Her Majesty the Queen in Right of Canada, As Represented by the Minister

Her Majesty the Queen

Trevor W Tucker

Larry J Conway

William D Cornish

Sylvain L Bouchard

A method and apparatus for frequency conversion comprising sampling an input signal having a first frequency with first time delays between samples in an input delay line, and distributing the samples of the input signal in sequence to an output delay line with different time delays between samples than the first time delays, to generate an output signal of different frequency than the input signal.

Sampling frequency converter

A sampling spectrum analyzer provides instantaneous continuous wideband spectrum analysis to allow RF signals occurring simultaneously and spaced within the band to be displayed. An input signal is split and each resulting portion is passed down a tapped delay line, with samples at the taps of each line being processed by separate arithmetic units. The output of each arithmetic unit is applied to the taps of output delay lines which are similar to the input delay lines. Each arithmetic unit weights the input samples with a set of coefficients and sums the resulting signal in a prescribed manner, thus transforming the signal into the frequency domain, according to a discrete Fourier transform. The resulting sums are the real and imaginary terms of a signal which are vectorially added, resulting in a signal which is fed to the ordinate of a display having a swept time base representing frequency.

Sampling spectrum analyzer

Known electronic countermeasures systems have difficulty handling some modern radar signals, for example frequency agile, frequency sliding or frequency coded signals. The invention disclosed overcomes the problems of the prior art by using an analog frequency dividing system to virtually instantaneously down-convert received signals in octave steps and in octave stages into the frequency regimes associated with the operation of processing devices, such as analog to digital converters, digital logic devices, surface acoustic wave devices, and charge coupled devices. Those processed signals which are selected for retransmission, perhaps in a modified form, are then up-converted into the region of the received signal by the appropriate number of stages of frequency multipliers. Any modification in such signal parameters as signal duration, delay, frequency, phase, power, amplitude or spectral content may be incorporated prior to the first multiplication stage, between multiplication stages, after the last multiplication stage, or any combination of the above.

Countermeasures system

This invention relates to a system for storing a pulse modulated radio frequency signal and for accessing and reconstructing the stored signal repetitively whereby it can be retransmitted as desired, either at the same frequency or at a shifted or shifting frequency. An input delay line is sampled at a plurality of locations and the signal samples are stored by a plurality of capacitors. The capacitors are accessed at will and the stored samples are applied to locations on an output delay line similar to the input delay line, where the input signal is reconstructed.

Microwave storage device

Disclosed is a microwave frequency generator for producing a microwave signal with high frequency accuracy, high spectral purity, low noise and high frequency stability. It is known to phase lock the fundamental microwave oscillator to a highly stable crystal oscillator at lower frequency and convert to a higher output frequency with a multiplier or harmonic generator but fm noise is also multiplied. The present invention avoids this problem by using MESFET frequency dividers to phase lock a microwave oscillator to a stable reference oscillator without the need for frequency multipliers. The MESFET frequency divider provides signal gain instead of loss during operation.

Microwave phase locked loops using FET frequency dividers

It is known to generate mircowave frequencies by locking the fundamental output frequency of a microwave oscillator to a multiple or sub-multiple of the output frequency of a highly stable crystal oscillator operating at a lower frequency than the microwave oscillator. Phase-locked loops are used together with frequency multipliers or dividers. One problem is that the frequency lock range decreases as successively higher and weaker harmonics are used for locking. This limits the practical harmonic locking range to multiples of approximately less than ten. The present invention eliminates this problem and allows microwave signals which have a frequency greater than 10 times the reference frequency to be phase locked without an impractical reduction of the capture range. As well, in conventional phase locked loop systems which use multipliers, fm modulation which is intentionally injected must have a modulation index less than 1.0. The present invention eliminates this problem and increases the allowed modulation index by a factor N, where N is the division ratio of the frequency divider used in the feedback loop. The present invention uses a microwave parametric frequency divider to phase lock a microwave oscillator to a stable reference oscillator without the need for frequency multipliers. The output f1 of an rf oscillator is divided by N and fed to one input of a phase detector. The phase detector has another input fed by a reference oscillator of predetermined frequency f.sub.2. The phase detector has an output fed to a control input of the rf oscillator which causes the rf oscillator to produce a frequency of Nf.sub.2 which is directly fed to the rf output of the apparatus. Note that no multiplier is required.

Microwave frequency division by phase locked loops

It is known to measure the frequency of microwave signals by heterodyne conversion or by transfer oscillator techniques. Heterodyne conversion frequency counters are limited in their ability to measure the frequency of pulsed microwave signals. On the other hand, while transfer oscillator frequency counters can measure the frequency of pulsed microwave signals they have limitations in measuring signals with large frequency modulation components. The present invention utilizes analog microwave frequency dividing devices to virtually instantaneously convert the signal to be measured in octave steps into the frequency regimes associated with digital frequency counters. The apparatus disclosed comprises an antenna or other device for receiving a microwave frequency signal and feeding it to an analog frequency divider system having n stages, where n is an integer, each stage dividing frequencies applied to it by a factor of 2. The output of the divider system feeds a digital counter which, in turn, feeds a digital display device which displays a number equal to 2.sup.n times the output of the digital counter and hence equal to the frequency of the received microwave signal.

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Ottawa, Canada

Trevor W Tucker