PSEUDO-RANDOM CODED DOPPLER TRACKING AND RANGING

• US 3,727,222 A
• Filed: 11/17/1970
• Issued: 04/10/1973
• Est. Priority Date: 11/17/1970
• Status: Expired due to Term

• Current Assignee: Walter C. Hollis
• Original Assignee: Walter C. Hollis
• Inventors: Hollis, Walter C.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Montone, G. E.
• Application Number:
  US05/090,276
• Time in Patent Office: 875 Days
• Field of Search: 343/17.1PF,17.1R,13R,7.5 356/5
• US Class Current: 342/80
• CPC Class Codes: G01S 13/222 using random or pseudorandom pulse repetition frequency
• CPC Class Codes: G01S 13/583 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G01S 13/66 Radar-tracking systems; Analogous systems

Abstract

A gated continuous wave system is described in which the transmitter and receiver are gated alternately to transmit and receive signals. The gating of the transmitter and receiver is controlled by a code generator which cyclically produces pseudorandom sequences of gating pulses for both the receiver and transmitter. By this means, the reflected transmitted signal will always be sensed by the receiver provided that the delay does not exceed the period of each sequence of pseudo-random gating pulses.

Claims

1. A data transmitting and receiving system, comprising data transmitting means operative when activated to transmit a signal, data receiving means operative when activated to receive a signal derived from the transmitted signal, and control means operatively connected to activate the transmitting and receiving means, the control means being operative to activate the transmitting means for each ON period of a sequence of ON and OFF periods, the relative lengths of the periods being predetermined and such that each part of the sequence measured from the beginning of the sequence differs from the next following part of equal length, the control means being operative to activate the receiving means during each said OFF period.

2. A system according to claim 1, including an antenna connected to the data transmitting and receiving means to radiate and receive said signal.

3. A system according to claim 2, wherein said control means comprises means for repetitively generating a pseudo-random binary code and means responsive to said binary code to produce a first group of pulses to control the ON and OFF periods of the data transmitting means and a second group of pulses to control the ON and OFF periods of the data receiving means.

4. A gated transmitter and receiver system comprising an antenna, a transmitter connected to transmit signals to said antenna, a receiver connected to receive signals from said antenna, first gating means for gating the signals from the transmitter to the antenna, second gating means for gating the signals from the antenna to the receiver, and code generating means for alternately operating said first and second gating means by means of, respectively, recurringly generated first and second pluralities of pulses, the pulses of said first and second pluralities of pulses being of such predetermined durations and recurring at such predetermined times that all signals transmitted by the antenna and sensed thereby upon reflection by a target will be registered by the receiver provided that the delay between transmission and reception of the signal does not exceed the duration of said first and said second plurality of pulses.

5. A search radar system, comprising an antenna, a transmitter connected to the antenna, a receiver connected to the antenna, a code generator connected to the transmitter and receiver to alternatiVely enable the transmitter and receiver by means of respective recurring groups of predetermined transmitter and receiver pulses, the pulses of the two groups being such that signals transmitted by the antenna and received by the antenna upon reflection within the duration of each group of pulses will be processed by the receiver, a delay shift register connected to the code register for delaying the group of transmitter pulses, a coincidence matrix connected to receive the outputs of the code generator and the delay shift register whereby to simulate receiver output signals for different discrete target ranges, and comparison means for comparing the receiver output signal with the simulated output signals to determine between which pair of adjacent discrete target ranges the range represented by the receiver output signal lies.

6. A system according to claim 5 wherein said coincidence matrix comprises a plurality of AND gates each having first and second inputs and an output, one input of each AND gate being connected to a corresponding output of the delay shift register and the other input of each AND gate being connected to receive said group of diode switch pulses, a plurality of pairs of linear gates, each linear gate having first and second inputs and one output, means interconnecting the first inputs of each pair of linear gates to the outputs of corresponding AND gates and connecting the second inputs of the linear gates to receive the output of the receiver, difference means connected to the outputs of each pair of linear gates to provide an output signal representative of the difference in output signals from each pair of linear gates, and a threshold circuit connected to the output of each difference means to pass the output signal from the difference means only when the amplitude of the output signal exceeds a predetermined value.

7. A radar tracking system comprising an antenna, a transmitter, a receiver, a code generator connected to the transmitter and receiver to recurringly connect the transmitter and receiver alternately to the antenna under the control of respective first and second groups of predetermined coded pulses, said first and second groups of coded pulses being such that the signals transmitted by the antenna and which return to the antenna within the duration period of each group of coded pulses can be received by the receiver to enable an unambiguous determination of the distance travelled by the transmitted signal.

8. A system according to claim 7, including a range tracker connected to the receiver and the code generator to receive said second group of coded pulses for determining the distance travelled by the transmitted signal.

9. A system according to claim 8, including a frequency tracker connected to the receiver and the range tracker to determine the doppler frequency imposed upon the transmitted signal on its journey to and from the antenna.

10. A system according to claim 7, including a monopulse feed arrangement operable to cause the received signal to be modulated by an error signal representative of the attitude of the antenna relative to the direction in which a target to be tracked lies, an error signal demodulator connected to the receiver to detect said error signal, and antenna attitude servo control means connected to the error demodulator to control the attitude of the antenna in dependence upon the error signal.

11. A system according to claim 7, wherein said range tracker comprises first, second and third linear gates each having first and second inputs and an output, the first output of each gate being connected to the receiver, first and second difference means each having first and second inputs, the first input of each difference means being connected to the output of the second linear gate, and the second inputs of the first and second difference means being connected to the outputs of the first and third linEar gates, first and second threshold devices each having an input and an output, the inputs of the threshold devices being respectively connected to the outputs of the first and second difference means, third difference means having first and second inputs and an output, said first and second input being respectively connected to the outputs of the first and second threshold devices, a code generator similar to the first mentioned code generator, a controllable pulse generator for driving the code generator in dependence upon the output of said third difference means, first, second and third AND gates each having first and second inputs and an output, the first input of each AND gate being connected to receive said first group of coded pulses from said first mentioned code generator and the outputs of the AND gates being respectively connected to the second inputs of the first, second and third linear gates, and delay means interconnecting the second mentioned code generator with the second inputs of the AND gates whereby to delay the code generator output to the first, second and third AND gates respectively by O, T and at least 2 1/2 T where T is the period of the pulses generated by the controllable pulse generator.