Digital satellite broadcasting receiver for changing PLL loop band-width during center controlling

Abstract

A digital satellite broadcasting receiver includes: a channel selecting circuit having a channel selecting PLL; a carrier recovery circuit receiving an output from the channel selecting circuit and having a carrier recovery PLL; a switching circuit for switching a loop bandwidth of the channel selecting PLL; and a control circuit for controlling the switching circuit such that the loop bandwidth of the channel selecting PLL circuit is made narrower than in a normal receiving state and than at a channel switching, at the time of centering. Instead of channel selecting PLL, the loop bandwidth of the carrier recovery PLL may be made wider temporarily.

Description

technical field [0001] The present invention relates to a digital satellite broadcasting receiver for receiving, demodulating, signal-processing and outputting broadcasting signals from satellites, etc., and particularly relates to carrier locking of a PLL circuit for carrier regeneration which is less susceptible to noise and less likely to occur during center adjustment A digital satellite radio receiver that lost its lock. Background technique [0002] International Patent Application Publication No. WO 96 / 39745A discloses a digital satellite broadcasting receiver, wherein a tuner, a PLL (Phase Locked Loop) circuit, and a QPSK demodulator are disclosed. The US patent No. US 5272452A discloses a PLL with a variable bandwidth loop filter, in which the switch 9 is used to switch the loop bandwidth of the PLL circuit; when the switch control signal makes the switch closed, the loop filter The bandwidth of the device is narrowed. [0003] In the digital satellite broadcast r...

AI Technical Summary

Problems solved by technology

However, during the center adjustment, if the channel selection frequency of the channel selection PLL is moved step by step, the carrier regeneration PLL of the subsequent QPSK demodulator cannot keep up with the channel selection PLL, and as a result, the carrier lock is lost

Conversely, if the loop bandwidth of the subsequent carrier regeneration PLL is increased, the carrier regeneration PLL can easily keep up with the station selection PLL, but in normal reception, the characteristics of the signal to noise deteriorate, and the bit error rate deteriorates. Propensity

Images