CN101917375B - Method for adding audio frequency signaling in broadcast system - Google Patents
Method for adding audio frequency signaling in broadcast system Download PDFInfo
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Abstract
The invention provides a method for calculating and adjusting synchronous audio delay in a synchronized frequency modulation broadcast system. The method is characterized in that: an audio front end server of the system executes the following steps of: communicating with a human-machine interface module to obtain the user data of an application layer of the digital frequency modulation synchronized broadcast system; selecting a data frame format needing to be sent by way of polling, sending synchronous frames and non-synchronous frames in turn and sending a synchronous frame per second; framing data from the application layer to a data link layer; carrying out FSK (Frequency Shift Keying) modulation on the data of the data link layer; receiving a digital audio signal form the audio input end, carrying out low filtering, then adding the digital audio signal with the FSK waveform modulated by the channel associated audio signaling, and outputting to a next-stage device via a digital or analogue audio interface after CODEC D/A conversion.
Description
Technical field
The present invention relates to the synchronous frequency-modulating broadcast systems technology, particularly a kind of system and method that solves frequency-shift keying synchronized broadcasting system audio time-delay adjustment problem.
Background technology
Synchronous frequency-modulating broadcast refer to utilize two ones of being positioned at the different location or more the multi-section transmitter use same frequency to broadcast the forms of broadcasting of same programme content.The establishment of synchronous frequency-modulating broadcast network can well solve uses single-frequency to carry out the problem of large tracts of land FM broadcasting.
The advantage of synchronous frequency-modulating broadcast shows following two aspects.At first, because the coverage mode that synchronous frequency-modulating broadcast adopts small-power to layout as required can reduce electromagnetic pollution, for saving operating cost in the radio station.The characteristics that its single-frequency of while covers, compare with the poor coverage mode that turns of traditional FM broadcasting, not only can save a large amount of frequency spectrum resources, and need not frequently to adjust the receiver frequency, for increasing mobile reception audience (such as the driver), bring great convenience.
Realize synchronous frequency-modulating broadcast, if just simply utilize a plurality of radio station that are distributed in diverse location, use same carrier frequency, it is impracticable broadcasting same program.As shown in Figure 1, transmitter A and transmitter B use same carrier frequency to broadcast same program, and in transmitter A and the independent zone that covers of transmitter B, because the capture effect of FM receiver, the audibility of frequency modulation programme is fine.But at the poor coherence area less than 15 dB of signal strength from A, two transmitting stations of B, because co-channel interference generally can be heard more serious back drop.
Synchronous frequency-modulating broadcast key issue to be solved will guarantee the listening quality of this coherence area exactly.Concrete solution is exactly the realization (according to GY/T154-2000) of " three same guarantors "." three together " refers to frequency, homophase, same modulation." one protects " refers to guarantee minimum usbale field strength.The homophase here is to guarantee that the audio signal phase that adjacent 2 transmitting stations that receiver receives launch is identical, that is to say that audio signal will have identical audio delay in transmission course.The scope that the realization one of " three same guarantors " can be dwindled coherence area is reduced to the poor overlapping region less than 6dB of field intensity from the poor overlapping region less than 15dB of field intensity, and two can reduce the distortion of coherence area, obviously improve the audibility of coherence area.
In order to guarantee the same audio delay in " three together ", must carry out the Adaptive Time Delay adjustment to the audio signal that exciter receives.Because with audio signal from the broadcast control centre in radio station in the middle of the transmission course of each transmitting station exciter (exciter A as shown in Figure 2 and exciter B), not only can be owing to A, B two places produce fixing audio frequency delay inequality from the audio signal of different each exciters of distance of broadcasting centre, and the variation of audio transmission link route, the variation of clock, the uncertain variation that the factors such as multiplexing and demultiplexing of signal in transmission course all can be brought the audio frequency time delay.Guarantee same audio delay, must be able to automatically measure, this uncertain variation of auto-compensation.Concrete way is, transmits a timing signal in the transmission broadcast singal, and both are simultaneously transmission in same channel, has identical audio frequency time delay.Exciter just can carry out corresponding time delay adjustment according to the time delay of the timing signal that measures like this.
But, with road audio frequency timing signal adding, separation and synchronizing process, be a more scabrous problem always, can not affect the audio signal quality of synchronous frequency-modulating broadcast system transmissions, the system that also will guarantee can be synchronous exactly.
Summary of the invention
In order to solve frequency-shift keying synchronized broadcasting system with the audio frequency delay problem, the 1PPS pps pulse per second signal that GPS is provided is as timing signal, mode frequency division multiplexing by the FSK modulation transmits in channel, the invention provides adding and an extracting method with the road voice-frequency signaling.Described technical scheme is as follows:
A kind of method that solves synchronous frequency-modulating broadcast system synchronization audio frequency time-delay calculation and adjustment is characterized in that, the audio front end server of described system is carried out following steps:
Steps A: communicate with human-machine interface module, obtain frequency-shift keying synchronized broadcasting system applies layer user data;
Step B: adopt the mode of poll to select the data picture format that will send, synchronization frame and Non-alignment Frame send in turn, and per second only sends a synchronization frame;
Step C: from application layer until the data framing of data link layer;
Step D: the data of data link layer are carried out the FSK modulation;
Step e: receive digital audio and video signals from audio input end, after low-pass filtering, and with the FSK waveform adder after the modulation of road voice-frequency signaling, after CODEC D/A conversion, export to rear class equipment by numeral or analog audio interface.
Preferably, the data picture format that described system audio front-end server sends comprises synchronization frame, site information frame and command frame, synchronization frame comprises the time delay reference point as timing signal, the site information frame provides parameter control for each exciter, and command frame then can carry out concentrated setting to the parameter of all exciters in the whole network.
Preferably, the frame head of described synchronization frame aligns with the pps pulse per second signal that GPS provides.
Preferably, the frame head of described synchronization frame and Frame carry out respectively CRC check.
Preferably, for the FSK modulation of data in link layer, adopting tables look-up adds the method for keying.
A kind of method that solves synchronous frequency-modulating broadcast system synchronization audio frequency time-delay calculation and adjustment is characterized in that, the Digit FM Exciter of described system is carried out following steps:
Steps A: the digital audio and video signals that receives is carried out low-pass filtering, for the exciter coded modulation; The digital audio and video signals that receives is carried out high-pass filtering, obtain the FSK modulated wave of signaling;
The correlation detection principle of step B:FSK is to carry out demodulation by the square-law maximum of relatively correlator output.The FSK modulated wave that obtains and in-phase component and the quadrature component of frame head data are carried out related calculation respectively, obtain two groups of correlation computations results, square operation is done in two class value pointwises, and the result is carried out addition, preserve operation result.Simultaneously ask for maximum in the result, the maximum corresponding points that find within a frame period are the frame synchronization point, thereby recover the accurate sampled point relative position relation of whole transmission frame, realize sampled point synchronously, bit synchronization and frame synchronization.
Step C: the signaling data that obtains is carried out CRC check and frame parsing, obtain correct network management information, and calculate the audio frequency time delay in conjunction with the 1PPS standard timing signal of GPS.
Preferably, among the step B, utilize modulated wave and frame head to carry out related operation and realize that frame head is synchronous, and realize that sampled point is synchronous.
Preferably, the system clock of transmitting-receiving two-end is all phase-locked with the 10MHz benchmark frequency marking that GPS provides; At set intervals, the original position of demodulation is finely tuned.
The beneficial effect that technical scheme of the present invention is brought is:
Transmit in the frequency division multiplexing mode with the road voice-frequency signaling by provided by the invention, receiving terminal only needs high-pass filtering and carries out the FSK demodulation that just can to obtain transmitting terminal added with the road voice-frequency signaling, this adding method with the road voice-frequency signaling is applicable to the audio transmission system that any transmission bandwidth is 20KHZ, has the most widely applicability, and this method need not to add any optional equipment, brings great convenience for the user in the actual sets network process.
Description of drawings
Fig. 1 is synchronous frequency-modulating broadcast schematic diagram of the present invention;
Fig. 2 is synchronous frequency-modulating broadcast of the present invention system at the synchronous lower schematic diagram of calculating the audio frequency time delay of GPS standard timing signal;
Fig. 3 is the time division multiplexing schematic diagram with road voice-frequency signaling and audio signal;
Fig. 4 is time-multiplexed with road voice-frequency signaling transmission plan schematic diagram;
Fig. 5 is the frequency division multiplexing schematic diagram with road voice-frequency signaling and audio signal;
Fig. 6 is the architecture with road voice-frequency signaling transmission system layering of frequency division multiplexing;
Fig. 7 is the concrete formation with road each layering of voice-frequency signaling transmission system of frequency division multiplexing;
Fig. 8 is the transmission sequence of various function frames;
Fig. 9 is the structured flowchart of hardware platform;
Figure 10 is the software function module schematic diagram of transmitting terminal;
Figure 11 is CRC check fast algorithm flow chart;
Figure 12 is that the FSK modulation module is realized block diagram;
Figure 13 is the software function module schematic diagram of receiving terminal;
Figure 14 be adopt relevant and the square-law decision device finish sampled point synchronously, the frame synchronization schematic diagram;
Figure 15 is that data demodulates is processed block diagram;
Embodiment
The invention will be further described below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.
In the synchronous frequency-modulating broadcast of the present invention, the 1PPS pps pulse per second signal that GPS is provided is as timing signal, transmits in channel with audio stream is multiplexing together.As shown in Figure 2, at transmitting terminal, the pps pulse per second signal that the audio front end server provides GPS is as joining in the audio stream with the road voice-frequency signaling.At receiving terminal, exciter will extract with the road voice-frequency signaling, and timing signal that will be wherein compares with local GPS pulse per second (PPS), just can obtain audio frequency time delay that transmission course causes.In addition, with the down management information that can also comprise network in the voice-frequency signaling of road, can realize like this Long-distance Control to each exciter, for the management of whole network provides very large convenience.
From broadcasting control centre to the transmission of each emission station FM exciter, the ad-hoc networks that can be utilized as synchronous frequency-modulating broadcast provides realizes for audio signal noted earlier.These ad-hoc networks can be the PDH/SDH networks of fiber optic network, microwave network or telecommunications.But to have a general shortcoming be exactly the construction cost costliness to this special network, is difficult to promote.
So wish to use at present very ripe DVB transmission link.The satellite transmission link of DVB at first, at present, the Digital Television that each overwhelming majority of central, and province level TV station has had the DVB-S program of broadcasting TV programs by satellite.And one road satellite television programming can also attach six road audio frequency except the television field frame that comprises program itself.Can be the audio signal that will transmit as the transmission that is combined with each other of one tunnel supplemental audio and TV programme.Owing to need not to ward off in addition separately channel, so there is not extra channel occupancy expense.In addition, the satellite broadcasting wide coverage is suitable for the establishment of large tracts of land synchronous frequency-modulating broadcast network.And satellite broadcasting is not limited by geographical conditions, and some geographical conditions is abominable, is unsuitable for the place that Wireline is laid, and can receive the signal of satellite transmission yet.The popularity rate of cable TV network in the city of DVB system is quite high at present, and the audio transmission scheme of via satellite link realization almost can be transplanted to cable TV network fully.These all make the DVB transmission link become the first-selection of setting up synchronous frequency-modulating broadcast network.But, no matter be dedicated network, or the DVB network, all may bring the uncertain variation of audio frequency time delay, so no matter adopt any transmission means, all need to carry out the time delay adjustment.
For DVB transmission link the most frequently used in the synchronous frequency-modulating broadcast network, adding method with the road voice-frequency signaling has been done following consideration: some the MPEG-2 encoder that uses in the DVB system is at present only supported the analogue audio frequency input, and the network provider does not generally allow existing equipment is changed, so need and with the joining in the analog audio stream with the road voice-frequency signaling of timing signal, in transmission course, to remain identical time delay to guarantee both.The method that adds is exactly first to the modulating with the road voice-frequency signaling of digital form, and is again that modulation signal and analogue audio frequency is together multiplexing.Since lower with road voice-frequency signaling data transfer rate, and consider that the modulation and demodulation of FSK are simpler, so present embodiment has adopted the modulation system of FSK.
With the multiplex mode of the modulation waveform of road voice-frequency signaling and analogue audio frequency two kinds of time division multiplexing and frequency division multiplexings can be arranged.
Time division multiplexing at first is shown in accompanying drawing 3 and 4.At first, the audio stream of inputting is passed through sample rate conversion, in time domain it is compressed, come command transmitting to reserve time slot.During reception, with higher sample rate composite signal is received first, again it is separated.In the process of separating, the rotary switch of transmitting-receiving two-end must be opened simultaneously or be closed, if error appears in this synchronizing process, signaling will be sneaked in the audio signal, to the serious interference of mass formation of the audio signal broadcasted.In the implementation procedure of reality, because the pseudo-signaling of very possible appearance in the signal, so this strict being difficult to synchronously guarantees that this allows to occur anything but, so do not adopt this multiplex mode in this preferred embodiment in the equipment of broadcast level.
Then see again frequency division multiplexing, as shown in Figure 5.Because the frequency spectrum of most of audio signal all concentrates on below the 15KHz, so the thought of frequency division multiplexing is exactly will be high-end with the frequency spectrum that the road voice-frequency signaling is modulated to more than the audio signal 15KHz by the FSK modulation.Like this, at receiving terminal, only need a simple low pass filter just can the filtering signaling on the impact of audio signal, can not affect the audio signal quality of broadcast.And the system that it is 20KHz that this multiplex mode is applicable to any audio transmission bandwidth has widely versatility.Therefore, present embodiment has selected the mode of frequency division multiplexing to realize multiplexing with road voice-frequency signaling and analogue audio frequency.
According to the analysis of front as can be known in the synchronous frequency-modulating broadcast the most frequently used audio transmission mode be the transmission link of DVB.In this transmission link, need to use the MPEG-2 encoder.The use meeting of this MPEG-2 encoder exerts an influence to the transmission with the road voice-frequency signaling of frequency division multiplexing.Because the coding standard of MPEG-2 takes full advantage of the psychologic acoustics characteristic of people's ear audio signal has been carried out lossy compression method.And people's ear is insensitive to the radio-frequency component in the audio frequency, so if high frequency range component is too little or by temporal masking or masking spectrum, encoder just can not be to its transmission of encoding.Because when adopting frequency division multiplexing, the frequency spectrum that has been modulated onto audio signal with the road voice-frequency signaling is high-end, so through behind the MPEG-2 encoder, the phenomenon that certain period do not encode and transmit signaling probably occurs.
For the characteristic of MPEG-2 encoder, present embodiment has carried out prudent selection to the transformation parameter with the road voice-frequency signaling.Here, the modulating frequency of FSK is selected lower frequency as far as possible, such as 17KHz and 18KHz.The modulation amplitude of FSK requires moderate, and what present embodiment was selected is-24dBFS.The duration of FSK modulation symbol has been selected 1ms.Duration is shorter, like this, when owing to the MPEG-2 coding a certain section FSK modulation waveform being lost, just can find as early as possible a new frame complete signal, re-starts correct demodulation.Because the data transfer rate of signaling is lower, so missing data can be remedied by the retransmission data of back, the audio frequency time delay does not need per second all to go to adjust yet, so can not affect the performance of signaling.In addition, at transmitting terminal, also audio signal has been carried out the low-pass filtering of 15KHz, to reduce audio signal to the interference of signaling.In the frame structure of design, also added CRC check, detect the demodulation error code that may exist.
The application has designed the architecture with road voice-frequency signaling transmission system layering of frequency division multiplexing.Mainly comprising four layers, is respectively physical layer, data link layer, transport layer and application layer.The corresponding relation of the architecture of native system and ISO/OSI and TCP/IP as shown in Figure 6.
System adopts the architecture of layering, can bring two benefits: the one, and, the layering abstract according to different qualities realizes a clear and definite function for every layer, can avoid each layer function chaotic.The 2nd,, each layer is relatively independent, thereby so that is assigned to the task of each layer and can independently realizes.Like this, when certain solution that provides when one deck is wherein upgraded, can not affect other layer.
The concrete formation of each layer as shown in Figure 7.
Three kinds of function frames have been defined with the road voice-frequency signaling: synchronization frame, site information frame and command frame.Synchronization frame comprises the time delay reference point as timing signal, and the site information frame provides parameter control for each exciter, and command frame then can carry out concentrated setting to the parameter of all exciters in the whole network.During transmission, synchronization frame and Non-alignment Frame send in turn, and per second only sends a synchronization frame.The frame head of synchronization frame aligns with the pps pulse per second signal that GPS provides, as shown in Figure 8.
Signaling transmission system is to realize on the common treatment hardware platform of a base-band audio signal.This hardware platform comprises seven modules as shown in Figure 9: human-machine interface module, digital audio transceiver module, analogue audio frequency CODEC module, FPGA and CPLD module, DSP module, power module and clock module.
Wherein, analogue audio frequency CODEC module and digital audio transceiver module are the input/output modules of this platform.Simulation or the audio signal of digital form are sent in the rear class module by these two modules and to be processed; Voice data output after perhaps system can will process by these two modules is for next stage equipment.
The DSP module is the core of whole hardware platform, and nearly all signal processing function is all finished in this module.
FPGA and CPLD module are used for providing the transmission of signal and the buffer memory of data for above-mentioned several modules.The part signal processing capacity also realizes in this module.
Human-machine interface module provides the interface of an interchange for human-computer dialogue.Power supply and clock module then are the essential conditions of whole normal operation circuit.
Transmitting terminal, audio front end server namely, the function that realize has the following aspects:
(1) with the single chip communication of controlling liquid crystal panel and serial ports of computers, obtains system applies layer user data;
(2) adopt the mode of poll to select the data picture format that will send;
(3) from application layer until the data framing of data link layer;
(4) data of data link layer are carried out the FSK modulation;
(5) receive digital audio and video signals from input, after the 15KHZ low-pass filtering, and with the FSK waveform adder after the modulation of road voice-frequency signaling, after CODEC D/A conversion, export to rear class equipment by analog audio interface.
The software function module schematic diagram of transmitting terminal as shown in figure 10.
For CRC check, DSP has adopted a kind of quick CRC check algorithm by byte calculating based on tabling look-up.The thinking of this algorithm of tabling look-up is the residue coding schedule of a byte information of first off-line structure, tables look-up and XOR can be tried to achieve the CRC residue of multibyte information according to this coding schedule.Because byte information is totally 8 binary elements, so always have 256 kinds of various combinations.With the generator polynomial G (x) of most widely used CCITT suggestion=x
16+ x
12+ x
5+ 1 is example, and every kind of combination removes through generator polynomial G (x), just produces the check value of two bytes, so byte residue coding schedule accounts for 256 words (512 bytes) altogether.
CRC check fast algorithm flow chart as shown in figure 11.
For the FSK modulation of data in link layer, adopting tables look-up adds the method for keying.This method has three advantages: (1) speed fast (2) can guarantee phase place, and (3) realization is simple continuously.Its algorithm schematic diagram as shown in figure 12.
The receiving terminal of system, Digit FM Exciter end namely, the function that finish mainly contains the following aspects:
(1) digital audio and video signals that receives is carried out the 15KHZ low-pass filtering, for the exciter coded modulation.
(2) digital audio and video signals that receives is carried out the 15KHZ high-pass filtering, obtain the FSK modulated wave of signaling.
(3) FSK modulated wave and the frame head that obtains carried out related operation, to simplify the demodulation of FSK.
(4) signaling data that obtains is carried out CRC check and frame parsing, obtain correct network management information, and calculate the audio frequency time delay in conjunction with the 1PPS standard timing signal of GPS.
The software function module schematic diagram of receiving terminal as shown in figure 13.
The design of filter
In native system, all adopt digital filter in DSP, to realize filtering to digital signal.Digital filter mainly is divided into two classes: finite impulse response (FIR) filter and infinite impulse response (IIR) filter.The FIR filter has the impulse response of a finite length, is the filter with ideal linearity phase place and constant group delay.Now the summary of benefits with the FIR filter is as follows:
● desirable linear phase response can be provided.
● can adopt foolproof algorithm to realize.
● reduced algorithm to limited arithmetic precision and the sensitivity of rounding error.
● guaranteed stability.
The ideal linearity phase place of FIR filter refers to that the phase response of filter is with frequency linearity decay (being that the speed that phase place changes is constant).The constant group delay is used the value that particular importance is arranged to the application of ask for something preservation signal waveform shape such as the audio or video of high speed data transfer or high-fidelity.We are based upon on this point basis especially to the reckoning of audio frequency time delay, so the design of filter here all adopts Finite Impulse Response filter to realize.
The THE DESIGN OF WINDOW FUNCTION method is the basic design method of FIR filter, is widely used.In the present embodiment, with THE DESIGN OF WINDOW FUNCTION method designing filter the time, can use triumphant damp window.Because triumphant damp window is one of useful and the most optimum window construction.For given stopband attenuation, it provides minimum main lobe width, the transition band of steepest namely, and just in this point, it is optimum.During specific implementation, first the empirical equation according to triumphant damp window calculates filter parameter N and β, and the firl function that then provides by MATLAB obtains desired filter coefficient vector, again with the form of coefficient table at the DSP Calling.
Sampled point is synchronous
Sampled point is a synchronization concept that proposes for native system synchronously.Sampled point requires synchronously to separate the bit synchronization timing error that timing recovers and is no more than an audio sample point interval, and the synchronization timing of ascending the throne can be as accurate as sampled point.Only in this way, could satisfy the required precision that the audio transmission time-delay is calculated.The synchronous realization of sampled point is particularly important, and it is the basis of follow-up series of computation.
The FSK demodulation
The FSK demodulation is adopted relevant and the square-law decision device finish sampled point synchronously, frame synchronization, method is as shown in figure 14.
The correlation detection principle of FSK is to carry out demodulation by the square-law maximum of relatively correlator output.The FSK modulated wave that obtains and in-phase component and the quadrature component of frame head data are carried out related calculation respectively, obtain two groups of correlation computations results, square operation is done in two class value pointwises, and the result is carried out addition, preserve operation result.Simultaneously ask for maximum in the result, the maximum corresponding points that find within a frame period are the frame synchronization point, thereby recover the accurate sampled point relative position relation of whole transmission frame, realize sampled point synchronously, bit synchronization and frame synchronization.Calculate maximum outgoing position homogeneous phase simultaneously at continuous 3 times, we think that system enters sampled point precise synchronization state.Adopt above-mentioned demodulating algorithm, can realize simultaneously that bit synchronization, frame synchronization and sampled point are synchronous.
After realizing synchronously, the transmission frame data are carried out demodulation, separate timing employing method as shown in figure 15.Demodulation is carried out CRC check after obtaining whole transmission frame data, if the CRC check result is correct, then preserves demodulating data, output after resolving.If CRC check result is incorrect, then abandon data.
The application has proposed in a kind of digital synchronous frequency modulation broadcast system adding and the extracting method with the road voice-frequency signaling.By the analysis of the audio transmission mode that may use synchronous frequency-modulating broadcast network, proposed a kind ofly will add universal method in the simulated audio signal with the road voice-frequency signaling.This method will be modulated to the high-end frequency of audio frequency with the road voice-frequency signaling by the FSK modulation first, be sent to transmission link with the audio signal frequency division multiplexing more together.Receiving terminal only needs high-pass filtering and carries out the FSK demodulation that just can to obtain transmitting terminal added with the road voice-frequency signaling.This adding method with the road voice-frequency signaling is applicable to the audio transmission system that any transmission bandwidth is 20KHz, has the most widely applicability.And this method need not to add any optional equipment, brings great convenience for the user in the actual sets network process.
The architecture Design with the road audio transmission system of frequency division multiplexing has taken into full account MPEG-2 encoder in the present the most frequently used DVB transmission system to the audio frequency radio-frequency component, also namely with the impact of road voice-frequency signaling.And for these impacts the parameters that adopts in the signalling process and strategy have been made detailed regulation.
Above-described embodiment is more preferably embodiment of the present invention, and the common variation that those skilled in the art carries out in the technical solution of the present invention scope and replacement all should be included in protection scope of the present invention.
Claims (3)
1. method that solves synchronous frequency-modulating broadcast system synchronization audio frequency time-delay calculation and adjustment, its transmission bandwidth is the audio transmission system of 20KHz, it is characterized in that, the Digit FM Exciter of described system is carried out following steps:
Steps A: the digital audio and video signals that receives is carried out low-pass filtering, for the Digit FM Exciter coded modulation; The digital audio and video signals that receives is carried out high-pass filtering, obtain the FSK modulated wave of signaling;
The correlation detection principle of step B:FSK is to carry out demodulation by the square-law maximum of relatively correlator output; The FSK modulated wave that obtains and in-phase component and the quadrature component of frame head data are carried out related calculation respectively, obtain two groups of correlation computations results, square operation is done in two class value pointwises, and the result is carried out addition, preserve operation result; Simultaneously ask for maximum in the result, the maximum corresponding points that find within a frame period are the frame synchronization point, thereby recover the accurate sampled point relative position relation of whole transmission frame, realize sampled point synchronously, bit synchronization and frame synchronization;
Step C: the signaling data that obtains is carried out CRC check and frame parsing, obtain correct network management information, and calculate the audio frequency time delay in conjunction with the 1PPS standard timing signal of GPS.
2. the method for solution synchronous frequency-modulating broadcast system synchronization audio frequency time-delay calculation as claimed in claim 1 and adjustment is characterized in that, among the step B, utilizes modulated wave and frame head to carry out related operation and realizes that frame head is synchronous, and realize that sampled point is synchronous.
3. the method for solution synchronous frequency-modulating broadcast system synchronization audio frequency time-delay calculation as claimed in claim 1 and adjustment is characterized in that, the system clock of transmitting-receiving two-end is all phase-locked with the 10MHz benchmark frequency marking that GPS provides; At set intervals, the original position of demodulation is finely tuned.
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| CN110392221A (en) * | 2018-04-19 | 2019-10-29 | 北京同方吉兆科技有限公司 | A kind of emergent broadcast transmission structure based on the synchronous net system of frequency modulation |
| CN113037413B (en) * | 2021-03-11 | 2023-04-21 | 成都德芯数字科技股份有限公司 | Frequency modulation synchronization method, device, system, equipment and storage medium |
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