Abstract: Phase locked loop calibration system. Apparatus is provided for calibration of a phase-locked loop. The apparatus includes logic to calibrate an integration filter of the phase-locked loop, and logic to calibrate a charge pump current of the phase-locked loop, wherein the integration filter and charge pump current are calibrated to achieve a desired phase-locked loop performance level.

Abstract: A reference current generator configured to produce matched and isolated current references is disclosed. The reference current generator includes a primary reference generator operative to produce a first reference current. The reference current generator further includes a duplicate reference generator operative to produce a second reference current. An adjustment circuit coupled to the primary reference generator and the duplicate reference generator is configured such that the first reference current is substantially matched to and isolated from the second reference current.

Abstract: A direct synthesis transmitter. A very efficient and highly linear direct synthesis transmitter is provided that can be used to directly synthesize and transmit any type of modulated signal. The direct synthesis transmitter includes a phase-locked loop (PLL) with controls phase modulation plus an accompanying variable gain amplifier for amplitude modulation. Also included is a system to align the phase and amplitude modulation signals. A transmitter constructed in accordance with the present invention is very efficient and suitable for use in portable radio equipment.

Abstract: A system and method of operating a phase-locked loop frequency synthesizer is disclosed herein. The disclosed method includes defining a first set of operating parameters applicable to operation of a phase-locked loop of the synthesizer in a first mode and defining a second set of operating parameters applicable to operation of the phase-locked loop in a second mode. A first detection signal is generated so as to initiate transition of the phase-locked loop into the second mode. The method further includes configuring, at least in part in response to the first detection signal, the phase-locked loop to operate in accordance with the second set of operating parameters.

Abstract: An apparatus providing a phase/frequency modulation system is disclosed herein. The apparatus includes a first circuit configured to introduce an offset to center a signal applied to a VCO. The apparatus further includes a second circuit configured to set a gain of the VCO. A frequency tracking network is configured to dynamically adjust one or both of the offset and the gain.

Abstract: System for high-Q integrated RF filters. A filter system is provided that comprises a resonate LC filter and a Q-enhancement circuit coupled to the resonate LC filter, wherein the Q-enhancement circuit operates to improve a quality factor of the filter system.

Abstract: Multi-segment gain control system. Apparatus is provided for a multi-segment gain control. The apparatus includes logic to convert a gain control signal to an exponential signal, and logic to map the exponential signal to multiple control signals that are used to control multiple gain stages to produce linear multi-segment gain control.

Abstract: Direct down-conversion mixer. A direct down-conversion mixer is provided. The mixer comprises an LO switching pair coupled to receive an RF input signal and produce a down converted output signal. The mixer also comprises an integrator coupled to receive the output signal and produce an integrator output signal. The mixer also comprises a control circuit coupled to receive an input voltage and the integrator output signal to produce a control signal that is coupled to the LO switching pair.

Abstract: A divider apparatus for use within a phase-locked loop having an output terminal at which an output frequency is produced. The apparatus includes a prescalar circuit configured to produce a prescaled signal by dividing the output frequency in response to a mode select signal. A first programmable counter is disposed to receive the prescaled signal and to produce the mode select signal. In addition, a second programmable counter is disposed to receive the prescaled signal and to produce a divided signal utilized by the phase-locked loop. The apparatus further includes a control circuit connected to the first programmable counter and to the second programmable counter, the control circuit providing a first resynchronization signal to the first programmable counter and a second resynchronization signal to the second programmable counter.

Abstract: Smart transmitter system that includes apparatus for an automatic gain control circuit. The apparatus includes a circuit translates a transmit power control signal to produce a linear signal, and a first mapping circuit that maps the linear signal to a first control signal that is coupled to a variable gain amplifier (VGA). The apparatus also includes a power amplifier (PA) control circuit that receives the linear signal and a transmit signal to produce a second control signal that is coupled to a power amplifier.

Abstract: Envelope limiting for a polar modulator. A system is provided that intelligently compresses the amplitude modulation in a polar modulator so that it can be implemented with a single-stage variable gain amplifier. Limiting the amplitude modulation range on the low side prevents collapse of the transmit signal's time-varying envelope and eases circuit implementation. Limiting the amplitude modulation range on the high side reduces the peak-to-average ratio of the waveform and thereby improves the efficiency of the radio transmitter.

Abstract: Charge pump circuit. A charge pump circuit is provided for use in a phase-lock loop circuit. The charge pump circuit comprises a charge pump core circuit that outputs a control voltage. The charge pump circuit also comprises a replica circuit that is coupled to the charge pump core circuit, wherein the replica circuit receives the control voltage and produces one or more bias signals that are coupled to the charge pump core circuit to minimize the difference between charge up and charge down currents generated by the charge pump core circuit.

Abstract: Systems for multi-mode phase modulation are disclosed. Systems provide for direct modulation of a multi-mode voltage controlled oscillator (VCO). A fractional-N counter may be used in a phase-locked loop (PLL) to synthesize a radio frequency carrier signal. The multi-mode VCO may be characterized by a first frequency gain during operation in a first mode and by a second frequency gain during operation in a second mode where signals controlling the first and second operating modes are provided by a control circuit. The control circuit may include a switch to provide control signals to the VCO.

Abstract: Envelope limiting for a polar modulator. A system is provided that intelligently compresses the amplitude modulation in a polar modulator so that it can be implemented with a single-stage variable gain amplifier. Limiting the amplitude modulation range on the low side prevents collapse of the transmit signal's time-varying envelope and eases circuit implementation. Limiting the amplitude modulation range on the high side reduces the peak-to-average ratio of the waveform and thereby improves the efficiency of the radio transmitter.

Abstract: Continuous variable-gain low-noise amplifier. The amplifier continuously adjusts its gain between well-defined high and low values by using a cascode current-steering circuit to partition signal current between two different nodes of an output loading network. A shunt feedback network connected from an intermediate node of the loading network to the input provides negative feedback that linearizes the amplifier as its gain is decreased. The circuit degrades the noise figure at lower gains by varying the gain without directly dumping the signal current to the power supply. The circuit produces only small changes in input and output impedances and preserves an improved reverse-isolation cascode characteristic as the gain is controlled.

Abstract: A differential feedback system that minimizes even order distortion of a differential circuit. The feedback system includes a feedback circuit for use with a differential circuit to reduce even-order distortion and dc offset of a difference output signal produced by the differential circuit. The feedback circuit includes an integrator coupled to receive the difference output signal from the differential circuit and produce an integrator output signal. The feedback circuit also includes a control circuit coupled to the integrator to receive the integrator output signal to produce a control signal that is coupled to the differential circuit, wherein the control signal controls the differential circuit to reduce the even-order distortion and the DC offset.

Abstract: A bias voltage circuit with ultra low output impedance. The circuit incorporates feedback to reduce the output impedance at both low and RF frequencies. The bias circuit outputs a bias signal for biasing an amplifier. The bias circuit includes an input stage that receives an input signal and produces the bias signal at an output terminal that is coupled to a gain stage. The bias circuit also includes a load coupled to the input stage at a first terminal, and a feedback circuit coupled between the first terminal and the gain stage.

Abstract: A translinear variable-gain amplifier. The translinear variable gain amplifier receives a differential input voltage and produces a differential output current having a selected gain. The amplifier comprises a buffer amplifier that receives the differential input voltage and produces a differential input current. The amplifier further comprises a translinear gain cell coupled to receive the differential input current and produce the differential output current. The gain cell includes a first adjustable bias source that operates to set a linear input range of the gain cell, and a second adjustable bias source that operates to set a gain value of the gain cell.

Abstract: Voltage-controlled oscillator with apparatus for automatic calibration. The voltage-controlled oscillator includes switches connecting associated coarse-tuning capacitors to an LC resonant tank of the oscillator. The voltage-controlled oscillator also comprises a calibration loop used to appropriately set the switches associated with the coarse tuning capacitors based on a oscillator control signal.

Abstract: System for highly linear phase modulation. Apparatus is provided for linear phase modulation utilizing a phase-locked loop (PLL). The apparatus includes a PLL utilizing fractional N synthesis to realize a non-integer divide value. A two-port voltage-controlled oscillator includes a first port controlled by the phase-locked loop and a second port accessed for direct modulation. A second input to the fractional-N phase-locked loop is provided to remove the modulation introduced at the second port. Lastly, a calibration loop is provided wherein a frequency offset applied at the second port is adjusted until it cancels the effects of a known frequency offset introduced to the fractional-N phase-locked loop.