CN111736117B - Array signal analog decoherence method - Google Patents
Array signal analog decoherence method Download PDFInfo
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- CN111736117B CN111736117B CN202010600810.6A CN202010600810A CN111736117B CN 111736117 B CN111736117 B CN 111736117B CN 202010600810 A CN202010600810 A CN 202010600810A CN 111736117 B CN111736117 B CN 111736117B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/288—Coherent receivers
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Abstract
The invention discloses an array signal analog decoherence method, when in use, the array radar receives, and due to the fact that the noise of different analog receiving channels has great program correlation, SNR does not obtain certain benefit when receiving beam synthesis. The correlation of the phase noise of the analog radio frequency signals among the channels is mainly derived from common local oscillation signals. Therefore, the noise correlation of local oscillation signals among the channels of the table can be directly improved. Each channel switches to a different local oscillator at the receive of the front. Reduce the coherence of signal phase noise among channels, and improve the gain of the wave beam synthesis of the array surface for a single pulse signal. For single-channel multi-pulse signals, the gain of signal accumulation between pulses can be improved by adopting a mode of switching local oscillation sources with different frequencies between different receiving pulses.
Description
Technical Field
The invention relates to the technical field of electronic information, in particular to an array signal analog decoherence method.
Background
The digital phased array radar has the capability of receiving and transmitting beam electric scanning, the beam scheduling is extremely flexible, multi-target interception and tracking can be easily realized, and the digital phased array radar has strong anti-jamming capability and target detection and identification self-adaption capability. The scale of the existing digital radar array is larger and larger, and the radar power and the flexibility of radar resource scheduling are also larger and larger.
For a digital array radar, the synthesis of transmitting beams at different azimuth and pitch angles in space is completed by configuring initial phases and transmitting time of different transmitting units during transmitting, and because the number of the array units is large, the energy of the beams after the spatial synthesis is large during transmitting; meanwhile, the transmitted beam direction is determined by the initial phases of all the transmitting units of the array surface, and within a certain space range, the beam scanning airspace is completed without mechanically rotating the radar, and the beam scanning can be completed only by configuring the initial phases of the transmitting units of the array surface, so that the transmitted beam electric scanning is realized. During receiving, because the wave beams are completed by weighting the data of all receiving channels in certain amplitude and phase, simultaneous multi-wave beams including a main wave beam and an auxiliary wave beam can be received, and the anti-interference and target detection capabilities of the radar are greatly improved. In general, in the process of receive beam synthesis, it is desirable to accumulate useful signals as much as possible, and simultaneously, it is desirable to accumulate noise as little as possible, so that the signal-to-noise ratio of the synthesized signals is as large as possible. If the array surface has N receiving channels to participate in the receiving beam synthesis, and the received signal noise of all the channels is assumed to be uncorrelated, the synthesized noise is:
wherein σ tptal For the total noise, σ, after beam-forming 1 ，...，σ N Noise for channels 1 to N, where σ total Much less than the direct superposition of all channel noise.
Assuming that the useful signals of all channels are perfectly synthesized, the synthesized signal is:
S total ＝s 1 +s 2 +s 3 +...+s N
wherein S total Is the total signal after beam forming, s 1 ，...，s N For the signals of channels 1 to N, the signal-to-noise ratio of the synthesized signal is:
it can be seen that during the synthesis of the receive beam, the signal energy is normally accumulated, and the noise energy accumulation is smaller than that of the direct superposition, so after the signal synthesis, the SNR should be beneficial theoretically.
However, in the current practical test of the digital phased array radar, the signal noise after beam synthesis is far greater than sigma total The SNR gains far from the theoretical calculation, mainly because the noise of different analog receiving channels cannot be considered as completeUncorrelated, on the other hand, inter-channel signal phase noise is partially correlated due to the presence of common power and ground, common local oscillator signals, and the like. Because the array surface is large, the power supply and the ground are generally isolated by adopting a multi-stage power supply, most of the power supplies are distributed power supplies finally adopted by the array surface transmitting and receiving unit, in addition, the influence of the ground of the power supply is generally signals with lower frequency, the processing is reasonable, and the influence on radio frequency signals is limited, so that the correlation of the phase noise of the analog radio frequency signals among channels mainly comes from common local oscillation signals.
Thus each channel switches to a source of a different frequency local oscillator at the time of wavefront reception (the local oscillators differ in frequency from one another and, respectively, produce phase noise that is decorrelated). Reduce the coherence of signal phase noise among channels, and improve the gain of the wave beam synthesis of the array surface for a single pulse signal. For single-channel multi-pulse signals, the gain of signal accumulation between pulses can be improved by adopting a mode of switching local vibration sources with different frequencies between different received pulses.
Disclosure of Invention
In order to solve the above-mentioned drawbacks in the background art, an object of the present invention is to provide an array signal analog decoherence method, in which, when the array radar receives signals, due to the fact that the noise of different analog receiving channels has a large program correlation, the SNR does not obtain a certain benefit when receiving beam synthesis. The correlation of the phase noise of the analog radio frequency signals among the channels is mainly derived from common local oscillation signals. Therefore, the noise correlation of the local oscillation signals among the channels of the table can be directly improved. Each channel is switched to a different frequency dither source at the time of wavefront reception. Reduce the coherence of signal phase noise among channels, and improve the gain of the wave beam synthesis of the array surface for a single pulse signal. For single-channel multi-pulse signals, the gain of signal accumulation between pulses can be improved by adopting a mode of switching local vibration sources with different frequencies between different received pulses.
The purpose of the invention can be realized by the following technical scheme:
an array signal analog decoherence method, comprising the steps of:
firstly, generating a group of local oscillation signals with different frequencies in a frequency source, wherein the local oscillation frequencies have certain deviation, and ensuring that the intermediate frequency signals after frequency conversion of all channels are within a designed intermediate frequency bandwidth;
secondly, performing coherent elimination processing between local oscillation signals, wherein the local oscillation signals are coherent;
thirdly, each channel frequency conversion module is connected with two local oscillator signals and is switched into the frequency conversion module through an analog switch;
fourthly, during transmission, the frequency conversion module transmits a local oscillator, the local oscillator is the same for all transmission channels, the frequency is the same, and the local oscillator is output from the frequency source, amplified and distributed to all channels;
fifthly, during receiving, the local oscillator input of the frequency conversion module is switched to a receiving local oscillator through a switch, the local oscillator frequencies of all receiving channels are different, and the receiving local oscillator directly comes from a frequency source;
and sixthly, receiving the intermediate frequency signal, digitalizing by an ADC (analog to digital converter), filtering by digital down-conversion and extracting to a baseband, and using different digital local oscillators to match the frequency of the intermediate frequency signal.
Further, in the first step, different local oscillation sources are adopted for local oscillation signal transmission and reception, and the local oscillation sources are a group of spot frequency signals with different frequencies.
Further, all local oscillation signals with different frequencies generated by the local oscillation source are coherent signals.
Further, in the third step, the local oscillation signals are a transmit local oscillation and a receive local oscillation.
Furthermore, when the array surface is transmitted in the fourth step, all channels use the same local oscillator signal with the same frequency, so that the same radio frequency carrier frequency is realized, and beam space synthesis is ensured.
Furthermore, the array plane in the fifth step uses a local oscillation signal with a frequency different from that of the transmission time when receiving, and each analog receiving channel receives the local oscillation signal differently.
Further, the if signal in the sixth step should fall into the if filter band.
The invention has the beneficial effects that:
when the array radar array antenna is used, the array radar receives, and due to the fact that noise of different analog receiving channels has great program correlation, SNR (signal to noise ratio) does not obtain certain benefit when receiving beam synthesis. The correlation of the phase noise of the analog radio frequency signals among the channels mainly comes from the common local oscillation signals. Therefore, the noise correlation of the local oscillation signals among the channels of the table can be directly improved. Each channel is switched to a different frequency dither source at the time of wavefront reception. Reduce the coherence of signal phase noise among channels, and improve the gain of the wave beam synthesis of the array surface for a single pulse signal. For single-channel multi-pulse signals, the gain of signal accumulation between pulses can be improved by adopting a mode of switching local vibration sources with different frequencies between different received pulses.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a schematic diagram of a radar frequency source/local oscillator source of the present invention;
fig. 3 is a schematic diagram of a radar analog decoherence signal reception DBF of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, 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 invention.
In the description of the present invention, it is to be understood that the terms "opening," "upper," "lower," "thickness," "top," "middle," "length," "inner," "peripheral," and the like are used in an orientation or positional relationship that is merely for convenience in describing and simplifying the description, and do not indicate or imply that the referenced component or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be considered as limiting the present invention.
An analog decorrelation method for array signals, as shown in fig. 1, 2 and 3, includes the steps of:
firstly, generating a group of local oscillation signals with different frequencies in a frequency source, wherein the local oscillation frequencies have certain deviation, and ensuring that the intermediate frequency signals after frequency conversion of all channels are within a designed intermediate frequency bandwidth; when the local oscillation signal is transmitted and received, different local oscillation sources are adopted, and the local oscillation sources are a group of point frequency signals with different frequencies. All local oscillation signals with different frequencies generated by the local oscillation source are coherent signals.
Secondly, performing coherent removal processing between local oscillation signals, wherein the local oscillation signals are coherent;
thirdly, each channel frequency conversion module is connected with two local oscillator signals and is switched into the frequency conversion module through an analog switch; the local oscillation signals are a transmitting local oscillation and a receiving local oscillation.
Fourthly, during transmission, the frequency conversion module transmits a local oscillator, the local oscillator is the same for all transmission channels, the frequency is the same, and the local oscillator is output from the frequency source, amplified and distributed to all channels; when the array surface is transmitted, all channels use the same local oscillator signal with the same frequency, the same radio frequency carrier frequency is realized, and beam space synthesis is ensured.
Fifthly, during receiving, the local oscillator input of the frequency conversion module is switched to a receiving local oscillator through a switch, the local oscillator frequencies of all receiving channels are different, and the receiving local oscillator directly comes from a frequency source; the local oscillation signals with different frequencies from those in transmitting are used in receiving of the array surface, and the local oscillation signals received by each analog receiving channel are different.
And sixthly, receiving the intermediate frequency signal, digitalizing by an ADC (analog to digital converter), performing digital down-conversion filtering and extracting to a baseband, and using different digital local oscillators to match the frequency of the intermediate frequency signal, wherein the intermediate frequency signal is required to fall into an intermediate frequency filter band.
Where LO _ TX is used during the transmit period and a separate LO _ RX is used for each channel during the receive period, as shown in fig. 1.
After the digital phased array radar transmits wave speed, a target echo signal is received by an array formed by a plurality of receiving channels, then data of each receiving channel is weighted according to a certain amplitude phase to form a receiving wave beam, and the radar intercepts target information from the receiving wave beam.
Phase noise coherence of the analog channel signal can weaken the digital phased array combining gain and the accumulation gain. The non-coherent source of the analog channel signal noise generally originates mainly from the local oscillator signal. Since the local oscillation signals are from the same local oscillation source during receiving frequency conversion, and are generally distributed to all the receiving and transmitting channels after active power division amplification, the phase noise of the signals of all the receiving channels is coherent, which results in the loss of receiving gain during digital wave velocity synthesis; in addition, when multi-pulse target echo accumulation is realized, particularly when an airborne radar accumulates low-altitude low-speed small target echoes, echo signals of targets are weak, strong clutter or interference signals exist, and the coherence of multi-time target echo phase noise of a receiving channel and the coherence of target echo phase noise among multiple channels weaken the gain of signal accumulation. The invention realizes that different local vibration sources are adopted to reduce the coherence of channel signals during receiving when the wave beam of the array surface is transmitted and received. All channels transmitted by the wave front wave beam adopt the same local oscillation source, and the requirement on the phase noise correlation of signals is not high during transmission. Each channel is switched to a respective local oscillator source during reception of the wavefront, the local oscillator source frequency of each receiving channel is different and is generated in advance in the frequency source (the local oscillator sources are different in frequency and are generated respectively, and phase noise is decorrelated). The structure can reduce the coherence of signal phase noise among channels, and improves the gain of the wave beam synthesis of the front surface for a single pulse signal. For single-channel multi-pulse signals, the gain of signal accumulation between pulses is improved by adopting a mode of switching local vibration sources with different frequencies between different received pulses.
In the description herein, references to the description of "one embodiment," "an example," "a specific example," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are given by way of illustration of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, and such changes and modifications are within the scope of the invention as claimed.
Claims (7)
1. An analog decorrelation method for array signals, comprising the steps of:
firstly, generating a group of local oscillation signals with different frequencies in a frequency source, wherein the local oscillation frequencies have certain deviation, and ensuring that the intermediate frequency signals after frequency conversion of all channels are within a designed intermediate frequency bandwidth;
secondly, performing coherent elimination processing between local oscillation signals, wherein the local oscillation signals are coherent;
thirdly, each channel frequency conversion module is connected with two local oscillator signals and is switched into the frequency conversion module through an analog switch;
fourthly, during transmission, the frequency conversion module transmits local oscillators, the transmission local oscillators are the same for all transmission channels, the frequencies are the same, and the power is distributed to all the channels after being output from the frequency source and amplified;
fifthly, during receiving, the local oscillator input of the frequency conversion module is switched to a receiving local oscillator through a switch, the local oscillator frequencies of all receiving channels are different, and the receiving local oscillator directly comes from a frequency source;
and sixthly, receiving the intermediate frequency signal, digitalizing by an ADC (analog to digital converter), filtering by digital down-conversion and extracting to a baseband, and using different digital local oscillators to match the frequency of the intermediate frequency signal.
2. The analog decorrelation method for array signals according to claim 1, wherein in the first step, different local oscillation sources are used for transmission and reception of the local oscillation signals, and the local oscillation sources are a set of spot frequency signals with different frequencies.
3. The analog decorrelation method according to claim 2, wherein all of the local oscillator signals of different frequencies generated by the local oscillator source are coherent signals.
4. The analog decorrelation method for array signals according to claim 1, wherein the local oscillation signals in the third step are a transmit local oscillation and a receive local oscillation.
5. The analog decoherence method of array signals according to claim 1, wherein the same local oscillator signal with the same frequency is used for all channels during the array surface transmission in the fourth step, so that the same radio frequency carrier frequency is realized, and beam space synthesis is ensured.
6. The analog decoherence method of array signals according to claim 1, wherein in the fifth step, local oscillation signals with different frequencies from those of transmission are used for receiving the front surfaces, and the local oscillation signals received by each analog receiving channel are different.
7. The analog decorrelation method according to claim 1, wherein the if signal in the sixth step should fall within the if filter band.
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