Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1980-12-12
1983-07-19
Wilbur, Maynard R.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
343 177, G01S 1344
Patent
active
043946593
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a monopulse radar comprising a pilot signal generator for injecting phase- and amplitude-defined pilot signals into the separate receiving channels to obtain correction signals through the variation in the mutual phase and amplitude relationship between said receiving channels for correcting angle error signals derived from target return signals.
Such a monopulse radar is known from the U.S. Pat. No. 3,794,998; the monopulse radar described therein operates at a fixed transmitter frequency, which limits its effectiveness in the case of unfavorable operating conditions, such as with the receipt of jamming signals and multiple-trace echoes.
SUMMARY OF THE INVENTION
The present invention has for its object to provide a radar apparatus of the type set forth in the opening paragraph, in which radar the above limitation is obviated. According to the invention, the pilot signal generator and the transmitter in the monopulse radar are tunable, while a control circuit is incorporated for adapting the pilot signal generator relative to the frequency of the target returns.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described with reference to the accompanying figures, of which
FIG. 1 shows an embodiment of the radar according to the invention; and
FIGS. 2A-E illustrate a number of embodiments of the control circuit for adapting the pilot signal generator relative to the frequency of the target echoes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The radar of FIG. 1 is of the type based on the sum and difference method, permitting the tracking of a moving target in two coordinates and in range. The radar comprises a transmitter 1 and a receiver 2. A TR tube 3 passes transmitter pulses from transmitter 1 to the antenna system 4, where the transmitter pulses are emitted and the associated return signals are detected. As is customary with such a radar, the energy received from a target return is distributed by a comparator 5 to produce an elevation difference signal .DELTA.E, an azimuth difference signal .DELTA.B and a sum signal .epsilon.. These signals, containing amplitude and phase information which is a measure of the magnitude and direction of the target deviation with respect to the radar boresight axis, are used for the generation of error voltages for controlling the azimuth angle tracking unit (not shown in the figure) and the elevation angle tracking unit to track the target in azimuth and elevation. The .DELTA.B, .DELTA.E and .epsilon. signals are fed to receiver 2, in which they are processed in separate channels. Apart from the .epsilon. channel, FIG. 1 shows only the .DELTA.B channel, since the .DELTA.E channel is identical to the latter channel.
The .DELTA.B channel comprises in succession an RF protection element 6, a mixer 7, an IF amplifier 8, a phase detector 9, a boxcar detector 10, a doppler signal processing unit 11, and an error voltage generator 12. One of the functions of protection element 6 is to protect the .DELTA.B channel against reflections which are derived from the transmitter signal and are coupled in the .DELTA.B channel through comparator 5. Using a local oscillator 13, mixer 7 converts the RF signal .DELTA.B into an IF signal. This IF signal is detected in phase detector 9 by means of an IF oscillator or coherent oscillator (COHO) 14.
Since transmitter 1 consists of a pulsating RF oscillator and is therefore active only during the generation of a transmitter pulse, the phase of the signal derived therefrom is practically randomly distributed with respect to the output signal of local oscillator 13. To meet the consequences thereof, the radar comprises a control circuit of which various embodiments are shown in FIGS. 2A-E. This control circuit, including transmitter 1, local oscillator 13 and COHO 14, achieves a predetermined phase relationship between the transmitter pulse, the local oscillator signal and the COHO signal in each pulse repetition time. In this way the return signal of an ideal fixed target, tra
REFERENCES:
patent: 3718927 (1973-02-01), Howard et al.
patent: 3728723 (1973-04-01), Gellekink
patent: 3794998 (1974-02-01), Pearson, Jr. et al.
patent: 3883870 (1975-05-01), Kunz
patent: 3921173 (1975-11-01), Thomson
patent: 3950750 (1976-04-01), Churchill et al.
patent: 3977000 (1976-08-01), Wagner
patent: 4208632 (1980-06-01), Sheldon et al.
Hollandse Signaalapparaten B.V.
Kaiser K. R.
Kraus Robert J.
Wilbur Maynard R.
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