JPH03289578A - Radar equipment - Google Patents

Abstract

PURPOSE:To make the transmission angle of radio wave beam continuously variable and to magnify the search region of a target by combining the control of transmission pulse quantity due to a digital phase shifter and the variable control of transmission frequency and an antenna interval. CONSTITUTION:At first, the output voltage B of an oscillator control circuit 61 is changed so that a wavelength lambda gradually becomes large in the stat of phase difference deltai. By this method, a transmitting-receiving angle is increased from thetai to thetam. Next, phase difference is set to deltai+2 and the voltage B is outputted so that the wavelength lambda gradually becomes small in this phase state. When radio wave beam is repeated from phi1 to phin and, when the change quantity at every cycle Tr of the output voltage B of the oscillator control circuit 61 is made sufficiently little, the transmitting-receiving angle of radio wave beam can be continuously changed and the search region of a target in a radar appara tus can be widened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radar device, and particularly to a radar device suitable for detecting a target within a detection area at high speed and with high precision.

[Conventional technology]

As a radar device that detects targets within the detection area at high speed,
There is a phased array radar that uses an array antenna and a digital phase shifter. The configuration of this radar device is the 10th
As shown in the figure. The antenna elements 101 to Io are connected from the transmitter 6 via the transmission/reception switch 5, the distribution circuit 4, and the phase shifters 201 to 20n.
Pulse voltages P1 to Pn are supplied to each antenna element (hereinafter simply referred to as an antenna), and a radio wave beam is radiated into space from each antenna element (hereinafter simply referred to as an antenna). In this case, a pulse voltage P1 between two adjacent antennas, for example, antenna 101 and antenna 102
If the transmission phase difference δ between
A radio beam is sent in the direction.

δ= (27C/λ) d −5in f)
(1) Here, λ is the wavelength and d is the spacing between the array antennas. Therefore, by controlling the phase difference δ between adjacent antennas, the transmission and reception angle 0 of the radio wave beam can be varied in all directions. Therefore, conventionally, a configuration has been used in which the transmission phase difference δ is changed using a digital phase shifter.

This digital phase shifter prepares a delay circuit in which each of multiple delay lines is equipped with a switch that bypasses the delay line, connects each delay circuit in series, and changes the delay time by turning each switch on and off. In other words, the amount of phase shift can be varied.

[Problem to be solved by the invention]

In the conventional technology described above, the control amount of the transmission phase by the digital phase shifter is discrete. For this reason, the phase difference δ between adjacent antennas can only take discrete values, so if the wavelength λ and the antenna spacing d are constant, as is clear from equation (1), the transmission angle θi of the transmit beam (reception is also completely Same) is also the 11th
As shown in the figure, only discrete values can be taken. For example, if d=0.5λ and the digital phase shifter is 4 bits (
In the example (when four delay lines are used), the transmission and reception angles θ of the transmission beams are 22 degrees, 30 degrees, 39 degrees, etc.
and takes discrete values. Therefore, like the target 12 in FIG. 11, a discrete beam φ1. There was a problem that objects existing between φ2 could not be detected. To prevent this.

If the interval between the beam transmission and reception angles θi is made smaller, a large number of position changes will be required, creating a problem that the apparatus and its control will become complicated.

An object of the present invention is to provide a radar device that can finely change the transmission/reception angle of a transmission beam within a predetermined detection area and that can be easily controlled.

[Means to solve the problem]

The above objective is achieved by controlling the phase of the transmitted pulse voltage using a digital phase shifter, as well as variable control of one or both of the frequency of the transmitted pulse voltage and the spacing between adjacent antennas through selective use of antennas. be able to.

[For production]

The transmission/reception angle θ of the transmission beam in the phased array radar is expressed by the following equation (2) by transforming equation (1).

e = 5un-1(λδ/(2zd))”(2)
As is clear from this equation (2), by varying the wavelength λ, that is, the transmission frequency, the beam transmission/reception angle θ can be varied. Furthermore, the beam transmission/reception angle θ can be made variable by effectively changing the distance d between adjacent antennas by using, for example, every other antenna. By combining these methods, the beam transmission and reception angle can be controlled more precisely. In particular, the transmission frequency can be continuously controlled and the configuration can be simplified by using a voltage-controlled oscillator whose output frequency can be controlled by a control voltage.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a block diagram showing one embodiment of the present invention. The transmitter 6 includes a synchronization circuit 65, an oscillator control circuit 61, a voltage-controlled oscillator 62, a pulse oscillator 63, and a pulse modulator 64.
It outputs a pulse-modulated pulse voltage P. This pulse voltage P is transmitted through phase shifters 201 to 20n whose phase shift amount is adjusted by the control circuit 3, and transmission/reception switching devices 51 to 5n.
are supplied to the antennas 101-10n as pulse voltages P1-Pn having a predetermined phase.

On the other hand, the signal reflected from the target in space is sent to the antenna 1.
01 to Ion and become received signals R1 to Rn,
After being combined by a wideband adder 8 via transmission/reception switchers 51 to 5n and phase shifters 201 to 20n, the signals are inputted to a receiver 7 as a received signal R, where they are amplified and signal processed.

FIG. 2 is a time chart showing the operation of the apparatus shown in FIG. A synchronization signal A with a period Tr is output from the synchronization circuit 65 in the transmitter 6 and applied to the pulse oscillator 63 and the oscillator control circuit 61. The oscillator control circuit 61 receives the synchronization signal A
It generates a DC voltage whose value changes every time control signal B, that is, signal A, is inputted in synchronization with . The voltage controlled oscillator 62 oscillates a frequency modulation signal C having a frequency corresponding to the voltage of the control signal B. On the other hand, the pulse oscillator 63 generates a pulse signal synchronized with the synchronization signal A, and the pulse modulator 64 pulse-modulates (turns on and off) the frequency modulation signal C using the pulse signal to obtain a pulse voltage P.

In this way, the pulse voltage P becomes a signal whose frequency is varied every repetition period Tr.

The phase shifter control circuit 3 outputs the phase shifter control circuits 1 to 1 to 20n to the phase shifters 201 to 20n.
-20n is set with a phase shift amount determined by phase shifter control signals 1-In. Now, if this phase shift amount is set to a value that differs by δ between adjacent antennas, the pulse voltages P1 to Pn to each antenna will have a phase difference by δ, and from the antennas 101 to Ion, the phase difference will be different by δ. A radio beam is transmitted in a predetermined direction θ determined by δ. Furthermore, since the transmission frequency is variably set for each period Tr of the synchronization signal A, the transmission angle of the radio beam changes accordingly. The change in beam direction during reception is exactly the same as during transmission.

Next, the process of varying the radio beam transmission/reception angle according to the present invention will be explained using FIG. FIG. 3 shows antennas 101 to Io.
This shows the beam pattern obtained by combining the outputs of n, and assuming that the wavelength λ is constant, the phase difference is δi.

Radio wave beams φi and φi+1 are generated at positions of transmission and reception angles θi and Oi+1 with respect to δi+1. In this embodiment, in order to perform scanning by directing the radio beam during this period, first, the output voltage B of the oscillator control circuit 61 is changed so that the wavelength λ gradually increases (the frequency decreases) in a state where the phase difference δi is maintained. let This changes the transmitting and receiving angle from θi to 0.
Increase to m. Next, the phase difference is set to δi+1, and in this state, the voltage B is output so that the wavelength λ gradually becomes smaller. This reduces the transmission/reception angle of the radio wave beam φi+1 from θi+1 to 0 m. If this scanning is repeated from radio wave beams φ1 to φn, which are discretely present, and the amount of change per period Tr of the output voltage B of the oscillation control circuit 61 is made sufficiently small, the transmission/reception angle of the radio wave beams will be continuous from 0 to On. can be varied. For example, when the distance d between adjacent antennas is 0.5λ and the phase shifter is 4 bits, the radio beam transmission/reception angle Oi is 30 degrees and θi
When +1 is 39 degrees, in order to scan the radio beam up to θm=34.5 degrees, the wavelength, that is, the frequency, needs to be changed by about 10%.

Next, a modification of the radio beam scanning method will be described. The system shown in Figure 3 is a method in which the incident angle of one radio wave beam is varied up to the center position between adjacent radio wave beams, and the frequency of the other radio wave beam is similarly controlled so as to vary up to the center position. there were. Figures 4 and 5 are variations of this,
In order to scan between adjacent radio wave beams generated by a discrete phase shifter, there is a method of scanning while increasing the wavelength λ in the direction of increasing the radio wave transmission/reception angle (Figure 4), or a method of scanning in the direction of decreasing the transmission/reception angle. This is a method of scanning while decreasing the wavelength λ (FIG. 5). In this way, the transmission frequency can be controlled to be variable only in either the increasing or decreasing direction, which simplifies the control of the transmission frequency.

FIG. 6 is a block diagram showing the circuit configuration of a second embodiment of the present invention. The transmission/reception angle θ of the radio beam is determined by the wavelength λ, the phase δ, and the distance d between adjacent antennas, as shown in equation (2).
By selecting and operating every m Ions, control is also performed to vary the effective antenna spacing d, making it possible to more finely vary the transmission and reception angle of the radio wave beam. For this purpose, switches 301 to 30n for selecting antennas for transmission and reception and a switch control circuit 9 are added.

Next, the operation of this embodiment will be explained using the flowchart shown in FIG. First, the phase shifter control circuit 3 calculates the initial phase of each array element, and sets each initial phase to the phase shifters 201 to 20n. Further, the switch control circuit 9 calculates the antenna to be transmitted and received first, and the switches 301 to 30n are used to select that antenna (process 701). Next, under these conditions, pulse voltages P1 to Pn are supplied to the antenna,
Sends a radio beam in a predetermined direction. At this time, transmitter 6
The frequency of the pulse voltage P output from the repeating period T
By varying each r, the transmitting and receiving angle θ of the radio beam
(processing 702), then switch 3
01 to 30n to change the spacing d between transmitting and receiving antennas to continuously vary the transmitting and receiving angle θ of the radio wave beam. This operation is continued until the switching scan of the transmitting/receiving element interval is completed (processes 702 to 704). When this operation is completed, the phase difference δ is changed and the same operation as 1 or more is repeated for 0 or more. The operation is continued until the control of the phase difference δ is completed (processes 702 to 706). By performing such operations, the control for selecting the transmitting and receiving antenna, the control of the transmitting and receiving phase difference of the pulse voltage, and the transmission By combining variable frequency control, it becomes possible to finely vary the transmission and reception angle of the radio wave beam.

FIG. 8 is a block diagram showing a third embodiment of the present invention, in which the antenna is divided into transmitting and receiving antennas. The antennas 101 to Ion transmit a radio wave beam in a predetermined direction according to the amount of phase shift of the phase shifter, and continuously vary the transmission and reception angle of the radio wave beam by varying the transmission frequency. On the other hand, signals reflected from targets in space are received by adjacent antennas 111 to lln. Received signals R1 to Rn from antennas 111 to lln can receive reflected waves in a predetermined direction by passing through phase shifters 201 to 20n installed with the same amount of phase shift as that for transmission. The operation of the circuit other than this is the same as that of the first embodiment, so the explanation will be omitted.

If this embodiment is used, a transmitting/receiving switch for switching between transmitting and receiving is not required, and the circuit configuration can be simplified.

Next, a fourth embodiment of the present invention will be described. As mentioned earlier, the transmission/reception angle θ of the radio beam is expressed by equation (2), and the wavelength λ
, phase δ, and distance between adjacent antennas d. When the minimum phase control amount δwin is a constant value, the beam transmission and reception angle θ
In order to continuously scan the beam between adjacent beams when the angle is near 0 degrees, it is necessary to increase the range in which one frequency can be varied.

On the other hand, when the beam transmission/reception angle is around 90 degrees, the frequency variable range may be small. Therefore, when the beam transmission/reception angle θ is around 0 degrees, the frequency variable range can be made smaller by decreasing the minimum phase control amount δl1lin. is possible,
In this embodiment, the minimum phase control amount δwin can be changed by changing the number of bits of the phase shifter, and the block diagram thereof is shown in Fig. 9. This figure only shows a phase shifter with a variable bit number, and the other circuits are the same as in the first embodiment.

The phase amount control circuit 13 sends a control signal F1"Fn to the dual switches 41 to 4n via the switches 31 to 3n. The dual switches 41 to 4n send control signals F1 to Fn.
The combination of delay lines 71 to 7n to be used is switched according to n, and the amount of phase shift is determined. Up to this point, the operation is the same as the conventional one, but in this embodiment, the switches 31 to 3n are controlled by the control signals 81 to Sn from the bit number selection circuit 14, and the signals are actually applied to the dual switches 41 to 4n. For example, when the number of bits is 3, only the control signals F1 to Fn are selected so that only the delay lines 71 to 73 are used. The minimum phase control amount δll1in at this time is π/4. According to this embodiment, the minimum phase amount δwin is obtained by varying the number of bits of the phase shifter.
can be varied, making it possible to efficiently control the transmission and reception angle of radio wave beams.

〔Effect of the invention〕

According to the present invention, in a radar device composed of a digital phase shifter and an array antenna, radio waves can be This has the advantage that the beam transmission and reception angle can be varied almost continuously, and the target detection area of the radar device can be expanded.

[Brief explanation of drawings]

1 and 2 are block diagrams showing one embodiment of the present invention and time charts showing its operation, FIGS. 3 to 5 are explanatory diagrams of the transmission beam scanning method of the present invention, and FIGS. 7 is a block diagram and its operation flowchart of another embodiment of the present invention, and FIG. 8 is a block diagram of another embodiment of the present invention. FIG. 9 is a block diagram showing another embodiment of the present invention, and FIGS. 10 and 11 are explanatory diagrams of a conventional radar device. 101-10n, 111-1ln-antenna element, 2
01-20n... Digital phase shifter, 6... Transmitter, 62... Voltage controlled oscillator, 61... Oscillator control circuit, 64... Pulse modulator, 9゛°°°° Switch control 301 to 30n...Switch Figure 14...Bit number selection circuit 31 to 3n...Switch.

Claims (1)

[Claims] 1. An array antenna, a transmitter that generates a high-frequency signal, and an antenna that configures the array antenna by shifting the phase of the high-frequency signal generated by the transmitter so that a beam in a predetermined direction is formed. a digital phase shifter that shifts the phase of each high-frequency signal supplied to each of the antenna elements and received by the antenna element so that a beam in a predetermined direction is received; In the radar apparatus, the transmitter is configured to transmit its own transmitter so that a beam can be formed in a direction other than the beam direction of the array antenna, which can be set by the digital phase shifter. A radar device characterized in that it is configured to be able to change the frequency of a high-frequency signal generated by an aircraft. 2. A control circuit that outputs a signal instructing which antenna element of the array antenna to select, and applying the high frequency signal from the digital phase shifter only to the antenna element selected by the circuit, or controlling the above selection. 2. The radar apparatus according to claim 1, further comprising a switch circuit for controlling the antenna element to send only the high frequency signal received by the antenna element to the receiver. 3. The radar device according to claim 1 or 2, wherein each of the antenna elements constituting the array antenna is composed of adjacently arranged antenna elements for transmitting and receiving. 4. The minimum phase shift amount of the digital phase shifter can be variably set so that it becomes larger when the beam direction is parallel to the plane of the array antenna and smaller when the beam direction is perpendicular to the plane. The radar device according to claim 1, characterized in that: