Abstract: Method and apparatus for controlling the timing of the sampling of signals and signal amplitude in a PRML read channel. A VCO generates a read clock and a clock generator connected to the VCO generates even and odd clock signals corresponding to even and odd cycles of operation of the VCO. Serially connected even sample and hold circuits respond to clock signals to store samples of the read channel signal taken during successive odd cycles and serially connected odd sample and hold circuits store samples taken during successive even cycles. Comparator circuits compare the samples taken in each cycle to reference signals and the comparisons are clocked through two stage, even and odd shift registers to provide estimates of the presence or absence of nonzero samples for each even and odd cycle.

Abstract: A selective call radio frequency (RF) communication device (105) includes a receiver (203) for receiving and converting an RF signal into a converted signal. A controller (206) generates binary message information, a synchronization command signal and an address detection signal. An alert device (207) indicates the receipt of the message information. A frequency counter (427) measures the frequency of the converted signal and also determines the associated binary state of the binary message information. A measurement memory (439) stores the converted signal frequency measurements. The frequency control generator (440) generates a frequency control signal in response to the synchronization command signal being generated. The frequency control signal is a function of the stored converted signal frequency measurements and the associated binary states.

Abstract: A complex signal correlator (106) and method therefor for correlating, at the multiple points in time, complex sampled (111) and reference (112) signals to produce a complex correlation signal (113). A relationship between the location of the reference signal (112) relative to the real and imaginary axes (301 and 302) is determined. The sampled signal (111) is processed responsive to the determined location, relative to the axes (301 and 302), of the reference signal (112) to produce real and imaginary processed components (210 and 211). The complex correlation signal (113) is produced responsive to adding (202-205) combinations of the real and imaginary processed components (210 and 211). Substituting adders (202-205) in the present invention for multipliers in the prior art complex signal correlators along with processing the sampled signal ( 111) significantly reduces the complexity of the complex signal correlator (106).

Abstract: A digital data transmission system includes a transmitter connected to a receiver by a twisted pair. A digital transversal filter, included in the transmitter, supplies output signals to one of four resistor banks, as determined by an automatic selection system that selects one of the resistor banks based on the measured transmission characteristics of the twisted pair. The output signals are weighted by the resistors of the selected resistor bank, summed, and used to generate the transmitted pulse. The values of the resistors of each resistor bank are chosen to shape the transmitted pulse for a respective length of transmission medium so that, after distortion by the transmission medium, the transmitted pulse more nearly corresponds to the ideal pulse shape for which the receiver is designed.