CN100459667C - Digit satellite frequency channel blind search method based on automatic gain control value - Google Patents
Digit satellite frequency channel blind search method based on automatic gain control value Download PDFInfo
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Abstract
The method includes following steps: a) the blind scan initialization is made for front-end system in use for receiving radio frequency that includes high frequency head and demodulator; b) by controlling high frequency head, scan is made in preset frequency and in a certain frequency interval to get auto gain control value at each frequency point; c) with processing the obtained value, several frequency points with stronger energy are selected to be as candidate frequency; d) the symbol rate scan is made at each candidate frequency point, if a symbol rate can be locked, then saves the frequency point and symbol rate; otherwise, the candidate frequency point is considered invalid.
Description
Technical field
The present invention relates to the searching method of digital terrestial television channels, relate in particular to a kind of blind method of sweeping of controlling the digital terrestial television channels of (AGC) value based on automatic gain.
Background technology
So-called blind sweeping is implemented in the method that searches out the channel that is loaded with digital signal under the situation of satellite repeater unknown parameters exactly.
Satellite television programming is normally transmitted by the transponder that is positioned at the satellite on the geostationary orbit.Transponder from satellite to ground forwarding one road extremely high frequency signal (usually 11 to 12GHz), one or more transport stream (transport stream contains multichannel video-audio program signal) of middle carrying.The modulation system of general satellite digital TV signal is QPSK (a Quadrature Phase Shift Keying keying phase shift modulation).Each transponder has 4 physical parameters: 1. frequency; 2. symbol rate; 3. polarised direction; 4. forward error correction.
The reception of satellite digital TV needs two complete equipments at least: 1. antenna and low noise unit (LNB); 2. digital TV set-top box.The effect of antenna is to converge satellite-signal to its focus, enhancing signal intensity.LNB is the receiving equipment of satellite repeater actual signal, and it is installed on the focus of antenna.LNB is down-converted to the signal frequency range that the satellite television set-top box can receive to the satellite repeater signal.Each LNB has its oneself centre frequency, and its output frequency is the absolute value of satellite repeater frequency and LNB centre frequency difference.
The module that the satellite television set-top box receives the LNB output signal is referred to as the set-top box radio-frequency front-end usually or is called for short front end, and the frequency range of its received signal is from 950 to 2150 megahertzes (MHz).In addition, the satellite television set-top box also comprises microprocessor, memory and procedure stores memory.It generally is divided into two parts: 1. tuner unit and 2. demodulator unit.The effect of tuner unit is the tuning radiofrequency signal that receives from LNB, and it is changed into baseband signal and passes to demodulator unit.In order to want to receive the energy of satellites transmits, the polarised direction that must control satellite earth antenna is consistent with the electric wave direction of transponder emission.
The effect of demodulator unit has two aspects: be the parameters such as automatic gain control that will control tuner on the one hand, to reach best reception.On the other hand, be demodulated to the digital signal that digital television decoder can be decoded to base band QPSK satellite-signal.Because transport stream is according to certain symbol rate data to be weaved into symbol transmission in modulated process, compile according to certain error correction code rate simultaneously and add forward error correction, so in demodulating process, must be according to the correct symbol rate and the forward error correction code check of transport stream, can success catch transport stream.
Thereby the digital satellite television set-top box receives the digital television signal of certain transponder, must know its frequency, symbol rate, forward error correction and polarised direction.In general, most now front ends can be discerned forward error correction automatically, thereby do not relate to forward error correction in the searching method here.
At present, Jue Daduoshuo satellite set top box front end does not all have the blind function of sweeping of hardware.Its blind sweeping all is that front end travels through all frequencies and symbol rate realizes by controlling.Suppose every Frequency point of 1M scanning, 450 symbol rates of each Frequency point scanning, the stand-by period of each symbol rate is 500ms.Then like this maximum duration of scanning is (2150-950) * 450*0.5=270000 second=75 hour, just approximately takes more than 3 days.
Therefore, need a kind of method that can search the digital satellite signal channel in the short time.
Summary of the invention
The objective of the invention is under the prerequisite that antenna has correctly been installed, can under the situation of satellite repeater unknown parameters, in a short period of time, search all satellite repeaters that this antenna can be received.
According to the present invention, the digital signal of microprocessor control front end reception and instrumented satellite transponder, carry out a series of processing, find out the physical parameter of each transponder, and then lock each transponder and search all digital channels according to these physical parameters.It may further comprise the steps:
(a) front end system of microprocessor and received RF carries out the blind initialization of sweeping, and wherein the front end system of received RF comprises tuner and demodulator;
(b) microprocessor control tuner calculates good frequency range interscan with certain frequency interval in advance, obtains the automatic gain control value of each Frequency point;
(c), draw the frequency spectrum of echo signal system, then according to some Candidate Frequency points are found in the analysis of frequency spectrum by processing and calculating to these values;
(d) microprocessor control tuner carries out symbol rate scanning at each Candidate Frequency point, if can lock a symbol rate, then stores this Frequency point and symbol rate; Otherwise, think that this Candidate Frequency point is invalid.
Preferably, the difference according to satellite band when scanning in the step (b) is used different sweep bandwidths, and promptly for the C-band satellite, sweep bandwidth is that LNB centre frequency-4200MHz is to LNB centre frequency-3400MHz; For the Ku band satellite, sweep bandwidth is that 950MHz is to 2150MHz.
Preferably, the method of seeking Candidate Frequency in the step (c) is, if the resulting automatic gain control value of any one frequency is less than a thresholding, this frequency then is rejected not as considering so, otherwise, described frequency is as Candidate Frequency, and wherein this thresholding multiply by a coefficient for the geometrical mean of each frequency automatic gain control value, and wherein this coefficient is slightly larger than 1.
Preferably, can handle for carrying out deburring automatic gain control value, promptly add up the automatic gain control value of 2 frequencies about each Frequency point, if the automatic gain control value of two points in its left side and two points in the right all equates, and the automatic gain control value of this point itself is than their a big unit, a perhaps little unit thinks that then this point is burr, and its automatic gain control value substitutes with the automatic gain control value of left and right sides consecutive points.
Preferably, can be weighted average treatment to automatic gain control value, promptly the automatic gain control value for each frequency goes weighted average to handle, and obtains the weighted average of each frequency automatic gain control.
Seek in the step (c) Candidate Frequency method can also for:
At first, go weighted average to handle, obtain the weighted average of each frequency automatic gain control for the AGC value of each frequency;
Secondly, check the weighted average change direction of each Frequency point, if the change direction of weighted average becomes smooth by rising or decline, this Frequency point will be used as initial Candidate Frequency point;
Then, at this Candidate Frequency, calculate three dB bandwidth and/or breakover point bandwidth, wherein, three dB bandwidth is the weighted average according to each Candidate Frequency, seek the Frequency point of energy than the low 3dB of Candidate Frequency left and to the right respectively, the difference on the frequency of the energy Frequency point of these two low 3dB is exactly the three dB bandwidth of Candidate Frequency; The breakover point bandwidth is in the process that the searching 3dB that turns left or turn right is ordered, when appearance weighted average curve becomes rising by decline, the weighted average that at first finds breakover point higher in the breakover point of the left and right sides is as the bandwidth measurement energy point, calculates then at energy at the difference on the frequency of the left and right sides of this some Frequency point as the breakover point bandwidth;
Then, the frequency intermediate value with left and right sides 3dB or breakover point is the centre frequency of Candidate Frequency;
At last, be far smaller than the AVG value of contiguous blocked Candidate Frequency if find the weighted average of certain Candidate Frequency, think that so this Candidate Frequency is invalid, the critical parameter here need be according to measuring decision.
Preferably, in the step (d) each Candidate Frequency point is carried out symbol rate when scanning, the sweep limits of symbol rate is to set like this: if the turnover bandwidth of Candidate Frequency is lower than 4MHz, its bandwidth will be set as 4MHz; If Candidate Frequency has three dB bandwidth and breakover point bandwidth simultaneously, the sweep limits of symbol rate will be from
To breakover point bandwidth * 2.5 Hes
To three dB bandwidth * 2; If Candidate Frequency has only three dB bandwidth, the sweep limits of symbol rate will be from
To three dB bandwidth * 2.
Preferably, during to each symbol rate scanning beginning, at first attempt the symbol rate that successfully locked last time in the step (d).
Preferably, the ordering of the symbol rate of being swept in the step (d) for by the high more symbol rate of frequency of utilization to the low more symbol rate of frequency of utilization.
The present invention is according to the characteristics of the front end of digital satellite television set-top box, go for most digital satellite television set-top box and similar system thereof, front end is not had any specific (special) requirements, search speed also is relatively independent of the processing speed of rear end control chip.Use method of the present invention and can shorten blind sweeping the used time greatly.
Description of drawings
The present invention is described in detail below in conjunction with drawings and Examples, in the accompanying drawing:
Fig. 1 is set-top-box system figure;
Fig. 2 is the set-top box radio-frequency front-end system;
Fig. 3 is the blind flow chart of sweeping method of prior art;
Fig. 4 is the blind method general flow chart of sweeping of the present invention;
Fig. 5 is the frequency scanning flow chart of one embodiment of the invention;
Fig. 6 is the symbol rate scanning flow chart of one embodiment of the invention;
Fig. 7 is the burr removing method diagram;
Fig. 8 is satellite frequency scanning curve (AGC) and weighted average curve (AVG);
Fig. 9 bandwidth calculation diagram;
Figure 10 centre frequency is calculated diagram.
Embodiment
Be example with the digital satellite television channel below, illustrate content of the present invention, sweep but the present invention is not limited to the blind of digital satellite television channel, it also can be used for fields such as digital satellite data broadcasting.
Fig. 1 shows the digital satellite television set-top-box system.The subsystem that a radio-frequency front-end is arranged in set-top box, a microprocessor is done computing, the program of a procedure stores memory storage computing, a memory is used for storing operation program and finishing required parameter of computing and parameter when start.
Fig. 2 shows the front terminal system of digital satellite television set-top box.Microprocessor is controlled tuner by the control interface on the demodulator.The parameter of control comprises frequency, inner filter bandwidht etc.Tuner is done at the satellite-signal that LNB receives and with I/Q (inphase/orthogonal) holding wire the modulated digital TV signal is passed to demodulator after tuning.To be demodulator adjust the yield value of tuner automatically according to the intensity of the i/q signal of tuner output for automatic gain control, in the hope of reaching the reception of the best.Generally speaking automatic gain is big more, and expression received signal intensity is weak more.Otherwise represent that then signal is strong more.In the present invention, for convenience of calculation, we have done anti-phase processing with the automatic gain value.Be that the strong more automatic gain value of signal is big more, the weak more automatic gain value of signal is more little.
Computing of the present invention is carried out (with reference to figure 1) by the microprocessor in the system.Usually it has the dynamic and static memory of oneself, and by bus or other interfaces control demodulator.Demodulator is according to the requirement control tuner work of microprocessor.Microprocessor can read the register in demodulator and the tuner by the interface that links to each other with demodulator, monitors their operating state.Automatic gain control value for example, information such as lock-out state can obtain by the method for read register.
Fig. 3 is the blind flow chart of sweeping method of prior art.Blind principle of sweeping is that control satellite digital television receiver set top box front end scans the parameters that obtains satellite repeater.Can be as seen from the figure, the common blind method of sweeping is all carried out symbol rate scanning to each Frequency point, and having wasted a large amount of time is not like this having on the Frequency point of signal, very slow of speed.Run-down approximately takes 3 days time.
The used hardware of the invention process is identical with system shown in Figure 1, to hardware without any specific (special) requirements, hardware cost increased to zero.Its cardinal principle is: rejected most Frequency points that does not have signal by frequency scanning and series of computation, processing, only carried out the scanning of symbol rate at some limited Frequency points, shortened the time of scanning greatly.
In addition, satellite repeater generally uses two polarised direction-levels with vertical, so the present invention only discusses a polarised direction is carried out blind sweeping, and the scanning process of another polarised direction is identical.
The main flow process of method of the present invention is divided into the two large divisions, and a part is a frequency scanning, the scanning of another part is-symbol rate.Fig. 4 shows the blind main-process stream block diagram of sweeping, and it has described blind whole flow process of sweeping:
At first, carry out the blind initialization of sweeping.
Secondly, carry out frequency scanning,, calculate good frequency range interscan in advance, obtain automatic gain control (AGC) value of each Frequency point with certain frequency interval promptly by the control tuner.
Then,, analyze its correlation, find several more intense Frequency points of energy as Candidate Frequency by processing and calculating to these values.The precision of frequency scanning is very crucial for improving sweep speed, and precision is high more, and then Candidate Frequency is few more, and the frequency of missing is also few more, and the Candidate Frequency that need carry out symbol rate scanning is also few more.By the frequency that will carry out symbol rate scanning is screened, the precision of frequency scanning of the present invention is higher than additive method far away.
At last, carry out symbol rate scanning,, then store this Frequency point and symbol rate if can lock a symbol rate at each Candidate Frequency point; Otherwise, think that this Candidate Frequency point is invalid.When symbol rate scans, except according to prior art to 450 symbol rates of each Candidate Frequency spot scan, also can pass through a series of optimization method, improve scan efficiency, shorten sweep time.
In the frequency scanning flow process, preferably use different scanning strips according to the difference of satellite band.According to the difference of satellite band, we can use different sweep bandwidths.For the satellite of C-band, its transponder frequency scope is from 3,400MHz to 4,200MHz.The bandwidth that we should scan should be to (LNB centre frequency-3400) from (LNB centre frequency-4200).With the LNB centre frequency is that 5150MHz is an example, and the bandwidth that should scan is to (5150-3400)=1550MHz from (5150-4200)=950MHz.For the Ku wave band, the transponder frequency scope has exceeded the frequency coverage of tuner, thereby should carry out full frequency band scanning, promptly from 950MHz to 2150MHz.Like this, just can farthest dwindle sweep limits, reduce sweep time.
In the frequency scanning flow process, preferably each Frequency point is carried out deburring and handle.Fig. 7 shows the principle of deburring: the AGC value of adding up 2 frequencies about each Frequency point; If the AGC value of two points in its left side and two points in the right all equates, and the AGC value of this point itself is than their a big unit, and a perhaps little unit thinks that then this is put is burr; Its AGC value substitutes with the AGC value of left and right sides consecutive points.Like this, just can remove the little burr of finding in the scanning process, reduce the burr erroneous judgement is the possibility of Candidate Frequency.
When the frequency of scanning is screened, a screening technique is: if the resulting AGC value of any one frequency is less than a thresholding, this frequency then is rejected not as considering so, otherwise, as Candidate Frequency, wherein this thresholding multiply by a coefficient for the spectrum averaging energy, and wherein this coefficient is slightly larger than 1 usually.The spectrum averaging energy is the geometrical mean of each frequency AGC value, promptly
Because all normalization is to positive for the AGC value of all frequencies, for fear of the complex calculation of sqrt, we can directly take the square value of average energy.Like this, just can filter out the very low Frequency point of the energy value that scans to reach the purpose that shortens sweep time.
When the frequency of scanning was screened, another screening technique was:
At first, go weighted average to handle, obtain the weighted average (AVG) of each frequency AGC for the AGC value of each frequency.Fig. 8 shows weighted average method.The principle of this method is, to each Frequency point and about the AGC value of each n Frequency point be weighted average computation.Say it for example: n=2 has represented at 5 on average.If the weights that we adopt are W1, W2, W3, W4, W5, J calculates for Frequency point, and its weighted average AGC value AVG then is AVG (J)=(W1*AGC (J-2)+W2*AGC (J-1)+W3*AGC (J)+W4*AGC (J+1)+W5*AGC (J+2))/5.Like this, pass through weighted average method and done substantial low pass filtering for the curve of AGC and obtained the AVG curve, on the AVG curve, done the judgement of Candidate Frequency again, can reduce to falsely drop the possibility of frequency.
Secondly, check the AVG value change direction of each Frequency point, if the change direction of AVG value becomes smooth by rising or decline, this Frequency point will be used as initial Candidate Frequency point.This Candidate Frequency point of finding out is more, most erroneous judgement Candidate Frequency can be rejected in the method for back.
Then, at this Candidate Frequency, calculate three dB bandwidth and/or breakover point bandwidth.As shown in Figure 9, three dB bandwidth is the AVG value according to each Candidate Frequency, seeks the Frequency point of energy than the low 3dB of Candidate Frequency left and to the right respectively, and the difference on the frequency of the energy Frequency point of these two low 3dB is exactly the three dB bandwidth of Candidate Frequency; The breakover point bandwidth is in the process that the searching 3dB that turns left or turn right is ordered, when appearance AVG value curve becomes rising by decline, the AVG value that at first finds breakover point higher in the breakover point of the left and right sides is as the bandwidth measurement energy point, calculates then at energy at the difference on the frequency of the left and right sides of this some Frequency point as the breakover point bandwidth.This 3dB is estimated that by the fall of AVG value curve concrete value should be according to the actual test result decision of front end.By the bandwidth of calculated candidate frequency, can dwindle the scope of symbol rate search, shorten search time.
Then, as shown in figure 10, be the centre frequency of Candidate Frequency with the frequency intermediate value of left and right sides 3dB or breakover point.Because the peak value searching method that we adopt can only find AVG value curve to become point smooth and that descend by rising, than under the condition with higher, the frequency of this point may be a lot of less than actual transponder frequency in the transponder symbol rate.The centre frequency of calculating like this can be very approaching with actual transponder frequency.
At last, be far smaller than the AVG value of contiguous blocked Candidate Frequency if find the AVG value of certain Candidate Frequency, think that so this Candidate Frequency is invalid, the critical parameter here need be according to measuring decision.The principle of making is like this, and through adding up and discovering, the energy value of the different transponders of same satellite changes can be very not greatly.Like this, just can filter the less erroneous judgement Candidate Frequency of energy.
Fig. 5 shows an embodiment of frequency scanning.It is divided into following steps:
(1) carries out frequency scanning,, calculate good frequency range interscan in advance, obtain the AGC value of each Frequency point with certain frequency interval promptly by the control tuner.
(2) the AGC value of each Frequency point being carried out deburring handles.
(3) calculate the AGC weighted average AVG of each Frequency point.
(4) average energy of calculating whole frequency.
(5) judge the change direction of each Frequency point AVG value, if become decline or smooth by rising, then default this Frequency point is Candidate Frequency and computation bandwidth and centre frequency; Otherwise give up this Frequency point.
(6) if a centre frequency and a last Candidate Frequency difference are too little, abandon this Candidate Frequency.If a centre frequency and a last Candidate Frequency difference think then that less than 4MHz both differ too little.
(7) if this Candidate Frequency AGC less than the band energy threshold, abandons this Candidate Frequency.The frequency range average energy that is defined as this energy threshold multiply by one and is a bit larger tham 1 coefficient.
General through obtaining to be no more than 100 Candidate Frequency points after the above-mentioned steps, wherein the number of Candidate Frequency point is main relevant with the number of digital satellite signal channel.Then, these Candidate Frequency points are carried out symbol rate scanning.
The principle of symbol rate scanning is selectively to set the symbol rate of front end, and attempts locking.After waiting for the regular hour, if if successfully locking then obtain the symbol rate of this frequency overtime then attempt the next symbol rate of selecting, only to finding out the symbol rate that can lock, has perhaps been attempted till all symbol rates of selecting.The length of symbol rate sweep time is related to the length of whole sweep time too.Reasonably select symbol rate and stand-by period, can find the symbol rate of Candidate Frequency with the fastest speed or get rid of Candidate Frequency.
In symbol rate scanning flow process, the sweep limits of symbol rate preferably sets: if the turnover bandwidth of Candidate Frequency is lower than 4MHz, its bandwidth will be set as 4MHz; If Candidate Frequency has three dB bandwidth and breakover point bandwidth simultaneously, the sweep limits of symbol rate will be from
To breakover point bandwidth * 2.5 Hes
To three dB bandwidth * 2; If Candidate Frequency has only three dB bandwidth, the sweep limits of symbol rate will be from
To three dB bandwidth * 2.The scope that like this, just can reduce symbol rate scanning as far as possible is with raising speed.
In symbol rate scanning flow process, preferably at first attempt the symbol rate that a success locks.This is because find that through statistics on same satellite, the probability that the symbol rate of adjacent transponder is identical is very high.Like this, can reduce the scanning of symbol rate.
In symbol rate scanning flow process, preferred front end needed stand-by period of transponder signal of locking is A-symbol rate * B, A wherein, and B is constant.According to this formula, the time that high more symbol rate is waited for is short more.This method can shorten the stand-by period when symbol rate is higher, at low time delay high latency, reduce to miss the possibility of symbol rate.
In symbol rate scanning flow process, the ordering of the symbol rate of being swept is preferably by the high more symbol rate of frequency of utilization to the low more symbol rate of frequency of utilization.Can shorten the total time of symbol rate scanning like this.
Fig. 6 shows an embodiment of symbol rate scanning.It is divided into following steps:
(1) obtains a frequency and polarised direction from the Candidate Frequency kind; If this Candidate Frequency drops in the effective bandwidth of a locking frequency, then give up this frequency; Set polarised direction; If this Candidate Frequency drops on outside the effective range, then give up this frequency; Scope according to the scanning of Candidate Frequency bandwidth constraints symbol rate.
(2) symbol rate of the last successful locking frequency of scanning.
(3) calculate parameters and stand-by period.
(4) examination scanning.
(5) if wait timeout carries out next symbol rate scanning; Otherwise, this symbol rate is locked.
(6), carry out the symbol rate scanning of next step frequency then, until the end of scan if this Candidate Frequency and symbol rate are preserved in locking.
In the general above-mentioned symbol rate scanning, the symbol rate scanning number of each Candidate Frequency point is no more than 100.
Use the blind blind function of sweeping that can on the platform of microprocessor, finish high speed of sweeping method of the present invention, exempted the realization of special hardware, thereby reduced cost for the satellite repeater TV programme in the mode of software.The precision of frequency scanning is very crucial for improving sweep speed, and precision is high more, and then Candidate Frequency is few more, and the frequency of missing is also few more, and the Candidate Frequency that need carry out symbol rate scanning is also few more.The precision of frequency scanning method of the present invention is higher than additive method far away, can shorten blind sweeping the used time greatly.In the scanning of symbol rate, the present invention also by a series of optimization method, has improved scan efficiency, also shortens sweep time.According to result of the test, it approximately is about 10 minutes that the present invention finishes the whole blind time of sweeping.Precision has has all met or exceeded by hard-wired blind degree of sweeping.
Should be appreciated that the present invention is not limited to the blind of satellite repeater TV programme and sweeps, it also can be applicable to the blind of other satellite digital signal and sweeps.
Claims (9)
1. the blind method of sweeping of a digital terrestial television channels is used to search for the digital signal that receives satellite repeater, it is characterized in that: may further comprise the steps:
(a) front end system of received RF carries out the blind initialization of sweeping, and wherein the front end system of received RF comprises tuner and demodulator;
(b) by the control tuner, calculate good frequency range interscan with certain frequency interval in advance, obtain the automatic gain control value of each Frequency point;
(c) by to the going weighted average to handle, calculate the breakover point bandwidth of these values, find the weighted average curve to become smooth by rising or the point that descends as Candidate Frequency;
(d) carry out symbol rate scanning at each Candidate Frequency point,, then store this Frequency point and symbol rate if can lock a symbol rate; Otherwise, think that this Candidate Frequency point is invalid.
2. the blind method of sweeping as claimed in claim 1 is characterized in that: the difference according to satellite band in the step (b) is used different sweep bandwidths, and promptly for the C-band satellite, sweep bandwidth is that LNB centre frequency-4200MHz is to LNB centre frequency-3400MHz; For the Ku band satellite, sweep bandwidth is that 950MHz is to 2150MHz.
3. the blind method of sweeping as claimed in claim 1 or 2, it is characterized in that: the method for seeking Candidate Frequency in the step (c) is, if the resulting automatic gain control value of any one frequency is less than a thresholding, this frequency then is not rejected and considers as Candidate Frequency so, otherwise, described frequency is as Candidate Frequency, and wherein this thresholding multiply by a coefficient for the geometrical mean of each frequency automatic gain control value, and wherein this coefficient is slightly larger than 1.
4. the blind method of sweeping as claimed in claim 3, it is characterized in that: the automatic gain control value of described automatic gain control value for handling through deburring, promptly add up the automatic gain control value of 2 frequencies about each Frequency point, if the automatic gain control value of two points in its left side and two points in the right all equates, and the automatic gain control value of this point itself is than their a big unit, a perhaps little unit, think that then this point is burr, its automatic gain control value substitutes with the automatic gain control value of left and right sides consecutive points.
5. the blind method of sweeping as claimed in claim 3, it is characterized in that: the automatic gain control value of described automatic gain control value for handling through weighted average, promptly the automatic gain control value for each frequency goes weighted average to handle, and obtains the weighted average of each frequency automatic gain control value.
6. the blind method of sweeping as claimed in claim 1 or 2 is characterized in that: the method for seeking Candidate Frequency in the step (c) is:
At first, go weighted average to handle, obtain the weighted average of each frequency automatic gain control for the automatic gain control value of each frequency;
Secondly, check the weighted average change direction of each Frequency point, if the change direction of weighted average becomes smooth by rising or decline, this Frequency point will be used as initial Candidate Frequency point;
Then, at this Candidate Frequency, calculate three dB bandwidth and/or breakover point bandwidth, wherein, three dB bandwidth is the weighted average according to each Candidate Frequency, seek the Frequency point of energy than the low 3dB of Candidate Frequency left and to the right respectively, the difference on the frequency of the energy Frequency point of these two low 3dB is exactly the three dB bandwidth of Candidate Frequency; The breakover point bandwidth is in the process that the searching 3dB that turns left or turn right is ordered, when appearance weighted average curve becomes rising by decline, the weighted average that at first finds breakover point higher in the breakover point of the left and right sides is as the bandwidth measurement energy point, calculates difference on the frequency at the left and right sides of this some Frequency point then as the breakover point bandwidth;
Then, be the centre frequency of Candidate Frequency with the frequency intermediate value of left and right sides 3dB or breakover point, if this centre frequency and a last Candidate Frequency differ less than predetermined value, then abandon this Candidate Frequency;
At last, be far smaller than the weighted average of contiguous blocked Candidate Frequency, think that so this Candidate Frequency is invalid if find the weighted average of certain Candidate Frequency.
7. the blind method of sweeping as claimed in claim 6 is characterized in that: in the step (d) each Candidate Frequency point is carried out symbol rate when scanning, the sweep limits of symbol rate is to set like this:
If the turnover bandwidth of Candidate Frequency is lower than 4MHz, its bandwidth will be set as 4MHz;
If Candidate Frequency has three dB bandwidth and breakover point bandwidth simultaneously, the sweep limits of symbol rate will be
If Candidate Frequency has only three dB bandwidth, the sweep limits of symbol rate will be
8. the blind method of sweeping as claimed in claim 1 is characterized in that: during to each symbol rate scanning beginning, at first attempt the symbol rate that successfully locked last time in the step (d).
9. as claim 1 or the 8 described blind methods of sweeping, the ordering of the symbol rate of being swept for by the high more symbol rate of frequency of utilization to the low more symbol rate of frequency of utilization.
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| CN102236055B (en) * | 2010-04-30 | 2015-11-25 | 东莞华仪仪表科技有限公司 | Automatic frequency selection method |
| CN102572340B (en) * | 2012-02-09 | 2016-06-01 | 青岛海信电器股份有限公司 | Digital satellite television channel search method and digital satellite television machine |
| CN102724088B (en) * | 2012-05-25 | 2015-12-16 | 华为终端有限公司 | Downlink channel locking means, device and cable modem loading method, device |
| CN103458201B (en) * | 2012-06-05 | 2017-02-22 | 晨星软件研发(深圳)有限公司 | Signal processing device and signal processing method |
| GB201317461D0 (en) * | 2013-10-02 | 2013-11-13 | Imagination Tech Ltd | Satellite scanning |
| CN105959779A (en) * | 2016-06-16 | 2016-09-21 | 珠海迈科智能科技股份有限公司 | Method and device for updating satellite frequency points in set top box |
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| JPH1169415A (en) * | 1997-05-22 | 1999-03-09 | Casio Comput Co Ltd | Receiving device and receiving channel setting method |
| JPH11313261A (en) * | 1998-04-28 | 1999-11-09 | Hitachi Ltd | Receiving device receiving method |
| CN1413031A (en) * | 2001-10-15 | 2003-04-23 | 汤姆森许可贸易公司 | Method for testing transmission channel and receiver using said method |
| JP2003179824A (en) * | 2001-12-12 | 2003-06-27 | Sanyo Electric Co Ltd | Automatic channel scanning system |
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- 2004-11-23 CN CNB2004100916014A patent/CN100459667C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1169415A (en) * | 1997-05-22 | 1999-03-09 | Casio Comput Co Ltd | Receiving device and receiving channel setting method |
| JPH11313261A (en) * | 1998-04-28 | 1999-11-09 | Hitachi Ltd | Receiving device receiving method |
| CN1413031A (en) * | 2001-10-15 | 2003-04-23 | 汤姆森许可贸易公司 | Method for testing transmission channel and receiver using said method |
| JP2003179824A (en) * | 2001-12-12 | 2003-06-27 | Sanyo Electric Co Ltd | Automatic channel scanning system |
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| CN1780376A (en) | 2006-05-31 |
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