Vehicular traffic sensor
View Patent ↗A vehicle traffic sensor for detecting and monitoring vehicular targets is presented. The sensor employs a planar design resulting in a reduced profile sensor. The sensor includes a multi-layer radio frequency board with RF components on one of the sides and both isolation and planar array antennas on the opposing side. The antennas are preferably tapered planar array antennas which include one transmit antenna and one receive antenna. The sensor also includes at least one logic or signal processing board populated with components on a first side and a ground plane on a second side positioned toward the RF componentry of the RF board to form an RF shield. The boards are housed within a housing that is permeable, at least on the side through which the antenna structures propagate.
1. A sensor for monitoring vehicles on a roadway, the sensor comprising:
a transmit portion comprising:
a digital signal generator for digitally generating a modulated signal for transmission; and
a transmit antenna for transmitting the modulated signal towards vehicles on a roadway;
a received portion comprising:
a receive antenna for receiving reflections of the modulated signal from vehicles on the roadway, wherein the reflections of the modulated signal are processed to produce traffic data representing the vehicles on the roadway;
wherein the transmit antenna and the receive antenna comprise a single antenna used to transmit the modulated signal and to receive the reflections of the modulated signal, respectively.
2. A sensor as defined in claim 1 , wherein the digital signal generator further comprises at least one of:
a direct digital synthesizer that is coupled with a phase locked loop;
a modulated signal digital generator and an up-converter; and a direct digital to analog conversion generator that produces the modulated signal.
3. A sensor as defined in claim 1 further comprising a housing for enclosing said transmit portion and said receiving portion.
4. A sensor as defined in claim 1 , wherein said digital signal generator further comprises:
a direct digital synthesizer for generating a low frequency waveform for said transmit antenna of said sensor;
a phase lock loop coupled to said direct digital synthesizer for tracking said low frequency waveform; and
a voltage controlled oscillator coupled to said phase lock loop for generating a modulate transmit signal.
5. A sensor as defined in claim 1 , wherein said modulated signal is from 10.5 megahertz to 10.55 megahertz.
6. A sensor as defined in claim 1 , wherein said transmit antenna and said receive antenna comprise a plurality of series-configured loop elements arranged in tapered arrays.
7. A sensor as defined in claim 1 , wherein said transmit antenna and said receive antenna comprise a plurality of series-configured loop elements comprising:
a wide coplanar slot for reducing the effects of manufacturing variations; and grounding vias for preventing unwanted signal propagation.
8. A sensor as defined in claim 7 , where said vias are located 25 mils from said slot.
9. A sensor for monitoring vehicles on a roadway, the sensor comprising:
a transmit portion comprising:
a digital signal generator for digitally generating a modulated signal; and
a transmit antenna for transmitting the modulated signal towards vehicles on a roadway;
a receiving portion comprising:
a receive antenna for receiving reflections of the modulated signal from vehicles on the roadway, wherein the reflections of the modulated signal are processed to produce traffic data representing the vehicles on the roadway;
wherein the transmit antenna and the receive antenna comprise a single antenna used to transmit the modulated signal, respectively, and to receive the reflections of the modulated signal and wherein the transmit antenna is a first array of series fed coplanar loop elements and the receive antenna is a second array of series fed coplanar loop elements.
10. A sensor as defined in claim 9 , wherein said digital signal generator further comprises:
a digitally modulated signal generator for generating a modulated signal;
an oscillator for generating an RF tone; and
a frequency mixer for mixing said modulated signal and said RF tone to form a signal comprised of sum and difference frequencies.
11. A sensor as defined in claim 9 , wherein said receiving portion further includes:
a bandpass filter coupled to said receive antenna for filtering said received reflections of said modulated signal;
an amplifier coupled to said bandpass filter for amplifying said received reflections of said modulated signal; and
a mixer coupled to said amplifier for frequency mixing said received reflections of said modulated signal with additional RF signals.
12. A sensor for monitoring vehicles on a roadway, the sensor comprising:
a transmit portion comprising:
a digital signal generator that digitally generates a modulated signal for transmission; and
an antenna for transmitting the modulated signal towards vehicles on a roadway and receiving reflections of the modulated signal from vehicles on the roadway, wherein the reflections of the modulated signal are processed to produce traffic data representing the vehicles on the roadway and wherein said antenna is used to transmit the modulated signal and to receive the reflections of the modulated signal.
13. A sensor as defined in claim 12 , wherein said antenna comprises a plurality of series-configured loop elements arranged in a tapered array.
14. A sensor as defined in claim 13 , wherein said antenna comprises at least a pair of tapered arrays.
15. A sensor as defined in claim 12 , wherein said antenna comprises a first array of series fed coplanar loop elements and a second array of series fed coplanar loop elements.
16. A sensor as defined in claim 12 , further comprising a circulator for controlling the different times that said antenna is used to either transmit said modulated signal or receive reflections of said modulated signal.
17. A sensor as defined in claim 12 , wherein said digital signal generator further comprises at least one of:
a direct digital synthesizer that is coupled with a phase locked loop; and
a modulated signal digital generator and an up-converter.
18. A sensor as defined in claim 12 , wherein said digital signal generator further comprises:
a direct digital to analog converter for directly generating a modulated signal at RF frequencies.
19. A sensor as defined in claim 12 , wherein said digital signal generator further comprises:
a direct digital synthesizer for generating a low frequency waveform for said transmit antenna of said sensor;
a phase lock loop coupled to said direct digital synthesizer for tracking said low frequency waveform; and
a voltage controlled oscillator coupled to said phase lock loop for generating a modulate transmit signal.
20. A sensor as defined in claim 12 , wherein said digital signal generator further comprises:
a digitally modulated signal generator for generating a modulated signal;
an oscillator for generating an RF tone; and
a frequency mixer for mixing said modulated signal and said RF tone to form a signal comprised of sum and difference frequencies.