Short range electromagnetic proximity detection

• US 5,793,309 A
• Filed: 08/14/1996
• Issued: 08/11/1998
• Est. Priority Date: 08/14/1996
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Nellson, George Franklin
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Pope, Daryl C.
• Application Number:
  US08/702,411
• Time in Patent Office: 727 Days
• Field of Search: 340/932.2, 340/435, 340/436, 340/561, 340/552, 340/551, 340/554, 340/903, 342/27, 342/28, 342/59, 342/118, 361/179, 327/189, 331/76
• US Class Current: 340/932.2
• CPC Class Codes: B60Q 9/008 for anti-collision purposes
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: G01S 7/285 Receivers

Abstract

A very low-cost, short-range electromagnetic transceiver uses a low frequency oscillator signal as a means of charging a step recovery diode (SRD) which converts the stored charge into a very short impulse to enable very high energy efficiency frequency multiplication. This impulse is coupled to an antenna which radiates the energy and receives reflections from objects in the vicinity. The energy of the received impulse reflections in an indicator of the distance of the object to the sensor. This system may be used in a vehicle to detect obstructions in its path of motion or a parking facility where it would determine the occupancy of each vehicle parking space. In the parking facility embodiment, information is reported to a central office computer which displays spaces which are not occupied and available for assignment. This system may also be used as a proximity detector for other applications, for example, to automatically detect pedestrians approaching a traffic control signal at a street corner or to detect the proximity of any object to another.

Claims

1. A transceiver for short range electromagnetic proximity detection comprising,

comb signal generating means for generating line spectrum electromagnetic signals in a sequence of groups of said signals,

excitation source means coupled to said comb generating means for supplying a periodic excitation signal to said comb generating means,

antenna means coupled to said comb signal generating means for transmitting said electromagnetic signals, said antenna means also being capable of receiving at least a portion of said electromagnetic signals which are reflected from an object after said electromagnetic signals have been transmitted from said antenna means,

receiving means coupled to said antenna means for receiving said line spectrum electromagnetic signals from said antenna means, and

timing means coupled to said comb signal generating means and to said receiving means which determines the proximity distance of an object which reflects said electromagnetic signals that have been transmitted from said antenna means for establishing the time that has elapsed between the transmission of one of said groups of said electromagnetic signals and the return of reflected electromagnetic signals from said one group of said electromagnetic signals to said antenna means by initiating a timing action when said one group of said electromagnetic signals is transmitted from said antenna means, and by terminating said timing action when said one group of said electromagnetic signals is received by said antenna means wherein:

said antenna means comprises a single antenna,

said comb generating means comprises step recovery diode means for generating said line spectrum electromagnetic signals, and

wherein said transceiver comprises;

filter means coupled between said antenna means and said step recovery diode means for providing electrical isolation of said step recovery diode means and said antenna means, and

said timing means comprises pulse providing means coupled to said filter means for initiating a pulse upon the initial transmission of said line spectrum electromagnetic signals from said comb generating means and to said receiver means for terminating said pulse upon the receipt of reflected signals from an object in the path of said initial transmission of said line spectrum electromagnetic signals,

wherein said receiver means comprises;

PIN diode means coupled to said antenna means for isolating said antenna from said receiver means,

amplifier means coupled to said PIN diode means for amplifying reflected received signals,

Schottky diode means coupled to the output of said amplifier means and to said pulse producing means for detecting the reflected received signals, and

threshold means coupled to said pulse producing means for determining the distance of said transceiver to an object that reflects said electromagnetic signals.

2. A system comprising a plurality of transceivers for short range electromagnetic proximity detection in a plurality of areas in which at least one transceiver is located to be associated with each area, and wherein each transceiver comprises:

comb signal generating means for generating line spectrum electromagnetic signals in a sequence of groups of said signals,

antenna means coupled to said comb signal generating means for transmitting said electromagnetic signals, said antenna means also being capable of receiving at least a portion of said electromagnetic signals which are reflected from an object after said electromagnetic signals have been transmitted from said antenna means,

receiving means coupled to said antenna means for receiving said line spectrum electromagnetic signals from said antenna means, and

timing means coupled to said comb signal generating means and to said receiving means which determines the proximity distance of an object which reflects said electromagnetic signals that have been transmitted from said antenna means for establishing the time that has elapsed between the transmission of one of said groups of said electromagnetic signals and the return of reflected electromagnetic signals from said one group of said electromagnetic signals to said antenna means by initiating a timing action when said one group of said electromagnetic signals is transmitted from said antenna means, and by terminating said timing action when said one group of said electromagnetic signals is received by said antenna means, and

said system comprises distribution means which comprises;

excitation source means which is coupled to each of said comb generating means of said plurality of transceivers for supplying a periodic excitation signal to said comb generating means, and

receiver identification means coupled to each of said receiver means of said plurality of transceivers for identifying which of said areas contain detected objects wherein each of said transceivers is constructed so that said antenna means comprises a single antenna,

said comb signal generating means comprises step recovery diode means for generating said line spectrum electromagnetic signals, and

said transceiver comprises;

filter means coupled between said antenna means and said step recovery diode means for providing electrical isolation of said step recovery diode means and said antenna means, and

said timing means comprises pulse providing means coupled to said filter means for initiating a pulse upon the initial transmission of said line spectrum electromagnetic signals from said comb generating means and to said receiver means for terminating said pulse upon the receipt of reflected signals from an object in the path of said initial transmission of said line spectrum electromagnetic signals wherein each of said transceivers is constructed so that said receiver means comprises;

PIN diode means coupled to said antenna means for isolating said antenna from said receiver means,

amplifier means coupled to said PIN diode means for isolating said antenna from said receiver means,

amplifier means coupled to said PIN diode means for amplifying reflected received signals,

Schottky diode means coupled to the output of said amplifier means and to said pulse producing means for detecting the reflected receive signal, and

threshold means coupled to said pulse producing means and to said receiver identification means for sensing the distance of each of said transceivers to an object that reflects said electromagnetic signals in the area associated with said transceivers.

3. A system as claimed in claim 2 wherein said areas are used for parking stalls for vehicles, said objects are vehicles, and all of said transceivers are coupled to said distribution means over a bus means that interconnects said comb signal generating means to said excitation source means in said distribution means, and said receiver means to said receiver identification means in said distribution means.