초록 ▼

In a receiver for the reception of satellite television signals sub-carrier signals carrying, for example, data are recovered from the demodulated television signal and themselves demodulated to provide data outputs. Prior to the second demodulation, each sub-carrier signal is averaged to improve it

In a receiver for the reception of satellite television signals sub-carrier signals carrying, for example, data are recovered from the demodulated television signal and themselves demodulated to provide data outputs. Prior to the second demodulation, each sub-carrier signal is averaged to improve its signal-to-noise, ratio, thereby taking advantage of the relatively small basic bandwidth of the sub-carrier signal to enable satisfactory reception of the signal in poor reception conditions when the received signal is too weak to obtain an acceptable television picture signal. Impulse noise in the received signal is reduced prior to averaging. To avoid intermodulation products being generated by the transmission and reception of several sub-carriers together, direct sequence modulation of the transmitted sub-carriers can be used to spread their power over a wider frequency band. A code lock loop circuit is then used in the receiver to recover the original narrow band signals, which are subsequently averaged to obtain the advantage in signal-to-noise ratio.

대표청구항 ▼

A receiver for receiving a television signal from an earth orbiting satellite, wherein the receiver comprises a first demodulator stage for extracting a video signal and at least one information-carrying sub-carrier signal from the received signal, at least one sub-carrier processing channel coupled

A receiver for receiving a television signal from an earth orbiting satellite, wherein the receiver comprises a first demodulator stage for extracting a video signal and at least one information-carrying sub-carrier signal from the received signal, at least one sub-carrier processing channel coupled to an output of the first demodulator stage and including a signal averaging circuit followed by a second demodulator stage for producing a respective demodulated information signal, and an impulse noise reduction circuit upstream of the signal averaging circuit, whereby said at least one sub-carrier signal can be satisfactorily demodulated when the received signal strength is low such that said video signal is substantially unrecoverable.