Synchronizaton detection apparatus

#The present invention relates to a synchronization detection device for detecting a synchronization signal from an input signal containing the synchronization signal, and more particularly to a synchronization detection device provided in a receiver that is compliant with the US digital terrestrial broadcasting standard, or the like.

#FIG. 15 is a block diagram illustrating a configuration of a conventional synchronization detection device provided in a digital broadcast receiver. A synchronization detection device 100 illustrated in FIG. 15 includes a field synchronization detection section 101, a pattern match section 102, a count section 103, a backward guard level storage section 104, a forward guard level storage section 105, a synchronization determination section 106, and a synchronization detection signal generation section 107. The synchronization detection device 100 is provided in a digital demodulation system of a receiver compliant with the US digital terrestrial broadcasting standard. The VSB (Vestigial Side Band) scheme is employed as the modulation scheme for the digital demodulation system. The synchronization detection device 100 detects two kinds of synchronization signals (a field synchronization signal and a segment synchronization signal) from an input signal DT having a frame structure compliant with the ATSC (Advanced Television Systems Committee) standard, and outputs a field synchronization detection signal FS and a segment synchronization detection signal SS.

#In FIG. 15, the field synchronization detection section 101 detects a field synchronization signal contained in the input signal DT, and outputs the field synchronization detection signal FS. Elements other than the field synchronization detection section 101 together form a segment synchronization detection section 109. The segment synchronization detection section 109 has a synchronization backward guard function and a synchronization forward guard function. The backward guard function refers to a function of transitioning from a synchronization-unestablished state to a synchronization-established state when a pattern match operation with a synchronization signal succeeds a predetermined number of times (referred to as “backward guard level”) consecutively in a synchronization-unestablished state. The forward guard function refers to a function of transitioning from a synchronization-established state to a synchronization-unestablished state when a pattern match operation with a synchronization signal fails a predetermined number of times (referred to as “forward guard level”) consecutively in a synchronization-established state.

#FIG. 1 is a block diagram illustrating a configuration of a synchronization detection device according to a first embodiment of the present invention.

#FIG. 2 is a block diagram illustrating a configuration of a VSB demodulation system with a synchronization detection device according to first to fifth embodiments of the present invention provided therein.

#FIG. 3 is a block diagram illustrating a configuration of a waveform equalization section of the VSB demodulation system illustrated in FIG. 2.

#(First Embodiment)

#FIG. 1 is a block diagram illustrating a configuration of a synchronization detection device according to the first embodiment of the present invention. A synchronization detection device 110 illustrated in FIG. 1 includes the field synchronization detection section 101, a clock multiplication section 111, a switchable sampling section 112, the pattern match section 102, the count section 103, the backward guard level storage section 104, the forward guard level storage section 105, the synchronization determination section 106, and the synchronization detection signal generation section 107. The synchronization detection device 110 is characterized in that it samples the input signal with a multiplied clock, and switches sample points for sampling the input signal from one to another in a synchronization-unestablished state, for detecting a segment synchronization signal.

#Prior to describing the synchronization detection device 110, a digital demodulation system with this device provided therein will now be described. FIG. 2 is a block diagram illustrating a configuration of a VSB demodulation system with the synchronization detection device 110 provided therein. The VSB demodulation system illustrated in FIG. 2 includes a receiving antenna 10, a tuner 20, a down converter 30, a digital demodulation section 40, and an error correction section 50, and forms part of a receiver compliant with the ATSC standard, which is the US digital terrestrial broadcasting standard. Note that the US digital terrestrial broadcasting standard is described in detail in “ATSC Standard: Digital Television Standard, Revision B”, Doc. A/B53, August 2001.