Abstract: A front end for a radio frequency tuner, for example for connection to a cable distribution network, including an input connected to a signal path comprising an LNA connected via an AGC stage to a signal splitter. The input path has a bandwidth sufficiently wide to pass all of the channels in an input signal and has a substantially constant voltage standing wave ratio over the bandwidth. The splitter supplies identical signals to several filtering paths, each of which comprises a fixed filter. The paths are selectable one at a time and the filters divide the input frequency band into a plurality of contiguous or slightly overlapping sub-bands. The output of the front end is supplied to, for example, a double conversion arrangement comprising an upconverter and a downconverter with first and second IF filters.

Abstract: A radio frequency amplifier including a long tail pair of transistors provided with a tail current source. The bases of the transistors are driven by emitter follower transistor provided with collector load resistors. Feedback capacitors ensure stability and feedback resistors bias the amplifier without degrading noise performance. The amplifier may be driven unbalanced while retaining good second harmonic distortion performance.

Abstract: A radio frequency tuner comprises a first frequency changer for block upconverting the channels of an input broadband signal in a first frequency range to a higher second frequency range. A multiplexer selects between the output of the first frequency changer and anyone of second broadband signals in the second frequency range. A second frequency changer has a variable frequency local oscillator for selecting and converting to I and Q baseband signals any selected channel in the broadband signal from the multiplexer.

Abstract: A tuner is provided for converting any selected channel in an input band to zero intermediate frequency. The tuner input is connected to the inputs of a plurality of input stages. Each input stage comprises tracking filters having a passband which is tunable across the tuning range of the input stage, where the tuning ranges of the stages form a contiguous or overlapping set so as to provide tuning across the whole of the input band. Only one of the input stages is enabled at a time with the disabled stages being depowered. A frequency changer converts the selected channel from the enabled input stage to substantially zero intermediate frequency.

Abstract: A front end for a radio frequency tuner, for example for connection to a cable distribution network, including an input connected to a signal path comprising an LNA connected via an AGC stage to a signal splitter. The input path has a bandwidth sufficiently wide to pass all of the channels in an input signal and has a substantially constant voltage standing wave ratio over the bandwidth. The splitter supplies identical signals to several filtering paths, each of which comprises a fixed filter. The paths are selectable one at a time and the filters divide the input frequency band into a plurality of contiguous or slightly overlapping sub-bands. The output of the front end is supplied to, for example, a double conversion arrangement comprising an upconverter and a downconverter with first and second IF filters.

Abstract: A radio frequency amplifier including a long tail pair of transistors provided with a tail current source. The bases of the transistors are driven by emitter follower transistor provided with collector load resistors. Feedback capacitors ensure stability and feedback resistors bias the amplifier without degrading noise performance. The amplifier may be driven unbalanced while retaining good second harmonic distortion performance.

Abstract: An input interface is provided for interfacing between a radio frequency input, for example from a cable distribution network, and a plurality of radio frequency tuners. The interface comprises a broadband active multipath non-reactive power splitter having an input for receiving a broadband radio frequency signal and a plurality of differential outputs. The splitter further has an active power splitting circuit which supplies the broadband radio frequency signal to each of the outputs via a channel comprising an automatic gain control circuit having a single-ended output connected to the input of a differential output buffer.

Abstract: A phase lock detector for a digital phase locked loop frequency synthesiser in which phase errors, represented by phase error pulses of a duration equal to the relative time displacement of synthesised and reference waveforms in the phase locked loop, are compared with a predetermined time interval representing the maximum phase error acceptable in a phase-lock condition. A favourable result of the comparison may be required to persist for a predetermined time before a phase-lock indication is given, to avoid jitter or flicker of that indication in a near-lock situation.