CN103905800A - A Fast Blind Scan Method Insensitive to Adjacent Channel Interference - Google Patents

Abstract

The invention provides a fast blind scanning method insensitive to adjacent channel interference, which is characterized in that a parameter index is initialized to capture a block frequency spectrum, whether a signal with large frequency spectrum amplitude exists in the captured block frequency spectrum or not is judged, the frequency distance between the signal with large frequency spectrum amplitude and a starting point index is larger than a first frequency distance threshold value, and if not, whether the channel is a full-band channel or not is judged. If the channel is a full-band channel, signal detection and parameter acquisition are performed, and the frequency of the starting point index is set as a second cross point. And then, judging whether the difference value of the frequency of the starting point index and the frequency of a terminal point index is smaller than a second frequency distance threshold value, if not, setting a carrier frequency index for capturing the next block frequency spectrum by the tuner. When the channel is empty or partial frequency channel, the frequency and carrier frequency index of the starting point index are also set for the tuner to capture the next block frequency spectrum.

Description

A Fast Blind Scan Method Insensitive to Adjacent Channel Interference

technical field

The invention relates to the technical field of satellite digital television transmission, in particular to a fast blind scan (Blind Scan) method insensitive to adjacent channel interference, which is suitable for DVB-S or DVB-S2 systems.

Background technique

In order for digital TV to develop vigorously, the first task is to establish a digital platform. Digital platform refers not only to pure hardware devices such as set-top boxes (Set-Top Box), but also includes digital channels and digital content.

At present, the main specifications of global digital TV can be divided into several major fields, including the ATSC (Advanced Television Systems Committee) system mainly in the US market, the DVB (Digital Video Broadcasting) system mainly in the European market, and the Chinese mainland market. DTMB (Digital Terrestrial Multimedia Broadcasting) system, and ISDB-T system mainly in the Japanese market. Among them, the DVB system can be subdivided into DVB-C/C2 (Cable), DVB-S/S2 (Satellite), and DVB-T/T2 (Terrestrial). The so-called DVB-C/C2 refers to the cable TV standard, DVB-S/S2 refers to the satellite TV standard, and DVB-T/T2 refers to the terrestrial wireless TV standard.

Through the satellite at an altitude of more than 32,000 kilometers, the central office system operator can transmit the DVB-S/S2 signal to the satellite antenna on the residential building, and use this transmission method to transmit MPEG2 data. Since the position (carrier frequency) and symbol rate (span) of each channel on the frequency spectrum are not clearly regulated, the receiver can choose to pre-store the position (carrier frequency) and its symbol rate (span) of all known channels so that Can quickly receive programs.

However, whenever the carrier frequency and symbol rate of the channel are changed, the above-mentioned pre-storage method may not be able to correctly receive the updated channel. Therefore, in applications such as satellite TV (DVB-S/S2) receivers, blind channel search is a necessary and indispensable function, which provides a convenient mode of operation that allows users to Knowing the information of the received satellite channel, it can automatically scan out all channel parameters. Among them, the scanning speed and correctness are one of the most important indicators to measure the performance of the blind scanning algorithm, that is, fast and correct searching can save the user's waiting time.

FIG. 1 is a block diagram of an existing receiving end. Its working principle is that the control device 11 first sets a carrier frequency (Carrier Frequency, CF) for the tuner (tuner) 12, and then starts the filter bank (filter bank) in the baseband demodulation chip 13 (not shown in the figure) And the timing recovery loop (timing recovery loop) (not shown in the figure), starting from the minimum symbol rate (SR), if the timing loop cannot converge, increase the symbol rate. If the symbol rate exceeds the possible maximum value and has not converged, it means that there is no signal at this frequency point. Then it is necessary to update the carrier frequency of the tuner, add a step (Step) on the original basis, repeat the above steps until the timing loop converges, and then detect the signal and its parameters.

The disadvantage of this method is that the search speed is very slow, because the range of possible symbol rates used in the DVB-S/S2 system is very large, from 1M baud to 45M bauds are possible. Furthermore, the frequency spectrum occupied by the satellite signal is also very wide, and the input range of the Ku or C-band tuner is 950MHz~2150MHz. The combination of the two produces many possibilities, and it will take a long time to search all these possibilities in blind scan. In addition, changing the carrier frequency of the tuner 12 is a time-consuming process, and frequently stepping the carrier frequency will significantly prolong the search time. In addition, the step resolution of the tuner is quite limited, and its typical value is usually only a few hundred MHz, so it is not accurate to detect the carrier frequency simply by changing the frequency of the tuner. At the same time, the convergence of the timing loop is also very slow, and it is quite slow and time-consuming to use the timing loop to search the symbol rate back and forth.

Another problem with blind scan is to reduce the sensitivity to the strength of adjacent channel interference. Because in the frequency spectrum, the strength of each adjacent signal is quite different, and there is still the possibility of being interfered by other systems or strong signal sources. Only by reducing the sensitivity to adjacent channel interference can a fast and accurate channel search be achieved. my country's patent application number 98141858 "Blind scan system and method for DVB-S system" (corresponding to the US 2011/0135042 publication) is a related case filed by the inventor before, although the invention improves and proposes an efficient The blind scan method, but still can not bear the sharp difference in the strength of neighboring signals.

Therefore, the blind scan system and method used in the DVB-S/S2 system in the prior art still needs to be improved.

Contents of the invention

The purpose of the present invention is mainly to provide a fast blind scan method that is insensitive to adjacent channel interference. Suitable for DVB-S or DVB-S2 system. It can prevent signals with large spectrum amplitudes from interfering with adjacent signals with small spectrum amplitudes, so it can correctly detect weaker signals in the DVB-S/S2 system, and can accelerate the speed of signal scanning in the DVB-S/S2 system .

According to the purpose of the present invention, the present invention proposes a fast blind scan method for DVB-S/S2 system, which includes the steps: (A) initializing parameter indicators; (B) setting a tuner to retrieve a zone Block spectrum; (C) Judging whether there is a signal with large spectrum amplitude in the block spectrum and the frequency distance between the signal with large spectrum amplitude and a starting point index is greater than a first frequency distance threshold (BW_th1); (D) If it is determined There is no signal with large spectrum amplitude in the spectrum of this block or the frequency distance between the signal with large spectrum amplitude and a starting point index is greater than the first frequency distance threshold (BW_th1), and then judge whether it is a full-band channel (full-bandchannel) ); (E) If it is a full-band channel (full-band channel), perform signal detection and parameter extraction; (F) Set the frequency of the starting point indicator (SP) as a second crossover point (CP2) ; (G) Judging whether the difference between the frequency of the starting point index (SP) and the frequency of an end point index (EP) is less than a second frequency distance threshold (BW_th2); (H) If it is determined that the starting point index (SP ) frequency and the frequency of an end index (EP) is not less than a second frequency distance threshold (BW_th2), then set a carrier frequency index (CF), and perform step (B) so that the tuner Capture the next block of spectrum. When the channel is empty or part of the frequency band, the frequency of the starting point index and the carrier frequency index (CF) are also set respectively, so that the next block of spectrum can be extracted by the tuner. This completes the quick blind scan method.

Description of drawings

FIG. 1 is a block diagram of an existing receiving end.

Fig. 2 is a system block diagram of a fast blind scan method used in the DVB-S/S2 system of the present invention.

Fig. 3 is a flowchart of a fast blind scan method used in the DVB-S/S2 system of the present invention.

Fig. 4 is a schematic diagram of an embodiment of the present invention, (S1): (|CP1-SP|>BW_th1) & (M>8m)→EP=CP1.

FIG. 5 is a schematic diagram of an embodiment of the present invention, ( S2 ): SP<CP1<CP2<EP→detection and parameter extraction.

FIG. 6 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

Fig. 7 is a schematic diagram of an embodiment of the present invention, (S1): (|CP1-SP|>BW_th1)&(M>8m)→EP=CP1.

FIG. 8 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

FIG. 9 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

FIG. 10 is a schematic diagram of an embodiment of the present invention, (S2): SP<CP1<CP2<EP→detection and parameter extraction.

FIG. 11 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

Fig. 12 is a schematic diagram of an embodiment of the present invention, (S3): CP2>EP→SP=CP1.

FIG. 13 is a schematic diagram of an embodiment of the present invention, (PT): the next block of spectrum is captured by the tuner.

FIG. 14 is a schematic diagram of an embodiment of the present invention, (S2): SP<CP1<CP2<EP→detection and parameter extraction.

FIG. 15 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

Fig. 16 is a schematic diagram of an embodiment of the present invention, (S4): (CP1=SP_org) and (CP2=EP_org)→SP=EP.

FIG. 17 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

Fig. 18 is a schematic diagram of an embodiment of the present invention, (S1): (|CP1-SP|>BW_th1)&(M>8m)→EP=CP1.

FIG. 19 is a schematic diagram of an embodiment of the present invention, (S2): SP<CP1<CP2<EP→detection and parameter extraction.

Fig. 20 is a schematic diagram of an embodiment of the present invention, (S5): |SP-EP|<BW_th2→SP=EP.

FIG. 21 is a schematic diagram of an embodiment of the present invention, (PT): The next block of spectrum is captured by the tuner.

FIG. 22 is a schematic diagram of an embodiment of the present invention, (S2): SP<CP1<CP2<EP→detection and parameter extraction.

Fig. 23 is a schematic diagram of an embodiment of the present invention, (S6): |CF>CF_max|→the program ends.

Fig. 24 is a comparison diagram between the present invention and the prior art.

Description of main component symbols:

Control device 11 Tuner 12

Baseband demodulation chip 13

Blind Scan System 200

Tuner (tuner) 205 Analog to Digital Converter 210

Tuner automatic gain control device 215

Digital mixer 220 Interpolation device 225

Digital automatic gain control device 230 Digital matched filter 235

Spectrum calculation device 240 Spectrum parameter extraction device 245

Control device 250 Antenna 211

Step (A) ~ Step (O).

Detailed ways

Fig. 2 is a block diagram of a fast blind scan method system 200 used in the DVB-S/S2 system of the present invention, including: a tuner (tuner) 205, an analog to digital converter (Analog to digital converter, ADC) 210, a tuner automatic gain control device (AGC) 215, a digital mixer (Digital Mixer) 220, an interpolation device (Interpolation Device) 225, a digital automatic gain control device (DAGC) 230, a digital matched filter Digital Matched Filter (DMF) 235, a spectrum calculation device 240, a spectrum parameter extraction device 245, and a control device 250.

The Chinese patent application No. 98141858 "Blind scan system and method for DVB-S system" (corresponding to US 2011/0135042 publication) is a related case applied by the inventor. The present invention is to improve the blind scanning method in this patent application, and the present invention uses the same hardware components as this patent application, so the aforementioned components of the present invention can be found in the Chinese patent application No. 98141858 applied by the inventor, here No longer.

Fig. 3 is a flowchart of a fast blind scan method used in a DVB-S/S2 system according to the present invention. First in step (A), the parameter index is initialized. The parameter index includes the starting point index (SP), the end point index (EP), a carrier frequency index (CF), a starting point original index (SP_org), and an end point original index (EP_org).

The frequency band in the DVB-S/S2 system is 950MHz~2150MHz. Each frequency band is 1MHz~45MHz. It is therefore assumed that the minimum required sampling rate is 90MHz. During initialization, the digital mixer (Digital Mixer) 220 and the interpolation device (Interpolation Device) 225 do not act, but only let the signal pass through, wherein the starting point index (SP) and the starting point original index (SP_org ) is set to 950MHz, the endpoint index (EP) and the endpoint original index (EP_org) are set to 995MHz (950+45), and the carrier frequency index (CF) is set to 972.5MHz (950+45/2).

In terms of physical meaning, the DC component of the digital signal spectrum at the output of the interpolation device (Interpolation Device) 225 corresponds to the carrier frequency index (CF) and the end point index (EP) set by the tuner (tuner) 205 And the difference between the starting point index (SP) (that is, the difference between EP_org and SP_org) is half of the sampling rate. When the digital mixer and the interpolation device (Digital Mixer) 220 (Interpolation Device) 225 operate, the two values can be equivalently adjusted as required to detect the signal. This can be accomplished by those skilled in the art based on the disclosure of the present invention and the prior art, and will not be repeated here.

In step (B), a tuner 205 is set to capture a block frequency spectrum.

In step (C), it is judged whether there is a signal with large spectrum amplitude in the frequency spectrum of the block and the frequency distance between the signal with large spectrum amplitude and a starting point index (SP) is greater than a first frequency distance threshold (BW_th1). That is, the step (C) can be expressed as: (|CP1-SP|>BW_th1) & (M>8m) by a mathematical formula.

Step (C) is used to detect signals with large spectrum amplitude, which can be expressed by a mathematical formula: M>8m, where M is the highest value in the spectrum of the block, and m is the lowest value in the spectrum of the block. That is to say, in step (C), it is detected whether the highest value (M) of the signal with large spectrum amplitude is eight times the lowest value (m) in the frequency spectrum of the block.

The frequency distance between the signal with large spectrum amplitude and a starting point index is greater than a first frequency distance threshold value (BW_th1), which can be represented by a mathematical formula: (|CP1-SP|>BW_th1). Among them, CP1 is the first crossing point (CP1) at the frequency at which the first frequency in the spectrum of the block is greater than an amplitude threshold (amp_th), SP is the starting point index (SP), and BW_th1 is the frequency distance threshold (BW_th1).

As shown in FIG. 4 , there are three signals between the starting point indicator (SP) and the end point indicator (EP), namely signal 1 , signal 2 , and signal 3 . Wherein, compared with signal 1 and signal 2, signal 3 is a signal with a larger spectrum amplitude, so the highest value M in the spectrum of this block is the amplitude of signal 3 . When the signal amplitude is small, since it is impossible to distinguish what is signal and what is noise, the lowest value m in the spectrum of this block is noise floor.

The amplitude threshold (amp_th) can be calculated from the highest value M and the lowest value m, wherein the amplitude threshold (amp_th) is:

amp_th=(M-m)×η+m,

Among them, M is the highest value (M) in the spectrum of the block, m is the lowest value (m) in the spectrum of the block, and η is an adjustment factor. In a preferred example, the adjustment factor η can be 0.3.

As shown in FIG. 4 , the frequency in the block frequency spectrum that is lower than the amplitude threshold value (amp_th) for the first time is the second crossover point (CP2).

If it is determined that there is no signal with large spectral amplitude in the block spectrum or the frequency distance between the signal with large spectral amplitude and a starting point indicator (SP) is greater than the first frequency distance threshold (BW_th1), then in step (D) Determine whether it is a full-band channel.

In step (D), the full-band channel (full-band channel) means that the frequency of the end point (EP) is greater than the frequency of the second crossover point (CP2), and the frequency of the second crossover point (CP2) Greater than the frequency of the first crossing point (CP1), the frequency of the first crossing point (CP1) is greater than the frequency of the starting point index (SP), that is, step (D) can be expressed as SP<CP1< CP2<EP.

In step (E), if it is a full-band channel, signal detection and parameter extraction are performed.

In step (F), the frequency of the starting point index (SP) is set as a second crossing point (CP2). Step (F) can be expressed mathematically as SP=CP2.

In step (G), it is judged whether the difference between the frequency of the starting point index (SP) and the frequency of an end point index (EP) is smaller than a second frequency distance threshold (BW_th2). Step (G) can be represented by a mathematical formula: |SP-EP|<BW_th2.

In step (H), when it is determined in step (G) that the difference between the frequency of the starting point index (SP) and the frequency of an end point index (EP) is not less than a second frequency distance threshold (BW th2), then Set the carrier frequency index (CF), and execute step (N).

In step (N), it is judged whether a search range spectrum has been scanned, if so, end the blind scan method, if not, set the starting point index (SP), the end point index (EP) in step (O) ). Step (B) is then executed to obtain the next block of frequency spectrum by the tuner.

In step (I), when it is determined in step (C) that there is a signal with large spectrum amplitude in the frequency spectrum of the block and the frequency distance between the signal with large spectrum amplitude and a starting point index is greater than the frequency distance threshold value, set the end point The frequency of the index (EP) is a first crossing point (CP1). Step (I) can be expressed by a mathematical formula: EP=CP1.

In step (J), when it is determined in step (D) that it is not a full-band channel (full-band channel), then determine whether it is an empty channel (empty channel). Step (J) empty channel means that the frequency of the first crossover point (CP1) is equal to the frequency of the original index (SP_org) of the starting point, and the frequency of the second crossover point (CP2) is equal to the original index of the end point (SP_org). Frequency of indicators (EP_org). Step (J) can be represented by a mathematical formula: (CP1=SP_org) & (CP2=EP_org)

In step (K), when it is determined as an empty channel (empty channel) in step (J), set the frequency of the starting point index (SP) as the frequency of the end point index (EP). Step (K) can be represented by a mathematical formula: SP=EP.

In step (L), when it is determined in step (J) that it is not an empty channel (empty_channel), then it is determined whether it is a partial-band channel. Wherein, the partial-band channel in step (L) means that the frequency of the second crossover point (CP2) is greater than the frequency of the end index (EP). Step (L) can be represented by a mathematical formula: (CP2>EP).

In step (M), when it is determined in step (L) that it is a partial-band channel, then set the frequency of the starting point index (SP) as a first crossover point (CP1). Step (M) can be represented by a mathematical formula: SP=CP1. When it is determined in step (L) that it is not a partial-band channel, return to step (B).

In step (N), it is judged whether the spectrum of a search range has been scanned, and if so, the blind scanning method is terminated. Step (N) can be expressed by a mathematical formula: CF>CF_max, wherein, since the frequency band in the DVB-S/S2 system is 950MHz~2150MHz, CF_max can be preset as 2150MHz. In other embodiments, in order to detect more signals, CF_max can be preset to 2172.5MHz (2150+22.5).

If in step (N), it is determined that the spectrum of the search range is scanned, then in step (O), set the start point index (SP) and the end point index (EP), and then execute step (B). Step (O) can be represented by a mathematical formula: SP=SP_org, EP=EP_org.

When it is determined in step (G) that the difference between the frequency of the starting point index (SP) and the frequency of the end point index (EP) is smaller than the second frequency distance threshold (BW_th2), step (K) is executed.

4 to 23 are schematic diagrams of an embodiment of the present invention. Please cooperate with the flowchart in Figure 3. As shown in FIG. 4 , signal 3 is a signal with a large spectrum amplitude, which can easily cover up signal 1 and signal 2 . In the prior art, the signal 1 and the signal 2 cannot be detected correctly due to the signal with large spectrum amplitude.

Therefore, the highest value M in the frequency spectrum of this block is the amplitude of signal 3 . When the signal amplitude is small, since it is impossible to distinguish what is signal and what is noise, the lowest value m in the spectrum of this block is the noise floor.

Since the signal 3 with a large spectrum amplitude exists, the amplitude threshold (amp_th) will be raised, and the first crossover point ( CP1 ) and the second crossover point ( CP2 ) will intersect the signal 3 . The frequency spectrum on the left of the starting point index (SP) represents the scanned frequency spectrum, and the present invention scans the frequency spectrum from the right spectrum of the starting point index (SP) to the end point index (EP).

As shown in Figure 4 to Figure 23, the two dots intersecting the amplitude threshold value (amp_th), the dot on the left is the first crossing point (CP1), and the dot on the right is the second crossing point ( CP2).

As shown in Figure 4, the first crossing point (CP1) is too far away from the starting point index (SP), and because there is a signal 3 with a large spectrum amplitude, the present invention hopes that the starting point index (SP) and the first The frequency spectrum between a crossover point (CP1) is scanned instead of being ignored directly, so in step (I), the frequency of the end point indicator (EP) is set as the frequency of the first crossover point (CP1) (EP =CP1).

When one of the judgment formulas (|CP1-SP|>BW_th1) or (M>8m) in step (C) is not established, then execute step (D). As shown in Figure 5, M is not greater than 8m. At this time, there is no signal with large spectrum amplitude in the spectrum between the starting point index (SP) and the end point index (EP). At the same time, the judgment formula SP<CP1<CP2 <EP is also established, which means that there is a full-band channel (full-band channel) in the spectrum between the starting point index (SP) and the end point index (EP), so step (E) is performed to perform signal detection and parameter extraction .

As shown in Figure 6, after step (E) is executed, it means that the signal 1 has been detected and the parameters are extracted, so the tuner 205 is set to acquire the next block spectrum (Programming Tunner, PT), etc. related steps. Therefore, in step (F), the frequency of the starting point index (SP) is set as a second crossing point (CP2). The related technology of signal detection and parameter extraction in step (E) can be found in Chinese patent application No. 98141858 (corresponding to US 2011/0135042 publication) applied by the inventor.

In step (G), when the difference between the frequency of the starting point index (SP) and the frequency of the end point index (EP) is less than a second frequency distance threshold (BW_th2), it means that the starting point index (SP) The spectrum between the frequency of the starting point index (SP) and the end point index (EP) is too small, and there may be no signal, so the frequency between the frequency of the starting point index (SP) and the end point index (EP) can be skipped directly, so perform the step ( K). As shown in Figure 6, the spectrum between the frequency of the starting point index (SP) and the end point index (EP) will not be too small (greater than BW_th2), indicating that there may be a signal, so perform step (H), set The carrier frequency indicator (CF) is CF+SP-SP_org.

In step (N), it is judged whether the spectrum of a search range has been scanned. If the scan has not been completed (CF>CF_max is not established), step (O) is executed, and the starting point index (SP) is set as SP_org, and the end point index ( EP) is EP_org, and step (B) is performed to retrieve the next block of spectrum by this tuner, as shown in FIG. 7 .

In Figure 8, since there is a signal 3 with a large spectrum amplitude in the frequency spectrum between the starting point index (SP) and the end point index (EP), step (I) is performed to set the end point index (EP) The frequency is the first crossover point (CP1).

Afterwards, through steps (D) and (E), signal 2 is detected and parameters are extracted. As shown in FIG. 9 , in step (F), the frequency of the starting point index (SP) is set as a second crossing point (CP2). As shown in Figure 9, the spectrum between the frequency of the starting point index (SP) and the end point index (EP) will not be too small (greater than BW_th2), indicating that there may be a signal, so step (H), step ( N), step (O), and capture the next block of frequency spectrum.

As shown in Figure 10, the spectrum between the starting point index (SP) and the first crossing point (CP1) is not too large, so the judgment formula in step (C) (|CP1-SP|>BW_th1) If not, go to step (D). At the same time, the judgment formula SP<CP1<CP2<EP in step (D) is also established, indicating that there is a full-band channel (full-band channel) in the spectrum between the starting point index (SP) and the end point index (EP) , so step (E) is executed to perform signal 3 detection and parameter extraction, and set the frequency of the starting point indicator (SP) as the second crossing point (CP2), as shown in FIG. 11 . Since the difference between the frequency of the starting point index (SP) and the frequency of the end point index (EP) is not less than a second frequency distance threshold (BW_th2), step (H), step (N), and step (O ) to extract the spectrum of the next block, as shown in Figure 12.

As shown in Figure 12, after step (C) is executed, because CP2 is greater than EP, the judgment formula SP<CP1<CP2<EP in step (D) does not hold true, indicating that the block spectrum is not a full-band channel (full -bandchannel), and may be an empty channel (empty channel), so judge CP1=SP_org and CP2=EP_org in step (J). As shown in Figure 12, it is not established, so step (L) is executed.

In step (L), it is judged whether CP2 is greater than EP. Since CP2 is greater than EP, step (M) is executed to set the frequency of the starting point index (SP) as the first crossing point (CP1), as shown in Figure 13, and then step (H), step (N), step (O) to extract the spectrum of the next block, as shown in FIG. 14 .

As shown in FIG. 14 , after step (C) and step (D) are executed, signal 4 detects and extracts parameters in step (E). Then in step (F), the frequency of the starting point index (SP) is set as the second crossing point (CP2), as shown in Figure 15, since the frequency of the starting point index (SP) is different from the frequency of the end point index The frequency difference of (EP) is not less than a second frequency distance threshold (BW_th2), so step (H), step (N), and step (O) are executed to retrieve the next block of spectrum, as shown in Figure 16 shown.

In FIG. 16 , since there is no signal between the start point index (SP) and the end point index (EP), the amplitude threshold (amp_th) is about noise floor. Therefore, at this time, the first crossing point (CP1) is the starting point index (SP), and the second crossing point (CP2) is the end point index (EP). Therefore, after step (C) and step (D), it is judged in step (J) whether it is an empty channel (empty channel). Since the judgment formula in step (J): (CP1=SP_org) & (CP2=EP_org) is established, step (K) is executed to set the frequency of the starting point index (SP) as the end point index (EP) , thereby skipping the frequency spectrum between the starting point index (SP) and the end point index (EP), as shown in FIG. 17 . Afterwards, step (H), step (N), and step (O) are executed again to capture the frequency spectrum of the next block, as shown in FIG. 18 .

As shown in Figure 18, since the amplitude of signal 6 is large and the frequency distance between signal 6 and the starting point index (SP) is greater than the first frequency distance threshold (BW_th1), the judgment formula of step (C) is established, and the execution Step (I), to set the frequency of the endpoint index (EP) as the frequency of the second crossover point (CP2), as shown in FIG. 19 . Afterwards, through step (C), step (D), and in step (E), the signal 5 is detected and parameters are extracted. As shown in FIG. 19, in step (F), set the frequency of the starting point index (SP) as a second crossing point (CP2). As shown in Figure 20.

As shown in Figure 20, in step (G), since the difference between the frequency of the starting point index (SP) and the frequency of the end point index (EP) is less than a second frequency distance threshold (BW_th2), it means that the start The spectrum between the frequency of the start point indicator (SP) and the end point indicator (EP) is too small, and there may be no signal. You can directly skip the frequency between the frequency of the start point indicator (SP) and the end point indicator (EP). , so execute step (K) and set SP as EP, as shown in Figure 21. Afterwards, step (H), step (N), and step (O) are executed again to capture the frequency spectrum of the next block, as shown in FIG. 22 .

As shown in FIG. 22 , after step (C), step (D), step (E), step (F), step (G) and step (H) are executed, it is shown in FIG. 23 . Then in step (N) it is judged whether the spectrum of a search range has been scanned. Since CF is greater than the preset value of the carrier frequency (CF_max), the blind scan method ends.

Fig. 24 is a comparison diagram between the present invention and the prior art. They all use Sharp's tuner (tuner): Sharp7306, and measure the time required to generate screen images by the blind scan method. The 950MHz~2150MHz frequency band of the DVB-S/S2 system is divided into two frequency bands, C (22k) and Ku (non22k), the front 600MHz is 22k, and the back 600MHz is non22k. At the same time, each frequency band can be divided into vertical polarization (Vertical polarization) and horizontal polarization (Horizontal polarization). As shown in Figure 24, under 22k vertical polarization, the present invention takes 1 minute and 16 seconds (1'16"), while the prior art takes 2 minutes and 01 seconds (2'1"). Under non22k vertical polarization, the present invention takes 12 seconds (12"), while the prior art takes 35 seconds (35"). At 22k horizontal polarization, the present invention takes 1 minute and 7 seconds (1'7"), while the prior art takes 1 minute and 27 seconds (1'27"). Under non22k horizontal polarization, the present invention takes 1 minute and 58 seconds (1'58"), while the prior art takes 3 minutes and 55 seconds (3'55").

It can be seen from the above description that the present invention uses the judgment formula of step (C) to prevent the signal with large spectrum amplitude from interfering with the signal with small amplitude of adjacent spectrum, so it can correctly detect the signal with small amplitude in the DVB-S/S2 system . At the same time, the judgment formulas of step (G) and step (J) can accelerate the speed of signal scanning in the DVB-S/S2 system, so in actual measurement, both have better detection performance than the prior art. At the same time, the present invention uses the analog tuner to capture and scan the entire frequency spectrum with a larger step size, so as to capture a new frequency spectrum block in the analog domain, and use a digital mixer in the digital domain. It supports subsequent channel and parameter detection. Therefore, the speed of the overall blind scan method is greatly improved. The present invention can dynamically adjust the adjustment factor η according to the frequency spectrum observed in each calculation loop, and adaptively determine the amplitude threshold value (amp_th), and then in the frequency spectrum as much as possible High and low channels can be accurately detected, thereby reducing the chance of channels being missed. Furthermore, since the number of times the carrier frequency of the tuner 12 is changed is minimized, the goal of fast and accurate channel search can finally be achieved.

From the above, it can be known that the present invention has features that are very different from the prior art in terms of purpose, means and efficacy, and has great practical value. However, it should be noted that the above-mentioned embodiments are examples only for convenience of description, and the scope of rights claimed by the present invention should be determined by the claims, rather than limited to the above-mentioned embodiments.

Claims (16)

1. disturb insensitive Fast Blind to sweep a method for DVB-S/S2 system to adjacent channel, it comprises step:

A) initiation parameter index;

B) set a tuner in order to capture a block frequency spectrum;

C) judge and in described block frequency spectrum, whether have signal that a spectral amplitude is large and the large signal of described spectral amplitude and the frequency distance of a starting point index be greater than a first frequency distance threshold value;

D) in described block frequency spectrum, do not have signal that signal that a spectral amplitude is large or described spectral amplitude are large and the frequency distance of a starting point index not to be greater than described first frequency distance threshold value if judge, then determine whether a full frequency band passage;

E) if full frequency band passage carries out input and parameter acquisition;

F) frequency of setting described starting point index is one second crossover point;

Whether the difference that G) judges the frequency of described starting point index and the frequency of a terminal index is less than a second frequency distance threshold value;

H) if judge the non-second frequency distance threshold value that is less than of the difference of the frequency of described starting point index and the frequency of a terminal index, set a carrier frequency index, and perform step B) in order to be captured next block frequency spectrum by described tuner.

2. the method for eliminating illiteracy fast according to claim 1, it further comprises:

I) as step C) in judge have in described block frequency spectrum signal that a spectral amplitude is large and the large signal of described spectral amplitude and the frequency distance of described starting point index be greater than described frequency distance threshold value, the frequency of setting described terminal index is one first crossover point.

3. Fast Blind according to claim 2 is swept method, and it further comprises:

J) as step D) in judge that described block frequency spectrum is non-during as described full frequency band passage, then determined whether passage.

4. Fast Blind according to claim 3 is swept method, and it further comprises:

K) as step J) in be judged to be sky passage, the frequency of setting described starting point index is the frequency of described terminal index.

5. Fast Blind according to claim 4 is swept method, and it further comprises:

L) as step J) in to judge non-be empty passage, then determine whether a part of frequency range passage.

6. Fast Blind according to claim 5 is swept method, and it further comprises:

M) as step L) in be judged to be described band segment passage, the frequency of setting described starting point index is one first crossover point.

7. Fast Blind according to claim 5 is swept method, wherein, as step L) in judge non-ly as described band segment passage, perform step B).

8. Fast Blind according to claim 7 is swept method, and it further comprises:

N) judge whether been scanned of a search area frequency spectrum, if so, finish the described blind method of sweeping, if not, at step O) in set described starting point index, and described terminal index, then perform step B).

9. Fast Blind according to claim 8 is swept method, wherein, as step G) in judge that the difference of the frequency of described starting point index and the frequency of described terminal index is less than described second frequency distance threshold value, performs step K).

10. Fast Blind according to claim 9 is swept method, wherein, step C) described in block frequency spectrum have the signal that described spectral amplitude is large to refer to the octuple that in described block frequency spectrum, peak is minimum.

11. Fast Blinds according to claim 9 are swept method, wherein, step D) in full frequency band passage refer to that the frequency of described terminal index is greater than the frequency of described the second crossover point, the frequency of described the second crossover point is greater than the frequency of described the first crossover point, and the frequency of described the first crossover point is greater than the frequency of described starting point index.

12. Fast Blinds according to claim 8 are swept method, wherein, the frequency that is greater than for the first time described amplitude threshold in described block frequency spectrum is described the first crossover point, and the frequency that is less than for the first time described amplitude threshold in described block frequency spectrum is described the second crossover point.

13. Fast Blinds according to claim 12 are swept method, and wherein, described amplitude threshold amp_th is:

amp_th=(M-m)×η+m，

In the middle of, M is peak in described block frequency spectrum, and m is minimum in described block frequency spectrum, and η is an adjustment factor.

14. Fast Blinds according to claim 13 are swept method, wherein, step J) in described empty passage refer to that the frequency of described the first crossover point equals the frequency of a starting point original index, the frequency of described the second crossover point equals the frequency of a terminal original index.

15. Fast Blinds according to claim 14 are swept method, wherein, step L) in band segment passage refer to that the frequency of described the second crossover point is greater than the frequency of described terminal index.

16. Fast Blinds according to claim 14 are swept method, wherein, step N) in search area frequency spectrum been scanned refer to that described carrier frequency index is greater than a carrier frequency preset value.

Images