Radio transceiver including an antenna switching circuit capable of changing reception sensitivity

• US 4,853,972 A
• Filed: 04/07/1987
• Issued: 08/01/1989
• Est. Priority Date: 04/09/1986
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Ueda, Hideki, Babano, Sotoaki
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Smith, Ralph E.
• Application Number:
  US07/035,321
• Time in Patent Office: 847 Days
• Field of Search: 455/78, 455/79, 455/82, 455/83, 455/195, 455/254, 370/32
• US Class Current: 455/83
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 1/44 Transmit/receive switching

Abstract

A radio transceiver having a plurality of switching means such that the reception sensitivity and transmission level of the transceiver can be changed. An antenna switching circuit selectively couples the transmitter or receiver to the antenna in response to a transmit or receive mode. A first switch connects the antenna switching circuit to one of a plurality of different potential levels to control the switching of the antenna switching circuit. First and second potential levels are used to achieve first and second receive modes having different receive sensitivities, and a third potential level is used to achieve a transmit mode. A second switch selectively activates one of a first transmitter circuit providing transmission signals, a second transmitter circuit providing reduced transmission signals, and a receiver. A control circuit controls the switching of the first and second switch.

Claims

1. A radio transceiver comprising an antenna, a transmitter, a receiver, an antenna switching circuit including switching diodes for coupling said transmitter and said receiver to said antenna in response to a transmit mode and a receive mode, respectively, and means for changing the resistances of said switching diodes in response to another receive mode to reduce the level of a received signal supplied from said antenna to said receiver.

2. A radio transceiver comprising an antenna, a transmitter, a receiver and an antenna switching circuit including first and second switching diodes, first means for giving a high resistance to said switching diodes by providing a first bias to said switching diodes in a receive mode to couple said antenna to said receiver, second means for giving a low resistance to said switching diodes by providing a second bias to said switching diodes in a transmit mode to couple said transmitter to said antenna, and third means for giving a resistance lying between said high and low resistances to said diodes by providing a third bias to said switching diode in another receive mode.

3. A radio transceiver as claimed in claim 2, comprising means for selecting one of said first and third means in response to a control signal.

4. A radio transceiver as claimed in claim 3, wherein said control signal comprises a signal representative of the intensity of a radio signal received in one of said receive modes.

5. A radio transceiver as claimed in claim 3, comprising key board means for generating said control signal.

6. A radio transceiver as claimed in claim 2, comprising means for varying the output level of said transmitter in response to a control signal.

7. A radio transceiver as claimed in claim 6, comprising key board means for generating said control signal.

8. A radio receiver as claimed in claim 6, comprising means for selecting one of said first and third means in response to another control signal representative of the intensity of a received radio signal.

9. A radio transceiver including:

an antenna,

a transmitter,

a receiver, and

an antenna switching circuit for selectively coupling said transmitter and said receiver to said antenna in response to a transmit mode and a receive mode, respectively the antenna switching circuit including;

a first diode coupled between said antenna and said transmitter,

a second diode and an inductor connected in series between a point of fixed potential and the junction of said antenna and said first diode, and

means for coupling said receiver to the junction of said second diode and said inductor, and

means for changing the resistances of said first and second diodes in response to a control signal to couple said antenna to said transmitter in a transmit mode, to couple said antenna to said receiver in first and second receive modes, a receive signal being supplied from said antenna to said receiver in said first receive mode, and a received signal having a reduced level being supplied to said receiver in said second receive mode.

10. A radio transceiver comprising:

an antenna;

a transmitter;

a receiver;

an antenna switching circuit for selectively coupling said transmitter and said receiver to said antenna in response to a transmit mode respectively and a receive mode, respectively;

first switching means for connecting said antenna switching circuit to one of a first, second and third potential, said first potential for causing said antenna switching circuit to selectively couple said antenna to said receiver such that a received signal can be applied to said receiver in a first receive mode, said second potential for causing said antenna switching circuit to selectively couple said antenna to said receiver such that a received signal of reduced level can be applied to said receiver in a second receive mode, and said third potential for causing said antenna switching circuit to selectively couple said antenna to said transceiver in a transmit mode.

11. A radio transceiver as claimed in claim 10, wherein said transmitter produces one of a plurality of transmission signals of a plurality of levels in response to a control signal.