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 tuner arrangement is provided comprising one or more tuners. Each tuner has two or more frequency changers, each comprising a mixer and a local oscillator. A controller controls the local oscillators in response to receipt of a channel select request. The controller determines the nominal frequencies of the local oscillators for tuning the selected channel and then performs a calculation to determine whether any beat frequencies between harmonics greater than the first harmonic of the local oscillators lie within the frequency band at the tuner output occupied by the selected channel. If so, the controller shifts the local oscillator frequencies so as to move the potentially interfering products outside the utilised band and then tunes the local oscillators appropriately.

Abstract: A tuner includes 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 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 terrestrial tuner has an RF input connected to a filter arrangement, whose output signal is supplied to a zero intermediate frequency frequency changer. The filter arrangement comprises a plurality of signal paths of different frequency responses. The signal paths are selectable one at a time for insertion between the tuner input and the frequency changer. At least one of the signal paths comprises a non-tracking filter which provides attenuation of out-of-band signals so as to reduce harmonic mixing caused by harmonics of the frequency changer commutating signal or by harmonics of spurious signals at lower frequencies.

Abstract: A pulse generator is provided for generating pulses with a selectable variable width and/or delay. The pulse generator comprises an oscillator and a selecting arrangement for selecting how many of a first group of delay elements are connected in series for delaying the oscillator signal. Identical delay elements are connected in series to form a second group. A measuring circuit repeatedly measures the delay provided by the second group, for example providing output pulses whose width or duration is equal to the delay. A reference pulse generator generates a series of reference pulses, each of which is a predetermined fraction of the oscillator period. A control circuit compares the measurement and reference pulses to generate an error signal that is fed back to timing delay control inputs of all the delay elements such that the widths of the measurement and reference pulses are made substantially equal to each other.

Abstract: A digital receiver comprises a quadrature zero intermediate frequency tuner supplying I and Q components to adjustable low pass analog filters. In the case of OFDM signals, a demodulator contains a measuring arrangement which determines the average power of carriers at the band edges and the average power of the OFDM carriers. These are compared and a controller increases the passbands of the filters 7 and 8 until the average level of the edge carrier is substantially equal to the average level of all of the carriers.

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 1F 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 tuner is provided for selecting a channel from a broadband radio frequency input signal containing a plurality of channels, such as a terrestrial broadcast signal. The tuner has an input which supplies the broadband signal to a filter. The output of the filter is connected to a mixer of a single frequency changer, which converts the selected channel to a predetermined non-zero intermediate frequency. The filter is a tracking radio frequency filter which tracks the frequency of the selected channel so as to attenuate the image channel. A controller receives from a demodulator a signal representing reception quality, such as bit error rate, and adjusts the tracking of the filter so as to achieve acceptable reception quality, such as an adequately low bit error rate. Alignment of the filter during manufacture is not, therefore, required.

Abstract: A multi-channel tuner apparatus is provided which is capable of simultaneously and independently selecting a plurality of channels for reception. The apparatus comprises a plurality of tuners, each of which converts a selected channel to a near-zero intermediate frequency. The output signals from the tuners are supplied to respective sample/hold circuits, whose outputs are supplied to a single analogue/digital converter for multiplexing the tuner signals and converting them to the digital domain. A common demodulator arrangement processes the digital domain signal to extract the information from all of the selected channels.

Abstract: A method is provided for reducing imbalance in a quadrature frequency converter. A test tone generator controlled by an alignment controller supplies a test signal to the input of the frequency converter. A starting point is selected in a solution space addressed by I and Q corrections. The starting point comprises in-phase (I) and quadrature (Q) phase correction values. A test is then performed to determine the best direction of movement in the I/Q phase correction plane in order to reduce phase imbalance. The I and Q phase correction values are then moved in that direction towards a phase imbalance minimum.

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: 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.

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: 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 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 tuner is provided for selecting a channel from a broadband radio frequency input signal containing a plurality of channels, such as a terrestrial broadcast signal. The tuner has an input which supplies the broadband signal to a filter. The output of the filter is connected to a mixer of a single frequency changer, which converts the selected channel to a predetermined non-zero intermediate frequency. The filter is a tracking radio frequency filter which tracks the frequency of the selected channel so as to attenuate the image channel. A controller receives from a demodulator a signal representing reception quality, such as bit error rate, and adjusts the tracking of the filter so as to achieve acceptable reception quality, such as an adequately low bit error rate. Alignment of the filter during manufacture is not, therefore, required.

Abstract: A multi-channel tuner apparatus is provided which is capable of simultaneously and independently selecting a plurality of channels for reception. The apparatus comprises a plurality of tuners, each of which converts a selected channel to a near-zero intermediate frequency. The output signals from the tuners are supplied to respective sample/hold circuits, whose outputs are supplied to a single analogue/digital converter for multiplexing the tuner signals and converting them to the digital domain. A common demodulator arrangement processes the digital domain signal to extract the information from all of the selected channels.

Abstract: A tuner is provided for selecting for reception any one of a plurality of channels in a broadband radio frequency signal supplied to its input. The tuner comprises a plurality of stages, at least some of whose gains and power consumptions can be adjusted by a controller in accordance with prevailing reception conditions. A frequency changer and variable gain amplifier provide a first filtering arrangement to reject non-adjacent channels and a tuneable filter rejects substantially all but the selected channel. Signal levels before the first filtering arrangement, between the first filtering arrangement and a second filtering arrangement formed by the tuneable filter, and after the second arrangement are supplied to the controller, which adapts the gain structure and/or individual stage power consumptions according to the prevailing reception conditions so as to provide an adequate performance for demodulation while reducing power consumption when extreme reception conditions are not encountered.

Abstract: A digital receiver comprises a quadrature zero intermediate frequency tuner supplying I and Q components to adjustable low pass analog filters. In the case of OFDM signals, a demodulator contains a measuring arrangement which determines the average power of carriers at the band edges and the average power of the OFDM carriers. These are compared and a controller increases the passbands of the filters 7 and 8 until the average level of the edge carrier is substantially equal to the average level of all of the carriers.