Patent application number | Description | Published |
20090086107 | RECIEVER SYSTEM FOR MULTIPLE BANDWIDTH TELEVISION CHANNELS - Disclosed is a receiver system, capable of receiving RF signals on television channels of multiple bandwidths. The receiver system includes a tuner, an analog IF filter, an ADC, a mixer module, one or more digital filters, an AGC module and a controller. The tuner converts an RF signal into an IF signal using a mixer frequency. The analog IF filter filters out a fixed band signal from the IF signal. The ADC module converts the fixed band signal into a digital signal, which is filtered by digital filters. The output of the digital filters is converted to a base band signal and the power level of the base band signal is controlled by the AGC module. The controller selects a mixer frequency from a group of mixer frequencies based on a function of power of the output of the AGC module by applying each mixer frequency to the tuner. | 04-02-2009 |
20120155577 | CHANNEL ESTIMATION FOR DVB-T2 DEMODULATION USING AN ADAPTIVE PREDICTION TECHNIQUE - According to various embodiments, a method is disclosed that includes receiving an orthogonal frequency-division multiplexing (OFDM) modulated signal at a modulator; filtering the received modulated signal using a plurality of sets of filter coefficients with a linear predictor algorithm; and estimating a channel frequency response based on the filtering. | 06-21-2012 |
20130272460 | INTER CARRIER INTERFERENCE CANCELLATION FOR ORTHOGONAL FREQUENCY DOMAIN MULTIPLEXING RECEIVERS - Apparatus and methods are described to perform inter carrier interference (ICI) reduction or cancellation in an orthogonal frequency domain multiplexing (OFDM) receiver. A first and a second stage of ICI cancellation may be performed before inputting an estimated transmitted data carrier for forward error correction. Forward error correction may include a signal re-correction and reconstruction of the estimated transmitted data carrier prior to a further stage of ICI cancellation. | 10-17-2013 |
20140029708 | DYNAMIC OPTIMIZATION OF CARRIER RECOVERY PERFORMANCE FOR COMMUNICATION SYSTEMS - Apparatuses, systems, and methods are directed to maintaining optimal carrier tracking performance in view of operating conditions that prevail. Such configurations employ a phase lock loop that configured to generate an estimated phase error value, a variance module configured to calculate a phase noise variance based on the estimated phase error value, and a loop control bandwidth module that calculates a loop bandwidth value based on a detected lower phase noise variance, generates modified loop filter values in accordance with the calculated loop bandwidth value, and updates the phase lock loop with the modified loop filter values. During subsequent iterations, the modified loop filter values are incrementally adjusted along a particular direction until the phase noise variance increases at which point the modified loop filter values are incrementally adjusted in an opposite direction to converge on an optimal loop bandwidth value. | 01-30-2014 |
20140219324 | ORTHOGONAL FREQUENCY DIVISION MULTIPLEX (OFDM) DEMODULATOR WITH IMPROVED CYCLIC AMBIGUITY RESOLUTION - A system according to one embodiment includes a demodulator configured to receive an OFDM modulated signal over a channel, the signal including a sequence of symbols, each of the symbols including one or more pilot carriers and one or more data carriers; a time filtering and interpolation circuit coupled to the demodulator, the time filtering and interpolation circuit configured to estimate the frequency response of the channel based on time filtering and interpolation of the pilot carriers; a phase slope correction circuit configured to apply each of a plurality of phase slope corrections to the frequency response and to the data carriers; a frequency filtering and interpolation circuit configured to calculate frequency response estimates of the channel at data carrier frequencies based on frequency filtering and interpolation of the phase slope corrected frequency response; an equalization circuit configured to equalize the phase slope corrected data carriers based on the calculated frequency response estimates; an error calculation circuit configure to calculate the mean square error between the equalized data carriers and a nearest QAM constellation point; and an iterative phase slope optimization circuit configured to select the phase slope correction associated with the minimum of the mean square errors, wherein the selected phase slope resolves the cyclic ambiguity. | 08-07-2014 |
Patent application number | Description | Published |
20140036157 | APPARATUS, SYSTEMS AND METHODS UTILIZING ADJACENT-CHANNEL POWER DEPENDENT AUTOMATIC GAIN CONTROL FOR DIGITAL TELEVISION DEMODULATION - An embodiment of the present invention provides a method for digital television demodulation, comprising using adjacent-channel power dependent automatic gain control (AGC) for the digital television demodulation, wherein an AGC technique takes into account a total power as well as power of adjacent channels to control gain of a gain control amplifier. | 02-06-2014 |
20140064419 | APPARATUS AND METHOD FOR IMPROVING OFDM RECEIVER PERFORMANCE IN THE PRESENCE OF NARROWBAND INTERFERERS - In an Orthogonal Frequency Division Multiplex (“OFDM”) system, the problem of an interferer reducing the signal-to-noise ratio of a signal can be mitigated by generating an interferer-correction signal and subtracting it from the signal to be processed. The amplitude, frequency and phase of the interferences are determined first. The frequency is estimated by averaging the squared-magnitude of multiple FFTs of the incoming signal and then locating the spectral peaks. The phase and amplitude may be estimated from this FFT outputs or through a process of correlation in the time domain. The interferer-correction signal is generated from the estimated amplitude, frequency, and phase. The correction to be subtracted from the main signal in order to reduce the effect of the interference may be generated in the time or frequency domain. The subtraction of the correction may also be implemented in the time or frequency domains. | 03-06-2014 |
20140119420 | METHODS AND SYSTEMS TO MITIGATE IMPULSE INTERFERENCE - Methods and systems to mitigate impulse interference in an OFDM QAM signal. A per-symbol noise measure, or quality measure (QM) is computed for a symbol k as a MSE of distances between carriers in the symbol and points of corresponding QAM constellations. MSE(k) is averaged over multiple symbols to compute a background signal QM, AVG_MSE(k). If MSE(k) exceeds AVG_MSE(k) by a moderate amount, symbol k may be moderately affected by impulse interference, and per-carrier SNR estimates are downgraded for all data carriers in symbol k, prior to LLR computation. SNR downgrading may be linear or step-wise based on an extent to which MSE(k) exceeds AVG_MSE(k). If MSE(k) exceeds AVG_MSE(k) by a significant amount, symbol k may be significantly affected by impulse interference, and LLRs may be set to indicate that all data carriers are erased in symbol k. | 05-01-2014 |
20140169188 | SYSTEMS AND METHODS FOR IMPLEMENTING PEAK-TO-AVERAGE POWER RATIO REDUCTION FOR OFDMA MODULATION - A system and method are provided for implementing a peak-to-average power ratio (PAPR) reduction scheme for Orthogonal Frequency-Division Multiple Access (OFDMA) modulation. A unique PAPR reduction scheme for OFDMA modulation for systems operated according to a DOCSIS standard achieves results similar to those attributable to tone reservation schemes in a manner that does not negatively affect an amount of available data capacity, particularly in implementations with limited numbers of subcarriers. The disclosed systems and methods are particularly adaptable to next generation cable gateways and/or next generation cable modems. These next generation cable gateways and/or cable modems may find particular utility in advanced hybrid fiber/coaxial cable systems. The adaptable cable gateways/modems may include a cable gateway system-on-chip (SOC) configuration. The disclosed schemes may be applicable to OFDM modulation. For OFDM, however, the known tone reservation algorithms also may be employed. | 06-19-2014 |
20140169434 | METHOD AND APPARATUS FOR PHASE NOISE MITIGATION - An approach is provided to mitigate phase noise by correcting common phase error and inter-carrier-interference in a received signal. The approach involves determining a received signal includes phase noise comprising at least a common phase error component and an inter-carrier-interference component. The approach also involves causing the common phase error to be corrected based on one or more pilot carriers. The approach further involves causing an estimate of a main signal component to be subtracted from the one or more pilot carriers. The approach additionally involves determining a sequence of estimated coefficients of a multiplicative phase noise sequence. The approach also involves causing the inter-carrier-inference to be corrected by processing the multiplicative phase noise sequence using the sequence of estimated coefficients. The approach further involves causing an equalized data signal to be output based on the corrected common phase error and the corrected inter-carrier-interference. | 06-19-2014 |
20140185657 | SYSTEMS AND METHODS FOR IMPLEMENTING SOFT-DECISION REED-SOLOMON DECODING TO IMPROVE CABLE MODEM AND CABLE GATEWAY PERFORMANCE - A system and method are provided for implementing a soft Reed-Solomon (RS) decoding scheme, technique or algorithm to improve physical layer performance in cable modems and cable gateways. At 1024-QAM, a receiver is provided in which a signal to noise ratio is reduced by at least about 1 dB relaxing design considerations and specifications for other components in the system including for the tuner. A soft-RS-symbol generation scheme is provided to enable soft-input RC decoding in a forward error correction (FEC) module connected to a QAM demodulator. The RS decoding scheme is implemented without significantly complicating hardware or processing overhead. A typical receiver hardware requirement in an FEC module to implement the disclosed scheme may be comparatively modest, e.g., on an order of approximately 50K gates. | 07-03-2014 |
20140211889 | ORTHOGONAL FREQUENCY DIVISION MULTIPLEX (OFDM) RECEIVER WITH PHASE NOISE MITIGATION AND REDUCED LATENCY - A system according to one embodiment includes a demodulator configured to receive an orthogonal frequency division multiplexed (OFDM) modulated signal comprising a current symbol and a sequence of previous symbols, each of the symbols comprising one or more pilot sub-carriers and one or more data sub-carriers; a phase angle computation circuit coupled to the demodulator, the phase angle computation circuit configured to compute a first mean, the first mean computed from the phase angle of one or more of the pilot sub-carriers of a predetermined number of the previous symbols; a predictive filter circuit coupled to the phase angle computation circuit, the predictive filter circuit configured to compute a second mean, the second mean estimating the phase angle of one or more sub-carriers of the current symbol, the estimation based on the first mean; and a phase noise cancelling circuit coupled to the predictive filter circuit, the phase noise cancelling circuit configured to correct the phase of one or more sub-carriers of the current symbol based on the second mean. | 07-31-2014 |
20140247782 | Configurable Constellation Mapping to Control Spectral Efficiency Versus Signal-to-Noise Ratio - Mixed mode constellation mapping to map a data block to a block of sub-carriers based on a configurable set of one or more constellation mapping schemes, and corresponding mixed mode least likelihood ratio (LLR) de-mapping based on the configurable set of one or more modulation schemes. The set may be configurable to include multiple modulation schemes to provide to a SEvSNR measure that is a non-weighted or weighted average of SEvSNR measures of the multiple modulation schemes. Mixed mode constellation mapping may be useful be configurable to control spectral efficiency versus SNR (SEvSNR) over a range of SNR with relatively fine SNR granularity, and may be configurable to control SEvSNR over a range of SNR at a fixed FEC code rate, which may include a highest available or highest permitted code rate. | 09-04-2014 |
20140247803 | Block-Based Time-Frequency Interleaving and De-Interleaving - Block-based interleaving to process a block of sub-carriers as a two-dimensional array defined by a frequency dimension and a time dimension. For each symbol of the array a cell is selected at each frequency index of the array in a diagonal wrap-around fashion. The array may be traversed with a modulo-based index computed as a function of an incrementing frequency index, a symbol index, and a modulus defined by a depth of the array. Cells may be selected as indicated by the frequency and time indices, and/or as indicated by a bit-reversed representation of the frequency index and/or the time index. A block interleaver may be configured to time interleave without impacting frequency, or interleave in time and frequency. Frequency interleaving may performed with the bit-reversed representation of the frequency index. | 09-04-2014 |