Motorola Corporation

Clinton C Powell, Ii

Chun-Ye Susan Chang

James Michael Keba

Christopher T Thomas

Stephen Rocco Carsello

Mahibur Rahman

James David Hughes

Joseph Boccuzzi

Robert K Schweickert

James Rodney Webster

Edgar Herbert Callaway, Jr

John Richard Oakley

Eric Thomas Eaton

Craig P Wadin

David L Brown

James G Mittel

Morris A Moore

Lu Chang

Jian-Cheng Huang

Hyuck M Kwon

David R Petreye

Edward K Lee

Ronald A Craig

Daniel A Morera

Richard C Bernhardt

Lorenzo Ponce De Leon

Mark L Servilio

Dalier J Ramirez

Carla J Maroun

David F Brown

James A Kimball

An automatic gain control (AGC) system () for a controlled gain receiver () includes a magnitude generator () and a gain corrector (). The magnitude generator () generates a binary voltage squared signal () having a binary value that is directly proportional to a recovered signal power of an intercepted signal (). The gain corrector () determines an adjustment of a gain control value () as a multiple of increments that are approximately 3 decibel (dB), by shifting () a reference threshold by one or more bits and comparing () the shifted reference threshold to the binary voltage squared signal. An initial setting of a state of a step attenuator () during a track mode () is determined during a warm up mode () by comparing the binary voltage squared signal () to two different thresholds (). A filter () accommodates a variety of bandwidths and symbol rates by settings of an accumulator () and scaler () that are included in the filter (). A received signal strength indicator function () of the controlled gain receiver () generates a low resolution or high resolution RSSI signal (), depending on the mode. The value of the low resolution RSSI signal () is directly proportional to the power of the intercepted signal ().

Digitized automatic gain control system and methods for a controlled gain receiver

A correlation demodulator unit () having gain normalization includes a correlation demodulator () for receiving a signal from a receiver (). The correlation demodulator has a plurality of correlators (C-C) corresponding to a plurality of N correlator outputs. A gain normalizer () is coupled to the correlation demodulator for accumulating symbol energy on a symbol by symbol basis for each of the plurality of correlator outputs based upon a current symbol decision providing at least an accumulated value within an accumulator () for the plurality of correlators and for normalizing the plurality of N correlator outputs using the accumulated value(s).

Method and apparatus for gain normalization of a correlation demodulator

An automatic gain control (AGC) system ( ) for a controlled gain receiver ( ) includes a magnitude generator ( ) and a gain corrector ( ). The magnitude generator ( ) generates a binary voltage squared signal ( ) having a binary value that is directly proportional to a recovered signal power of an intercepted signal ( ). The gain corrector ( ) determines an adjustment of a gain control value ( ) as a multiple of increments that are approximately 3 decibel (dB), by shifting ( ) a reference threshold by one or more bits and comparing ( ) the shifted reference threshold to the binary voltage squared signal. An initial setting of a state of a step attenuator ( ) during a track mode ( ) is determined during a warm up mode ( ) by comparing the binary voltage squared signal ( ) to two different thresholds ( ).

An automatic simulcast correction method ( ) for a selective call receiver ( ) includes the steps of measuring a received signal ( ) for a received signal strength indication measurement and then determining if a protocol indicates a simulcast signal ( ). If the received signal strength indication measurement is above a predefined threshold and the protocol indicates the simulcast signal, then the selective call receiver is optimized for simulcast delay spread distortion ( ). If the received signal strength indication measurement is below a predefined threshold or the protocol does not indicate the simulcast signal, then the selective call receiver is optimized for static sensitivity (

Method and apparatus for automatic simulcast correction for a correlation detector

A signal processor ( ) for recovering data symbols from a received signal includes matched filters ( ) for receiving and filtering a quadrature (Q) signal component of the received signal. A detector ( ) is coupled to the matched filters ( ) for selecting a filtered signal provided by one of the matched filters ( ) and for labeling the filtered signal according to a magnitude and phase of the filtered signal to provide a Q channel output flag. A Q channel symbol/sign decoder ( ) then processes the Q channel output flag to generate a Q channel magnitude variable and a polarity variable, and a symbol decoder ( ) coupled to the Q channel symbol/sign decoder ( ) generates a data symbol in accordance with the Q channel magnitude variable and the polarity variable.

Method and apparatus for recovering data symbols from a signal received by a radio communication device

A DC offset correction circuit ( ) provides DC offset correction within a receiver ( ) for receiving and processing a radio frequency signal ( ) within a radio communication system ( ). The DC offset correction circuit ( ) includes a feedback loop ( ) for shifting a digital signal ( ) by a programmable amount; and a coarse DC offset correction path ( ) coupled to the feedback loop ( ) for performing coarse DC offset correction.

DC offset correction scheme for wireless receivers

A full serial implementation of a M-level correlation based demodulator ( ) includes a two's complement, pass-through, zero-out complex conjugate multiplier element ( ), a boxcar filter ( ) coupled to the multiplier element, a complex magnitude approximater element ( ) coupled to the boxcar filter and a maximum value and index holding element ( ). The multiplier element reuses common products along an M-level of cross-correlation to reduce multiplication functions at a rate 2 times M faster than a sampling rate at an input of the demodulator.

Method and apparatus for efficient correlation detection

A method (,) of decoding a multi-level synchronous protocol having a first portion encoded as M/2-level signals and a subsequent portion encoded as M/2-level signal or M-level signals, wherein the M/2-level signals have expected larger than normal variation of deviations includes steps of decoding (,) the first portion using a biased mode which uses M correlators shifted (,) to adequately cover the frequency range of the expected larger than normal variation of deviations and determining (,) from decoding of the first portion whether the subsequent portion is the M/2-level or M-level signal. If a M/2-level signal is found, continue decoding (,) in the biased mode. If it's the M-level signal, then decoding continues in standard mode (,), which uses M correlators that are spaced in frequency to match M spectral deviations within a predetermined frequency range.

Method and apparatus for correlation detection of multi-level signals with non-standard deviations

A selective call receiver unit (,) capable of reducing data distortion and improving simulcast reception includes a selective call receiver (,), a demodulator (,) coupled to the selective call receiver and a circuit (,and,) coupled to the demodulator for reducing data distortion received at a selective call receiver. The circuit includes a detector (,) for detecting a simulcast signal, a filter (,) for windowing the symbol edge area in the simulcast signal providing a windowed symbol edge area, and a clipping circuit (,) for clipping the windowed symbol edge area.

Method and apparatus for reducing data distortion and improving simulcast reception

A method (900) and circuit (400) for automatic frequency correcting a frequency modulated (FM) digital signal determines a frequency offset value of the detected FM signal during a preamble portion of the FM digital signal, generates an offset corrected signal by removing the frequency offset value from a detected FM signal (440), and generates a frequency corrected signal (460). The frequency corrected signal is generated by selecting the offset corrected signal during the preamble portion, selecting the detected FM signal after the end of the preamble portion when a magnitude of the frequency offset value of the detected FM signal is below a predetermined threshold (445), and otherwise selecting the offset corrected signal after the end of the preamble portion.

Frequency shift modulation automatic frequency correction circuit and

A circuit (12) for symbol decision directed feedback synchronization includes a current synchonization clock (45) that provides an initial sampling point and selects a detector corresponding to a current symbol decision. The circuit further includes a plurality of detectors (31, 32, 33, and 34) including the detector corresponding to the current symbol decision, a buffer (736) for storing the output of the detector corresponding to the current symbol decision and a processor (300) for seeking within a predetermined window about the initial sampling point for an optimum phase value to provide an adjustment signal which is used by the processor to adjust a subsequent symbol's sychronization clock to provide an optimal sampling point.

Method and apparatus for accurate synchronization using symbol decision

A method (500) of baud detection in a communication device (700) includes the steps of sorting phase pulses among overlapping sets of time slots (502) and counting phase pulses within each of the overlapping sets of time slots creating corresponding counter values (504). Then, counter values are compared with predetermined thresholds (506-512), wherein a baud pass condition (570) is met when at least one counter has a counter value exceeding an upper threshold and wherein a counter N/2 positions away has a counter value below a lower threshold. The baud pass condition may he further conditioned on meeting the requirement that at least another counter value falls below a middle threshold.

Method and apparatus for baud detection in a communication device

A symbol synchronizer (10) for use in a communication device. The symbol synchronizer (10) comprises a sampling circuit (100) which samples the demodulated signal at a plurality of sampling events for each symbol period to generate three sample values at each sampling event. An eye pattern detector circuit (200) generates eye pattern characteristic information based on the three sample values, and outputs a symbol pulse in response to detecting eye pattern characteristic information consistent with a symbol center. A synchronization noise mask circuit (400) filters symbol pulses that occur during a predetermined period of time after a first symbol pulse is detected for each symbol period. A synchronization adjust circuit (500) generates a synchronization pulse during each symbol period at a particular instant of time during the symbol period based on a history of the occurrences of symbol pulses for a current symbol period and for prior symbol periods.

Symbol synchronizer based on eye pattern characteristics having variable

A circuit (350) for detecting simulcast channel conditions includes a symbol center averaging circuit (308) for providing a center count of excursions above and below at least a first predetermined threshold and for providing a moving average of the center count over a predetermined number of symbol periods and a symbol edge averaging circuit (310) for providing an edge count of excursions above and below at least a second predetermined threshold and for providing a moving average of the edge count over a predetermined number of symbol periods. Finally, the circuit further includes a comparison circuit (360) programmed to receive and compare the moving average of the center count and the moving average of the edge count to provide a control signal (380) for simulcast detection.

Method and apparatus for detecting simulcast channel conditions

A selective call receiver (800), including a receiver circuit (101) and a processor (810), is used for synchronizing an internal reference to symbol edges of a plurality of symbols in a multi-level radio signal transmitted by a radio communication system. To perform this function the processor (810) is adapted to cause the receiver circuit (101) to demodulate the multilevel radio signal to in-phase and quadrature signals (108, 106), convert the in-phase and quadrature signals (108, 106) to a sequence of state transitions representative of the plurality of symbols, detect at least one same state transition from the sequence of state transitions, and synchronize the internal reference to the at least one symbol edge of the plurality of symbols based on the at least one same state transition.

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Lake Worth, FL, United States of America

Clinton C Powell, Ii