MTI (Moving Target Indication) radar systems have been built for many years, based on . The simple MTI delay-line canceller shown in Fig.4 is an example of a. Download scientific diagram | Block Diagram for Double Delay Line Canceller from publication: Implementation of MTI based Pulse compression Radar system . The MTI radar uses Low Pulse Repetition Frequency (PRF) to avoid range ambiguities. . Y. &. D. E. S. I. G. N. I. I. S. T. Effect of delay line canceller on the signal.
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Therefore, the output of Full Wave Rectifier looks like as shown in the following figure. The output of the carrier gate 15 is connected to an input of an upconverter mixer 1’8 which is driven by a stable local oscillator or stalo In addition, since the carrier gate 15 is triggered by the output of a frequency divider 17 which in turn is controlled by the voltage controlled crystal oscillator 14, the.
Hence, complete cancellation of the two signals will not take place and an output from the IF output 46 will be obtained. Homodyne FMCW radar range resolution effects with sinusoidal nonlinearities in the frequency sweep.
Radar Systems Delay Line Cancellers
The delay line canceller 13 also includes an AND gate 50 havingone input connected to the IF output 46 and the other input connected to the output of the frequency divider The input 34 of the delay line canceller 13 is connected to two channels; an undelayed channel 35 which includes a phase equalizer 40, and a delayed channel 36 which includes a delay line 41 and a variable gain network During operation of the radar system, signals from the generating means 11 as shown in FIGURE 2D are upconverted by the mixer 11 to the final carrier frequency and after being amplified by the power amplifier 20 they pass through the T-R switch 21 and are transmitted by the antenna 22 in a well known manner.
This invention furthermore permits conversion of more conventional moving target indicator pulsed radar systems utilizing video delay line cancellers to superior performance systems utilizing intermediate dekay delay line cancellers.
This is not delayy severe problem when the period iin the alternating current component cancelle relatively short compared to that of the pulse width, since the residual phase error will only account for a small portion of the total signal width. The advantage of double delay line canceller is that it rejects the clutter broadly.
Radar Systems – Delay Line Cancellers
In a radar system comprising: An example embodiment of the invention radr now be described with reference to the accompanying drawings in which:. What is claimed is: In addition, since the carrier gate 15 is triggered by the output of a frequency divider 17 which in turn is controlled by the voltage controlled crystal oscillator 14, the phase of the alternating current component of each pulse signal, illustrated in FIGURE 2D, will be constant.
These pulses are then frequency divided by the frequency divider 17 by a ratio of to produce at its output, reference point C, a series of nanosecond D-C gating pulses having a pulse repetition rate of 6. The output of the AND gate 50 is connected to one input of an amplitude demodulator 51 which utilizes as its reference signal the output of the voltage controlled crystal oscillator The output of two delay line cancellers, which are cascaded, will be equal to the square of the output of single delay line canceller.
The signals from the channel outputs 32 and 33 are then subtracted by the substractor network Fischer, Ottawa, n- tario, Canada, and John 0.
USA – Delay line canceller for radar system – Google Patents
On the other hand, a reflected signal from a moving delsy will differ from its predecessor at least in phase because the object will move through a distance between successive pulses which is not negligible compared with lihe transmitter wavelength.
The phase demodulator 53 is, in turn, connected through an integrating amplifier 55, the output of which is used to control the frequency of the voltage controlled crystal oscillator If two such delay line cancellers are cascaded together, then that combination is called Double delay line canceller.
The output of the mixer 31 is coupled through an IF amplifier 32 to one input of an OR gate 33 which, in turn, is connected to the input 34 of the delay line canceller Another object of the invention is to provide a means for dynamically controlling the relative gain of the delayed and undelayed channels in the delay line canceller so that consecutive pulse signals returned from stationary targets will be substantially cancelled out.
Thus, reilected cancelldr from stationary objects will be cancelled out and only those from moving objects will appear on the radar display.
The phase equalizer 40 is connected to the output 43 of a subtractor network 45 which is connected at its outwork linee is connected to the output 44 of the delayed channel The improvement comprises means for connecting a sample of the alternating current pulse signal generated by the transmitter in the radar system to the input of the delay line canceller; means for comparing the amplitude and phase of the alternating current component of this signal at the subt-racted output of the canceller against the alternating current component of the transmitter pulse signal samples.
US3373427A – Delay line canceller for radar system – Google Patents
As the name suggests, delay line introduces a certain amount of delay. The generating means 11 inculdes a voltage controlled crystal oscillator 14 which is connected to one input of a carrier gate 15 and also to a pulse generator In accordance with the present invention there is provided an improved moving target indicator for a radar indicator for a radar system employing a delay line canceller. In on typical embodiment, this oscillator 14 produces a signal cacneller a frequency of The signal from reference point A is fed to the carrier gate which is canceeller by the signal from reference point Dela so as to produce at its output, reference point D, a series of alternating current pulse signals having an A-C component of It is also called single Delay line canceller.
So, the delay line is mainly used in Delay line canceller in order to introduce a delay of pulse repetition time. March l2, T. Signal processor for reducing clutter and eliminating range ambiguities in target detection systems.
In a radar system, any received signal reilected from a stationary object will be exactly edlay, in magnitude and phase, to the preceding one, being displaced from it in time by the period of successive transmitter pulses. Delay line canceller is a filter, which eliminates the DC components of echo signals received from stationary targets.
Find the first, second and third blind speeds of this Radar.
When the signals are reflected from stationary objects, the time delay in the channel 36 which includes the delay line 41 is equal to the period between successive transmitted pulses. We will get the following mathematical relation from the second delay line canceller. Similarly, a difference in gain between the two channels 35 and 36 results in an output signal from the subtractor network lihe which is coupled through the AND gate 5 to the amplitude demodulator 51 where it is referenced against a signal from the voltage controlled crystal oscillator An example embodiment of the invention will now be described with reference to the accompanying drawings in ij A phase error signal will then be coupled from the phase demodulator 53 and after passing through the integrating amplifier 55 will be used to control the frequency of the voltage controlled crystal oscillator Complete cancellaion will only occur when the period of the signal from the carrier gate 15 is equal to the time delay of the delay line 41, the initial phase of the alternating current component of each pulse signal at D is a constant, the received IF signals reflected from targets are identical in frequency to those at the output of ,ine carrier gate 15, lline the gains of the two channels 35 and 36 are equal.