CN115684683A - Coherent synthesis method and system for field intensity of radiation source for time slot excitation calibration - Google Patents
Coherent synthesis method and system for field intensity of radiation source for time slot excitation calibration Download PDFInfo
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Abstract
The invention relates to a coherent synthesis method and a coherent synthesis system for the field intensity of a radiation source for time slot excitation calibration, which can improve the power density of a radiation field at a target position to obtain the high-peak microwave field intensity of a local area, are used for research and application such as field intensity examination of a target object and the like, and solve the technical problems that the existing vacuum electronic device can only be subjected to strong electromagnetic radiation by an attached high-voltage pulse generating device and the system is complex. The coherent synthesis method of the radiation source field intensity of time slot excitation calibration excites the microwave radiation sources through excitation signals, gates each microwave radiation source through a specific time sequence and radiates to a target position. The invention also provides a coherent synthesis system of the radiation source field intensity for time slot excitation calibration, which comprises a frequency synthesizer, N microwave radiation sources arranged in any mode, a measuring antenna and a receiver. The excitation signal can be subsequently compensated to realize the radiation field coherence enhancement at the target position.
Description
Technical Field
The invention relates to a coherent synthesis method and a coherent synthesis system for the field intensity of a radiation source for time slot excitation calibration, which can improve the power density of a radiation field at a target position to obtain the high-peak microwave field intensity of a local area and are used for research and application such as field intensity examination of a target object.
Background
With the rapid development of microwave technology, in the high power microwave technology field such as microwave energy transmission and microwave energy industrial application, it is often required to obtain as high microwave power as possible. The output power of a single microwave radiation source is limited by the power capacity of the device, and power synthesis in space by using an array formed by a plurality of microwave radiation sources is an effective means capable of greatly improving the emission power of the system and improving the power density of a radiation field at a target position.
At present, vacuum electronic devices such as klystrons are commonly used in laboratories as microwave radiation sources, and strong electromagnetic radiation is generated through power synthesis and is used for the examination and research of the tolerance field intensity of targets. However, the vacuum electronics requires an additional high voltage pulse generator to generate strong electromagnetic radiation, and the system is complicated.
In recent years, semiconductor microwave device materials and process technology have made breakthrough progress, the output power of semiconductor microwave devices is higher and higher, and the semiconductor microwave devices have the potential of further improving the output power through the improvement of materials, processes and designs. The semiconductor microwave device belongs to an amplifying system, and when power synthesis is carried out, waveform control, time difference control and phase difference control of radiation field signals are easier to realize.
Disclosure of Invention
The invention aims to provide a coherent synthesis method and a coherent synthesis system of radiation source field intensity for time slot excitation calibration, aiming at the technical problems that the existing vacuum electronic device can only carry out strong electromagnetic radiation by an auxiliary high-voltage pulse generating device and the system is more complex, so that the power density of a radiation field at a target position can be improved, the microwave field intensity with a local high peak value can be obtained, and the coherent enhancement of the radiation field at the target position can be realized.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a coherent synthesis method of the field intensity of a radiation source for time slot excitation calibration is characterized by comprising the following steps:
s1, generating N excitation signals, wherein N is a positive integer greater than or equal to 1;
the gate time gates of the N excitation signals satisfy the following formula
Gate k (τ)＝Gate 1 (τ-T 1k )
In the formula: gate k (τ) represents the gate time of the kth excitation signal, k ∈ [2]；T 1k Is the time difference of the kth excitation signal gating time gate relative to the 1 st excitation signal gating time gate; τ is time;
s2, inputting the N excitation signals into N microwave radiation sources respectively, amplifying the N excitation signals by the N microwave radiation sources respectively, and sending the N radiation signals to a target position;
s3, the N radiation signals are received through the measurement antenna at the target position in the step S2 in an induction mode, the measurement antenna sends out N radiation field signals, and the receiver is used for receiving the N radiation field signals;
s4, defining the transmission of the microwave radiation source to the target position excited by the excitation signal as a transmission channel; respectively calculating the time difference and the phase difference of the N transmission channels;
and S5, respectively compensating the time difference and the phase difference of the N excitation signals according to the time difference and the phase difference obtained in the step S4, so that the amplitude and the phase of the radiation field signals of the N transmission channels reaching the target position are consistent, and realizing the coherent synthesis of the radiation field at the target position.
Further, in step S1, N excitation signals are generated by frequency synthesis, specifically:
in the formula, S 1A (τ)，…，S NA (τ) 1,2, \8230indicatingfrequency synthesis generation, N excitation signals; gate 1 (τ)，…，Gate N (τ) represents the gating time gates for the N excitation signals for the 1,2, \8230;, frequency synthesizers; f. of c In order to frequency synthesisA heart frequency;
is the equivalent phase of the up-conversion of the excitation signal.
Further, in step S2, the corresponding excitation signal sensed by each microwave radiation source specifically is:
S 1B (τ)＝S 1A (τ-T 1A ),
S 2B (τ)＝S 2A (τ-T 2A ),
...
S NB (τ)＝S NA (τ-T NA )
in the formula, S 1B (τ)，...，S NB (τ) represents S 1A (τ)，...，S NA (τ) N signals propagating to reach the microwave radiation source; t is a unit of 1A ,T 2A ,...,T NA Representing the propagation time difference of the N excitation signals from the frequency synthesizer to each microwave radiation source.
Further, in step S3, the N radiation signals received by the measuring antenna at the target position are specifically:
S 1C (τ)＝S 1B (τ-T 1B ),
S 2C (τ)＝S 2B (τ-T 2B ),
...
S NC (τ)＝S NB (τ-T NB )
in the formula, S 1C (τ)，...，S NC (τ) represents S 1B (τ)，...，S NB (τ) N signals passing from the microwave radiation source to the measurement antenna; t is 1B ,T 2B ,...,T NB Representing the difference in propagation time of the N radiation signals from the microwave radiation source to the target location.
Further, in step S3, the N radiation field signals received by the receiver are specifically:
in the formula, S 1D (τ)，...，S ND (τ) represents S 1C (τ)，...，S NC (τ) propagating the N signals through the measurement antenna to the receiver; t is L The propagation time differences of the N radiated field signals from the measuring antenna to the receiver are measured.
N radiation field signals satisfy the following formula
Gate k (τ-T kA -T kB -T L )·Gate i (τ-T iA -T iB -T L )＝0
In the formula: gate k (τ-T kA -T kB -T L )·Gate i (τ-T iA -T iB -T L ) A pulse envelope signal representing the kth microwave radiation source and the ith microwave radiation source, where k ≠ i and i ∈ [2, N]；T kA Representing the propagation time difference of the excitation signal from the frequency synthesizer to the k microwave radiation source; t is kB Representing a propagation time difference of a radiation signal propagating from the kth microwave radiation source to the target location; t is iA Representing the propagation time difference of the excitation signal from the frequency synthesizer to the ith microwave radiation source; t is iB Representing the difference in propagation time of the radiation signal from the ith microwave radiation source to the target location.
Further, in step S3, the receiver sequentially performs amplification, filtering, down-conversion, and digital sampling by the radio frequency front end to obtain a complex baseband signal:
...
in the formula, S 1E (τ)，…，S NE (τ) represents S 1D (τ)，...，S ND (τ) compensating the time difference and the phase difference to obtain a signal; j is an imaginary unit;
Further, step S4 specifically includes:
4.1 Time of each radiation field signal is calculated
In the formula (I), the compound is shown in the specification,
time of the k-th radiation field signal; pulsefrent { } denotes taking the pulse leading edge of the kth radiation field signal; abs () represents the complex amplitude of the k-th radiation field signal; i is k (τ) is the in-phase channel of the kth radiated field signal quadrature down-conversion; q k (τ) is the kth radiation field signal quadrature-phase channel;
4.2 Calculate the phase of the radiated field signal
In the formula (I), the compound is shown in the specification,
is the phase of the k-th radiation field signal;
4.3 Maintaining the time of the 1 st microwave radiation source constant, adding a time setting amount to the kth microwave radiation source according to step 4.1)
In the formula (I), the compound is shown in the specification,
representing an additional time difference from the kth to the Mth microwave radiation source, based on the time of the 1 st microwave radiation source;
represents the time of the 1 st radiation field signal, M ∈ [2,N]；
4.4 Keeping the phase of the 1 st microwave radiation source constant, adding a phase setting amount to the k-th microwave radiation source according to step 4.2)
In the formula (I), the compound is shown in the specification,
indicating an additional phase difference of the kth to the Mth microwave radiation sources with respect to the phase of the 1 st microwave radiation source;
represents the phase of the 1 st radiation field signal;
representing the phase of the k-th radiation field signal.
Further, step 5 specifically comprises:
respectively compensating the time difference and the phase difference of N excitation signals through a gating switch of the frequency synthesizer and a phase shifter at the front end of a microwave radiation source:
...
after compensation, the N excitation signals excite the microwave radiation source to generate N radiation signals, the amplitude and the phase difference of the radiation signals reaching the target position are consistent, and the radiation field signals formed at the target position are specifically as follows:
in the formula: s 1A' (τ)，…，S NA' (τ) represents N excitation signals generated by frequency synthesis after compensating the time difference and the phase difference; s 1C' (τ)，...，S NC' (τ) represents S 1A' (τ)，…，S NA' (τ) N signals that arrive at the receiver after propagation;
indicating additional time differences from the 2 nd, the right, the N th to the Mth microwave radiation source respectively based on the time difference of the 1 st microwave radiation source;
indicating the additional phase difference from the 1 st microwave radiation source to the 2 nd, the other, the N, respectively, mth microwave radiation source, with respect to the phase of the 1 st microwave radiation source.
Meanwhile, the invention also provides a coherent synthesis system of the radiation source field intensity for time slot excitation calibration, which is used for realizing the coherent synthesis method of the radiation source field intensity for time slot excitation calibration and is characterized in that: the device comprises a frequency synthesizer, N microwave radiation sources arranged in any mode, a measuring antenna and a receiver;
the frequency synthesizer is used for generating and outputting N paths of different excitation signals, and the N paths of different excitation signals are respectively used as the excitation signals of the N microwave radiation sources after phase shifting;
n excitation signal output ends of the frequency synthesizer are respectively connected with the excitation signal input ends of N microwave radiation sources which are arranged in an arbitrary mode through phase shifters, and a frequency time reference signal output end of the frequency synthesizer is connected with a receiver and used for ensuring phase locking of the receiver and the frequency synthesizer;
each microwave radiation source receives the respective excitation signal, generates a radiation signal after amplification, radiates the radiation signal to a target position, and forms a radiation field signal at the target position;
the measuring antenna is positioned at the target position and is connected with the receiver; the measuring antenna is used for sensing and measuring the radiation field signal and transmitting the radiation field signal to the receiver;
the receiver is used for receiving the radiation field signals, performing separation processing to obtain excitation signals corresponding to each microwave radiation source, and calculating the time difference and the phase difference of the excitation signals of each frequency synthesizer reaching the target position; and adjusting a gating time gate of the frequency synthesis excitation signal according to the calculated time difference and phase difference to realize coherent synthesis of the radiation source field intensity of time slot excitation calibration.
The radio frequency front end comprises a variable attenuator, an amplitude limiting low noise amplifier, a band-pass filter, a down-conversion module, a gain control module, an AD sampling module, a digital pre-selection filter and a digital quadrature down-conversion module which are sequentially connected;
the measuring antenna is connected with the variable attenuator; the receiver is connected with the digital quadrature down-conversion module;
the variable attenuator is used for adjusting the power of the radiation field signal;
the amplitude limiting low-noise amplifier is used for amplifying the radiation field signal processed by the variable attenuator;
the band-pass filter is used for filtering the amplified radiation field signal;
the down-conversion module is used for performing down-conversion on the filtered radiation field signal;
the gain control module is used for carrying out automatic gain control on the radiation field signal after the down-conversion;
the AD sampling module is used for converting the radiation field signal after automatic gain control into a digital signal;
the digital pre-selection filtering is used for image interference suppression before quadrature down-conversion of the digital signal;
the digital quadrature down-conversion module is used for converting the digital signal into a corresponding complex baseband signal.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
(1) The invention excites each distributed microwave radiation source through the excitation signal, and gates each microwave radiation source through the specific time sequence to radiate to the target position. The radiation signals of the individual microwave radiation sources arrive at the target position in a specific time sequence. The radiation signals are received at the target position, the excitation signals can be compensated in sequence by calculating the time difference and the phase difference of the radiation signals reaching the target position, the time and the phase of the excitation signals of the microwave radiation sources are further changed, coherent synthesis is realized, and the radiation field coherence at the target position is enhanced.
(2) The system compensates the time difference and the phase difference of the radiation signals of the microwave radiation sources reaching the target position by changing the time and the phase of the excitation signals of the microwave radiation sources, so that the amplitude and the phase of the radiation signals reaching the target position are consistent, and the coherent enhancement of the radiation field at the target position is realized. The method in which the time is changed can be realized by modulating the time difference of the pulses (excitation signals), and the phase is realized by a phase shifter at the front end of the microwave source.
(3) The invention generates strong electromagnetic radiation by a field strength coherent synthesis method, and compared with a method for generating strong electromagnetic radiation by using a vacuum electronic device as a microwave radiation source, the method is simpler and has flexible configuration.
(4) The method is used for improving the power density of the radiation field at the target position, obtaining the high-peak microwave field intensity of the local area, and can be used for research and application such as field intensity examination of the target object.
Drawings
FIG. 1 is a schematic diagram of a constructed coherent combining system for the field intensity of a radiation source.
Fig. 2 is a schematic diagram of implementation of time domain gating logic by using frequency synthesis in an embodiment of the coherent synthesis method for field intensity of a radiation source for time slot excitation calibration according to the present invention.
Fig. 3 is a schematic time slot diagram of a radiation source emitting a radiation signal by a microwave radiation source in an embodiment of the coherent combining method for field intensity of the radiation source for time slot excitation calibration according to the present invention.
Fig. 4 is a schematic diagram of adjusting an excitation signal at the front end of a microwave radiation source in an embodiment of the coherent combining method for field intensity of a radiation source for time slot excitation calibration according to the present invention.
Detailed Description
The design idea of the invention is as follows:
the method comprises the steps of utilizing the advantages of stable amplitude and phase difference of an amplification system of the microwave radiation sources, constructing a phase difference and time difference measuring system, receiving radiation field signals formed by the radiation field signals emitted by the microwave radiation sources at a target position, and calculating the time difference and the phase difference of the radiation signals emitted by the microwave radiation sources reaching the target position in a signal processing mode.
In order to realize the measurement of the time difference and the phase difference, the invention designs a time slot excitation signal, and respectively excites each microwave radiation source through corresponding time sequence gating. The radiation field signals of the respective microwave radiation sources arrive at the target position according to a specific time sequence. And receiving the radiation field signals at the target position, and calculating the time difference and the phase difference of each microwave radiation source reaching the target position in a signal processing mode. The time difference and the phase difference of the radiation field signals of the microwave radiation sources reaching the target position are compensated by changing the time difference and the phase difference of the excitation signals of the microwave radiation sources, so that the amplitude value and the phase difference of the radiation field signals of the microwave radiation sources reaching the target position are consistent, and the radiation field coherence enhancement at the target position is realized. The method for changing the time difference can be realized by changing the pulse time difference of the modulation excitation signal, and the phase difference change can be realized by a phase shifter at the front end of the microwave radiation source.
As shown in fig. 1, the radiation source field strength coherent combining system for time slot excitation calibration provided by the present invention further includes a frequency synthesizer, N microwave radiation sources arranged in any manner, a measuring antenna, and a receiver; high field strength is realized at a certain target position.
N excitation signal output ends of the frequency synthesizer are respectively connected with the excitation signal input ends of N microwave radiation sources which are arranged in an arbitrary mode through phase shifters, and a frequency time reference signal output end of the frequency synthesizer is connected with the receiver and used for ensuring phase locking of the receiver and the frequency synthesizer; the measuring antenna is positioned at the target position and is connected with the receiver; the frequency synthesizer is used for generating and outputting N paths of different excitation signals, and the N paths of different excitation signals are respectively used as the excitation signals of the N microwave radiation sources after phase shifting; each microwave radiation source receives the respective excitation signal, generates a radiation signal after amplification, radiates the radiation signal to a target position, and forms a radiation field signal at the target position; the measuring antenna is used for sensing and measuring the radiation field signal and transmitting the radiation field signal to the receiver; the receiver is used for receiving radiation field signals, performing separation processing to obtain excitation signals corresponding to each microwave radiation source, and calculating the time difference and the phase difference of the excitation signals of each frequency synthesizer reaching a target position; and adjusting a gating time gate of the frequency synthesis excitation signal according to the calculated time difference and phase difference to realize coherent synthesis of the radiation source field intensity of time slot excitation calibration.
In this embodiment, a radio frequency front end is further disposed between the measuring antenna and the receiver, and the radio frequency front end includes a variable attenuator, a limiting low noise amplifier, a band-pass filter, a down-conversion module, a gain control module, an AD sampling module, a digital pre-selection filter, and a digital quadrature down-conversion module, which are connected in sequence; the measuring antenna is connected with the variable attenuator, and the receiver is connected with the digital orthogonal down-conversion module;
the frequency synthesizer is used for generating and outputting N paths of different excitation signals which are respectively used as the excitation signals of the N microwave radiation sources; each microwave radiation source receives the respective excitation signal, generates a radiation signal after amplification, radiates the radiation signal to a target position, and forms a radiation field signal at the target position; the measuring antenna is used for sensing and measuring the radiation field signal and transmitting the radiation field signal to the variable attenuator; the variable attenuator is used for adjusting the power of the radiation field signal; the amplitude limiting low-noise amplifier is used for amplifying the radiation field signal processed by the variable attenuator; the band-pass filter is used for filtering the amplified radiation field signal; the down-conversion module is used for performing down-conversion on the filtered radiation field signal; the gain control module is used for carrying out automatic gain control on the radiation field signal after the down-conversion; the AD sampling module is used for converting the radiation field signal after automatic gain control into a digital signal; the digital pre-selection filtering is used for image interference suppression before quadrature down-conversion; and the digital quadrature down-conversion module is used for converting the digital signals into corresponding complex baseband signals.
Firstly, physical channels with time synchronization and phase locking need to be established among all microwave radiation sources, the radiation signal time and phase of each microwave radiation source are controlled, and the coherence enhancement at a specific position is realized. The system constructed by the invention consists of N microwave radiation sources distributed at different positions, a frequency synthesizer, a receiver and a measuring antenna. The frequency time reference signal output end of the frequency synthesizer is connected with the receiver and used for ensuring the phase locking of the receiver and the frequency synthesizer, and N excitation signal output ends of the frequency synthesizer are respectively connected with excitation signal input ends of N microwave radiation sources which are arranged in an arbitrary mode through a phase shifter; the measuring antenna is used for sensing and measuring the radiation field signal and transmitting the radiation field signal to the receiver; the measuring antenna is positioned at the target position and is connected with the receiver; the frequency synthesizer is used for generating and outputting N paths of different excitation signals, and the N paths of different excitation signals are respectively used as the excitation signals of the N microwave radiation sources after phase shifting; each microwave radiation source receives the respective excitation signal, generates a radiation signal after amplification, radiates the radiation signal to a target position, and forms a radiation field signal at the target position; the receiver is used for receiving the radiation field signals, performing separation processing to obtain the excitation signals corresponding to the microwave radiation sources, and calculating the time difference and the phase difference of the excitation signals of the frequency synthesizers reaching the target position.
In this embodiment, the receiver is sequentially connected with a variable attenuator, a limiting low noise amplifier, a band-pass filter, a down-conversion module, a gain control module, an AD sampling module, a digital pre-selection filter and a digital quadrature down-conversion module;
the measuring antenna is connected with the variable attenuator and is used for adjusting the power of the radiation field signal; the frequency time reference signal output end of the frequency synthesizer is connected with the reference signal input end of the receiver; the amplitude limiting low-noise amplifier is used for amplifying the radiation field signal processed by the variable attenuator; the band-pass filter is used for filtering the amplified radiation field signal; the down-conversion module is used for performing down-conversion on the filtered radiation field signal; the gain control module is used for carrying out automatic gain control on the radiation field signal after the down-conversion; the AD sampling module is used for converting the radiation field signal after automatic gain control into a digital signal; the digital pre-selection filtering is used for image interference suppression before orthogonal down-conversion is carried out on the digital signal; and the digital quadrature down-conversion module is used for converting the digital signals into corresponding complex baseband signals.
The excitation signal for each microwave radiation source is generated by a frequency synthesizer, and the excitation signal for each microwave radiation source is required to be generated independently, and the waveform is completely controllable. The deployment position of each microwave radiation source is not particularly restricted. As can be seen in fig. 1, the plurality of microwave radiation sources of the present invention are arranged in any manner. The frequency synthesizer signal output end is electrically connected with the signal input ends of the N microwave radiation sources which are arranged in any mode; the receiving antenna is located at the target location and is electrically connected to the receiver. The receiver processes the radiation field signals at the target position and calculates the time difference and the phase difference of the radiation signals emitted by the microwave radiation sources reaching the target position.
The coherent synthesis method of the radiation source field strength for time slot excitation calibration of the present invention is described in detail below with reference to the accompanying drawings, in which:
as shown in fig. 2, the frequency synthesizer generates N different excitation signals, where N is a positive integer greater than or equal to 1;
wherein τ represents time; s 1A (τ)，…，S NA (τ) represents the excitation signal generated by the frequency synthesizer for the corresponding 1,2,3 microwave radiation source; gate 1 (τ)，…，Gate N (τ) gate timing signals representing the excitation signals generated by the N microwave radiation sources with a frequency synthesis to 1,2, \8230; f. of c Is the center frequency of the frequency ensemble;
is the up-conversion equivalent phase of the frequency complex.
Selecting gating time gates of all time domains of the frequency synthesizer to satisfy the formula (2):
Gate k (τ)＝Gate 1 (τ-T 1k )，k＝2,3,...,N (2)
in the formula, gate k (τ) represents the gating time gate of the excitation signal generated by the kth microwave radiation source integrated in frequency, k ∈ [2, N]；T 1k Is the time difference of the gate time of the kth microwave radiation source relative to the gate time of the 1 st microwave radiation source.
After each microwave radiation source receives the excitation signal, the excitation signal is amplified, and the amplified excitation signal is radiated to a target position. In this embodiment, for convenience of distinction, the signal radiated by the microwave radiation source is referred to as a radiation signal. The signal at the target location is recorded as the radiated field signal. When the excitation signal generated by the frequency synthesizer is transmitted to each microwave radiation source, each excitation signal generates different time differences:
in the formula, S 1B (τ)，...，S NB (τ) represents S 1A (τ)，...，S NA (τ) N signals, T, propagating to the microwave radiation source 1A ,T 2A ,...,T NA Representing the propagation time difference of the N excitation signals generated by the frequency synthesizer from the frequency synthesizer to each microwave radiation source.
As shown in fig. 3, the microwave radiation source amplifies the signal and radiates it to the target location. Since the distances between the respective microwave radiation sources and the target position are different, the respective radiation signals will also generate different signal propagation time differences:
in the formula, S 1C (τ)，...，S NC (τ) represents S 1B (τ)，...，S NB (tau) N signals, T, passing through a microwave radiation source to a measuring antenna 1B ,T 2B ,...,T NB Representing the difference in propagation time of the N radiation signals from the microwave radiation source to the target location.
And finally, the measuring antenna at the target position carries out induction measurement on the radiation field signal and transmits the radiation field signal to the radio frequency front end. In this embodiment, the selection principle of the measuring antenna is to adopt an electrically small measuring antenna, so as to reduce the influence of the measuring antenna on the propagation of the electromagnetic field. Meanwhile, the arrival directions of the microwave radiation sources relative to the target position are different in the invention. When selecting the measurement antenna, wide angle reception should be used. If necessary, the phase difference pattern of the measuring antenna can be calibrated into the system.
After the rf front end performs level adjustment on the radiated field signal, the signal may be transmitted to a receiver by using an rf cable. For the case where the target location is far from the receiver, the radio frequency signal may be modulated by an optical signal and transmitted through an optical fiber. The radiated field signal propagation time differences from the receive measurement antennas to the receiver are identical. Therefore, the signals of the radiated field signals arriving at the receiver are:
in the formula, S 1D (τ)，...，S ND (τ) represents S 1C (τ)，...，S NC (τ) N signals, T, propagating through the measuring antenna to reach the receiver L The propagation time differences of the N radiated field signals from the measuring antenna to the receiver are measured.
The radiation field signal propagation time difference passed from the receiving measurement antenna to the receiver is uniform for all microwave radiation sources. In order to ensure that the radiation field signals do not interfere with each other when reaching the receiver, the radiation field signals are required to satisfy the following formula:
Gate k (τ-T kA -T kB -T L )·Gate i (τ-T iA -T iB -T L )＝0,k≠i (6)
in the formula, gate k (τ-T kA -T kB -T L )·Gate i (τ-T iA -T iB -T L ) The product term is the pulse envelope signal of the kth microwave radiation source and the ith microwave radiation source of equation (5), where k ≠ i and i ∈ [2, N]；T kA Representing the propagation time difference of the excitation signal from the frequency synthesizer to the k microwave radiation source; t is kB Representing a propagation time difference of a radiation signal propagating from the kth microwave radiation source to the target location; t is a unit of iA Representing the propagation time difference of the excitation signal from the frequency synthesizer to the ith microwave radiation source; t is iB Representing the difference in propagation time of a radiation signal from the ith microwave radiation source to the target location
In this embodiment, it is preferable to ensure that the signals of the respective radiation fields reach the receiver without interfering with each other by the following formula:
in the formula, T 1i Is the time difference of the gate time of the ith microwave radiation source relative to the gate time of the 1 st microwave radiation source.
In this embodiment, the time difference between the excitation signals generated by the frequency synthesizer is set according to equation (7), so that the respective excitation signals can reach the receiver in the respective order. And no aliasing in the time domain occurs. Due to the fact that the time difference of each excitation signal can be estimated through the approximate lengths of the cable and the feeder line, an upward conservative calculation method can be adopted, and the situation that aliasing does not occur is guaranteed.
The local oscillator frequency and the sampling clock requirements of the receiver are generated by frequency synthesizers. The signals transmitted from the measuring antenna to the receiver are sequentially subjected to amplification, filtering, down-conversion and digital sampling operations through a radio frequency front end to obtain a complex baseband signal of a formula (9):
in the formula, S 1E (τ)，…，S NE (τ) represents S 1D (τ)，…，S ND (tau) signals obtained after amplification, filtering, down-conversion, digital sampling operations;
is the receiver down-conversion reference phase.
Since each microwave radiation source is received by the same receiving channel, the down-conversion reference phase of the receiver is consistent for all radiation field signals. The fixed phase portion of the microwave radiation source (i.e., the common phase of the radiation signals) is:
therefore, equation (9) can be expressed as:
in the formula, S 1E (τ)，…，S NE (τ) represents S 1D (τ)，...，S ND (τ) compensating the time difference and the phase difference to obtain a signal; j is an imaginary unit;
expression (11) is expressed at the receiverIs I k 、Q k Two channels of data (i.e. in receiver where the complex signal is in phase I k And quadrature phase Q k Data for both channels); calculating a time difference and a phase difference caused by a distance difference of the microwave radiation source to the target position; the time difference calculation method comprises the following steps:
in the formula (I), the compound is shown in the specification,
time difference of the k radiation field signal; pulsefrnt denotes taking the leading edge of the pulse of the k-th radiation field signal, abs () denotes taking the complex amplitude of the k-th radiation field signal, I k (τ) in-phase channel, Q, of quadrature down-conversion of the kth radiated field signal k (τ) is the kth radiation field signal quadrature-phase channel; in this embodiment, the leading edge of the pulse is actually the leading edge of the pulse, the trailing edge of the pulse, the center of the pulse, etc., and the methods for taking the microwave radiation sources are consistent. It is not necessary to take the leading edge of the pulse, but the time difference calculation method and criteria for all signals are exactly the same.
Determining the effective time support of each radiation field signal as
Wherein atan2 () is an arctangent function, T set(k) Is a valid subset.
Based on the propagation time differences of the excitation signals of the microwave radiation sources (i.e., equation (2)) that are set previously, the following can be obtained:
therefore, with reference to the 1 st microwave radiation source, the propagation time difference can be calculated:
wherein the content of the first and second substances,
representing an additional time difference from the kth to the Mth microwave radiation source, based on the time of the 1 st microwave radiation source; example T 1k To start setting values, known quantities are used.
Calculating the phase difference of each microwave radiation source waveform as:
wherein the content of the first and second substances,
is the phase of the k-th radiation field signal;
therefore, with reference to the 1 st microwave radiation source, the phase difference of each microwave radiation source can be calculated as:
based on this, the calculation of the time difference and the phase difference is completed.
Keeping the time of the 1 st microwave radiation source unchanged, and adding the setting quantity to the excitation signals of other microwave radiation sources as follows:
wherein the content of the first and second substances,
when using the 1 st microwave radiation sourceAn additional time difference from the kth to the Mth microwave radiation source on a time basis;
represents the time of the 1 st radiation field signal, M ∈ [2,N]；
Keeping the phase of the 1 st microwave radiation source unchanged, and adding phase setting quantities to the excitation signals of other microwave radiation sources as follows:
wherein, the first and the second end of the pipe are connected with each other,
indicating an additional phase difference of the kth to the Mth microwave radiation sources with respect to the phase of the 1 st microwave radiation source;
represents the phase of the 1 st radiation field signal;
representing the phase of the k-th radiation field signal.
On the basis of the calculation result, the time difference and the phase difference of the radiation signals of the microwave radiation sources are changed by adjusting the excitation signal of the frequency synthesizer:
wherein S is 1A' (τ)，…，S NA' (τ) N excitation signals generated by the frequency synthesizer after compensating for the time difference and the phase difference; s 1C' (τ)，...，S NC' (τ) represents S 1A' (τ)，…，S NA' (τ) N signals that arrive at the receiver after propagation;
is shown as 1 stThe time difference of the microwave radiation sources is taken as a reference, and the additional time difference from the No. 2, the No. N microwave radiation sources to the Mth microwave radiation source is respectively obtained;
indicating the additional phase difference from the 1 st microwave radiation source to the 2 nd, the other, the N, respectively, mth microwave radiation source, with respect to the phase of the 1 st microwave radiation source.
As shown in fig. 4, the time difference is realized by time adjustment of the gating switch. In this embodiment, the additional phase may be added with a phase shifter at the front end of the amplification chain of the microwave radiation source. The excitation signal generated by the frequency synthesizer is transmitted to each microwave radiation source and radiated to the target position through the measuring antenna:
comparing equations (17), (18) and (20) it can be seen that the amplitude and phase of the microwave radiation source at the target location are consistent, achieving coherence enhancement.
And (3) performing time difference and phase difference compensation setting on the frequency synthesizer, adjusting the initial phase and time of the frequency synthesizer to radiate the target position, and realizing phase compensation on the intermediate frequency signal of the frequency synthesizer. The radiation signal realized by the method can realize the field intensity coherence enhancement at the target position.
Claims (10)
1. A coherent synthesis method of the field intensity of a radiation source for time slot excitation calibration is characterized by comprising the following steps:
s1, generating N excitation signals, wherein N is a positive integer greater than or equal to 1;
the gate time gates of the N excitation signals satisfy the following formula
Gate k (τ)＝Gate 1 (τ-T 1k )
In the formula: gate k (τ) represents the gating time gate for the kth excitation signal, k ∈ [2,N]；T 1k Is the time difference of the kth excitation signal gating time gate relative to the 1 st excitation signal gating time gate; τ is time;
s2, inputting the N excitation signals into N microwave radiation sources respectively, amplifying the N excitation signals by the N microwave radiation sources respectively, and sending the N radiation signals to a target position;
s3, the N radiation signals are received through the measurement antenna at the target position in the step S2 in an induction mode, the measurement antenna sends out N radiation field signals, and the receiver is used for receiving the N radiation field signals;
s4, defining transmission of the excitation signal to excite the microwave radiation source to reach a target position as a transmission channel; respectively calculating the time difference and the phase difference of the N transmission channels;
and S5, respectively compensating the time difference and the phase difference of the N excitation signals according to the time difference and the phase difference obtained in the step S4, so that the amplitude and the phase of the radiation field signals of the N transmission channels reaching the target position are consistent, and realizing the coherent synthesis of the radiation field at the target position.
2. The coherent combining method for the field intensity of the radiation source for time slot excitation calibration according to claim 1, wherein the N excitation signals in step S1 are generated by frequency synthesis, specifically:
in the formula, S 1A (τ)，…，S NA (τ) 1,2, \8230indicatingfrequency synthesis generation, N excitation signals; gate 1 (τ)，…，Gate N (τ) represents the gating time gates for the N excitation signals for the 1,2, \8230;, frequency synthesizers; f. of c Is the center frequency of the frequency ensemble;
is the equivalent phase of the excitation signal up-conversion.
3. The coherent combination method of radiation source field strength for time slot excitation calibration according to claim 2, wherein in step S2, the corresponding excitation signal sensed by each microwave radiation source specifically includes:
S 1B (τ)＝S 1A (τ-T 1A ),
S 2B (τ)＝S 2A (τ-T 2A ),
...
S NB (τ)＝S NA (τ-T NA )
in the formula, S 1B (τ)，...，S NB (τ) represents S 1A (τ)，...，S NA (τ) N signals propagating to reach the microwave radiation source; t is a unit of 1A ,T 2A ,...,T NA Representing the propagation time difference of the N excitation signals from the frequency synthesizer to each microwave radiation source.
4. The coherent combination method of field intensity of radiation source for time slot excitation calibration according to claim 3, wherein in step S3, the N radiation signals received by the measuring antenna at the target position are specifically:
S 1C (τ)＝S 1B (τ-T 1B ),
S 2C (τ)＝S 2B (τ-T 2B ),
...
S NC (τ)＝S NB (τ-T NB )
in the formula, S 1C (τ)，...，S NC (τ) represents S 1B (τ)，...，S NB (τ) N signals passing through the microwave radiation source to the measurement antenna; t is a unit of 1B ,T 2B ,...,T NB Representing the difference in propagation time of the N radiation signals from the microwave radiation source to the target location.
5. The coherent combining method for the field intensity of the radiation source for time slot excitation calibration according to claim 4, wherein in step S3, the N radiation field signals received by the receiver are specifically:
in the formula, S 1D (τ)，...，S ND (τ) represents S 1C (τ)，...，S NC (τ) propagating the N signals through the measurement antenna to the receiver; t is a unit of L Propagation time differences of the N radiation field signals from the measuring antenna to the receiver are measured;
the N radiation field signals satisfy the following equation:
Gate k (τ-T kA -T kB -T L )·Gate i (τ-T iA -T iB -T L )＝0
in the formula: gate k (τ-T kA -T kB -T L )·Gate i (τ-T iA -T iB -T L ) A pulse envelope signal representing the kth microwave radiation source and the ith microwave radiation source, where k ≠ i and i ∈ [2, N]；T kA Representing the propagation time difference of the excitation signal from the frequency synthesizer to the k microwave radiation source; t is kB Representing a propagation time difference of a radiation signal propagating from the kth microwave radiation source to the target location; t is a unit of iA Representing the propagation time difference of the excitation signal from the frequency synthesizer to the ith microwave radiation source; t is iB Representing the difference in propagation time of the radiation signal from the ith microwave radiation source to the target location.
6. The coherent synthesis method of the radiation source field strength for time slot excitation calibration according to claim 5, characterized in that, in step S3, the receiver sequentially performs amplification, filtering, down-conversion and digital sampling through the radio frequency front end to obtain a complex baseband signal:
in the formula, S 1E (τ)，…，S NE (τ) represents S 1D (τ)，...，S ND (τ) compensating the time difference and the phase difference to obtain a signal; j is an imaginary unit;
7. The coherent combining method for the field intensity of the radiation source for time slot excitation calibration according to claim 6, wherein the step S4 specifically comprises:
4.1 Time of each radiation field signal is calculated
In the formula (I), the compound is shown in the specification,
time of the k-th radiation field signal; pulsefirt { } denotes the pulse leading edge of the k-th radiation field signal; abs () represents the complex amplitude of the k-th radiation field signal; i is k (τ) is the in-phase channel of the kth radiated field signal quadrature down-conversion; q k (τ) is the kth radiation field signal quadrature-phase channel;
4.2 Calculate the phase of the radiated field signal
In the formula (I), the compound is shown in the specification,
the phase of the k-th radiation field signal;
4.3 Maintaining the time of the 1 st microwave radiation source constant, adding a time setting amount to the kth microwave radiation source according to step 4.1)
In the formula (I), the compound is shown in the specification,
representing an additional time difference from the kth to the mth microwave radiation source, based on the time of the 1 st microwave radiation source;
represents the time of the 1 st radiation field signal, M ∈ [2,N]；
4.4 Keeping the phase of the 1 st microwave radiation source constant, adding a phase setting amount to the k-th microwave radiation source according to step 4.2)
In the formula (I), the compound is shown in the specification,
indicating an additional phase difference of the kth to the Mth microwave radiation sources with respect to the phase of the 1 st microwave radiation source;
represents the phase of the 1 st radiation field signal;
representing the phase of the k-th radiation field signal.
8. The coherent combining method for the field intensity of the radiation source for time slot excitation calibration according to claim 7, wherein the step 5 specifically comprises:
respectively compensating the time difference and the phase difference of N excitation signals through a gating switch of the frequency synthesizer and a phase shifter at the front end of the microwave radiation source:
after compensation, the microwave radiation source is excited by the N excitation signals to generate N radiation signals, the amplitude and the phase difference of the N radiation signals reaching the target position are consistent, and the radiation field signals formed at the target position are specifically as follows:
in the formula: s. the 1A' (τ)，…，S NA' (τ) represents N excitation signals generated by frequency synthesis after compensating the time difference and the phase difference; s 1C' (τ)，...，S NC' (τ) represents S 1A' (τ)，…，S NA' (τ) N signals that arrive at the receiver after propagation;
indicating additional time differences from the 2 nd, the right, the N th to the mth microwave radiation source, respectively, based on the time of the 1 st microwave radiation source;
indicating the additional phase difference from the 1 st microwave radiation source to the 2 nd, the other, the N, respectively, mth microwave radiation source, with respect to the phase of the 1 st microwave radiation source.
9. A coherent combining system of radiation source field strength for time slot excitation calibration, for implementing the coherent combining method of radiation source field strength for time slot excitation calibration according to any one of claims 1 to 8, characterized in that: the device comprises a frequency synthesizer, N microwave radiation sources arranged in any mode, a measuring antenna and a receiver;
the frequency synthesizer is used for generating and outputting N paths of different excitation signals, and the N paths of different excitation signals are respectively used as the excitation signals of N microwave radiation sources after phase shifting;
the N excitation signal output ends of the frequency synthesizer are respectively connected with the excitation signal input ends of the N microwave radiation sources which are arranged in an arbitrary mode through phase shifters, and the frequency time reference signal output end of the frequency synthesizer is connected with the receiver and used for ensuring the phase locking of the receiver and the frequency synthesizer;
each microwave radiation source receives the respective excitation signal, generates a radiation signal after amplification, radiates the radiation signal to a target position, and forms a radiation field signal at the target position;
the measuring antenna is positioned at the target position and is connected with the receiver; the measuring antenna is used for sensing and measuring the radiation field signal and transmitting the radiation field signal to the receiver;
the receiver is used for receiving the N radiation field signals, performing separation processing on the N radiation field signals to obtain excitation signals corresponding to the N microwave radiation sources, and calculating time difference and phase difference of the N excitation signals of the frequency synthesizer at the target position; and adjusting a gating time gate of the frequency synthesis excitation signal according to the calculated time difference and phase difference to realize coherent synthesis of the field intensity of the radiation source for time slot excitation calibration.
10. The coherent combination system of radiation source field strength for time slot excitation calibration of claim 9, wherein: the radio frequency front end comprises a variable attenuator, an amplitude limiting low-noise amplifier, a band-pass filter, a down-conversion module, a gain control module, an AD sampling module, a digital pre-selection filter and a digital quadrature down-conversion module which are sequentially connected;
the measuring antenna is connected with the variable attenuator; the receiver is connected with the digital quadrature down-conversion module;
the variable attenuator is used for adjusting the power of the radiation field signal;
the amplitude limiting low-noise amplifier is used for amplifying the radiation field signal processed by the variable attenuator;
the band-pass filter is used for filtering the amplified radiation field signal;
the down-conversion module is used for performing down-conversion on the filtered radiation field signal;
the gain control module is used for carrying out automatic gain control on the radiation field signal after the down-conversion;
the AD sampling module is used for converting the radiation field signal after automatic gain control into a digital signal;
the digital pre-selection filtering is used for image interference suppression before quadrature down-conversion of the digital signal;
and the digital quadrature down-conversion module is used for converting the digital signal into a corresponding complex baseband signal.
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