Unisys Corporation

Scott R Bullock

Patrick J Smith

Ronald S Leahy

Laurence D Sawyer

Jeffery Mac Thornock

A signal detector for receiving a wide band (W) of frequency-hopped signals which channelizes the incoming signals, via filter banks into a plurality (L) of channels. Magnitude squaring circuits in each channel generate a 'power' estimate which is compared to a preset threshold value by threshold-quantizer units that produce a positive voltage (=1) if the threshold is exceeded. After summation of all the channels, the direct sequence (DS) signal component and noise component are processed so that a DC voltage is produced if a frequency-hop signal (FH) is present which is greater in value than when the signal is not present. Thus the DC signal indicates whether the FH signal is present or absent.

Channelized binary-level radiometer

A narrowband parameter estimator circuit is described which can be used to estimate the frequency and the relative power of narrowband interference tones which reside in a wideband information signal. A two-weight adaptive filter with a phase/frequency-lock loop circuit works in conjunction with a stepped synthesizer to lock onto the individual narrowband interference tones. A lock-detect circuit signals a digital logic unit to record the frequency of the stepped synthesizer and to measure the power in the adaptive filter output signal. This same output signal is used to cancel the unwanted tone in the wideband information signal being transmitted.

Narrowband parameter estimator

A hop rate detector, for receiving frequency-hopped signals carrying information data, which generates a tone at the 'hop rate' when modulated or unmodulated frequency-hopped signals are present. The input signal is channelized into sub-bands via filter banks and the signal in each channel is power detected (squared) and compared to a present threshold to produce a positive voltage (='1') if the threshold is exceeded and zero volts (='0') otherwise. The channel signals are split into an upper band (B.sub.u) and lower band (B.sub.d), then each band is summed and the lower band sum subtracted from the upper band sum to provide a first stage signal. The first stage signal has its DC component removed, then is multiplied by a delayed copy of itself to provide a frequency tone indicating the hop rate of the received signal.

Channelized binary-level hop rate detector

An I-Q channel adaptive line enhancer has bandpass filters with passbands that can be widened to well beyond the band that is actually being processed by the adaptive line enhancer. This eliminates the requirement of filtering one of the sidebands as is required in single channel adaptive line enhancers, in which the sum and difference sidebands are generated on up-conversion. Band limiting is done with lowpass filters, and the local oscillator may be made variable so that any part of the band that is passed by the bandpass filters can be processed by a single I-Q channel adaptive line enhancer. This type of I-Q channel adaptive line enhancer can process any one of a large number of possible bands without tunable bandpass filters, or without banks of adaptive line enhancers which have been preset to adjacent sub-bands.

I-Q channel adaptive line enhancer

The reference channel, the narrowband channel, and the error feedback channel are all constructed with analog components, while the adaptive processor is constructed with digital components. Unavoidable analog time delays in the narrowband and the error feedback channels are compensated for in the digital adaptive processor. The adaptive line enhancer described herein employs a local oscillator signal which is mixed with the input signal in a reference channel, which is subsequently converted to a digital signal. A digitized reference signal is supplied to an adaptive filter as an input signal. The adjustable weight values of the adaptive filter are adjusted by a feedback digitized signal. The output signal is derived from the subtraction of a narrowband analog signal, which is derived from the adaptive filter. The error feedback signal is split off of the output signal, mixed with the local oscillator signal, and supplied to the weight update mechanisms.

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Cos, CO, United States of America

Scott R Bullock