Method and apparatus for suppressing spurious third-order responses in transceivers

• US 5,590,411 A
• Filed: 01/10/1995
• Issued: 12/31/1996
• Est. Priority Date: 01/10/1995
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Sroka, Peter, Harrison, Peter D.
• Primary Examiner(s): Pham, Chi H.
• Application Number:
  US08/371,027
• Time in Patent Office: 721 Days
• Field of Search: 455/24, 455/69, 455/78, 455/79, 455/80, 455/84, 455/295, 455/296, 455/311, 455/239.1, 455/250.1, 455/283, 455/289, 455/291, 455/293, 370/32, 370/32.1
• US Class Current: 455/78
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input

Abstract

Apparatus and a method for inhibiting spurious responses in the receiver stage of a radio telephone are disclosed. A detector detects the transmission of an RF signal from the transceiver and sends a control signal indicative of such transmission to a linearity controller. The linearity controller is coupled to non-linear devices in the receiver stage of a transceiver and varies the linearity of the non-linear devices in accordance with the control signal. Preferably, the linearity is varied by increasing the bias current or voltage for the non-linear devices when the control signal indicates transmission of an RF signal.

Claims

1. Apparatus for inhibiting spurious responses in a receiver section of a transceiver, said receiver section having a non-linear device, said apparatus comprising:

detection means for detecting transmission of a RF signal from the transceiver and outputting a control signal indicative of said transmission; and

linearity control means connected to said detection means and to the non-linear device so as to vary the linearity of said non-linear device in accordance with said control signal.

3. Apparatus according to claim 1, wherein said linearity is varied by varying a bias current for said non-linear device in accordance with said control signal.

4. Apparatus according to claim 1, wherein said linearity is varied by varying a bias voltage for said non-linear device in accordance with said control signal.

5. Apparatus according to claim 1, wherein said linearity is varied by varying a drive power of a local oscillator signal for said non-linear device in accordance with said control signal.

6. Apparatus according to claim 3, wherein said linearity control means comprises a selectable resistance disposed in series with said bias current.

7. Apparatus according to claim 6, wherein said selectable resistance comprises a first resistor and a second resistor switchably coupled in parallel with said first resistor.

8. Apparatus according to claim 6, wherein said selectable resistance comprises a first resistor switchably coupled in parallel with a short circuit to ground.

2. A transceiver comprising:

a transmitting means for transmitting a first RF frequency;

a receiving means for receiving a second RF frequency; and

a duplexer coupled to the transmitting and receiving means so as to inhibit ingress of said first RF frequency into the receiving means, said receiving means including a non-linear device for operating on the second RF frequency, said non-linear device being adapted to provide greater linearity during transmission of said first RF frequency from the transmitting means.

9. A method for inhibiting spurious responses in a receiver for a transceiver, comprising the steps of:

detecting when signals are transmitted from said transceiver; and

increasing the linearity of a non-linear device disposed in the receiver when signals are transmitted from said transceiver.

10. A method according to claim 9, wherein the bias current for the non-linear device is increased during transmission of signals from said transceiver.

11. A method according to claim 9, wherein a bias voltage for the non-linear device is increased during transmission of signals from said transceiver.

12. A method according to claim 9, wherein drive power of a local oscillator signal for the non-linear device is increased during transmission of signals from said transceiver.

13. A method according to claim 10, wherein the bias current is increased by reducing a resistance coupled in series with the bias current.