Antenna system with a limitable communication area

• US 5,337,066 A
• Filed: 09/14/1992
• Issued: 08/09/1994
• Est. Priority Date: 09/13/1991
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Watanabe, Atsushi, Hirata, Tatsuya, Tokitsu, Naoki
• Primary Examiner(s): Hajec, Donald
• Assistant Examiner(s): LE, HOANGANH T
• Application Number:
  US07/943,429
• Time in Patent Office: 694 Days
• Field of Search: 343/841, 343/793, 343/810, 343/700 MS, 343/813, 343/720, 343/721, 342/1, 342/2, 342/3, 342/4
• US Class Current: 343/841
• CPC Class Codes: H01Q 17/001 for modifying the directional characteristic of an aerial
• CPC Class Codes: H01Q 3/12 using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems

Abstract

An antenna system, comprising an antenna for transmitting a radio wave of a frequency, and a radio wave absorber intercepting and absorbing part of the radio wave to reduce the gain of the antenna. Thereby, the antenna system narrows down the communication area of the radio wave independently of the frequency. The antenna system is applicable to a movable object discriminator using a radio wave.

Claims

1. An antenna system used in a movable object discriminator, comprising:

an antenna for transmitting a radio wave of a predetermined band of frequencies in a direction to produce a communication area of said radio wave in said direction;

means, provided in said direction, for intercepting and absorbing part of said radio wave to reduce a gain of said antenna and thereby narrow down said communication area independently of said frequencies;

means for enabling said intercepting and absorbing means to be pivotable about a pivot at a fixed position to set an angle α

between said intercepting and absorbing means and said antenna to determine said communication area; and

a light transmitter disposed adjacent to said antenna, said light transmitter transmitting a beam of light so that a cross-sectional area of said beam of light exiting from said intercepting and absorbing means indicates a transmission area S of said radio wave.

2. An antenna system, comprising:

an antenna In the form of a board transmitting a radio wave of a frequency from a front surface thereof;

two radio wave absorbers in the form of a board, largest surfaces of said radio wave absorbers being opposite each other through a normal line to a center of said front surface of said antenna, front edges of said radio wave absorbers defining a radio wave transmitting area of said antenna system; and

hinges joining rear edges of said radio wave absorbers to said antenna, said hinges enabling said radio wave transmitting area to be variable.

3. An antenna system comprising:

an antenna in the form of a board transmitting a radio wave of a frequency from a front surface thereof;

two radio wave absorbers in the form of a board, wherein said radio wave absorbers are positioned adjacent to said front surface of said antenna such that the largest surfaces of said radio wave absorbers are opposite each other and generally parallel to a line perpendicular to said front surface of said antenna, front edges of said radio wave absorbers defining a radio wave transmitting area of said antenna system; and

wherein each of said radio wave absorbers are movable transversely to said antenna to change said radio wave transmitting area.

4. The antenna system according to claim 3, further comprising:

two second radio wave absorbers fixedly arranged opposite side edge surfaces of said antenna; and

wherein the rear portions of said first radio wave absorbers have a larger thickness than the front portions of said first radio wave absorbers.

5. An antenna system comprising:

an antenna in the form of a board transmitting a radio wave of a frequency from a front surface thereof;

two radio wave absorber in the form of aboard, wherein said radio wave absorbers are positioned adjacent to said front surface of said antenna and such that the largest surfaces of said radio wave absorbers are opposite each other on either side of a normal line to a center of said front surface of said antenna, front edges of said radio wave absorbers defining a radio wave transmitting area of said antenna system; and

wherein each of said radio wave absorbers is made of a plastic material and rear edges of said radio wave absorbers are fastened to said antenna and wherein a change in the shape of each of said radio wave absorbers also changes said communication area.

6. An antenna system, comprising:

a conductive support;

an antenna for transmitting a radio wave of a frequency, said antenna being fastened to a front portion of said support;

two radio wave absorbers in the form of a board, largest surfaces of said radio wave absorbers being opposite each other through the normal line to the center of the front surface of said antenna, the front edges of said radio wave absorbers defining a radio wave transmitting area of the antenna system;

hinges joining rear edges of said radio wave absorbers to said antenna, said hinges enabling the radio wave transmitting area to be variable; and

a radio interference guard made of a conductive material arranged to opposite side edge surfaces of said support.

7. The antenna system according to claim 6, further comprising:

a housing containing said antenna, said support board, said radio wave absorbers and said hinges.

8. The antenna system according to claim 6, wherein said support is electrically connected to said radio interference guard.

9. The antenna system according to claim 6, further comprising:

a second antenna for transmitting a radio wave of a frequency, said second antenna being fastened to a rear portion of said support;

p1 two second radio wave absorbers in the form of a board, largest surfaces of said second radio wave absorbers being opposite each other through the normal line to the center of the rear surface of said second antenna, the rear edges of said radio wave absorbers defining a second radio wave transmitting area of the antenna system; and

second hinges joining front edges of said second radio wave absorbers to said second antenna, said second hinges enabling the second radio wave transmitting area to be variable.

10. An antenna system used in a movable object discriminator, comprising:

an antenna for transmitting a radio wave of a predetermined band of frequencies in a direction to produce a communication area of said radio wave in said direction;

means, provided in said direction, for intercepting and absorbing part of said radio wave to reduce a gain of said antenna and thereby narrow down said communication area independently of said frequencies; and

means for enabling said intercepting and absorbing means to be pivotable about a pivot at a fixed position to set an angle α

between said intercepting and absorbing means and said antenna to determine said communication area.

11. An antenna system, comprising:

an antenna for transmitting a radio wave of a frequency in a direction to produce a communication area of said radio wave in said direction;

means, provided in said direction, for intercepting and absorbing part of said radio wave to reduce a gain of said antenna and thereby narrow down said communication area toward a desired direction independently of said frequency; and

a light transmitter disposed adjacent to said antenna, said light transmitter transmitting a beam of light toward said desired direction so that a cross-sectional area of the beam of light emitted from said intercepting and absorbing means indicates a transmission area S of said radio wave.