Abstract: A non-systematic convolutional decoder of a convolutionally encoded multi-level data stream includes a shift register and two or more paths of exclusive-OR (XOR) gates, arranged to reconstruct an original input information stream, each path having a quantiser arranged to quantise the signal to two levels, and a set of XOR gates arranged to match an encoding path in an associated convolutional encoder, and a selector arranged to feed an output from each path to a single input of the shift register. If the paths have differing values at their output, the selector may choose the value from the path based upon a function of the multi-level signals associated with each path, such as the path with the largest absolute signal level. The decoder provides a simple means for decoding signals while allowing the signal to also or instead be decoded using e.g. a Viterbi decoder if higher performance is required.

Abstract: A system for compensating for phase noise, with particular application in lidar, includes a compensation interferometer that receives a signal from a source, and splits it into a first and second path, with a path length difference ?? between them. Typically the path length is significantly less than that of the return distance to a target. The output of the compensation interferometer, which consists of phase noise generated in time ?? is vectorially summed during a time similar to a signal flight time to a target, and the result used to reduce phase noise present on measurements of a target. It further includes means for selecting ?? such that competing noise elements are reduced or optimised.

Abstract: A radio receiver includes a downconverter for downconverting dual sideband signals such as Binary Offset Carrier (BOC) signals from multiple sources to produce an upper and a lower sideband signal, and chip-matched filters for filtering each of the sideband signals. The output of each filter is provided to a series of separate channels, one for each source, where there are at least Early, Prompt and Late gates. Each gate has a nearest-neighbour sampler and a multiplier for multiplying with an appropriate part of a spreading code, a mixer for removing Doppler or other frequency offsets and an integrator. The invention provides a means for demodulating signals such as BOC modulated satellite navigation signals in an efficient manner by using a single downconverter for the received signals of interest from the multiple sources.

Abstract: A radio receiver includes a downconverter for downconverting dual sideband signals such as Binary Offset Carrier (BOC) signals from multiple sources to produce an upper and a lower sideband signal, and chip-matched filters for filtering each of the sideband signals. The output of each filter is provided to a series of separate channels, one for each source, where there are at least Early, Prompt and Late gates. Each gate has a nearest-neighbour sampler and a multiplier for multiplying with an appropriate part of a spreading code, a mixer for removing Doppler or other frequency offsets and an integrator. The invention provides a means for demodulating signals such as BOC modulated satellite navigation signals in an efficient manner by using a single downconverter for the received signals of interest from the multiple sources.

Abstract: A method for the reception of a frequency hopped direct sequence spread spectrum signal includes acquiring the signal by splitting the received signal into a plurality of processing sub-channels, each corresponding to one or more hop frequencies; and within each sub-channel: i) subtracting any sub-carrier frequency from the received signal; ii) filtering the signal from (i) using a chip-matched filter; iii) selecting a sub-set of samples from the filtered signal; iv) correlating the sampled signal from step (iii) with a known reference signal to produce at least one correlator output. The output(s) from each sub-channel are provided to an input of a corresponding one or more common discrete time Fourier transforms (DTFT), and an output therefrom having a peak above a predetermined threshold is selected for further processing in the receiver. The method is a less expensive way of tracking the signal and can demodulate appropriately modulated signals.

Abstract: Some embodiments are directed to a method of determining the time of arrival of an incoming satellite signal at a receiver, including receiving an incoming signal, multiplying of the incoming signal by a first real-valued periodic modifying signal to produce a first modified output, correlating the first modified output to obtain a first correlation output, multiplying the incoming signal by a second real-valued periodic modifying signal to produce a second modified output, correlating the second modified output to produce a second correlation output and comparing the first correlation output with the second correlation output.

Abstract: A method for the reception of a frequency hopped direct sequence spread spectrum signal includes acquiring the signal by splitting the received signal into a plurality of processing sub-channels, each corresponding to one or more hop frequencies; and within each sub-channel: i) subtracting any sub-carrier frequency from the received signal; ii) filtering the signal from (i) using a chip-matched filter; iii) selecting a sub-set of samples from the filtered signal; iv) correlating the sampled signal from step (iii) with a known reference signal to produce at least one correlator output. The output(s) from each sub-channel are provided to an input of a corresponding one or more common discrete time Fourier transforms (DTFT), and an output therefrom having a peak above a predetermined threshold is selected for further processing in the receiver. The method is a less expensive way of tracking the signal and can demodulate appropriately modulated signals.

Abstract: A system for compensating for phase noise, with particular application in lidar, includes a compensation interferometer that receives a signal from a source, and splits it into a first and second path, with a path length difference ?? between them. Typically the path length is significantly less than that of the return distance to a target. The output of the compensation interferometer, which consists of phase noise generated in time ?? is vectorially summed during a time similar to a signal flight time to a target, and the result used to reduce phase noise present on measurements of a target. It further includes means for selecting ?? such that competing noise elements are reduced or optimised.

Abstract: Some embodiments are directed to a method of identifying a vehicle-borne transmitter emitting an interfering signal over a predefined frequency band. The method comprises monitoring the predefined frequency band at a first location to identify an emission of an interfering signal from a passing vehicle. If an interfering signal is detected, the method further comprises capturing a first image of the passing vehicle to enable an identity of the passing vehicle to be determined.

Abstract: The invention relates to a method of determining the time of arrival of an incoming satellite signal at a receiver, the method comprising: receiving an incoming signal, multiplying of the incoming signal by a first real-valued periodic modifying signal to produce a first modified output, correlating the first modified output to obtain a first correlation output, multiplying the incoming signal by a second real-valued periodic modifying signal to produce a second modified output, correlating the second modified output to produce a second correlation output and comparing the first correlation output with the second correlation output.

Abstract: A method of identifying a vehicle-borne transmitter emitting an interfering signal over a predefined frequency band. The method comprises monitoring the predefined frequency band at a first location to identify an emission of an interfering signal from a passing vehicle. If an interfering signal is detected, the method further comprises capturing a first image of the passing vehicle to enable an identity of the passing vehicle to be determined.

Abstract: An apparatus is provided for compensating for the effect of a moving door on a nearby ferromagnetic object detector. The ferromagnetic object detector is of a type to produce a main sensor signal indicative of the presence of a ferromagnetic object in the vicinity of the ferromagnetic object detector. Furthermore, the door is arranged relative to the ferromagnetic object detector such that movement of the door is liable to introduce an undesirable interference signal into the main sensor signal. The apparatus comprises an input (3) for receiving the main sensor signal and a door sensor signal that is responsive to an opening angle of the door. The apparatus also comprises an interference signal estimator (4) for estimating a door-related interference signal in dependence upon the door sensor signal and a model of interference for the door.

Abstract: An apparatus is provided for compensating for the effect of a stray ferromagnetic object moving past but not through a sensing region of a ferromagnetic object detector. The ferromagnetic object detector is of a type to produce a plurality of sensor signals, each sensor signal being influenced by the presence of a genuine ferromagnetic object moving through the sensing region but also liable to be influenced by the presence of the stray object. The apparatus comprises: an input for receiving the plurality of sensor signals and first means for analysing the received signals to determine whether there is a substantially same time-varying component present in each of the signals. The apparatus also comprises second means for determining whether the plurality of signals without the contribution of that time-varying component are each or collectively below a predetermined level of significance.

Abstract: Direction findings by radio comprises arraigning an array of antennas, to receive signals from emitters, selecting individual antenna signals using a first multipole switch and determining, antenna signal strengths. Individual antenna signals are also selected by mutipole switch, which routes a selected signal to a third multipole switch. The third switch switches a phase shifter into and out of an antenna signal path. An adder is employed to add an antenna signal in a first signal path extending via the first multipole switch to a different antenna signal in a second signal path extending via the second and third switches. This determines combined signal strengths between pairs of antenna signals, one of which either has or has not been relatively phase shifted depending on the third switch position. Covariance matrix elements are determined from signal strengths enabling emitter bearings to be derived.