阅读说明：本技术 一种具有保护通道的单脉冲雷达无盲区测距方法和系统 (non-blind area ranging method and system for monopulse radar with protection channel ) 是由 杨明远 王晓冰 江利中 黄勇 邹波 许颖莹 于 2019-10-16 设计创作，主要内容包括：本发明公开一种具有保护通道的单脉冲雷达无盲区测距方法和系统,系包含缝隙阵列主天线、保护天线、高频头、环形器、中频接收机、信号处理机、二次电源、发射机。本发明为单脉冲体制,由缝隙阵列主天线周期发射高频脉冲信号,保护天线实时接收目标回波信号；一发一收,实现收发分置；当无测距盲区时,使用缝隙阵列主天线接收到的回波形成和通道、方位差通道和俯仰差通道数据,三通道数据进行目标距离测量；当有测距盲区时,缝隙阵列主天线作为发射,保护天线接收回波数据形成保护通道数据；保护天线实时接收实现无盲区距离观测,达到米级距离测量的要求；最后利用脉冲法进行距离测量,结合脉冲压缩提高测距的精度,以满足雷达测距精度要求。(the invention discloses a non-blind area distance measuring method and system for a monopulse radar with a protection channel. The invention is a monopulse system, a slot array main antenna periodically transmits high-frequency pulse signals, and an antenna is protected to receive target echo signals in real time; transmitting and receiving to realize separate transmitting and receiving; when no ranging blind area exists, forming sum channel, azimuth difference channel and elevation difference channel data by using echoes received by the slot array main antenna, and measuring the target distance by using the three-channel data; when a ranging blind area exists, the main antenna of the slot array is used for transmitting, and the protection antenna receives echo data to form protection channel data; the antenna is protected to receive in real time to realize non-blind area distance observation, and the requirement of meter-level distance measurement is met; and finally, the distance measurement is carried out by using a pulse method, and the precision of distance measurement is improved by combining pulse compression so as to meet the requirement of radar distance measurement precision.)

1. the utility model provides a monopulse radar non-blind area ranging system with protection passageway which characterized in that contains:

A transmitter (8) that generates and transmits a first pulse transmission signal;

The slot array main antenna (1), the first pulse transmitting signal is sent to the slot array main antenna (1) through a circulator (4), the slot array main antenna (1) radiates the first pulse transmitting signal, and the first pulse transmitting signal radiated to a space forms an echo through the reflection of an object in the space; the slot array main antenna (1) receives the echo periodically, and the echo forms a sum channel echo signal, a azimuth difference echo channel signal and a pitch difference channel echo signal through a sum difference device in the slot array main antenna (1);

The protection antenna (2) is parasitic on the slot array main antenna (1), and the protection antenna (2) receives the transmitted echo in real time and forms a protection channel echo signal;

the high-frequency head (3) is used for receiving the sum channel echo signal, the azimuth difference channel echo signal, the pitch difference channel echo signal and the protection channel echo signal and outputting corresponding four paths of intermediate frequency echo data;

An intermediate frequency receiver (5) which receives four paths of intermediate frequency echo data and respectively outputs corresponding IQ orthogonal baseband echo signals;

The signal processor (6) is used for receiving the baseband echo signals corresponding to the channels and selectively processing the current baseband echo signals according to whether the ranging blind area exists or not; when a ranging blind area exists, signal processing is carried out on a baseband echo signal corresponding to the protection channel; and when the ranging blind area does not exist, respectively processing the baseband echoes corresponding to the channel, the azimuth difference channel and the pitch difference channel.

2. The monopulse radar blind spot-free ranging system according to claim 1, further comprising: and the secondary power supply (7) is used for converting the primary power supply into the secondary power supply and supplying power to each module.

3. The monopulse radar blind spot free ranging system according to claim 1 or 2, wherein the transmitter (8) selects an operating frequency according to an operating frequency point provided by the signal processor (6), a reference frequency generated by an internal frequency source of the transmitter (8) is up-converted to obtain a microwave signal, the microwave signal is mixed with a coded signal sent by the intermediate frequency receiver (5) and up-converted to a fixed operating frequency to form a first pulse transmitting signal with the fixed operating frequency, and the first pulse transmitting signal is subjected to transceiving isolation by the circulator (4) and finally modulated and radiated by the slot array main antenna (1).

4. the monopulse radar blind spot-free ranging system according to claim 1, wherein the sum channel echo signal, the azimuth difference channel echo signal, the pitch difference channel echo signal and the protection channel echo signal are input to the tuner (3) and are filtered, amplified and down-converted to obtain the corresponding four intermediate frequency echo data.

5. The monopulse radar blind spot free ranging system according to claim 1 or 4, wherein the intermediate frequency receiver (5) filters, amplifies and IQ-quadrature demodulates the four intermediate frequency echo data received by it to obtain the corresponding baseband echo signals, respectively.

6. The monopulse radar blind area-free ranging system according to claim 1, wherein the signal processing performed by the signal processor (6) comprises:

performing pulse pressure processing, coherent accumulation and target detection processing on the selected baseband echo;

and when the target is detected, calculating the current target distance R-c-t/2 according to the time delay t between the selected echo data and the first pulse transmitting signal, wherein c is the propagation speed of the electromagnetic wave in the space.

7. the monopulse radar blind spot free ranging system according to claim 6, further comprising: and carrying out filtering processing on the calculated target distance R.

8. A monopulse radar non-blind area ranging method of the monopulse radar non-blind area ranging system according to any one of claims 1 to 7, comprising the steps of:

S1, the transmitter (8) generates and transmits a first pulse transmission signal with fixed frequency;

s2, isolating the first pulse transmitting signal through a circulator (4) and sending the first pulse transmitting signal to a slot array main antenna (1);

s3, radiating the first pulse transmitting signal by a slot array antenna (1);

S4, the first pulse transmitting signal radiated to the space forms an echo through reflection, and the echo is received by the slot array main antenna (1) periodically and the protective antenna (2) in real time; the target echo received by the slot array main antenna (1) forms a sum channel echo signal, a azimuth difference echo channel signal and a pitch difference channel echo signal through an internal sum-difference device, and the target echo received by the protection antenna (2) forms a protection channel echo signal;

S5, transmitting the four-channel echo signals to a high-frequency head (3), filtering and amplifying the four-channel echo signals by the high-frequency head (3), and performing down-conversion to obtain corresponding four-channel intermediate frequency echo signals respectively;

s6, the intermediate frequency receiver (5) receives the intermediate frequency echo signals of the four channels, and filters, amplifies and orthogonally demodulates the intermediate frequency echo signals of the four channels to respectively obtain corresponding IQ orthogonally demodulated baseband echo signals;

S7, the baseband echo signal is sent to the signal processor (6), and the signal processor (6) performs selection processing on the current baseband echo signal: if a ranging blind area is generated, signal processing is carried out on a baseband echo signal of the protection channel; if no ranging blind area is generated, receiving baseband echo signals corresponding to the sum channel, the azimuth difference channel and the pitch difference channel for signal processing;

s8, the signal processor (6) carries out pulse pressure processing, coherent accumulation and target detection processing on the selected echo;

S9, if a target is detected, calculating a current target distance R ═ c × t/2 according to a time delay t between the selected echo data and the first pulse transmission signal, where c is a propagation speed of the electromagnetic wave in the space; if the target is not detected, the method returns to the step S1 directly, and the steps S1-S9 are circularly carried out until the target is detected and the target distance is calculated.

9. the monopulse radar blind spot-free ranging system according to claim 8, wherein the step S1 further comprises the following processes:

The transmitter (8) selects a fixed frequency to be generated according to a working frequency point generated by the signal processor (6), and an internal frequency source of the transmitter (8) generates a reference frequency signal and modulates and power-amplifies the frequency signal to form a microwave signal; the microwave signal and a coding signal generated by an intermediate frequency receiver (5) are subjected to up-conversion frequency mixing to obtain a first pulse transmitting signal with fixed frequency.

10. The monopulse radar blind spot-free ranging system according to claim 8 or 9, further comprising the process of:

S10, filtering the calculated target distance R to improve the ranging precision;

and S11, outputting the measured target distance information to finish the distance measurement of the target.

Technical Field

the invention relates to the technical field of radar ranging, in particular to a method and a system for ranging a monopulse radar with a protection channel without a blind area.

Background

The ranging methods commonly used by radar mainly include pulse method ranging and frequency modulation method ranging (FMCW). The pulse method calculates the target distance by calculating the time difference between the transmitted pulse and the received pulse. The fm continuous wave ranging is to transmit a frequency-modulated constant amplitude continuous wave signal, and use the frequency difference between an echo signal and the transmitted signal, that is, target distance information included in the difference frequency to perform ranging. The pulse method has the advantages of high tracking precision, long action distance and good anti-interference performance; but with a dead distance zone. The advantages of the frequency modulation continuous wave radar ranging are that there is no distance blind area, very close target can be measured, and simultaneously the measuring distance resolution is high and the radiation is small. But has the problems of difficult complete isolation of the transmitting and receiving channels, limited target distance measurement and the like.

Related patent 3 is retrieved through patent retrieval, wherein an FMCW radar ranging method and device (patent application No. 201010292116.9, patent publication No. CN101957446A) discloses a radar ranging method and device, which make judgment according to phase difference method correction conditions and calculate distance from corrected intermediate frequency. The method uses frequency modulation continuous waves, and the action distance is limited; a radar ranging and angle measuring method based on difference beam modulation and waveform analysis (patent application No. 201310585874.3, patent publication No. CN103616679A) discloses a radar ranging and angle measuring method based on difference beam modulation and waveform analysis, wherein a monopulse radar is co-located in a transmitting and receiving mode, the transmitting and receiving switching requires time, and the non-blind area distance measurement cannot be realized; a measuring device and a compensation correction method for FMCW radar ranging precise correction are disclosed (patent application No. 200910092240.8, patent publication No. CN 101666874A). The method utilizes a frequency method for ranging, the distance measurement is limited, and the separate cost of a transmitting antenna and a receiving antenna is high.

two related papers are searched through paper retrieval, wherein a derivative ratio value-based frequency modulation continuous wave distance measurement method aims at continuous wave distance measurement, and the method also has the defect of short distance measurement range. The high-frequency radar phase coding signal distance shielding characteristic research is a research on the distance measurement of the monostatic radar which can not receive and transmit simultaneously, although the method can shorten the short-distance measurement range, the method can not realize the non-blind area distance measurement.

The monopulse radar ranging of the above three patent applications can not realize non-blind area ranging, and continuous wave ranging has a shorter ranging range although non-blind area ranging can be realized.

Based on the above, the invention develops a monopulse radar non-blind area ranging method with a protection channel, which can greatly improve the ranging range of the radar by using a monopulse system and can realize the non-blind area ranging range by combining with the real-time receiving of the protection channel, and utilizes the main antenna of the slot array to transmit pulse signals and the protection antenna to receive echo signals, and the transmitting and receiving are carried out one by one to realize the transmitting and receiving separately; on one hand, after the main antenna of the slot array finishes the transmission of signals, the receiving and sending switching is carried out, and the echo signals are periodically received; on the other hand, the protection antenna receives echo signals in real time.

Disclosure of Invention

the invention aims to provide a monopulse radar non-blind area ranging method and a monopulse radar non-blind area ranging system with a protection channel, wherein monopulse technology is combined with the protection channel to realize monopulse non-blind area ranging; the distance measurement method utilizes a single-pulse distance measurement technology to improve the detection distance of a target, simultaneously utilizes a main antenna of a slot array to transmit pulse signals, protects the antenna to receive echo signals to form protection channel echo data, realizes the transceiving split position to overcome a short-distance measurement blind area, and realizes ultra-short distance measurement; when no ranging blind area exists, the slot array main antenna is used for periodically transmitting pulse signals and receiving echo data, and when the ranging blind area exists, the echo data received by the antenna is protected for ranging.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a monopulse radar non-blind area ranging system with a protection channel comprises:

A transmitter generating and transmitting a first pulse transmission signal;

the first pulse transmitting signal is sent to the slot array main antenna through a circulator, the slot array main antenna radiates the first pulse transmitting signal, and the first pulse transmitting signal radiated to a space forms an echo through the reflection of an object in the space; the main antenna of the slot array receives the echo periodically and the echo forms a sum channel echo signal, an azimuth difference echo channel signal and a pitch difference channel echo signal through a sum difference device in the main antenna of the slot array;

The protection antenna is parasitic on the slot array main antenna and receives the transmitted echo in real time to form a protection channel echo signal;

The high-frequency head receives the sum channel echo signal, the azimuth difference channel echo signal, the pitch difference channel echo signal and the protection channel echo signal and outputs corresponding four paths of intermediate frequency echo data;

The intermediate frequency receiver receives four paths of intermediate frequency echo data and respectively outputs corresponding IQ orthogonal baseband echo signals;

The signal processor is used for receiving the baseband echo signals corresponding to each channel and selectively processing the current baseband echo signals according to whether a ranging blind area exists or not; when a ranging blind area exists, signal processing is carried out on a baseband echo signal corresponding to the protection channel; and when the ranging blind area does not exist, respectively processing the baseband echoes corresponding to the channel, the azimuth difference channel and the pitch difference channel.

the monopulse radar non-blind area distance measuring system further comprises: and the secondary power supply is used for converting the primary power supply into a secondary power supply and supplying power to each module.

Preferably, the transmitter selects an operating frequency according to an operating frequency point provided by the signal processor, the reference frequency generated by the internal frequency source of the transmitter performs up-conversion to obtain a microwave signal, the microwave signal and the coded signal sent by the intermediate frequency receiver perform frequency mixing and up-conversion to a fixed operating frequency to form a first pulse transmitting signal with the fixed operating frequency, the first pulse transmitting signal is subjected to transceiving isolation by the circulator, and finally the first pulse transmitting signal is modulated and radiated by the slot array main antenna.

preferably, the sum channel echo signal, the azimuth difference channel echo signal, the pitch difference channel echo signal, and the protection channel echo signal are input to the tuner, filtered, amplified, and down-converted to obtain the corresponding four channels of intermediate frequency echo data.

Preferably, the intermediate frequency receiver performs filtering, amplification and IQ quadrature demodulation on the four paths of intermediate frequency echo data received by the intermediate frequency receiver to obtain corresponding baseband echo signals respectively.

preferably, the signal processing performed by the signal processor includes: performing pulse pressure processing, coherent accumulation and target detection processing on the selected baseband echo; and when the target is detected, calculating the current target distance R-c-t/2 according to the time delay t between the selected echo data and the first pulse transmitting signal, wherein c is the propagation speed of the electromagnetic wave in the space.

Preferably, the monopulse radar non-blind area ranging system further comprises: and carrying out filtering processing on the calculated target distance R.

The invention also provides a monopulse radar non-blind area distance measuring method of the monopulse radar non-blind area distance measuring system, which comprises the following steps:

s1, the transmitter generates and transmits a first pulse transmission signal with fixed frequency;

s2, isolating the first pulse transmitting signal through a circulator and sending the first pulse transmitting signal to the main antenna of the slot array;

S3, radiating the first pulse emission signal by a slot array antenna;

S4, reflecting the first pulse transmitting signal radiated to the space to form an echo, and periodically receiving the echo by the main antenna of the slot array and receiving the echo in real time by the protective antenna; the target echo received by the main antenna of the slot array forms a sum channel echo signal, a azimuth difference echo channel signal and a pitch difference channel echo signal through an internal sum-difference device, and the target echo received by the protection antenna forms a protection channel echo signal;

S5, transmitting the four-channel echo signals to a high-frequency head, filtering and amplifying the four-channel echo signals by the high-frequency head, and performing down-conversion to obtain corresponding four-channel intermediate frequency echo signals respectively;

S6, the intermediate frequency receiver receives the intermediate frequency echo signals of the four channels, and the intermediate frequency echo signals of the four channels are filtered, amplified and orthogonally demodulated to respectively obtain corresponding IQ orthogonally-demodulated baseband echo signals;

S7, sending the baseband echo signal to the signal processor, and the signal processor performs selection processing on the current baseband echo signal: if a ranging blind area is generated, signal processing is carried out on a baseband echo signal of the protection channel; if no ranging blind area is generated, receiving baseband echo signals corresponding to the sum channel, the azimuth difference channel and the pitch difference channel for signal processing;

S8, the signal processor performs pulse pressure processing, coherent accumulation and target detection processing on the selected echo;

s9, if a target is detected, calculating a current target distance R ═ c × t/2 according to a time delay t between the selected echo data and the first pulse transmission signal, where c is a propagation speed of the electromagnetic wave in the space; if the target is not detected, the method returns to the step S1 directly, and the steps S1-S9 are circularly carried out until the target is detected and the target distance is calculated.

Preferably, the step S1 further includes the following steps: the transmitter selects a fixed frequency to be generated according to a working frequency point generated by the signal processor, an internal frequency source of the transmitter generates a reference frequency signal, and the frequency signal is modulated and power-amplified to form a microwave signal; the microwave signal and a coding signal generated by the intermediate frequency receiver are subjected to up-conversion frequency mixing to obtain a first pulse transmitting signal with fixed frequency.

preferably, the monopulse radar non-blind area ranging system further comprises the following processes: s10, filtering the calculated target distance R to improve the ranging precision; and S11, outputting the measured target distance information to finish the distance measurement of the target.

compared with the prior art, the invention has the beneficial effects that: (1) the distance measuring system is provided with a protection channel, a main antenna of a slot array finishes the emission of radar pulse signals and the reception of target echoes and forms three-channel data, namely data of a sum channel, an azimuth difference channel and a pitch difference channel, the protection antenna is integrated on the main antenna of the slot array and only occupies one slot of the main antenna of the slot array, the protection antenna realizes the real-time reception of the target echoes to form protection channel data, the protection channel is a link from the echoes to the rear end of a signal processor through the front end of the protection antenna, the protection antenna and the slot array antenna realize the receiving and sending separately placement, and the distance non-blind area detection form is realized; (2) the method adopts a pulse method for ranging, a radar transmitter can transmit a series of high-frequency signals with a certain repetition period through an antenna, a relative delay t is formed between a transmitting signal and an echo signal, the distance R between a target and a radar is calculated to be ct/2, and c is the propagation speed of electromagnetic waves in space; the distance measurement system is also a single-pulse system, and can realize a long-distance measurement range by utilizing the characteristic of high energy of a single-pulse transmitting signal; (3) the distance measurement method of the invention is an integrated design of a protection channel and a single pulse, is not influenced by the receiving and transmitting switching time and the pulse transmitting time, and can realize single-pulse ultra-short distance measurement; the distance measuring method of the invention is an integrated design of the protective antenna and the main antenna, and compared with the characteristics of simple structure, low cost and the like of the receiving and transmitting split antenna; (4) the method adopts a channel selection mode, if the target distance is closer to a ranging blind section, the data of a protection channel is selected for processing, otherwise, the data of a sum channel, an azimuth difference channel and a pitch difference channel are used for processing, and then down-conversion, filtering, amplification and other processing are carried out on an echo signal; (5) the invention adopts a pulse compression technology, in order to meet the requirement of radar ranging precision, the pulse compression processing is carried out on echo signals, and the wide pulse echoes are compressed into narrow pulse echoes; the relative distance of a target is measured by measuring the peak position of a signal after pulse compression, a wide pulse signal is transmitted during the distance measurement by the pulse compression method, and a longer acting distance can be obtained when the peak power is lower; during receiving, the echo signals are compressed into narrow pulse signals through matched filtering, and the distance resolution is improved, namely, the pulse compression method can obtain a longer acting distance and a higher distance resolution at the same time; (6) the invention adopts distance filtering processing, and in order to obtain high distance measurement precision, the measured distance is filtered, and the final filtered distance value is output.

Drawings

FIG. 1 is a schematic diagram of a front-end antenna of a monopulse radar non-blind area ranging system according to the present invention;

FIG. 2 is a schematic diagram of a transmitting and receiving system of the monopulse radar blind-area-free ranging system of the present invention;

FIG. 3 is an antenna radiation range of the monopulse radar non-blind area ranging system of the present invention;

fig. 4 is a slot array antenna and a protection antenna pattern of the present invention;

FIG. 5 is a flow chart of the non-blind area ranging operation of the present invention;

fig. 6 shows the radar distance range of the present invention.

Detailed Description

in order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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.

as shown in fig. 1-6, the present invention provides a monopulse radar blind area-free ranging system with a protection channel, which mainly comprises a transceiver front end and a transceiver processing system, wherein the transceiver front end comprises a slot array main antenna 1, a protection antenna 2, a tuner 3 and a circulator 4, and the transceiver processing system comprises an intermediate frequency receiver 5, a signal processor 6, a secondary power supply 7 and a transmitter 8.

As shown in fig. 1, the distance measuring radar front-end antenna is a slot array main antenna 1 and a protection antenna 2. The slot array main antenna 1 is used for realizing the function of a common single pulse antenna, and the number of the slots is N, wherein N is far larger than 1. The protection antenna 2 is parasitic on the slot array main antenna 1, the slot array main antenna 1 and the protection antenna 2 are integrally designed, the protection antenna 2 only occupies one slot of the slot array main antenna 1, and the performance of the slot array main antenna 1 is not affected.

The slot array main antenna 1 mainly realizes the periodic transmission of high-frequency pulse signals and the reception of target echo signals and forms sum channel signals, azimuth difference channel signals and elevation difference channel signals; the protection antenna 2 mainly realizes real-time reception of a target echo signal and forms a protection channel signal; therefore, the protection antenna 2 completes receiving, the slot array antenna 1 completes transmitting, and one transmitting and one receiving are realized, so that separate receiving and transmitting are realized. When no ranging blind area exists, the echo signal received by the slot array main antenna 1 forms a sum channel signal, an azimuth difference channel signal and a pitch difference channel signal, and the three channels of data are used for measuring the target distance. When a ranging blind area exists, the main antenna 1 of the slot array is used for transmitting, and the protection antenna 2 receives echo data to form a protection channel signal. Therefore, the invention realizes the non-blind area distance observation by utilizing the protective antenna 2 to receive in real time, and meets the requirement of meter-level distance measurement. And finally, the distance measurement is carried out by using a pulse method, and the precision of distance measurement is improved by combining a pulse compression technology so as to meet the requirement of radar distance measurement precision.

as shown in fig. 2, the circulator 4 realizes isolation of the transmitting and receiving of the slot array main antenna 1; the transmitter 8 completes the generation of the pulse transmitting signal, sends the pulse transmitting signal to the circulator 4 and radiates out by the slot array main antenna 1, and generates a coherent local oscillator signal and sends the coherent local oscillator signal to the high-frequency head 3; the tuner 3 performs low-noise amplification and down-conversion processing of the received echo signal to obtain an intermediate frequency signal. The if receiver 5 provides the encoded signal for the transmitter 8 to generate the transmit signal, while the if receiver 5 mainly performs matched filtering, amplification and quadrature demodulation of the if signal, generating an IQ quadrature baseband signal for the signal processor 6. The signal processor 6 provides a working frequency point for selecting the working frequency of the transmitter 8, and at the same time, finishes the judgment of the working mode, receives the baseband signal of the intermediate frequency receiver 5, and performs sampling, pulse compression, accumulation, detection, measurement of the relative distance of the target and the like on the baseband signal. The secondary power supply 7 converts the primary power supply into a secondary power supply to supply power to each module and the single machine, and has a load short circuit or overcurrent protection function.

as shown in fig. 1 to 6, the principle of the blind-area-free ranging method of the monopulse radar with the protection channel of the present invention is as follows:

(1) The transmitter 8 quickly selects the working frequency according to the working frequency point provided by the signal processor 6; meanwhile, the reference frequency generated by the internal frequency source of the transmitter 8 is up-converted to obtain a microwave signal, the microwave signal and the coded signal sent by the intermediate frequency receiver 5 are subjected to frequency mixing and up-conversion to a fixed working frequency to form a required high-frequency pulse transmitting signal, the high-frequency pulse transmitting signal is transmitted, received and isolated by the circulator 4 and finally modulated and radiated by the slot array main antenna 1.

(2) Because the electromagnetic wave radiated to the space from the slot array antenna is reflected by a space object to form an echo, the slot array main antenna 1 receives a target echo signal and forms a sum channel, an azimuth difference channel and a pitching difference channel three-channel echo signal through a sum-difference device in the slot array main antenna 1; the protection antenna 2 directly and independently forms a path of protection channel echo signal and performs gain amplification processing. The received four-channel echo signals (sum channel echo signal, azimuth difference channel echo signal, pitch difference channel echo signal and protection channel echo signal) are sent to the high-frequency head 3, the high-frequency head 3 completes low-noise amplification of the four-channel echo signals, then local oscillation signals are distributed to four-channel receiving channels (sum channel, azimuth difference channel, pitch difference channel and protection channel), and the received echo signals are down-converted to intermediate frequency signals.

(3) The intermediate frequency signal is subjected to matched filtering, amplification and quadrature demodulation by an intermediate frequency receiver 5 to obtain baseband signals of a sum channel, a azimuth difference channel, a pitch difference channel and a protection channel in-quadrature (IQ modulation means that data is divided into two paths which are respectively subjected to carrier modulation, the two paths of carriers are mutually orthogonal, I is in-phase which is in-phase, and q is quadraturity which is orthogonal); finally, the baseband signals of the four paths of sum channels, the azimuth difference channel, the pitch difference channel and the protection channel in IQ orthogonality enter a signal processor 6, the signal processor 6 judges whether a ranging blind area exists or not and selects echo data: if no ranging blind area exists, selecting echo signals of a sum channel, a azimuth difference channel and a pitch difference channel to finish signal processing (such as signal pulse pressure, coherent accumulation and detection processing); if a ranging blind area exists, the echo signal of the protection channel is selected to carry out signal processing (for example, finishing signal pulse pressure and coherent accumulation and detection processing).

(4) And finishing the detection processing of the selected echo, and if the target is detected, performing distance measurement on the target. In order to meet the requirement of radar ranging accuracy, pulse pressure processing can be performed on the selected echo signal, and the wide pulse echo is compressed into the narrow pulse echo; meanwhile, in order to improve the signal to noise ratio, coherent accumulation processing can be carried out on the selected echo; then, target detection is carried out, if a target is detected, the relative delay t between the transmitting signal and the echo signal is compared, the distance R from the target to the radar is equal to ct/2, wherein c is the propagation speed of the electromagnetic wave in the space; and finally, in order to obtain high distance measurement precision, alpha-beta filtering processing is carried out on the measured distance, and a finally filtered distance value is output.

As shown in FIG. 3, the invention relates to a radar beam design of a monopulse radar blind-area-free ranging method and system with a protection channel, which mainly designs the coverage area of a transmitting beam of a slot array main antenna 1 and the receiving beam width of a protection antenna 2. And designing the number of the slits of the main antenna of the slit array to be N. The transmission beam of the main antenna 1 of the slot array is designed to be within a phi multiplied by phi solid angle range, and the receiving beam width of the protective antenna 2 covers +/-phi. As shown in fig. 4, the gain amplification processing is performed on the echo received by the protection antenna 2 at the rear end of the protection antenna 2, so that the gain of the received beam of the protection antenna 2 after processing should be greater than the secondary lobe level of the main antenna 1 of the slot array. The protection antenna 2 is parasitic on the main antenna 1 of the slot array, and the working bandwidth of the protection antenna 2 is consistent with that of the main antenna 1 of the slot array.

FIG. 6 is a diagram of the range of radar range, illustrating the range of the single pulse ranging blind zone from 0 to R_uAnd a non-blind area range R_u～R_mThe whole distance range is 0 to R_mthe range of the radar of the present invention.

as shown in fig. 5, the method for measuring distance without blind area by using monopulse radar with protection channel of the present invention includes the following steps:

Step S1, first, the transmitter 8 quickly selects a fixed frequency to be generated according to the operating frequency point generated by the signal processor 6; a frequency source inside the transmitter 8 generates a reference frequency signal, and modulates and power-amplifies the frequency signal to form a microwave signal; the microwave signal and the coded signal generated by the intermediate frequency receiver 5 are subjected to up-conversion frequency mixing to obtain a pulse transmitting signal with fixed frequency.

The pulse transmission signals in step S2 and step S1 are isolated by the circulator 4 and sent to the slot array main antenna 1.

The pulse transmission signal in step S3 and step S2 is radiated from the slot array antenna 1.

Step S4, the electromagnetic wave radiated to the space by the slot array antenna is reflected by the object in the space to form an echo, and the echo is periodically received by the slot array main antenna 1 and is received by the protective antenna 2 in real time; echo data of a sum channel, an azimuth difference channel and a pitching difference channel are formed by the echo received by the main antenna 1 of the slot array through an internal sum-difference device, and echo data of a protection channel are formed by the echo received by the protection antenna 2.

The four paths of echo data (sum channel, azimuth difference channel, pitch difference channel, and protection channel data) in step S5 and step S4 are sent to the tuner 3, and are filtered and amplified by the tuner 3 and down-converted to obtain four paths of intermediate frequency echo data.

Step S6, the if receiver 5 receives the four-channel if echo data in step S5, and performs filtering, amplification and quadrature demodulation on the four-channel if echo data to obtain corresponding baseband IQ quadrature-demodulated echo data, respectively.

Step S7, the baseband echo data is sent to the signal processor 6, the signal processor 6 carries out selection processing on the current echo, and the signal processor 6 judges whether the monopulse distance measurement is blocked to generate a distance measurement blind area according to the distance of the front target: and if a ranging blind area is generated, receiving and processing the echo data of the protection channel, otherwise, receiving and processing the echo data of the sum channel, the azimuth difference channel and the pitch difference channel.

Step S8, the signal processor 6 performs pulse pressure processing, coherent accumulation, and target detection processing on the selected echo.

Step S9, if a target is detected, calculating a current target distance R ═ ct/2 according to a time delay t between the selected echo data and a pulse transmission signal (i.e., the pulse transmission signal that the transmitter starts to transmit), where c is a propagation speed of the electromagnetic wave in the space; if no target is detected, the process returns to step S1.

and step S10, performing alpha-beta filtering processing on the calculated target distance R to improve the distance measurement precision.

And step S11, outputting the measured target distance information, finishing the distance measurement of the target, and returning to step S1.

in the design of the ranging radar system, the ranging method uses a monopulse system, in the monopulse radar system, the slot array main antenna is used as a monopulse antenna, and the slot array main antenna transmits a high-frequency pulse signal with a certain repetition period.

The invention takes a coded signal as an example, the frequency of the coded signal is designed to be f, the pulse width of a transmitted signal is tau, the pulse repetition frequency is prf, and the number of pulse coherent accumulation is M points. For the ranging range design of the ranging radar, because the repetition frequency of the pulse is prf, the range delay formula is as follows:

Wherein R is₁for the theoretical non-fuzzy action distance, prf is a pulse repetition period, and c is the space propagation speed of the electromagnetic wave; the range of the unambiguous distance obtained by calculation is 0 to R₁Within the range. And by the radar power equation:

Wherein, P_τfor emission of the peak power of the pulse, τ is the pulse width, G_tIs the antenna gain; lambda is the working wavelength, and sigma is the target reflection area; f₀Is the receiver noise figure; l, system loss; c. C_BIs a bandwidth correction factor; d₀To detect the signal-to-noise ratio; m is the number of coherent accumulation points; k is Boltzmann constant 1.38X 10^-23；T₀Is the effective noise temperature.

through calculation of a radar equation, the farthest acting distance of the radar is R under a certain detection signal-to-noise ratio_maxObtaining the range of the radar unambiguous distance from 0 to R by the radar equation_max. Thus taking R₁And R_maxThe minimum value of (d) as the radar maximum unambiguous distance is:

R_m＝min(R₁,R_max) (3)

0 to R in the range of the unambiguous distance_mif utilize slot array main antenna to carry out monopulse range finding, because unable echo of receiving and dispatching switching time of slot array main antenna and transmit pulse time quantum in, there is the measurement blind area to the short distance target, and the target distance measurement can't be accomplished to slot array main antenna, and wherein the biggest range blind area is:

R_u＝c(τ+t_tr)/2 (4)

wherein, t_trThe switching time is used for transceiving. Calculating to obtain the range of the blind zone from 0 to R_uAs shown in FIG. 6, 0 to R_ufor distance measurement of the shielding section, R_u～R_mThere is no occlusion segment for distance measurement. The invention can realize real-time measurement of the target distance by utilizing the protection channel to receive the echo signal in real time, and overcomes the problem of short-distance measurement blind area. The radar range of the invention is thus from zero range to the maximum unambiguous range R of the radar_m。

In summary, the distance measuring method of the present invention mainly uses a pulse method for distance measurement, and the radar transmitter generates a series of high frequency transmitting signals with a certain repetition period, and the signals are transmitted, received and isolated by the circulator and radiated into the space by the slot array main antenna. If a target exists on a transmission path of a transmitting signal, the target can reflect electromagnetic waves, three paths of echo data of a sum channel, an azimuth difference channel and a pitch difference channel are periodically received and formed by the main antenna of the slot array, and echo data of a protection channel are received and formed by the radar protection antenna in real time. And then, the echo signals of the sum channel, the azimuth difference channel, the pitch difference channel and the protection channel are filtered, amplified, down-converted and the like by the high-frequency head to obtain intermediate-frequency echo signals. And the intermediate frequency echo signal is sent to an intermediate frequency receiver and then quadrature demodulation is carried out to obtain baseband IQ echo data. And sending the four paths of baseband IQ echo data to a signal processor, judging whether a ranging blind area exists or not, and selecting echo signals of a sum channel, a azimuth difference channel and a pitch difference channel to perform signal processing if the ranging blind area does not exist. And if a ranging blind area exists, selecting a protection path echo signal to finish signal processing.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.