CN108008346A - A kind of radar system based on two unit time-modulation arrays - Google Patents

Abstract

The invention discloses a radar system based on a two-unit time modulation array, which includes an antenna array for receiving electromagnetic waves in space and radiating electromagnetic energy to space; When in the receiving state, the switch is in the modulating state; the power splitter distributes the energy of the transmitted signal to the two antenna arrays equally, and combines the energy of the received signal on the two antenna arrays; the single-pole double-throw RF switch controls the transmission and reception of the radar system The state; the control and signal processing unit controls the single-pole single-throw radio frequency switch and the single-pole double-throw radio frequency switch, and analyzes the spectrum characteristics of the received signal to estimate the incident direction of the received signal. The invention does not need mechanical scanning or electronic scanning, and aims at the simultaneous tracking of multiple targets in the radar system, adopts a two-unit time modulation array to transmit and receive pulse signals, and estimates the positions and directions of multiple targets through signal processing.

Description

A Radar System Based on Two-element Time Modulation Array

technical field

The invention belongs to the technical field of radar engineering, in particular to a radar system based on a two-unit time modulation array capable of simultaneously detecting multiple targets in different directions.

Background technique

Radar systems are widely used in both military and civilian fields. The traditional radar uses a mechanical rotating platform to complete the direction finding of the target through the narrow beam characteristic of the radar antenna itself. The phased array radar uses electronic scanning to complete narrow beam scanning by changing the amplitude and phase of each unit channel, and at the same time realizes the direction finding of the target.

The direction finding of the target echo by the existing radar system is completed by continuous scanning or electronic scanning, so a complex mechanical scanning or electronic scanning system is required.

Therefore, it is an urgent problem to be solved in this field to provide a radar system that can reduce the complexity of the existing radar system and realize simultaneous direction finding of radar echoes in multiple directions.

Do not find description or report similar to the present invention at present, also do not collect similar data both at home and abroad.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a radar system based on a two-unit time-modulated array. The radar system does not require mechanical scanning or electronic scanning systems. By analyzing the harmonic characteristics of received signals, Estimate the direction of the radar echo signal. The invention can simultaneously measure target echo signals in multiple directions, and can reduce the complexity and cost of the existing radar system.

The present invention is achieved through the following technical solutions.

A radar system based on a two-element time-modulated array comprising:

There are two antenna arrays 1, both of which are used to transmit radar pulse signals to space and receive target echo signals from space;

Single-pole single-throw radio frequency switch 2, said single-pole single-throw radio frequency switch 2 is two, and is connected with two antenna arrays 1 correspondingly respectively; The pulse signal is fed into the two antenna arrays 1 and transmitted to the space; when in the receiving state, the two single-pole single-throw radio frequency switches are in the modulation state, and the target echo signals received on the two antenna arrays 1 are connected in turn;

The power divider 3 is connected with two single-pole single-throw radio frequency switches 2. When in the transmitting state, the power divider 3 divides the energy of the radar pulse signal to be transmitted into two equal parts, and passes through the two single-pole single-throw radio frequency switches 2 respectively. Feed into the corresponding antenna array 1 for transmission; when in the receiving state, the power splitter receives the target echo signals received by the two antenna array 1 in turn and feeds them into the receiving branch;

The single-pole double-throw radio frequency switch 4 is connected with the power divider 3, and is used for gating the transmitting and receiving states of the radar pulse signal;

The power amplifier 5 is connected to the receiving end of the SPDT radio frequency switch 4, and is used to amplify the radar pulse signal;

The low noise amplifier 6 is connected to the transmitting end of the SPDT radio frequency switch 4, and is used to amplify the received target echo signal with low noise;

Mixer 7, said mixer 7 is two, and is respectively connected with power amplifier 5 and low-noise amplifier 6, is used for carrying out up-conversion and down-conversion to the signal of transmission and reception;

The local oscillator 8 is connected between the two mixers 7 and is used to provide a reference signal for the mixers 7;

Low-pass filter 9, said low-pass filter 9 is two, and is connected with two mixers 7 correspondingly respectively, wherein, the low-pass filter on the transmitting branch is also connected with digital-to-analog converter 10, uses To filter out the harmonic components produced in the digital-to-analog converter 10, the low-pass filter on the receiving branch is used to filter out the high-frequency components produced in the down-conversion;

Digital-to-analog converter 10 is connected with the low-pass filter on the transmitting branch, and is used to convert the digital intermediate frequency signal generated by the low-pass filter on the transmitting branch into an analog intermediate frequency signal;

The analog-to-digital converter 11 is connected with the low-pass filter on the receiving branch, and is used to convert the analog intermediate frequency signal received by the low-pass filter on the receiving branch into a digital signal;

The control and signal processing unit 12 is used for controlling the single pole single throw switch and the single pole double throw switch, generating radar pulse signals, analyzing the spectrum characteristics of the received signal and estimating the incident direction of the received signal.

Preferably, the control and signal processing unit 12 includes:

The control module is used to control the state of the single pole double throw switch and perform state control and modulation on the two single pole single throw switches;

A signal transmitting module, used to generate radar pulse signals;

The signal processing module is used for analyzing the spectrum characteristics of the received signal and estimating the incident direction of the received signal.

Preferably, the radar system based on the two-unit time modulation array includes the following parameters:

T: pulse repetition time of the radar;

τ: radar pulse duration;

Δt: time delay of the target echo relative to the transmitted pulse;

T _p : modulation cycle of the SPST RF switch; where, in the first half cycle, the receiving branch is connected to one of the two antenna arrays, and in the second half cycle, the receiving branch is connected to one of the two antenna arrays another.

Preferably, the signal processing module analyzes the spectral characteristics of the received signal and estimates the incident direction of the received signal, specifically:

The distance R of the target relative to the radar system can be calculated from the time delay of the target echo relative to the transmitted pulse:

where c is the speed of light in vacuum;

Assume that the carrier frequency of the transmitted pulse is F _c , and the target echo signal is periodically modulated by the SPST RF switch to generate a fundamental component with a carrier frequency of F _c and a harmonic with a carrier frequency of F _c ±kF _p Component, where k is the order of the harmonic, F _p is the switching frequency of the RF switch; if the RF local oscillator produces a single-frequency signal with a frequency of F _o , after passing through the mixer and the low-pass filter, the received signal contains The fundamental wave component with carrier frequency F _c -F _o , and the harmonic component with carrier frequency F _c -F _o ±kF _p ; after Fourier transform, the fundamental wave component is calculated as α ₀ , the first harmonic The wave component is α ₁ , then the angle θ of the incident direction of the target echo signal is:

Among them, D is the distance between the two antenna elements, and K is the wave number corresponding to the carrier frequency _Fc , namely:

A radar system based on a two-unit time modulation array provided by the present invention, its working principle is as follows:

The radar system has two working modes, namely transmitting mode and receiving mode. When the radar system works in the transmitting mode, radar pulse signals of equal amplitude and phase are fed into the two antenna arrays and radiated into the space. After the radar system transmits a radar pulse signal, it is controlled by the single-pole double-throw switch to enter the receiving state. In the receiving state, the single-pole single-throw radio frequency switches connected to the two antenna arrays control the received target echo signals to enter the receiving channel in turn. Due to the periodic modulation of the single-pole single-throw RF switch, the received target echo signal will generate fundamental wave components and various harmonic components. By comparing the mathematical relationship between the fundamental component and the first harmonic component, the direction of the target echo signal can be calculated. In the radar system proposed by the present invention, the distance information of the target is realized by comparing the time difference between the transmitted pulse and the echo signal.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention reduces the complexity of the radar system and realizes simultaneous direction finding of radar echoes in multiple directions;

2. The present invention does not require mechanical scanning or electronic scanning, and can simultaneously measure target echoes in various directions, thereby determining the orientation of multiple targets;

3. The present invention has the advantages of simple structure and low algorithm complexity, and is especially suitable for miniaturized platforms such as missiles, unmanned vehicles, and drones;

4. The present invention has the characteristics of low cost and is suitable for popularization.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the principle and structural block diagram of radar system of the present invention;

Fig. 2 is a schematic diagram of the radar system of the present invention transmitting radar pulses and receiving echo signals;

Fig. 3 is the radar pulse of launching and the echo signal of receiving in embodiment 1;

Fig. 4 is the frequency spectrum of the echo signal received in embodiment 1;

Fig. 5 is the radar pulse that transmits and the echo signal that receives in embodiment 2;

Fig. 6 is the three-dimensional time-frequency spectrum of the radar pulse transmitted in embodiment 2 and the echo signal received;

Fig. 7 is the two-dimensional time-frequency spectrum of the radar pulse transmitted in embodiment 2 and the echo signal received;

In the figure: 1 is the antenna array, 2 is the SPST RF switch, 3 is the power splitter, 4 is the SPDT RF switch, 5 is the power amplifier, 6 is the low noise amplifier, 7 is the mixer, 8 is the base vibration, 9 is a low-pass filter, 10 is a digital-to-analog converter, 11 is an analog-to-digital converter, and 12 is a control and signal processing unit.

Detailed ways

The following is a detailed description of the embodiments of the present invention: this embodiment is implemented on the premise of the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Example

This embodiment provides a radar system based on a two-unit time modulation array, which consists of:

Two-unit (two) antenna array 1: used to receive electromagnetic waves in space and radiate electromagnetic energy to space;

Two single-pole single-throw RF switches 2: when the system is in the transmitting state, the switch is in the closed state, and when the system is in the receiving state, the switch is in the modulating state;

Power divider 3: used to evenly distribute the energy of the transmitted signal to the two antenna arrays, and combine the energy of the received signal on the two antenna arrays;

SPDT RF switch 4: used to control the transceiver status of the radar system;

Control and signal processing unit 12: used to control the single-pole-single-throw radio frequency switch and the single-pole double-throw radio frequency switch, and analyze the spectrum characteristics of the received signal, and estimate the incident direction of the received signal;

This embodiment also includes: a power amplifier 5 , a low noise amplifier 6 , a mixer 7 , a radio frequency local oscillator 8 , a low-pass filter 9 , a digital-to-analog converter 10 and an analog-to-digital converter 11 . The working state of the radar system described in this embodiment is as follows:

When the radar system is in the transmitting state, the single pole double throw radio frequency switch is connected to the transmitting branch. The control and signal processing unit generates a digital radar pulse signal, which passes through a digital-to-analog converter 10, a low-pass filter 9, a mixer 8, a power amplifier, a single-pole double-throw radio frequency switch 4, a power divider 3, and a single-pole single-throw radio frequency switch 2 After that, it radiates into space through two antenna arrays 1 . At this time, the two single-pole single-throw RF switches are always in the closed state.

After the radar system transmits a radar pulse signal, the single-pole double-throw radio frequency switch is connected to the receiving branch. The target echo signal received by the antenna array 1 enters the power splitter 3 after being modulated by the SPST radio frequency switch 2 . After the received signal output by the power splitter passes through the SPDT RF switch 4, the low noise amplifier 6, the mixer 8, the low pass filter 9, and the analog-to-digital converter 11, it is compared and transmitted by the control and signal processing unit in the digital domain. The time delay between the pulse and the echo signal, estimating the range of the target. At the same time, the control and signal processing unit performs spectrum analysis on the received signal, and calculates the direction of the echo signal from the result of the spectrum analysis.

The control and signal processing unit 12 includes:

Control module: used to control the state of the single-pole double-throw radio frequency switch, and used for state control and modulation of two single-pole single-throw radio frequency switches.

Signal transmitting module: used to generate radar pulse signals;

Signal processing module: used to analyze the spectrum characteristics of the received signal and estimate the incident direction of the received signal;

FIG. 1 shows a schematic diagram of various parts and connection relationships of the radar system disclosed in this embodiment. Figure 2 shows a schematic diagram of the transmitted pulse signal and the received echo signal within a pulse repetition time of the radar. It can be seen from the figure that within a pulse repetition period, the radar transmits a single-frequency pulse signal, and then the system enters the receiving state and prepares to receive the target echo. The received echo signals are modulated by the single-pole single-throw radio frequency switch, so that the echo signals received on the two antenna arrays enter the receiving channel (receiving branch) in turn.

The main technical parameters of the radar system disclosed in this embodiment include:

T: pulse repetition time of the radar;

τ: radar pulse duration;

Δt: time delay of the target echo relative to the transmitted pulse;

T _p : modulation period of the SPST RF switch. Wherein, in the first half period, the receiving branch is connected to one of the two antenna arrays; in the second half period, the receiving branch is connected to the other antenna array of the two antenna arrays.

The distance of the target relative to the radar system can be calculated from the time delay of the target echo relative to the transmitted pulse:

where c is the speed of light in vacuum.

Assume that the carrier frequency of the radio pulse is F _c , and the echo signal is periodically modulated by the SPST RF switch, which will generate a fundamental wave component with a carrier frequency of F _c and harmonics with a carrier frequency of F _c ±kF _p Component, where k is the order of the harmonic, F _p is the switching frequency of the RF switch; if the RF local oscillator produces a single-frequency signal with a frequency of F _o , after passing through the mixer and the low-pass filter, the received signal contains The fundamental component with carrier frequency F _c -F _o , and the harmonic component with carrier frequency F _c -F _o ±kF _p . After Fourier transform, the fundamental wave component is calculated as α ₀ , and the first harmonic component is α ₁ , then the incident direction of the echo signal relative to the normal offset angle of the two-element antenna array is:

Among them, D is the distance between the two antenna elements, and K is the wave number corresponding to the carrier frequency _Fc , namely:

The above embodiments will be further described in detail below in conjunction with the accompanying drawings and specific examples.

Specific example 1. Single target echo detection

It is assumed that the antenna arrays forming the radar system of the present invention are omnidirectional, and the distance between the two antenna arrays is 1.5m. As shown in Figure 3, within a pulse repetition time (20μs), the radar system is first in the transmitting state, the SPDT RF switch is connected to the transmitting branch, and the two SPST RF switches are in the closed state. At this time, the two antenna arrays form a two-element antenna array to radiate a single-frequency sinusoidal signal into the air. The amplitude of the radiation signal is 1, the pulse duration is 1μs, and the signal-to-noise ratio of the transmitting system is 30dB. After the radar pulse transmission is completed, the SPDT RF switch is immediately connected to the receiving state to receive the echo signal of the target. Assume that in the direction of +25°, there is a target reflecting the radar signal 900m away from the radar, and its radar scattering area makes the amplitude of the single-frequency signal received by the radar system 0.2, and the signal-to-noise ratio of the receiving channel is 10dB. In the receiving state, two single-pole single-throw radio frequency switches control the radio frequency signals received on the two antenna arrays to enter the receiving branch in turn, and the cycle is 0.1μs (the corresponding modulation frequency is 10MHz).

The position of the target distance radar system can be obtained by comparing the time delay of the transmitted pulse and the echo signal. Assuming that the time delay of the received echo signal relative to the transmitted pulse is 6 μs, the distance of the target relative to the radar system is:

Perform fast Fourier transform on the echo signal, and the normalized power spectrum of the obtained echo signal is shown in Fig. 4 . It can be seen from the figure that the fundamental wave component is located at 30MHz, and its power is 0dB, and the first harmonic component is located at 40MHz, and its power is -6.1dB. The bearing of the target is calculated by the formula (1.2) as follows:

Specific example 2. Multi-target echo detection

For the radar system based on the two-unit time modulation array shown in Figure 1, the distance between the two antenna units is set to be 1.5m. The radar transmits a radar pulse signal with a carrier frequency of 100MHz and a width of 10μs. The pulse repetition time of the radar is 200μs. Suppose the distances are 6km, 9km, and 21km, and the directions are 5°, 40°, and 75° respectively, and there is a target echo. In a pulse repetition time, the radar signal transmitted and received by the radar system is shown in Figure 5. It can be seen from the figure that the durations of the three received echo signals are [40μs, 50μs], [60μs, 70μs] and [140μs, 150μs]. From the return time of the echo signal, the distances of the three targets can be estimated to be 6km, 9km and 21km respectively.

Figure 6 shows the time-frequency spectrum of the transmitted signal and the received signal within a pulse repetition time. It can be seen from the figure that during the time period [0μs, 10μs], the energy of the transmitted pulse is mainly concentrated at 100MHz. [40μs, 50μs], [60μs, 70μs] and [140μs, 150μs] are three target echo signals, and their energy is distributed to 100MHz (fundamental component) and 100MHz±k·10MHz (harmonic component) . Figure 7 shows a two-dimensional time-spectrum spectrum, the abscissa represents time, the ordinate represents frequency, and the grayscale of the color represents the energy intensity at the corresponding frequency within the corresponding time. It can be seen from the figure that when the target signal is in different directions, the energy distribution of the generated harmonic components is also different after being modulated by the SPST RF switch. Using the aforementioned method, the azimuths of the three target signals can be estimated to be 4.9°, 40.0° and 74.8° respectively.

This embodiment provides a radar system based on a two-unit time-modulated array. Aiming at the requirement of simultaneous tracking of multiple targets in a radar detection system, a two-unit time-modulated array is used to transmit and receive pulse signals, and through a specific signal processing method Estimate the position and orientation of multiple targets. The radar system proposed in this embodiment does not require mechanical scanning or electronic scanning, and is especially suitable for platforms such as missiles, unmanned vehicles, and drones that require miniaturization and lightweight guidance radars and anti-building radars.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (4)

1. A kind of 1. radar system based on two unit time-modulation arrays, it is characterised in that including：

   Aerial array (1), the aerial array (1) are two, are used to connect to spatial emission radar pulse signal and from space Receive target echo signal；

   Single-pole single-throw(SPST RF switch (2), the single-pole single-throw(SPST RF switch (2) be two, and respectively with two aerial arrays (1) Corresponding connection；When in emission state, two single-pole single-throw(SPST RF switches are in closure state, and radar pulse signal is presented Enter two aerial arrays (1) and to spatial emission；When in reception state, two single-pole single-throw(SPST RF switches are in modulating State, connects on two aerial arrays (1) target echo signal received in turn；

   Power splitter (3), is connected with two single-pole single-throw(SPST RF switches (2), and when in emission state, power splitter (3) will be treated Launch the energy in part of radar pulse signal into two parts, pass through the corresponding day of two single-pole single-throw(SPST RF switch (2) feed-ins respectively Linear array (1) is launched；When in reception state, power splitter receives the target echo letter that two aerial arrays (1) receive in turn Number and feed-in receiving branch；

   Single-pole double throw RF switch (4), is connected with power splitter (3), transmitting and reception shape for gated radar pulse signal State；

   Power amplifier (5), is connected to the receiving terminal of single-pole double throw RF switch (4), for amplifying radar pulse signal；

   Low-noise amplifier (6), is connected to the transmitting terminal of single-pole double throw RF switch (4), for docking received target echo Signal carries out low noise amplification；

   Frequency mixer (7), the frequency mixer (7) is two, and is connected respectively with power amplifier (5) and low-noise amplifier (6) Connect, for carrying out up-conversion and down coversion to transmitting and received signal；

   Local oscillator (8), is connected between two frequency mixers (7), for providing reference signal for frequency mixer (7)；

   Low-pass filter (9), the low-pass filter (9) they are two, and connection corresponding with two frequency mixers (7) respectively, wherein, Low-pass filter on transmitting branch is also connected with digital analog converter (10), for filtering out what is produced in digital analog converter (10) Harmonic component, the low-pass filter on receiving branch are used to filter out the high fdrequency component produced in down coversion；

   Digital analog converter (10), is connected with the low-pass filter on transmitting branch, for by the low-pass filtering on transmitting branch The digital medium-frequency signal that device produces is converted to analog if signal；

   Analog-digital converter (11), is connected with the low-pass filter on receiving branch, for by the low-pass filtering on receiving branch The analog if signal that device receives is converted to digital signal；

   Control and signal processing unit (12), for being controlled to single-pole single-throw switch (SPST) and single-pole double-throw switch (SPDT), producing radar Pulse signal, the spectrum signature of the docking collection of letters number are analyzed and estimate to receive the incident direction of signal.
2. 2. the radar system according to claim 1 based on two unit time-modulation arrays, it is characterised in that the control And signal processing unit (12) includes：

   Control module, for controlling the state of single-pole double-throw switch (SPDT) and carrying out state control and tune to two single-pole single-throw switch (SPST)s System；

   Signal emission module, for producing radar pulse signal；

   Signal processing module, the spectrum signature for docking the collection of letters number are analyzed, and estimate to receive the incident direction of signal.
3. 3. the radar system according to claim 1 or 2 based on two unit time-modulation arrays, it is characterised in that including Following parameter：

   T：The pulse-recurrence time of radar；

   τ：The pulse duration of radar；

   Δt：Target echo is relative to exomonental time delay；

   T_p：The modulation period of single-pole single-throw(SPST RF switch；Wherein, connected in preceding half period, receiving branch in two aerial arrays One of them, in second half of the cycle, receiving branch connects another in two aerial arrays.
4. 4. the radar system according to claim 3 based on two unit time-modulation arrays, it is characterised in that the signal The estimation for receiving signal incident direction is analyzed and docked to the spectrum signature of the processing module docking collection of letters number, is specially：

   By target echo distance R of the target relative to radar system can be calculated relative to exomonental time delay：

   <mrow> <mi>R</mi> <mo>=</mo> <mfrac> <mrow> <mi>c</mi> <mi>&amp;Delta;</mi> <mi>t</mi> </mrow> <mn>2</mn> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1.1</mn> <mo>)</mo> </mrow> </mrow>

   Wherein, c is the light velocity in vacuum；

   If exomonental carrier frequency is F_c, then target echo signal through single-pole single-throw(SPST RF switch carry out periodic modulation after, Generation carrier frequency is F_cFundametal compoment, and carrier frequency is F_c±kF_pHarmonic component, wherein, k is harmonic order number, F_pFor the switching frequency of RF switch；It is F that if RF local oscillator, which produces frequency,_oSimple signal, by frequency mixer and low-pass filter Afterwards, it is F comprising carrier frequency in reception signal_c-F_oFundametal compoment, and carrier frequency is F_c-F_o±kF_pHarmonic component； After Fourier transformation, it is α to calculate fundametal compoment₀, the first order harmonic components are α₁, then the incidence side of target echo signal To be relative to the normal direction deviation angle θ of two element antenna arrays：

   <mrow> <mi>&amp;theta;</mi> <mo>=</mo> <mi>a</mi> <mi>r</mi> <mi>c</mi> <mi>s</mi> <mi>i</mi> <mi>n</mi> <mrow> <mo>(</mo> <mfrac> <mn>2</mn> <mrow> <mi>K</mi> <mi>D</mi> </mrow> </mfrac> <mi>a</mi> <mi>r</mi> <mi>c</mi> <mi>t</mi> <mi>a</mi> <mi>n</mi> <mfrac> <mrow> <msub> <mi>&amp;pi;&amp;alpha;</mi> <mn>1</mn> </msub> </mrow> <mrow> <mn>2</mn> <msub> <mi>&amp;alpha;</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1.2</mn> <mo>)</mo> </mrow> </mrow>

   Wherein, D is the distance between two antenna elements, and K is corresponding to carrier frequency F_cWave number, i.e.,：

   <mrow> <mi>K</mi> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <msub> <mi>&amp;pi;F</mi> <mi>c</mi> </msub> </mrow> <mi>c</mi> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1.3</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow>