Abstract: 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.

Abstract: 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.

Abstract: 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.