Abstract: An Interleaved Radio Frequency Digital-to-Analog Converter (RF DAC) suitable for use in cellular base stations and optimized to give both a wide RF tuning range and a wide RF bandwidth is disclosed. The RF DAC uses two levels of interleaving, the first providing a direct conversion path from Base Band (BB) to RF, and the second providing a variable interleaving factor through the use of summation to optimize the output bandwidth as a function of the RF center frequency. Digital Interpolation, including an arbitrary sample rate conversion filter, allows the RF DAC to operate from a wide range of possible BB sample rates and the DAC sample rate is a fixed ratio of the RF center frequency. As a result, the spurious outputs from the RF DAC are in known locations that are relatively easy to filter out, minimizing the frequency planning tasks required for a complete RF system design.

Abstract: Systems and methods are provided in which a voltage-controlled oscillator for a radio transmitter includes a LC tank circuit, and a muting circuit. The LC tank circuit includes an inductive element and a capacitive element; wherein the inductive element of the LC tank circuit includes the antenna of the transmitter. The muting circuit can include a variable resistor connected in parallel with the LC tank circuit.

Abstract: Systems and methods are provided in which a voltage-controlled oscillator for a radio transmitter includes a LC tank circuit, and a muting circuit. The LC tank circuit includes an inductive element and a capacitive element; wherein the inductive element of the LC tank circuit includes the antenna of the transmitter. The muting circuit can include a variable resistor connected in parallel with the LC tank circuit.

Abstract: An Interleaved Radio Frequency Digital-to-Analog Converter (RF DAC) suitable for use in cellular base stations and optimized to give both a wide RF tuning range and a wide RF bandwidth is disclosed. The RF DAC uses two levels of interleaving, the first providing a direct conversion path from Base Band (BB) to RF, and the second providing a variable interleaving factor through the use of summation to optimize the output bandwidth as a function of the RF center frequency. Digital Interpolation, including an arbitrary sample rate conversion filter, allows the RF DAC to operate from a wide range of possible BB sample rates and the DAC sample rate is a fixed ratio of the RF center frequency. As a result, the spurious outputs from the RF DAC are in known locations that are relatively easy to filter out, minimizing the frequency planning tasks required for a complete RF system design.

Abstract: Systems and methods are provided in which an offset phase-locked loop (PLL) system can be configured as part of a radio frequency transmitter. The PLL can include a phase detection circuit including a first input configured to receive an information signal and a second input configured to receive a feedback signal; a charge pump including an input coupled to the phase detection circuit and an output; a filter including an input coupled to the output of the charge pump; a voltage-controlled oscillator coupled to the charge pump and including an LC tank circuit comprising an inductive element and a capacitive element, wherein the inductive element of the LC tank circuit comprises the antenna; and a feedback path.

Abstract: An Interleaved Radio Frequency Digital-to-Analog Converter (RF DAC) suitable for use in cellular base stations and optimized to give both a wide RF tuning range and a wide RF bandwidth is disclosed. The RF DAC uses two levels of interleaving, the first providing a direct conversion path from Base Band (BB) to RF, and the second providing a variable interleaving factor through the use of summation to optimize the output bandwidth as a function of the RF center frequency. Digital Interpolation, including an arbitrary sample rate conversion filter, allows the RF DAC to operate from a wide range of possible BB sample rates and the DAC sample rate is a fixed ratio of the RF center frequency. As a result, the spurious outputs from the RF DAC are in known locations that are relatively easy to filter out, minimizing the frequency planning tasks required for a complete RF system design.

Abstract: An Interleaved Radio Frequency Digital-to-Analog Converter (RF DAC) suitable for use in cellular base stations and optimized to give both a wide RF tuning range and a wide RF bandwidth is disclosed. The RF DAC uses two levels of interleaving, the first providing a direct conversion path from Base Band (BB) to RF, and the second providing a variable interleaving factor through the use of summation to optimize the output bandwidth as a function of the RF center frequency. Digital Interpolation, including an arbitrary sample rate conversion filter, allows the RF DAC to operate from a wide range of possible BB sample rates and the DAC sample rate is a fixed ratio of the RF center frequency. As a result, the spurious outputs from the RF DAC are in known locations that are relatively easy to filter out, minimizing the frequency planning tasks required for a complete RF system design.

Abstract: An Interleaved Radio Frequency Digital-to-Analog Converter (RF DAC) suitable for use in cellular base stations and optimized to give both a wide RF tuning range and a wide RF bandwidth is disclosed. The RF DAC uses two levels of interleaving, the first providing a direct conversion path from Base Band (BB) to RF, and the second providing a variable interleaving factor through the use of summation to optimize the output bandwidth as a function of the RF center frequency. Digital Interpolation, including an arbitrary sample rate conversion filter, allows the RF DAC to operate from a wide range of possible BB sample rates and the DAC sample rate is a fixed ratio of the RF center frequency. As a result, the spurious outputs from the RF DAC are in known locations that are relatively easy to filter out, minimizing the frequency planning tasks required for a complete RF system design.

Abstract: Apparatus and methods for removing dc offsets in feedback loops such as may be used in communication circuits are disclosed. A comparator may be used to sample the output of the feedback loop, with the comparator output applied to a DSP module. The DSP module is configured to determine a dc offset in the output signal and generate an offset correction signal, which may then be applied to the input of the feedback loop to adjust the de offset.

Abstract: Apparatus and methods for providing transmit signals in polar transmitters are described. A modulation signal may be provided from a VCO to low noise and low power signal paths and selectively combined based on a desired output power level. CMOS and CML divider circuits may be used to implement the low noise and low power signal paths respectively, and logic may be provided to select desired signals from the low noise and low power signal stages based on the desired output power level.

Abstract: Apparatus and methods for improving the spectral performance of a polar modulator are described. A composite FM signal component of a composite polar transmit signal may be processed by monitoring the FM signal to detect a transient burst component, and, responsive to detection of a transient burst, generating a spectrally friendly replacement signal component that may be combined with the FM signal to improve spectral performance of the composite signal. In addition, an associated AM component of the composite transmit signal may be filtered to further improve spectral performance.

Abstract: Apparatus and methods for adjustment of spectral signal characteristics in polar modulators are described. A composite signal detection circuit is configured to detect when a signal trajectory of a composite signal provided to the polar modulator passes near the origin of a complex plane associated with the composite signal, and then adjusts the composite signal to pass through the origin. A spectral adjustment circuit is described to adjust AM and FM or PM components of the composite signal to reduce the deviation of an FM component of the composite signal.

Abstract: Apparatus and methods for enhancement of performance in polar modulators are described. In one implementation, an FM signal component is divided into a coarse FM signal and a residue FM signal to be applied to a VCO for generation of a modulation signal. The coarse FM signal may be proportional to a threshold value when the FM signal exceeds the threshold, while the residue FM signal may be proportional to the difference between the FM signal and coarse FM signal.

Abstract: An alternate clock apparatus and method configured to reduce noise in selected frequency bands in an electronic device such as a communication device is described. In one embodiment the alternate clock includes a ring oscillator to generate multiple time shifted signals which may then be combined to generate clock signals at alternate frequencies to a primary reference. A resynchronization circuit may be coupled to the ring oscillator to periodically resynchronize the ring oscillator to a reference signal to reduce alternate clock jitter.

Abstract: Apparatus and methods for providing integrated RF notch filter subsystems having enhanced Q values are described. An integrated notch filter includes an LC filter element and a Q-enhancement circuit coupled to the LC filter element, with the Q-enhancement circuit configured to offset resistive losses in the LC filter element to adjust the Q value of the filter system. A transceiver having multiple LNAs for various bands may be provided to a single notch filter system including a Q-enhancement 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: A system and method for providing, among other things, wideband phase modulation is described. Several embodiments include a scaling network for scaling an input modulation signal in accordance with a scaling parameter and thereby generating a scaled modulation signal that is applied to a voltage-controlled oscillator of a phase-locked loop. A sensing network may also be included for detecting changes in one or more parameters characterizing the voltage-controlled oscillator. A calibration adjustment network may additionally be included for adjusting the scaling parameter in accordance with the changes in the one or more parameters.

Abstract: An alignment apparatus for use with a polar transmitter system is disclosed herein. The alignment apparatus includes a signal alignment module configured to apply an amplitude modulation control signal and a frequency modulation control signal to the polar transmitter in accordance with a defined timing relationship. A time alignment network, operatively coupled between an output of the polar transmitter system and the signal alignment module, sets the defined timing relationship.

Abstract: Variable gain commutating amplifier apparatus and methods for use in a polar modulator are described. The apparatus may include two or more commutating amplifier stages configured to be switched to an output load based on a desired amplitude and/or transmit power level. The amplifier stages may include cross-coupled differential pairs to cancel RF carrier feedthrough. An additional R-2R ladder circuit may be provided to further extend the dynamic range by reducing the output power at the lowest output stages.

Abstract: Apparatus and methods for improving the performance of a modulator, typically in an I/Q modulation system, are described. Input I and Q current modulation signals may be processed to generate a sign signal and a magnitude signal, with the magnitude signal selectively applied to the inputs of a mixer based on the sign signal so as to generate respective I and Q modulation signal components. These may then be combined to generate a composite modulation signal.