Highway vehicle guidance system

• US 5,684,490 A
• Filed: 03/01/1995
• Issued: 11/04/1997
• Est. Priority Date: 03/01/1995
• Status: Expired due to Fees

• Current Assignee: Ohio State University
• Original Assignee: Ohio State University
• Inventors: Henderson, Lee W., Young, Jonathan D.
• Primary Examiner(s): Carone, Michael J.
• Assistant Examiner(s): MONTGOMERY, CHRISTOPHER KEITH
• Application Number:
  US08/396,575
• Time in Patent Office: 979 Days
• Field of Search: 342/70-72, 342/5-8, 342/10, 342/11, 342/33, 342/34, 342/456, 342/6, 901/1, 404/12, 404/13, 404/14
• US Class Current: 342/70
• CPC Class Codes: G01S 13/106 using transmission of pulses having some particular characteristics G01S13/12, G01S13/22, G01S13/24, G01S13/26, G01S13/28 and G01S13/30 take precedence
• CPC Class Codes: G01S 13/24 using frequency agility of carrier wave
• CPC Class Codes: G01S 13/44 Monopulse radar, i.e. simultaneous lobing
• CPC Class Codes: G01S 13/4454 phase comparisons monopulse, i.e. comparing the echo signals received by an interferometric antenna arrangement
• CPC Class Codes: G01S 13/4463 using phased arrays
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/9318 Controlling the steering
• CPC Class Codes: G01S 2013/93271 in the front of the vehicles
• CPC Class Codes: G01S 2013/93272 in the back of the vehicles
• CPC Class Codes: G01S 2013/9329 cooperating with reflectors or transponders
• CPC Class Codes: G01S 7/02 of systems according to group G01S13/00
• CPC Class Codes: G01S 7/024 using polarisation effects in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems
• CPC Class Codes: H01Q 1/3233 particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
• CPC Class Codes: H01Q 15/0013 said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective

Abstract

A radar highway motor vehicle guidance apparatus for guiding a land vehicle along a roadway using a forward looking, lateral position sensing, monopulse tracking radar guidance apparatus which transmits radar pulses forward of the vehicle. The pulses are reflected back to the vehicle by a stripe distributed along the roadway. The stripe is a frequency selective surface which generates retro-reflective grating lobes at an operating frequency of the tracking radar. Operating the radar at two frequencies allows the radar to look at regions spaced at two different distances from the front of the vehicle. Highway related information may be encoded in the frequency selective surface by variations in the shape or dimensions of the frequency selective stripe morphology in order to modulate the reflected signal with highway information which is then also detected at the radar receiver. Target discrimination is enhanced by using pseudo random codes and matching antenna polarization with stripe polarization.

Claims

1. A radar vehicle guidance apparatus for use in guiding a land vehicle along a roadway and comprising:

(a) a forward looking, lateral position sensing, tracking radar guidance apparatus mounted to the vehicle wherein the radar radiates and detects at least two frequencies, the two frequencies being selected to generate a retro-reflected grating lobe at two angles above the roadway and corresponding to two different distances from the vehicle; and

(b) an elongated stripe distributed along the roadway in the direction of vehicle travel, the stripe comprising substantially laterally aligned antenna elements substantially uniformly spaced at least one-half the wavelength of the radar frequency, formed of electrically conductive material and spaced to provide a frequency selective surface generating retro-reflective, non-specular grating lobes at the operating frequencies of the tracking radar.

2. An apparatus in accordance with claim 1 wherein the radar guidance apparatus comprises a monopulse radar guidance apparatus.

3. An apparatus in accordance with claim 1 wherein the radar apparatus comprises a chirp radar transmitting pulses across a frequency band including said two frequencies.

4. An apparatus in accordance with claim 1 wherein polarization, frequency response and grating lobe angle parameters of the stripe are determined by the size, shape and orientation of said antenna elements, wherein at least one of said parameters is spatially varied along the stripe to modulate incident radar waves and generate waves reflected from the stripe containing roadway related information, and wherein the radar includes a detector for demodulating the reflected signals.

5. An apparatus in accordance with claim 1 wherein the radar has a transmitter which modulates the transmitted radar pulses with a selected pseudo-random code and also has a receiver which discriminates the reflections from said transmitter using correlation techniques.

6. An apparatus in accordance with claim 1 wherein said elements are covered by a weather resistant protective synthetic resin.

7. An apparatus in accordance with claim 1 wherein a ground plane is spaced below said elements for increasing the reflectivity of said stripe.

8. An apparatus in accordance with claim 1 wherein said stripe comprises a series of parallel, substantially equidistantly spaced wires spaced in excess of one half wavelength of said radar operating frequency and less than one wavelength.

9. An apparatus in accordance with claim 1 wherein the antenna elements comprise a series of spaced conductor elements.

10. An apparatus in accordance with claim 1 wherein the antenna elements comprise a conductive sheet material having a pattern of non-conducting slots forming slot antenna elements.

11. A method for guiding a vehicle along a roadway comprising:

directing radar waves at a radar frequency toward the roadway and radar tracking and steering the vehicle to follow retro-reflections from an elongated frequency selective surface formed as a stripe along a roadway by a series of substantially laterally aligned antenna elements formed by a conductive material with substantially uniform spacings between the elements at least one-half wavelength of the radar frequency to generate retro-reflective, non-specular grating lobes from incident radar waves, the radar tracking comprising radiating radar waves at a plurality of frequencies which generate retro-reflecting grating lobes reflected from said stripe at different angles above the roadway, and detecting the waves at said different frequencies corresponding to different distances from the vehicle.

12. A method in accordance with claim 11 and further comprising varying the physical configuration of said elements in a pattern modulating an incident radar wave from a moving vehicle with roadway related information and demodulating the information in a receiver circuit mounted to the vehicle.

13. A method in accordance with claim 11 and further comprising modulating radiated radar waves with a pseudo-random code and discriminating reflected waves by cross correlation.