JPH0149905B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a pulsed Doppler radar using an active type phased array antenna, which controls ON/OFF and gain of a transmitter/receiver of an antenna element having a transmitting/receiving function and a phase shift function. In particular, the present invention aims to provide a phased array radar in which transmission power and antenna gain or antenna sideloop characteristics are optimized depending on the radar mode of the pulsed Doppler radar, thereby significantly improving radar detection range performance. It is something to do.

Conventional active phased array antennas use uniformly distributed apertures to transmit transmit signals from all antenna elements in order to maximize the transmit power or minimize the transmit power of each antenna element. It formed a surface. For this reason, the antenna gain is maximized, but the side rope level is also maximized, and in a circular aperture antenna, the first
The sidelobe level is -17.6dB. on the other hand,
In pulsed Doppler radar, the size of reflected waves from the ground surface or the like, that is, clutter, received from antenna side lobes poses a problem. In particular, in pulsed Doppler radar installed on aircraft, the frequency spectrum of sidelobe clutter received by antenna sidelobes that exist in a wide range of space is widely distributed on the frequency axis depending on the speed of the aircraft, so the frequency spectrum is the same. The reflected signal from an aircraft target approaching at low speed while traveling in the direction of
It will compete with Kuratsuta on the frequency axis. Therefore, in order to improve target detection range performance, it is necessary to reduce the antenna sidelobes, but if we try to take advantage of the most important feature of active phased arrays, they will not be optimally compatible with pulsed Doppler radar. . Therefore, in the past, the amplitude of the signal received by each antenna element was controlled during reception to form an amplitude taper distribution on the aperture surface in order to reduce side lobes. However, if the transmitting time is uniformly distributed, the antenna sidelobe level for transmitting and receiving cannot be reduced below a certain value even if the receiving sidelobe is lowered.

This invention was made to eliminate such drawbacks in conventional phased array radar, and by controlling the transmitter/receiver of the antenna element having transmitting and receiving functions on/off and gain control, The present invention aims to provide a phased array radar that can improve radar range performance by optimizing transmission power and antenna gain or antenna sidelobe characteristics according to the radar mode of the pulsed Doppler radar. The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an example of the configuration of a conventional phased array radar. Based on the radar transmission mode selected by the controller 1, a reference signal generator 2 generates a pulsed transmission reference signal, which is transmitted via a transmitter/receiver switcher 3. The signal is sent to active phased array antenna 4. The transmission signal from the active phased array antenna is radiated toward the target, reflected from the target, received by the active phased array antenna 4, and inputted again to the receiver 5 via the transmitter/receiver switch 3, where it is amplified. A signal processor 6 performs necessary processing as a video signal and the signal is displayed on an indicator 7. Furthermore, the output of the signal processor 6 is sent to the radar computer 8, which performs target signal tracking processing based on the target tracking command from the controller 1, and extracts accurate distance information, precise angle information, and speed information. The beam scanning angle command signal is displayed on the indicator 7 through the signal processor 6 in symbols and numbers, and the beam scanning angle command signal is sent to the antenna controller 9.
The signal is sent to the phase shift calculation circuit 10 in the antenna beam, and the antenna beam is controlled so that the target is always irradiated. Also, based on the radar operation command from the controller 1, the radar computer 8 sends an antenna pattern shaping command signal to the attenuation controller 11 in the antenna controller 9, and sends a side lobe at the time of reception of the active type phased array antenna 4. control to a low level. A power supply 12 supplies power to an antenna element 13 shown in FIG. 2 within the active phased array antenna 4, and a reference signal generator 2 supplies a transmission trigger. FIG. 2 is a diagram showing an example of the basic configuration of the antenna element 13 constituting the active type phased array antenna 4, in which the transmission reference signal from the reference signal generator 2 is received at the terminal 1T, and the phase is shifted. The phase of the signal is changed by a predetermined phase shift amount in the circulator 14, and after passing through the circulator 15, the signal is input to the transmitter 16. The transmitter 16 uses an amplification method using a transistor, or an injection-locked or phase-locked oscillation method using a diode oscillator. Alternatively, there is also a method that combines these with a multiplier. The signal amplified to high power by the transmitter 16 passes through the transmitter/receiver switch 17 and is radiated into space from the radiator 18. On the other hand, the signal reflected by the target is received by the radiator 18 again, passes through the transmitter/receiver switch 18 again, and is input to the receiver 19. The receiver usually uses an amplification method using transistors. The amplitude of the signal amplified by the receiver 19 is attenuated by a predetermined attenuation amount by an attenuator 20 and then passed to the circulator 15.
The signal is transmitted to the terminal 1T through the phase shifter 14, and is inputted from the transmitter/receiver switch 3 to the receiver 5 for signal processing as described in FIG. Phase shifter driver 21
is connected to a phase shift calculation circuit 10 in the antenna controller 9 through a terminal 2T. radar computer 8
Based on the beam scanning angle command from the phase shifter driver 21, the phase shift amount calculation circuit 10 calculates the phase shift amount of each antenna element, and sends predetermined phase shift amount data to the phase shifter driver 21 to drive it. Attenuator driver 22 is connected to attenuation controller 11 in antenna controller 9 through terminal 3T. When the radar computer 8 instructs the attenuation controller 11 to set the aperture distribution of the antenna in response to a mode command from the controller 1, the attenuation controller 11 sends attenuation data to the attenuator driver.
drive The transmitter/receiver driver 23 is connected to the reference signal generator 2 through a terminal 5T, and upon receiving a transmission trigger from the reference signal generator 2, transmits the transmitter 1.
6. Pulse drive the receiver 19 and transmit/receive switch 17. Terminal 4T is connected to power supply 12 and supplies power to the driver within antenna element 13.

In this way, in radars using conventional active phased array antennas, the aperture distribution of the antenna can only be changed during reception, and is kept uniform during transmission. The disadvantage is that it cannot be lowered to below 45 dB.

On the other hand, in pulsed Doppler radar for aircraft, the PRF is sufficient so that there is no uncertainty in the target speed.
A high PRF method with a high pulse repetition frequency (Pulse Repetition Frequency) is used, but as shown in Figure 3a, the antenna main beam 3
0 irradiates the target 134 and the ground 33, and the antenna side lobe 31 irradiates the ground 33, the frequency spectrum of the received signal is divided into the main beam clutter 36 and the side lobe clutter 37 as shown in FIG. 3b.
spreads on the frequency axis. The target 134 approaching in opposition is received at a frequency ( _p + _d ) higher than the transmission frequency _p by the Doppler frequency _d , so the sidelobe clutter 37 and the main beam clutter 36 are clearly separated on the frequency axis. Since it can be separated, if unnecessary clutter is removed, the oncoming approaching target signal 38
can only be detected. However, Figure 4a
The received signal 39 from the approaching target 235 traveling in the same direction as shown in FIG. 3 has a frequency between the main beam clutter frequency _MBC and the transmission frequency _p as shown in FIG. It is buried in the sidelobe clutter 37 that is accumulated and becomes a large level for each transmission PRF. Therefore, for tracking approaching targets, the side lobe clutter
In order to reduce the overlap of each PRF, the PRF is set to a low value and the main beam clutter 36
A medium PRF method is used in which the PRF is set high enough that the signals do not overlap on the frequency axis. Figure 4b is inside
This is a diagram showing the frequency spectrum of the received signal in the PRF mode, and the tracking approaching date signal 39 becomes larger than the side lobe clutter 37 and becomes detectable. If the sidelobe clutter 37 is further reduced, the detection probability of the tracking approaching target signal 39 will be greatly improved.

However, since conventional active phased array antennas always use a uniform distribution when transmitting, antenna side lobes cannot be reduced even in medium PRF mode, so the probability of detecting a tracked approaching target from within side lobe clutter is low. is low.

Therefore, the present invention provides a means for controlling ON/OFF of a transmitter with a built-in antenna element constituting an active type phased array antenna of a conventional phased array radar and controlling the gain of a receiver. Transmit power depending on mode,
Control of sidelobe levels and antenna gain can be implemented to optimize radar range performance.

FIG. 5 is a diagram showing an embodiment of the present invention, in which a transmitter controller 24 is installed in the antenna controller 9 of a conventional phased array radar, and a transmitter controller 24 is installed in the antenna element 13.
By installing the ON/OFF control driver 25, it becomes possible to easily change the performance of the antenna. When the high PRF mode is selected by the controller 1, the radar computer 8 instructs the transmitter controller 24 to operate the transmitters of all antenna elements. Transmitter in antenna element 13 through 6T
Turn on the ON/OFF control driver 25.

This allows transmission from all antenna elements, maximizing the transmission output, and at the same time achieving uniform distribution, resulting in maximum gain. Similarly, the attenuation controller 11 controls the attenuators 20 of all antenna elements.
By setting the attenuation amount to the minimum value, the maximum gain can be obtained even during reception. Therefore, the target detection distance performance of the radar is improved. If the antenna aperture distribution is made uniform, the sidelobe level will rise and the sidelobe clutter will also increase, but as shown in Figure 3, in the high PRF mode, the clutter and the approaching target can be separated on the frequency axis, so the sidelobe level will increase. There is no effect of the lobe level increase.

Next, when the medium PRF mode is selected by the controller 1, the radar computer 8 tells the transmitter controller 24 to turn each antenna element on and off so that the antenna aperture distribution becomes a density distribution that provides low sidelobes. OFF
command the control of The transmitter controller 24 includes a transmitter ON/OFF driver 25 within each antenna element.
Turn on or off. Furthermore, by controlling the attenuation amount of the attenuator 20 to obtain an amplitude taper distribution,
It is possible to significantly reduce antenna side lobes during transmission and reception, significantly reduce side lobe clutter as shown in FIG. 4, and improve the detection distance or detection probability of a tracked approaching target.

As described above, according to the present invention, by providing means for controlling ON/OFF of the transmitter with a built-in antenna element of an active type phased array radar and the gain of the receiver according to the radar mode, radar detection is possible. Distance performance can be improved.

[Brief explanation of drawings]

Figure 1 shows the configuration of a conventional phased array radar, Figure 2 shows the configuration of the antenna element, Figure 3 shows the characteristics of high PRF pulsed Doppler mode, and Figure 4 shows medium PRF. FIG. 5 is a diagram showing the characteristics of the pulsed Doppler mode, and is a diagram showing an embodiment based on the present invention, in which 1 is a controller, 2 is a reference signal generator, 3 is a transmission/reception switch, and 4 is an active type face switch. 5 is a receiver, 6 is a signal processor, 7 is an indicator, 8 is a radar computer, 9 is an antenna controller, 10 is a phase shift calculation circuit, 11 is an attenuation amount controller, 12 is a power supply, 13 is an antenna element, 14 is a phase shifter, 15 is a circulator, 16
is a transmitter, 17 is a transmitter/receiver switch, 18 is a radiator, 1
9 is a receiver, 20 is an attenuator, 21 is a phase shifter driver, 22 is an attenuator driver, 21 is a transceiver driver, 24 is a transmitter controller, 25 is a transmitter ON/
OFF control driver, 30 is the antenna main beam, 31 is the antenna side lobe, 33 is the ground,
34 is target 1, 35 is target 2, 36 is main beam clutter, 37 is side lobe clutter, 38
39 is an oncoming approaching target signal, 39 is a tracking approaching target signal,
1T to 6T are terminals, _p is the transmission frequency, _d is the Doppler frequency, _MBC is the main beam clutter frequency, and _r is the pulse repetition frequency. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. A transmitter, a receiver, an attenuator for attenuating the amplitude of the output signal of the receiver, and a phase shifter connected to the output side of the attenuator and the input side of the transmitter via a circulator. In a phased array radar that uses an active type phased array antenna consisting of a large number of antenna elements, there is a controller that generates command signals for radar modes such as high PRF mode and medium PRF mode, and a controller that generates command signals for the radar modes such as high PRF mode and medium PRF mode. A radar computer generates a beam scanning angle command signal, an antenna pattern shaping command signal, and a transmitter operation command signal in the antenna element based on the signals, and a beam scanning angle command signal from the radar computer calculates the amount of phase shift of each antenna element. a phase shift amount calculator that calculates the amount of phase shift and outputs the phase shift amount to each of the antenna elements, and an attenuation amount controller that controls the amount of attenuation of the attenuator in each of the antenna elements based on an antenna pattern shaping command signal from the radar computer. , a transmitter controller for turning on and off the transmitter in each of the antenna elements according to a transmitter operation command signal from the radar computer, and when the radar mode from the controller is a high PRF mode, The transmitters of all of the above antenna elements are turned ON and the attenuation of the above attenuator is controlled to the minimum value, and when the radar mode is medium PRF mode, the antenna aperture distribution has a low side lobe. an antenna controller that turns on or off a transmitter in each antenna element so as to have a density distribution, and also controls the amount of attenuation of the attenuator so that the antenna aperture distribution forms an amplitude taper distribution during reception; A phased array radar characterized by: