System and method for signal retransmission

Abstract

To provide a new method and system for signal retransmission.SOLUTION: A signal effect processor includes a plurality of sub-band processors and a summer. A channelizer receives a sampled intermediate frequency signal indicating a first sampling rate. The channelizer generates a plurality of sub-band signals, each associated with respective sub-bands of the intermediate frequency signal. Each sub-band signal indicates a second sampling rate lower than the first sampling rate. Each of at least one selected sub-band processor receives respective sub-band signals, introduces at least one effect to the respective sub-band signals, increases the sampling rate of the respective sub-band signals to the first sampling rate, and generates respective affected sub-band retransmission signals. The respective affected sub-band retransmission signals are provided to respective inputs of the summer.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The disclosed technology generally relates to transceivers, and more particularly to methods and systems for effecting a signal to be retransmitted.

Background Art

[0002] In the art, it is known to retransmit a signal having a jamming effect using a digital radio frequency memory (DRFM). Generally, the DRFM records the received signal, the jamming processor effects a jamming effect (e.g., delay, amplitude modulation, phase modulation, Doppler effect), and the modified signal is retransmitted towards the source. If the signal is a radar signal, the radar receiving the modified signal will generate incorrect indications regarding the position and Doppler frequency of the object (e.g., aircraft) using the DRFM. One drawback of DRFM systems is that such systems operate with a bandwidth wider than the bandwidth of the signal or signals of interest. In other words, DRFM systems known in the art operate in a band that does not necessarily include the signal of interest.

[0003] The publication entitled "Design and Application of DRFM System Based on Digital Channelized Reciever" by Wang Zongbo et al. relates to a DRFM system used for jamming signal modulation. In this system by Wang Zongbo et al., a digital channelized receiver is added between an analog-to-digital converter (ADC) and a memory. The ADC sampling frequency corresponds to the instantaneous bandwidth of the received signal. The channelized receiver divides the instantaneous bandwidth of the received signal into D uniform sub-channels, each sub-channel covering the bandwidth evenly. The channelized receiver also provides the number of channels used to set the transmission frequency. Since the received signal is channelized into D channels, the data flow rate is 1 / D of the sampling frequency. If f s is the sampling frequency, then fs Each sub-channel's digital-to-analog converter, having a conversion speed of / D, converts the jamming modulation signal into an analog signal. The converted signal is up-converted according to each transmission frequency determined by that sub-channel.

[0004] U.S. Patent No. 6,473,474 to Wiegand, entitled "Wide Band Alias resolving digitally Channelized reciever and a Memory for Use Therewith", relates to a channelized wideband receiver that divides a wide frequency band into channels such that signals within each channel are individually sensed or modulated. Wiegand's publication relates to addressing the problem of different operating clock rates between a digital signal processor (DSP) that performs channelization and filtering and converters (i.e., analog-to-digital and digital-to-analog). To that end, Wiegand's publication proposes a DSP that uses a demultiplexer that separates signals into a plurality of channels, a filter that filters and phase-shifts the separated signals, and an adder that sums the filtered signals. SUMMARY OF THE INVENTION

[0005] The objective of the disclosed technology is to provide a novel method and system for signal retransmission. According to an aspect of the disclosed technology, a system for signal retransmission is provided. This system includes a channelizer, a signal effect processor, and a controller. The signal effect processor is coupled to the channelizer. The controller is coupled to the channelizer and the signal effect processor. The signal effect processor includes a plurality of sub-band processors and an adder. The channelizer is configured to receive a sampled intermediate frequency signal. The sampled intermediate frequency signal indicates a first sampling rate. The channelizer is further configured to generate a plurality of sub-band signals. Each sub-band signal is associated with a respective sub-band of the sampled intermediate frequency signal. Each sub-band signal indicates a second sampling rate that is lower than the first sampling rate. Each of at least one selected sub-band processor is configured to receive a respective sub-band signal, apply at least one effect to the respective sub-band signal, and increase the sampling rate of the respective sub-band signal to the first sampling rate, thereby generating a respective affected sub-band retransmission signal. Each of at least one selected sub-band processor is further configured to provide the respective affected sub-band retransmission signal to a respective input of the adder. The adder is configured to sum its inputs and generate an affected wideband retransmission signal. The controller is configured to select at least one selected sub-band processor and control the setting of at least one effect.

[0006] According to another aspect of the disclosed technology, a method for signal retransmission is provided. The method includes procedures for determining a plurality of sub-band signals each associated with a respective sub-band of a sampled received intermediate frequency signal. The sampled received intermediate frequency signal indicates a first sampling rate. Each sub-band signal indicates a second sampling rate lower than the first sampling rate. The method also includes procedures for generating an affected sub-band signal for each of at least one target sub-band by bringing at least one selected effect to each respective sub-band signal for each of at least one target sub-band. The method further includes procedures for increasing the sampling rate of each affected sub-band signal to the first sampling rate to generate at least one affected sub-band retransmission signal, and procedures for summing all the affected sub-band retransmission signals to generate an affected broadband retransmission signal.

[0007] The disclosed technology will be more fully understood and recognized from the following detailed description presented together with the drawings.

Brief Description of the Drawings

[0008]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Modes for Carrying Out the Invention

[0009] The disclosed technology overcomes the drawbacks of the prior art by providing a system and method for signal retransmission that utilizes the sparsity of the reception bandwidth. In other words, since the reception bandwidth is sparse, it is not necessarily required to process the entire reception bandwidth, and it is sufficient to process only the selected subbands where the signals exist. According to the disclosed technology, a wideband reception IF (Intermediate Frequency) signal is sampled. However, only the selected subbands of the wideband reception IF signal that exhibit a narrow (i.e., narrow compared to the bandwidth of the wideband reception IF signal) bandwidth are processed. As a result, the processing requirements (e.g., processing time, power consumption) are lower compared to the case where the entire bandwidth of the wideband IF signal is processed.

[0010] Here, refer to FIGS. 1A, 1B, and 1C, which are schematic diagrams of a system for signal retransmission generally referred to as 100, configured and operable in accordance with an embodiment of the disclosed technology. Generally, system 100 receives a wideband IF signal (e.g., a radar signal or a communication signal), introduces various jamming effects (e.g., delay, amplitude modulation, frequency modulation), and retransmits the affected signal.

[0011] System 100 includes an analog-to-digital converter (ADC) 102, a channelizer 104, a controller 105, a signal effect processor 106, and a digital-to-analog converter (DAC) 108. Signal effect processor 106 includes a plurality of subband signal effect processors 1101, 1102, ···, 110 M and an adder 112. Each of subband processors 1101, 1102, ···, 110 M includes respective subband signal effect processors 1141, 1142, ···, 114 M and respective interpolators 1161, 1162, ···, 116 M .

[0012] Subband signal effect processors 1141, 1142, ···, 114 MEach of the inputs is combined with the output of the channelizer 104 and the sub-band signal effect processors 1141, 1142, ···, 114 M Each of the outputs is combined with the inputs of the respective interpolators 1161, 1162, ···, 116 M is combined with the inputs of the interpolators 1161, 1162, ···, 116 M The outputs of the interpolators 1161, 1162, ···, 116 are combined with the inputs of the adder 112. The input of the channelizer 104 is combined with the output of the ADC 102. The output of the adder 112 is combined with the input of the DAC 108. The controller 105 is coupled to the channelizer 104 and the signal effect processor 106.

[0013] The ADC 102 receives a wideband IF signal from an RF front end (not shown) and samples the received wideband IF signal at respective sampling rates as determined by the sampling theorem and additional system requirements and constraints (such as guard bands, system clock frequency, availability of the sampler, etc.). The ADC 102 generates a sampled wideband IF signal 120. The ADC 102 provides the sampled wideband IF signal 120 to the channelizer 104. Referring to FIG. 1B, the channelizer 104 generates a spectrogram 124 of the sampled wideband IF signal 12 0 The spectrogram 124 may be continuous or finite. To generate the spectrogram 124, the channelizer 104 determines the frequency representation of each group of N samples (using, for example, the fast Fourier transform, FFT algorithm), and consecutive sample groups 1221, 1222, 1223, ···, 122 i , ··· (i.e., each of the N samples) includes overlapping samples (i.e., the first v samples in sample group 122 i are the same as the last v samples in sample group 122 i-1the last v samples in (where v represents a number). In other words, v is the number of samples that overlap between two consecutive frames. The term N / v (i.e., the quotient of N divided by v) is referred to as the "overlap factor" in this specification. Thus, the channelizer 104 generates a plurality of frequency representation vectors, and each such frequency representation vector contains N / 2 frequency bins (N / 2 due to the conjugate symmetry of the Fourier transform). The frequency bins are also referred to as subbands in this specification. Also, each frequency representation vector is associated with a respective time tag. Each entry within the frequency representation vector is in the form of X n k where k represents the subband and n represents the time tag (i.e., the superscript is related to the bin number and the subscript is related to time). For example, the channelizer 104 generates frequency representation vectors X1 1 X1 2 X1 3 ··· X1 N / 2 which are the first instances within each sample group 1221 respectively. The channelizer 104 generates frequency representation vectors X2 1 X2 2 X2 3 ··· X2 N / 2 which are the second time instances within each sample group 1222 respectively. It should be noted that each entry within the frequency representation vector is a complex number (resulting from the conversion from time to frequency). In other words, the spectrogram is a function of time and frequency, typically a discrete function. Generally, the spectrogram is determined using a short-time FFT (SFFT), a generalized sliding FFT, a sliding discrete Fourier transform (SDFT), or by a bank of time filters using decimation.

[0014] The channelizer 104 is connected to each one of subband processors 1101, 1102, ···, 110 M (i.e., subband processors 1101, 1102, ···, 110 M1101, 1102, . . . , 1104, 1105, 1106, 1107, 1108, 1109, 1200, 1201, 1202, 1203, 1204, 1205, 1206, 1207, 1208, 1209, 1300, 1310 M The number M of frequency bins is less than or equal to N / 2 (i.e., M≦N / 2, where N / 2 is the number of frequency bins). A subband signal is defined by a stream of k-th entries of successive frequency representation vectors. For example, entry X1 in spectrogram 124 1 , X2 1 , X3 1 , , X i 1 , . . . define the subband signal associated with the first subband (i.e., subband 1), and the entry X1 in the spectrogram 124 2 , X2 2 , X3 2 , , X i 2 , ··· define the subband signal associated with the second subband (i.e., subband 2). Thus, each subband signal is associated with a respective kth subband of the bandwidth of the IF signal. Also, since each entry in the frequency representation vector is a complex number, the values ​​of the subband signals are also complex numbers. The sample rate of each subband signal is

number

[0015] Generally, only a part of the bandwidth of the wideband IF signal 120 contains the target signal or a plurality of target signals. Therefore, only the sub-band signals corresponding to the bandwidths of these target signals are provided to each of the sub-band signal effect processors 1141, 1142, ···, 114 M of each one. In other words, only the selected part of the bandwidth of the IF signal (i.e., the target sub-band) is processed. In a special case where M = N / 2, each sub-band signal associated with the selected k-th sub-band can be assigned to the corresponding k-th sub-band signal effect processor. Generally, the selection of the sub-band signals and their assignment to each signal effect processor are controlled by the controller 105. The controller 105 utilizes the spatial sparsity of the received IF signal. For example, the controller 105 may have prior information related to the target sub-band. Alternatively or additionally, the controller 105 may assign only the sub-band signals whose amplitudes exceed a predetermined threshold.

[0016] In each of the selected sub-band processors 1101, 1102, ···, 110 M each of the sub-band signal effect processors 1141, 1142, ···, 114 M brings about the respective selected effects to the corresponding sub-band signals provided thereto, generating the affected sub-band signals. These effects are, for example, one of delay, amplitude modulation, phase modulation, and Doppler effect, or any combination thereof. Referring to FIG. 1C, a typical implementation of the sub-band signal processor 110 k is shown. The sub-band processor 110 k includes an interpolator 116 k and a sub-band signal effect processor 114 k coupled to a mixer 144 k . The sub-band signal effect processor 114 k includes a delay 130 k (e.g., a delay line), a phase shifter 132 k , an ortho-polarity converter 134 k , and an amplifier 136 kincludes the phase shifter 132 k is a direct digital synthesizer (DDS) 138 k and the mixer 140 k includes the interpolator 116 k has a cosine look-up table (LUT) 142 k includes the delay 130k and the DDS 138 k is connected to the input of the mixer 140 k The output of the mixer 140 k is connected to the input of the quadrature polar converter 134 k The phase output of the quadrature polar converter 134 k is connected to the input of the interpolator 116K, and the amplitude output of the quadrature polar converter 134 k is connected to the input of the amplitude modulator 136 k The output of the interpolator 116 k and the output of the amplitude modulator 136 k are connected to the respective inputs of the mixer 144 k Note that the controller 105 also controls the settings of the effects (i.e., the duration of the delay, the level of the amplitude modulation, the phase modulation, and the amount of the Doppler shift) brought about by each of the sub-band signal effect processors 1141, 1142, ···, 114 M

[0017] The delay 130 k receives the sub-band signal and provides each sub-band signal with a respective delay. The delay 130 k can be implemented as a buffer memory in which the sub-band signal is stored for a certain period. The delay 130 k provides the delayed sub-band signal to the phase shifter 132 k In the phase shifter 132 k the mixer 140 k mixes the delayed sub-band signal with the selected digital synthesis signal and frequency and / or phase modulates the delayed sub-band signal. The frequency modulation can also be used to provide a Doppler shift to the sub-band signal. The phase shifter 132 k provides the frequency and / or phase modulation signal to the quadrature polar converter 134 k ​is provided to the orthogonal polar converter 134 k converts the complex numerical values of the received sub-band signals from the orthogonal form (i.e., x + iy) to the polar form (i.e., the amplitude and phase values). The orthogonal polar converter 134 k provides the phase value to the interpolator 116k and the amplitude value to the amplifier 136k. The amplifier 136 k amplifies the amplitude of the sub-band signal (i.e., amplitude modulation) and provides the amplified amplitude value of the sub-signal to the mixer 144 k is provided to.

[0018] The interpolator 116 k increases the sampling frequency of each sub-band signal back to the sampling frequency of the ADC 102. Here, it is recalled that the sample rate of each sub-band signal is the "overlap factor" / N of the sample rate of the sampled broadband IF signal. For this purpose, for each difference between consecutive pairs of phase values, the interpolator 116 k generates a sampled sine wave containing N / "overlap factor" (i.e., the quotient of N divided by the overlap factor) samples at a frequency corresponding to the difference between consecutive phase values. The interpolator 116 k uses the cosine LUT 142 k to generate this sampled sine wave. The interpolator 116 k provides the sampled sine wave to the mixer 144 k is provided to.

[0019] The mixer 144 k multiplies the sine wave samples by the amplitude value from the amplifier 136 k to generate the sub-band retransmission signals affected by the k-th sub-band, each called the affected k-th sub-band retransmission signal. The mixer 144 k provides the affected k-th sub-band retransmission signals to the respective inputs of the adder 112. The adder 112 sums the inputs accordingly. Therefore, the adder 112 sums the sub-band retransmission signals affected by the relevant sub-band signal effect processors 1141, 1142, ···, 114 M to generate the affected broadband retransmission signal.

[0020] As described above, one of the selected ones among the sub-band processors 1101, 1102, ···, 110 M processes each of the sub-band signals provided thereto, and the number of samples processed per second (also referred to as the sample processing rate) by each selected one of the signal effect processors 1101, 1102, ···, 110 M is smaller than the sample rate of the sampled wideband IF signal 120 generated by the ADC 102 by N / “overlap factor”. Therefore, the processing requirements (i.e., power consumption and processing speed) of the signal effect processor 106 are reduced as compared with the processing requirements when processing all of the bandwidths of the received wideband IF signal. Also, since the adder 112 generates a single signal at the sample rate of the sampled wideband IF signal, there is no need to modify the DAC 108 or use a DAC for each sub-band. In other words, the system according to the disclosed technology can be used in place of an existing DRFM system without modifying the operating rates of the ADC and DAC of the existing system.

[0021] The system 100 can be implemented using individual components in an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), or a general purpose computer. When implemented with a DSP or a general purpose computer, the system 100 includes a memory for storing machine-readable instructions configured to be executed by the DSP or the general purpose computer.

[0022] Now, refer to FIG. 2 which is a schematic diagram of a method for signal retransmission operable in accordance with another embodiment of the disclosed technology. In procedure 200, the received wideband IF signal is sampled at respective sampling rates. Referring to FIG. 1A, an ADC samples the wideband IF signal.

[0023] In procedure 202, a plurality of frequency representation vectors are determined from successive sample groups, each group including N samples of the sampled wideband IF signal. These frequency representation vectors are determined, for example, by performing a Fourier transform. Generally, the entries of these frequency representation vectors are complex numbers. Referring to FIGS. 1A and 1B, the channelizer 104 determines a plurality of frequency representation vectors.

[0024] In procedure 204, a plurality of subband signals are determined from the frequency representation vectors. Each subband signal is defined by a stream of the k-th entries of successive frequency representation vectors. Thus, each subband signal is associated with the k-th subband of the bandwidth of the IF signal. Also, since each entry within the frequency representation vector is a complex number, the values of the subband signals are also complex numbers. Further, the sample rate of each subband signal is the "oversampling factor" / N of the sampled wideband IF signal (since each of these entries is determined from a group of N samples). Thus, the sample rate of each subband signal is lower than the sample rate of the sampled wideband IF signal. Referring to FIGS. 1A and 1B, the channelizer 104 determines the subband signals from the k-th entries X1 k , X2 k , X3 k , ···, X i k , ···, of each successive frequency representation vector.

[0025] In procedure 206, for each of at least one selected sub - band of interest, by causing at least one selected effect to be brought to each sub - band signal, a sub - band signal affected for each of at least one sub - band of interest is generated. This effect or effects are, for example, at least one of delay, amplitude modulation, phase modulation, and Doppler effect, or any combination thereof. The effect or effects brought to each sub - band signal do not have to be the same as the effect or effects brought to other sub - band signals. For example, the effect brought to one sub - band signal is only delay, while the effects brought to other sub - band signals are delay and Doppler effect, and the effects brought to other sub - band signals are delay, amplitude modulation, and Doppler effect. Referring to FIG. 1A, the controller 105 selects one or more of the sub - band processors 1101, 1102, ···, 110 M corresponding to at least one selected sub - band of interest. The selected one or more of the sub - band processors 1101, 1102, ···, 110 M bring about the respective effects to be brought to each sub - band signal.

[0026] In procedure 208, the sample rate of each affected sub - band signal is increased to the sampling rate of the received wide - band IF signal in order to generate each affected sub - band re - transmission signal. The sample rate is increased, for example, by generating N / “overlap factor” samples of a sine wave of a frequency corresponding to the phase difference between two consecutive samples of the corresponding affected sub - band signal for each affected sub - band signal. Referring to FIG. 1A, the interpolator 116 increases the sampling rate of each sub - band signal.

[0027] In step 210, in order to generate an affected wideband retransmission signal, all (i.e., one or more) affected sub-band retransmission signals are summed. Referring to FIG. 1A, adder 112 sums the sub-band retransmission signals affected by the associated sub-band signal effect processors 1141, 1142, ···, 114 M to generate an affected wideband retransmission signal. It should be noted that step 210 is only performed when a plurality of affected sub-band retransmission signals are generated.

[0028] As will be understood by those skilled in the art, the disclosed technology is not limited to what is specifically illustrated and described herein. The scope of the disclosed technology is defined only by the following claims.

Claims

1. A system (100) for signal retransmission, comprising a channelizer (104), a signal effects processor (106), and a controller (105), The channelizer (104) comprises: configured to receive a sampled wideband intermediate frequency (IF) signal exhibiting a first sampling rate; and configured to generate a plurality of subband signals, each subband signal associated with a respective subband of the sampled wideband IF signal, each subband signal exhibiting a second sampling rate lower than the first sampling rate; The signal effects processor (106) is coupled to the channelizer (104), the signal effects processor (106) including a plurality of sub-band processors (114). １ , 114 ２ …114 Ｍ ) and an adder (112), each of the at least one selected sub-band processor comprising: receiving the subband signals; applying at least one effect to said subband signals thereby generating affected subband signals; increasing the sampling rate of the affected subband signal to the first sampling rate, thereby generating an affected subband retransmission signal; and configured to provide the affected subband retransmission signal to the adder (112); The controller (105) is coupled to the channelizer (104) and the signal effects processor (106), the controller (105) comprising: configured to select the at least one selected sub-band processor and to control a setting of the at least one effect; the adder (112) is configured to sum the affected subband retransmission signals from each of the at least one selected subband processor to generate a wideband affected retransmission signal; the system is configured to process selected subbands of the sampled wideband IF signal. system.

2. Each of said sub-band processors comprises a sub-band signal effects processor (110 １ , 110 ２ , … 110 Ｍ ) and an interpolator (116 １ , 116 ２ , … 116 Ｍ ), the subband signal effects processor is configured to apply the at least one effect to the subband signals; The system of claim 1 , wherein the interpolator is configured to increase the sampling rate of the subband signal to the first sampling rate.

3. The above-mentioned effects are as follows: Frequency modulation, Amplitude modulation, Phase modulation, Doppler effect, and delay The system of claim 2 , wherein the

4. The subband signal effects processor comprises: a delay (130) configured to introduce a delay into the subband signals; a phase shifter (132) coupled to the delay and configured to provide a phase shift corresponding to at least one of frequency modulation, phase modulation, and the Doppler effect; a quadrature-polar converter (134) coupled to the phase shifter and configured to convert received complex values ​​of the subband signals from a quadrature form to a polar form; an amplifier (136) coupled to the quadrature polar converter and configured to amplify the amplitude of the subband signal; The system of claim 2 , comprising:

5. The channelizer generates the subband signal by generating a plurality of frequency representation vectors, each frequency representation vector including a plurality of subbands and associated with a time tag; The system of claim 1 , wherein a kth entry of the frequency representation vector in succession defines a subband signal.

6. The channelizer comprises: Short-time Fast Fourier Transform, Generalized sliding fast Fourier transform, Sliding Discrete Fourier Transform, and Bank of temporal filters using decimation - Patent Application 20070123633 The system of claim 1 , further comprising:

7. A method for signal transmission, comprising the steps of: determining (202) a plurality of subband signals each associated with a subband of a sampled received spreadband intermediate frequency (IF) signal, the sampled received spreadband IF signal exhibiting a first sampling rate and each subband signal exhibiting a second sampling rate lower than the first sampling rate; selecting at least one subband processing from the plurality of subbands; for each of at least one selected subband, applying at least one selected effect to said subband signal, thereby generating an affected subband signal; increasing (208) a sample rate of each affected subband signal to said first sampling rate to generate at least one affected subband retransmission signal; summing (210) all affected sub-band retransmission signals to generate an affected wideband retransmission signal; Inclusive of A method comprising processing selected subbands of the sampled spreadband IF signal.

8. The at least one selected effect is: Frequency modulation, Amplitude modulation, Phase modulation, Doppler effect, and delay The method of claim 7, wherein the method is one of:

9. determining (202) a plurality of frequency representation vectors from each sample group of the sampled received wideband IF signal, prior to the step of determining the plurality of subband signals; The method of claim 7 , wherein the kth consecutive entry of the frequency representation vector defines a subband signal.

10. 10. The method of claim 9, further comprising the step of sampling (200) the received wideband IF signal at the first sampling rate prior to the step of determining the plurality of frequency representation vectors.

11. The subband signal is Short-time Fast Fourier Transform, Generalized sliding fast Fourier transform, Sliding Discrete Fourier Transform, and Bank of temporal filters using decimation - Patent Application 20070123633 The method of claim 7, wherein the determination is made by using one of the following:

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