CN100536365C - Transmission system and demodulating equipment using in same - Google Patents

Abstract

To execute a test for adjusting the direction of a receiving antenna even in a further slight reception electric field, and also, to allow a demodulator to grasp a state that it is in the middle of setting for the test. In the transmission system, an OFDM signal including a guide interval period is transmitted with a transmitter. The OFDM signal is received with the receiving antenna. Correlation calculation in the guide interval period of the OFDM signal is executed with the demodulator. The direction of the receiving antenna is adjusted by generating a signal for adjusting the direction of the receiving antenna on the basis of a correlation signal obtained as a result of the correlation calculation. The transmitter is equipped with amplitude converting means for making amplitude of a signal in the guide interval period larger than that of a signal in an effective symbol period. The demodulator is equipped with a detection means which detects the amplitude of the signal in the guide interval period of the received OFDM signal, and a notification means for notifying an operator of the detected results.

Description

Transmission system and be used for the demodulating equipment of this transmission system

Technical field

The present invention relates to adopt the transmission system of orthogonal frequency-division modulation system (Orthogonal FrequencyDivision Multiplexing: be designated hereinafter simply as the OFDM mode), the transmission system that relates in particular to the direction adjustment test (test) that is applicable to reception antenna with and the demodulating equipment that uses.

Background technology

Past, the method that adopts is: when the direction of the reception antenna of simulation FPU (Field Pickup Unit) being adjusted to incoming level and becoming maximum direction adjustment test optimum orientation, reception antenna (test), received signal from reception antenna output is input to spectrum analyzer, make on one side the direction of reception antenna the left and right sides is trickle up and down and move, measure on one side the level of the carrier wave that on spectrum analyzer, shows, and seek peak level and become maximum direction and regulate with kurtosis.

But in recent years, in the wireless device field, the OFDM mode was noticeable as the modulation system of anti-multichannel decay, was carrying out application study in a large number with fields such as the television broadcasting of future generation of the various countries headed by Europe and the Japan, FPU, WLAN.Wherein, about the exploitation trend and the mode of the terrestrial digital broadcasting of UHF frequency band, in 1998 the 52nd volumes of image information medium association magazine the 1st phase (non-patent literature 1), narrate in detail.

This OFMD mode is almost to carry out digital modulation by spaced apart hundreds of the carrier waves of certain frequency by certain symbol period in whole transmission band and to send.Therefore the waveform of ofdm signal becomes the waveform similar with random noise.Its frequency distribution is also such shown in pattern among Figure 18, becomes the shape of flatly expanding in whole transmission bandwidth, is the high mode of utilization ratio of transmission band.But, have the very difficult shortcoming of direction adjustment test (test) of reception antenna thus conversely.

As shown in figure 18, be the smooth distribution that almost equates in the OFDM mode with average power level.And in the transmission system of OFDM mode, for example the modulation system that each carrier wave is modulated adopts BPSK, if use the convolution code of encoding rate 1/2 to transmit, even then C/N also can receive for about odB.Received signal level and noise level are almost equal under this state.The power density of the signal in the transmission band that constitutes by the power sum of the power of received signal and noise, as shown in figure 19, with respect to the high approximately 3dB of level of the only noise in its outside.So,,, then can confirm the existence of transmission signals in any case if make reception antenna towards optimum orientation even adopt the method for spectrum analyzer.

But if the skew of the direction of reception antenna is very big, then the level of ofdm signal buries as shown in figure 20 fully in noise, sees and can not confirm whether it exists with observing.If can see the short range transmission that sends the place, then also can be with feeling to come travel direction adjustment test (test).But,, so, in fact can not carry out the direction adjustment test of reception antenna if transmission range exceedance kilometer is not measured the correct position relation that sends place and reception site if then do not use GPS to wait.

Eliminate these shortcomings; in the receiving system of OFDM mode; even the initial stage of the direction adjustment of the reception antenna below the about 0dB of C/N test; also can detect the level of received signal; because can adjust the direction of reception antenna; so; transmission comprise the protection interim in the transmission system of interior ofdm signal; to the ofdm signal that receives by reception antenna; in demodulating equipment, carry out the related operation of protection interim of ofdm signal; according to the coherent signal of the gained as a result of related operation, generate reception antenna direction adjustment signal, carry out the direction adjustment of reception antenna and test.This transmission system technology proposes in patent gazette 2003-115787 number (referring to patent documentation 1).

Figure 13 is the figure of the structure of expression transmission system in the past.Be input to information code in the emission pre processing circuit 13a of emitter 12 by to the conversion of error correcting code, to the preliminary treatment of the modulation of 64QAM etc., be transformed into the train of signal of the frequency band distributed image of each carrier signal of expression, in the IFFT of OFDM modulator (anti-Fourier transformation) circuit 13b, be transformed into the train of signal of express time waveform.

The OFDM mode is respectively by the mode of carrying out digital modulation and transmission during certain symbol hundreds of the carrier waves of arranging by certain band separation.In the modulation of ofdm signal, adopt the IFFT (anti-Fourier transformation) of M (for example M=2048) that count usually.

And, insert at interval among the circuit 13c in the protection of OFDM modulator, in order to reduce the influence of the intersymbol interference of transmitting the caused receiver side of delay ripple in the road, supplementary protection is at interval on the ofdm signal that is sent out.After having inserted this protection signal at interval and in emission post processing circuitry 13d, carrying out reprocessings such as quadrature modulation, D/A conversion, upconvert again, launch from transmitting antenna 11.

1 symbol of the ofdm signal that sends from emitting side shown in the pattern of Figure 14, has following component part: the ofdm signal that Ts signal (B+b) during the significant character, its M when modulating with IFFT circuit 13b are ordered constitutes; And the signal b of Tg ' during last Mg (for example Mg=128) point of 1 symbol when inserting at interval circuit 13c in protection and insert, duplicate the Mg point protection blank signal b ' on the protection interim Tg before the Ts during the significant character.And a and a ' are partly, c also is the same with c ' part.

The OFDM transmission signals that is launched is received by reception antenna 21, is sent to demodulating equipment 22 by cable.Be input to received signals in the demodulating equipment 22 are transformed into the complex vector located signal of numeral in down converter 23a, A/D translation circuit 23b after; be input in the path of main line system; and be input in the protection correlation computations circuit 24 in other path, there is following formation portion in above-mentioned main line system: implement the information code that is transmitted is carried out IFFT (Fourier transformation) the circuit 23c of the signal processing of demodulation, the demodulation decoding circuit 23e of transmission road response equalizing circuit 23d etc.

Figure 15 represents the circuit structure example of the protection correlation computations circuit 24 of Figure 13.The complex vector located signal Zin (m) that are input in the protection correlation computations circuit 24 are branched off into 2, and one of them is input in the delay circuit 31, as the following segment signal of Figure 16 (a), postpone to be equivalent to the number of samples M (for example M=2048) of Ts during the significant character.Here m is the sampling point numbering.In the A/D of Figure 13 translation circuit 23b, the used identical frequency clock of clock frequency is taken a sample among the IFFT13b of employing and emitter 12, so the number of sampling of Ts equals the M that counts of IFFI13b during the significant character.

Postponed the signal Zin (m-M) of Ts during this significant character and postpone before signal Zin (m) in complex multiplication operation circuit 32, carry out complex multiplication operation by each sampling point, calculate Zmul (m).

Zmul(m)＝Zin(m)×Zin(m-M)*……(1)

The waveform of this complex multiplication operation signal is shown in Figure 16 (b) with pattern.Here the value that same signal b and b ' are carried out the scope of multiplying becomes | b (m) | ²+ j0 becomes positive real number value shown in during Figure 16 41.And ofdm signal is the waveform near random noise, its amplitude | b (m) | ²Be worth also random vibration.Therefore, correctly say also random vibration of 41 I composition (real number composition) level during Figure 16.But,,, use straight line here with modal representation for fear of confusing mutually with The noise.

On the other hand, shown in during Figure 16 42, to mutually different complex vector located signals such as C * B carry out multiplying during the complex multiplication operation signal, become at random original state waveform (wherein, amplitude square waveform).The complex vector located signal Zmul (m) of output from the complex multiplication operation circuit 32 of Figure 15; be input to successively in the shift register in the related operation circuit 33; shown in following (2) formula; by each sampling point the Mg sampled signal in the shift register is carried out add operation, and export as protection coherent signal Cg.

Cg (m)=∑ Zmul (m-k) (in the formula, k=0～Mg-1) ... (2)

Figure 16 (c) should protect the waveform of coherent signal Cg with modal representation.On sampling point 43, the signal that carries out add operation is the Mg sampled signal of change at random, so the level ratio of cancelling each other is less, becomes random signal.To this, all become multiplying value between same signal b and the b ' in sampling point 44 added signal | b (m) | ²+ j0.Therefore, in the I composition, Mg real positive value can not cancelled each other, and all additions shown in the thick arrow of Figure 16 (c), become big real positive value signal.And, in the Q composition, answer the value of add operation all to become 0, so the add operation result also becomes 0.

As sampling point 45, if depart from sampling point 44 a little, then the number of the real positive value of add operation reduces, and the random signal number of correspondingly cancelling each other increases.Therefore, the level of I composition slowly reduces.And Q becomes score value slowly to increase on the contrary, becomes the signal of random vibration.

Therefore; protection coherent signal Cg from protection correlation computations circuit 24 output of Figure 13, Figure 15; as Figure 16 (c), the I composition becomes the general triangular waveform that has peak value on the boundary point during the symbol, and the Q composition becomes on boundary point on the contrary and is roughly 0 waveform.And above explanation is only set up under the situation that the Lo of receiving system frequency (local oscillation frequency) is introduced synchronously.As the initial stage of the direction adjustment of reception antenna test, not establish when synchronous, the complex vector located signal that is made of I composition and the Q composition of Figure 16 (c) becomes the signal of going up rotation in any direction.

Protection coherent signal Cg from the protection correlation computations circuit 24 of Figure 13 is exported is input to incoming level counting circuit 25 in order to calculate received signal level.

Figure 17 represents the example of internal circuit of the incoming level counting circuit 25 of Figure 13.Being input to protection coherent signal Cg in the incoming level counting circuit 25 is imported in the peak point testing circuit 51 here; to Ts ' during per 1 symbol, detect respectively as the peak point absolute value of the complex vector located signal of protection coherent signal Cg, in during this symbol.The peak signal of the peak that expression is detected and protection coherent signal Cg are imported into the peak dot value counting circuit 52 of I composition absolute value and the peak dot value counting circuit 53 of Q composition absolute value.

In each peak dot value counting circuit 52,53; calculate the absolute value of I composition of the protection coherent signal Cg of detected peak dot | the absolute value of max Ic| and Q composition | after the max Qc|, in peak dot value adder operation circuit 54, calculate their additive value | max Ic|+|max Qc|.This is the computing of approximation of absolute value of calculating the complex vector located signal of conduct of protection coherent signal Cg, preferably calculates absolute value accurately $\max \left|\mathrm{Cg}\right|=\sqrt{(\max \mathrm{Cg}\×\max \mathrm{Cg}*)}.$ In the formula, max Cg is the value (complex vector located signal) of the peak dot of protection coherent signal Cg.

But when the direction of reception antenna was faced optimum orientation, the level height of received signal can be ignored to noise, so, if obtain the signal that only constitutes, then can be the absolute value that is similar to by ofdm signal.Therefore, peak value max|Cg| can be approximated to be

max|Cg|＝∑|b(k)| ²＝Mg×{1/Mg×∑|b(k)| ²}

In the formula (k=1～Mg) ... (3).

If Mg becomes enough big value, then the formula in the bracket approaches to be input to the calculating formula of the average power of protecting the ofdm signal in the correlation computations circuit 24.Usually, the Mg value is about 128 samples or more big positive number, so, be σ if be imported into the average power of the ofdm signal in the protection correlation computations circuit 24 ², then peak value max|Cg| becomes the value of approaching Mg * σ ²Value, promptly almost with average power σ ²The value that is directly proportional.

On the other hand, when the direction of reception antenna during towards the opposite way round, can receive ofdm signal hardly, under extreme case, the signals that are input in the protection correlation computations circuit 24 almost become to having only noise.In the case, it doesn't matter between Zin of complex multiplication operation (m) and the Zin (m-M), so Zmul (m) becomes the power σ that effective value is input to the noise in the protection correlation computations circuit 24 no better than _n ²Random signal.Therefore, if calculate the Zmul (m) of Mg sampling amount, cancel each other between the then opposite polarity value, protection coherent signal Cg (m) becomes effective value and is substantially

About random signal.

And in reception antenna direction adjustment test midway, the ofdm signal of having sneaked into the noise of the level that can not ignore is input in the protection correlation computations circuit 24.In the case, the peak value max|Cg| that calculates becomes following signal: at the power σ of the ofdm signal composition that has and import ²The value Mg that is directly proportional * σ ²Signal on, add the noise contribution power σ that has and sneak into _n ²The effective value that is directly proportional

The signal of random signal.So the CN of received signal is than being σ/σ _nSituation under, can obtain the peak value of following ofdm signal.

For example, length M g at interval is under the situation of 128 samples in protection, even the CN of received signal is than being 0dB=20.log (σ/σ _n), also can obtain the peak value of the ofdm signal number of following good SN ratio.

$20\·\log [{(\mathrm{\σ}/{\mathrm{\σ}}_n)}^2\×\sqrt{\mathrm{Mg}}]=2\×20\·\log (\mathrm{\σ}/{\mathrm{\σ}}_n)+20\·\log \left(\sqrt{\mathrm{Mg}}\right)$

$=21\mathrm{dB}$

The averaging circuit 55 of Figure 17 in order further to improve the SN ratio of gained peak value, calculates from the mean value of peak point adder operation circuit 54 by the peak value max|Cg| of each symbol output.Specifically, can use the average circuit of add operation of the peak value max|Cg| that calculates a fixed number, perhaps the LPF (low pass filter) that the peak value max|Cg| frequency band by each symbol input is limited.For example, the add operation of peak value max|Cg| that only calculates 64 symbols is average, can make SN than further being improved as 10Log (64)=18dB.This equalization computing can also obtain because above-mentioned value | b (m) | ²The influence of random vibration and effect that the random fluctuation of the peak value that produces can reduce.

But, by the peak value max|Cg| that above computing calculates, be and the power σ that is input to the ofdm signal composition that is comprised in the signal Zin that protects in the correlation computations circuit 24 ²The value that is directly proportional, not necessarily the power level Ps with the signal of receiving is directly proportional.Usually, in receiving system, the received signal level that great variety takes place is transformed into the almost signal of certain level in agc circuit under condition of acceptance, carries out various signal processing then.The power that is input to the signal Zin in the protection correlation computations circuit 24 also remains roughly certain.

So, be controlled so as to: when the ofdm signal level that receives is high, be input to the power level σ of the ofdm signal in the protection correlation computations circuit 24 ²Roughly keep certain.The size of the peak value max|Cg| that is calculated by incoming level counting circuit 25 also almost is certain.Therefore, usually, can not from the peak value max|Cg| that calculates, detect the accurate power level Ps of the ofdm signal that has received.But in fact the signal by agc circuit control is by the ofdm signal of the power level Ps that is received and the power level Ptot=Ps+Pn of the signal integral body that noise constituted of the power level Pn that sneaks into.Therefore, be input to the power σ of the ofdm signal that is comprised among the signal Zin that protects in the correlation computations circuit 24 ², accurately, become

σ ²＝Ps/Ptot＝(Ps/Pn)×1/(Ps/Pn+1)

On the other hand, in the direction adjustment test of reception antenna, the level detection of received signal the most important thing is, the direction skew of reception antenna, the power level Ps of received ofdm signal reduces, when the power level of noise Pn that produces in the preposition AMP of receiving system (amplifier) increases.Like this, compare with the power level Ps of ofdm signal, when power level of noise Pn is enough big,

Approximate expression set up, the power level that is input to the ofdm signal in the protection correlation computations circuit 24 can be approximately

In the formula, the power level of noise Pn that produces in the preamplifier is the certain value by the circuit performance decision of receiving system, so the result is input to the power σ of the ofdm signal in the protection correlation computations circuit 24 ²Power level Ps with the ofdm signal that receives is directly proportional haply.

So the peak value max|Cg| that is calculated by incoming level counting circuit 25 is directly proportional with the power level Ps of the ofdm signal that receives haply, this level can detect.And as described above, peak value max|Cg| is the value of the high SN ratio of about 21dB+18dB=39dB.Therefore, the direction of reception antenna is towards the direction of mistake, and even the power level of the ofdm signal of reception also lower than noise level, also can not only detect the existence of this signal as shown in Figure 20, and can detect its level variation.

Therefore, the peak value max|Cg| of output as above-mentioned calculating and equalization from incoming level counting circuit 25 is as the incoming level signal.The incoming level signal of output is imported in the direction adjustment signal generating circuit 26 from incoming level counting circuit 25, be transformed into the signal that the adjustment with reception antenna 21 adapts, utilize the measuring instrument that shows incoming level to measure incoming level on one side, carry out on one side under the situation of direction adjustment test of reception antenna, will adjust signal as direction and export the signal of controlling with the measuring instrument show values such as length of the corresponding brightness of incoming level, color or display bar.

Like this, if utilize the demodulating equipment of the OFDM mode of Figure 13, then the CN of the ofdm signal of Jie Shouing ratio becomes below the 0dB, adopt in the method for spectrum analyzer, in the existence of ofdm signal initial stage of the direction adjustment test of non-detectable reception antenna all, also be the existence that not only can detect ofdm signal, and can recently measure the power level and the variable quantity thereof of the ofdm signal that has received with high SN.Therefore, on one side can change the direction of reception antenna, Yi Bian seek the direction of the ofdm signal level maximum that is received.Utilize the incoming level signal that has calculated, can carry out the direction adjustment test of reception antenna at an easy rate.

＜patent documentation 1〉spy opens the 2003-115787 communique;

＜non-patent literature 1〉image information medium association magazine,, the 52nd volume in 1998, o. 11th.

In the initial stage that the direction adjustment of reception antenna is tested, the deviation in driction optimum orientation of reception antenna, so received signal level is low, if the direction of reception antenna departs from optimum orientation significantly, then received signal level is very low.Therefore, wish that reception antenna also responds in very faint reception electric field.And, whether be in direction adjustment test with the situation in setting by utilizing demodulating equipment can grasp reception antenna, utilize demodulating equipment can check out after test (test) in emitter finishes whether forgotten test return.

Summary of the invention

The object of the present invention is to provide a kind of direction adjustment that in faint reception electric field, also can carry out reception antenna to test and utilize demodulating equipment to grasp whether be in the test transmission system of the situation in setting and the demodulating equipment of use thereof.

In order to achieve the above object, transmission system of the present invention, utilize emitter to launch and comprise the ofdm signal of protecting interim, utilize reception antenna to receive above-mentioned ofdm signal, utilize demodulating equipment to carry out the related operation of protection interim of above-mentioned ofdm signal, the coherent signal of obtaining according to the result of this related operation, generate the direction adjustment signal of above-mentioned reception antenna, and carry out the direction adjustment of above-mentioned reception antenna, it is characterized in that: have the amplitude converting means in above-mentioned emitter, this amplitude converting means is transformed into the amplitude of the signal of protecting interim at least in the above-mentioned ofdm signal bigger than the amplitude of the signal during the significant character; In above-mentioned demodulating equipment, have: testing agency, detect the amplitude of the signal of protecting interim at least in the above-mentioned ofdm signal; And notice mechanism, notice is by the detected result of this testing agency.

And transmission system of the present invention is characterized in that: above-mentioned notice mechanism shows that at least the expression reception antenna is in the mechanism of direction adjustment test with the literal of the situation in setting.

Moreover transmission system of the present invention is characterized in that: above-mentioned notice mechanism is in direction adjustment test with in setting the time and in this settings during in addition state at reception antenna, shows with different colours.

And, demodulating equipment of the present invention, be used for following transmission system: utilize emitter to launch and comprise the ofdm signal of protecting interim, utilize reception antenna to receive above-mentioned ofdm signal, utilize demodulating equipment to carry out the related operation of protection interim of above-mentioned ofdm signal, the coherent signal of obtaining according to the result of this related operation, generate the direction adjustment signal of above-mentioned reception antenna, and carry out the direction adjustment of above-mentioned reception antenna, have the amplitude converting means in above-mentioned emitter, this amplitude converting means is transformed into the amplitude of the signal of protecting interim at least in the above-mentioned ofdm signal bigger than the amplitude of the signal during the significant character; This demodulating equipment is characterised in that, has: testing agency, detect the amplitude of the signal of protecting interim at least in the paid-in above-mentioned ofdm signal; And notice mechanism, be used for notice by the detected result of this testing agency.

Demodulating equipment of the present invention is characterized in that: above-mentioned notice mechanism shows that at least the expression reception antenna is in the mechanism of direction adjustment test with the literal of the situation in setting.

The invention effect

According to the present invention, can obtain such transmission system and used demodulating equipment thereof, even they also can carry out the direction adjustment test of reception antenna in faint reception electric field, and, utilize demodulating equipment can grasp in the setting that whether is in above-mentioned test.

Description of drawings

Fig. 1 represents the structure of the execution mode in the transmission system of the present invention.

The major part OFDM modulator of Fig. 2 presentation graphs 1 and the structure of amplitude conversion part.

The internal circuit of the Modulation and Amplitude Modulation portion in Fig. 3 presentation graphs 2.

Fig. 4 illustrates an example of ofdm signal of the present invention.

Fig. 5 illustrates another example of ofdm signal of the present invention.

Analog result during the ofdm signal of Fig. 6 presentation graphs 4.

The structure of the detector of the demodulating equipment of Fig. 7 presentation graphs 1.

The operate condition of each several part when Fig. 8 represents received signal with Fig. 4 (d-1) same waveform as, Fig. 7.

The operate condition of each several part when Fig. 9 represents received signal with Fig. 5 (d-2) same waveform as, Fig. 7.

Operate condition during the identical received signal of the amplitude of the signal during the signal that Figure 10 represents to protect interim and the significant character, Fig. 7 each several part.

The concrete example of the notice portion of Figure 11 presentation graphs 1.

The application examples of the demodulating equipment of Figure 12 presentation graphs 1.

Figure 13 represents the structure of transmission system in the past.

Figure 14 represents the explanation of the formation of the ofdm signal that is transmitted.

Figure 15 represents the example of circuit structure of the protection correlation computations circuit of Figure 13.

Figure 16 illustrates the computing of implementing with the protection correlation computations circuit of Figure 13.

Figure 17 represents the example of internal circuit of the incoming level counting circuit of Figure 13.

Figure 18 illustrates the frequency distribution of ofdm signal.

Figure 19 illustrates the frequency distribution when receiving ofdm signal.

Figure 20 illustrates the frequency distribution when the direction adjustment of reception antenna is tested.

Embodiment

Below utilize accompanying drawing, detailed description relates to embodiments of the present invention.

Fig. 1 represents the structure of the execution mode in the transmission system of the present invention.The major part OFDM modulator of the transmitting device of Fig. 2 presentation graphs 1 and the structure of amplitude conversion part.The internal circuit of the Modulation and Amplitude Modulation portion in Fig. 3 presentation graphs 2.Fig. 4 illustrates an example of ofdm signal of the present invention.Fig. 5 illustrates another example of ofdm signal of the present invention.

In Fig. 1, marked identical symbol in the part identical with the structure in past of Figure 13.Be input to the interior information code of emission pre processing circuit 13a of emitter 12,, be transformed into the train of signal of the frequency band distributed image of each carrier signal of expression, be input in the OFDM modulator 61 by to the conversion of error correcting code, to the preliminary treatment such as modulation of 64QAM.

Be input to the train of signal of the frequency band distributed image in the OFDM modulator 61; utilize built-in IFFT circuit and be transformed into the train of signal of express time waveform; and; insert circuit at interval by built-in protection; export as the certain train of signal of amplitude, 1 symbol of this train of signal comprises: the signal (B+b) of Ts and the signal b of Tg ' during last among the Ts during the significant character duplicated the protection blank signal b ' among the protection interim Tg before the Ts during the significant character during the significant character that is made of the OFMD signal shown in Fig. 4 (a), Fig. 5 (a).And, shown in Fig. 4 (b), Fig. 5 (b), from OFDM modulator 61, to the timing of expression symbol period each constantly tn0 (n=0,1 ...), output becomes the symbol timing signal of level H.

From the certain ofdm signal of amplitude of OFDM modulator 61 output, be imported into Fig. 1, amplitude conversion part 62 shown in Figure 2, and, also be input to Fig. 1, amplitude conversion part 62 shown in Figure 2 from the symbol timing signal of OFDM modulator 61 outputs.

Fig. 1, amplitude conversion part 62 shown in Figure 2 are as shown in Figure 3, constitute by multiplier 62-1 and control part 62-2, be imported in the multiplier 62-1 from the certain ofdm signal of amplitude of OFDM modulator 61 outputs, the symbol timing signal of exporting from OFDM modulator 61 is imported in the control part 62-2.

Control part 62-2 generates the also amplitude control signal shown in the output map 4 (c-1), the perhaps amplitude control signal shown in Fig. 5 (c-2).Amplitude control signal shown in Fig. 4 (c-1) as the protection interim Tg Tn0～tn1 (n=0,1 ...) during be decided to be level H; Being decided to be level L during the tn1～t (n+1) 0 as Ts during the significant character.Amplitude control signal shown in Fig. 5 (c-2) is following signal: promptly be decided to be level H during its Tn0～tn1 as protection interim Tg; During significant character among the Ts, with protection interim Tg irrelevant during Ts ' be decided to be level L; During significant character among the Ts, the making of protection interim Tg signal used during Tg ' be decided to be level H.

Multiplier 62-1 utilizes the amplitude control signal shown in the amplitude control signal shown in Fig. 4 (c-1) or Fig. 5 (c-2) to adjust the amplitude of the certain ofdm signal of amplitude.

At amplitude control signal is under the situation of Fig. 4 (c-1); the ofdm signal that multiplier 62-1 is certain to amplitude; shown in Fig. 4 (d-1); amplitude as the signal b ' of the protection interim Tg of relevant treatment object increased promptly strengthen; correspondingly the amplitude of the signal among the Ts during the significant character (B+b) is decayed; like this, it is identical to set total transmitting power for.

Specifically, multiplier 62-1 is made as A doubly with the amplitude of ofdm signal when the level H of amplitude control signal; When the level L of amplitude control signal, the amplitude of ofdm signal is made as B doubly, and establishes

A(tno～tn1)+B(tn1～t(n+1)0)＝1

On the other hand; amplitude control signal is under the situation of Fig. 5 (c-2); the ofdm signal that multiplier 62-1 is certain to amplitude; shown in Fig. 5 (d-2); make as the signal of the protection interim Tg among the Ts during the amplitude of the signal b ' of the protection interim Tg of relevant treatment object and the significant character make employed during the amplitude of signal b of Tg ' increase promptly and strengthen; correspondingly make during the significant character among the Ts with protection interim Tg irrelevant during the amplitude fading of signal B of Ts ', thereby it is identical to set total transmitting power for.

Specifically, multiplier 62-1 is made as A doubly with the ofdm signal amplitude when the level H of amplitude control signal; When the level L of amplitude control signal, the amplitude of ofdm signal is made as C doubly, and establishes

A(tno～tn1)+C(tn1～tn2)+A(tn2～t(n+1)0)＝1

At the ofdm signal of shown in Fig. 4 (d-1) or Fig. 5 (d-2), setting in the amplitude conversion part 62, in the emission post processing circuitry 13d of Fig. 1, carry out reprocessings such as orthogonal transform, D/A conversion, upconvert after, launch from transmitting antenna 11.

Integral body among the multiplier 62-1 is 1 ratio distribution, is implemented by amplitude conversion part 62 in the present embodiment, but also can carry out in emission post processing circuitry 13d thereafter.

And, also can set like this, be the setting state of no amplitude control below 1 promptly, the summation in the time of will carrying out above-mentioned amplitude control is set at just in time 1.Moreover, also can set like this, promptly the state of no amplitude control is decided to be 1; Summation when carrying out the control of above-mentioned amplitude is set at 1+ α (wherein, α＞0).

Ofdm signal so far is represented the protection blank signal is arranged in 1 example on the part (on the time shaft during the significant character one-sided) during the symbol.But also can be the ofdm signal that the protection blank signal is arranged in both sides on the time shaft of significant character.

Analog result during the ofdm signal of Fig. 6 presentation graphs 4.This simulation is; in Fig. 4; is the fixed amplitude of Ts signal (B+b) during the significant character of ofdm signal 1; make amplitude G from G=1 to G=6.0, increase G=0.5 as the signal b ' of the protection interim Tg of relevant treatment object at every turn; in these amplitudes G, the electric field strength when changing C/N (signal/noise) is shown in this performance plot.Along with the increase of amplitude G, the variation of the electric field strength characteristic when changing C/N (signal/noise) increases.So,, in very faint reception electric field, also can carry out the direction adjustment test of reception antenna according to present embodiment.

For this ofdm signal; unlike Fig. 4 (d-1) but as Fig. 5 (d-2); if will as the amplitude of the signal b ' of the protection interim Tg of relevant treatment object and during significant character among the Ts in the making of the signal of protection interim Tg employed during the amplitude of signal b of Tg ' increase; so; along with the increase of amplitude G, the variation of the electric field strength characteristic when having changed C/N (signal/noise) further increases.So,,, also can carry out the direction adjustment test of reception antenna even in very faint reception electric field according to present embodiment.

The signal amplitude of protection in interim being increased promptly strengthen is to have a mind to the setting carried out, so that can carry out the direction adjustment test of reception antenna in demodulating equipment.After the direction of reception antenna is adjusted EOT, must test return, so that in emitter, it is identical to make signal amplitude in protection interim turn back to signal amplitude interior during the significant character with usually the time.

But; just in case in emitter; under the state of having forgotten test return, enter into formal utilization, then in demodulating equipment, protect the increase of the signal amplitude in interim to become noise, so; the tolerance limit (margin) of expression S/N ratio reduces; and, under the situation of the signal amplitude decay during significant character in the Ts, the utilization state that tolerance limit further reduces when becoming formal the utilization; in demodulating equipment, the picture signal that is transmitted is difficult to obtain stable picture quality.

Therefore, in the present embodiment, utilize demodulating equipment can grasp situation in the setting that reception antenna is in direction adjustment test usefulness.

That is to say, in the present embodiment of Fig. 1, in demodulating equipment 22, added test section 70 and notice portion 80.Test section 70 is connected with the output of down converter 23a, and being used to detect received signal is Fig. 4 (d-1), or Fig. 5 (d-2).Notice portion 80 is connected with the output of test section 70, the accepting state of notice received signal.

Test section 70 now is described.At first, utilize average power detector symbol waveform to received signal, detecting average power identical or less each specified time limit interim with protection.Whether according to the average power result's of this each specified time limit size variation, judging at least and detecting is that protection interim is increased the received signal that has promptly strengthened.

If no matter common waveform is to protect during interim or the significant character then, amplitude level all is certain, and the average power that is detected all is roughly the same same equivalence at every turn.On the other hand, protection is under the situation of the waveform that has been enhanced interim, the average power height of protection interim, and the average power content during the significant character is low.

Detect average power during regularly corresponding to possibility is less during with the interruption of the symbol of received signal.During average power is calculated across during the significant character and protection interim.Therefore, preferably the computing interval unit of average power level is set at half of protection interim.

And, owing to suppress noise, by the amplitude level that the computing interval unit of average power level obtains, preferably be set at according to the mean value that is the amplitude level obtained of the computing interval unit behind the regulation unit value in time.

And; the amplitude level of obtaining according to the computing interval unit of average power level compares by the amplitude level of obtaining with the computing interval unit of going up adjacency by the time, can compare the amplitude level of protection interim and the amplitude level during the significant character.

The structure of the detector 70 of the demodulating equipment 22 in Fig. 7 presentation graphs 1.Fig. 8 shows: with the received signal of Fig. 4 (d-1) same waveform as; increase i.e. enhancing at signal amplitude to protection interim Tg; correspondingly make the signal amplitude decay of Ts during the significant character; like this; total transmission power setting be identical transmit and the situation of the received signal of same waveform as under, the operating state of each one of Fig. 7.

In Fig. 7, the 71st, average power detector, 72-1,72-2,72-3,72-4 are memories, the 73rd, controller, the 74th, adder, the 75th, subtracter, the 76th, comparator, the 77th, timer.

In average power detector 71, utilize controller 73 according to as protection half each computing interval unit of interim, the average power of output received signal.

By controller 73 average power that is detected is input among the memory 72-1, and it is transferred among memory 72-2,72-3, the 72-4 successively by controller 73.The output of the output of average power detector 71 and memory 72-4 is imported in the adder 74, by the additional calculation result of adder 74 outputs 1/2.

Then, from the output of memory 72-2, deduct the output of adder 74, and export the result by subtracter 75.Then, with comparator 76 output of subtracter 75 and Th (threshold value)=1.8 are compared.Its result, comparator 76 is only exported high level to the signal of protection interim Tg.

Output by timer 77 maintenance high level.Each fixed cycle has one to protect interim, so, export high level from comparator 76 when protecting interim at every turn.Therefore, timer 77 keeps high level.Like this, can detect protection interim that increase has promptly strengthened.

Fig. 9 shows: and the received signal of Fig. 5 (d-2) same waveform as; to the signal amplitude of protection interim Tg and during significant character among the Ts in the making of signal of protection interim Tg employed during the signal amplitude of Tg ' increase promptly and strengthen; correspondingly among the Ts during the significant character with protection interim irrelevant during the amplitude of Ts ' signal decay; like this; total transmission power setting be identical transmit and the situation of the received signal of same waveform as under, the operate condition of Fig. 7 each several part.

Under the situation of this received signal; Fig. 7 carries out the action identical with above-mentioned explanation; in comparator 76; by the output of subtracter 75 and Th shown in Figure 8 (threshold value)=0.9 are compared; during significant character among the Ts, in the making to the signal of protection interim Tg employed during the signal of Tg ' also export high level.Promptly export from comparator 76 across the high level on Tg '+protection interim Tg during employed in protection interim signal is made.Like this, can detect in the making of signal of protection interim of increase when promptly strengthening employed during+protection interim.

Figure 10 shows: under the situation of the identical received signal of the amplitude of the signal of Ts during signal and the significant character of protection interim Tg; be to test return after the direction of reception antenna is adjusted EOT; return amplitude when being set at original common mode transmit and the situation of the received signal of same waveform as under, the operate condition of the each several part of Fig. 7.

Under the situation of this received signal, also carry out the action identical among Fig. 7,,, therefore, from comparator 76, do not export high level so subtracter 75 is output as 0 because of amplitude is identical with above-mentioned explanation.Like this, can detect the protection interim that non-increase is non-enhancing.

The notice portion 80 of following key diagram 1.Notice portion 80 increases under the situation about promptly strengthening in the interim of protecting at least of received signal according to the detection of test section 70, notifies at least.Notice portion 80 both can be that enterprising the working of display known demonstration, also can be measuring instrument, loud speaker, indicator light or buzzer.

The concrete example of the notice portion 80 in Figure 11 presentation graphs 1.(a) during the common mode of expression, (b) demonstration of the direction adjustment test of expression reception antenna when setting.On display 81, demonstrate: postpone characteristic pattern (profile) (reflected wave have stateless) 82, tolerance limit 85, electric field 86, the error rate 87 of reflected wave 83, layout Figure 84, expression S/N ratio are arranged, in addition, situation at test section 70 output high level is responded, represent that reception antenna is in the test literal demonstration 88 of direction adjustment test with " TEST " of the situation in setting.

And, the situation at test section 70 output high level is responded, in case of necessity, display 81 is for example shown when mode usually with blue, when the setting of the direction adjustment test usefulness of reception antenna, for example use red display instead.

Like this, can grasp reception antenna with demodulating equipment and be in direction adjustment test with the situation in setting.So, can be with the contact of phone and receiving system side when beginning is formally got in touch with from the emitter side, by the display 81 of watching Figure 11, come as the direction adjustment test of reception antenna with under the situation about showing in the setting, this content can be passed to emitter.

Therefore, notice that emitter forgets the situation of test return,, can form the big utilization state of tolerance limit of representing the S/N ratio when formal by testing return, so, the picture quality that the picture signal that can obtain to be transmitted with demodulating equipment is stable.

The application examples of the demodulating equipment 22 in Figure 12 presentation graphs 1.In Figure 12, for the position mark identical symbol identical with Fig. 1.Figure 12 is illustrated in and also has switch 90, measuring instrument 91, switch 92, loud speaker 93 in the demodulating equipment 22, also has a status display system 94.

Import the output of electric field level, associated level and test section 70 on the switch 90.Switch 90 the electric field level that obtains with incoming level counting circuit 25 of Fig. 1, be input in the measuring instrument 91 with the associated level of protecting interlock circuit 24 to obtain, carries out the measuring instrument demonstration when common mode.Switch 90 switches when the setting of the direction adjustment test usefulness of reception antenna, the output of test section 70 is input to carries out the measuring instrument demonstration in the measuring instrument 91.

The input electric field closes liaison, relevant output of closing liaison and test section 70 on switch 92.Switch 92 is when common mode; the electric field pass liaison of the electric field level that obtains by the incoming level counting circuit 25 of Fig. 1 conversion in no illustrated circuit and the relevant pass liaison of the associated level conversion in no illustrated circuit that obtains by protection interlock circuit 24; be input in the loud speaker 93, and sound.Switch 92 switches and the output of test section 70 is input in the loud speaker 93 sends forte when the setting of the direction adjustment of reception antenna test usefulness.

And; on status display system 94; the electric field level that input is obtained by the incoming level counting circuit 25 of Fig. 1, by the protection associated level that obtains of interlock circuit 24 and the output of test section 70, on the display screen of built-in display monitor central monitoring system 95, for example carry out identical with Figure 11 or similar demonstration.

Like this, also can grasp situation in the setting that reception antennas are in direction adjustment test in the demodulating equipment by measuring instrument 91 or loud speaker 93.

Can obtain following transmission system and used demodulating equipment thereof according to present embodiment, it also can carry out the direction adjustment test of reception antenna in fainter reception electric field, and can grasp the situation of testing with in setting that is in by enough demodulating equipments.

Claims (5)

1, a kind of transmission system, utilize emitter to launch and comprise the ofdm signal of protecting interim, utilize reception antenna to receive above-mentioned ofdm signal, utilize demodulating equipment to carry out the related operation of protection interim of above-mentioned ofdm signal, the coherent signal of obtaining according to the result of this related operation, generate the direction adjustment signal of above-mentioned reception antenna, and carry out the direction adjustment of above-mentioned reception antenna, it is characterized in that: have the amplitude converting means in above-mentioned emitter, this amplitude converting means is transformed into the amplitude of the signal of protecting interim at least in the above-mentioned ofdm signal bigger than the amplitude of the signal during the significant character; In above-mentioned demodulating equipment, have: testing agency, detect the amplitude of the signal of protecting interim at least in the above-mentioned ofdm signal; And notice mechanism, notice is by the detected result of this testing agency.

2, transmission system as claimed in claim 1 is characterized in that: above-mentioned notice mechanism shows that at least the expression reception antenna is in the mechanism of direction adjustment test with the literal of the situation in setting.

3, transmission system as claimed in claim 1 is characterized in that, above-mentioned notice mechanism is following mechanism: be in direction adjustment test with in setting the time and in this settings during in addition state at reception antenna, show with different colours.

4, a kind of demodulating equipment, be used for following transmission system: utilize emitter to launch and comprise the ofdm signal of protecting interim, utilize reception antenna to receive above-mentioned ofdm signal, utilize demodulating equipment to carry out the related operation of protection interim of above-mentioned ofdm signal, the coherent signal of obtaining according to the result of this related operation, generate the direction adjustment signal of above-mentioned reception antenna, and carry out the direction adjustment of above-mentioned reception antenna, have the amplitude converting means in above-mentioned emitter, this amplitude converting means is transformed into the amplitude of the signal of protecting interim at least in the above-mentioned ofdm signal bigger than the amplitude of the signal during the significant character;

This demodulating equipment is characterised in that, has: testing agency, detect the amplitude of the signal of protecting interim at least in the paid-in above-mentioned ofdm signal; And notice mechanism, be used for notice by the detected result of this testing agency.

5, demodulating equipment as claimed in claim 4 is characterized in that: above-mentioned notice mechanism shows that at least the expression reception antenna is in the mechanism of direction adjustment test with the literal of the situation in setting.

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