Oki Telecom, Inc.

He Feng Wang

John P De Loe, Jr

Anthony B Waldroup

Ryo Yamazaki

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.

Saturation prevention system for radio telephone with open and closed

A circuit for connecting multiple signal paths within a multi-mode communication device includes a double balanced mixer circuit selectively functioning as a modulation switch during an unbalanced state. As applied to a transmit section of a CDMA/FM cellular telephone, a dual-function double balanced mixer circuit connects a CDMA IF signal path with an FM audio signal path. The double balanced mixer circuit includes a double balanced mixer connected through oscillator input to an external LC (inductor-capacitor) tank connected to both a PLL (phase lock loop) and an FM audio signal. One signal input of the double balanced mixer receives a CDMA low IF signal, while the other double balanced mixer signal input is connected to a microprocessor-controlled switch for selectively unbalancing the balanced mixer while in the FM mode of operation.

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Saitama, Japan

He Feng Wang