Abstract: Systems for controlling the frequency of the output signal of a controllable oscillator in a frequency synthesizer are provided. One such system comprises a controllable oscillator and a frequency control circuit. The controllable oscillator is configured to generate an output signal that has a predefined frequency. The controllable oscillator is also configured with a plurality of operational states that are controlled by the frequency control circuit. Each operational state of the controllable oscillator defines a distinct frequency for the output signal of the controllable oscillator. The frequency control circuit receives the output signal of the controllable oscillator and determines the distinct frequency for the output signal that best approximates the predefined frequency.

Abstract: This invention provides a charge pump biasing circuit that varies the bias when the phase lock loop changes frequency to improve the settling time of the phase lock loop. During a frequency change, the charge pump output current taper off as the phase lock loop approaches the desired frequency. The charge pump biasing circuit allows the phase lock loop to change frequencies faster and minimizes spurious sideband noise once the loop has settled.

Abstract: A closed loop power amplifier control system is provided. A self-adapting driver circuit is used to drive the power amplifier in accordance with the feed back error signal. The driver circuit compensates for non-linearities of the power amplifier.

Abstract: A system and method for minimizing power dissipation in a battery-operated mobile unit by adaptively controlling a voltage converter to provide a variable power supply voltage to a transmitter. In the preferred embodiment, the voltage converter is coupled to receive a source voltage from a battery, and is coupled to provide operating power to the transmitter or the power amplifier. The voltage converter is also coupled to receive a control signal from a controller, which adaptively activates the voltage converter to transform the source voltage to a converted voltage, or deactivates the voltage converter so as to directly apply the source voltage to the transmitter. Power dissipation is therefore minimized when conversion functions of the voltage converter are deactivated when voltage conversion is unnecessary.

Abstract: A direct conversion receiver system is provided in which a first input signal at a first frequency is applied to a first input port of a multiplier, a second input signal at a second frequency equal to about {fraction (1/n)} times the first frequency, wherein n is an integer, is applied to a second input port of the multiplier. A first filter coupled to the first input port is configured to substantially filter out any leakage at the second frequency which may be present. A second filter coupled to the second input port is configured to substantially filter out any leakage at the first frequency which may be present. The multiplier is configured to produce a signal at an output port thereof which is derived from the product of the first and second signals. In one embodiment, the output is representative of the product of the filtered first signal and a multiplication factor which switches at n times the second frequency. The output of the multiplier is coupled to a third filter.

Abstract: A system for reducing internal interference in a radio-frequency (RF) receiver includes providing a plurality of time slots within a frame where the receiver is configured to receive external RF signals during a receive time slot within the frame. External RF signals are the prevented from reaching a front-end portion of the receiver and the receiver is activated, and a predetermined period of time is permitted to elapse to permit the receiver to settle. An interference data collection is performed during a period of time prior to a predetermined receive time slot where the data collected represents internally generated interference signals. The data collected during the interference data collection is processed to determine a bias value corresponding to the interference signals, and the receiver is then permitted to receive external RF signals during the predetermined receive time slot so that data is collected during the predetermined receive time slot.

Abstract: A differential oscillator based on a first Colpitts oscillator and a mirror image Colpitts oscillator that is coupled to the first Colpitts oscillator. This differential oscillator outputs differential voltage signals that are about 180 degrees out of phase. The differential oscillator may also be adapted to form a voltage controlled oscillator (VCO) such that the differential voltage signals output by the VCO can be varied. A transceiver for telecommunication devices such as cellular phones may use differential oscillators to generate a carrier signal on which a voice or data signal is modulated and the same differential oscillators to assist isolation of the voice or data signal from received signals.

Abstract: A method and apparatus for improving the sensitivity of a radio frequency (RF) receiver at certain frequencies suffering from co-channel interference. In the preferred embodiment, when a reference frequency, FREF, generates significant harmonics for a received RF signal in a selected channel, the reference frequency is varied or offset by a small amount, &Dgr;F. The harmonics of the offset reference frequency, F′REF=FREF±&Dgr;F, are thereby shifted away from the frequency of the received RF signal, thus reducing co-channel interference. The offset amount &Dgr;F is chosen such that the same injection frequency synthesized from FREF can still be synthesized from FREF±&Dgr;F by shifting N by an integer amount, preferably to N+1 or N−1. However, the invention encompasses shifting N by other integer amounts.

Abstract: A system and method for minimizing power dissipation in a battery-operated mobile unit by adaptively controlling a voltage converter to provide a variable power supply voltage to a transmitter. In the preferred embodiment, the voltage converter is coupled to receive a source voltage from a battery, and is coupled to provide operating power to the transmitter or the power amplifier. The voltage converter is also coupled to receive a control signal from a controller, which adaptively activates the voltage converter to transform the source voltage to a converted voltage, or deactivates the voltage converter so as to directly apply the source voltage to the transmitter. Power dissipation is therefore minimized when conversion functions of the voltage converter are deactivated when voltage conversion is unnecessary.

Abstract: A DC voltage power supply for a time division multiple access (TDMA) radio system is provided. The DC voltage power supply apparatus includes an AC signal source, a switching transistor, a controlling signal source, a voltage converter circuit, and a capacitor. The AC signal source provides an AC signal to the DC voltage power supply. The switching transistor is coupled to the clock for switching on and off the clock signal. The controlling signal source is coupled to the switching transistor for turning the switching transistor off during a transmission or reception period and for turning the switching transistor on during an idle period. The voltage converter circuit is coupled to the switching transistor and generates a DC output voltage from the AC signal. Finally, the capacitor is coupled to the voltage converter such that the capacitor is charged by the DC output voltage when the switching transistor is turned on and the capacitor holds the DC output voltage by discharging when the switch is turned off.

Abstract: A torsional-mode resonator is produced by using an extensional mode transducer on a piece of material such as a metal bar where the transducer lies at an angle between the longitudinal axis of the material and the transverse axis. Placing the midpoint of the transducer at approximately the midpoint of the material such as the bar, optimizes the torsional effect. Further optimization may be obtained by making the transducer in the shape of a rhomboid.