Time sharing FM radar system

Abstract

A time-sharing FM radar system. A plurality of beam radiating and receiving means, an FM signal generating means, a transmitting unit, a receiving unit, and a direction detecting means are configured to minimize power consumption and interference between channels. The beam radiating and receiving means are arranged to radiate partially overlapping beams in space and to receive return beams. The FM signal generating means generates an FM signal. The transmitting unit includes a plurality of transmitting switching circuits each comprised of a plurality of amplifiers. Each amplifier corresponds to one of the beam radiating and receiving means, and is configured to intermittently amplify and distribute a portion of the FM signal generated by the FM signal generating means to its corresponding beam radiating and receiving means. The receiving unit includes a plurality of receiving switching circuits and a single mixer. The receiving switching circuits comprise a plurality of amplifiers each corresponding to one of the beam radiating and receiving means. The amplifiers amplify signals received by the beam radiating and receiving means intermittently and in different timing. The mixer is configured to generate beat signals by mixing received signals output from the receiving switching circuits and a portion of the FM signal generated by said FM signal generating means. The direction detecting means detects a direction to the target based upon a ratio of the amplitude levels of the beat signals.

What is claimed is: 
     
       1. A time-sharing radar system comprising: a plurality of beam radiating and receiving means arranged to radiate partially overlapping beams and to receive return beams, each of said radiating and receiving means having a selected location and direction of radiation, said radiated beams having substantially the same patterns, and said return beams being produced upon a reflection of said radiated beams by a target;   an FM signal generating means for generating an FM signal having a frequency varying with time and having a substantially constant amplitude;   a transmitting unit including a transmitting switching circuit for distributing a portion of said FM signal generated by said FM signal generating means to the beam radiating and receiving means;   a receiving unit including a receiving switching circuit and a single mixer, said receiving switching circuit comprising a plurality of amplifiers, each amplifier corresponding to one of said beam radiating and receiving means, each amplifier intermittently and in a pre-determined sequence amplifying signals received by its corresponding beam radiating and receiving means, and said mixer being capable of generating a plurality of beat signals in different timing by mixing received signals output from said receiving switching circuit, with an FM signal related to said FM signal generated by said FM signal generating means;   a direction detecting means for detecting a direction to the target based on a plurality of amplitude levels of said beat signals output from said mixer and the locations and directions of said beam radiating and receiving means; and   a range detecting means for detecting a range to the target based on a frequency of said beat signal output from said mixer.   
     
     
       2. A time-sharing radar system according to claim 1 wherein; said a portion of said FM signal being supplied to said transmitting switching circuit is delayed by predetermined amount in relation to said portion of said FM signal which is supplied to said mixer.   
     
     
       3. A time-sharing radar system according to claim 2 wherein; said direction detecting means and said range detecting means both include an analog-to-digital converter for converting said beat signals output from said mixer from an analog format to a digital format, and a Fast Fourrier Transformer for transforming said converted digital signals to frequency spectra.   
     
     
       4. A time-sharing radar system according to claim 3, wherein said transmitting switching circuit comprises a plurality of amplifiers, each of said amplifiers corresponding to one of said beam radiating and receiving means, each of said amplifiers intermittently and in a predetermined sequence amplifying and distributing said portion of said FM signal which is supplied to said mixer; and   wherein said amplifiers comprising said transmitting switching circuit and said receiving circuit comprise: a field effect transistor having a gate terminal for receiving a signal to be amplified, a source terminal coupled to ground and a drain terminal used as a bias input terminal and FM signal output terminal; and   a bias controlling circuit for controlling said field effect transistor by intermittently raising a bias voltage supplied to said field effect transistor.     
     
     
       5. The time-sharing radar system of claim 1 wherein; each of said amplifiers of said receiving switching circuit intermittently amplifies signals received by its corresponding beam radiating and receiving means during a period in which beams are radiated from both said corresponding beam radiating and receiving means and a beam radiating and receiving means adjacent to said corresponding radiating and receiving means.   
     
     
       6. A time-sharing radar system according to claim 5 wherein; said a portion of said FM signal being supplied to said transmitting switching circuit is delayed by predetermined amount in relation to said portion of said FM signal which is supplied to said mixer.   
     
     
       7. A time-sharing radar system according to claim 6 wherein; said direction detecting means and said range detecting means both include an analog-to-digital converter for converting said beat signals output from said mixer from an analog format to a digital format, and a Fast Fourrier Transformer for transforming said converted digital signals to frequency spectra.   
     
     
       8. A time-sharing radar system according to claim 7, wherein said transmitting switching circuit comprises a plurality of amplifiers, each of said amplifiers corresponding to one of said beam radiating and receiving means, each of said amplifiers intermittently and in a predetermined sequence amplifying and distributing said portion of said FM signal which is supplied to said mixer; and   wherein said amplifiers comprising said transmitting switching circuit and said receiving circuit comprise: a field effect transistor having a gate terminal for receiving a signal to be amplified, a source terminal coupled to ground and a drain terminal used as a bias input terminal and FM signal output terminal; and   a bias controlling circuit for controlling said field effect transistor by intermittently raising a bias voltage supplied to said field effect transistor.     
     
     
       9. A time-sharing radar system according to claim 5 wherein; at least one of said amplifiers of said receiving switching circuit amplifies signals received by its corresponding beam radiating and receiving means intermittently during a period in which a beam is not radiated from any of said beam radiating and receiving means; and   said direction detecting means further includes means for storing said received signals as noise output from said amplifiers during said period and means for subtracting said noise from said beat signals.   
     
     
       10. A time-sharing radar system according to claim 9 wherein; said a portion of said FM signal being supplied to said transmitting switching circuit is delayed by predetermined amount in relation to said portion of said FM signal which is supplied to said mixer.   
     
     
       11. A time-sharing radar system according to claim 10 wherein; said direction detecting means and said range detecting means both include an analog-to-digital converter for converting said beat signals output from said mixer from an analog format to a digital format, and a Fast Fourrier Transformer for transforming said converted digital signals to frequency spectra.   
     
     
       12. A time-sharing radar system according to claim 11, wherein said transmitting switching circuit comprises a plurality of amplifiers, each of said amplifiers corresponding to one of said beam radiating and receiving means, each of said amplifiers intermittently and in a predetermined sequence amplifying and distributing said portion of said FM signal which is supplied to said mixer; and   wherein said amplifiers comprising said transmitting switching circuit and said receiving circuit comprise: a field effect transistor having a gate terminal for receiving a signal to be amplified, a source terminal coupled to ground and a drain terminal used as a bias input terminal and FM signal output terminal; and   a bias controlling circuit for controlling said field effect transistor by intermittently raising a bias voltage supplied to said field effect transistor.     
     
     
       13. A time-sharing radar system comprising: a plurality of beam radiating and receiving means having a selected location and direction, said beam radiating and receiving means being configured to radiate partially overlapping beams and to receive return beams, said radiated beams having substantially the same patterns, said return beams being produced by reflection of said radiated beams by a target;   an FM signal generating means for generating an FM signal having a frequency varying with time and having a substantially constant amplitude;   a transmitting unit including a transmitting switching circuit comprising a plurality of amplifiers, each of said amplifiers corresponding to one of said beam radiating and receiving means, and each of said amplifiers intermittently amplifying and distributing a portion of said FM signal generated by said FM signal generating means to its corresponding beam radiating and receiving means through frequency multipliers;   a receiving unit including a local switching circuit and a mixer, said local switching circuit comprising a plurality of amplifiers, each amplifier corresponding to one of said beam radiating and receiving means, said amplifiers intermittently amplifying a portion of said FM signal generated by said FM signal generating means, said mixer being configured to generate beat signals by mixing signals received by each of said corresponding beam radiating and receiving means with an FM signal related to said FM signal output from amplifiers;   a direction detecting means for detecting a direction to the target based upon a plurality of amplitude levels of said beat signals output from said mixer and the locations of said beam radiating and receiving means;   a range detecting means for detecting a range to the target based upon a frequency of at least one of said beat signals output from said mixer.   
     
     
       14. A time-sharing radar system according to claim 13 wherein; each of said amplifiers comprising both of said transmitting switching circuit and receiving circuit comprises: a field effect transistor having a gate terminal for receiving a signal to be amplified, a source terminal coupled to ground and a drain terminal used as a bias input terminal and an FM signal output terminal; and   a bias controlling circuit for controlling said field effect transistor by intermittently raising a bias voltage supplied to said field effect transistor. .Iadd.     
     
     
       15.  A method for detecting a distance and direction to an object, said method comprising the steps of: generating a frequency modulated (FM) signal by modulating a carrier signal with a modulation signal having a frequency varying with time;   providing the FM signal to an amplifier circuit coupled to a transmitting and receiving antenna system to cause the antenna system to radiate a beam;   allowing the beam radiated by the antenna system to be reflected by an object and received by the antenna system, the reflected beam comprising a return beam and the antenna system including receiving antennas, a plurality of which can receive said return beam, and the plurality of receiving antennas each generating a signal upon receiving a return beam;   amplifying the signals generated by the plurality of receiving antennas and providing the amplified signals to a mixer circuit in a time varying manner to cause the signals generated by the plurality of receiving antennas to be mixed with the FM signal to produce a sequence of beat signals;   determining a distance to the object based upon a frequency of the beat signals; and   determining a direction to the object based upon an amplitude of the beat signals..Iaddend..Iadd.16. The method of claim 15, wherein the transmitting and receiving antenna system includes a transmitting antenna   
     
     
        which comprises one of said receiving antennas..Iaddend..Iadd.17.  The method of claim 15, wherein the transmitting and receiving antenna system includes a transmitting antenna which comprises one of said plurality of receiving antennas..Iaddend..Iadd.18. A frequency modulated (FM) radar system for detecting a distance and direction to an object, the FM radar system comprising: a FM signal generator for generating a frequency modulated (FM) signal by modulating a carrier signal with a modulation signal having a frequency varying with time;   an amplifier coupled to the FM signal generator and to a transmitting and receiving antenna system for amplifying the FM signal generated by the FM signal generator and providing amplified signals to the transmitting and receiving antenna system for transmission toward an object to provide return beams;   the antenna system including a plurality of receiving antennas, each of the receiving antennas being capable of generating a signal corresponding to a received return beam, each return beam comprising a beam originally transmitted by the antenna system as reflected by an object;   a plurality of amplifiers respectively coupled to the receiving antennas for amplifying the signals corresponding to the received return beams;   an amplifier and mixer circuit for amplifying and mixing in a time varying manner the signals corresponding to the received return beams with the FM signal generated by the FM signal generator to sequentially produce a plurality of beat signals;   a timing control circuit for determining when each of the signals corresponding to the received return beam will be mixed with the signals generated by the FM signal generator; and   a processing circuit for determining a distance to the object based upon a frequency of the beat signals and determining a direction to the object   
     
     
        based upon an amplitude of the beat signals..Iaddend..Iadd.19.  The FMCW radar system of claim 18, wherein the amplified FM signal is transmitted by one of said plurality of receiving antennas..Iaddend..Iadd.20. A frequency modulated (FM) radar system for detecting a distance and direction to an object, the FM radar system comprising: a FM signal generator for generating a frequency modulated (FM) signal by modulating a carrier signal with a modulation signal having a frequency varying with time;   an amplifier coupled to the FM signal generator and to a selected one of a plurality of transceiving antennas, the amplifier being capable of amplifying the FM signal generated by the FM signal generator and providing an amplified signal to the selected transceiving antenna;   each of the transceiving antennas being capable of generating a signal corresponding to a received return beam, the return beam comprising a beam originally transmitted by the selected transceiving antenna and reflected by an object;   a plurality of amplifier circuits coupled, respectively, to the transceiving antennas for amplifying the signals corresponding to the received return beam;   a mixer circuit for mixing in a time varying manner the signals corresponding to the received return beam with the FM signal generated by the FM signal generator to produce a sequence of beat signals;   a timing control circuit for determining when each of the signals corresponding to the received return beam will be mixed with the signal generated by the FM signal generator; and   a processing circuit for determining a distance to the object based upon a frequency of the beat signals and determining a direction to the object   
     
     
        based upon an amplitude of the beat signals..Iaddend..Iadd.21.  A mixer and switching circuit for use in a frequency modulated (FM) radar system, said circuit comprising: a plurality of amplifier circuits for amplifying a plurality of signals received from a respective plurality of antennas to produce a respective plurality of amplified signals;   a mixer circuit for mixing said amplified signals with a signal generated by a FM signal generator circuit; and   a timing control circuit for determining when each of said amplified signals will be mixed with said signal generated by said FM signal generator circuit to cause said mixer circuit to produce in sequential periods a plurality of beat signals corresponding, respectively, to said plurality of amplified signals..Iaddend..Iadd.22. A frequency modulated (FM) radar system comprising:   a FM signal generator circuit;   a power divider circuit coupled to said FM signal generator circuit;   a delay circuit coupled to a first output of said power divider circuit;   a first plurality of amplifier circuits coupled to said delay circuit;   a plurality of circulator circuits coupled respectively to said first plurality of amplifier circuits;   a plurality of antennas coupled respectively to said circulator circuits;   a second plurality of amplifier circuits coupled respectively to said circulator circuits;   a mixer circuit coupled to a second output of said power divider circuit and to respective outputs of said second plurality of amplifier circuits; and   a timing control circuit coupled to said first plurality of amplifier circuits and to said second plurality of amplifier circuits..Iaddend..Iadd.23. The frequency modulated (FM) radar system of claim 22 further comprising:   an analog-to-digital converter coupled to said mixer circuit; and   a processing circuit coupled to said analog-to-digital   
     
     
        converter..Iaddend..Iadd.24.  A method of operating a radar system to detect a direction and distance to an object located within a selected range of detection of said radar system, said method comprising the steps of: arranging a plurality of transceiving antennas to radiate beams in and receive beams from a plurality of distinct directions within the selected range of detection;   causing the antennas to radiate beams, respectively, within sequential beam radiation periods;   allowing the antennas to receive return beams, each return beam comprising a beam originally transmitted by one of the antennas and reflected by an object, and each antenna generating a signal upon receiving a return beam;   within each beam radiation period enabling in a sequential manner the signals generated by a selected number of adjacent antennas to be mixed with a signal provided by a FM signal generator circuit to produce beat signals;   determining a direction to said object based upon an amplitude of the produced beat signals; and   determining a direction to an object based upon a frequency of the produced   
     
     
        beat signals..Iaddend..Iadd.25.  The method of claim 24, wherein the selected number of adjacent antennas is two, and wherein one antenna of the selected number of antennas comprises the antenna which was caused to radiate a beam during the given beam radiation period..Iaddend.