Abstract: Strong narrowband signals interfering with the reception of a desired broadband signal in systems such as spread spectrum systems are continuously suppressed by converting the received signal to a frequency-domain representation thereof wherein strong narrowband interference components appear as strong impulse components. These impulsive components are blanked or clipped at a level that is a function of the average magnitude of the input signal. Resulting suppressed frequency-domain signals are reconverted to time-domain signals that are then available for further processing by conventional broadband signal receivers.

Abstract: A beamformer that accommodates signals of substantially wider bandwith than conventional phase-shift beamformers by processing signals coupled from an array of sensor elements in a multi-stage sequence of operations that alternate between phase-shift beamforming and time-delay steering.

Abstract: A CFAR estimator-correlator comprises an estimating filter responsive to the signal-plus-noise input process for providing an estimate of the signal waveform. The estimate and the signal-plus-noise process are applied to a correlator. An amplitude limiter interposed between the signal-plus-noise input and the correlator and a bandpass amplitude limiter interposed between the estimating filter and the correlator impart a CFAR characteristic to the apparatus. An interferometer is configured by utilizing separate sensors to provide a signal-plus-noise input process and a further signal-plus-noise input process to the amplitude limiter coupled to the correlator and to the estimating filter, respectively.

Abstract: An incoming signal is tested for the presence or onset of a frequency shift keyed (FSK) signal which alternates at a known rate between two unknown frequencies separated by a known frequency shift. The incoming signal is time delayed an odd multiple of the keying period and the delayed signal is multiplied by the incoming signal to produce sum and difference frequencies when the FSK signal is present. The difference frequency is selected by filtration and multiplied by a time delayed version of itself to produce a steady phase signal. The steady phase signal is extracted by filtration, demodulated and integrated to produce a useable detector signal for comparison with a threshold level.

Abstract: An apparatus and method for measuring the average or carrier frequency of a frequency shift keyed (FSK) signal which consists of sinusoidal tones that alternate regularly in frequency at a known rate between two unknown frequencies separated by a known frequency shift. The incoming signal is multiplied by two delayed versions of itself to yield to product signals. The delay employed in the first version is nominally equal to the FSK shift rate and the second delay differs from the first by an incremental amount. The two product signals are passed through substantially identical bandpass filters centered at the shift frequency and having a bandwidth approximately equal to the shift rate, and the phase angles of the filtered signals are differentially compared and averaged to produce a signal proportional to the average frequency of the FSK signal.