TW202043799A - High-resolution spatial angle scanning radar system and design method thereof wherein mutual coupling effect of signals on all the antenna units is lowered by increasing the distance between the adjacent antenna units - Google Patents

Abstract

This invention relates to a high-resolution spatial angle scanning radar system and a design method thereof. The high-resolution spatial angle scanning radar system includes a plurality of antenna units, a corresponding phase shifter is disposed on a signal transmission path of each of the antenna units, and the plurality of the phase shifters is coupled with a wave mixer, wherein a distance d is formed between every two adjacent antenna units, and the distance d is greater than 1/2 of a wavelength [lambda] of a wireless signal. According to this invention, the mutual coupling effect of signals on all the antenna units is lowered by increasing the distance between the adjacent antenna units.

Description

High resolution spatial angle scanning radar system and its design method

The present invention relates to a phased array radar (Phased Array Radar), in particular to a high-resolution spatial angle scanning radar that can reduce the effect of mutual coupling.

The beam direction of traditional radar is fixed (for example, Doppler radar), which depends on the installation position of the radar. If the scanning direction needs to be adjusted, the direction of the beam must be changed by rotating the positioning of the radar through a mechanical device.

As shown in Fig. 5A, different from the above-mentioned conventional radar, a phase shifter Y is used in a phased array radar, and a phase shifter is added to the signal transmission path of each antenna unit 51 52. This changes the direction of the overall beam receiving and sending, as shown in Figure 5B. In this way, it is only necessary to change the signal phase of each antenna unit 51 to control the transmission and reception direction of the overall beam.

In order to suppress the generation of grating lobes in traditional phased array radar, when designing the relative position of the antenna unit 51, the distance L between two adjacent antenna units 51 is deliberately controlled to be less than half of the transmission. The signal wavelength λ, that is, L<1/2λ. That is to reduce the distance between adjacent antenna elements to be more closely arranged. However, this will cause a mutual coupling problem as shown in FIG. 6, and the signals on adjacent antenna elements 51 will be coupled with each other. Cause unnecessary interference.

The main purpose of the present invention is to provide a "high resolution spatial angle scanning radar" to avoid the mutual coupling problem existing in the existing phased array radar.

In order to achieve the foregoing objective, the high-resolution spatial angle scanning radar of the present invention includes: a plurality of antenna units, a corresponding phase shifter is arranged on the signal transmission path of each antenna unit, and the plurality of phase shifters are combined with a hybrid The wave device is coupled, wherein a distance d is maintained between two adjacent antenna units, and the distance d is greater than one-half of the wavelength λ of the wireless signal.

When applied to receiving signals, the radar system of the present invention can shorten the scanning time and improve the receiving resolution; when applied to transmitting signals, the phase difference of a relatively large angle can be adjusted, and the control signal beam produces a small angle change in space , The phase shifter is easier to design and manufacture.

Please refer to FIG. 1, which is a schematic diagram of the structure of the radar system of the present invention. The structure of the radar system 100 is an active phased array antenna, which can be used as a signal transmitting or signal receiving system. In this embodiment, multiple antennas are included. Units 11a-11d, a plurality of phase shifters 12 (phase shifters) and at least one mixer 13, the following description takes the first antenna unit 11a to the fourth antenna unit 11d as an example, but the number of antenna units is not limit.

Each antenna unit 11a-11d is an element that transmits or receives a signal. A corresponding phase shifter 12 is provided on the signal transmission path of each antenna unit 11a-11d, the plurality of phase shifters 12 and the mixer 13 Coupling. Taking the transmitting system as an example, the main signal is coupled to each phase shifter 12 through the mixer 13, and then radiated out through each antenna unit 11a~11d; when the parameters of the phase shifter 12 are changed, each antenna unit 11a~11d The signal above has an appropriate phase, so that the signals between adjacent antenna elements 11a-11d have a shape difference ψ, and the required beam can be generated.

In the present invention, in order to reduce the mutual coupling effect between the antenna units 11a-11d, the linear relative distance L between two adjacent antenna units 11a-11d is equal and the distance is greater than the transmission signal wavelength One half of (λ), that is, L>1/2λ. That is, the relative distance L between the first antenna unit 11a and the second antenna unit 11b is greater than one-half of the transmission signal wavelength (λ), and the relative distance between the second antenna unit 11b and the third antenna unit 11c L is also greater than half of the transmitted signal wavelength (λ)

Please refer to FIGS. 2A to 2C. In the following, four dipole antenna elements (Dipole) are used to simulate the first antenna element 11a to the fourth antenna element 11d. Assuming that the transmission signal (operating frequency) is 3GHz, the wavelength is λ=100mm, and the distance L between two adjacent antenna elements 11a~11d is set to 0.9 times the wavelength λ (L=0.9λ=90mm). When changing the adjacent The phase difference (ψ) between the antenna elements 11a-11d can change the angle (θ) of the beam. The relationship between the phase difference and the angle is as follows:

Taking the beam of Figure 2A as an example, in order to generate a 15-degree beam (θ=15 degrees), according to the above formula, the required phase difference ψ between adjacent antenna elements 11a~11d can be calculated to be about 83.8 degrees (0.47 π), therefore, when designing the antenna, the phase of the first antenna element 11a is taken as the reference point (zero degree), and the phase difference between the second antenna element 11b and the first antenna element 11a is controlled by the phase shifter 12 The phase difference between the third antenna element 11c and the first antenna element 11a is controlled to be approximately 167.6 degrees, and the phase difference between the fourth antenna element 11d and the first antenna element 11a is controlled to be approximately At 251.4 degrees, a beam as shown in FIG. 2A can be generated, where the angle of the main beam B1 is about 15 degrees.

Taking the beam of Figure 2B as an example, in order to generate a 30-degree beam (θ=30 degrees), according to the above formula, the required phase difference ψ between adjacent antenna elements 11a~11d can be calculated to be about 162 degrees (0.9 π), therefore, when designing the antenna, taking the phase of the first antenna element 11a as the reference point (zero degree), the phase difference of the second antenna element 11b relative to the first antenna element 11a is about 162 degrees, and the third The phase difference between the antenna unit 11c and the first antenna unit 11a is 324 degrees, and so on, so that a beam as shown in FIG. 2B can be generated, wherein the angle of the main beam B1 is about 30 degrees. Among them, the extension axis of the dipole antenna is shown by arrow A, because the dipole antenna is placed in the space for simulation in Figs. 2A~2C, so the complete beam of the dipole antenna can be seen completely.

Taking the beam of Figure 2C as an example, in order to generate a 30-degree beam (θ=45 degrees), according to the above formula, the required phase difference ψ between adjacent antenna elements 11a~11d can be calculated to be about 229.1 degrees (1.27 π), therefore, when designing the antenna, taking the phase of the first antenna element 11a as a reference point (zero degree), the phase difference between the second antenna element 11b and the first antenna element 11a is about 229.1 degrees, and the third The phase difference between the antenna unit 11c and the first antenna unit 11a is 458.2 degrees, and so on, so that a beam as shown in FIG. 2C can be generated, wherein the angle of the main beam B1 is about 45 degrees.

The above FIGS. 2A to 2C prove that the angle of the beam can be changed by adjusting the phase difference ψ between the adjacent antenna elements 11a to 11d. On the other hand, when the relative distance L between adjacent antenna units 11a-11d is changed, the number of beams is adjusted, which is equivalent to changing the geometric shape of the beams.

Please refer to FIGS. 3A to 3C to further simulate the first antenna 11a to the fourth antenna 11d with 4 patch antennas. Assuming that the frequency (operating frequency) of the transmission signal is 2.45 GHz, the wavelength is λ=122.5mm, and the distance L between two adjacent antennas 11a-11d is set to 0.9 times the wavelength λ (d=0.9λ=110mm).

Taking the beam of Figure 3A as an example, in order to generate a 15-degree beam (θ=15 degrees), the phase difference ψ required between adjacent antennas 11a-11d is about 83.8 degrees (0.47π). Therefore, when designing the antenna When taking the phase of the first antenna 11a as a reference point (zero degrees), the phase difference between the second antenna 11b and the first antenna 11a is about 83.8 degrees, and the phase difference between the third antenna 11c and the first antenna 11a is about 83.8 degrees. The difference is 167.6 degrees, and the phase difference between the fourth antenna 11d and the first antenna 11a is 251.4 degrees, which can generate a beam as shown in FIG. 3A, where the angle of the main beam B1 is about 15 degrees.

Taking the beam of Figure 3B as an example, in order to generate a 30-degree beam (θ=30 degrees), the phase difference ψ required between adjacent antennas 11a-11d is about 162 degrees (0.9π). Therefore, when designing the antenna When taking the phase of the first antenna 11a as a reference point (zero degrees), the phase difference between the second antenna 11b and the first antenna 11a is about 162 degrees, and the phase difference between the third antenna 11c and the first antenna 11a is about 162 degrees. The difference is 324 degrees, and so on, so that a beam as shown in FIG. 3B can be generated, where the angle of the main beam B1 is about 30 degrees, and the other beam B2 has an angle with the main beam B1.

Take the beam of Figure 3C as an example. In order to generate a 30-degree beam (θ=45 degrees), the phase difference ψ required between adjacent antennas 11a-11d is about 229.1 degrees (1.27π). Therefore, when designing the antenna When taking the phase of the first antenna 11a as a reference point (zero degrees), the phase difference between the second antenna 11b and the first antenna 11a is about 229.1 degrees, and the phase difference between the third antenna 11c and the first antenna 11a is about 229.1 degrees. The difference is 458.2 degrees, and so on, so that a beam as shown in FIG. 3C can be generated, where the angle of the main beam B1 is about 45 degrees.

，可能方向角的數量(m)為4。After the present invention increases the distance d between two adjacent antenna units 11a-11d, although the mathematical ambiguity of the antenna array response (array response) will cause the signal beam to be in addition to the main beam B1, Generate other side beams B2, but using the announcement No. I616064 owned by the applicant "A high-precision analytical method for calculating the direction of arrival using the phase of arrival and time difference of the wave" technology, the direction angle of the main beam can be calculated . When the distance L between the antenna elements 11a~11d is shown in the following table, the number of possible direction angles (m) will increase as the distance L increases; for example, when the distance between the antenna elements 11a~11d When the distance L is three-half of the signal wavelength

, The number of possible direction angles (m) is 4.

condition

的數量(m)Possible direction angle estimate

Number (m)

m=2

m=3

m=4

m=5

m=6

m=7

m=8

As shown in the example shown in Fig. 4A, when the present invention is actually applied, because it can generate complex beams and as long as the phase difference ψ and the adjacent distance L between adjacent antenna elements are set, the geometric shape of the beam can be determined. When scanning the plane, only a small angle of deflection is needed to detect the azimuth of the source signal. For example, the present invention is applied to the received signal as an example, assuming that the half-wavelength is 0.624mm, and the distance between the two antenna elements L= 0.762mm, which is slightly larger than half the wavelength, the two beams B1 and B2 generated by the radar system are shown in Figures 4A and 4B. Because the angles of the two beams B1 and B2 in space change synchronously, the scanning range of the two beams is also synchronous Change, if the scanning space is viewed from a plane of -90 degrees to 90 degrees, scanning the entire plane only needs to change the beam angle as shown in Figures 4A and 4B to complete the full range of scanning (as shown in Figure 4C). Compared with the traditional single beam scanning gradually from -90 degrees to +90 degrees, the present invention actually controls the beam movement in a smaller range, which can effectively shorten the scanning time.

In addition, when the phase angle (DOA) of the signal changes by 1 degree, the received phase angle changes by more than 1 degree (about 3 degrees in this example), so the received resolution can be improved. Similarly, when the radar system of the present invention is applied to transmit signals, as long as the phase difference is adjusted to about 3 degrees, the angle of the signal beam can be changed to about 1 degree in space, so the phase shifter 12 is easier to design.

11a~11d: antenna unit 12: Phase shifter 13: Mixer 51: Antenna unit 52: Phase shifter

Figure 1: Schematic diagram of the architecture of the present invention.

2A~2C: In the present invention, a dipole antenna is taken as an example, and beams of different angles are obtained by adjusting different phase differences.

3A to 3C: In the present invention, a patch antenna is used as an example, and beams of different angles are obtained by adjusting different phase differences.

Figures 4A-4C: schematic diagrams of the array radar of the present invention changing the scanning beam orientation.

Figure 5A: A schematic diagram of a traditional phased array radar (Phased Array Radar).

Figure 5B: Schematic diagram of beam directivity of phased array radar.

Figure 6: Schematic diagram of the mutual coupling effect of phased array radar.

11a~11d: antenna unit

12: Phase shifter

13: Mixer

Claims (8)

A high-resolution spatial angle scanning radar system, comprising: a plurality of antenna units, a corresponding phase shifter is arranged on the signal transmission path of each antenna unit, and the plurality of phase shifters are coupled to a mixer, wherein : The wavelength of the wireless signal transmitted by each antenna unit is λ, and a distance d is maintained between two adjacent antenna units, and the distance d is greater than one-half of the wavelength λ of the wireless signal; among them, any two adjacent antenna units The wireless signal between the two has a phase difference ψ, so that the angle θ of the beam generated by the scanning radar system and the phase difference ψ conform to a relationship:

. The high-resolution spatial angle scanning radar system according to claim 1, wherein the number of beams is changed by adjusting the distance d between two adjacent antenna elements. The high-resolution spatial angle scanning radar system according to claim 1, wherein the angle of the beam is changed by adjusting the phase difference between two adjacent antenna elements. The high-resolution spatial angle scanning radar system according to claim 1, wherein the distance between two adjacent antenna units is equal. A design method for a high-resolution spatial angle scanning radar system. The system includes a plurality of antenna elements, each antenna element transmitting wireless signals, wherein the design method includes: arranging the plurality of antenna elements at equal intervals to make two adjacent antenna elements Maintain a distance d between them, and the distance d is greater than one-half of the wavelength λ of the wireless signal; configure the wireless signal between any two adjacent antenna units to produce a phase difference ψ, so that the angle of the beam generated by the scanning radar system θ and the phase difference ψ conform to the following formula:

. The design method of the high-resolution spatial angle scanning radar system described in claim 5, wherein the number of beams is changed by adjusting the distance d between two adjacent antenna units. The design method of the high-resolution spatial angle scanning radar system according to claim 5, wherein the angle of the beam is changed by adjusting the phase difference between two adjacent antenna units. The design method of a high-resolution spatial angle scanning radar system as described in claim 5, wherein the distance between two adjacent antenna units is equal.

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