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:
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:
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 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. The second switch and the second inverter form a second sample-and-hold circuit or a second latch that resamples the second single-ended signal.
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:
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:
Selectable sizes for a local oscillator (LO) buffer and mixer are disclosed. In an exemplary embodiment, LO buffer and/or mixer size may be increased when a receiver or transmitter operates in a high gain mode, while LO buffer and/or mixer size may be decreased when the receiver or transmitter operates in a low gain mode. In an exemplary embodiment, LO buffer and mixer sizes are increased and decreased in lock step. Circuit topologies and control schemes for specific exemplary embodiments of LO buffers and mixers having adjustable size are disclosed.
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 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).