Title: Method and apparatus for reducing oscillator noise by noise-feedforward
Application Number: 00805671 Application Date: 2000.03.28
Publication Number: 1345482 Publication Date: 2002.04.17
Approval Pub. Date: 2005.10.26 Granted Pub. Date: 2005.10.26
International Classifi-cation: H03L7/00;H03L7/23;H03C3/09;H04B1/04
Applicant(s) Name: Ericsson Inc. Address:
Inventor(s) Name: P.W. Dent
Attorney & Agent: wang yue
Abstract:
    A circuit for reducing phase noise in a transmitted radio signal includes a first phase-locked loop (12) circuit including a first controlled oscillator (18) generating a first output signal (20) at a first desired frequency, and a first phase comparator (32) developing a first phase error signal (34) to control the first controlled oscillator, the first error signal representative of phase differences between the first output signal and the first desired frequency. A second phase-locked loop circuit (16) includes a second controlled oscillator (50) generating a second output signal at a desired frequency of transmission related to the first desired frequency, and a second phase comparator (56) developing a second phase error signal (58) representative of phase differences between the first output signal and the desired frequency of transmission. A summer (74) combines the first and second error signals to control the second controlled oscillator (18) to thereby reduce, or cancel, phase noise generated by the first controlled oscillator in the second output signal transmitted as a radio signal at the desired frequency of transmission.
Time: 17