Abstract: The RF input of a radio receiver is converted to IF including received signal, noise and interference and fed to an interference detector and to an interference canceler of an interference suppressor. A fast Fourier transform (FFT) at the front end of the interference detector detects samples of all the interferences in the frequency domain. The frequency domain samples are scaled for gain control and detection of interferences above a predetermined threshold. The interference detector suppresses interferences to the predetermined threshold level. The scaled frequency domain interference samples are phase rotated and fed to an inverse fast Fourier transform to obtain a time domain replica of the interferences which are phase shifted replicas of the detected interferences.

Abstract: A threshold level generator for generating threshold levels to detect zero-crossings of a spread spectrum received waveform. An IF sampler quantizes the received spread spectrum signals at IF. The IF signal is sampled at a number of quarter cycle intervals to allow sampling in sequence of the in-phase (I) and quadrature-phase (Q) components. The outputs of the IF sampler are two bits, a sign bit and a magnitude bit. The threshold level generator using only the sign bit of the I and Q samples sets a threshold level (T0) to detect the zero-crossings of a received waveform. Two magnitude threshold levels are set at fixed offsets (D1 and D2) from the T0 threshold level.

Abstract: A spread spectrum signal detector for sampling a modulated carrier employing a zero-crossing detection means having two independent control loops, a first loop for a zero-mean threshold control and a second loop for AGC control. An IF sampler quantizeds the received spread spectrum signals at IF and provides high immunity to interference or jamming. The IF signal is sampled at a number of quarter cycle intervals to allow sampling in sequence of the in-phase (I) and quadrature-phase (Q) components. The output of the IF sampler is two bits, a sign bit and a magnitude bit. The zero-man threshold control loop using only the sign bit of the I and Q samples sets a threshold level (T0) to detect the zero-crossings of a received waveform. Two magnitude threshold levels are set at fixed offsets from the T0 threshold level.

Abstract: An apparatus and method for pseudo-random noise (PN) code correlation in a GPS receiver employing sign and magnitude input weighting for each of the in-phase (I) and quadrature-phase (Q) samples of a received PN-code modulated carrier. A programmable R factor provides input A/D sample sign and magnitude weighting control of outside crossing samples for interference rejection of other RF signals interfering with the received PN-code modulated RF carrier. The R factor weighting determines if the A/D samples are from a linear or adaptive A/D converter. In-phase reference (IREF) signals and quadrature-phase reference (QREF) signals, produced by an internally generated PN-code reference, are provided to a plurality of I and Q multi-Y-tap correlator/integrators for correlation with the I and Q samples. The apparatus correlates I and Q samples obtained from IF sampling or baseband sampling of the received PN-code modulated carrier.

Abstract: A spread spectrum signal detector for sampling a modulated carrier employing a zero-crossing detection means having two independent control loops, a first loop for a zero-mean threshold control and a second loop for AGC control. An IF sampler quantizes the received spread spectrum signals at IF and provides high immunity to interference or jamming. The IF signal is sampled at a number of quarter cycle intervals to allow sampling in sequence of the in-phase (I) and quadrature-phase (Q) components. The output of the IF sampler is two bits, a sign bit and a magnitude bit. The zero-mean threshold control loop using only the sign bit of the I and Q samples sets a threshold level (T0) to detect the zero-crossings of a received waveform. Two magnitude threshold levels are set at fixed offsets from the T0 threshold level.

Abstract: A radar receiver having a feed-forward control circuit for adjusting the automatic gain control (AGC) setting in 6 dB increments for each range cell in a next sweep based on the AGC setting of each corresponding range cell in the present sweep, the magnitude of the larger of the in-phase (I) or quadrature (Q) components of the video signals of the present sweep from an A/D converter, the status of present sweep and previous sweep A/D limit conditions, and a selected guardband thereby holding the level of the radar return signal within the dynamic range of the A/D converter. The AGC setting is adjusted using a switchable attenuator which changes the level of the video signal into the A/D converter in 6 dB increments, each increment corresponding to a common I and Q data exponent directly used for floating point signal processing.

Abstract: A vernier address scale reduces the number of addressable memory locations required for numerical look-up tables. Read-only memories (ROMs) store the data of linear or non-linear functions. Decoders determine which ROM is selected and advantage is taken of accuracy improvement as numbers become larger by dropping least significant bits as the vernier address scale moves from one ROM table to another. Accuracy is further improved by using a method of one-half level quantization step for rounding. This reduces the size of numerical tables for math processing of reciprocals, roots of numbers, powers of numbers, logarithms, trigonometric and exponential functions.

Abstract: A radar receiver having a feed-forward control circuit for adjusting the automatic gain control (AGC) setting in 6 dB increments for each range cell in a next sweep based on the AGC setting of each corresponding range cell in the present sweep, the magnitude of the larger of the in-phase (I) or quadrature (Q) components of the video signals of the present sweep from an A/D converter, the status of present sweep and previous sweep A/D limit conditions, and a selected guardband thereby holding the level of the radar return signal within the dynamic range of the A/D converter. The AGC setting is adjusted using a switchable attenuator which changes the level of the video signal into the A/D converter in 6 dB increments, each increment corresponding to a common I and Q data exponent directly used for floating point signal processing.

Abstract: A vernier address scale reduces the number of addressable memory locations required for numerical look-up tables. Read-only memories (ROMs) store the data of linear or non-linear functions. Decoders determine which ROM is selected and advantage is taken of accuracy improvement as numbers become large by dropping least significant bits as the vernier address scale moves from one ROM table to another. Accuracy is further improved by using a method of one-half level quantization step for rounding. This reduces the size of numerical tables for math processing of reciprocals, roots of numbers, powers of numbers, logarithms, trigonometric and exponential functions.