Abstract: Techniques are provided for reducing mismatch between the in-phase (I) and quadrature (Q) channels of a communications transmitter or receiver. In an exemplary embodiment, separate voltages are applied to bias the gates or bulks of the transistors in a mixer of the I channel versus a mixer of the Q channel. In another exemplary embodiment, separate voltages are applied to bias the common-mode reference voltage of a transimpedance amplifier associated with each channel. Techniques are further provided for deriving bias voltages to minimize a measured residual sideband in a received or transmitted signal, or to optimize other parameters of the received or transmitted signal. Techniques for generating separate bias voltages using a bidirectional and unidirectional current digital-to-analog converter (DAC) are also disclosed.

Abstract: A wireless communication device configured for receiving a multiple carrier signal is described. The wireless communication device includes a single-chip signal splitting carrier aggregation receiver architecture. The single-chip signal splitting carrier aggregation receiver architecture includes a primary antenna, a secondary antenna and a transceiver chip. The single-chip signal splitting carrier aggregation receiver architecture reuses a simultaneous hybrid dual receiver path.

Abstract: Techniques for using a narrow filter located before a power amplifier to reduce interference in an adjacent frequency band are disclosed. In an exemplary design, an apparatus (e.g., a wireless device) includes the narrow filter and the power amplifier. The narrow filter is for a first frequency band (e.g., Band 40) and has a first bandwidth that is more narrow than the first frequency band. The narrow filter receives and filters an input radio frequency (RF) signal and provides a filtered RF signal. The power amplifier receives and amplifies the filtered RF signal and provides an amplified RF signal. The apparatus may further include a full filter for the first frequency band and located after the power amplifier. The full filter receives and filters the amplified RF signal and provides an output RF signal when it is selected for use.

Abstract: Exemplary embodiments are directed to impedance balancing within a transceiver. A device may include a transformer having a first side coupled to a transmit path and a second side coupled to a receive path. Further, the device may include an antenna tuning network coupled to a first portion of the first side and configured for coupling to an antenna. The device may also include an adjustment unit coupled to a second portion of the first side and configured for being adjusted to enable an impedance at the adjustment unit to be substantially equal to an impedance at the antenna tuning network.

Abstract: A method for dividing the frequency of a signal using a configurable dividing ratio is disclosed. An input signal with a first frequency is received at clocked switches in a frequency divider with a configurable dividing ratio. Non-clocked switches inside the frequency divider are operated to select one of multiple dividing ratios. An output signal is output with a second frequency that is the first frequency divided by the selected dividing ratio.

Abstract: A synchronized frequency divider that can divide a clock signal in frequency and provide differential output signals having good signal characteristics is described. In one exemplary design, the synchronized frequency divider includes a single-ended frequency divider and a synchronization circuit. The single-ended frequency divider divides the clock signal in frequency and provides first and second single-ended signals, which may be complementary signals having timing skew. The synchronization circuit resamples the first and second single-ended signals based on the clock signal and provides differential output signals having reduced timing skew. In one exemplary design, the synchronization circuit includes first and second switches and first and second inverters. The first switch and the first inverter form a first sample-and-hold circuit or a first latch that resamples the first single-ended signal.

Abstract: A time-to-digital converter (TDC) with fine resolution of less than one inverter delay is described. In an exemplary design, the TDC includes first and second delay paths, a delay unit, and a phase computation unit. The first delay path receives a first input signal and a first reference signal and provides a first output. The second delay path receives a second input signal and a second reference signal and provides a second output. The delay unit delays the second input signal relative to the first input signal or delays the second reference signal relative to the first reference signal, e.g., by one half inverter delay. The phase computation unit receives the first and second outputs and provides a phase difference between the input signal and the reference signal. Calibration may be performed to obtain accurate timing for the first and second delay paths.

Abstract: A time-to-digital converter (TDC) with fine resolution of less than one inverter delay is described. In an exemplary design, the TDC includes first and second delay paths, a delay unit, and a phase computation unit. The first delay path receives a first input signal and a first reference signal and provides a first output. The second delay path receives a second input signal and a second reference signal and provides a second output. The delay unit delays the second input signal relative to the first input signal or delays the second reference signal relative to the first reference signal, e.g., by one half inverter delay. The phase computation unit receives the first and second outputs and provides a phase difference between the input signal and the reference signal. Calibration may be performed to obtain accurate timing for the first and second delay paths.

Abstract: Selectable sizes for a local oscillator (LO) buffer and mixer are disclosed. In an embodiment, LO buffer and/or mixer size may be increased when a receiver operates in a high gain mode, while LO buffer and/or mixer size may be decreased when the receiver operates in a low gain mode. In an embodiment, LO buffer and mixer sizes are increased and decreased in lock step. Circuit topologies and control schemes for specific embodiments of LO buffers and mixers having adjustable size are disclosed.

Abstract: A method for reducing average current consumption in a local oscillator (LO) path is disclosed. An LO signal is received at a master frequency divider and a slave frequency divider. Output from the master frequency divider is mixed with an input signal to produce a first mixed output. Output from the slave frequency divider is mixed with the input signal to produce a second mixed output. The second mixed output is forced to be in phase with the first mixed output.

Abstract: A method for dividing the frequency of a signal using a configurable dividing ratio is disclosed. An input signal with a first frequency is received at clocked switches in a frequency divider with a configurable dividing ratio. Non-clocked switches inside the frequency divider are operated to select one of multiple dividing ratios. An output signal is output with a second frequency that is the first frequency divided by the selected dividing ratio.

Abstract: A local oscillator includes a programmable frequency divider coupled to the output of a VCO. The frequency divider can be set to frequency divide by three. Regardless of the divisor, the frequency divider outputs quadrature signals (I, Q) that differ from each other in phase by ninety degrees. To divide by three, the frequency divider includes a divide-by-three frequency divider. The divide-by-three frequency divider includes a divide-by-three circuit, a delay circuit, and a feedback circuit. The divide-by-three circuit frequency divides a signal from the VCO and generates therefrom three signals C, A? and B that differ from each other in phase by one hundred twenty degrees. The delay circuit delays signal A? to generate a delayed version A of the signal A?. The feedback circuit controls the delay circuit such that the delayed version A (I) is ninety degrees out of phase with respect to the signal C (Q).

Abstract: Techniques are disclosed for adjusting and programming the duty cycle of a signal generated by a circuit. In an embodiment, parallel transistors are coupled between a NAND gate and a supply voltage. Selectively enabling the parallel transistors adjusts the switching point of the NAND gate, thereby allowing control of the pulse width of the output signal. In an alternative embodiment, the size of the PMOS versus the NMOS transistors in the NAND gate is selectively varied to achieve the same effect. Further disclosed are applications of the techniques to calibrating the receiver to minimize measured second-order inter-modulation products and/or residual sideband.

Abstract: A time-to-digital converter (TDC) with fine resolution of less than one inverter delay is described. In an exemplary design, the TDC includes first and second delay paths, a delay unit, and a phase computation unit. The first delay path receives a first input signal and a first reference signal and provides a first output. The second delay path receives a second input signal and a second reference signal and provides a second output. The delay unit delays the second input signal relative to the first input signal or delays the second reference signal relative to the first reference signal, e.g., by one half inverter delay. The phase computation unit receives the first and second outputs and provides a phase difference between the input signal and the reference signal. Calibration may be performed to obtain accurate timing for the first and second delay paths.

Abstract: A synchronized frequency divider that can divide a clock signal in frequency and provide differential output signals having good signal characteristics is described. In one exemplary design, the synchronized frequency divider includes a single-ended frequency divider and a synchronization circuit. The single-ended frequency divider divides the clock signal in frequency and provides first and second single-ended signals, which may be complementary signals having timing skew. The synchronization circuit resamples the first and second single-ended signals based on the clock signal and provides differential output signals having reduced timing skew. In one exemplary design, the synchronization circuit includes first and second switches and first and second inverters. The first switch and the first inverter form a first sample-and-hold circuit or a first latch that resamples the first single-ended signal.

Abstract: A local oscillator includes a programmable frequency divider coupled to the output of a VCO. The frequency divider can be set to frequency divide by three. Regardless of the divisor, the frequency divider outputs quadrature signals (I, Q) that differ from each other in phase by ninety degrees. To divide by three, the frequency divider includes a divide-by-three frequency divider. The divide-by-three frequency divider includes a divide-by-three circuit, a delay circuit, and a feedback circuit. The divide-by-three circuit frequency divides a signal from the VCO and generates therefrom three signals C, A? and B that differ from each other in phase by one hundred twenty degrees. The delay circuit delays signal A? to generate a delayed version A of the signal A?. The feedback circuit controls the delay circuit such that the delayed version A (I) is ninety degrees out of phase with respect to the signal C (Q).

Abstract: An exemplary embodiment disclosed comprises a mixer having a plurality of input leads; a first degenerative impedance element coupled to a first input lead of the mixer; a second degenerative impedance element coupled to a second input lead of the mixer; and a local oscillator (LO) system comprising a plurality of duty cycle modes to generate a LO signal for the mixer, the local oscillator system operates in a first duty cycle based on a first gain state of the mixer, and in a second duty cycle based on a second gain state of the mixer.

Abstract: Within a receiver, the frequency of a comparison reference clock signal supplied to a fractional-N Phase-Locked Loop (PLL) is dynamically changed such that undesirable reciprocal mixing of reference spurs with known jammers (for example, transmit leakage) is minimized. As the transmit channel changes within a band, and as the transmit leakage frequency changes, a circuit changes the frequency of the comparison reference clock signal such that reference spurs generated by the PLL are moved in frequency so that they do not reciprocally mix with transmitter leakage in undesirable ways. In a second aspect, the PLL is operable either as an integer-N PLL or a fractional-N PLL. In low total receive power situations, the PLL operates as an integer-N PLL to reduce receiver susceptibility to fractional-N spurs. In a third aspect, jammer detect information is used to determine the comparison reference clock signal frequency.

Abstract: Techniques are provided for reducing mismatch between the in-phase (I) and quadrature (Q) channels of a communications transmitter or receiver. In an exemplary embodiment, separate voltages are applied to bias the gates or bulks of the transistors in a mixer of the I channel versus a mixer of the Q channel. In another exemplary embodiment, separate voltages are applied to bias the common-mode reference voltage of a transimpedance amplifier associated with each channel. Techniques are further provided for deriving bias voltages to minimize a measured residual sideband in a received or transmitted signal, or to optimize other parameters of the received or transmitted signal. Techniques for generating separate bias voltages using a bidirectional and unidirectional current digital-to-analog converter (DAC) are also disclosed.

Abstract: Techniques are disclosed for adjusting and programming the duty cycle of a signal generated by a circuit. In an embodiment, parallel transistors are coupled between a NAND gate and a supply voltage. Selectively enabling the parallel transistors adjusts the switching point of the NAND gate, thereby allowing control of the pulse width of the output signal. In an alternative embodiment, the size of the PMOS versus the NMOS transitors in the NAND gate is selectively varied to achieve the same effect. Further disclosed are applications of the techniques to calibrating the receiver to minimize measured second-order inter-modulation products and/or residual sideband.