Abstract: An exciter matching circuit (125), interstage matching circuit (134), and harmonic filter matching circuit (140) match impedances at the input to a two-stage power amplifier (130), between the first stage (132) and the second stage (136) of the power amplifier (130), and at the output of the power amplifier (130) for more than one frequency band of interest. In a GSM/DCS dual band radiotelephone (101), the matching circuits (124, 134, 140) provide low return loss at 900 MHz when the dual band transmitter (110) is operating in the GSM mode. The harmonic filter matching circuit (140) also filters out signals at 1800 MHz, 2700 MHz, and high order harmonics. When the dual band transmitter (110) is in DCS mode, however, the matching circuits (124, 134, 140) provide a low return loss at 1800 MHz and filter out signals at 2700 MHz and harmonics of 1800 MHz.

Abstract: An exciter matching circuit (125), interstage matching circuit (134), and harmonic filter matching circuit (140) match impedances at the input to a two-stage power amplifier (130), between the first stage (132) and the second stage (136) of the power amplifier (130), and at the output of the power amplifier (130) for more than one frequency band of interest. In a GSM/DCS dual band radiotelephone (101), the matching circuits (124, 134, 140) provide low return loss at 900 MHz when the dual band transmitter (110) is operating in the GSM mode. The harmonic filter matching circuit (140) also filters out signals at 1800 MHz, 2700 MHz, and high order harmonics. When the dual band transmitter (110) is in DCS mode, however, the matching circuits (124, 134, 140) provide a low return loss at 1800 MHz and filter out signals at 2700 MHz and harmonics of 1800 MHz.

Abstract: An exciter matching circuit (125), interstage matching circuit (134), and harmonic filter matching circuit (140) match impedances at the input to a two-stage power amplifier (130), between the first stage (132) and the second stage (136) of the power amplifier (130), and at the output of the power amplifier (130) for more than one frequency band of interest. In a GSM/DCS dual band radiotelephone (101), the matching circuits (124, 134, 140) provide low return loss at 900 MHz when the dual band transmitter (110) is operating in the GSM mode. The harmonic filter matching circuit (140) also filters out signals at 1800 MHz, 2700 MHz, and high order harmonics. When the dual band transmitter (110) is in DCS mode, however, the matching circuits (124, 134, 140) provide a low return loss at 1800 MHz and filter out signals at 2700 MHz and harmonics of 1800 MHz.

Abstract: An exciter matching circuit (125), interstage matching circuit (134), and harmonic filter matching circuit (140) match impedances at the input to a two-stage power amplifier (130), between the first stage (132) and the second stage (136) of the power amplifier (130), and at the output of the power amplifier (130) for more than one frequency band of interest. In a GSM/DCS dual band radiotelephone (101), the matching circuits (124, 134, 140) provide low return loss at 900 MHz when the dual band transmitter (110) is operating in the GSM mode. The harmonic filter matching circuit (140) also filters out signals at 1800 MHz, 2700 MHz, and high order harmonics. When the dual band transmitter (110) is in DCS mode, however, the matching circuits (124, 134, 140) provide a low return loss at 1800 MHz and filter out signals at 2700 MHz and harmonics of 1800 MHz.

Abstract: A unique method and apparatus modifies the load impedance at the output of a power amplifier by varying a voltage variable capacitor (VVC) (310) to maximize the efficiency of the power amplifier (304). A comparator (509) generates amplifier control signal (211) based upon a detected power output signal (216) and a reference signal. In addition to providing power control, the control signal is also coupled to a VVC circuit (506) to control the output impedance of the power amplifier. In an alternate embodiment, a separate VVC control signal (527) based upon a comparison of the power control signal and the battery voltage is coupled to a VVC. In another alternate embodiment, a second VVC can be coupled in parallel to the first VVC. The second VVC is preferably controlled by a signal (805) based upon the current in the power amplifier.

Abstract: A method and apparatus enables a communication device (100) to operate in multiple bands, such as GSM 900 MHz, DCS 1800 MHz, and DCS 1900 MHz bands, by eliminating the need for a mixer for each band. In a dual band GSM/DCS 1800 radiotelephone, for example, the local oscillator (LO) injection frequencies for both GSM and DCS bands are provided to a mixer (234) through the use of combination filters (222, 246). Thus, the duplexing and matching requirements to the mixer input are simplified and the signal losses are minimized. The common output ports of the GSM RX/LO combination filter and DCS RX/LO combination filter are duplexed to the input of the mixer. Also, the input impedance matching of the mixer is designed to match the impedance for the received signals in each band, as well as provide an RF trap at the IF frequency. The match at the output of the mixer is designed to match the impedance of the IF filter and provides a low impedance to RF input frequencies.

Abstract: A transmitter VCO (204) includes nodes for receiving a band selector voltage for altering the base-emitter capactance of a transistor to enable the VCO to act as an oscillator in the appropriate band, and for altering the resonator capacitance to change the resonant frequency of the oscillator. The method and apparatus enables oscillation in different frequency bands for dual mode communication devices.

Abstract: A unique method and apparatus modifies the load impedance at the output of a power amplifier by varying a voltage variable capacitor (VVC) (310) to maximize the efficiency of the power amplifier (304). A comparator (509) generates amplifier control signal (211) based upon a detected power output signal (216) and a reference signal. In addition to providing power control, the control signal is also coupled to a VVC circuit (506) to control the output impedance of the power amplifier. In an alternate embodiment, a separate VVC control signal (527) based upon a comparison of the power control signal and the battery voltage is coupled to a VVC. In another alternate embodiment, a second VVC can be coupled in parallel to the first VVC. The second VVC is preferably controlled by a signal (805) based upon the current in the power amplifier.