Motorola Corporation

Universal Data Systems, Inc.

Mickey C Rushing

Richard Lee Goodson

Lee T Gusler

Gary D Hunt

Steven R Blackwell

Jack L Hayes

An apparatus and method for a data communications device such as a modem (100, 101) to determine transmit power levels for data transmission and reception, from a received probe signal. The various embodiments utilizing a processor (108) or a digital signal processor (106) receive a probe signal, transmitted at two different power levels, which also typically contains noise and other distortions. The various method and apparatus embodiments then determine average signal levels (501), average noise levels (503), and a set of signal to distortion ratios corresponding to combinations of symbol rates and carrier frequencies. Parameters such as the receive signal power (509), the harmonic content (507), the proportional noise (511), and a signal to distortion ratio threshold (513) are utilized to determine a transmit power level (515).

Method and apparatus for determining transmit power levels for data

An apparatus and method are provided for a data communications device, such as a modem (100, 101) or facsimile machine, to detect and discriminate various amplitude modulated signals, such as an ANS signal of the ITU V.25 protocol and an ANSam signal of the ITU V.8 protocol, which may be subject to impulse distortions (FIG. 5B). The apparatus and method embodiments band pass filter (204) an incoming signal at a first frequency, and dynamically limit (208) any impulse distortions of the incoming signal to a limit threshold (211). The limit thresholds may be dynamically determined by rectifying (209) and low pass filtering (210) the band pass filtered signal to determine a low frequency average magnitude level of the incoming signal, with the limit thresholds set as a predetermined variance from this low frequency average magnitude level. The various frequency components of the amplitude modulated signal may then be discriminated by rectifying (215) and band pass filtering (217) at a second frequency, such as the frequency of the amplitude modulating component. Various detectors (205, 206) then determine the type of information present in the incoming signal, such as whether the signal is an ANS signal or an ANSam signal.

Apparatus and method for detecting and discriminating various signal

An apparatus and method for a data communications device, such as a modem (100, 101), to determine a symbol rate and carrier frequency combination, from a received probe signal, for optimizing a bit rate for data transmission and reception. The various embodiments utilizing a processor (108) or a digital signal processor (106) receive a probe signal, which also typically contains noise and other distortions. The various method and apparatus embodiments then determine signal to distortion ratios for a plurality of symbol rate and carrier frequency combinations (820), and other optimization parameters, such as channel characteristics and attenuation distortion parameters (830). These optimization parameters are then utilized to determine an optimal symbol rate and carrier frequency (840).

Apparatus and method for determining a symbol rate and a carrier

An apparatus and method for a data communications device such as a modem (100, 101) to determine carrier frequency offset and timing frequency offset, from a received probe signal. The various embodiments utilizing a processor (108) or digital signal processor (106) receive first and second sets of a transmitted probe signal having known characteristics, and determine a set of phase differences for the tones comprising the probe signal (702, 703, 704, 705). The various method and apparatus embodiments then form a linear approximation from the set of phase differences to determine the carrier frequency offset and the timing frequency offset (706). In the preferred embodiments, the linear approximation is formed from a minimization of a least square error estimate proportionally weighted by either signal to noise ratios or normalized, average amplitudes of the set of tones of the received probe signal.

Apparatus and method for determining carrier frequency offset and timing

An apparatus and method for a data communications device such as a modem (100) to generate initial coefficient values for an equalizer (440) from a transmitted training signal received via a channel, in which the transmitted training signal has predetermined characteristics. The apparatus and method embodiments of the invention determine a finite impulse response characteristic of the inverse frequency response of the channel based on a received training signal and the transmitted training signal (610). In the various embodiments, an energy index, a magnitude index, and an offset index are generated and combined with an equalizer length index to select a sequence of initial coefficient values for the equalizer (630, 640, 650).

Method and apparatus for initializing equalizer coefficents using

The present invention provides a novel method, device, digital signal processor and modem for efficiently determining and tracking a phase roll of a far end echo by utilizing a novel phase error generator and a novel, efficient replica generator. The efficient replica generator utilizes a uniquely positioned phase rotator to facilitate replication of the far end echo. A unique combination of a Hilbert phase splitter and a conjugate Hilbert phase splitter together with a rectangular to polar converter enable the novel phase error generator to provide a reliable phase error.

Method, device, DSP and modem for efficient echo canceler phase roll

A modem (100) includes an equalizer for equalizing a received signal (10) for amplitude jitter distortion. The received signal includes modulated symbols based on a predetermined constellation of points, each point representing a symbol. The modem first extracts a modulated symbol to provide an extracted symbol, R(k), which includes amplitude jitter distortion. The modem then identifies a signal point P.sub.n (k) of the predetermined constellation corresponding to the extracted symbol. Further, the modem determines an error signal (76) based on the amplitude jitter distortion, and then uses the error signal to compensate subsequent extracted symbols for the amplitude jitter distortion.

Apparatus and method for equalizing for amplitude jitter

A modem receiver includes an echo canceller (122), the echo canceller including a near-end echo canceller (128) and a far-end echo canceller (130). The echo canceller also includes a phase jitter tracker (154) arranged to track and generate a phase jitter component associated with the far-end echo.

Modem with echo cancellation

A modem with nonlinear equalization (100) receives a signal (101) that includes linear and nonlinear distortion. The modem includes a multiplier (107) that frequency shifts the signal to form a baseband signal, which is then sampled by an A/D converter (114) to provide a complex receiver input sample, R(n). A first equalizer (117) equalizes R(n) to form a first equalized result (n). A nonlinear generator (129) forms .vertline.R(n).vertline..sup.2 R(n), which is then equalized by a second equalizer (133) to form a second equalized result (n). A summing device (121) combines the first equalized result (n) with the second equalized result (n) to form a composite equalized result (n). The modem includes a data recovery circuit (125) that determines a received signal point (n) based on the composite equalized result (n) and a predetermined constellation.

Growing community of inventors

Harvest, AL, United States of America

Mickey C Rushing