Marconi Instruments Limited

Aeroflex International Limited

Cintex Limited

Neil E Thomas

John Norman Wells

Ian W Cox

Christopher Marcus

Robert M Averill

Peter John Howlett Fox

Clive F Kittel

A phase locked loop () comprising: a tuneable oscillator (); a mixer-based phase sensitive detector () to receive input signals from the tuneable oscillator () and a reference signal (); a cycle slip detector () to receive input signals from the tuneable oscillator () and the reference signal (), the cycle slip detector () being configured to generate an output signal when two consecutive pulses are present in one of its input signals without an intervening pulse in the other of its input signals; coarse tune signal means () to receive the output signal generated by the cycle slip detector; and adding means () for adding a signal output by the coarse signal means () to a signal output by the phase sensitive detector () to control the frequency of the tuneable oscillator ().

Phase locked loop

A waveform generator for generating a smooth version of an original waveform which contains abrupt transitions, includes a phase accumulator incremented at successive sampling times to produce an output representative of the phase of the original waveform, a phase scaler arranged to convert the residual contents of the accumulator following a transition from phase to time, computing means responsive to the time to calculate a number of samples along a smooth transition, each offset by that time from the sampling times, and a sequencer to replace the otherwise abrupt transition with the sequence of samples from the computed smooth transition.

Waveform generation

Method and apparatus for monitoring a series of products

Apparatus for synthesising a composite signal (53) which has spaced first and second frequency channels of which each has an independently predetermined power, the power of the first channel being substantially below that of the second, and each channel being frequency modulated by an independent signal, the apparatus including a generator (51) responsive to the independent signals and to representations of the said powers and to the channel spacing to generate a composite modulation signal, and a single, high purity radio frequency source (52) connected for modulation by the output of the composite modulation signal-generating generator to produce the composite signal (53).

Apparatus for synthesizing a composite RF signal suitable for use as a

A frequency counter for counting pulses of a variable input signal (Fin) using another input signal (Fgate) of a different, fixed frequency as a reference, includes a noise-shaping synchronizer (20,23,24) for retiming pulses of the lower frequency input signal to have a fixed timing relationship with selected pulses of the higher frequency input signal such as to introduce substantially less phase noise onto the lower frequency input at low modulation rates that would be the case with a simple synchronizer; and a counter and a latch (11,12) responsive to the retimed pulses (13) and to the higher frequency input signal (Fin) to provide a data output representative of the ratio between the frequencies of the input signals.

Frequency counter

A frequency or phase modulator, in particular a DC-coupled frequency modulation synthesizer, comprises a voltage-controlled oscillator (1) in series with a divider (2) in a phase-locked loop, and an analog-to-digital converter (17) connected to control the divider in accordance with an input analog modulation signal. The converter (17), preferably a one-bit charge-balanced converter, has a noise-shaped frequency response to reduce noise at frequencies below the loop-bandwidth.

Frequency or phase modulation

A phase comparator accepts two streams of digital pulses, one being a reference signal and the other a test signal, and generates an output signal indicative of the phase difference. The phase comparator can be implemented as a four-state device or higher, and thus exhibits a wide phase capture range, i.e. multiples of 360.degree., and can provide a stable, predictable and linear output signal when the two input signals are in lock. It is therefore very suitable for use in a phase locked loop in which temporary wide variations in phase can occur.

Phase comparators

An attenuator is in the form of a pad comprising a coating of resistive material which connects an input port, an output port and a pair of linked constant potential ports. The regions of the pad adjacent to the outer edges of the input port are provided with outwardly pointing cusps with curved boundary edges. These reduce current crowding at the edges of the input port, and avoid localized overheating of the adjacent regions of the pad, which could result in pad failure.

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St. Albans, United Kingdom

Neil E Thomas