Tunable phase shifter and applications for same
AssigneeKyocera Wireless Corp.
InventorsStanley S. Toncich, Raymond Curtis Wallace
Life of this patent
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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.
Claims12
An electromagnetic signal phase shifter comprising:
- a control signal generator for generating a control signal;
- a first impedance element comprising a ferroelectric component;
- a control line coupled between the control signal generator and the first impedance element;
- a second impedance element coupled to the first impedance element, the first and second impedance elements configured to shift a phase of an electromagnetic signal applied to either the first impedance element or the second impedance element.
A direct downconversion receiver, comprising:
- a local oscillator configured to produce a local oscillator signal;
- a mixer coupled to the local oscillator and to an RF signal input and configured to mix the local oscillator signal and the RF signal to directly downconvert the RF signal to a baseband signal;
- a DC offset detector configured to detect a DC offset of a baseband signal and output a DC offset signal indicative of the DC offset;
- a feedback network coupled to the DC offset detector and configured to receive the DC offset signal and output a control signal;
- a tunable phase shifting filter coupled to the feedback network and coupled between the local oscillator and the mixer for shifting the phase of the local oscillator signal and configured to receive the control signal and to vary the phase shifting, responsive to the control signal;
- wherein the feedback network is configured to reduce the DC offset by shifting the phase of the local oscillator signal, responsive to the DC offset signal.
A method of reducing DC offset, comprising:
- mixing an RF signal with a phase-shifted local oscillator signal to produce a directly downconverted baseband signal;
- detecting a DC offset in the directly downconverted baseband signal;
- and
- adjusting the phase-shift in the phase-shifted local oscillator signal to reduce the detected DC offset.
Dependencies are inferred from the claim text.