Abstract: A filter can include a first channel and a second channel. The first channel can be configured to process a first term and a second term of an input vector using a first coefficient and a second coefficient of the filter. The first channel can be configured to generate a first term of an output vector. The second channel can be configured to process the first term and the second term of the input vector using the first coefficient and the second coefficient of the filter. The second channel can be configured to generate a second term of the output vector. The first and second channels can be configured to operate in parallel.

Abstract: A channelization circuit channelizes baseband signals in the channels of a wideband signal. The channelization circuit includes a phase shifter, a Fourier transform circuit, filtering circuits, commutator circuits, and a summation circuit. The phase shifter circuit is configured to receive the baseband signals. The Fourier transform circuit is coupled to the phase shifter circuit and configured to frequency translate the baseband signals to the channels of the wideband signal. The filtering circuits are coupled to the Fourier transform circuit, and the commutator circuits are coupled to the filtering circuits. The summation circuit is coupled to the commutator circuits and configured to generate the wideband signal.

Abstract: Disclosed is a recursive, direct digital synthesizer includes an accumulator module and a Coordinate Rotation Digital Computer (CORDIC) module coupled to the accumulator module. The CORDIC module rotates a signal according to a desired rotation angle specified by the accumulator module. An automatic gain control module is coupled to the CORDIC module. The automatic gain control module can apply a level of gain to the rotated signal.

Abstract: Method and apparatus for peak-to-amplitude ratio reduction are described. A data carrying signal waveform with sub-carrier signals (S1-1 through S1-M) is obtained. An initial peak reduction waveform (S2(m)) is obtained by selection of a portion of the sub-carrier signals (S1-1 through S1-M) for non-data carrying. The initial peak reduction waveform (S2(m)) is refined by at least one recursive iteration which combines the initial peak reduction waveform (S2(m)) with a circularly time-shifted version thereof to obtain a resultant peak reduction waveform having a peak side lobe amplitude less than that of the initial peak reduction waveform (S2(m)).

Abstract: Method and apparatus for digital frequency synthesis are described. A frequency synthesizer has an accumulator, an adder, and a predictive filter. The adder is configured to subtract a predicted error from a phase profile signal. A quantized version of the phase profile signal is separated from an error portion thereof. The predictive filter, set for a fraction of a sample frequency bandwidth, is coupled to receive the error portion for generation of a next predicted error. A storage device has digital representations of sinusoidal signals accessible responsive to the quantized version of the phase profile signal. A digital-to-analog converter is coupled to receive a digital representation of a sinusoidal signal obtained from the storage device to provide an analog sinusoidal signal. An anti-imaging filter is coupled to receive the analog sinusoidal signal and configured to filter out noise.

Abstract: Signal conversion is implemented employing a memory system operating as a look-up table that stores a plurality of sets of output samples associated with each of a plurality of respective input samples. The look-up table thus can generate a corresponding set of output samples in response to a given input sample, thereby emulating desired digital upsampling and delta-sigma modulation. The output samples can be aggregated, such as by multiplexing, to provide an output data stream at a desired sample rate.

Abstract: A tunable narrow-band filter that includes a sigma-delta modulator. In one embodiment, a conventional DC canceler is modified to include a re-quantizer in the feedback loop in the form of a ?? modulator. In another embodiment, a digital receiver employs a processing chip, such as an FPGA, that includes a ?? modulator to requantize oversampled control signals in the digital receiver. In still another embodiment, a wide-bandwidth sigma-delta loop has a tunable center frequency.

Abstract: Signal conversion is implemented employing a memory system operating as a look-up table that stores a plurality of sets of output samples associated with each of a plurality of respective input samples. The look-up table thus can generate a corresponding set of output samples in response to a given input sample, thereby emulating desired digital upsampling and delta-sigma modulation. The output samples can be aggregated, such as by multiplexing, to provide an output data stream at a desired sample rate.

Abstract: A narrow-band bandpass filter is implemented in a field programmable gate array (FPGA). An analog-to-digital converter quantizes an input analog signal with a high degree of precision to produce input data samples. A sigma-delta modulator re-quantizes the samples with a substantially lower degree of precision. The re-quantized samples are passed through a bandpass, lowpass, or highpass, finite impulse response (FIR) filter which operates at the lower degree of precision. The reduced degree of precision enables a substantial reduction in the number of resources required to implement the narrow-band bandpass, lowpass, or highpass filter in the FPGA. The modulator includes a predictor filter which has a center frequency coinciding with that of the FIR filter, and redistributes noise such that it is lowest within the passband of the FIR filter. The narrow-band filter design can be adapted to incorporate a single or multi-rate decimator configuration.

Abstract: A circuit arrangement and method for direct digital synthesis (DDS). In various embodiments, the invention feeds forward the phase error introduced by a quantizer in a DDS system. The error is fed forward to adjust the sine and cosine values that are obtained based on output from the quantizer. Correction of the sine and cosine values based on the fed-forward error values results in a significant reduction in the effect of spectral artifacts.