阅读说明：本技术 一种面向mf-tdma的星上多载波解调器 (Satellite multi-carrier demodulator facing MF-TDMA ) 是由 陈实华 刘向 倪祖耀 阳凯 曹春燕 余洋 王育强 唐海 于 2019-09-27 设计创作，主要内容包括：本发明公开了一种面向MF?TDMA的星上多载波解调器，包括时间共享的全时捕获器、定时同步器、载波跟踪环路和符号解映射器；所述全时捕获器，用于分别对输入数据及延时后的输入数据进行滤波后，通过计算得到粗捕频偏补偿值和粗捕相偏补偿值；所述定时同步器，用于根据输入的星上多载波分路后的串流形式的多路IQ信号得到定时同步后插值恢复的数据；所述载波跟踪环路，用于完成残留多普勒频率的剥离，得到载波跟踪的数据；所述符号解映射器根据调制方式对定时同步和载波跟踪的数据完成符号解映射。本发明用一路高速解调器通过时分复用的方式来支持多路低速信号的解调，电路复用率高、资源开销低、时延小且处理灵活。(The invention discloses an MF-TDMA (Multi-frequency time division multiple Access) -oriented satellite multi-carrier demodulator, which comprises a time-sharing full-time capturer, a timing synchronizer, a carrier tracking loop and a symbol demapper; the full-time capturer is used for respectively filtering the input data and the delayed input data and obtaining a coarse frequency-capturing offset compensation value and a coarse phase-capturing offset compensation value through calculation; the timing synchronizer is used for obtaining data of interpolation recovery after timing synchronization according to input multi-path IQ signals in a streaming form after satellite multi-carrier shunting; the carrier tracking loop is used for completing the stripping of the residual Doppler frequency to obtain carrier tracking data; and the symbol demapper finishes symbol demapping on the data of the timing synchronization and the carrier tracking according to a modulation mode. The invention uses a high-speed demodulator to support the demodulation of multi-path low-speed signals in a time division multiplexing mode, and has the advantages of high circuit multiplexing rate, low resource overhead, small time delay and flexible processing.)

1. An MF-TDMA-oriented on-satellite multi-carrier demodulator is characterized by comprising a time-sharing full-time acquirer, a timing synchronizer, a carrier tracking loop and a symbol demapper;

the full-time capturer is used for respectively filtering the input data and the delayed input data and obtaining a coarse frequency-capturing offset compensation value and a coarse phase-capturing offset compensation value through calculation; the input data comprises multi-path IQ signals in a streaming form after multi-carrier branching on the satellite, carrier tags corresponding to the branching and effective enabling of data;

the timing synchronizer is used for sequentially carrying out serial-parallel conversion, timing error detection and interpolation operation on input multi-path IQ signals in a streaming form after satellite multi-carrier shunting to obtain data recovered by interpolation after timing synchronization; storing each carrier parameter into RAM according to the address corresponding to the carrier label, and taking out the corresponding carrier parameter to perform interpolation operation when multiple paths of IQ signals arrive each time;

the carrier tracking loop comprises a carrier phase discriminator, a loop filter, NCO data storage and an NCO numerical control oscillator, and data recovered by interpolation after timing synchronization is sent to the carrier tracking loop at a symbol rate; the carrier phase discriminator selects a corresponding phase discrimination formula according to a modulation mode to extract the phase difference of the current symbol; the loop filter calculates a phase discrimination result with a carrier label and a last loop filter result to output a frequency control word; the NCO data storage is used for storing frequency control words of each branch of the multi-carrier; the NCO numerical control oscillator inputs the rough catching frequency offset compensation value and the rough catching phase offset compensation value into a storage space of a corresponding address to generate sine waves, and stripping of residual Doppler frequency is completed, so that carrier tracking data are obtained;

and the symbol demapper finishes symbol demapping on the data of the timing synchronization and the carrier tracking according to a modulation mode.

2. An MF-TDMA oriented satellite multi-carrier demodulator according to claim 1, wherein the value interval of the carrier tag is [0, M-1], where M is the maximum number of carriers in the MF-TDMA system.

3. An MF-TDMA oriented satellite multi-carrier demodulator according to claim 1, wherein the full time capturer employs filters H1 and H2 to filter the input data and the delayed input data, respectively; the filters H1 and H2 are both direct FIR filters.

4. An MF-TDMA oriented on-satellite multi-carrier demodulator according to claim 3, characterised in that, if the sequence length of the data frame header up-sampling 4 times of the input data is N, the first N/2 sequence is taken as the coefficients of filter H1, and the last N/2 sequence is taken as the coefficients of filter H2.

5. An MF-TDMA oriented satellite multi-carrier demodulator according to claim 3, characterized in that the delay length of the delayed input data is N/2.

6. An MF-TDMA oriented satellite multi-carrier demodulator according to claim 3, characterized in that each stage of filter arithmetic units of the filters H1 and H2 opens up a memory space RAM of depth M, data is initialized to 0; when the filters H1 and H2 carry out filtering, according to the effective enabling of the carrier tags and the data, the data with the address equal to the carrier tags are read from the storage space RAM by the filter operation units of each stage and are sent to the operation unit of the next stage, and the address data space is updated by the operation result of the current stage.

7. An MF-TDMA oriented satellite multi-carrier demodulator according to claim 3, wherein the output result of the filter H1 is Y1, the output result of the filter H2 is Y2, wherein Y1 and Y2 are both complex numbers, and the procedure of calculating the coarse frequency-capture offset compensation value and the coarse frequency-capture offset compensation value by the full-time capturer is as follows:

(1) adding Y1 and Y2 to obtain SUM;

(2) performing modulo operation on the SUM to obtain Amp; wherein SUM is complex number, Amp is real number;

(3) comparing the SUM with each threshold, and when the SUM is larger than the threshold, successfully capturing;

(4) performing conjugate multiplication on Y1 and Y2 corresponding to the maximum value in the SUM with all successful threshold capturing to obtain Conj _ Y1Y 2; wherein Conj _ Y1Y2 is a complex number;

(5) after the inverse tangent of Conj _ Y1Y2 is calculated, dividing the inverse tangent by T/2 to obtain residual frequency difference Feq, namely a coarse frequency capture offset compensation value;

(6) conjugate multiplying Conj _ Y1Y2 and SUM to obtain Pha;

(7) and taking Pha as Conj _ Pha, namely a coarse phase-capturing offset compensation value.

8. An MF-TDMA oriented satellite multi-carrier demodulator according to claim 3, characterized in that the timing synchronizer employs a forward structure based on square-law timing estimation.

Technical Field

The invention relates to the technical field of satellite communication, in particular to an MF-TDMA-oriented satellite multi-carrier demodulator.

Background

With the continuous increase of the requirement of satellite broadband services, more and more countries are put into the research, development and application of high-throughput communication satellites, and the overall technical trend is developed towards the direction of on-satellite regeneration processing and switching from the traditional bent-tube transparent forwarding. The broadband communication system mostly adopts an MF-TDMA multiple access mode, and adapts to different service transmission and networking requirements through dynamic configuration of carrier number and carrier rate. The on-satellite regeneration processing facing the MF-TDMA mainly comprises multi-carrier shunting and multi-carrier demodulation, wherein after non-uniform channel separation is completed on the satellite through the multi-carrier shunting, multi-channel low-speed data are sent to a multi-carrier demodulator in a streaming mode to complete real-time multi-user real-time acquisition, timing synchronization, carrier tracking and symbol demapping. Because a broadband communication satellite serves many users simultaneously, and in an on-demand dynamic resource allocation system, the number of carriers and the carrier rate may change with the difference of user distribution and user types, if a conventional modulation and demodulation technology needs a large amount of demodulator resources and multi-rate clock resources, as shown in fig. 1, it poses a serious challenge to the digital resource allocation of satellite loads, and thus an efficient multi-carrier demodulation structure is a key technology for on-satellite regeneration processing.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the existing problems, the satellite multi-carrier demodulator facing MF-TDMA is provided, a path of high-speed demodulator supports the demodulation of a plurality of paths of low-speed signals in a time division multiplexing mode, and has the advantages of high circuit multiplexing rate, low resource overhead, small time delay and flexible processing.

The technical scheme adopted by the invention is as follows:

an MF-TDMA-oriented on-satellite multi-carrier demodulator comprises a time-sharing full-time capturer, a timing synchronizer, a carrier tracking loop and a symbol demapper;

the full-time capturer is used for respectively filtering the input data and the delayed input data and obtaining a coarse frequency-capturing offset compensation value and a coarse phase-capturing offset compensation value through calculation; the input data comprises multi-path IQ signals in a streaming form after multi-carrier branching on the satellite, carrier tags corresponding to the branching and effective enabling of data;

the timing synchronizer is used for sequentially carrying out serial-parallel conversion, timing error detection and interpolation operation on input multi-path IQ signals in a streaming form after satellite multi-carrier shunting to obtain data recovered by interpolation after timing synchronization; storing each carrier parameter into RAM according to the address corresponding to the carrier label, and taking out the corresponding carrier parameter to perform interpolation operation when multiple paths of IQ signals arrive each time;

the carrier tracking loop comprises a carrier phase discriminator, a loop filter, NCO data storage and an NCO numerical control oscillator, and data recovered by interpolation after timing synchronization is sent to the carrier tracking loop at a symbol rate; the carrier phase discriminator selects a corresponding phase discrimination formula according to a modulation mode to extract the phase difference of the current symbol; the loop filter calculates a phase discrimination result with a carrier label and a last loop filter result to output a frequency control word; the NCO data storage is used for storing frequency control words of each branch of the multi-carrier; the NCO numerical control oscillator inputs the rough catching frequency offset compensation value and the rough catching phase offset compensation value into a storage space of a corresponding address to generate sine waves, and stripping of residual Doppler frequency is completed, so that carrier tracking data are obtained;

and the symbol demapper finishes symbol demapping on the data of the timing synchronization and the carrier tracking according to a modulation mode.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the satellite multi-carrier demodulator facing MF-TDMA supports demodulation of multi-path low-speed signals by a path of high-speed demodulator in a time division multiplexing mode, and has high circuit multiplexing rate, low resource overhead, small time delay and flexible processing.

2. In the demodulation process of the satellite multi-carrier demodulator facing the MF-TDMA, data is input into the multi-carrier demodulator in a time division low-speed streaming mode, intermediate results in the operation process are cached according to shunt carrier tags, corresponding carrier data enters the multi-carrier demodulator every time, corresponding cache space is used for data operation and new operation result updating, the whole data input and output time sequence cannot be changed, and meanwhile, the occupied cache space is smaller.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a block diagram of a conventional multi-carrier demodulation module.

Fig. 2 is a schematic diagram of a multi-carrier demodulator according to the present invention.

Fig. 3 is a diagram illustrating a data frame format of input data of a multi-carrier demodulator according to the present invention.

Fig. 4 is a timing diagram of input data of the multi-carrier demodulator according to the present invention.

Fig. 5 is a constellation diagram of a carrier before and after timing synchronization and carrier tracking using the multi-carrier demodulator of the present invention.

Detailed Description

The invention relates to an MF-TDMA-oriented satellite multi-carrier demodulator, which comprises a time-sharing full-time capturer, a timing synchronizer, a carrier tracking loop and a symbol demapper, wherein a path of high-speed demodulator is used for supporting the demodulation of a plurality of paths of low-speed signals in a time division multiplexing mode, and the satellite multi-carrier demodulator has the advantages of high circuit multiplexing rate, low resource overhead, small time delay and flexible processing. In the demodulation process, data is input into the multi-carrier demodulator in a time division low-speed streaming mode, intermediate results in the operation process are cached according to a shunt carrier label, corresponding carrier data enters the multi-carrier demodulator each time, data operation and new operation result updating are carried out in corresponding caching space, the whole data input and output time sequence cannot be changed, and meanwhile, the occupied caching space is smaller.

The features and properties of the present invention are described in further detail below with reference to examples.

The basic implementation mode is as follows:

the invention provides an MF-TDMA-oriented satellite multi-carrier demodulator, which comprises a time-sharing full-time capturer, a timing synchronizer, a carrier tracking loop and a symbol demapper, as shown in figure 2; the number of carriers can support dozens to hundreds, the carrier symbol rate is graded by power of 2, and assuming that the minimum rate is Rs, the supportable rate comprises the following steps: rs, 2Rs, 4Rs, 8Rs, and the like, and the specific processing procedure of the multi-carrier demodulator is as follows:

1. inputting data; the input data comprises multi-path IQ signals in a streaming form after multi-carrier branching on the satellite, carrier tags corresponding to the branching and effective enabling of data; preferably, the value interval of the carrier tag is [0, M-1], where M is the maximum number of carriers under the MF-TDMA system. In this case, the data stream rate of each carrier is typically 4 times the symbol rate and is sent to the full-time capturer.

2. The full-time capturer is used for respectively filtering the input data and the delayed input data and obtaining a coarse frequency-capturing offset compensation value and a coarse phase-capturing offset compensation value through calculation;

specifically, the full-time capturer adopts filters H1 and H2 to filter the input data and the delayed input data respectively; wherein, the filters H1 and H2 both support multi-path serial filtering, and a direct FIR filter can be adopted. Further, the tap coefficients of the filters H1 and H2 are the sequence length N of 4 times of the data frame header of the input data, and then the first N/2 sequence is used as the coefficients of the filter H1 (filter for filtering the input data) and the last N/2 sequence is used as the coefficients of the filter H2 (filter for filtering the delayed input data).

The delay length of the input data after delay is N/2, the input data before and after delay are baseband complex signals, and the input data before and after delay are respectively sent to filters H1 and H2. The filter arithmetic units of each stage of the filters H1 and H2 open a storage space RAM with the depth of M, and data are initialized to 0; when the filters H1 and H2 carry out filtering, according to the effective enabling of the carrier tags and the data, the data with the address equal to the carrier tags are read from the storage space RAM by the filter operation units of each stage and are sent to the operation unit of the next stage, and the address data space is updated by the operation result of the current stage.

Further, assuming that the output result of the filter H1 is Y1, the output result of the filter H2 is Y2, where Y1 and Y2 are both complex numbers, the process of calculating the coarse phase-capturing offset compensation value and the coarse phase-capturing offset compensation value by the full-time capturer is as follows:

(1) adding Y1 and Y2 to obtain SUM;

(2) performing modulo operation on the SUM to obtain Amp; wherein SUM is complex number, Amp is real number;

(3) comparing the SUM with a threshold, and when the SUM is larger than the threshold, successfully capturing;

(4) carrying out conjugate multiplication on Y1 and Y2 corresponding to the maximum value in the successfully captured SUM to obtain Conj _ Y1Y 2; where Conj _ Y1Y2 is complex, and this value is the phase change to the corresponding IQ value within T/2 (assuming that the carrier rate is Rs _ index, then T is N/Rs _ index);

(5) after the inverse tangent of Conj _ Y1Y2 is calculated, dividing the inverse tangent by T/2 to obtain residual frequency difference Feq, namely a coarse frequency capture offset compensation value;

(6) conjugate multiplication is carried out on Conj _ Y1Y2 and SUM to obtain Pha, namely the phase value of the capture frame tail time;

(7) and taking Pha as Conj _ Pha, namely a coarse phase-capturing offset compensation value, wherein the Pha and the Conj _ Pha are complex numbers. The phase is not required to be obtained, and only IQ values corresponding to the phase are required to be compensated, so that resources are saved.

3. The timing synchronizer is used for sequentially carrying out serial-parallel conversion, timing error detection and interpolation operation on input multi-path IQ signals in a streaming form after satellite multi-carrier shunting to obtain data recovered by interpolation after timing synchronization; storing each carrier parameter into RAM according to the address corresponding to the carrier label, and taking out the corresponding carrier parameter to perform interpolation operation when multiple paths of IQ signals arrive each time; preferably, the timing synchronizer adopts a forward structure based on square law timing estimation, and avoids the phenomenon that the convergence time of a feedback structure is too long and the phenomenon of 'hanging' possibly occurs. The serial-parallel conversion is that several sample values of a symbol in input data are parallelly and simultaneously fed into an error detector to complete timing error detection, and every time the coming parallel input data of each path takes out corresponding carrier parameters to complete an interpolation operation, so as to obtain the recovery of the optimal sampling point, namely the data recovered by interpolation after timing synchronization.

4. The carrier tracking loop comprises a carrier phase discriminator, a loop filter, NCO data storage and an NCO numerical control oscillator, and data recovered by interpolation after timing synchronization is sent to the carrier tracking loop at a symbol rate; the carrier phase discriminator selects a corresponding phase discrimination formula according to a modulation mode to extract the phase difference of the current symbol; the loop filter calculates a phase discrimination result with a carrier label and a last loop filter result to output a frequency control word; the NCO data storage is used for storing frequency control words of each branch of the multi-carrier; the NCO numerical control oscillator inputs the rough catching frequency offset compensation value and the rough catching phase offset compensation value into a storage space of a corresponding address to generate sine waves, and stripping of residual Doppler frequency is completed, so that carrier tracking data are obtained;

and the symbol demapper finishes symbol demapping on the data of the timing synchronization and the carrier tracking according to a modulation mode.

Specific examples are as follows:

an MF-TDMA oriented satellite multi-carrier demodulator, as shown in fig. 2, includes a time-shared full-time acquirer, a timing synchronizer, a carrier tracking loop and a symbol demapper; the dynamic maximum configuration of the MF-TDMA carrier wave is as follows: 200 paths 250Ksps, wherein the 250Ksps rate-progressive frame format is shown in fig. 3, and the duration of the corresponding data frame varies with the symbol rate.

The specific processing procedure of the multi-carrier demodulator is as follows:

1. inputting data; the input data comprises multi-path IQ signals in a streaming form after satellite multi-carrier shunting, carrier tags iChan _ idx corresponding to the shunting, and data effective enabling iDin _ dv; wherein, the value interval of the carrier label iChan _ idx is [0,199 ]. At this time, the data flow rate of each carrier is sent to the full-time grabber at 4 times the symbol rate, and the input timing diagram is shown in fig. 3.

2. The full-time capturer is used for respectively filtering the input data and the delayed input data and obtaining a coarse frequency-capturing offset compensation value and a coarse phase-capturing offset compensation value through calculation; the input data comprises multi-path IQ signals in a streaming form after satellite multi-carrier shunting, carrier tags iChan _ idx corresponding to the shunting, and data effective enabling iDin _ dv; wherein, the filters H1 and H2 both adopt a direct FIR filter. According to the frame format shown in fig. 3, the header symbol length is 256, and the tap coefficients of the filters H1 and H2 are 4 times the length of the data frame header upsampled, i.e. 256 × 4 equals 1024. The first 512 sequences are taken as the coefficients of filter H1 (the filter used to filter the input data) and the 512 sequences are taken as the coefficients of filter H2 (the filter used to filter the delayed input data), both filters H1 and H2 supporting multiple serial filtering.

The input data is recorded as D1, the delayed input data is recorded as D2, the delay length of D2 is 512 sampling points under 250Ksps, wherein D1 and D2 are both baseband complex signals, and D1 and D2 are aligned and respectively sent to filters H1 and H2. The filter arithmetic units of each stage of the filters H1 and H2 open a storage space RAM with the depth of M, and data are initialized to 0; when the filters H1 and H2 perform filtering, according to the carrier label iChan _ idx and the data effective enable iDin _ dv, the data of the address RAM _ addr ═ iChan _ idx is read from the storage space RAM by the filter operation unit of each stage and sent to the operation unit of the next stage, and the address data space is updated by the operation result of this time.

Further, assuming that the output result of the filter H1 is Y1, the output result of the filter H2 is Y2, where Y1 and Y2 are both complex numbers, the process of calculating the coarse phase-capturing offset compensation value and the coarse phase-capturing offset compensation value by the full-time capturer is as follows:

(1) adding Y1 and Y2 to obtain SUM;

(2) performing modulo operation on the SUM to obtain Amp; wherein SUM is complex number, Amp is real number;

(3) comparing the SUM with a threshold, and when the SUM is larger than the threshold, successfully capturing; it should be noted that, the sampling rate is generally 4 times of the symbol rate, there may be 4 SUM that pass the threshold, the maximum value in 4 SUM that pass the threshold needs to be solved, and the sampling point corresponding to the maximum value is the frame start coarse estimation value;

(4) carrying out conjugate multiplication on Y1 and Y2 corresponding to the maximum value in the successfully captured SUM to obtain Conj _ Y1Y 2; where Conj _ Y1Y2 is complex, and this value is the phase change to the corresponding IQ value within T/2 (assuming that the carrier rate is Rs _ index, then T is N/Rs _ index);

(5) after the inverse tangent of Conj _ Y1Y2 is calculated, dividing the inverse tangent by T/2 to obtain residual frequency difference Feq, namely a coarse frequency capture offset compensation value;

(6) conjugate multiplication is carried out on Conj _ Y1Y2 and SUM to obtain Pha, namely the phase value of the capture frame tail time;

(7) and taking Pha as Conj _ Pha, namely a coarse phase-capturing offset compensation value, wherein the Pha and the Conj _ Pha are complex numbers. The phase is not required to be obtained, and only IQ values corresponding to the phase are required to be compensated, so that resources are saved.

3. The timing synchronizer is used for sequentially carrying out serial-parallel conversion, timing error detection and interpolation operation on input multi-path IQ signals in a streaming form after satellite multi-carrier shunting to obtain data recovered by interpolation after timing synchronization; storing each carrier parameter into an RAM according to an address corresponding to a carrier label iChan _ idx, and taking out the corresponding carrier parameter to perform interpolation operation when multiple paths of IQ signals arrive each time; in this example, the timing synchronizer employs a forward structure based on square-law timing estimation. The serial-parallel conversion is to make 4 samples of a symbol in input data enter an error detector in parallel to complete timing error detection, and take out corresponding carrier parameters from 4 paths of parallel input data to complete an interpolation operation every time, so as to obtain the recovery of an optimal sampling point, namely the data recovered by interpolation after timing synchronization.

The carrier tracking loop comprises a carrier phase discriminator, a loop filter, NCO data storage and an NCO numerical control oscillator, and data recovered by interpolation after timing synchronization is sent to the carrier tracking loop at a symbol rate; the carrier phase discriminator selects a corresponding phase discrimination formula according to a modulation mode to extract the phase difference of the current symbol; the loop filter calculates the phase discrimination result with the carrier label and the previous loop filter result to output frequency control words, the loop filter can adopt a traditional second-order loop structure, and considering that the loop filter is a feedback system, the variable of the loop filter needs to be stored by an RAM (random access memory), the phase discrimination result with the carrier label and the previous loop filter result are calculated each time to output the frequency control words, the numerical value is replaced and stored to a corresponding RAM space, and when the next data comes to participate in the calculation, the NCO data memory is adopted to store the frequency control words of each multi-carrier branch; inputting the coarse acquisition frequency offset compensation value Feq and the coarse acquisition phase offset compensation value Conj _ Pha into a storage space of a corresponding address by an NCO numerical control oscillator to generate a sine wave, and completing stripping of residual Doppler frequency so as to obtain carrier tracking data;

and the symbol demapper finishes symbol demapping on the data of the timing synchronization and the carrier tracking according to a modulation mode. Taking QPSK signal as an example, the constellation before and after timing synchronization and carrier tracking of a certain carrier branch is shown in fig. 5, and symbol demapping is completed according to different modulation modes.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.