RF synthesizer and RF transmitter or receiver incorporating the synthesizer

Abstract

An RF (radio frequency) synthesizer (200) includes a VCO (voltage controlled oscillator) (120) operable to provide an output signal at a desired frequency, a phase locked loop (130) including (i) the VCO; (ii) a frequency divider (114) operable to receive an output signal of the VCO and to provide a feedback signal which is divided in frequency relative to the output signal of the VCO; and (iii) a phase frequency detector (110) operable to receive the feedback signal produced by the VCO and to compare a phase and frequency of the feedback signal with the phase and frequency of a reference signal; and is characterised by (iv) a further control loop (230) inside the phase locked loop (130); and (v) a phase rotator (205) connected to an output of the VCO and operable to equalise a phase error of an output signal produced by the VCO, the further control loop being connected to the phase rotator to provide a control signal to the phase rotator. The synthesizer may beneficially include an integrated circuit which incorporates at least part of the VCO, the phase locked loop and the further control loop. Also described is a RF transmitter or receiver, e.g. for use in a base transceiver station, which incorporates the synthesizer.

Description

technical field [0001] The present invention relates to an RF (Radio Frequency) synthesizer and an RF transmitter or receiver incorporating the RF synthesizer. In particular, the present invention relates to an RF synthesizer for generating a stable RF signal, including a VCO (Voltage Controlled Oscillator) usable in a wireless transmitter or receiver. Background technique [0002] The carrier frequency signal in an RF communication transmitter is typically generated by a frequency synthesizer comprising a VCO coupled with a phase locked loop (PLL). A phase locked loop comprising this VCO provides a suitably stable output signal at a precisely defined frequency. The VCO typically employs a resonator section that provides oscillation within a given frequency band including the frequency of the output signal, a tuning section that employs, for example, one or more voltage-controlled device, such as a varactor diode, to tune the output frequency based on the input control vol...

AI Technical Summary

Problems solved by technology

The problem of these spurious peaks is exacerbated when the VCO operating frequency increases

Images