Integrated image reject mixer
First Claim
1. An image reject mixer comprising:
- a local oscillator for producing a local oscillator signal;
a local oscillator phase shifting network, coupled to the local oscillator, for producing an in-phase local oscillator signal and a quadrature local oscillator signal from the local oscillator signal;
a phase detector, coupled to the local oscillator phase shifting network, for examining a phase of the in-phase local oscillator signal and a phase of the quadrature local oscillator signal and producing a control signal for adjusting the phase of the in-phase local oscillator signal and the phase of the quadrature local oscillator signal; and
an intermediate frequency phase shifting network, coupled to the phase detector, for adjusting a phase of an in-phase intermediate frequency signal and a phase of a quadrature intermediate frequency signal in response to the control signal.
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Accused Products
Abstract
An integrated image reject mixer (150) generates precise quadrature components using highly matched local-oscillator (LO) path and intermediate frequency (IF) path resistor-capacitor (RC) phase shifting networks (131, 138). Because the LO signal from a local oscillator (127) has a constant amplitude, a phase detector (136) feedback loop easily maintains an accurate ninety-degree phase difference between the quadrature LO signals (122, 124) from the LO path phase shifting network (131). Because the two phase shifting networks are matched, the feedback control signal (137) from the phase detector (136) can also be used to maintain an accurate ninety-degree phase difference between the quadrature IF signals (123, 128) from the IF path phase shifting network (138) despite the dynamically-varying amplitude of the IF signal. Thus, this image reject mixer uses only components that may be easily integrated into an integrated circuit.
204 Citations
21 Claims
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1. An image reject mixer comprising:
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a local oscillator for producing a local oscillator signal; a local oscillator phase shifting network, coupled to the local oscillator, for producing an in-phase local oscillator signal and a quadrature local oscillator signal from the local oscillator signal; a phase detector, coupled to the local oscillator phase shifting network, for examining a phase of the in-phase local oscillator signal and a phase of the quadrature local oscillator signal and producing a control signal for adjusting the phase of the in-phase local oscillator signal and the phase of the quadrature local oscillator signal; and an intermediate frequency phase shifting network, coupled to the phase detector, for adjusting a phase of an in-phase intermediate frequency signal and a phase of a quadrature intermediate frequency signal in response to the control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A radiotelephone comprising:
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A) an antenna; B) an image reject mixer integrated onto a single integrated circuit, coupled to the antenna, having; 1) a local oscillator for producing a local oscillator signal; 2) a local oscillator phase shifting network, coupled to the local oscillator, for producing an in-phase local oscillator signal and a quadrature local oscillator signal from the local oscillator signal including; a) a first capacitor, coupled to the local oscillator; b) a first resistor, coupled to the local oscillator; c) a second capacitor, coupled to the first resistor; and d) a second resistor, coupled to the first capacitor and the second capacitor; 3) a phase detector, coupled to the local oscillator phase shifting network, for examining a phase of the in-phase local oscillator signal and a phase of the quadrature local oscillator signal and generating a control signal for adjusting the phase of the in-phase local oscillator signal and the phase of the quadrature local oscillator signal; and 4) an intermediate frequency phase shift network, coupled to the phase detector, for adjusting a phase of an in-phase intermediate frequency signal and a phase of a quadrature intermediate frequency signal in response to the control signal including; a) a first capacitor; b) a first resistor, coupled to the first capacitor; c) a second capacitor, coupled to the first resistor; and d) a second resistor, coupled to the first capacitor and the second capacitor; C) an audio speaker, coupled to the image reject mixer.
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21. A method for image reject mixing comprising the steps of:
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producing a local oscillator signal; creating an in-phase local oscillator signal and a quadrature local oscillator signal from the local oscillator signal; examining a phase of the in-phase local oscillator signal and a phase of the quadrature local oscillator signal and generating a control signal for adjusting the phase of the in-phase local oscillator signal in relation to the phase of the quadrature local oscillator signal; and adjusting a phase of an in-phase intermediate frequency signal in relation to a phase of a quadrature intermediate frequency signal using the control signal.
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Specification