Abstract: Oscillator circuits that support highly accurate fixed frequency generation over process, voltage and temperature (PVT) variations include a reference voltage generator, which is configured to generate a reference voltage across a resistor (e.g., high precision poly-resistor) therein. An auto-zeroing comparator is provided, which is configured to generate a differential clock signal (e.g., Ck, Ckb) at an output thereof. First and second switched capacitor circuits are further provided, which include matching first and second trim capacitors therein, respectively. The first and second switched capacitor circuits are configured to periodically drive respective first and second input terminals of the comparator at a first voltage level in an alternating back-and-forth sequence, in response to the reference voltage and a pair of switching signals derived from the differential clock signal.

Abstract: A fractional-N frequency divider includes a half-integer frequency divider and a duty cycle adjustment circuit. The half-integer frequency divider includes a multi-modulus divider containing a cascaded chain of div2/3 cells, which is responsive to a multi-bit modulus control signal, and a phase control circuit configured support half-integer frequency division by the multi-modulus divider, by providing an input terminal of the multi-modulus divider with a periodically phase-flipped input signal having a first frequency. The duty-cycle adjustment circuit is configured to generate a divider output signal with a 50% duty cycle in response to a periodic signal generated by the half-integer frequency divider.

Abstract: A spread spectrum cellular network (FIG. 1) mobile unit transmitter (30) that enables communication via protocols having different bandwidth (372) and baseband signal generation (260), the transmitter including a phase locked loop and an amplitude control loop.

Abstract: A spread spectrum cellular network (FIG. 1) mobile unit transmitter (30) that enables communication via protocols having different bandwidth (372) and baseband signal generation (260), the transmitter including a phase locked loop and an amplitude control loop.

Abstract: A dual-mode wireless telephone which is capable of operating on two different bands of frequencies. The dual-mode telephone having a single phase lock loop combined with a single local oscillator that can select between two frequencies in two widely spread output frequency bands such as the bands in the GSM and DCS standards. A switch in the phase lock loop selectively swaps an UP signal and a DOWN signal to achieve either a high side lock or a low side lock. When the phase lock loop is high side locked, a target frequency in a higher band of output frequencies is generated. When the phase lock loop is low side locked, a target frequency in a lower band of output frequencies is generated.