CN117544183B - Forward intermediate frequency processing system and method supporting variable symbol rate - Google Patents

Forward intermediate frequency processing system and method supporting variable symbol rate Download PDF

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CN117544183B
CN117544183B CN202410025964.5A CN202410025964A CN117544183B CN 117544183 B CN117544183 B CN 117544183B CN 202410025964 A CN202410025964 A CN 202410025964A CN 117544183 B CN117544183 B CN 117544183B
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frequency
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rate
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CN117544183A (en
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焦杰
焦计平
陈威
徐钧
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Space Engineering Network Technology Development Hangzhou Co ltd
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Space Engineering Network Technology Development Hangzhou Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
    • H04B1/0007—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/66—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for reducing bandwidth of signals; for improving efficiency of transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/74—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission for increasing reliability, e.g. using redundant or spare channels or apparatus
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

The application discloses a forward intermediate frequency processing system and a method supporting variable symbol rate. The system comprises: a transmitter, configured to perform a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation, and a first digital mixing parallel operation on a first baseband signal with a variable symbol rate to generate a parallel first intermediate frequency digital signal with a first sampling rate, and send the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit to sample and generate a first intermediate frequency analog signal; a receiver for performing a frequency shift parallel operation, a hilbert transform parallel operation, a frequency domain filtering parallel operation, a time domain filtering parallel operation, and an interpolation parallel operation on the parallel second intermediate frequency digital signal to generate a parallel second baseband signal having a variable symbol rate of which the sampling rate is multiple; the second intermediate frequency digital signal is an intermediate frequency digital signal generated by sampling the second intermediate frequency analog signal through the analog-to-digital conversion unit.

Description

Forward intermediate frequency processing system and method supporting variable symbol rate
Technical Field
The present invention relates to the field of satellite communications. And more particularly to a forward intermediate frequency processing system and method supporting variable symbol rates.
Background
The existing forward intermediate frequency variable symbol rate selection set is limited, the implementation complexity is high, and the symbol rate and the sampling rate of the intermediate frequency need to have strict integer multiple relation. In addition, the intermediate frequency processing is required to support the symbol rate to be variable in a large range according to the change of the satellite communication bandwidth requirement.
Therefore, it is needed to provide a forward intermediate frequency processing system and method supporting variable symbol rate, which are used for solving the problem of variable symbol rate in a larger range and meeting the requirement of flexible configuration of a broadband system.
Disclosure of Invention
It is an object of the present invention to provide a forward intermediate frequency processing system and method supporting variable symbol rates to address at least one of the problems of the prior art.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a first aspect of the present invention provides a forward intermediate frequency processing system supporting variable symbol rates, the system comprising:
a forward variable rate transmitter for performing a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation, and a first digital mixing parallel operation on a first baseband signal having a variable symbol rate to generate a parallel first intermediate frequency digital signal having a first sampling rate, and transmitting the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit to perform a sampling operation and generate a first intermediate frequency analog signal;
A forward variable rate receiver for performing a frequency shift parallel operation, a hilbert transform parallel operation, a frequency domain filtering parallel operation, a time domain filtering parallel operation, and an interpolation parallel operation on a parallel second intermediate frequency digital signal to generate a parallel second baseband signal having a sampling rate that is multiple of the variable symbol rate; the second intermediate frequency digital signal is an intermediate frequency digital signal generated by sampling the received second intermediate frequency analog signal through an analog-to-digital conversion unit.
Optionally, the forward variable rate transmitter includes a first rate interpolation unit and at least one parallel branch, where each parallel branch includes a first root raised cosine filter unit, a plurality of second rate interpolation units, a plurality of first half-band filter units corresponding to the second rate interpolation units one to one, a plurality of first lagrangian interpolation units, and a plurality of first digital frequency shift units corresponding to the first lagrangian interpolation units one to one; wherein,
the input end of the first rate interpolation unit receives the first baseband signals, and the output end of the first rate interpolation unit is connected with the input end of each first root raised cosine filter unit;
The output end of each first root raised cosine filter unit is connected with the input end of each second rate interpolation unit of the corresponding branch respectively, and the output end of each second rate interpolation unit is connected with the input end of the corresponding first half-band filter unit;
the output end of each first half-band filtering unit is connected with the input end of each first Lagrangian interpolation unit of the corresponding branch respectively, and the output end of each first Lagrangian interpolation unit is connected with the input end of the corresponding first digital frequency shifting unit;
and the output ends of the plurality of first digital frequency shifting units output the parallel first intermediate frequency digital signals.
Optionally, the step of the first lagrangian interpolation unit is:
in the method, in the process of the invention,for the variable symbol rate; />Is the sampling rate of the digital-to-analog conversion unit.
Optionally, the forward variable rate receiver includes a plurality of second digital frequency shift units, a fast fourier transform unit, a first frequency domain filter unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filter units; wherein,
the input ends of the plurality of second digital frequency shifting units receive the parallel second intermediate frequency digital signals, and the output ends of the plurality of second digital frequency shifting units are connected with the input ends of the fast Fourier transform units;
The output end of the fast Fourier transform unit is connected with the input end of the first frequency domain filtering unit, and the output end of the first frequency domain filtering unit is connected with the input end of the inverse fast Fourier transform unit;
the output ends of the inverse fast Fourier transform units are connected with the input ends of the second Lagrange interpolation units, and the output ends of the second Lagrange interpolation units are connected with the input ends of the third time domain filtering units;
and the output ends of the third time domain filtering units output the parallel second baseband signals.
Optionally, the forward variable rate receiver includes a fast fourier transform unit, a first frequency domain filtering unit, a first frequency domain frequency shift unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units; wherein,
the input end of the fast Fourier transform unit receives the parallel second intermediate frequency digital signal, and the output end of the fast Fourier transform unit is connected with the input end of the first frequency domain filtering unit;
the output end of the first frequency domain filtering unit is connected with the input end of the first frequency domain frequency shifting unit, and the output end of the first frequency domain frequency shifting unit is connected with the input end of the inverse fast Fourier transform unit;
The output ends of the inverse fast Fourier transform units are connected with the input ends of the second Lagrange interpolation units, and the output ends of the second Lagrange interpolation units are connected with the input ends of the third time domain filtering units;
and the output ends of the third time domain filtering units output the parallel second baseband signals.
Optionally, the single-sided passband bandwidth of the first frequency domain filtering unit is:
in the method, in the process of the invention,for the variable symbol rate; />A roll-off coefficient for the first frequency domain filtering unit; />The channel spacing protection coefficient; />Representing the channel; />Indicating that the passband magnitude is 1;
the step of the second Lagrangian interpolation unit is:
in the method, in the process of the invention,for the variable symbol rate; />And (3) the data sampling rate after the inverse fast Fourier transform operation.
Optionally, the first frequency domain filtering unit isThe first frequency domain filtering unit comprises a path parallel processing structureA filter factor, said->The individual filter factors are at said->The length of the parallel processing structure of the path is +.>Sequentially and parallelly arranged; wherein,
the relation between the input and the output of the first frequency domain filtering unit is as follows:
in the method, in the process of the invention, Multiple parallel lines generated for the fast Fourier transform unit>A plurality of frequency domain signals; />Is->A filter factor; />A filtered parallel +.>A plurality of filtered signals;。
a second aspect of the present invention provides a method of forward intermediate frequency processing supporting variable symbol rates, the method comprising:
performing a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation and a first digital mixing parallel operation on a first baseband signal with a variable symbol rate by using a forward variable rate transmitter to generate a parallel first intermediate frequency digital signal with a first sampling rate, and transmitting the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit to perform sampling operation and generate a first intermediate frequency analog signal;
performing frequency shift parallel operation, hilbert transform parallel operation, frequency domain filtering parallel operation, time domain filtering parallel operation and interpolation parallel operation on the parallel second intermediate frequency digital signals by using a forward variable rate receiver to generate parallel second baseband signals with the variable symbol rate of which the sampling rate is multiple; the second intermediate frequency digital signal is a parallel intermediate frequency digital signal which is generated by sampling operation of the received second intermediate frequency analog signal through the analog-to-digital conversion unit.
Optionally, the forward variable rate receiver includes a plurality of second digital frequency shifting units, a fast fourier transform unit, a first frequency domain filtering unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units, and the forward intermediate frequency processing method further includes:
receiving the parallel second intermediate frequency digital signals through a plurality of second digital frequency shifting units, and transmitting the parallel digital frequency shifting signals subjected to digital frequency shifting to the fast Fourier transform unit;
performing fourier transform on the received parallel digital frequency-shifted signals by the fast fourier transform unit and transmitting the generated parallel frequency-domain signals to the first frequency-domain filtering unit;
the first frequency domain filtering unit filters the parallel frequency domain signals and transmits the filtered parallel filtering signals to the inverse fast fourier transform unit;
the inverse fast fourier transform unit performs inverse fourier transform on the parallel filtered signals and transmits the generated parallel time domain signals to a plurality of second lagrangian interpolation units;
and the plurality of second Lagrangian interpolation units conduct interpolation operation on the parallel time domain signals, the generated parallel interpolation signals are transmitted to the plurality of third time domain filtering units, and the parallel second baseband signals are output after being filtered by the plurality of third time domain filtering units.
Optionally, the forward variable rate receiver includes a fast fourier transform unit, a first frequency domain filtering unit, a first frequency domain frequency shift unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units, and the forward intermediate frequency processing method further includes:
receiving the parallel second intermediate frequency digital signals through the fast Fourier transform unit to perform Fourier transform and transmitting the generated parallel frequency domain signals to the first frequency domain filtering unit;
the first frequency domain filtering unit filters the parallel frequency domain signals and transmits the filtered parallel filtering signals to the first frequency domain frequency shifting unit;
the first frequency domain frequency shifting unit shifts the frequency of the parallel filtering signals and transmits the frequency-shifted parallel digital frequency shifting signals to the inverse fast Fourier transform unit;
the inverse fast fourier transform unit performs inverse fourier transform on the parallel digital frequency-shifted signals and transmits the generated parallel time domain signals to a plurality of second lagrangian interpolation units;
and the plurality of second Lagrangian interpolation units conduct interpolation operation on the parallel time domain signals, the generated parallel interpolation signals are transmitted to the plurality of third time domain filtering units, and the parallel second baseband signals are output after being filtered by the plurality of third time domain filtering units.
The beneficial effects of the invention are as follows:
the forward intermediate frequency processing system supporting variable symbol rate can support any symbol rate configuration, and the symbol rate can be changed between tens of megameters and hundreds of megameters; and the cascade combination of various filters is not needed, the structure is simple, and the implementation complexity is low.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
Fig. 1 is a schematic diagram of a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 2 shows a schematic diagram of a forward variable rate transmitter in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 3 shows a schematic diagram of a forward variable rate receiver in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a first lagrangian interpolation unit in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 5 shows a schematic diagram of a parallel architecture of forward variable rate transmitter intermediate frequency processing in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 6 shows a schematic diagram of a parallel structure of a first lagrangian interpolation unit in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 7 shows a frequency selective schematic of a forward variable rate receiver in a forward intermediate frequency processing system supporting variable symbol rates provided by an embodiment of the invention.
Fig. 8 shows a schematic diagram of an intermediate frequency processing parallel structure of a forward variable rate receiver in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 9 shows a schematic diagram of a frequency domain filtering structure and hilbert transform in a forward if processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 10 is a schematic diagram of a forward receiving frequency domain processing parallel FFT in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 11 is a schematic diagram of a forward receiving frequency domain processing parallel filter in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 12 shows an 8-way 128-point FFT parallel processing schematic diagram supporting 1024-point parallel FFT processing in a forward intermediate frequency processing system with variable symbol rate according to an embodiment of the present invention.
Fig. 13 shows a schematic diagram of multiplication by a twiddle factor in 1024-point parallel FFT processing in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 14 shows a schematic diagram of a full parallel 8-point FFT process in 1024-point parallel FFT processes in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 15 shows a schematic diagram of a parallel IFFT process for forward receiving frequency domain processing in a forward intermediate frequency processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 16 shows a schematic diagram of the impulse response of a 20Msps transmitter in a forward if processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 17 shows a schematic diagram of an impulse response of a 400Msps transmitter in a forward if processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 18 shows a symbol rate 20Msps receiver demodulation constellation in a forward if processing system supporting variable symbol rates according to an embodiment of the present invention.
Fig. 19 shows a symbol rate 400Msps receiver demodulation constellation in a forward if processing system supporting variable symbol rates according to an embodiment of the present invention.
Detailed Description
In order to more clearly illustrate the present invention, the present invention will be further described with reference to examples and drawings. Like parts in the drawings are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this invention is not limited to the details given herein.
The broadband satellite adopts a bandwidth repeater, can support single-carrier broadband forward broadcasting, and can flexibly divide a plurality of channels, and each channel carries out independent forward broadcasting. The existing forward intermediate frequency variable symbol rate selection set is limited, the implementation complexity is high, and the symbol rate and the sampling rate of the intermediate frequency need to have strict integer multiple relation. And the intermediate frequency processing is required to support a symbol rate that is variable over a wide range, depending on the variation in satellite communication bandwidth requirements.
Accordingly, one embodiment of the present invention provides a forward intermediate frequency processing system supporting variable symbol rates, the system comprising: a forward variable rate transmitter for performing a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation, and a first digital mixing parallel operation on a first baseband signal having a variable symbol rate and generating a parallel first intermediate frequency digital signal having a first sampling rate, and transmitting the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit for sampling operation and generating a first intermediate frequency analog signal; a forward variable rate receiver for performing a frequency shift parallel operation, a hilbert transform parallel operation, a frequency domain filtering parallel operation, a time domain filtering parallel operation, and an interpolation parallel operation on a parallel second intermediate frequency digital signal and generating a parallel second baseband signal having a sampling rate that is multiple of the variable symbol rate; the second intermediate frequency digital signal is an intermediate frequency digital signal generated by sampling the received second intermediate frequency analog signal through an analog-to-digital conversion unit.
Specifically, as shown in fig. 1, the forward communication system includes a forward variable rate transmitter and a forward variable rate receiver. The network side forward transmitter transmits high-level data through a local network, and sends out wireless signals in an air interface through baseband transmission processing, intermediate frequency transmission processing and radio frequency processing. The receiver receives the wireless signal, and transmits the data to the higher layer of the terminal side through radio frequency processing, intermediate frequency receiving and baseband receiving processing.
In one specific example, the baseband signal in the forward variable rate transmitter is subjected to a 2-fold rate interpolation, root raised cosine filter; then, interpolation is carried out at the rate of 2 times or 4 times, and a low-pass filter which is not limited by half-band filtering is used to reach the baseband rate of 4 times or 8 times; the method is not limited to an interpolator of a Lagrangian method, and any rate transformation ratio interpolation is realized, and the rate is increased from 4 times or 8 times to the sampling rate of a digital-to-analog converter (Digital to Analog Converter, DAC).
In one specific example, the forward variable rate transmitter includes multiple branches in parallel. Each branch comprises 1 root raised cosine filter, 1 or 2 interpolation and half-band filters, a multipath parallel interpolator and a frequency shifter; the output rate of the interpolator can reach the sampling rate of the DAC, and random rate matching is realized.
In one specific example, the forward variable rate receiver includes a digital frequency shift unit, a fast fourier transform (Fast Fourier Transform, FFT) processing unit, a frequency domain filtering unit, an inverse fast fourier transform (Inverse Fast Fourier Transform, IFFT) processing unit, an interpolator unit, and a root raised cosine filter unit. The digital frequency shifting unit shifts the intermediate frequency signal to a baseband; the FFT processing unit and the frequency domain filtering unit carry out frequency domain filtering, and the IFFT processing unit converts the frequency domain signals into time domain signals; then, a Lagrange interpolator is adopted to realize the matching of any rate, and the output sample rate is reduced to 2 times of the symbol rate; and sending the data to baseband demodulation through a root raised cosine filter.
In a specific example, the image frequency is filtered through a frequency domain Hilbert (Hilbert) transformation method, and the received real signal is recovered into a complex signal; compared with the conventional method, there is no particular limitation between the sampling rate and the symbol rate of the Analog-to-Digital Converter (ADC) in the present embodiment, and the sampling theorem is satisfied. This architecture can support higher symbol rates with the same ADC capabilities.
In the embodiment, half-band filtering and interpolation device combination is adopted in the intermediate frequency of the forward transmitter, frequency domain filtering and interpolation device combination is adopted in the intermediate frequency of the forward receiver, and the intermediate frequency variable symbol rate is supported at the receiving and transmitting ends. By adopting a combination of a filter and an interpolator in a forward intermediate frequency processing system, any symbol rate and any intermediate frequency sampling rate can be supported; meanwhile, the processing method of combining a single filter and an interpolator is adopted, the structure is simple, and the implementation complexity is reduced.
In related satellite communication systems, conventional transmitters typically employ digital intermediate frequency processing. The rate conversion of digital up-conversion is realized by means of multi-stage up-sampling and filter banks, each stage of up-sampling is followed by a stage of low-pass filter. When supporting variable symbol rate transmission, combining in a limited set of upsampling is required, while complex filter cascade combining is required. However, the up-sampling set selection is limited, so the selection of the variable symbol rate is also limited, and the symbol rate and the output DAC sample rate need to have a strict integer multiple relationship.
In one possible implementation, the forward variable rate transmitter includes a first rate interpolation unit and at least one parallel branch, each of the parallel branches including a first root raised cosine filter unit, a plurality of second rate interpolation units, a plurality of first half-band filter units in one-to-one correspondence with the second rate interpolation units, a plurality of first lagrangian interpolation units, and a plurality of first digital frequency shift units in one-to-one correspondence with the first lagrangian interpolation units; the input end of the first rate interpolation unit receives the first baseband signals, and the output end of the first rate interpolation unit is connected with the input end of each first root raised cosine filter unit; the output end of each first root raised cosine filter unit is connected with the input end of each second rate interpolation unit of the corresponding branch respectively, and the output end of each second rate interpolation unit is connected with the input end of the corresponding first half-band filter unit; the output end of each first half-band filtering unit is connected with the input end of each first Lagrangian interpolation unit of the corresponding branch respectively, and the output end of each first Lagrangian interpolation unit is connected with the input end of the corresponding first digital frequency shifting unit; and the output ends of the plurality of first digital frequency shifting units output the parallel first intermediate frequency digital signals.
In one specific example, as shown in fig. 2, the forward variable rate transmitter includes a 2-fold rate interpolator and Root-raised cosine filter (Root-Raised Cosine filter, RRC); then, a baseband rate of 4 times is achieved through a 2-time rate interpolator and a Half Band filter (Half-Band FIR, HBF); a Lagrange interpolator (Farrow) is connected to realize random rate transformation ratio interpolation, and the rate is increased from 4 times to n times; finally, the signals are output to a digital-to-analog converter for transmission after passing through a digital mixer (Numerically Controlled Oscillator, NCO).
The embodiment adopts the combination of a half-band filter and an interpolator, can be used for a forward transmitter and supports any symbol rate transmission; and there is no requirement for the DAC sampling rate. The DAC and its operating clock can be flexibly selected without being limited by the limited set of variable symbol rates in the conventional transmitter. On the other hand, the simplification of the structure in the embodiment reduces the implementation complexity, the traditional method needs to support various upsampling and various filter combinations, the implementation complexity is high, and the embodiment only needs one low-speed half-band filter and one interpolator, so that the structure is simple, and the implementation complexity is reduced.
In one possible implementation, the half-band filter is based on a 4-times rate, a 21 tap filter may be employed, with 10 tap coefficients of 0. In a specific example, the first half-band filtering unit is a filter with 21 taps; wherein the coefficient values of the 21 taps are 0, 0.0037, 0, -0.0188, 0, 0.0601, 0, -0.1636, 0, 0.6188, 1, 0.6188, 0, -0.1636, 0, 0.0601, 0, -0.0188, 0, 0.0037 and 0 in sequence.
In one possible implementation, the first lagrangian interpolation unit is a first lagrangian interpolator with 6 taps; wherein the relation of the first Lagrangian interpolator is:
in the method, in the process of the invention,is the output signal of the interpolator; />The sequence number of the interpolation coefficient; />Is->Coefficients for each tap; />Interpolation positions for integer multiples; />An input data signal for an interpolator; />Is an index of the input data signal.
In a specific example, a 6-tap Lagrangian interpolator is shown in FIG. 4, by which the matching of arbitrary symbol rates of the transmitter and receiver can be achieved. At least a first tap coefficient, a second tap coefficient, a third tap coefficient, a fourth tap coefficient, a fifth tap coefficient, and a sixth tap coefficient are included in fig. 4; including 6 time delays.
In a specific example, the interpolation position update formula of the lagrangian interpolator is:
in the method, in the process of the invention,interpolation position of decimal +.>，/>Stepping an interpolator;interpolation position for integer multiple->，/>Is a round down function.
In one possible implementation, the step of the first lagrangian interpolation unit is:
in the method, in the process of the invention,for the variable symbol rate; />Is the sampling rate of the digital-to-analog conversion unit.
In a specific example, letThe relationship between the interpolation coefficient and the interpolation position is:
in one specific example, assuming a system clock of 250MHz, parallel architecture processing is required when the transmitter is configured to a high symbol rate of 400 Msps. In one specific example, a parallel architecture of forward variable rate transmitter intermediate frequency processing is shown in fig. 5. Assuming that the system clock is 250MHz, the DAC sampling rate is 4GHz, the maximum symbol rate is 400Msps, and 4 root raised cosine filters are adopted in a parallel structure; 8 2-rate interpolators and a half-band filter; 16 parallel interpolators and frequency shifters. The output rate of the interpolator can reach the sampling rate of the DAC, and random rate matching is realized.
In a specific example, as shown in FIG. 6, which is a block diagram of parallel processing of an interpolator, it is assumed that the parallel branches of the interpolator are PThen there isPThe path parallel interpolation relation is:
in the method, in the process of the invention,is the input of the interpolator; />Is->Interpolation output of the branch circuits; />The sequence number of interpolation output in the branch is obtained; />Serial numbers of parallel branches; />Is->Interpolation coefficients of the branches; />；。
In a specific example, assume thatThe following steps are:
further, let theBased on the Lagrange interpolator of 6 th order, the +.>Interpolation coefficient of branch>The relationship between the interpolation position is:
in this embodiment, since the sampling rate of the DAC is higher, the transmitter interpolates from a low rate to a high rate, and when implemented, the transmitter adopts more parallel branches relative to the receiver.
In an associated satellite communication system, conventional forward receivers typically employ digital intermediate frequency processing. The rate conversion of digital down-conversion is realized by a multi-stage filter bank and a down-sampling mode, and each stage of low-pass filtering is followed by one stage of down-sampling. When supporting variable symbol rate reception, combining in a limited set of downsampling is required, while complex filter cascade combining is required for implementation. However, the downsampling set selection is limited, so the selection of the variable symbol rate is also limited, and the symbol rate and the input ADC sampling rate need to have a strict integer multiple relationship.
In one possible implementation, the forward variable rate receiver includes a plurality of second digital frequency shift units, a fast fourier transform unit, a first frequency domain filtering unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units; the input ends of the second digital frequency shifting units receive the parallel second intermediate frequency digital signals, and the output ends of the second digital frequency shifting units are connected with the input ends of the fast Fourier transform units; the output end of the fast Fourier transform unit is connected with the input end of the first frequency domain filtering unit, and the output end of the first frequency domain filtering unit is connected with the input end of the inverse fast Fourier transform unit; the output ends of the inverse fast Fourier transform units are connected with the input ends of the second Lagrange interpolation units, and the output ends of the second Lagrange interpolation units are connected with the input ends of the third time domain filtering units; and the output ends of the third time domain filtering units output the parallel second baseband signals.
In a specific example, shown in fig. 3 is a block diagram of forward variable rate receiver intermediate frequency processing, including a digital frequency shifting unit, a fast fourier transform unit, a frequency domain filtering unit, an inverse fast fourier transform unit, a lagrangian interpolator, and a root raised cosine filter. The digital frequency shifting unit shifts the intermediate frequency signal to a baseband; the FFT unit and the filter unit carry out frequency domain filtering, and the IFFT unit converts the frequency domain signal into a time domain signal; then, a Lagrange interpolator is adopted to realize the matching of any rate, and the output sample rate is reduced to 2 times of the symbol rate; and sending the data to baseband demodulation through a root raised cosine filter.
In a specific example, as shown in fig. 8, in a parallel structure of intermediate frequency processing of a forward variable rate receiver, parallel data sampled by an ADC is sent to a hilbert transform and frequency domain filtering unit through a digital frequency shifter, and then converted to a time domain, subjected to parallel lagrangian interpolation, reduced in rate to 2 times of symbol rate, and subjected to matched filtering to enter baseband processing.
The present embodiment adopts a structure of combining frequency domain processing and an interpolator, and can support arbitrary symbol rate reception. Whereas conventional receivers are limited by a limited set of variable symbol rates, they cannot support arbitrary symbol rate reception and have constraints on the ADC sampling rate, limiting the choice of ADC devices and sampling clocks. On the other hand, the frequency domain processing of the embodiment adopts a fast algorithm, and structurally adopts a fixed combination of an FFT processing unit, a frequency domain filtering unit, an IFFT processing unit and an interpolator unit, so that the frequency domain processing device has a simple structure and reduces the implementation complexity. The traditional method needs to support filter cascading and various downsampling combinations, and the implementation complexity is high.
In one possible implementation, the forward variable rate receiver includes a fast fourier transform unit, a first frequency domain filtering unit, a first frequency domain frequency shifting unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units; the input end of the fast Fourier transform unit receives the parallel second intermediate frequency digital signal, and the output end of the fast Fourier transform unit is connected with the input end of the first frequency domain filtering unit; the output end of the first frequency domain filtering unit is connected with the input end of the first frequency domain frequency shifting unit, and the output end of the first frequency domain frequency shifting unit is connected with the input end of the inverse fast Fourier transform unit; the output ends of the inverse fast Fourier transform units are connected with the input ends of the second Lagrange interpolation units, and the output ends of the second Lagrange interpolation units are connected with the input ends of the third time domain filtering units; and the output ends of the third time domain filtering units output the parallel second baseband signals.
In a specific example, fig. 9 shows hilbert transform and filtering processing in the frequency domain, including an FFT unit of N points, a frequency selective filtering unit, a frequency shifting unit (if the receiving front end does not use a digital frequency shifting unit), and an IFFT unit of N points. The combination of Hilbert transform and frequency domain selective filtering can filter out the image frequency while completing channel selection in the frequency domain; the frequency shift process can shift the intermediate frequency signal to the baseband; the number N of the FFT and the IFFT is set to 1024, and the range of the symbol rate 10Msps to 400Msps can be supported.
The present embodiment adopts a structure of combining frequency domain processing and an interpolator, and can support arbitrary symbol rate reception. Whereas conventional receivers are limited by a limited set of variable symbol rates, they cannot support arbitrary symbol rate reception and have constraints on the ADC sampling rate, limiting the choice of ADC devices and sampling clocks. On the other hand, the frequency domain processing of the embodiment adopts a fast algorithm, and structurally adopts a fixed combination of an FFT processing unit, a frequency domain filtering unit, an IFFT processing unit and an interpolator unit, so that the frequency domain processing device has a simple structure and reduces the implementation complexity. The traditional method needs to support filter cascading and various downsampling combinations, and the implementation complexity is high.
In a specific example, as shown in fig. 7, the bandwidth allocation of the satellite flexibly divides a plurality of channels, and the broadband receiver needs to filter adjacent channel interference through an analog front-end filter and a digital filter combination, so as to select a channel on a designated carrier; the digital filter can realize a steep transition zone and meet the requirement of adjacent channel selectivity.
In a specific example, the method of selecting frequency domain filtering according to this embodiment has a passband magnitude set to 1 and a stopband magnitude set to 0. In one possible implementation manner, the single-side passband bandwidth of the first frequency domain filtering unit is:
in the method, in the process of the invention,for the variable symbol rate; />A roll-off coefficient for the first frequency domain filtering unit; />The channel spacing protection coefficient; />Representing the channel; />Indicating that the passband magnitude is 1;
the amplitude-frequency response of the embodiment is an ideal filter characteristic, has ideal adjacent channel selection performance, and can be matched with smaller roll-off coefficients and high-efficiency frequency spectrum planning.
In one possible implementation, the step of the second lagrangian interpolation unit is:
in the method, in the process of the invention,for the variable symbol rate; />And (3) the data sampling rate after the inverse fast Fourier transform operation.
Specifically, the receiver uses an interpolator to achieve arbitrary symbol rate matching, and its parallel structure is the same as that of the transmitter parallel interpolator, as shown in fig. 6, except that the receiver uses a down rate interpolation in steps.
In a specific example, the fast fourier transform unit is a parallel processing structure. In one specific example, fig. 10 shows a parallel structure of forward receiver 1024-point FFT processing. In this embodiment, 8 parallel branches are selected, including 3 processing steps: a 128-point one-dimensional FFT; complex multiplication of phase rotation; 8-point full parallel FFT.
Specifically, each branch data path of the input end is allocated as follows: branch 0 1000: x (0), x (8), …; branch 1 1001: x (1), x (9), …; …; branch 7 1007: x (7), x (15), ….
The data distribution of each branch of the output end is as follows: branch 0, 1010: x (0), …, X (127); branch 1 1011: x (128), …, X (255); …; branch 7, 1017: x (896), …, X (1023).
In one possible implementation, the first frequency domain filtering unit isThe first frequency domain filtering unit comprises +.>A filter factor, said- >The individual filter factors are at said->The length of the parallel processing structure of the path is +.>Sequentially and parallelly arranged; the relation between the input and the output of the first frequency domain filtering unit is as follows:
in the method, in the process of the invention,multiple parallel lines generated for the fast Fourier transform unit>A plurality of frequency domain signals; />Is->A filter factor; />A filtered parallel +.>A plurality of filtered signals;。
in a specific example, as shown in fig. 11, which shows a forward receiver frequency domain parallel filtering and frequency shifting structure, 8 parallel branches may be selected for processing. Specifically, the filter factor length 1024, denoted as C (0), C (1), …, C (1023), is converted to an 8-way parallel-allocated filter factor as follows: branch 0 1100: c (0), …, C (127); branch 1 1101: c (128), …, C (255); …; branch 7, 1107: c (896), …, C (1023).
The output data sequence is: branch 0 1110: x "(0), …, X" (127); branch 1 1111: x "(128), …, X" (255); …; branch 7 1117: x "(896), …, X" (1023).
Further, the relationship between input and output is:
in the method, in the process of the invention,multiple parallel lines generated for the fast Fourier transform unit >A plurality of frequency domain signals; />Is->A filter factor; />。
In a specific example, a block diagram of 8-way 128-point FFT parallel processing is shown in fig. 12, which is the first step of 1024-point parallel FFT processing. Specifically, each branch is divided into 7 stages of processing, each stage of processing comprises butterfly operation and data exchange, the branches can keep running the processing, and the last stage of output data of each branch has a sequencing process and is sequentially output.
In one specific example, the 8 128-point FFT finger input data is assigned as follows: branch 0 1000: x (0), x (8), …; branch 1 1001: x (1), x (9), …; …; branch 7 1007: x (7), x (15), ….
The 8 128-point FFT branch output data are distributed as follows: branch 0 1210: x "(0), …, x" (127); branch 1 1211: x "(128), …, x" (255); …; 7 th branch 1217: x "(896), …, x" (1023).
In a specific example, as shown in fig. 13, the intermediate step of 1024-point parallel FFT processing is multiplied by a twiddle factor, and twiddle factors twFactor corresponding to 8 branches are respectively: branch 0 1300: w (W) 1024 0 ，W 1024 0 ，…，W 1024 0 The method comprises the steps of carrying out a first treatment on the surface of the Branch 1 1301: w (W) 1024 0 ，W 1024 1 ，…，W 1024 127 The method comprises the steps of carrying out a first treatment on the surface of the …; branch 7, 1307: w (W) 1024 0 ，W 1024 7 ，…，W 1024 889 。
The input sequence is: branch 0 1210: x "(0), …, x" (127); branch 1 1211: x "(128), …, x" (255); …; 7 th branch 1217: x "(896), …; x "(1023).
The output sequence is: branch 0 1310: x '(0), …, x' (127); branch 1 1311: x '(128), …, x' (255); …; branch 7 1317: x '(896), …, x' (1023).
In one specific example, the relationship between input and output is:
in the method, in the process of the invention,outputting data for the branches in the first step of the parallel FFT processing; />Is->A rotation factor; />。
In a specific example, a full parallel 8-point FFT process is shown in fig. 14, which is step 3 of a 1024-point parallel FFT process. Specifically, firstly, the sequence of sequential input is regulated, and the sequence of sequential input is as follows: branch 0 1310: x '(0), …, x' (127); branch 1 1311: x '(128), …, x' (255); branch 2, 1312: x '(256), …, x' (383); branch 3 1313: x '(384), …, x' (511); branch 4 1314: x '(512), …, x' (639); branch 5 1315: x '(640), …, x' (767); branch 6 1316: x '(768), …, x' (895); branch 7 1317: x '(896), …, x' (1023).
The order is exchanged, and the exchange result is: branch 0 1400: x '(0), …, x' (127); branch 1 1401: x '(256), …, x' (383); branch 2 1402: x '(512), …, x' (639); branch 3 1403: x '(768), …, x' (895); branch 4 1404: x '(128), …, x' (255); branch 5 1405: x '(384), …, x' (511); branch 6 1406: x '(640), …, x' (767); branch 7, 1407: x '(896), …, x' (1023).
Further, then, through three-stage butterfly operation, the output sequence is adjusted again, and the rotation factors of the three-stage butterfly operation comprise: a first twiddle factor 1430, a first twiddle factor of W 8 0 The method comprises the steps of carrying out a first treatment on the surface of the A second twiddle factor 1431, a second twiddle factor W 8 1 The method comprises the steps of carrying out a first treatment on the surface of the A third twiddle factor 1432, the first twiddle factor being W 8 2 The method comprises the steps of carrying out a first treatment on the surface of the A fourth twiddle factor 1433, a first twiddle factor W 8 3 . The corresponding relation between the output sequence B of the final stage of butterfly operation and the final sequence S of 8-point FFT output is as follows: b (0) =s (0); b (1) =s (4); b (2) =s (2); b (3) =s (6); b (4) =s (1); b (5) =s (5); b (6) =s (3); b (7) =s (7).
Further, the output result of the final stage of butterfly operation is: branch 0 1420: x (0), …, X (127); branch 1 1421: x (512), …, X (639); branch 2 1422: x (256), …, X (383); 3 rd branch 1423: x (768), …, X (895); branch 4, 1424: x (128), …, X (255); branch 5 1425: x (640), …, X (767); branch 6 1426: x (384), …, X (511); branch 7, 1427: x (896), …, X (1023).
Further, the final output result of the 8-point FFT is: branch 0 1410: x (0), …, X (127); branch 1 1411: x (128), …, X (255); branch 2 1412: x (256), …, X (383); branch 3 1413: x (384), …, X (511); branch 4 1414: x (512), …, X (639); branch 5 1415: x (640), …, X (767); branch 6 1416: x (768), …, X (895); branch 7 1417: x (896), …, X (1023).
In a specific example, the inverse fast fourier transform unit is a parallel processing structure.
In a specific example, as shown in fig. 15, which is a 1024-point parallel IFFT processing block diagram, the inverse FFT operation includes 3 steps: the first step is 8-point full parallel IFFT; the second step is reverse rotation; the third step is 8 paths of 128-point parallel IFFT; wherein, the functional units (1), (2) and (3) correspond to 8-point full parallel IFFT, 8-point FFT processing in figure 11 is multiplexed, and input and output of the functional units are subjected to conjugation and amplitude contraction processing; wherein the functional unit (1) divides the amplitude of the input signal by 1/8 and then obtains conjugation, namely conj (1/8); the function unit (3) is to conjugate the amplitude of the input signal, i.e. conj (1); the functional unit (4) multiplexes the rotation processing in fig. 10 in correspondence with the inverse rotation, but the inverse rotation factor takes the conjugate form of the rotation factor, i.e., conj (twFactor); the functional units (5), (6) and (7) correspond to 8 paths of 128-point parallel IFFT processing, 8 paths of 128-point parallel FFT processing in figure 9 are multiplexed, and conjugation and amplitude contraction processing are also carried out on input and output; wherein the functional unit (5) divides the amplitude of the input signal by 1/8 and then obtains conjugation, namely conj (1/8); the function unit (7) divides the amplitude of the input signal by 1/16 and then obtains conjugation, i.e., conj (1/16).
In a specific example, the data paths of each branch of the input end of the 1024-point parallel IFFT process are allocated as follows: branch 0 1110: x "(0), …, X" (127); branch 1 1111: x "(128), …, X" (255); …; branch 6 1111: x "(128), …, X" (255); branch 7 1117: x "(896), …, X" (1023).
The data distribution of each branch of the output end is as follows: branch 0 1510: x '"(0), x'" (8), …; branch 1, 1511: x '"(1), x'" (9), …; …; branch 6 1516: x '"(6), x'" (14), …; branch 7 1517: x '"(7), x'" (15), ….
In the embodiment, a half-band filter and an interpolator combination are adopted in the intermediate frequency of a forward transmitter, a frequency domain filter and an interpolator combination are adopted in a forward intermediate frequency receiver, and the intermediate frequency variable symbol rate is supported at the receiving and transmitting ends; by adopting a combination of a filter and an interpolator in a forward intermediate frequency processing system, any symbol rate and any intermediate frequency sampling rate can be supported; meanwhile, the processing method of combining a single filter and an interpolator is adopted, the structure is simple, and the implementation complexity is reduced.
In a specific example, for a transmitter, adjacent channel leakage ratio index needs to be met, and in particular, the third adjacent channel-55 dBc interference suppression requirement needs to be met. The adjacent channel interference suppression is mainly embodied in the out-of-band suppression index of the digital filter and can be obtained through the impact response of the transmitting link.
In a specific example, for a variable symbol rate intermediate frequency processing system, it is desirable to meet demodulation performance requirements, especially performance requirements under high order modulation. To illustrate the effect of the intermediate frequency processing system on demodulation performance at different symbol rates, two cases, namely low symbol rate 20Msps and high symbol rate 400Msps, were selected for 32APSK demodulation performance simulation.
In a specific example, as shown in fig. 16, the transmitter impulse response of the symbol rate 20Msps is shown, and according to the requirement that the adjacent channel leakage ratio index is greater than or equal to the third adjacent channel, the interference suppression is required to be-55 dBc, and the adjacent channel interference suppression at the far end in fig. 16 is greater than-70 dBc, so as to meet the requirement of the adjacent channel leakage ratio index of the transmitter. As shown in fig. 17, the impulse response of the transmitter with the symbol rate of 400Msps is shown, and according to the requirement that the adjacent channel leakage ratio index is greater than or equal to the third adjacent channel, the interference suppression requirement of-55 dBc is to be met, and the far-end adjacent channel interference suppression requirement in fig. 17 is greater than-60 dBc, so that the adjacent channel leakage ratio index requirement of the transmitter is met. As shown in fig. 18, the 20Msps symbol rate 32APSK includes transmit and receive full link demodulation constellations, evm=1.845%, snr=34.7 dB; the observed vector magnitude error (Error Vector Magnitude, EVM) is no greater than 2%, the reduced signal-to-noise ratio (Signal Noise Ratio, SNR) is greater than 30dB, and is far above the demodulation threshold by an index requirement of 16 dB. As shown in fig. 19, the 400Msps symbol rate 32APSK includes transmit and receive full link demodulation constellations, evm=1.991%, snr=34.0 dB; the EVM is observed to be more than 2%, the conversion SNR is more than 30dB, and the index requirement is far higher than the demodulation threshold by 16 dB. Through the simulation, the intermediate frequency processing method with the variable symbol rate can meet the requirement of the system performance index.
Another embodiment of the present invention provides a forward intermediate frequency processing method supporting a variable symbol rate, the method comprising: performing a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation and a first digital mixing parallel operation on a first baseband signal with a variable symbol rate by using a forward variable rate transmitter to generate a parallel first intermediate frequency digital signal with a first sampling rate, and transmitting the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit to perform sampling operation and generate a first intermediate frequency analog signal; performing frequency shift parallel operation, hilbert transform parallel operation, frequency domain filtering parallel operation, time domain filtering parallel operation and interpolation parallel operation on the parallel second intermediate frequency digital signals by using a forward variable rate receiver to generate parallel second baseband signals with the variable symbol rate of which the sampling rate is multiple; the second intermediate frequency digital signal is a parallel intermediate frequency digital signal which is generated by sampling operation of the received second intermediate frequency analog signal through the analog-to-digital conversion unit.
It should be noted that, the principle and the workflow of the forward intermediate frequency processing method supporting the variable symbol rate provided in this embodiment are similar to those of the forward intermediate frequency processing system supporting the variable symbol rate, and the relevant parts may be referred to the above description and will not be repeated here.
In one possible implementation, the forward variable rate receiver includes a plurality of second digital frequency shifting units, a fast fourier transform unit, a first frequency domain filtering unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units, the forward intermediate frequency processing method further comprising: receiving the parallel second intermediate frequency digital signals through a plurality of second digital frequency shifting units, and transmitting the parallel digital frequency shifting signals subjected to digital frequency shifting to the fast Fourier transform unit; performing fourier transform on the received parallel digital frequency-shifted signals by the fast fourier transform unit and transmitting the generated parallel frequency-domain signals to the first frequency-domain filtering unit; the first frequency domain filtering unit filters the parallel frequency domain signals and transmits the filtered parallel filtering signals to the inverse fast fourier transform unit; the inverse fast fourier transform unit performs inverse fourier transform on the parallel filtered signals and transmits the generated parallel time domain signals to a plurality of second lagrangian interpolation units; and the plurality of second Lagrangian interpolation units conduct interpolation operation on the parallel time domain signals, the generated parallel interpolation signals are transmitted to the plurality of third time domain filtering units, and the parallel second baseband signals are output after being filtered by the plurality of third time domain filtering units.
It should be noted that, the principle and the workflow of the forward intermediate frequency processing method supporting the variable symbol rate provided in this embodiment are similar to those of the forward variable rate receiver supporting the variable symbol rate, and the relevant parts will be referred to the above description and will not be repeated here.
In one possible implementation, the forward variable rate receiver includes a fast fourier transform unit, a first frequency domain filtering unit, a first frequency domain frequency shifting unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units, and the forward intermediate frequency processing method further includes: receiving the parallel second intermediate frequency digital signals through the fast Fourier transform unit to perform Fourier transform and transmitting the generated parallel frequency domain signals to the first frequency domain filtering unit; the first frequency domain filtering unit filters the parallel frequency domain signals and transmits the filtered parallel filtering signals to the first frequency domain frequency shifting unit; the first frequency domain frequency shifting unit shifts the frequency of the parallel filtering signals and transmits the frequency-shifted parallel digital frequency shifting signals to the inverse fast Fourier transform unit; the inverse fast fourier transform unit performs inverse fourier transform on the parallel digital frequency-shifted signals and transmits the generated parallel time domain signals to a plurality of second lagrangian interpolation units; and the plurality of second Lagrangian interpolation units conduct interpolation operation on the parallel time domain signals, the generated parallel interpolation signals are transmitted to the plurality of third time domain filtering units, and the parallel second baseband signals are output after being filtered by the plurality of third time domain filtering units.
It should be noted that, the principle and the workflow of the forward intermediate frequency processing method supporting the variable symbol rate provided in this embodiment are similar to those of the forward variable rate receiver supporting the variable symbol rate, and the relevant parts will be referred to the above description and will not be repeated here.
In the embodiment, a half-band filter and interpolator combination is adopted in a forward transmitter intermediate frequency processing method, a frequency domain filter and interpolator combination is adopted in a forward receiver intermediate frequency processing method, and intermediate frequency variable symbol rates are supported at the receiving and transmitting ends; by adopting a combination of a filter and an interpolator in the forward intermediate frequency processing method, any symbol rate and any intermediate frequency sampling rate can be supported; meanwhile, the processing method of combining a single filter and an interpolator is adopted, the structure is simple, and the implementation complexity is reduced.
It should be understood that the foregoing examples of the present invention are provided merely for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (9)

1. A forward intermediate frequency processing system supporting variable symbol rates, the system comprising
A forward variable rate transmitter for performing a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation, and a first digital mixing parallel operation on a first baseband signal having a variable symbol rate to generate a parallel first intermediate frequency digital signal having a first sampling rate, and transmitting the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit to perform a sampling operation and generate a first intermediate frequency analog signal;
a forward variable rate receiver for performing a frequency shift parallel operation, a hilbert transform parallel operation, a frequency domain filtering parallel operation, a time domain filtering parallel operation, and an interpolation parallel operation on a parallel second intermediate frequency digital signal to generate a parallel second baseband signal having a sampling rate that is multiple of the variable symbol rate; the second intermediate frequency digital signal is an intermediate frequency digital signal generated by sampling the received second intermediate frequency analog signal through an analog-to-digital conversion unit;
The forward variable rate transmitter comprises a first rate interpolation unit and at least one parallel branch, wherein each parallel branch comprises a first root raised cosine filter unit, a plurality of second rate interpolation units, a plurality of first half-band filter units, a plurality of first Lagrange interpolation units and a plurality of first digital frequency shifting units, wherein the first half-band filter units, the first Lagrange interpolation units and the first digital frequency shifting units are in one-to-one correspondence with the second rate interpolation units; wherein the method comprises the steps of
The input end of the first rate interpolation unit receives the first baseband signals, and the output end of the first rate interpolation unit is connected with the input end of each first root raised cosine filter unit;
the output end of each first root raised cosine filter unit is connected with the input end of each second rate interpolation unit of the corresponding branch respectively, and the output end of each second rate interpolation unit is connected with the input end of the corresponding first half-band filter unit;
the output end of each first half-band filtering unit is connected with the input end of each first Lagrangian interpolation unit of the corresponding branch respectively, and the output end of each first Lagrangian interpolation unit is connected with the input end of the corresponding first digital frequency shifting unit;
And the output ends of the plurality of first digital frequency shifting units output the parallel first intermediate frequency digital signals.
2. The forward intermediate frequency processing system of claim 1, wherein,
the step of the first Lagrange interpolation unit is that
In the method, in the process of the invention,for the variable symbol rate; />Is the sampling rate of the digital-to-analog conversion unit.
3. The forward intermediate frequency processing system of claim 1, wherein,
the forward variable rate receiver comprises a plurality of second digital frequency shifting units, a fast Fourier transform unit, a first frequency domain filtering unit, an inverse fast Fourier transform unit, a plurality of second Lagrangian interpolation units and a plurality of third time domain filtering units; wherein the method comprises the steps of
The input ends of the plurality of second digital frequency shifting units receive the parallel second intermediate frequency digital signals, and the output ends of the plurality of second digital frequency shifting units are connected with the input ends of the fast Fourier transform units;
the output end of the fast Fourier transform unit is connected with the input end of the first frequency domain filtering unit, and the output end of the first frequency domain filtering unit is connected with the input end of the inverse fast Fourier transform unit;
The output ends of the inverse fast Fourier transform units are connected with the input ends of the second Lagrange interpolation units, and the output ends of the second Lagrange interpolation units are connected with the input ends of the third time domain filtering units;
and the output ends of the third time domain filtering units output the parallel second baseband signals.
4. The forward intermediate frequency processing system of claim 1, wherein,
the forward variable rate receiver comprises a fast Fourier transform unit, a first frequency domain filtering unit, a first frequency domain frequency shifting unit, an inverse fast Fourier transform unit, a plurality of second Lagrangian interpolation units and a plurality of third time domain filtering units; wherein the method comprises the steps of
The input end of the fast Fourier transform unit receives the parallel second intermediate frequency digital signal, and the output end of the fast Fourier transform unit is connected with the input end of the first frequency domain filtering unit;
the output end of the first frequency domain filtering unit is connected with the input end of the first frequency domain frequency shifting unit, and the output end of the first frequency domain frequency shifting unit is connected with the input end of the inverse fast Fourier transform unit;
the output ends of the inverse fast Fourier transform units are connected with the input ends of the second Lagrange interpolation units, and the output ends of the second Lagrange interpolation units are connected with the input ends of the third time domain filtering units;
And the output ends of the third time domain filtering units output the parallel second baseband signals.
5. The forward intermediate frequency processing system of claim 3 or 4, wherein,
the single-side passband bandwidth of the first frequency domain filtering unit is
In the method, in the process of the invention,for the variable symbol rate; />A roll-off coefficient for the first frequency domain filtering unit; />The channel spacing protection coefficient; />Representing the channel; />Indicating that the passband magnitude is 1;
the step of the second Lagrange interpolation unit is that
In the method, in the process of the invention,for the variable symbol rate; />And (3) the data sampling rate after the inverse fast Fourier transform operation.
6. The forward intermediate frequency processing system of claim 4, wherein,
the first frequency domain filtering unit isThe first frequency domain filtering unit comprises +.>A filter factor, said->The individual filter factors are at said->The length of the parallel processing structure of the path is +.>Sequentially and parallelly arranged; wherein the method comprises the steps of
The relation between the input and the output of the first frequency domain filtering unit is that
In the method, in the process of the invention,multiple parallel lines generated for the fast Fourier transform unit>A plurality of frequency domain signals; />Is->A filter factor; / >A filtered parallel +.>A plurality of filtered signals;。
7. a method for forward intermediate frequency processing supporting variable symbol rates, the method comprising
Performing a first rate interpolation operation, a first time domain filtering parallel operation, a second rate interpolation parallel operation, a second time domain filtering parallel operation, a third rate interpolation parallel operation and a first digital mixing parallel operation on a first baseband signal with a variable symbol rate by using a forward variable rate transmitter to generate a parallel first intermediate frequency digital signal with a first sampling rate, and transmitting the parallel first intermediate frequency digital signal to a digital-to-analog conversion unit to perform sampling operation and generate a first intermediate frequency analog signal;
performing frequency shift parallel operation, hilbert transform parallel operation, frequency domain filtering parallel operation, time domain filtering parallel operation and interpolation parallel operation on the parallel second intermediate frequency digital signals by using a forward variable rate receiver to generate parallel second baseband signals with the variable symbol rate of which the sampling rate is multiple; the second intermediate frequency digital signal is a parallel intermediate frequency digital signal which is generated by sampling the received second intermediate frequency analog signal through an analog-to-digital conversion unit;
The forward variable rate transmitter comprises a first rate interpolation unit and at least one parallel branch, wherein each parallel branch comprises a first root raised cosine filter unit, a plurality of second rate interpolation units, a plurality of first half-band filter units, a plurality of first Lagrange interpolation units and a plurality of first digital frequency shifting units, wherein the first half-band filter units, the first Lagrange interpolation units and the first digital frequency shifting units are in one-to-one correspondence with the second rate interpolation units; wherein the method comprises the steps of
The input end of the first rate interpolation unit receives the first baseband signals, and the output end of the first rate interpolation unit is connected with the input end of each first root raised cosine filter unit;
the output end of each first root raised cosine filter unit is connected with the input end of each second rate interpolation unit of the corresponding branch respectively, and the output end of each second rate interpolation unit is connected with the input end of the corresponding first half-band filter unit;
the output end of each first half-band filtering unit is connected with the input end of each first Lagrangian interpolation unit of the corresponding branch respectively, and the output end of each first Lagrangian interpolation unit is connected with the input end of the corresponding first digital frequency shifting unit;
And the output ends of the plurality of first digital frequency shifting units output the parallel first intermediate frequency digital signals.
8. The method of forward intermediate frequency processing according to claim 7, wherein,
the forward variable rate receiver includes a plurality of second digital frequency shifting units, a fast fourier transform unit, a first frequency domain filtering unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units, and a plurality of third time domain filtering units, and the forward intermediate frequency processing method further includes:
receiving the parallel second intermediate frequency digital signals through a plurality of second digital frequency shifting units, and transmitting the parallel digital frequency shifting signals subjected to digital frequency shifting to the fast Fourier transform unit;
performing fourier transform on the received parallel digital frequency-shifted signals by the fast fourier transform unit and transmitting the generated parallel frequency-domain signals to the first frequency-domain filtering unit;
the first frequency domain filtering unit filters the parallel frequency domain signals and transmits the filtered parallel filtering signals to the inverse fast fourier transform unit;
the inverse fast fourier transform unit performs inverse fourier transform on the parallel filtered signals and transmits the generated parallel time domain signals to a plurality of second lagrangian interpolation units;
And the plurality of second Lagrangian interpolation units conduct interpolation operation on the parallel time domain signals, the generated parallel interpolation signals are transmitted to the plurality of third time domain filtering units, and the parallel second baseband signals are output after being filtered by the plurality of third time domain filtering units.
9. The method of forward intermediate frequency processing according to claim 7, wherein,
the forward variable rate receiver comprises a fast fourier transform unit, a first frequency domain filtering unit, a first frequency domain frequency shifting unit, an inverse fast fourier transform unit, a plurality of second lagrangian interpolation units and a plurality of third time domain filtering units, and the forward intermediate frequency processing method further comprises:
receiving the parallel second intermediate frequency digital signals through the fast Fourier transform unit to perform Fourier transform and transmitting the generated parallel frequency domain signals to the first frequency domain filtering unit;
the first frequency domain filtering unit filters the parallel frequency domain signals and transmits the filtered parallel filtering signals to the first frequency domain frequency shifting unit;
the first frequency domain frequency shifting unit shifts the frequency of the parallel filtering signals and transmits the frequency-shifted parallel digital frequency shifting signals to the inverse fast Fourier transform unit;
The inverse fast fourier transform unit performs inverse fourier transform on the parallel digital frequency-shifted signals and transmits the generated parallel time domain signals to a plurality of second lagrangian interpolation units;
and the plurality of second Lagrangian interpolation units conduct interpolation operation on the parallel time domain signals, the generated parallel interpolation signals are transmitted to the plurality of third time domain filtering units, and the parallel second baseband signals are output after being filtered by the plurality of third time domain filtering units.
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