Tunable phase shifer with a control signal generator responsive to DC offset in a mixed signal

• US 7,164,329 B2
• Filed: 04/10/2002
• Issued: 01/16/2007
• Est. Priority Date: 04/11/2001
• Status: Expired due to Term

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Wireless Corporation (Kyocera Corporation)
• Inventors: Toncich, Stanley S., Wallace, Raymond Curtis
• Primary Examiner(s): LEE, BENNY T
• Application Number:
  US10/120,938
• Publication Number:
  US 20030194984A1
• Time in Patent Office: 1,742 Days
• Field of Search: 455/283, 455/296, 455/323, 455/324, 455/313, 455/318, 455/319, 327/231, 327/233, 327/234, 333/156, 333/161, 333/164, 333/138, 333/139
• US Class Current: 333/139
• CPC Class Codes: H03H 7/0123 comprising distributed impedance elements together with lumped impedance elements
• CPC Class Codes: H03H 7/0153 Electrical filters; Controlling thereof
• CPC Class Codes: H03H 7/20 Two-port phase shifters providing an adjustable phase shift
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

The present invention provides a phase shifting filter and a phase compensating direct downconversion receiver. A DC offset detector detects a DC offset in a received baseband signal and provides a feedback signal. A tunable filter phase shifts a local oscillator signal responsive to the feedback signal. The phase-shifted local oscillator signal is used to directly downconvert a received RF signal, whereby DC offset in the resulting baseband signal is reduced.

Claims

1. An electromagnetic signal phase shifter comprising:

an input port configured to receive reference signal from a reference oscillator;

a control signal generator configured to generate a control signal, the control signal generator responsive to a DC offset in a mixed signal;

a tunable filter coupled to the control signal generator and to the input port, the tunable filter comprising a first impedance element and a second impedance element coupled to the first impedance element, the first impedance element comprising a first ferroelectric component, the first and second impedance elements configured to shift a phase of the reference signal; and

an output port coupled to the tunable filter, the output port configured to transmit the phase-shifted reference signal to a mixer.

2. The electromagnetic signal phase shifter of claim 1, wherein the first ferroelectric component comprises a first ferroelectric capacitor.

3. The electromagnetic signal phase shifter of claim 2, wherein the first ferroelectric capacitor comprises a gap capacitor.

4. The electromagnetic signal phase shifter of claim 2, wherein the first ferroelectric capacitor comprises an overlay capacitor.

5. The electromagnetic signal phase shifter of claim 1, further comprising a third impedance element comprising a second ferroelectric component.

6. The electromagnetic signal phase shifter of claim 5, wherein the first and second ferroelectric components comprise first and second ferroelectric capacitors respectively.

7. The electromagnetic signal phase shifter of claim 6, wherein the first and second ferroelectric capacitors comprise respective gap capacitors.

8. The electromagnetic signal phase shifter of claim 6, wherein the first and second ferroelectric capacitors comprise respective overlay capacitors.

9. The electromagnetic signal phase shifter of claim 1, wherein the control signal generator comprises a feedback network and a DC offset detector coupled to the feedback network.

10. The electromagnetic signal phase shifter of claim 9, wherein the feedback network comprises an inverting operational amplifier coupled to a scaling system.

11. The electromagnetic signal phase shifter of claim 9, wherein the feedback network comprises a state machine.

12. A method of shifting the phase of an electromagnetic signal:

receiving a reference signal from a reference oscillator;

generating a control signal via a feedback network, the control signal responsive to a DC offset in a mixed signal;

tuning a ferroelectric component in a tunable filter to shift the phase of the reference signal responsive to the control signal; and

transmitting the phase-shifted reference signal to a mixer.