Digital frequency phase locked loop (FPLL) for vestigial sideband (VSB) modulation transmission system

摘要

In a digital frequency phase locked loop (FPLL) for a grand alliance (GA) HDTV receiver using a vestigial sideband (VSB) modulation transmission system, the digital FPLL for a VSB transmission system having a VCO and a plurality of NTSC carrier eliminating filters for eliminating interference of NTSC adjacent channels includes a filter for eliminating high-frequency components by converting a digital signal output from one of the plurality of NTSC carrier eliminating filters, a delay for delaying the high-frequency-component-eliminated signal by a predetermined width so that its frequency-versus-phase characteristics are changed linearly, symbol inverter for inverting the symbol of the digital signal output from another of the plurality of NTSC-carrier eliminating filters, a switch for selectively outputting the symbol-inverted signal and the digital signal output from another filter, a second filter for limiting the selectively output signal to a predetermined frequency band, a digital-to-analog (D/A) converter for converting the band-limited-digital signal into an analog signal. The result is that the frequency-versus-phase characteristics of the filter is linear, and the size of digital ASICs gates are remarkably reduced.