Abstract:
Multi-dimensional finite impulse response filters are disclosed in hybrid and transpose forms. Multi-dimensional signals can be expressed in a vector (or matrix) form to allow multi-dimensional signals to be processed collectively. Known hybrid and transpose FIR filters are extended to the multi-dimensional case to allow multi-dimensional signals to be processed with reduced redundancies. The input signals are vectors with multidimensional components. The disclosed FIR filters include multipliers that perform matrix multiplications with multiple coefficients, and adders for performing vector additions with multiple inputs and outputs. The z-transforms are provided for the disclosed hybrid and transpose multi-dimensional FIR filters.
Abstract:
An arrangement is provided for using 2's complement arithmetic without the high switching activity of the prior art. In particular, the invention operates to exploit the sign-extension property of a 2's complement number. A reduced representation for 2's complement numbers is provided to avoid sign-extension and the switching of sign-extension bits. The maximum magnitude of a 2's complement number is detected and its reduced representation is dynamically generated to represent the signal. A constant error introduced by the reduced representation is also dynamically compensated.
Abstract:
A method and apparatus are disclosed for converting a signal between the analog and digital domains using frequency interleaving. The disclosed frequency interleaving techniques can be similarly applied to convert analog signals to the digital domain or vice-versa. An analog-to-digital converter decomposes the input broadband signal into N frequency bands that are separately sampled (quantized) before a Fourier transform is applied to convert the signal into the digital domain. Each of the frequency bands can be sampled in the corresponding narrow passband using narrow-band converters, such as passband Sigma-Delta converters, or can be returned to baseband prior to sampling. The various analog samples are then converted to the digital domain using an inverse Fourier transform, or another combining technique. Both sampling and analog-to-digital conversion can be performed at a speed that is N times slower than the input frequency. The disclosed frequency interleaving technique decomposes the input signal into frequency bands that are digitized separately at a slower rate. A disclosed calibration scheme corrects for phase and gain mismatches.
Abstract:
A digital signal processor and method are disclosed with one or more non-linear functions using factorized polynomial interpolation. A digital signal processor evaluates a non-linear function for a value, x, by obtaining two or more values from at least one look-up table for said non-linear function that are near said value, x; and interpolating said two or more obtained values to obtain a value, y, using a factorized polynomial interpolation.
Abstract:
A method and system for canonical channel estimation in the Long Term Evolution uplink where a multi-frequency signal is generated and then converted to frequency spectrum which is then convolved in the frequency domain with a truncated window function to obtain a time domain channel impulse response. The time domain channel impulse response can be then transformed to a frequency domain to produce a down sampled user channel response, which can be then linearly interpolated to provide a channel estimate for a plurality of subcarriers. Such an approach achieves channel estimation within Long Term Evolution at only canonical locations to reduce complexity without loss in channel entropy.
Abstract:
Methods and apparatus are provided for direct synthesis of RF signals using a delta-sigma modulator. An RF signal is synthesized from an input signal by quantizing the input signal using a quantizer, such as a one bit quantizer; determining a quantization error associated with the quantizer; generating an error prediction value using an error predictive filter, wherein the error predictive filter comprises one or more filter zeroes on a unit circle for one or more desired frequencies of f1, f2, . . . fn and one or more filter poles having a magnitude inside the unit circle and a frequency substantially equal to the one or more desired frequencies of f1, f2, . . . fn; and subtracting the error prediction value from the input signal. The filter poles have a magnitude that reduces a boost provided out-of-band.
Abstract:
In one embodiment, a receiver is provided for use in a multiple-input system that includes a receiving antenna receiving a time-domain signal corresponding to a plurality of signals transmitted from a plurality of transmitting antennas. The receiver includes: (a) a transform unit adapted to transform the time-domain signal into a frequency-domain signal; (b) a channel estimation unit adapted to estimate, based on the frequency-domain signal and a frequency-domain pilot signal, a combined transfer function corresponding to a plurality of transfer functions of respective channels between the plurality of transmitting antennas and the receiving antenna; and (c) a channel separation unit including a plurality of frequency-domain convolution units that separate the combined transfer function into a plurality of estimated channel transfer functions.
Abstract:
A method and apparatus are provided for joint equalization and decoding of multilevel codes, such as the Multilevel Threshold-3 (MLT-3) code, which are transmitted over dispersive channels. The MLT-3 code is treated as a code generated by a finite-state machine using a trellis having state dependencies between the various states. A super trellis concatenates the MLT-3 trellis with a trellis representation of the channel. Joint equalization and decoding of the received signal can be performed using the super trellis. A sequence detector is disclosed that uses the super trellis or a corresponding reduced-state trellis to perform joint equalization and decoding of the received signal to decode the MLT-3 coded data bits. The sequence detector may be embodied using maximum likelihood sequence estimation that applies the optimum Viterbi algorithm or a reduced complexity sequence estimation method, such as the reduced-state sequence estimation (RSSE) algorithm.
Abstract:
A method and apparatus are disclosed for canceling cross-talk in a frequency-division multiplexed communication system. The disclosed frequency-division multiplexed communication system employs multiple carriers having overlapping channels and provides an improved cross-talk cancellation mechanism to address the resulting interference. Bandwidth compression is achieved using n level amplitude modulation in each frequency band. An FDM receiver is also disclosed that decomposes the received broadband signal into each of its respective frequency bands and returns the signal to basehand in the analog domain. Analog requirements are relaxed by removing cross-talk from adjacent R-F channels, from image bands, and minimizing the performance degradation caused by In-phase and Quadrature-phase (I/Q) phase and gain mismatches in modulators and demodulators. The disclosed transmitter or receiver (or both) can be fabricated on a single integrated circuit.
Abstract:
Methods and apparatus are provided for whitening quantization noise in a delta-sigma modulator using a dither signal. An input signal is quantized using a predictive delta-sigma modulator by quantizing the input signal using a quantizer; adding a dither signal at a first location of the predictive delta-sigma modulator; determining a quantization error associated with the quantizer; removing the dither signal at a second location of the predictive delta-sigma modulator (for example, by subtracting a substantially similar version of the dither signal at the second location); generating an error prediction value using an error predictive filter; and subtracting the error prediction value from the input signal. The dither signal may be a white noise signal and may optionally be generated using a pseudo-random number generator.