Phase locked loop with down-conversion in feedback path

Details Phase locked loop with down-conversion in feedback path Phase locked loop with down-conversion in feedback path

1997-12-18

2000-01-25

Mis, David

Modulators

Frequency modulator

Including stabilization or alternatively distortion, noise...

332100, 332103, 332120, 332144, 332145, 332151, 331 23, 375300, 375302, 375306, 375308, 455108, 455113, H03C 300, H04L 2704, H04L 2712, H04L 2720

Patent

active

06018275&

ABSTRACT:
A transmitter and a phase locked loop (30) for a transmitter are disclosed. The phase locked loop (30) upconverts the frequency of a baseband signal to a frequency for radio transmission. As well as the usual components, the phase locked loop (30) comprises a modulator (39) for modulating a baseband signal (f.sub.bb) onto a carrier (f.sub.ref /R) and forwarding the resultant modulated signal (f.sub.c) to one of the inputs of the phase detector (33). It also comprises a low pass filter (38) in its forward path between the phase detector (33) and the voltage controlled oscillator (34) for passing signals having baseband signal frequencies. A mixer (35) and main frequency divider (36) are provided in the feedback path to downconvert the transmit signal (f.sub.tx). This low division eliminates large amounts of multiplicative noise within the loop bandwidth, and therefore enables a large loop bandwidth to be used. Consequently, the settling time of the phase locked loop is improved.

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