Radar based highway safety warning system

A receiver for receiving messages transmitted thereto comprising:

• a receive antenna;
• a detector/mixer operatively connected to receive a signal output from said receive antenna;
• a fixed or variable frequency first local oscillator operatively connected to provide a fixed or an adjustable difference frequency signal to said mixer;
• an intermediate frequency stage having an IF bandwidth and receiving an output of said mixer, said intermediate frequency stage being operative to adjust one of said local oscillator or a second local oscillator to place said output of said mixer in a center region of said IF bandwidth in response to receipt of a CW marker signal;
• a frequency discriminator configured to produce, after cessation of receipt of said CW marker signal, a predetermined voltage each time the frequency of said signal output from said receive antenna varies, a logical state of a bit of said message being changed from a logical state of a preceding bit when said frequency of said signal output sweeps in frequency by a predetermined amount.

A transceiver for transmitting a message to a vehicle comprising:

• an antenna;
• a modulator, said modulator being one of a phase modulator and a frequency modulator;
• an oscillator responsive to said modulator to produce one of a phase modulated and a frequency modulated signal;
• a mixer;
• a turnstile circuit routing a first portion of said modulated signal to said antenna and a second portion of said modulated signal to said mixer, said turnstile circuit further routing a radar reflection from said vehicle received by said antenna to said mixer;
• a discriminator operatively connected to receive an output of said mixer, said output of said mixer having a frequency indicative of a speed of said vehicle, said discriminator producing a voltage indicative of said speed of said vehicle;
• and
• a modulation controller responsive to said voltage to control said modulator to modulate one of frequency and phase of said portion of said modulated signal routed to said antenna to produce transitions detectable by a receiver in said vehicle, said transitions comprising portions of said message.

A transceiver for transmitting a message to a vehicle operating at excessive speed comprising:

• an antenna;
• a variable frequency oscillator responsive to a controller to produce a swept frequency signal;
• a mixer;
• a turnstile circuit routing a first portion of said swept frequency signal to said antenna and a second portion of said swept frequency signal to said mixer, said turnstile circuit further routing a radar reflection from said vehicle received by said antenna to said mixer;
• a discriminator operatively connected to receive an output of said mixer, said output of said mixer having a frequency indicative of a speed of said vehicle, said discriminator producing a voltage indicative of said speed of said vehicle;
• said controller being responsive to said voltage to control said variable frequency oscillator to sweep said frequencies within at least a portion of said frequency band at a first rate and a second rate, said first rate representing a first logical state and said second rate representing a second logical state of bits of said message transmitted by said transceiver.

A transceiver for transmitting a message to a vehicle operating at excessive speed comprising:

• an antenna;
• a variable frequency oscillator responsive to a controller to produce a swept frequency signal;
• a mixer;
• a turnstile circuit routing a first portion of said swept frequency signal to said antenna and a second portion of said swept frequency signal to said mixer, said turnstile circuit further routing a radar reflection from said vehicle received by said antenna to said mixer;
• a discriminator operatively connected to receive an output of said mixer, said output of said mixer having a frequency indicative of a speed of said vehicle, said discriminator producing a voltage indicative of said speed of said vehicle;
• said controller being responsive to said voltage to control said variable frequency oscillator to sweep frequency in a first direction from a higher frequency to a lower frequency and in a second direction from a lower frequency to a higher frequency, said first and second directions each representing a different logical state of bits of said message transmitted by said transceiver.

A message detector responsive to a CW marker to receive messages transmitted thereto comprising:

• a receive antenna;
• a detector/mixer operatively connected to receive a signal output from said receive antenna;
• a fixed or variable frequency first local oscillator operatively connected to provide a fixed or an adjustable difference frequency signal to said mixer;
• an intermediate frequency stage having an IF bandwidth and receiving an output of said mixer, said intermediate frequency stage being operative to set up said message detector to receive said message by adjusting one of said local oscillator or a second local oscillator to place said output of said mixer in a center region of said IF bandwidth in response to receipt of said CW marker signal, wherein said message detector receives said message after said CW marker signal turns off;
• a frequency discriminator producing a predetermined voltage each time the frequency of said signal output from said receive antenna varies after receipt of said CW marker, a logical state of a bit of said message being changed from a logical state of a preceding bit when said frequency of said signal output from said receive antenna sweets within said IF bandwidth by a predetermined amount.