Robert L Lyall

Author:

Robert Lyall

ISBN #:

0405030460

US Patent:

60262850, Feb 15, 2000

Filed:

Mar 27, 1997

Appl. No.:

8/825270

Inventors:

Robert L. Lyall - Loganville GA
Richard I. Bain - Suwanee GA

Assignee:

Oki Telecom, Inc. - Suwanee GA

International Classification:

H04B 106

US Classification:

4552491

Abstract:

A variable attenuator circuit provides variable attenuation responsive to received signal strength in a receiver to reduce intermodulation (IM) distortion. In a dual-mode frequency modulation/code division multiple access (FM/CDMA) cellular telephone implementation, the variable attenuator circuit decreases IM distortion by variably attenuating received radio frequency (RF) signals before an initial RF amplification stage to reduce the level of undesirable frequency mixing products. The variable attenuator circuit is turned on (activated) and off (deactivated) at a single, relatively low, input power level. An attenuator enable signal is also supplied from a logic unit of the mobile station to enable operation of the variable attenuator circuit throughout operation in a digital mode. Thus, while enabled, as soon as the input signal power level rises above a defined activation threshold amount, the variable attenuator circuit is activated and begins attenuating the input signal responsive to input signal power levels based upon a received signal strength indication output from a separate automatic gain control circuit. After the attenuation begins gradually, thus avoiding excessive chattering without the need for hysteresis, the attenuation rises non-linearly and continuously to quickly mitigate IM distortion problems.

US Patent:

61049190, Aug 15, 2000

Filed:

Jun 17, 1999

Appl. No.:

9/334967

Inventors:

Robert L. Lyall - Loganville GA
Richard I. Bain - Suwanee GA

Assignee:

Oki Telecom, Inc. - Suwanee GA

International Classification:

H04B 106

US Classification:

4552491

Abstract:

A variable attenuator circuit provides variable attenuation responsive to received signal strength in a receiver to reduce intermodulation (IM) distortion. In a dual-mode frequency modulation/code division multiple access (FM/CDMA) cellular telephone implementation, the variable attenuator circuit decreases IM distortion by variably attenuating received radio frequency (RF) signals before an initial RF amplification stage to reduce the level of undesirable frequency mixing products. The variable attenuator circuit is turned on (activated) and off (deactivated) at a single, relatively low, input power level. An attenuator enable signal is also supplied from a logic unit of the mobile station to enable operation of the variable attenuator circuit throughout operation in a digital mode. Thus, while enabled, as soon as the input signal power level rises above a defined activation threshold amount, the variable attenuator circuit is activated and begins attenuating the input signal responsive to input signal power levels based upon a received signal strength indication output from a separate automatic gain control circuit. After the attenuation begins gradually, thus avoiding excessive chattering without the need for hysteresis, the attenuation rises non-linearly and continuously to quickly mitigate IM distortion problems.

US Patent:

56970811, Dec 9, 1997

Filed:

Dec 13, 1995

Appl. No.:

8/571511

Inventors:

Robert L. Lyall - Loganville GA
Richard I. Bain - Suwanee GA

Assignee:

Oki Telecom, Inc. - Suwanee GA

International Classification:

H04B 106

US Classification:

4552491

Abstract:

A variable attenuator circuit provides variable attenuation responsive to received signal strength in a receiver to reduce intermodulation (IM) distortion. In a dual-mode frequency modulation/code division multiple access (FM/CDMA) cellular telephone implementation, the variable attenuator circuit decreases IM distortion by variably attenuating received radio frequency (RF) signals before an initial RF amplification stage to reduce the level of undesirable frequency mixing products. The variable attenuator circuit is turned on (activated) and off (deactivated) at a single, relatively low, input power level. An attenuator enable signal is also supplied from a logic unit of the mobile station to enable operation of the variable attenuator circuit throughout operation in a digital mode. Thus, while enabled, as soon as the input signal power level rises above a defined activation threshold amount, the variable attenuator circuit is activated and begins attenuating the input signal responsive to input signal power levels based upon a received signal strength indication output from a separate automatic gain control circuit. After the attenuation begins gradually, thus avoiding excessive chattering without the need for hysteresis, the attenuation rises non-linearly and continuously to quickly mitigate IM distortion problems.

US Patent:

6236863, May 22, 2001

Filed:

Mar 17, 1998

Appl. No.:

9/042759

Inventors:

Anthony B. Waldroup - Suwanee GA
Robert L. Lyall - Loganville GA
Richard I. Bain - Lilburn GA

Assignee:

Oki Telecom, Inc. - Suwanee GA

International Classification:

H04B 138

US Classification:

455522

Abstract:

An output power control system prevents saturation by limiting total output power and maintaining closed loop responsiveness for a radio telephone having closed loop and open loop gain control systems. The output power control system determines when total output power exceeds an output power trigger level and automatically enters a saturation prevention mode whereby total output power is reduced through modification of a closed loop power control register. In one embodiment, an output detector and an output comparator continuously monitor output power, and in another embodiment, an analog-to-digital converter samples output power levels. Saturation prevention processes of various preferred embodiments include, through continual monitoring, edge-triggered interrupt servicing, and level-triggered interrupt servicing, subsequently modifying the closed loop power control register to decrease the closed loop output power control portion of the total output power until the output power falls below the output trigger level. A saturation prevention method of yet another embodiment includes maintaining the closed loop power control register at a constant level unless a decrease in received signal strength is detected, in which case the closed loop power control register is modified to compensate for an increased open loop component of the total output power.