KR100346153B1 - Apparatus for transmitting intermediate frequency in a mobile communication cell site of code division multi access - Google Patents

Abstract

In the mobile communication base station apparatus of the code division multiple access method according to the present invention, the intermediate frequency transmitter receives a baseband I / Q signal converted into a spread spectrum signal from a modulator module and converts it into an analog signal and converts it into an analog signal. By converting the converted baseband signal into a 70MHz IF signal at a time by the provided 70MHz local frequency, and transmitting the converted 70MHz IF signal to the RF processor, the I / Q modulation function can be stably performed even at a lower frequency. In addition, since the band of the IF signal is used at 70 MHz, the baseband signal of a wider band can be accommodated than the conventional mobile communication system. In other words, by converting the baseband signal into an IF signal of 70MHz at once, the number of parts and the distortion of the signal are reduced, so that the IF transmitter can be easily implemented and operated stably.

Description

Apparatus for transmitting intermediate frequency in a mobile communication cell site of code division multi access}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate frequency transmitting apparatus in a mobile communication base station apparatus of Code Division Multi Access (CDMA) method, and in particular, to a spread spectrum signal in a wideband CDMA mobile communication base station apparatus. Intermediate frequency in the mobile communication base station of the code division multiple access method of converting the baseband signal to I / Q (Inphase / Quadrature) modulation and up-converting the modulated I / Q signal to an intermediate frequency at one time and transmitting it to a high frequency signal (RF) processor It relates to a transmitter.

A general CDMA mobile communication base station is composed of a switching system and cell equipment. This includes many of the unit functional units that make up the system, and these units are implemented with various types of equipment.

The core of such a mobile communication base station apparatus is a digital shelf carrying a channel card, a sector interface card, an analog common card, and an end card. The transceiver self converts an intermediate frequency signal (hereinafter referred to as IF) output from the digital self into UHF and down-converts the received UHF into IF.

In addition, the transceiver itself includes a sector access card for combining the baseband forward signal received from the channel card and converting it up to the IF signal. Such a sector access card receives a combined baseband transmission signal from an analog common card, combines and amplifies them. The combined signal is passed through a low pass filter (LPF) and combined with an IF signal, i.e., 0 ° and 90 ° delayed signals at 4.95 MHz, into the RF rack as an IF signal of 4.95 MHz through a band pass filter (BPF). Send. Therefore, the RF rack is to convert the 4.95Mhz IF signal received for signal transmission through the antenna to UHF signal.

Hereinafter, an IF transmitter in a general CDMA mobile communication base station apparatus will be described with reference to the accompanying drawings.

1 is a block diagram of an IF transmitter in a general CDMA mobile communication base station apparatus. Referring to FIG. 1, a baseband signal (I / Q) is 16 bits each from a channel card. A digital combiner 10 and a digital combiner 10 which receive a digital signal of 2-bit parallel x 8-bit serial form, digitally combine the signal, convert it into an I / Q signal of 16-bit parallel data, and output each of them. 16-bit parallel data I / Q signals are respectively output from the D / A converters 11 and 11a and the D / A converters 11 and 11a, respectively. Low pass filters 12 and 12a are respectively configured to low-pass filter unnecessary signals other than the baseband in the converted signal. Here, the low pass filters 12 and 12a are LC coupled low pass filters.

In addition, the amplifier 13, 13a for amplifying the I / Q signal filtered by the low pass filter (12, 12a) by a constant level to adjust the amplification gain value so that the peak to peak value of the I / Q signal is the same ), Phase equalizers 14 and 14a for non-linearizing the phase characteristics of the I / Q signals output from the amplifiers 13 and 13a, and non-linearized I / Q signals from the phase equalizers 14 and 14a. Low pass filters 15 and 15a perform filtering to remove band limitation and noise, and mix 0 ° and 90 ° delay signals with a local frequency of 4.95 MHz to the I / Q signals in the low-pass I / Q signals. The frequency mixers 16 and 16a and the adder 17 which adds the I / Q output signals of the frequency mixers 16 and 16a and modulates them into IF signals are provided.

In addition, a band pass filter 18 for band-filtering the IF signal modulated by the adder 17, a buffer 19 for buffering the IF signal through the band pass filter 18, and IF switching through the buffer 19 It consists of an analog switch 20 for switching in accordance with the control signal and transmitting the IF signal to the RF rack. Here, the band pass filter 18 has an intermediate frequency of 4.95 MHz and a bandwidth of 1.26 MHz.

The operation of the IF transmitter in the general CDMA mobile communication base station apparatus having such a configuration will be described.

First, the digital combiner 10 receives baseband signals as 16-bit digital signals from 10 channel cards, and digitally combines them, and then converts the combined baseband signals into 16-bit parallel data and converts them to D / A. Output to converters 11 and 11a, respectively. Here, the 16-bit digital signal received from the channel card is a 2-bit parallel x 8-bit serial signal, and the converted 16-bit digital signal input to the D / A converters 11 and 11a is 16-bit parallel. It is a digital signal.

Each 16-bit parallel data of the I / Q signal output from the digital combiner 10 is converted into an analog signal having 19.6608 MHz in the D / A converters 11 and 11a, respectively. 12a).

The low pass filters 12 and 12a attenuate unnecessary signals other than the baseband of the 19.660 8 MHz analog signals converted and output from the D / A converters 11 and 11a, and peak to peak of the I / Q signals. The amplification gains of the amplifiers 13 and 13a are adjusted so that the peaks are equal.

Then, the amplified gain-adjusted I / Q signal is converted into an artificially non-linearized signal in the phase equalizers 14 and 14a, and the converted non-linearized I / Q signal is third order for band limitation and noise cancellation. The Chebyshev filter, that is, the low pass filters 15 and 15a, is output to the multipliers 16 and 16a.

In this way, the I / Q signals output through the low pass filters 15 and 15a are multiplied by the 0 ° and 90 ° delayed signals of the local frequency of 4.95 MHz in the multipliers 16 and 16a, respectively, and then added through the adder 17. It is modulated with an IF signal. The modulated IF signal is filtered by a band pass filter 18 having an intermediate frequency of 4.95 MHz and a bandwidth of 1.26 MHz, and then an IF signal of 4.95 MHz is transmitted to the RF rack through the buffer 19 and the switch 20.

Such an IF transmitter for a general CDMA mobile communication base station apparatus has a problem in that I / Q modulation cannot be stably performed at low frequencies because the baseband signal is first upconverted only to 4.95 MHz.

In addition, since the IF signal is low at 4.95 MHz, the baseband of a wide band cannot be accommodated, and there is a problem in that the RF unit needs to be changed when the IF signal band becomes large.

Accordingly, an object of the present invention is to solve the above-mentioned problems according to the prior art, and an object of the present invention is to receive a baseband I / Q signal converted into a spread spectrum signal from a modulator module digitally and convert it into an analog signal. By converting the baseband signal to the intermediate frequency of 70MHz at once by the provided local frequency 70Mhz, it is possible to perform the I / Q modulation function at a lower frequency stably and to accept the wideband baseband signal. The present invention provides an intermediate frequency transmitter in a mobile communication base station apparatus having a code division multiple access method.

In the mobile communication base station apparatus of the code division multiple access method according to the present invention for achieving the above object, a feature of the intermediate frequency transmission apparatus, in the CDMS mobile communication base station apparatus having a baseband modulation module and RF processing unit, First and second D / A converters for converting a digital signal of an I / Q component modulated into a spread spectrum signal from the baseband modulation module to an analog signal having an arbitrary baseband; First and second amplifiers for amplifying each baseband signal of the I / Q converted to an analog signal by a predetermined level, respectively; a baseband of the I / Q component amplified by a predetermined level in the first and second amplifiers; First and second filtering units for removing spurious signal components other than the signals, respectively; and detecting a maximum value of the baseband I / Q component signals output from the first and second filtering units, respectively, to detect the spurious signal components. According to the I / Q channel A peak detection unit configured to generate an I / Q signal from which signal components other than a band are removed by the first and second filtering units and up-convert to an arbitrary IF signal by an arbitrary local frequency provided, and then I signal A modulator for outputting a sum of components and a Q signal component; a PLL providing the local frequency for I / Q modulation and IF upconversion in the modulator; and a digital for adjusting a power level of an IF transmission signal; A third D / A converter converting 8-bit data into an analog signal; and using the difference between the gain adjustment signal level output from the third D / A converter and the offset voltage provided, the power of the IF output signal is obtained. A gain control unit for amplifying or attenuating a predetermined level; removing an out-of-band signal from a signal output after being amplified or attenuated by the gain control unit, amplifying a predetermined level to meet the IF transmission level, and then And a transmitter for transmitting the amplified IF signal to the RF processor.

1 is a block diagram of an intermediate frequency transmitter in a mobile communication base station apparatus according to the prior art;

2 is a block diagram of an intermediate frequency transmission apparatus in a mobile communication base station apparatus of a code division multiple access method according to the present invention;

3 is a diagram illustrating a detailed circuit configuration of the peak detector shown in FIG. 2;

4 is a diagram showing a detailed circuit configuration of the gain control unit shown in FIG.

<Explanation of symbols for main parts of drawing>

30, 30a, 38: D / A conversion unit 31, 31a, 39, 42: amplification unit

32, 32a, 41: filtering section 33: peak detection section

34: modulator 35: PLL

37: gain control unit 43: switching unit

Hereinafter, a preferred embodiment of an intermediate frequency transmitter in a code division multiple access mobile communication base station apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of an IF transmitter in a CDMA mobile communication base station apparatus according to the present invention. Referring to FIG. First and second D / A converters 30 and 30a for converting a digital signal (14-bit parallel signal) of the component into a baseband analog signal, and first and second D / A converters 30 and 30a. First and second amplifiers 31 and 31a for a predetermined level amplification of the baseband signals of the I / Qs converted into analog signals at &lt; RTI ID = 0.0 &gt; and &lt; / RTI &gt; The first and second filtering units 32 and 32a respectively remove spurious signal components other than the baseband signals of the Q components. Here, the first and second filtering units 32 and 32a are formed of an eighth order LC low pass filter having a Chebyshev characteristic.

In addition, the peak detection unit for detecting the maximum value of the baseband I / Q component signals output from the first and second filtering units 32 and 32a to generate an error occurrence alarm signal of the I / Q channel according to the detection result ( 33), and a modulator 34 which modulates the I / Q signals output from the first and second filtering units 32 and 32a, respectively, and first up-converts them to arbitrary IF signals by a given local frequency. And a first PLL 35 that provides an arbitrary local frequency for I / Q modulation and IF upconversion in the modulator 34. Here, the peak detector 33 is composed of two operational amplifiers 33a and 33b as shown in FIG. 3, and the non-inverting terminals (+) of each of the operational amplifiers 33a and 33b are first and second filtering. The inverting terminals (-) of the operational amplifiers 33a and 33b are common to each other, and the variable resistor VR is connected to the common inverting terminal, and the operational amplifiers 33a and 33b are connected to the output terminals of the units 32 and 32a. Each output end of is connected to a multi vibrator (33c) is configured.

In addition, a third D / A converter 38 for converting digital 8-bit data for adjusting the power level of the IF transmission signal from the signal modulated by the modulator 34 into an analog signal and outputting a gain adjustment signal; And a gain control unit 37 which amplifies or attenuates the IF output signal power to a predetermined level by using a difference between the gain adjustment signal level output from the third D / A converter 38 and the offset voltage. As shown in FIG. 4, the gain control unit 37 is composed of two variable amplifiers 37a and 37b so that the gain adjustment signal level and the offset voltage 0.5 provided by the third D / A converter 38 are provided. The difference between V and 1.5V is used to amplify or attenuate the signal output from the modulator 34.

In addition, the third filtering unit 41 removes the band limit and noise of the IF signal amplified or attenuated by the gain control unit 37, and the third filter amplifies the IF signal filtered by the third filtering unit 41 at a constant level. An amplifying section 42 and an analog switching section 43 for transmitting an up-converted IF signal amplified by the third amplifying section 42 to the RF processing section by a TTL (Transister Transister Logig) control signal. .

The operation of the IF transmitter in the CDMA mobile communication base station apparatus having the above configuration will be described.

First, in the CDMA base station apparatus, the baseband I / Q signal converted into a spread spectrum signal is received from the baseband modulator module as a 14-bit parallel digital signal of I and Q components by the D / A converters 30 and 30a. After sampling at 14.7456 MHz, the sampled 14.7456 MHz signal is converted into a baseband 0-1.8432 MHz analog signal.

The baseband analog signal thus converted is amplified by a predetermined level to match the input signal level of the modulator 34 by the first and second amplifiers 31 and 31a and output to the first and second filtering units 32 and 32a, respectively. do. Then, in the eighth order LC passive low pass filter having the first and second filtering units 32 and 32a, that is, the Scheme-by-Sheve characteristic, the spurious components other than the baseband are removed and then output to the modulator 34, respectively. do. Here, the input / output impedance of the 8th-order LC passive low pass filter is 50 ohm, the pass loss is 0 db, and the pass band is 0-1.8432 MHz.

Accordingly, the modulator 34 performs I / Q modulation on any local frequency generated by the PLL 35 and upconverts the I / Q component signal to an IF signal having the same frequency as the arbitrary local frequency. Here, any local frequency and the up-converted IF signal generated in the first PLL 35 are 70 MHz. That is, the modulator 34 multiplies the I-channel component baseband signal output from the first filtering unit 32 by the 70 MHz local frequency generated by the PLL 35 and multiplies the I-channel component signal by 70 MHz. A signal having a 90 ° phase difference of the local frequency is multiplied by the Q-channel component signal, and is output to the gain control unit 37 in the form of a signal to which the multiplied I / Q channel signal is added.

As such, the IF signal up-converted to 70 MHz by the modulator 34 is output to the gain control unit 37, and the digital 8-bit data input to adjust the power level of the IF transmission signal is an analog signal. The analog signal converted by the A converter 38 is amplified by a predetermined level and provided as a signal for adjusting the gain level of the gain control unit 37. The third D / A converter 38 converts digital 8-bit data into an analog signal of 0-2.5V.

The gain control unit 37 has two variable amplifiers arranged in series so that the gain adjustment level provided from the third D / A converter 39 and the offset voltage of each variable amplifier, that is, the offset of the first variable amplifier 37a. Calculates a difference between the voltage (0.5V) and the gain adjustment level provided by the third D / A converter 38, and amplifies or attenuates the up-converted IF signal output from the modulator 34 according to the difference value; The amplified or attenuated IF signal is output to the second variable amplifier 37b. Accordingly, the second variable amplifier 37b has an offset voltage 1.5V for providing power of the IF signal output from the first variable amplifier amplifier 37a and a gain adjustment level output from the third D / converter 38. The difference from the signal is calculated and amplified or attenuated accordingly.

The 70MHz IF signal output from the gain control unit 37 is removed after the noise is removed through the third filtering unit 41, and then amplified to fit the IF output level through the third amplifier unit 42, and the amplified IF. The signal is transmitted to the RF processor through the switching unit 43. Here, the center frequency filtered by the fourth filtering unit 41 is 70MHz, the pass loss is 4.6dB, the passband has a characteristic of 5MHz.

Briefly summarizing the operation of the IF transmitter in the CDMA mobile communication base station apparatus according to the present invention, the digital signal generated by the baseband modulator is received and converted into an analog signal to amplify units 31 and 31a. ), And the analog signal amplified by the amplifiers 31 and 31a, that is, the signal of the baseband I / Q component, passes through the eighth order low pass filter 32 and 32a having a Zambibe characteristic and is out of band. After the signal component is removed, the modulator 24 is up-converted to the I / Q modulation and the IF signal by the 70 MHz local frequency generated in the PLL 35.

The modulated signal passes through the low noise automatic gain control unit 37, and the 70 MHz IF signal passed through the low noise automatic gain control unit 37 passes through the band pass filter 41 of the center frequency 70 MHz to reduce the band limit and noise of the IF signal. After being removed and amplified by the third amplifier 42 by a certain level, the output is transmitted through the coaxial cable to the RF processor through the analog switching unit 43 whose output is determined by the TTL control signal. Therefore, although not shown in the figure, the RF processor converts the received IF signal into a UHF signal and transmits it through an antenna.

As a result, the IF transmitter in the CDMA mobile communication base station apparatus receives a baseband I / Q signal converted into a spread spectrum signal from a modulator module, converts it into an analog signal, and converts it into an analog signal. The baseband signal is converted to an IF signal of 70 MHz at a time by using a local frequency of 70 MHz to transmit the converted 70 MHz IF signal to the RF processor.

In the mobile communication base station apparatus of the code division multiple access method according to the present invention as described above, the intermediate frequency transmitter receives the baseband I / Q signal converted into a spread spectrum signal from the modulator module and converts it into an analog signal. By converting the baseband signal converted into an analog signal into a 70MHz IF signal at a time by using the 70MHz local frequency provided, the 70MHz IF signal is transmitted to the RF processor for stable I / Q modulation even at a lower frequency. It can perform the function, and since the band of the IF signal is used as 70MHz, there is an effect that can accommodate the baseband signal of a wider band than the conventional mobile communication system. In other words, by up-converting the baseband signal to an IF signal of 70 MHz at once, the distortion of the part-item and the signal is reduced, so that the IF transmitter can be spherically more easily and stably dynamic.

In addition, even if a wider baseband signal is required, there is another effect that the request can be accommodated only by changing the modulation section of the IF section without requiring a change in the RF processing section. Therefore, IF transmitter according to the present invention is a next generation communication service of integrated wired / wireless (IMT-2000) that provides multimedia services such as voice, high-speed data, video, and global roaming to wireless terminals in land and satellite environments. It can be effectively applied to the base station of.

Claims (13)

In the CDMS mobile communication base station apparatus having a baseband modulation module and an RF processing unit, First and second D / A converters for converting a digital signal of an I / Q component modulated into a spread spectrum signal from the baseband modulation module into an analog signal having an arbitrary baseband; First and second amplifiers for amplifying the baseband signals of the I / Qs converted into analog signals by the first and second D / A converters to a predetermined level, respectively; First and second filtering units for removing spurious signal components other than the baseband signals of the I / Q components amplified by the first and second amplifiers, respectively; A peak detector for detecting a maximum value of the baseband I / Q component signals output from the first and second filtering units and generating an alarm signal of an I / Q channel according to a detection result; The first and second filtering units modulate the I / Q signal from which the signal components other than the band are removed, and up-convert to an arbitrary IF signal by a given local frequency, and then add the I signal component and the Q signal component. A modulator for outputting the form; A PLL providing the local frequency for I / Q modulation and IF upconversion in the modulator; A third D / A converter for converting digital 8-bit data into an analog signal for adjusting the power level of the IF transmission signal; A gain control unit which amplifies or attenuates the power of the IF output signal to a predetermined level by using a difference between the gain adjustment signal level output from the third D / A converter and the offset voltage provided; After the signal is amplified or attenuated by the gain control unit, an out-of-band signal is removed from the output signal, amplified by a predetermined level to meet the IF transmission level, and then transmitted to the RF processor to transmit the IF signal amplified by the provided control signal. IF transmitter in the CDMA mobile communication base station apparatus characterized in that it comprises a. delete delete delete delete delete delete delete delete delete delete delete delete