Abstract: A tuner for analogically and digitally modulated signals comprises a single tuner arrangement for converting any selected analog or digital channel to baseband or zero lF quadrature signals. Simple analog low pass filtering is applied before conversion in an ADC to the digital domain. A digital signal processor performs channel filtering and signal correction and supplies a signal to a digital demodulator. The processed digital signals are also supplied to a digital remodulator and DAC.

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 multiple conversion tuner comprises a plurality of cascade-connected frequency changers, each of which comprises a mixer and a local oscillator. The tuner also comprises a local oscillator frequency selecting circuit which controls the frequencies of the local oscillators. The frequencies are controlled so that the final mixer converts a desired signal to the final intermediate frequency and so that the frequency band occupied by the desired signal at the output of each mixer is within the passband of the following intermediate frequency part of the tuner.

Abstract: A single conversion tuner is provided for receiving digital terrestrial broadcast signals. The tuner comprises a single frequency changer comprising a mixer and local oscillator controlled by a PLL synthesiser. A non-alignable variable low pass filter is provided between the tuner input and the mixer, which is of the image reject type. The bandwidth of the filter is varied so as to track the local oscillator frequency to provide sufficient attenuation of the image channel without requiring any alignment during manufacture.

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: An amplifier, for example for use as an LNA of a radio frequency tuner, comprises a differential amplifying stage provided with an AGC core. The output signals are formed across load resistors at differential outputs. Compensating stages sum the signals at the differential outputs and subtract the resulting sum signal from the output signals so as to cancel the common mode signals including second order distortion products.

Abstract: A circuit stage such as an input stage is provided for a radio frequency tuner having an input which typically receives a broadband signal comprising many channels. The input stage comprises a low noise amplifier in the form of a long tail pair of transistors and a controllable tail current source. A level detector detects the signal level at the input of the amplifier and controls the tail current source so as to increase the tail current as the signal amplitude rises above a threshold level and so as to keep the tail current fixed when the signal amplitude is below the threshold.

Abstract: A multiple tuner arrangement is formed on a single integrated circuit having a common radio frequency input terminal. The terminal supplies a broadband input signal to a plurality of individual tuners, which may be identical to each other in construction. The tuners operate simultaneously and independently of each other to convert a channel in the radio frequency input to the appropriate output intermediate frequency and supply this to the channel output terminal. Features such as a databus interface and a common reference oscillator for channel frequency synthesisers need not therefore be duplicated.

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 tuner comprises a frequency changer which converts an input signal to a predetermined fixed intermediate frequency. The frequency changer is followed by an IF filter having a filter parameter, such as center frequency, which is electronically adjustable. A controller adjusts the adjustable filter characteristic so as to achieve a predetermined desired filtering performance, such as ensuring that the filter center frequency corresponds to the desired intermediate frequency. The controller comprises a local oscillator having the same type of tuned circuit as the IF filter. A phase locked loop compares the local oscillator frequency with a reference frequency and controls the tuned circuits of the IF filter and the local oscillator.

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 tuner comprises a first frequency changer with a mixer and local oscillator. The output of the frequency changer is connected to a first intermediate frequency filter, whose output is connected to a second frequency changer. The output of the frequency changer is connected to the usual second intermediate frequency filter and to an amplitude detector. A reference oscillator is connectable under control of a controller via a multiplexer to the input of the mixer. During an alignment mode of the tuner, the reference signal from the oscillator is supplied to the mixer and the local oscillators and are controlled by the controller to sweep across a frequency range encompassing all possible pass frequencies of the filter. The controller monitors the output of the detector so as to establish the frequency response of the filter. Frequency offsets are then stored in the synthesizers and so as to center each channel during a reception mode on the actual center frequency of the filter.

Abstract: A multiple conversion tuner comprises a plurality of cascade-connected frequency changers, each of which comprises a mixer and a local oscillator. The tuner also comprises a local oscillator frequency selecting circuit which controls the frequencies of the local oscillators. The frequencies are controlled so that the final mixer converts a desired signal to the final intermediate frequency and so that the frequency band occupied by the desired signal at the output of each mixer is within the passband of the following intermediate frequency part of the tuner.

Abstract: A radio frequency tuner is provided for selecting channels from a cable distribution network or other reception system. The tuner has one or more stages whose performance, such as signal to noise plus intermodulation, and gain are functions of the stage power consumption. A comparator compares the tuner performance, such as bit error rate, with a predetermined performance. When the tuner performance exceeds the predetermined performance, a power consumption control circuit reduces the power consumption of one or more of the stages so as to reduce the tuner power consumption while maintaining acceptable tuner performance. As an alternative, the control circuit may have an input which allows the power consumption to be preset in accordance with the tuner application. The control circuit also controls a variable gain arrangement to compensate for changes in gain resulting from changes in power consumption.

Abstract: A digital tuner has an input tuning range with lower and upper limit frequencies. An up converter converts an input signal to an intermediate frequency signal whose frequency is higher than the upper frequency limit of the input range. A downconverter is a zero intermediate frequency quadrature converter which converts the intermediate frequency signal to in-phase and quadrature baseband signals. The upconverter has a local oscillator fundamental frequency which is greater than the upper frequency limit of the input tuning range.

Abstract: A modem tuner of ZIF or NZIF type comprises a mixer which receive first and second inputs via a multiplexer in different frequency ranges from different sources such as cable and satellite. A local oscillator supplies signals via a bandswitch which switches the local oscillator frequency range in synchronism with the selection of inputs by the multiplexer. The mixer converts the selected incoming data stream to zero or near-zero intermediate frequency and this signal is filtered exclusively by a variable bandwidth low-pass filter before being converted to the digital domain and demodulated.

Abstract: A tuner for digital terrestrial television has an input section which supplies a sampled intermediate signal, for example at zero intermediate frequency and digitised by an ADC, corresponding to a desired reception channel corrupted by interference such as impulsive noise interference. A threshold generator generates a threshold which is larger than a moving average of the amplitudes of consecutive samples and a comparator compares the amplitudes of the samples with the threshold. If a sample amplitude exceeds the threshold, a corrector sets to zero the sample before processing by a fast Fourier transform. The threshold generator excludes samples which have been set to zero from the moving average.

Abstract: An analogue single conversion tuner comprises a plurality of channels (1, 2, 3) for covering the whole of a desired reception bandwidth. Each tuner comprises an image reject mixer (18) connected to the tuner input (4) by a single tracking filter (16), for example of the single-tuned type.