CN115567125A - Multichannel calibration and signal coherent recovery method and device for broadband channelization reception - Google Patents
Multichannel calibration and signal coherent recovery method and device for broadband channelization reception Download PDFInfo
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Abstract
The invention provides a method and a device for multi-channel calibration and signal coherent recovery of broadband channelized reception, wherein the method comprises the following steps: generating a reference signal which is coherent with the multi-path channelized local oscillator signals; recording N paths of first intermediate frequency signals obtained after the channelized receiver is processed; acquiring the phase of a reference signal at the receiving starting moment of the intermediate frequency signal; calculating the amplitude-frequency response and the phase-frequency response of each channel of the channelized receiver by using the time domain calibration result and the N paths of intermediate frequency signals; recording the intermediate frequency signals obtained by each channel, and acquiring the phase of the reference signal at the receiving start time of the intermediate frequency signals; calculating phases to be compensated of each channel in signal coherent recovery; and correcting the intermediate frequency signal, performing frequency shift processing on the intermediate frequency signal, and then superposing the intermediate frequency signal to complete the phase-coherent recovery of the broadband signal. The invention provides a method and a device for multi-channel calibration and signal coherent recovery of broadband channelized reception, which meet the digital receiving requirement of large instantaneous bandwidth arbitrary waveform signals.
Description
Technical Field
The invention belongs to the field of broadband radio frequency receiving, and relates to a method and a device for multichannel calibration and signal coherent recovery of broadband channelized reception.
Background
Digital reception of broadband arbitrary waveform signals is a key technology of a multifunctional integrated radio frequency system. According to the nyquist sampling theorem, the sampling rate of an analog-to-digital converter (ADC) must be at least twice the bandwidth of the signal in order to recover the signal without distortion. At the same time, the sample-and-hold front-end of the ADC also needs to have sufficient bandwidth to cover the entire signal spectrum. However, since the existing ADC has bottlenecks in both sampling rate and analog bandwidth, the wideband signal should be preprocessed to match parameters such as bandwidth and frequency band of the processed signal with the index of the ADC. A more effective method for preprocessing broadband signals is to divide broadband signals into a plurality of sub-bands with narrower bandwidths, and each band is down-converted to an intermediate frequency by local oscillation signals with different frequencies respectively. This method is a channelized reception technique for broadband signals.
At present, the channelization of wideband signals has been studied more in terms of hardware implementation, and the reported implementation approaches include radio frequency filter bank in combination with coherent multiple local oscillators [ Gompers, wei seal, li Xiang.
The research and validation around these schemes mainly focuses on the splitting and down-conversion of the wideband signal, and there are two problems to be solved in the splicing of multiple channels and the reconstruction of the wideband signal:
first, the amplitude-phase response measurement problem of the channelized down-conversion channel. The channelized down-conversion channel relates to three aspects of a radio frequency domain, an intermediate frequency domain and a digital domain, belongs to a complex mixed network, and is difficult to directly measure amplitude, particularly phase response, in the frequency domain. Although the vector mixing measurement option in the high-end multiport network analyzer can realize the frequency domain measurement of the radio frequency filtering and down-conversion module, the amplitude-phase response of the sampling holding front end in the ADC chip can not be directly measured due to the closed structure of the chip. The frequency sweep excitation is carried out by utilizing the dot frequency source, and the measurement of the amplitude-frequency response of the link can be realized by a method of recording the amplitude of a signal obtained by the ADC. However, due to the randomness of the phases of different output signals during the frequency sweeping process and the randomness of the instantaneous phase of the local oscillator, the method cannot effectively measure the phase-frequency response of the channelized link.
Second, the problem of coherence between multiple channels. Due to uncertainty of arrival time of the signals to be processed, even if coherent multifrequency local oscillation is adopted, extra phase shift is still introduced into the processed signals by random local oscillation time delay, and therefore the coherence among channels is damaged. Currently, there are two approaches to solve this problem to some extent. First, the spectral components of the signal in the overlapping portions of adjacent channels can be extracted to achieve inter-channel phase alignment in the digital domain [ Shi K., sillekens E., thomsen B.C.246-GHz direct pinned coherent receiver [ C ]. Optical Fiber Communication Conference,2017, pp.M3D-3 ]. This method is not suitable for signals where there are spectral notches in the channel overlap region and therefore cannot be used to process arbitrary wideband waveforms. Secondly, the digital local oscillator used in signal recovery can be locked to the down-conversion local oscillator in the channelization processing process, and compensation of extra phase shift is realized in signal recovery [ Pupalaikis P.J., schnecker M.A 30GHz Bandwidth,80GS/s Sample Rate Real-time Waveform digital systems [ C ]. National Fiber optical Engineers Conference,2010, pp.JThA52 ]. But the phase locking mode strengthens the coupling between the modules, so that the software and hardware of the system are difficult to separate, and the design and debugging difficulty is improved.
Disclosure of Invention
In order to solve the problems existing in the prior art, the invention provides a multichannel calibration and signal coherent recovery method for broadband channelization reception, which comprises the following steps:
step 2, taking the broadband waveform as an excitation signal, and recording N paths of intermediate frequency signals s obtained after the processing of the channelized receiver n (t), t being time, N =1,2, \8230;, N; the wideband waveform has an accurate time domain calibration result R (t), and a corresponding frequency spectrum R (omega) can cover the complete receiving bandwidth of the channelized receiver; wherein ω is angular frequency, ω =2 π f;
step 3, acquiring the intermediate frequency signal s of the reference signal n (t) phase of reception start time
Step 4, utilizing the time domain calibration result r (t) and N paths of intermediate frequency signals s n (t) calculating the amplitude-frequency response | H of each channel of the channelized receiver n (omega) | and phase frequency response & n (ω)；
Step 6, calculating phases to be compensated of each channel in signal coherent recovery
Wherein f is n The frequency of the local oscillation signal corresponding to the nth channel is obtained;
step 7, according to the amplitude frequency of each channel of the channelized receiverResponse | H n (omega) |, phase frequency response- n Omega, phase theta of each channel needing compensation in signal coherent recovery n Correcting intermediate frequency signal y n (t) obtaining an intermediate frequency signal Z n (ω) and intermediate frequency signal Z n And (omega) carrying out frequency shift and then superposing to complete the phase-coherent recovery of the broadband signal.
Further, the reference signal obtained in step 3 is an intermediate frequency signal s n (t) phase of reception start time
The specific process is as follows:
step 201, sending a reference signal into an auxiliary analog-to-digital converter for sampling; the auxiliary analog-to-digital converter collects N paths of intermediate frequency signals s n (t) the groups of analog to digital converters are synchronized with each other;
step 202, performing fourier analysis on the sampling result of the reference signal in the digital domain, wherein the phase at the frequency f is the phase
Further, the specific process of step 7 is as follows:
step 301, converting the intermediate frequency signal y n The N signals of (t) are respectively converted into frequency domain representation through Fourier transform, and the frequency domain representation is recorded as Y n (ω)；
Step 302, utilizing phase frequency response & lt H of each channel n The phase theta of each channel in the (omega) sum signal coherent recovery needs to be compensated n Respectively correcting the corresponding channels Y n (omega) to obtain an intermediate frequency signal Z n (ω), i.e. Z n (ω)＝Y n (ω)·exp[-j∠H n (ω)]·exp(jθ n ) (ii) a Wherein j represents an imaginary part;
step 303, converting the intermediate frequency signal Z n Shifting frequency of each path of signals in (omega) according to local oscillation frequency of corresponding channel, then superposing, and responding amplitude frequency | H of channel n (omega) I is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the obtained result is divided to obtain the frequency spectrum of the recovery signal
Namely, it is
Step 304, utilizing inverse Fourier transform to convert
Converting into time domain to obtain the recovery result of broadband signal
The multi-channel calibration and signal coherent recovery device for broadband channelization reception comprises a coherent multi-frequency local oscillator module for generating multi-channel channelization local oscillator signals, and further comprises:
a reference signal generation module: the device is used for generating a reference signal which is coherent with the multi-path channelized local oscillator signals; the reference signal is a single-frequency continuous wave signal, and the frequency f of the reference signal is a common divisor of the frequency of the multi-channel channelized local oscillation signal;
a broadband waveform generation module: for generating a broadband waveform for use as a measurement stimulus; the wideband waveform has an accurate time domain calibration result R (t), and a frequency spectrum R (omega) corresponding to the wideband waveform can cover the complete receiving bandwidth of the channelized receiver; t represents time, ω is angular frequency, ω =2 π f;
a phase calibration module: obtaining a reference signal at an intermediate frequency signal s n (t) phase of reception start time
Wherein s is n (t) is N paths of intermediate frequency signals s obtained after the broadband waveform is taken as an excitation signal and processed by a channelized receiver n (t); t represents time, N =1,2, \ 8230;, N;
a channel response calculation module: time domain calibration results r (t) and intermediate frequency signal s using wideband waveform n (t) calculating the amplitude-frequency response | H of each channel of the channelized receiver n (omega) | and phase frequency response & n (ω)；
The signal correction and coherent superposition module comprises: for amplitude-frequency response | H according to each channel n (omega) |, phase frequency response of each channel & n (omega) and intermediate frequency signal y n (t) receiving the phase of the start time, correcting the intermediate frequency signal Z obtained after channelizing the broadband signal to be received n (omega), frequency shifting and superposing the processing results to complete the phase-coherent recovery of the broadband signals; the intermediate frequency signal y n (t) is obtained by accessing the broadband signal x (t) to be received later.
Further, the phase calibration module specifically includes:
an auxiliary analog-to-digital converter: for sampling a reference signal; the auxiliary analog-to-digital converter collects N channelized intermediate frequency signals s n (t) the groups of analog to digital converters are synchronized with each other;
a Fourier analysis module: for fourier analysis of the sampling results of the reference signal in the digital domain, with the phase at frequency f as a calibration.
Further, the signal correction and coherent superposition module specifically includes:
a Fourier transform module: channelizing the broadband signal to obtain N paths of intermediate frequency signals y n (t) conversion to a frequency domain representation by Fourier transform, denoted Y n (ω)；
A phase correction module: is used for responding to the phase frequency & lt H of each channel n (omega) and intermediate frequency signal y n (t) correction of the phase of the reference signal at the reception start time Y n The phase of each signal in (omega) to obtain an intermediate frequency signal Z n (ω)；
The signal frequency shift superposition and amplitude correction module comprises: for converting intermediate frequency signals Z n Each path of signal in (omega) is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the channel amplitude frequency response | H n (omega) I is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the obtained result is divided to obtain the frequency spectrum of the recovery signal
Namely, it is
An inverse Fourier transform module: for transforming the signal by inverse Fourier transform
Converting into time domain to obtain the recovery result of broadband signal
Compared with the prior art, the invention has the following technical effects:
1. the broadband waveform of the time domain is taken as the measurement excitation of the channel response, the characteristic that the phase difference between different frequency components of the broadband signal is fixed is fully utilized, the phase-frequency response test problem of the channelized variable-frequency receiving channel is solved, and effective support can be provided for the post-calibration of the channelized link;
2. the phase difference between the channels is determined by using the reference signal which is coherent with the channelized local oscillator signal, so that the coherence between the channels in the signal recovery process can be ensured, the method is suitable for recovering any broadband waveform, and additional phase locking hardware is avoided.
Drawings
Fig. 1 is a schematic diagram of a prior art wideband channelized receiver.
Fig. 2 is a schematic diagram of a channel calibration and signal coherent recovery apparatus according to an embodiment of the present invention.
Fig. 3 is a signal processing flow of the signal correction and coherent addition module according to the embodiment of the present invention.
Fig. 4 is a graph of channel amplitude-frequency response measured by the method of the embodiment of the invention.
Fig. 5 is a diagram of channel phase-frequency response measured by the method of the embodiment of the invention.
Fig. 6 is a frequency spectrum diagram of a wideband chirp signal recovered by the method of the embodiment of the present invention.
Fig. 7 is a time-frequency diagram of a wideband chirp signal recovered by the method of the embodiment of the present invention.
FIG. 8 is a graph showing the effect on pulse pressure results when the inter-channel coherent state is non-coherent.
FIG. 9 is a graph showing the effect of inter-channel coherent state on pulse pressure results.
Detailed Description
The invention discloses a multichannel calibration and signal coherent recovery method for broadband channelized reception, which comprises the following steps: 1. generating a reference signal which is coherent with the channelized local oscillator signal, collecting the reference signal and a channelized processing result of a broadband signal to be received together, and analyzing the phase of the reference signal at the receiving starting moment; 2. measuring the amplitude-phase response of each channel by using the calibrated broadband time domain waveform as an excitation signal; 3. and completing correction, splicing and waveform recovery of the broadband signal in a digital domain by using the measurement result of the amplitude-phase response and the phase of the reference signal.
The invention also discloses a multi-channel calibration and signal coherent recovery device facing the broadband channelization reception. The device can accurately measure the amplitude-phase response of each frequency conversion channel of the channelized receiver and complete the coherent superposition and signal recovery among the channels, thereby solving the problem of broadband waveform recovery caused by the difficulty in measuring the phase response of the channels and the random phase difference among the channels in the existing broadband receiving technology.
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The technical scheme of the invention is explained in detail by combining the drawings as follows:
aiming at the problems that the channel response test of the existing channelized receiver is difficult and the coherence among the channels is difficult to guarantee, the idea of the invention is to use a time domain broadband waveform with a determined phase relationship as a measurement excitation to obtain the amplitude-phase response of each channel, calculate and compensate the phase difference among the channels through the phase of a reference signal, and finally realize the recovery of any broadband waveform.
Specifically, in an embodiment of the present invention, a method for multi-channel calibration and signal coherent recovery for wideband channelization reception includes the following steps:
step 2, taking the broadband waveform as an excitation signal, and recording N paths of intermediate frequency signals s obtained after the broadband waveform is processed by a channelized receiver n (t), t represents time, N =1,2, \8230;, N; the wideband waveform has an accurate time domain calibration result R (t), and a corresponding frequency spectrum R (omega) can cover the complete receiving bandwidth of the channelized receiver; wherein ω is angular frequency, ω =2 π f;
step 3, acquiring the intermediate frequency signal s of the reference signal n (t) phase of reception start time
Step 4, utilizing the time domain calibration result r (t) and N paths of intermediate frequency signals s n (t) calculating the amplitude-frequency response | H of each channel of the channelized receiver n (omega) | and phase frequency response- n (ω)；
Step 6, calculating phases to be compensated of each channel in signal coherent recovery
Wherein f is n The frequency of the local oscillation signal corresponding to the nth channel is obtained;
step 7, according to | H n (ω)|、∠H n (omega) and the phase theta to be compensated for each channel in the signal coherent recovery n Correcting intermediate frequency signal y n (t) obtaining an intermediate frequency signal Z n (ω) and will combine the intermediate frequency signal Z n And (omega) carrying out frequency shift and then superposing to complete the phase-coherent recovery of the broadband signal.
Preferably, in the proposed calibration and signal coherent recovery method, the step 3 is obtained
The specific process is as follows:
step 201, sending a reference signal into an auxiliary analog-to-digital converter for sampling; the auxiliary analog-to-digital converter collects N paths of intermediate frequency signals s n (t) the analog-to-digital converter groups are synchronized with each other;
step 202, performing fourier analysis on the sampling result of the reference signal in the digital domain, wherein the phase at the frequency f is the phase
Preferably, in the proposed method of calibration and signal coherent recovery, the mid-frequency signal y is corrected in step 7 n (t) and the specific process of superposition is as follows:
step 301, converting the intermediate frequency signal y n (t) the N signals are converted into frequency domain representation by Fourier transform, denoted as Y n (ω)；
Step 302, utilizing & lt H n (ω) and θ n Respectively correcting the corresponding channels Y n (omega) to obtain an intermediate frequency signal Z n (ω), i.e. Z n (ω)＝Y n (ω)·exp[-j∠H n (ω)]·exp(jθ n ) (ii) a Wherein j represents an imaginary part;
step 303, adding Z n Shifting frequency of each path of signals in (omega) according to local oscillation frequency of corresponding channel, then superposing, and responding amplitude frequency | H of channel n The (omega) I is also overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and then the obtained result is obtainedDividing to obtain the frequency spectrum of the recovered signal
Namely that
Step 304, utilizing inverse Fourier transform to convert
Converting into time domain to obtain the recovery result of broadband signal
The embodiment also provides a multi-channel calibration and signal coherent recovery device for wideband channelized reception, which includes:
coherent multifrequency local oscillator module: the system is used for generating multi-channel channelized local oscillator signals (local oscillator signals which are synchronous with each other and have different frequencies) and used for down-conversion of each channel in the channelized receiver;
a reference signal generation module: the device is used for generating a reference signal which is coherent with the multi-path channelized local oscillator signals; the reference signal is a single-frequency continuous wave signal, and the frequency f of the reference signal is the common divisor of the frequency of the multi-channel channelized local oscillation signal;
a broadband waveform generation module: for generating a broadband waveform for use as a measurement stimulus; the wideband waveform has an accurate time domain calibration result R (t), and a corresponding frequency spectrum R (omega) can cover the complete receiving bandwidth of the channelized receiver;
a phase calibration module: obtaining a reference signal at an intermediate frequency signal s n (t) phase of reception start time
Wherein s is n (t) N intermediate frequency signals s obtained by processing the broadband waveform as an excitation signal by a channelized receiver n (t); t represents time, N =1,2, \8230;, N;
a channel response calculation module: using r (t) and s n (t) calculating the amplitude-frequency response | H of each channel of the channelized receiver n (omega) | and phase frequency response- n (ω)；
The signal correction and coherent superposition module comprises: for according to | H n (ω)|、∠H n (omega) and intermediate frequency signal y n (t) receiving the phase of the start time, correcting the third intermediate frequency signal Z obtained after channelizing the broadband signal to be received n And omega, frequency shifting and superposing the processing results to complete the phase-coherent recovery of the broadband signal.
Preferably, the phase calibration module specifically includes:
an auxiliary analog-to-digital converter: for sampling a reference signal; the auxiliary analog-to-digital converter collects N channelized intermediate frequency signals s n (t) the groups of analog to digital converters are synchronized with each other;
a Fourier analysis module: for fourier analysis of the sampling results of the reference signal in the digital domain, with the phase at frequency f as a calibration.
Preferably, the signal modification and coherent addition module specifically includes:
a Fourier transform module: channelizing the broadband signal to obtain N paths of intermediate frequency signals y n (t) conversion to a frequency domain representation by Fourier transform, denoted Y n (ω)；
A phase correction module: is used for responding to the phase frequency & lt H of each channel n (omega) and intermediate frequency signal y n (t) correction of Y for the phase of the reference signal at the reception start time n The phase of each signal in (omega) to obtain an intermediate frequency signal Z n (ω)；
The signal frequency shift superposition and amplitude correction module comprises: for converting intermediate frequency signals Z n Each path of signal in (omega) is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the channel amplitude frequency response | H n The (omega) I is also overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and then the obtained result is divided to obtain the frequency spectrum of the recovery signal
Namely that
An inverse Fourier transform module: for transforming the signal by inverse Fourier transform
Converting into time domain to obtain the recovery result of broadband signal
To facilitate understanding of the public, the present invention will be described in further detail with reference to a preferred embodiment.
Fig. 1 is a schematic diagram of prior art channelized reception. The broadband signal to be processed is divided into N branches. The broadband signals in each branch are processed into narrowband signals through filters with the same bandwidth but with step-distributed central frequencies, and then the narrowband signals are mixed with local oscillator signals with step-distributed frequencies to complete down conversion. Each path of signals after down-conversion can be collected by an analog-to-digital converter (ADC) array, and the obtained data is sent to a processor for recovery processing of broadband signals.
The innovation of the invention is mainly aimed at amplitude-phase response measurement of each channelized channel and phase coherence maintenance among the channels. As shown in fig. 2, the input of the channelized receiver should be connected to a wideband waveform generation module when making response measurements. The broadband signal as used herein should satisfy several conditions: first, the spectrum is relatively flat; second, the spectrum may cover the full bandwidth of the channelized receive link; thirdly, the generation can be repeated for a plurality of times, and the signals generated each time are the same or only have fixed phase difference; fourth, the magnitude and phase of the signal spectrum are known or can be calibrated. The broadband excitation signal meeting the conditions is subjected to channelization processing to complete frequency band segmentation and down-conversion, and the result is collected and recorded by an analog-to-digital converter. And then, calculating the frequency spectrum of the signal obtained by each channel, and translating the frequency spectrum to a corresponding frequency band before the channelization processing.Comparing the obtained frequency spectrum with the frequency spectrum of the broadband signal, the measured value | H of the amplitude-phase response of each channel can be obtained n (omega) | and & n (ω)。
Besides the amplitude-phase response of each channel, another factor to be concerned in channelized reception is the inter-channel coherence. The coherent of the channels means that the phase relationship between two spectral components of the signal is unchanged or constant after the channelization process. Coherent multifrequency local oscillators in the channelization process are the first guarantee of multi-channel coherent. But the coherence between channels is still destroyed by the random delay between the signal to be processed and the local oscillator signal. Specifically, let the input signal to be processed be
s IN (t)＝cos(ω A t+θ A )+cos(ω B t+θ B ) (1)
Wherein ω is A ，ω B And
the angular frequency and phase of the two frequency components, respectively. Without setting angular frequency omega A Corresponding frequency components enter a first channel, and the frequency and the phase of corresponding down-conversion local oscillation signals are respectively omega 1 And theta 1 I.e. by
s LO1 (t)＝cos(ω 1 (t-τ)+θ 1 ) (2)
Wherein τ is a delay amount between the input signal to be processed and the local oscillation signal. After channelizing, the signal collected by ADC is
s CH1 (t)＝cos((ω 1 -ω A )t+(θ 1 -ω 1 τ)-θ A ) (3)
In order to achieve signal recovery, up-conversion of the signal should be achieved in the digital domain.
Local oscillator phase for recovery is
Namely, it is
Thus, the signal obtained after recovery is
Similarly, angular frequency ω B The corresponding frequency component enters a channel II, and the frequency of the corresponding local oscillator signal and the phases of the down-conversion local oscillator signal and the recovery local oscillator signal are respectively omega 2 、θ 2 And
the result obtained after channelization and recovery is
For this reason, a phase difference needs to be compensated
Can be expressed as
Wherein the fixed phase difference (theta) of the local oscillators 1 -θ 2 ) This can be compensated by the amplitude-phase response measurement of the channel, but the randomness of τ will hinder the coherent recovery of the signal. In order to solve the problem, the invention utilizes the method for measuring the random delay by the auxiliary signal to complete the calculation of the random delay between the local oscillator and the input signal by setting and synchronously acquiring a single-frequency reference signal which is coherent with the channelized local oscillator signal. When the frequency of the reference signal is local oscillator signalAnd when the signal frequency is a common divisor, the period of the reference signal is a common multiple of the period of each local oscillator signal. This indicates that, if the ADC array can synchronously acquire the reference signal of the coherent local oscillator module during the acquisition of the channelized output signal, the delay τ of the local oscillator and the input signal can be determined by the phase of the reference signal at the reception start time
Determining:
where f is the frequency of the reference signal. Due to the periodicity of the local oscillator signal, the additional phase difference due to the delay can still yield accurate measurements, although the amount of delay obtained may not be in accordance with reality. Coherence between multiple channels can thus be guaranteed. If the measured phase of the reference signal is as
And the phase of the reference signal when processing the signal to be received is
The delay amount of the local oscillator and the input signal considered in signal compensation is
Due to the fact that
Corresponding phase is counted into < H > n In (ω), formula (10) subtracts
Corresponding delay. Thus, the phase of each channel to be compensated in coherent recovery can be expressed as
Wherein f is n And the frequency of the local oscillation signal corresponding to the nth channel is obtained.
Using the measured amplitude-phase response of each channel and the phase to be compensated for to derive the intermediate frequency signal y from the channelized result data n The process of recovering the input wideband signal in (t) is shown in fig. 3. Firstly, intermediate frequency signal y is transmitted n (t) the N signals are converted into frequency domain representation by Fourier transform, denoted as Y n (ω). Then, utilizing < H n (ω) and θ n Respectively correcting corresponding channels Y n (omega) obtaining the intermediate frequency signal Z n (ω), i.e.
Z n (ω)＝Y n (ω)·exp[-j∠H n (ω)]·exp(jθ n ) (12)
Will Z n Shifting frequency of each path of signals in (omega) according to local oscillation frequency of corresponding channel, then superposing, and responding amplitude frequency | H of channel n The (omega) is also overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and then the obtained result is divided to obtain the frequency spectrum of the recovery signal
The corresponding mathematical relationship is
Finally, inverse Fourier transform is utilized to convert
Converting into time domain to obtain the recovery result of broadband signal
In order to verify the channel calibration and signal coherent recovery method proposed in this embodiment, a channelized demonstration module with two channels is built in the electrical domain by using a filter and a mixer. The demonstration module can divide signals with frequency of 10 GHz-12 GHz into two paths by using two paths of coherent local oscillator signals with frequencies of 12.3GHz and 13.3GHz respectively, and down-converts the signals to the frequency of 1.3-2.3 GHz. Amplitude-phase response measurements of the channelized link are first made. Therefore, the linear frequency modulation signal with the frequency range of 10 GHz-12 GHz and the pulse width of 10us is input into the time delay module. The channel amplitude-frequency and phase-frequency responses obtained after spectral analysis and shift comparison are shown in fig. 4 and 5. It can be seen that the amplitude-frequency response of the two channels is not flat, and the phase-frequency response also has a nonlinear component. If no correction is made, the recovered signal will deviate significantly from the original signal.
Fig. 6 and 7 show the results of recovering a chirp signal having a frequency range of 10GHz to 12GHz and a pulse width of 20us after processing by the channelization demonstration module. It can be seen that the overlapping portion between the two channels is in smooth transition, which indicates that the two channels are in good phase coherence and the compensation parameters of the channel amplitude-phase response have high accuracy. Fig. 8 and 9 compare the pulse pressure results of the signals obtained before and after applying the reference signal to compensate the local oscillator random delay. It can be seen that there are pits near the peak of the pulse pressure before compensation, which is a result of random phase differences between the two channels due to poor phase coherence. After compensation, the pulse pressure peak value shows a complete single-peak state, which indicates that the phase difference between channels is effectively corrected.
Compared with the prior art, the invention has the following beneficial effects:
1. the broadband waveform of the time domain is taken as the measurement excitation of the channel response, the characteristic that the phase difference between different frequency components of the broadband signal is fixed is fully utilized, the phase-frequency response test problem of the channelized variable-frequency receiving channel is solved, and effective support can be provided for the post-calibration of the channelized link;
2. the phase difference between the channels is determined by using the reference signal which is coherent with the channelized local oscillator signal, so that the coherence between the channels in the signal recovery process can be ensured, the method is suitable for recovering any broadband waveform, and additional phase locking hardware is avoided.
The terms "first," "second," "third," "fourth," and the like in the description of the application and the above-described figures, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b and c may be single or plural.
In the several embodiments provided in the present application, it should be understood that the disclosed system and apparatus may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method for calibrating and recovering coherent signals for wideband channelized reception according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present application.
Claims (6)
1. A method for multi-channel calibration and signal coherent recovery for wideband channelized reception, comprising the steps of:
step 1, generating a reference signal which is coherent with a plurality of channels of channelized local oscillator signals; the reference signal is a single-frequency continuous wave signal, and the frequency f of the reference signal is the common divisor of the frequency of the multi-channel channelized local oscillation signal;
step 2, taking the broadband waveform as an excitation signal, and recording N paths of intermediate frequency signals s obtained after the processing of the channelized receiver n (t), t being time, N =1,2, \8230;, N; the wideband waveform has an accurate time domain calibration result R (t), and a frequency spectrum R (omega) corresponding to the wideband waveform can cover the complete receiving bandwidth of the channelized receiver; wherein ω is angular frequency, ω =2 π f;
step 3, acquiring the intermediate frequency signal s of the reference signal n (t) phase of reception start time
Step 4, utilizing the time domain calibration result r (t) and N paths of intermediate frequency signals s n (t) calculating amplitude-frequency response | Hx (omega) | and phase-frequency response- n (ω)；
Step 5, accessing the broadband signal x (t) to be received, and recording the intermediate frequency signal y obtained by each channel n (t), N =1,2, \ 8230;, N, acquiring the reference signal at the intermediate frequency signal y n (t) phase of reception start time
Step 6, calculating phases to be compensated of each channel in signal coherent recovery
Wherein f is n The frequency of the local oscillation signal corresponding to the nth channel is obtained;
step 7, according to the amplitude-frequency response | H of each channel of the channelized receiver n (omega) |, phase frequency response- n Omega, phase theta of each channel needing compensation in signal coherent recovery n Correcting intermediate frequency signal y n (t) obtaining an intermediate frequency signal Z n (ω) and intermediate frequency signal Z n And (omega) performing frequency shift and then superposing to complete the phase-coherent recovery of the broadband signal.
2. The method of claim 1 wherein the reference signal is obtained in step 3 as an intermediate frequency signal s n (t) phase of reception start time
The specific process is as follows:
step 201, sending a reference signal into an auxiliary analog-to-digital converter for sampling; the auxiliary analog-to-digital converter collects N paths of intermediate frequency signals s n (t) the groups of analog to digital converters are synchronized with each other;
step 202, performing fourier analysis on the sampling result of the reference signal in the digital domain, wherein the phase at the frequency f is the phase
3. The method for multi-channel calibration and signal coherent recovery for wideband channelized reception of claim 1 wherein the specific procedure of step 7 is as follows:
step 301, converting the intermediate frequency signal y n The N signals of (t) are respectively converted into frequency domain representation through Fourier transform, and the frequency domain representation is recorded as Y n (ω)；
Step 302, utilizing phase frequency response & lt H of each channel n Phase theta of each channel to be compensated in coherent recovery of (omega) sum signal n Respectively correcting corresponding channels Y n (omega) to obtain an intermediate frequency signal Z n (ω)，Namely Z n (ω)＝Y n (ω)·exp[-j∠H n (ω)]·exp(jθ n ) (ii) a Wherein j represents an imaginary part;
step 303, converting the intermediate frequency signal Z n Each path of signal in (omega) is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the channel amplitude frequency response | H n (omega) I is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the obtained result is divided to obtain the frequency spectrum of the recovery signal
Namely, it is
Step 304, utilizing inverse Fourier transform to convert
Converting into time domain to obtain the recovery result of broadband signal
4. The utility model provides a multichannel calibration and signal coherent recovery unit that broadband channelization was received, is including the coherent multifrequency local oscillator module that is used for producing multichannel channelization local oscillator signal which characterized in that still includes:
a reference signal generation module: the device is used for generating a reference signal which is coherent with the multi-path channelized local oscillator signals; the reference signal is a single-frequency continuous wave signal, and the frequency f of the reference signal is the common divisor of the frequency of the multi-channel channelized local oscillation signal;
a wideband waveform generation module: for generating a broadband waveform for use as a measurement stimulus; the wideband waveform has an accurate time domain calibration result R (t), and a frequency spectrum R (omega) corresponding to the wideband waveform can cover the complete receiving bandwidth of the channelized receiver; t represents time, ω is angular frequency, ω =2 π f;
a phase calibration module: obtaining a reference signal at an intermediate frequency signal s n (t) phase of reception start time
Wherein s is n (t) is N paths of intermediate frequency signals s obtained after the broadband waveform is taken as an excitation signal and processed by a channelized receiver n (t); t represents time, N =1,2, \ 8230;, N;
a channel response calculation module: time domain calibration result r (t) and intermediate frequency signal s using wideband waveform n (t) calculating the amplitude-frequency response | H of each channel of the channelized receiver n (omega) | and phase frequency response- n (ω)；
The signal correction and coherent superposition module comprises: for amplitude-frequency response | H according to each channel n (omega) |, phase frequency response of each channel- n (omega) and the intermediate frequency signal y n (t) receiving the phase at the start time, correcting the intermediate frequency signal Z obtained after channelizing the broadband signal to be received n (omega), frequency shifting and superposing the processing results to complete the phase-coherent recovery of the broadband signals; the intermediate frequency signal y n (t) is obtained by accessing the broadband signal x (t) to be received later.
5. The apparatus for multi-channel calibration and signal coherent recovery for wideband channelized reception according to claim 4, wherein said phase calibration module specifically comprises:
an auxiliary analog-to-digital converter: for sampling a reference signal; the auxiliary analog-to-digital converter collects N channelized intermediate frequency signals s n (t) the groups of analog to digital converters are synchronized with each other;
a Fourier analysis module: for fourier analysis of the results of the sampling of the reference signal in the digital domain, with the phase at frequency f as a calibration.
6. The apparatus for multi-channel calibration and signal coherent recovery for wideband channelized reception according to claim 4 wherein the signal modification and coherent addition module comprises:
a Fourier transform module: channelizing the broadband signal to obtain N paths of intermediate frequency signals y n (t) by Fourier transformation respectivelyConverted to a frequency domain representation, denoted as Y n (ω)；
A phase correction module: is used for responding to phase frequency H according to each channel n (omega) and intermediate frequency signal y n (t) correction of the phase of the reference signal at the reception start time Y n The phase of each signal in (omega) to obtain an intermediate frequency signal Z n (ω)；
The signal frequency shift superposition and amplitude correction module comprises: for converting intermediate frequency signal Z n Each path of signal in (omega) is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the channel amplitude frequency response | H n The (omega) is overlapped after frequency shift according to the local oscillation frequency of the corresponding channel, and the obtained result is divided to obtain the frequency spectrum of the recovery signal
Namely, it is
An inverse Fourier transform module: for transforming the signal by inverse Fourier transform
Converting into time domain to obtain the recovery result of broadband signal
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