JP2582556B2 - MTI pulse radar device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an MTI radar device that detects only a moving target such as an aircraft.

(Prior Art) A conventional MTI radar device uses a circuit configuration as shown in FIG. That is, a high-frequency pulse signal output from the magnetron 1 is partially extracted from the transmission signal via the directional coupler 2 and mixed with the output of the stabilized local oscillator 7 by the mixer 1 of 6 to obtain the transmission signal. A phase pull-in signal having phase information is obtained. Using this signal, a coherent oscillator 10 creates a reference signal that is coherent to the transmission signal. The received signal from the antenna 4 passes through the circulator 3 and is mixed with the output of the stabilized local oscillator 7 by the mixer 2 of 8 and amplified by the IF amplifier 9 and then divided into two by the phase detector 1
Enter 1 and 12. The reference signal obtained by the coherent oscillator 10 is also bisected, one is input to the phase detector 11, and the other is shifted in phase by 90 ° by the 90 ° hybrid 13 and enters the phase detector 12, and the received signal is subjected to phase detection. Is done. Outputs of the phase detectors 11 and 12 are I (In-phase) channel video,
And Q (Quadrature) channel video, the reflected signal from the stationary object is eliminated by the erasure unit 14, and the MTI video 15 from which only the moving object is extracted is obtained.

(Problems to be solved by the invention) With this type of conventional MTI radar receiver, a coherent oscillator with sufficiently stable frequency cannot be obtained.
Shorter transmission pulse widths make coherent oscillation very difficult, and radars that require precision use amplifier-type transmitters and are very expensive.

(Means for Solving the Problems) An object of the present invention is to solve the above-mentioned drawbacks of the prior art, in which a highly stable oscillator is used as a reference signal source, and a transmission pulse and a reception pulse are used. Complex multiplication between the phase detection output of the transmission pulse and the phase detection output of the received signal to obtain the phase difference between the two, thereby obtaining a highly stable and accurate MTI pulse radar using a magnetron. It is to provide a device.

Embodiment An embodiment of the present invention shown in FIG. 1 will be described in detail below.

In the figure, 1 is a magnetron, 2 is a directional coupler, 3 is a circulator, 4 is an antenna, 5 is a modulator, 6 is a mixer that converts transmission pulses to an intermediate frequency, 1 is a stabilized local oscillator, and 8 is
Are mixers 2 and 9 for converting received pulses to an intermediate frequency, IF amplifiers 101, crystal oscillators 101, 102, 103, 11, 12 are phase detectors 1 to
4,13 are 90 ° hybrids that shift the signal phase by 90 °, 104 ~
107 is an AD converter 1-4, 108 is a complex multiplier, 14 is an erasure device, 15 is
MTI video output terminal.

A part of the transmission pulse from the magnetron 1 is taken out through the directional coupler 2 and mixed with the output of the stabilized local oscillator 7 in the mixer 1 and converted into an intermediate frequency. The received signal from the antenna 4 is transmitted to the circulator 3
, And is mixed with the output of the stabilized local oscillator 7 by the mixer 2 of 8, converted to an intermediate frequency, and sufficiently amplified by the IF amplifier 9. The transmission pulse and the reception signal converted to the intermediate frequency are bisected and enter the phase detectors indicated by 102, 103 and 11, 12, respectively. The reference signal using the crystal oscillator 101 is sufficiently stable and uses the same oscillation frequency as the intermediate frequency. The reference signal is bisected and the other is 90 ° hybrid 13 with phase 90
And is input to the phase detectors 103 and 12. After the transmission pulse is phase-detected, the signals AD-converted by the AD converters 1 and 2 at 104 and 105 are respectively I _t and Q _t , and the reception pulse is subjected to phase detection at A and 106 at 107.
The signals AD-converted by the D converters 3 and 4 are I _r and Q _r , and if they are considered to be complex signals, Z _r = I _r + JQ _r and Z _t = I _t + JQ _t . Note that I _t ,
For Q _t is only once transmitted pulse AD conversion for each transmission.

While coherence between the transmission pulses at a high frequency and the received pulse are taken, Z _r, Z _t the phase for each transmission is randomly to phase detection by the reference signal without phase alignment at an intermediate frequency. However, the angular difference of Z _r, and Z _t is
If _Zr is a received signal from a fixed object, it is constant. The received signal if the moving object is the frequency changes by the Doppler effect, the angle difference between the Z _r and Z _t varies with a period of Doppler. MT
I want information I radar is the angle difference between the Z _r and Z _t, it Z
a complex conjugate of _r and Z _t obtained by the product of the Z _r ^*. This means that, if ^{_{Z r = r 1 e JQ1,}} Z t = r 2 e JQ2 Z r Z t * = r 1 r 2 e
^{J (θ} ₁ ^-θ ₂₎ it can be seen that the angular difference between the next Z _r and Z _t are obtained. Transmit pulse amplitude Is usually constant, the output power fluctuation of the magnetron can be corrected division to Oke if magnetron output varies r ₂ ² be varied in amplitude.

I channel video and Q channel video obtained by the complex multiplier _{108, I = I r I t +} Q r Q t, Q = I t Q r -I r Q t , and the passed, canceller 14 uses this signal For example, an MTI video in which the reflection signal from the fixed object is eliminated and only the reflection signal from the moving object is detected is obtained.

In the above-described embodiment, the case where the magnetron is used as the high-frequency pulse oscillation source has been described.

(Effects of the Invention) As described above, a highly stable and highly accurate phase detection output can be obtained with a pulse radar using a magnetron. This eliminates the need for expensive amplifier-type transmitters, thus contributing to lower prices. It is also applied to fields that are widely used, such as marine radars. Processing can be performed.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention, and FIG. 2 is a block circuit diagram showing a conventional MTI pulse radar device. 1 ... magnetron, 2 ... directional coupler, 3 ... circulator, 4 ... antenna, 5 ... modulator, 6 ... mixer 1,7 ...
... stabilized local oscillator, 8 ... mixer 2,9 ... IF amplifier, 10 ...
… Coherent oscillators, 11-12 …… Phase detectors 1, 2, 13…
... 90 ° hybrid, 14 ... Eraser, 15 ... MTI video output, 101 ... Crystal oscillator, 102,103 ... Phase detector 3,4,104
... 107 AD converters 1-4,108 ... Complex multipliers.

Claims (1)

(57) [Claims] The present invention is characterized in that a reflected signal from an object is phase-detected by a coherent reference signal to a transmission pulse, a reflected signal from a fixed object is erased based on the extracted phase information, and only a reflected signal from a moving object is extracted. In the MTI pulse radar device, a highly stable oscillator that outputs a continuous signal that is not in phase with a transmission pulse to obtain a reference signal of a phase detector, and a quadrature of the transmission pulse using the output signal of the oscillator. A first quadrature phase detector for performing phase detection, a second quadrature phase detector for performing quadrature phase detection of the reflection signal, and a complex multiplier for performing complex multiplication of outputs of the respective phase detectors An MTI pulse radar apparatus, which extracts only phase information of a coherent reflected signal from the transmission pulse.