Patent application number | Description | Published |
20100144303 | METHOD AND APPARATUS FOR REMOVING DC OFFSET IN A DIRECT CONVERSION RECEIVER - A method and apparatus for correcting direct current (DC) offset errors of a received signal in a direct conversion receiver (DCR) are provided. DC offset correction algorithms are incorporated into the DCR, each algorithm being optimized for a particular receive signal operating environment. The DC offset correction algorithms remove DC offset errors in baseband In-phase and Quadrature-phase signals received within the direct conversion receiver baseband signal path. Individual DC offset correction algorithms are selected for use as determined by a signal quality estimator component. A DC offset correction component of the direct conversion receiver determines an appropriate DC offset correction algorithm suited for a particular operating environment. A criterion for a signal quality estimate is set to control transitioning between DCOC algorithms. A dual threshold strategy may be adopted to transition between one DC offset correction algorithm and another DC offset correction algorithm to provide hysteresis. | 06-10-2010 |
20110026643 | CARRIER DETECT SYSTEM, APPARATUS AND METHOD THEREOF - A method of detecting an on-channel signal and synchronizing signal detection with correcting for DC offset errors in a direct conversion receiver is presented. A received signal is digitized, and a state machine operates to detect the presence of an on-channel signal. If the signal is not detected, a mixed mode training sequence is initiated in which the DC offset errors in both an analog and digital received signal path are corrected. While training, processing of the digitized samples by a digital signal processor and a host controller is suspended (while they are put into battery save mode) and the gain provided to subsequently received signals is minimized. The DC offset correction circuitry is bypassed and put into battery save mode at predetermined periods when DC offset correction is not performed. | 02-03-2011 |
20120028594 | METHOD AND APPARATUS FOR IMBALANCE-FREE FM DEMODULATION IN DIRECT CONVERSION RADIO RECEIVERS - An apparatus and method for demodulating an FM RF signal is presented. An Adaptive Differentiate Cross Multiply (ADCM) system in which the energy estimate of the desired on-channel RF is generated using adaptive filtering. The adaptive filter includes low pass filtering of the instantaneous energy estimate. The bandwidth of the LPF is adjusted in real time based on the received signal strength energy estimate, the periodicity of any changes in the energy estimate, AGC setting for the receiver, and/or the type of sub-audible signaling applied to the RF signal if known. After the bandwidth is set, the optimum filtered energy estimate is applied to the system to demodulate the received information free from distortion artifacts associated with IQ imbalance. A normalized signal in the ADCM system is clipped by a limiter whose clipping threshold is equal to a maximum gain of differentiators in the ADCM system. | 02-02-2012 |
20120171975 | METHOD FOR CONTROLLING PEAK-TO-AVERAGE POWER RATIO OF SINGLE CARRIER FDMA SYSTEM - A method for controlling peak-to-average power ratio prior to amplification by a power amplifier is provided. The peak sample of a signal is predicted, window length is adjusted based on the peak width around the peak sample or subcarriers used to transmit the signal, and the window is subsequently used to clip the samples. A peak suppression window may be applied prior to predicting the peak sample when a set number of samples exceed a predetermined threshold. Window clipping may be deactivated if interference and throughput of the power amplifier is detrimentally affected. A pulse shaping filter may be optimized based on the window clipping to control transmitted signal characteristics. Various thresholds used in the prediction may be initially based on system design and power amplifier linearity and then dynamically adjusted based on an estimation of active subcarriers or of interferers present in the communication system. | 07-05-2012 |
20140146683 | METHOD AND APPARATUS FOR CONFIRMING DELIVERY IN A MULTI-CHANNEL RECEIVING APPARATUS - An apparatus for simultaneously receiving incoming messages on at least two channels in a multi-channel device, wherein a first incoming message is received on a first channel of the at least two channels according to a first protocol. Responsive to receiving the first incoming message, outgoing messages are transmitted on the first channel while the incoming messages are simultaneously received on a second channel. The outgoing messages to be sent according to the first protocol are queued in a transmitter. The transmitter also monitors at least one data stack that is used for transmitting messages according to a second protocol for transmit opportunities. Responsive to detecting a transmit opportunity, the transmitter transmits an optimal number of the outgoing messages within the duration of the transmit opportunity. The outgoing messages are transmitted on the first channel without affecting incoming messages received on the second channel. | 05-29-2014 |