JPS6069578A - Monopulse receiver - Google Patents

Abstract

PURPOSE:To correct a phase error and to obtain accurately an azimuth angle error signal and an elevation angle error signal by amplifying a sum signal and a difference signal obtained as the output of a monopulse comparator through respective intermediate frequency amplifiers. CONSTITUTION:An input signal 1 from a target is received by a multi(four)-beam antenna 30 constituting a monopulse antenna to obtain antenna outputs 2, 3, 4, and 5 corresponding to the four beams, and they are inputted to a monopulse comparator 31 to obtain the sum signal 6, the 1st error signal 7 containing error information on an azimuth angle, and the 2nd difference signal 8 containing error information on an elevation angle. The 1st switch output 9 obtained by dividing the 1st difference signal 7 and the 2nd difference signal 8 by time is supplied to the 2nd mixer 34 to obtain the 2nd mixer output 13 by using a local oscillator output 25, and the output is amplified by the 2nd intermediate amplifier 36 to obtain the 2nd intermediate frequency amplifier output 13, which is inputted to a synchronous detector 37. A digital computing element 44 obtains the azimuth angle error signal 16 and elevation angle error signal 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of technology to which the present invention pertains The present invention relates to electromagnetic waves generated by moving targets such as aircraft, flying objects, or vehicles, or electromagnetic waves coming from these targets as a medium. This invention relates to the improvement of a monopulse receiver used in combination with a monopulse antenna, which is one of the means for detecting the error angle between the target and the antenna reference axis of a continuous wave or pulsed/plater tracking radar device for tracking a target. It is.

(2) Background of the present invention When tracking targets such as aircraft, flying objects, or vehicles using electromagnetic waves as a medium, it is possible to remove unnecessary clutter signals from fixed targets and efficiently receive Doppler-shifted signals from moving targets. Continuous wave or pulsed Doppler monopulse tracking radar devices are often used in place of conical scan tracking radar devices because of their much superior tracking performance. However, the monopulse antenna and monopulse receiver used in the monopulse tracking radar are very complex, and there are many problems that need to be solved, so various systems have been proposed.

Two types of intermediate frequency amplifiers, which are part of the monopulse receiver used in the pulsed Doppler tracking leg, are used depending on the purpose: wideband and narrowband amplifiers. In particular, the front end monopulse antenna,
The bandpass filter of the intermediate frequency amplifier, which is coupled immediately after the mixer following the monopulse comparator of the amplitude comparison type, can be constructed using a high frequency element such as a crystal filter, e.g.
A monopulse reception device whose band width has been narrowed to a certain extent is called an inverse receiver, and it is attracting attention as the most effective means of removing cranks, which are unnecessary reflected waves from fixed targets such as the ground and sea surface.

1] In order to extract the azimuth angle error signal and the elevation angle error signal of the target, it is necessary to perform synchronous detection of the difference signal using the sum signal that is the output of the monopulse comparator.

To achieve this, it is necessary to align the phase characteristics of the narrowband crystal filters used in combination, but this has been technically quite difficult, difficult to mass-produce, and economically expensive.

(3) Conventional technology and its general problems A conventional example of monopulse reception + 0 will be explained using a PtSi diagram. Four multi-beam antennas 301 forming a monopulse antenna Human power signal 1 from the iron target
is received, antenna outputs 2 , t 3 , 4 , 5 corresponding to the four multibeams are obtained and inputted to a monopulse comparator 31 , and the output of this comparator 31 is a sum signal 6 and an azimuth error. A first difference signal 7 containing information and a difference signal 8 containing height angle error information are obtained.

The sum signal 6 becomes the first mixed output 1o by the first mixer 33 using the output 25 of the local oscillator 41, is amplified by the first intermediate frequency amplifier 35, and becomes the @1 intermediate frequency amplifier output 1.
2, which becomes the reference signal for the synchronous detector 37.

On the other hand, the first difference signal 7 and the second difference signal 8 are the first switch signal 18 which is the output signal of the first switch signal generator 40.
By driving the first switch 32, the first switch 32 is alternately switched, resulting in the first switch output 9. The first switch output 9, which is a signal obtained by time-sharing the first difference signal 7 and the second difference signal 8, is converted into the second mixer output 11 by the vJ2 mixer 34 using the local oscillator output 25, and the second Intermediate frequency amplifier 3
6 and becomes the second intermediate frequency amplifier output 13, which becomes the input signal of the synchronous detector 37. The synchronous detector output 14 becomes an input signal of a low-pass filter 38, and high frequency components are removed to obtain a low-pass filter output 15.

The m2 switch 39 is set to tj by the ml switch 43 No. 18.
Since the switching is performed in synchronization with the S1 switch 32, the azimuth error signal 16 and the elevation angle error signal 17 can be obtained from the low-pass filter output 15. That is, by switching the first switch 32 and the second switch 39 synchronously using the first switch signal 18, which is the output signal from the first switch signal generator 40, the first difference signal 7 and the first difference signal 7 can be connected without crosstalk. It is possible to match the azimuth angle error signal 16 and the f:tS2 difference signal 8 with the elevation angle error signal 17 by degrees.

+11 signal 6 is expressed as follows.

X6=CO8ωt...(1) The first difference signal 7 in the azimuthal direction is expressed as follows.

X7 = da cosωL (2) The second difference signal 8 in the elevation angle direction is expressed as follows.

X, = de cosωt - (3) Sum signal 6 and difference signal 7. ε is intermediate frequency amplifier 35°36
After amplification, an azimuth angle error signal 16 and an elevation angle error signal 17 are obtained by a synchronous detector 37.

The azimuth error signal 16 is expressed as AZ=“aCO8ωt−CO5ωt=da...(4
) However, - is the average of one cycle. Height angle error signal 17
Similarly to equation (4), El = ecosωt−cosωt=de −(5)
Therefore, if the phase relationship between the three signals of the sum and difference of the monopulse comparator 31 is maintained as it is even after passing through the intermediate frequency amplifiers 35 and 36, and synchronous detection is performed, equations (4) and (5) can be obtained.
The following relationship holds true and there is no problem; however, in reality, it is not easy to align the phases of the intermediate frequency amplifiers 35 and 36 corresponding to the sum and difference signals.

(4) Specific problems with the conventional technology The input signal from the antenna varies depending on the modulation format of the electromagnetic waves used, but in Dobra Rage, which tracks moving targets, a wide frequency spectrum is used, and signals from large aircraft to small Since it is necessary to track the flying object and the difference between the input signal and the signal is large, the Monopa receiver Shiniso matches the center frequency of the carrier with the center of the intermediate frequency amplifier, and uses the human input signal of the synchronous detector 37. Second intermediate frequency amplifier output 1
It is necessary to keep the amplitude of 3 constant, and various additional circuits are required for this purpose, making it increasingly difficult to align the phases of the sum and difference signals. If there is a phase error θ between the sum and difference signals, the synchronous detector output 14 will be as follows.

A z = 2 da cos(ωt+θ) ” co
sωt= da cosθ ・(6) There are few problems when the phase error θ is close to zero, but if π is pi, if the phase error θ exceeds π/2 radians, the sign is reversed and it can no longer be used as a tracking device. will lose its function. It is also difficult to know and correct the phase error θ from equation (6).

(5) Purpose of the present invention The present invention provides that, as a result of amplifying the sum signal and the difference signal obtained as the output of the monopulse comparator using respective intermediate frequency amplifiers, the difference between the sum signal and the difference signal on the output side of the differential frequency amplifier is Even if there is a phase error, a monopulse receiver is provided that can correct the phase error from a signal obtained by synchronously detecting a difference signal using a sum signal and obtain an accurate azimuth error signal and elevation angle error signal. The purpose is to provide.

(6) Main points of the configuration of the present invention Before explaining the embodiment shown in FIG. 2 in detail, the present invention will be explained in detail using the time chart shown in FIG. 3.

As shown in FIG. 3, the second switch signal 19 having a timing synchronized with the fourth switch signal 21 causes the sum signal 6 to
is modulated via the phase modulator 42, the following time-divided phase modulator output 22 (X22) with a π/2 radian phase difference is obtained.

Then, an output 12 obtained by frequency converting this output 22 becomes a reference signal for the synchronous detector 37.

Since the first switch output 9 (X9) is similarly time-divided by the third switch signal 20 synchronized with the fourth switch signal 21, the following equation is obtained. This output 9 is frequency-converted and becomes an output 13, which becomes an input signal of the synchronous detector 37.

If the respective intermediate frequency amplifiers 35 and 36 have a phase difference of θ radian from each other, the low-pass filter output 15 (X1s) obtained by smoothing the synchronous detector output 14 becomes a time series signal as shown below. .

Since the low-pass filter output 15 in equation (9) is taken in by the digital calculator 44 at the timing of the Pt54 switch signal 21, the phase error θ can be calculated from the following relationship.

d+ cosθ Azimuth angle error signal 16 (Az) and elevation angle error signal 17 (
E#) is accurately calculated by correcting the phase error θ from...(11)...(12). Note that θ in FIG. 3 is 0.2 radian.

(7) Embodiment of the present invention FIG. 2, which is an embodiment of the present invention, will be described in more detail.

The four multi-beam antennas 30 constituting the monopulse antenna receive the human signal 1 from the target, and output antenna outputs 2, 3, and 3, respectively corresponding to the four multi-beams.
4.5 is input to the monopulse comparator 31 to obtain a sum signal 6, a first difference signal 7 containing azimuth angle error information, and a second difference signal 8 containing elevation angle error information.

The sum signal 6 is generated by a second switch signal 19 generated by a second switch signal generator 43 using a phase modulator 42.
The phase modulator output 22 is a time-divided phase modulated signal with a phase difference of π/2 radians, and the first mixer 33
Therefore, the output 25 of the local oscillator 41 is used to become the ptSi mixer output 1o.

This output 10 is amplified by the first open frequency amplifier 35 and becomes the first open frequency amplifier output 12, which becomes a reference signal for the synchronous detector 37.

On the other hand, the first difference signal 7 and the second difference signal 8 are changed to the first difference signal 7 and the second difference signal 8 by driving the first switch 32 by the third switch signal 20 and switching to the first difference signal 7 and the second difference signal 8 alternately. 1 switch output 9. First difference signal 7 and second difference signal 8
The first switch output 9, which is a time-division signal of This becomes the frequency amplifier output 13 and becomes the input signal of the synchronous detector 37. High frequency components are removed from the synchronous detector output 14 by a low-pass filter 38, resulting in a low-pass filter output 15. The digital arithmetic unit 44 uses the formula (10
), (11), and (12) to obtain an azimuth angle error signal 16 and an elevation angle error signal 17. The second switch signal generator 43 is a second switch signal generator for driving the phase modulator 42.
The switch signal 19, the third switch signal 20 for driving the first switch 32, and the signal of the low-pass filter output 15 of equation (9) are transferred to the digital arithmetic unit 44 without crosstalk.
A fourth switch signal 21, which is a timing pulse necessary for taking in the signals, is generated respectively.

(8) Supplementary explanation of the embodiment (a) So far, we have described a two-channel monopulse receiver with two intermediate frequency amplifiers, but an intermediate frequency amplifier with intermediate frequency amplifiers each corresponding to the difference signal 7.8 has been described. It is also possible to use three 3-channel mode/pulse receiving channels, or if you remove the first switch and change the analog input of the digital calculator to 2 channels, you can obtain the azimuth error signal 16 and the elevation angle error signal 17, so it is even more convenient. This is possible if high sensitivity is required.

(b) In the explanations so far, the sum signal is phase modulated, but the difference signal can also be phase modulated using equations (10), (11), (12).
), the azimuth angle error signal and the elevation angle error signal can be determined.

(1) The phase modulator 42 and the first switch 32 are connected to the mixer 33
Although the phase modulator 42 and the first switch 32 are connected before the mixers 33 and 34, the phase modulator 42 and the first switch 32 may be connected after the mixers 33 and 34.

(9) Effects of the present invention (a) Even if a phase error occurs between the two intermediate frequency amplifiers due to large fluctuations in the amplitude of the input signal or fluctuations in the frequency of the input signal, the influence of the error can be canceled and the Correct azimuth error signals and elevation angle error signals can be obtained.

(b) For amplifiers that use very high Q elements such as crystals in the bandpass filter of intermediate frequency amplifiers, select two paired crystals with well-matched characteristics, and then select an amplifier with similarly well-matched characteristics. is technically extremely difficult. Although the device of the present invention has a large number of phase modulators and digital arithmetic units 44, it is still economically advantageous compared to the difficulty of manufacturing two intermediate frequency amplifiers with uniform characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example of a monopulse receiver.
FIG. 2 is a block diagram showing an embodiment of a monopulse receiver according to the present invention, and FIG. 3 is a time chart for explaining the embodiment of FIG. 2. 1... Input signal, 2, 3, 4, -5... Antenna output, 6... Sum signal, 7... First difference signal, Death...
2nd difference signal, 9...1st switch output, 10...1st
Mixer output, 11... Second mixer output, 12... First intermediate frequency amplifier output, 13... Second intermediate frequency amplifier output, 14... Synchronous detector output, 15... Low-pass filter output collar 16... Azimuth error signal, 17...
Height angle error No. 411, 18...1st switch signal, 1
9... Second switch signal, 20... Third switch signal, 21... Fourth switch signal, 22... Phase modulator output, 25... Local oscillator output, 30... Antenna, 31... Monopulse comparator, 32... First switch, 33... First mixer, 34... Second mixer, 3
5... First intermediate frequency amplifier, 36... Second intermediate frequency amplifier, 37... Synchronous detector, 38... Low pass filter, 39... Second switch, 40... ...first switch signal generator, 41...local oscillator, 42...phase modulator, 43...second switch signal generator, 44...
Digital arithmetic unit. Patent applicant Director of Technology Research Headquarters, Defense Agency Yukie Omori Agent Patent attorney Takashi Murai

Claims (2)

[Claims] (1) At a monopulse antenna and a monopulse receiver having a Lux comparator, the sum signal of the monopulse antenna, which is one of the outputs of the Lux comparator, is used as a switching signal. 1, the phase modulator alternately phase-modulates the time series signals with a phase difference of π/2 radians to serve as a reference signal for the synchronous detector, while the difference signal that is the output of the monopulse comparator is used as the reference signal. The respective signals obtained in synchronization with the switching signal when synchronously detected by the synchronous detector using A monopulse receiver (tl) characterized in that the phase error between the sum signal and the difference signal is corrected to obtain an azimuth error signal and an elevation angle error signal.
tfi. (2) In a monopulse receiver having a monopulse antenna and a monopulse comparator, the difference signal of the monopulse antenna, which is the output of the monopulse comparator, is alternately π/ A time series signal having a phase difference of 2 radians is phase-modulated, and the sum signal output from the monopulse comparator is used as a reference signal for a synchronous detector, and when the phase-modulated signal is synchronously detected, it becomes the switching signal. Each signal obtained in synchronization,
In synchronization with the switching signal, the signal is digitized by a digital calculator, the arc tangent is calculated to determine the phase difference, and the phase error between the sum signal and the difference signal is corrected to produce an azimuth error signal and an elevation angle error. A monopulse receiver (Di.