Testing circuit for radar-operated vehicle safety assurance systems

Claim 2

A testing circuit for a radar-operated safety assurance system for a roadway vehicle including means for transmitting a train of microwave burst energy and receiving a return signal from a target, means for mixing the return signal with a locally generated signal to derive an intermediate frequency return signal, means for sensing the roadway speed of said vehicle, relative speed detecting means for deriving the speed of said vehicle relative to said target from said intermediate frequency return signal, range detecting means for deriving the range of said target from said intermediate frequency return signal, and a decision making circuit responsive to said sensed vehicle roadway speed, said derived relative vehicle speed and said derived range of the target to determine a safety distance to said target, comprising: means for generating an artificial intermediate frequency return signal from a hypothetical target, said artificial return signal comprising a train of intermediate frequency burst signals which occur at intervals that decrease as a function of time; means for generating a signal indicative of a predetermined vehicle roadway speed; means for switching said radar system in response to a manual command from a normal operating mode to an under-test mode in which said relative speed detecting means and said range detecting means are receptive of said generated artificial intermediate frequency return signal and said decision making circuit is receptive of said generated predetermined vehicle roadway speed indicative signal, whereby said decision making circuit determines a safety distance to said hypothetical target and generates an output signal when the instantaneous value of the distance to said hypothetical target derived by said range detecting means corresponds to said determined safety distance to said hypothetical target; and means for determining whether said output signal from said decision making circuit occurs within a predetermined time interval.

Claim 3

A radar-operated safety assurance system for a roadway vehicle, comprising: means for transmitting a train of microwave burst energy and receiving a return signal from a target; means for mixing the return signal with a locally generated signal to derive an intermediate frequency return signal; means for sensing the roadway speed of said vehicle; relative speed detecting means for deriving the speed of said vehicle relative to said target from said intermediate frequency return signal; range detecting means for deriving the range of said target from said intermediate frequency return signal; a decision making circuit responsive to said sensed vehicle roadway speed, said derived relative vehicle speed and said derived range of the target to determine a safety distance to said target; means for generating an artificial intermediate frequency return signal from a hypothetical target, said artificial return signal comprising a train of intermediate frequency burst signals which occur at intervals that decrease as a function of time; means for generating a signal indicative of a predetermined vehicle roadway speed; means for switching said relative speed detecting means and said range detecting means from a normal operating mode to an under-test mode to receive said artificial intermediate frequency return signal instead of said intermediate frequency signal derived from said mixing means and switching said decision making circuit to receive said generated predetermined vehicle roadway speed indicative signal instead of the output from said speed sensing means, whereby said decision making circuit determines a safety distance to said hypothetical target and generates an output signal when the instantaneous value of distance to said hypothetical target derived by said range detecting means corresponds to said determined safety distance to said hypothetical target; and means for determining whether said output signal from said decision making circuit occurs within a preselected time interval.

Claim 4

A radar-operated safety assurance system for a roadway vehicle, comprising: means for transmitting a train of microwave burst energy and receiving a return signal from a target; means for mixing the return signal with a locally generated signal to derive an intermediate frequency return signal; means for sensing the roadway speed of said vehicle; relative speed detecting means for deriving the speed of said vehicle relative to said target from said intermediate frequency return signal; range detecting means for deriving the range of said target from said intermediate frequency return signal; a decision making circuit responsive to said sensed vehicle roadway speed, said derived relative vehicle speed and said derived range of the target to determine a safety distance to said target; means for generating an artificial intermediate frequency return signal from a hypothetical target, said artificial return signal comprising a train of intermediate frequency burst signals which occur at intervals that decrease as a function of time; means for generating a signal indicative of a predetermined vehicle roadway speed; means for switching said relative speed detecting means and said range detecting means from a normal operating mode to an under-test mode to receive said artificial intermediate frequency return signal instead of said intermediate frequency signal derived from said mixing means and switching said decision making circuit to receive said generated predetermined vehicle roadway speed indicative signal instead of the output from said speed sensing means, whereby said decision making circuit determines a safety distance to said hypothetical target and generates an output signal when the instantaneous value of distance to said hypothetical target derived by said range detecting means corresponds to said determined safety distance to said hypothetical target; and means for determining whether said output signal from said decision making circuit occurs within a preselected time interval.

Claim 5

A testing circuit as claimed in claim 1 or 2, wherein said means for generating an artificial intermediate frequency return signal comprises: a first ramp generator for generating a train of ramp voltage waveforms; a second ramp generator for generating a ramp voltage which decreases as a function of time; means for generating a pulse in response to a coincidence in voltage between the output signals from said first and second ramp generators; means for generating a phase-modulated intermediate frequency signal; and gating means for passing said phase-modulated intermediate frequency signal in the presence of said coincidence pulse.

Claim 6

A testing circuit as claimed in claim 3, wherein said first ramp voltage generator includes means for generating each of said ramp voltage waveforms in said train in step with the microwave burst energy transmitted from said radar system.

Claim 7

A testing circuit as claimed in claim 3, wherein said second ramp voltage generator includes means for generating said decreasing ramp voltage in step with said transmitted microwave burst energy.

Claim 10

The method of claim 6 wherein said step of generating an artificial intermediate frequency return signal further includes the steps of: generating a train of ramp voltage waveforms; generating a ramp voltage signal which decreases as a function of time; generating a pulse in response to a coincidence in voltage between said first ramp voltage waveform and said second ramp voltage signal; generating a phase-modulated intermediate frequency signal; and outputting said phase-modulated intermediate frequency signal when said coincidence pulse is generated.

Claim 11

The method of claim 7, wherein each of said ramp voltage waveforms in said train is generated in step with the microwave burst energy transmitted from said radar system.

Claim 12

The method of claim 7, wherein said decreasing ramp voltage is generated in step with said transmitted microwave burst energy.