Variable range cut-off system for dual frequency CW radar

• US 3,898,655 A
• Filed: 01/14/1974
• Issued: 08/05/1975
• Est. Priority Date: 01/14/1974
• Status: Expired due to Term

• Current Assignee: Carl P. Tresselt
• Original Assignee: Carl P. Tresselt
• Inventors: Tresselt, Carl P.
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US05/433,027
• Time in Patent Office: 568 Days
• Field of Search: 343/7A,7.3,7.5,9
• US Class Current: 342/83
• CPC Class Codes: G01S 13/348 using square or rectangular modulation, e.g. diplex radar for ranging over short distances
• CPC Class Codes: G01S 13/50 Systems of measurement based on relative movement of target
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/932 using own vehicle data, e.g. ground speed, steering wheel direction
• CPC Class Codes: G01S 2013/9321 Velocity regulation, e.g. cruise control
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

A system for rendering a CW radar insensitive to targets beyond a variable range, wherein two discrete frequency signals are alternately transmitted so that two doppler frequencies, whose phase relationships are indicative of target range, are produced at the receiver, includes means for turning off the receiver for a variable interval between transmission of the two frequencies and by gating the receiver so that video output is produced only during a portion of each transmitted signal. The variable interval periods are determined in accordance with vehicle speed and/or range to a selected target.

Claims

1. A range cutoff system for a continuous wave radar system wherein said radar system has a transmitter which transmits at least two discrete frequency signals and a receiver for producing doppler frequency signals in response to the reception of return signals from a target of the transmitted frequency signals, said cutoff system comprising:

modulation means for modulating said transmitter so that said discrete frequency signals are alternately transmitted and said transmitter produces no effective output for a variable time period between transmission of said discrete frequency signals and including means responsive to a control signal for varying said time period;

means responsive to predetermined parameters for generating said control signal; and

, means responsive to the return signal from a target for generating a target present signal and including means responsive to said target present signal for ceasing variation of said variable time period whereby said variable time period is thereafter maintained relatively constant.

2. The range cutoff system of claim 1 wherein said radar system is installed in a movable vehicle and wherein said means responsive to predetermined parameters comprises means at least responsive to velocity of said vehicle for generating said control signal.

3. The range cutoff system of claim 1 wherein said receiver comprises means for processing said doppler signals including switching means and wherein said modulation means modulates said switching means so that said means for processing is effective for processing doppler signals only durinG a portion of the time period during which the discrete frequency signals are transmitted.

4. The range cutoff system of claim 1 wherein said receiver comprises at least a two channel receiver for processing at least two doppler frequency signals resulting from transmission of said discrete frequency signals and including switching means for alternately actuating the two channels synchronously with transmission of said discrete frequency signals only during a portion of the time periods during which the discrete frequency signals are transmitted.

5. The range cutoff system of claim 4 wherein said radar system is installed in a vehicle and wherein said means responsive to predetermined parameters comprises means at least responsive to velocity of said vehicle for generating said control signal.

6. The range cutoff system of claim 4 wherein said means responsive to predetermined parameters comprises means for varying said control signal on a predeterined schedule.

7. The range cutoff system of claim 1 wherein said modulation means comprises a timer which generates a cyclically occurring first signal and which generates a cyclically occurring second signal, only one of said first and second signals being instantaneously generated, and which generates a third signal and including means for modifying said third signal, a first of the discrete frequencies being transmitted during the simultaneous occurrence of said first signal and the modified third signal and a second of the discrete frequencies being transmitted during the simultaneous occurrence of said second signal and the modified third signal.

8. The range cutoff system of claim 1 including means responsive to said target present signal for memorizing the range to said target.

9. The range cutoff system of claim 8 wherein said means responsive to predetermined parameters responds at least to said memorized range at least for a predetermined time period after said target present signal is extinguished.