Dual-mode radar system

Claim 2

A multimode radar system useful over a wide range of radar altitudes and comprising in combination a single common transmitter arranged for operation in an alternative one of a 50 percent duty cycle-interrupted continuous wave mode and a Bessel sideband FM-CW mode; and mode-switching means responsive to radar range for selecting said interrupted continuous wave mode under radar range conditions greater than a preselected range and selecting said FM-CW mode under radar range conditions less than said preselected radar range.

Claim 3

The device of claim 1 in which there is provided receiver local oscillator injection means comprising: a stable local oscillator for providing a source of a preselected intermediate frequency; frequency translation means responsive to said stable local oscillator and to a Bessel function generator of said FM-CW mode for providing a first output corresponding to a third-order Bessel function, a second output corresponding to a sixth-order Bessel function, a third output corresponding to the sum of said preselected intermediate frequency and said third-order Bessel function, and a fourth output corresponding to the sum of said preselected intermediate frequency and said sixth-order Bessel function; single-sideband modulating means for generating a receiver local oscillator signal being responsive to a continuous wave source of said transmitter and alternatively responsive to said third output of said frequency translation means during said interrupted continuous wave mode and to said preselected intermediate frequency during said FM-CW mode.

Claim 4

The device of claim 2 in which there is further provided gating means responsive to, said mode switching means during said interrupted continuous wave mode for gating on said third output of said frequency translation means during an interrupted state of said interrupted continuous wave mode.

Claim 5

The device of claim 2 in which there is further provided a single common velocity-receiver for use in both modes of operation of said multimode radar system and comprising: a first receiver-mixer having a local oscillator input responsive to said local oscillator injection means for providing an intermediate frequency receiver signal; band-pass filter means responsive to said intermediate frequency receiver signal and having a tuned center frequency equal to the sum of said preselected intermediate frequency and said third-order Bessel function; a second receiver-mixer having a local oscillator first input responsive to said fourth output of said signal translation means and further having a second input responsively coupled to an output of said band-pass filter means; and doppler frequency tracking means responsively coupled to an output of said second receiver mixer for providing an analog signal output indicative of the doppler velocity of a detected target.

Claim 6

The device of claim 4 in which there is further provided leakage elimination filter means interposed between said doppler frequency tracking means and said output of said second receiver mixer and responsive to said first output of said frequency translation means for reducing signal energy components other than those due to a received target siGnal.

Claim 7

The device of claim 4 in which there is further provided leakage elimination filter means, comprising: dual-channel means commonly coupled to an output of said second receiver mixer for providing a first and second receiver signal having a mutually quadrature time phase relationship, said dual-channel means including a first and second filter mixer, each responsive to a mutually exclusive one of said first and second receiver signals and further commonly responsive to said first output of said frequency-translating means; first and second low-pass filter means, each responsively coupled to an output of a mutually exclusive one of said first and second filter mixer; and signal combining means responsively coupled to said low-pass filter means for providing a signal output having a frequency indicative of the doppler velocity of a detected target.

Claim 8

The device of claim 4 in which there is further included automatic gain control means in series circuit with said band-pass filter means and having a gain control input responsive to the signal level of the received target signal in said doppler frequency tracking means.

Claim 9

A multimode radar system useful over a wide range of radar altitudes for providing both doppler velocity and range (distance) information, and comprising in combination a single common source of radio energy to be transmitted; a high duty-ratio coherent pulse system in cooperation with said source; a Bessel sideband FM-CW system in cooperation with said source; and mode-switching means responsive to radar range for coupling said transmitter to said high duty-ratio coherent pulse system at radar ranges greater than a preselected radar range and coupling said transmitter to said FM-CW system at radar ranges less than said preselected range.

Claim 10

A multimode radar system useful over a wide range of radar altitudes for providing both doppler velocity and range (distance) information, and comprising in combination a single common source of radio energy to be transmitted; a high duty-ratio coherent pulse system in cooperation with said source; a Bessel sideband FM-CW system in cooperation with said source; and mode-switching means responsive to radar range for coupling said transmitter to said high duty-ratio coherent pulse system at radar ranges greater than a preselected radar range and coupling said transmitter to said FM-CW system at radar ranges less than said preselected range.

Claim 11

The device of claim 8 in which there is further provided a single common intermediate frequency receiver channel for coupling a received signal to a respective range processor of said high duty-ratio coherent pulse system and said FM-CW system, said receiver channel having a local oscillator input; and dual-mode local oscillator injection means having an output coupled to the local oscillator input of said receiver channel and being responsive to said mode-switching means for compensatorily frequency translating the local oscillator frequency input of said receiver channel during an interrupted portion of the operation of said high duty-ratio coherent pulse system, whereby the intermediate frequency received signal bandwidths of the two modes of said multimode radar are mutually compatible.

Claim 12

The device of claim 8 in which there is further provided: an intermediate frequency receiver channel adapted to be responsive to a received signal and having a local oscillator input; a doppler frequency tracker responsive to an output of said receiver channel; dual-mode local oscillator injection means having an output coupled to the local oscillator input of said receiver channel and being responsive to said mode-switching means for compensatorily frequency translating the local oscillator frequency input of said receiver input of said receiver channel during an interrupted portion of the operation of said high duty-ratio coherent pulse system, whereby the bandwidths of the intermediate frequency receiver signals of said two modes of said multimode radar are mutually compatible.

Claim 13

The device of claim 10 in which said intermediate frequency receiver channel further includes bandwidth-limited frequency-translating means interposed at the output thereof for reducing said receiver signal to a frequency corresponding to a doppler shift of said receiver signal.

Claim 14

A multimode radar system having a high duty-ratio coherent pulse mode of operation at radar altitude conditions greater than a preselected altitude and a Bessel sideband FM-CW mode at radar altitude conditions less than said preselected altitude, and comprising in combination: a voltage-controlled RF oscillator having a control input; a switchable pulse modulator arranged for pulse modulation of the output of said voltage controlled oscillator; a switchable FM-CW oscillator for frequency modulation of said RF oscillator; a high-duty cycle interrupted continuous wave pulse repetition frequency generator having a first input coupled to an output of said pulse modulator and further having a second input and an output; FM-CW range-processing means having an input and an output; a receiver having a switchable local oscillator input and output coupled to an input of an alternative one of said pulse repetition frequency generator and said range-processing means; local oscillator means input coupled to said pulse modulator and having an output switchable coupled to said switchable input of said receiver; range computer means having an input switchably coupled to the output of an alternative one of said pulse repetition frequency generator and said range processing means for generating a two-state control output indicative of a radar range condition relative to a preselected radar range, for switching control of said switchable elements.

Claim 15

A multimode radar system having a high duty-ratio coherent pulse mode of operation at radar altitude conditions greater than a preselected altitude and a Bessel sideband FM-CW mode at radar altitude conditions less than said preselected altitude, and comprising in combination: a voltage-controlled RF oscillator having a control input; a switchable pulse modulator arranged for pulse modulation of the output of said voltage controlled oscillator; a switchable FM-CW oscillator for frequency modulation of said RF oscillator; a high-duty cycle interrupted continuous wave pulse repetition frequency generator having a first input coupled to an output of said pulse modulator and further having a second input and an output; FM-CW range-processing means having an input and an output; a receiver having a switchable local oscillator input and output coupled to an input of an alternative one of said pulse repetition frequency generator and said range-processing means; local oscillator means input coupled to said pulse modulator and having an output switchable coupled to said switchable input of said receiver; range computer means having an input switchably coupled to the output of an alternative one of said pulse repetition frequency generator and said range processing means for generating a two-state control output indicative of a radar range condition relative to a preselected radar range, for switching control of said switchable elements.

Claim 16

The device of claim 12 in which such switchable elements are arranged to cooperate in response to a first state of said control output whereby said FM-CW oscillator is coupled for frequency modulation of said RF oscillator, said pulse modulator continuously output couples the output of said voltage controlled oscillator, said local oscillator input of said receiver is responsively coupled to said local oscillator means, said output of said receiver is drivingly coupled to said input of said range processor, and said input of said range computer is drivingly coupled to the output of said range processor.

Claim 17

The device of claim 12 in which said switchable elements are arranged to cooperate in response to a second state of said control output whereby said pulse modulator is responsively coupled to an output of said pulse repetition frequency generator for pulse modulation of the output of said RF oscillator, said input of said range computer is responsively coupled to said output of said pulse repetition frequency generator, and said second input of said pulse repetition frequency generator is responsively coupled to the output of said receiver.

Claim 18

A multimode radar system useful over a wide range of radar altitudes and comprising in combination: switchable and modulatable transmitter means; an intermediate frequency receiver stage having a local oscillator input; a frequency-modulated continuous wave range processor responsively coupled to said receiver stage; an interrupted continuous wave pulse repetition frequency generator responsive to said receiver stage for providing a two-state output corresponding to a respective transmit state and receive state; a continuous wave oscillator for modulating said modulatable transmitter means; an intermediate frequency stable local oscillator for providing a first local oscillator modulating frequency; gated second intermediate-frequency-modulating means responsively coupled to said stable local oscillator and to said continuous wave oscillator for providing a gated second local oscillator modulating frequency, said frequency means being further responsive to a receive state of said output of said pulse repetition frequency generator; mode control means responsive to said pulse repetition frequency generator and to said range processor for providing a two-state mode control signal indicative of a preselected radar range state; and dual-mode local oscillator injection means including a single-sideband modulator having a first input responsive to a modulatable carrier frequency of said transmitter means and further having a switchable modulation input responsive to an alternative one of said local oscillator Modulating frequencies, said local oscillator injection means further having a switch control input responsive to said mode control means, a preselected one of said first and second modulating frequencies being coupled to said modulation input in response to a preselected state of said mode control signal, said transmitter means being further arranged to be switched off in response to said receive state of said pulse repetition frequency generator and to be modulated by said continuous wave oscillator in response to a preselected state of said mode control signal.

Claim 19

A multimode radar system useful over a wide range of radar altitudes and comprising in combination: switchable and modulatable transmitter means; an intermediate frequency receiver stage having a local oscillator input; a frequency-modulated continuous wave range processor responsively coupled to said receiver stage; an interrupted continuous wave pulse repetition frequency generator responsive to said receiver stage for providing a two-state output corresponding to a respective transmit state and receive state; a continuous wave oscillator for modulating said modulatable transmitter means; an intermediate frequency stable local oscillator for providing a first local oscillator modulating frequency; gated second intermediate-frequency-modulating means responsively coupled to said stable local oscillator and to said continuous wave oscillator for providing a gated second local oscillator modulating frequency, said frequency means being further responsive to a receive state of said output of said pulse repetition frequency generator; mode control means responsive to said pulse repetition frequency generator and to said range processor for providing a two-state mode control signal indicative of a preselected radar range state; and dual-mode local oscillator injection means including a single-sideband modulator having a first input responsive to a modulatable carrier frequency of said transmitter means and further having a switchable modulation input responsive to an alternative one of said local oscillator Modulating frequencies, said local oscillator injection means further having a switch control input responsive to said mode control means, a preselected one of said first and second modulating frequencies being coupled to said modulation input in response to a preselected state of said mode control signal, said transmitter means being further arranged to be switched off in response to said receive state of said pulse repetition frequency generator and to be modulated by said continuous wave oscillator in response to a preselected state of said mode control signal.

Claim 20

The device of claim 15 in which there is further provided a single common velocity-receiver for use in both modes of operation of said multimode radar system and comprising: a first velocity receiver-mixer having a local oscillator input responsive to said local oscillator injection means for providing an intermediate frequency receiver signal; band-pass filter means responsive to said intermediate frequency receiver signal and having a tuned center frequency equal to the sum of said preselected intermediate frequency and a third-order Bessel function; a second receiver-mixer having a local oscillator first input responsive to the sum of said preselected intermediate frequency and a sixth-order Bessel function and further having a second input responsively coupled to an output of said band-pass filter means; and doppler frequency tracking means responsively coupled to an output of said second receiver mixer for providing an analog signal output indicative of the doppler velocity of a detected target.

Claim 21

The device of claim 16 in which there is further provided leakage elimination filter means interposed between said doppler frequency tracking means and said output of said second receiver mixer and responsive to said third-order Bessel function for reducing signal energy components other than those due to a received target signal.

Claim 22

The device of claim 16 in which there is further provided leakage elimination filter means, comprising: dual-channel means commonly coupled to an output of said second receiver mixer for providing a first and second receiver signal having a mutually quadrature time phase relationship, said dual-channel means including a first and second filter mixer, each responsive to a mutually exclusive one of said first and second receiver signals and further commonly responsive to said third-order Bessel function; first and second low-pass filter means, each responsively coupled to an output of a mutually exclusive one of said first and second filter mixer; and signal combining means responsively coupled to said low-pass filter means for providing a signal output having a frequency indicative of the doppler velocity of a detected target.

Claim 23

The device of claim 16 in which there is further included automatic gain control means in series circuit with said band-pass filter means and having a gain control input responsive to the signal level of the received target signal in said doppler frequency tracking means.