Abstract: A sensor system is provided having a front end (81) and a digital signal processing unit (82) adapted for providing sensitivity enhancement. The front end (81) includes a sensor (10) whose output signal is digitized (11) and coupled to the digital signal processing unit (82). The digital signal processing unit (82) has a matched filter function to measure the signal's energy with minimum statistical error energy caused by white noise. The digital signal processing unit (82) also includes a matrix digital signal processor (12) that linearly utilizes the white noise values in the input's wider band spectrum to further suppress the white noise statistical error energy in the matched filter, to enhance the system sensitivity. The digital signal processing unit (82) also includes mode digital signal processors (13) to combine multiple event inputs in a manner that further improves sensitivity over extended time periods.

Abstract: A system and method are provided that includes at least a pair of spaced antennas having overlapping fields of view. The system further includes at least a pair of receivers respectively coupled to the pair of antennas. Each of the receivers includes a spectral separator having a plurality of output signals. Each of the output signals represents a signal value at one of a plurality of predetermined frequencies. A plurality of analog to digital converters are coupled to a corresponding one of the spectral separators for respectively providing a digital representation of each of the output signals. A digital processor coupled to an output of each of the plurality of analog to digital converters calculates an angle of arrival of the transmitted signal in at least one dimension from the digital representations.

Abstract: A real time channelized digital receiver partitions broad frequency bands into channels so that signals in each channel can be independently sensed or modulated. The digital receiver includes a high performance analog-to-digital converter that outputs a digital signal at a high clock rate and a Digital Signal Processor (DSP) that performs a real time channelization filtering operation at a slower clock rate. The DSP may use a multiplexer/demultiplexer approach to match unequal clock rates. The receiver can eliminate alias terms by improving Digital Radio Frequency Memories using quadrature processing with RF/IF mixers or digital processing to multiply the tones. The receivers and memories can also be improved with a homodyne operation that simplifies decimation and reconstitution for digital RF memory applications.

Abstract: An efficient digital integration technique (EDIT) filter uses a local oscillator pattern to provide the desired weighting for an input signal. A product waveform is determined by multiplying the local oscillator pattern and the input signal. The product waveform is then summed by a summing circuit with no additional multiplies. The output of the summing circuit is the filtered signal. Thus, a single multiply operation is required for the filter, thereby reducing costs.

Abstract: A digital filter and modulator provides programmable distinctive modulation on a programmable frequency selective basis with channelization. The digital channelization processor includes a plurality of channels. Each channel includes a filter and transform circuit that convert a real input signal to a quadrature signal that has a magnitude signal and a phase signal. The quadrature signal is offset and converted back to a real signal that is temporarily held and phase shifted. The digital filter and modulator minimize throughput delay and eliminate analog tolerance and inflexibility problems while eliminating digital processing overflow difficulties.

Abstract: A wideband digital microwave receiver includes a plurality of channels. Each channel includes an I sub-channel and a Q-sub-channel. Each channel also has a comb generator. Each sub-channel has a mixer for multiplying the signal from the comb generator and an input to that sub-channel. By offsetting the combs used in the channels, the true solution may be selected from a number of false solutions. This may be achieved by cross-multiplying outputs from the I sub-channels and cross-multiplying outputs from the Q sub-channels. The signal information may be stored in a buffer and pre-processed. The single true solution is output to a digital signal processor and/or a monitoring unit.

Abstract: A coherent radio frequency memory (CRFM) which employs a digital RF memory (DRFM) and a power limiter at its input for limiting the power of the RF input to a relatively constant level over a broad range of such inputs. In addition, a RF noise generating means is coupled to the input of the DRFM at the optimum level for providing random noise for decorrelating spurious outputs of the DRFM.

Abstract: A modulated single channel (as opposed to a quadrature channel) digital radio frequency memory (DRFM) system retrievably stores incoming radio frequency (RF) signals in a digital memory and replicates the RF signals at the output. The input RF signal to be stored is mixed with a local oscillator (LO) signal modulated with a waveform pattern to produce an intermediate frequency (IF) signal which is digitized and retrievably stored in the digital memory. The stored digital values are later retrieved from memory after the programmed delay time, and converted back to an analog IF signal and mixed with the local oscillator to produce the output RF signal. The LO signal is modulated with the same waveform used to produce the input IF signal. A controller for controlling the modulation of the LO signal and the memory includes a ROM for storing a pseudo random string of one bit words and an address counter to drive the ROM beginning at a starting address upon the occurrence of the input RF signal.

Abstract: A decorrelated spur digital radio frequency memory (DRFM) system stores incoming radio frequency (RF) signals in a digital memory and at some later time replicates these RF signals at the output. The input RF signal to be stored is mixed with a local oscillator (LO) signal, which is coded with a decorrelation waveform, to produce an intermediate frequency (IF) signal which is next digitized with a multibit analog-to-digital (A/D) converter. This data is stored in a digital memory and is later retrieved from the memory and converted back to an analog IF signal. The IF signal is then mixed with the coded LO to produce a replica of the original RF signal. The code on the LO is the same decorrelation waveform used to produce the input IF signal. The resultant RF output spectrum can be made to be spectrally clean, i.e., containing no spurious harmonic signals arising from the signal's quantization.

Abstract: An active radar jamming system using a digital radio frequency memory (DRFM) as the central subsystem in the generation and detection of specific signal characteristics. Associated systems control the operation, data processing, and loading of the DRFM. Signals generated by the jamming system are either repeated replicas of the received radar signal stored in the DRFM, or newly generated signals constructed from data loaded into the DRFM by the associated subsystems. Such associated subsystems generate appropriate data for providing carrier and noise RF signals. Systems are also provided for determining the presence of phase coding and chirp modulation in the received radar signal data contained in the DRFM, and for detecting the angle-of-arrival of the radar signal.

Abstract: A digital radio frequency memory (DRFM) system for storing and retrieving radio frequency signals in a digital memory. The system includes a digital memory, digital converters at the input and output of the digital memory, and input and output mixers. The RF signal to be stored is applied to the input mixer along with a modulated local oscillator signal to produce an IF signal which is converted into digital values for storage in the digital memory. When the stored digital values are retrieved from the memory to reproduce the RF signal, they are converted back into an analog IF signal which passes through a low-pass filter before being applied to the output mixer. The local oscillator signal, modulated with the same waveform used in storing the digital values, is also applied to the output mixer to provide the reconstructed RF signal. A pseudo random, discrete digital valued waveform is used to phase modulate the local oscillator signal in the preferred embodiment of the invention.

Abstract: There is disclosed herein a method of applying an active electronic countermeasure (ECM) False Target technique against MTI staggered pulse threat radar. This is accomplished by radar circuits which digitally transfer false target arrays grouped about low pulse repetition frequency (PRF) pulses to high PRF pulses, when they are present. The circuits of the invention then phase shift each transferred array with respect to the fundamental system clock rate to achieve proper alignment.

Abstract: A pulse detection radar signal receiver is disclosed which includes at least one pulse detection channel that has an RF amplifier and a feedback signal path coupling the output to the input thereof for recirculation of signals therethrough. The feedback path includes a signal-to-noise (S/N) enhancer circuit and an inhibiting means, preferably disposed in series therewith. The S/N enhancer circuit is operative to adaptively focus a narrow enhancement bandwidth about the frequency of an input signal, which has a power level greater than a predetermined threshold level, for enhancing signals which have frequencies within said enhancement bandwidth and for attenuating signals which have frequencies outside said enhancement bandwidth. The enhanced and attenuated signals are provided to the input of the RF amplifier for recirculation therethrough.

Abstract: The repetition frequency tracking apparatus utilizes the input signal to start a timer to provide the correct phase. When the timer sweeps through the right frequency, the tracker will lock to a single pulse train within a two octave frequency spectrum. After the lockup, the tracker is switched to a free running mode to provide pseudo synchronous running through durations of missing input pulses. Accurate tracking is provided by the use of an early late gate phase discriminator for phase sensing and correcting to zero, errors at all locking frequencies.

Abstract: A self-calibrating microwave transponder incorporating an amplifier, modulator, instantaneous frequency discriminator, memory and voltage controlled oscillator is described which may generate an RF signal in response to the carrier frequency of received low duty cycle pulse RF signals. The instantaneous frequency discriminator is used to provide an address signal from the pulse RF signals which is used to access a memory that contains the correct tuning data for the voltage controlled oscillator to generate an RF signal.