阅读说明：本技术 一种适用于非零带宽信号的频带采样微波被动观测系统 (Frequency band sampling microwave passive observation system suitable for non-zero bandwidth signal ) 是由 万珺之 于 2019-11-02 设计创作，主要内容包括：本发明涉及一种适用于非零带宽信号的频带采样微波被动观测系统,包括：空间2元天线阵,接收机,子带分割器,子带相关器,傅里叶变换器；非零带宽信号到达空间2元天线阵后,经接收机处理获得2路基带信号；2路基带信号经子带分割器分割为若干子带后,子带相关器对相同频率的子带进行相关运算,生成相关结果序列,最后通过傅里叶变换器生成波束；生成波束时,较之现有的微波被动观测系统,新系统的天线阵所需的阵元数目及相应的硬件成本显著减少。(The invention relates to a frequency band sampling microwave passive observation system suitable for non-zero bandwidth signals, which comprises: the system comprises a spatial 2-element antenna array, a receiver, a sub-band divider, a sub-band correlator and a Fourier transformer; after the non-zero bandwidth signal reaches the spatial 2-element antenna array, a receiver processes the signal to obtain a 2-element baseband signal; 2, after the baseband signal is divided into a plurality of sub-bands by a sub-band divider, a sub-band correlator performs correlation operation on the sub-bands with the same frequency to generate a correlation result sequence, and finally, a wave beam is generated through a Fourier transformer; when the wave beam is generated, compared with the existing microwave passive observation system, the number of array elements required by the antenna array of the new system and the corresponding hardware cost are obviously reduced.)

1. A frequency-band sampled microwave passive observation system suitable for non-zero bandwidth signals, comprising: the system comprises a spatial 2-element antenna array (1), a receiver (2) and a Fourier transformer (5); characterized in that, the system also includes: a subband divider (3), a subband correlator (4);

the space 2-element antenna array (1) is connected with the receiver (2) and is used for receiving microwave signals transmitted by a target and transmitting the microwave signals to the receiver (2);

the receiver (2) is respectively connected with the space 2-element antenna array (1) and the sub-band divider (3) and is used for converting microwave signals from the antennas into baseband signals;

the sub-band divider (3) is respectively connected with the receiver (2) and the sub-band correlator (4) and is used for dividing the baseband signal from the receiver (2) into a plurality of sub-bands;

the sub-band correlator (4) is respectively connected with the sub-band divider (3) and the Fourier transformer (5), and is used for performing correlation processing on the same-frequency sub-bands of the array elements 1 and 2 and extracting a spatial phase complex factor corresponding to each frequency;

the Fourier transformer (5) is connected with the sub-band correlator (4) and is used for transforming a sequence formed by N discrete complex samples with periodically changed phases into a normal beam through Fourier transform;

the spatial 2-element antenna array (1) comprises: array element 1 (6) and array element 2 (7) which receive non-zero bandwidth microwave signals transmitted by a target at different spatial positions;

the receiver (2) comprises: receiver 1 (8) and receiver 2 (9) which convert microwave signals received by array element 1 (6) and array element 2 (7) into baseband signals respectively.

2. The passive observation system for microwave sampling in frequency band suitable for non-zero bandwidth signal as claimed in claim 1, wherein: the subband divider (3) comprises: subband divider 1 (10) and subband divider 2 (11);

a subband divider 1 (10) divides the baseband signal from the receiver 1 (8) into N subbands;

the subband divider 2 (11) divides the baseband signal from the receiver 2 (9) into N subbands.

3. The passive observation system for microwave sampling in frequency band suitable for non-zero bandwidth signal as claimed in claim 1, wherein: the subband correlator (4) comprises: an intra-frequency subband complex conjugate multiplier (12) and an intra-frequency subband integrator (13);

a same-frequency subband complex conjugate multiplier (12) performs complex conjugate multiplication on each 1 subband from the subband divider 1 (10) and the same frequency subband from the subband divider 2 (11);

an intra-frequency subband integrator (13) integrates the output sequence produced by each intra-frequency subband complex conjugate multiplier (12) to produce N discrete complex samples with periodically varying phase.

Technical Field

The invention relates to the field of microwave passive observation, in particular to a frequency band sampling microwave passive observation system suitable for non-zero bandwidth signals.

Background

The existing microwave passive observation systems based on antenna arrays can be divided into two categories: based on the phased array principle and on the interferometric synthetic aperture principle, both belong to spatial sampling systems.

Taking a one-dimensional condition as an example, the principle of implementing beamforming by spatial sampling can be briefly described as follows: the target transmits a narrowband signal whose bandwidth is much smaller than the center frequency, so the spatial sampling system treats the narrowband signal as a single frequency when forming the beam. Assuming that the array elements are arranged at equal intervals in the antenna array, the spatial phase complex factor observed by the nth array element (N =1,2,3, …, N) is shown as follows:

wherein k is₀Is the wave number, r, corresponding to the center frequency of the narrowband signal₀Is the 1 st array elementDistance to target, Δ r is distance change step, r₀And n-1 is the distance from the nth array element to the target. The spatial phase complex factor samples observed by all array elements form a discrete complex sequence with periodically changed phase, and the sequence is subjected to Fourier transform to form a beam. Fig. 1 is a schematic diagram of the beam forming principle of the space sampling microwave passive observation system.

In order to ensure a sufficiently high spatial sampling rate, the space between adjacent array elements in the antenna array of the spatial sampling system must be sufficiently small, otherwise, spatial undersampling can cause spatial frequency aliasing, and beam pointing is deviated. Furthermore, if the antenna array of the spatial fully sampled system contains only 2 array elements, then grating lobes must be present in the generated beam in addition to the main lobe. Grating lobes can severely interfere with normal observation of the target.

A grating lobe-free beam with no aliasing at spatial frequencies is called a normal beam. For a spatial sampling system, in order to ensure that a normal beam is generated, if other conditions are not changed, the higher the spatial resolution is, the more array elements are required, and the higher the hardware complexity and cost are.

Disclosure of Invention

The invention aims to enable a microwave passive observation system to generate normal beams when the number of array elements contained in an antenna array is far less than that required for ensuring that a space sampling system generates normal beams. This patent proposes a passive observation system of frequency band sampling microwave suitable for nonzero bandwidth signal, includes: the space 2-element antenna array, a receiver and a Fourier transformer; characterized in that, the system also includes: a subband divider, a subband correlator;

the space 2-element antenna array is connected with a receiver and is used for receiving microwave signals transmitted by a target and transmitting the microwave signals to the receiver;

the receiver is respectively connected with the space 2-element antenna array and the sub-band divider and is used for converting microwave signals from the antenna into baseband signals;

the sub-band divider is respectively connected with the receiver and the sub-band correlator and is used for dividing the baseband signal from the receiver into a plurality of sub-bands;

the sub-band correlator is respectively connected with the sub-band divider and the Fourier transformer and is used for carrying out correlation processing on the same-frequency sub-bands of the array elements 1 and 2 and extracting a spatial phase complex factor corresponding to each frequency;

the Fourier transformer is connected with the sub-band correlator and is used for transforming a sequence formed by N discrete complex samples with periodically changed phases into a normal beam through Fourier transform.

The spatial 2-element antenna array comprises: array element 1 and array element 2, which receive the non-zero bandwidth microwave signal transmitted by the target at different spatial positions;

the receiver comprises: receiver 1 and receiver 2, which convert the microwave signals received by array element 1 and array element 2 into baseband signals, respectively.

As a further refinement of the above technical solution, the subband divider includes: a sub-band divider 1 and a sub-band divider 2;

the sub-band divider 1 divides the baseband signal from the receiver 1 into N sub-bands;

the subband splitter 2 splits the baseband signal from the receiver 2 into N subbands.

As a further refinement of the above technical solution, the subband correlator includes: a same-frequency sub-band complex conjugate multiplier and a same-frequency sub-band integrator;

the same-frequency sub-band complex conjugate multiplier performs complex conjugate multiplication on each 1 sub-band from the sub-band divider 1 and the same-frequency sub-band from the sub-band divider 2;

the same-frequency sub-band integrator integrates the output sequence generated by each same-frequency sub-band complex conjugate multiplier to generate N discrete complex samples with variable phase periods.

The frequency band sampling microwave passive observation system suitable for the non-zero bandwidth signal has the advantages that:

the system is based on frequency band sampling instead of space sampling, and can generate normal beams by using 2 array elements. As mentioned above, the conventional system based on spatial sampling cannot generate normal beams by using 2 array elements theoretically;

2, under the prerequisite of normal wave beam of generation, the required array element number of the system that this patent provided is less than the required array element number of the passive observation system of current microwave far away, and hardware complexity and cost are showing and are reducing.

Drawings

Fig. 1 is a schematic diagram of the beam forming principle of a spatial sampling microwave passive observation system.

Fig. 2 is a schematic diagram of the beam forming principle of the frequency band sampling microwave passive observation system.

Fig. 3 is a block diagram of a frequency band sampling microwave passive observation system suitable for non-zero bandwidth signals.

Fig. 4 is a schematic diagram of a signal processing flow.

Detailed Description

The invention is further described below with reference to the figures and examples.

Fig. 2 is a schematic diagram of the beam forming principle of the frequency band sampling microwave passive observation system. The principle of beamforming by band sampling is: under the 2-element array condition, the bandwidth of the narrowband signal is not equal to 0, so that the narrowband signal can be considered to contain a large number of single-frequency waves with different frequencies. The present invention further assumes: there are only a limited number of single-frequency waves of different frequencies throughout the band.

The frequency of the nth single frequency wave (N =1,2,3, …, N) is: f. of₀+ (n-1) Δ f, wherein f₀Is the frequency of the 1 st single frequency and Δ f is the step value of the frequency.

The spatial phase complex factor corresponding to the nth single frequency wave observed by the array element 1 can be expressed as:

wherein r is_a1The distance between the target and the array element 1; similarly, the spatial phase complex factor corresponding to the nth single frequency wave observed by the array element 2 can be expressed as:

wherein r is_a2Is the distance between the target and the array element 2; the correlation is performed by 2 space phase complex factors, which can be obtained as follows:

therefore, each monochromatic wave observed by array element 1 is correlated with the monochromatic wave of the same frequency observed by array element 2, so as to form a discrete complex sequence with the sample number of N and the phase period variation. Fourier transforming the sequence forms a single main peak beam.

If the observation signal is a continuous band containing an infinite number of frequencies, the band can be divided into N subbands by filtering, and then the subbands with the same center frequency are correlated to generate a discrete complex sequence with N samples and a periodically varying phase.

In addition, the frequency band sampling method can be adopted to form the beam only when the signal transmitted by the target is a non-zero bandwidth signal. If the target transmits a zero-bandwidth single-frequency signal, only 1 spatial phase complex factor can be generated, and the normal wave beam cannot be generated by performing Fourier transform on the spatial phase complex factor.

The following further explains the specific implementation of the frequency band sampling microwave passive observation system in combination with the basic principle of frequency band sampling beam forming.

Fig. 3 is a block diagram of a frequency band sampling microwave passive observation system suitable for non-zero bandwidth signals. Fig. 4 is a schematic diagram of a signal processing flow.

The space 2-element antenna array (1) comprises array elements 1 (6) and array elements 2 (7), and the array elements receive non-zero bandwidth microwave signals transmitted by a target at different space positions.

The receiver (2) comprises: receiver 1 (8) and receiver 2 (9) which convert microwave signals received by array element 1 (6) and array element 2 (7) into baseband signals respectively.

The subband divider (3) comprises: subband divider 1 (10) and subband divider 2 (11);

a subband divider 1 (10) divides the baseband signal from the receiver 1 (8) into N subbands;

a subband divider 2 (11) divides the baseband signal from the receiver 2 (9) into N subbands; to ensure that a normal beam is formed, the difference between the center frequencies of adjacent subbands must be small enough to ensure that the band is adequately sampled.

The subband correlator (4) comprises: an intra-frequency subband complex conjugate multiplier (12) and an intra-frequency subband integrator (13);

a same-frequency subband complex conjugate multiplier (12) performs complex conjugate multiplication on each 1 subband from the subband divider 1 (10) and the same frequency subband from the subband divider 2 (11);

an intra-frequency sub-band integrator (13) integrates the output sequence generated by each intra-frequency sub-band complex conjugate multiplier (12) to generate N discrete complex samples with periodically changing phases; the integration operation is to filter out interfering signals.

The Fourier transformer (5) is connected with the sub-band correlator (4) and is used for transforming the sequence of the N discrete complex samples with the periodically changed phase into a normal beam through Fourier transform.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.