Abstract: A phase detection and decision feedback equalization circuit is provided. A first latch and a second latch are coupled to an input of the circuit. A third latch and a fourth latch are respectively coupled in series to outputs of the first latch and second latch. The first and fourth latches are enabled by a clock signal, and the second and third latches are enabled by a complement of the clock signal. A first feedback circuit is configured to provide a signal output from the first latch and a first feedback signal derived from the output of the fourth latch to an input of the third latch. A second feedback circuit is configured to provide a signal output from the second latch and a second feedback signal derived from the output of the third latch to an input of the fourth latch.

Abstract: Exemplary embodiments are directed to data and clock recovery in NFC transceivers. A transceiver may include a phase-locked loop configured to recover a clock from a received input signal in a first mode and enable for oversampling of an output signal in a second, different mode.

Abstract: A serial bit stream having a given bit per second rate is received and distributed to a plurality of phase shifted samplers. A multi-phase sampling trigger is generated at a rate lower than the given bit per second rate, and each of the phase shifted samplers is controlled by one of the phases of the multi-phase sampling trigger. The time spacing between phases of the multi-phase sampling trigger is the inverse of the given bit per second rate.

Abstract: Exemplary embodiments are directed to near field communication A device may include a current digital-to-analog converter (DAC) configured to convey a current to an antenna in a first near-field communication (NFC) mode and enable for load modulation in a second NFC mode.

Abstract: Exemplary embodiments are directed to a transceiver having an adaptive matching circuit. A transceiver may include a matching circuit that is coupled to an antenna and includes an adjustable capacitor. The transceiver may further include an envelope detector coupled to the antenna and a sensor for sensing a voltage at an output of the envelope detector.

Abstract: Exemplary embodiments are directed to a transceiver. A transceiver may include a rectifier coupled to a capacitor. The transceiver may further include a power management module coupled to the capacitor, wherein the capacitor is configured as a power supply capacitor in a first mode and a rectifier capacitor in a second, different mode.

Abstract: Exemplary embodiments are directed to adaptive signal scaling in NFC transceivers. A transceiver may include a programmable load modulation element configured for load modulation in a tag mode. Further, the transceiver may include a sensing element for measuring an amount of power harvested by the transceiver in the tag mode. The transceiver may also include a controller configured for adjusting a depth of load modulation of the programmable load modulation element depending on the amount of power harvested.

Abstract: An LR polyphase filter implemented with inductors and resistors and capable of operating at high frequencies is described. In one design, the LR polyphase filter includes first and second paths, with each path including an inductor coupled to a resistor. The first and second paths receive a first input signal and provide first and second output signals, respectively, which may be in quadrature. For a differential design, the polyphase filter further includes third and fourth paths, which receive a second input signal and provide third and fourth output signals, respectively. The four output signals may be 90° out of phase. The first and second input signals are for a differential input signal. The first and third output signals are for a first differential output signal, and the second and fourth output signals are for a second differential output signal. Each inductor may be implemented with a transmission line.

Abstract: A frequency divider circuit is described. The frequency divider circuit includes a first cross-coupling. The first cross-coupling includes a first cross-coupled transistor with a first gate. The first gate is separately biased. The first cross-coupling also includes a second cross-coupled transistor with a second gate. The second gate is separately biased. The first gate is coupled to the second cross-coupled transistor and the second gate is coupled to the first cross-coupled transistor.

Abstract: A VCO of a PLL outputs a first differential signal of frequency FVCO. A first divide-by-two circuit local to the VCO divides the first differential signal and outputs a first quadrature signal of frequency FVCO/2. Two of the component signals of the first quadrature signal are routed to a second divide-by-two circuit local to a first mixer of a first device. The second divide-by-two circuit outputs a second quadrature signal of frequency FVCO/4 to the first mixer. All four signals of the first quadrature signal of frequency FVCO/2 are routed through phase mismatch correction circuitry to a second mixer of a second device. In one example, FVCO is a tunable frequency of about ten gigahertz, the first device is an IEEE802.11b/g transmitter or receiver that transmits or receives in a first band, and the second device is an IEEE802.11a transmitter or receiver that transmits or receives in a second band.

Abstract: A quadrature output high-frequency RF divide-by-two circuit includes a pair of differential complementary logic latches. The latches are interconnected to form a toggle flip-flop. Each latch includes a tracking cell and a locking cell. In a first embodiment, the locking cell includes two complementary logic inverters and two transmission gates. When the locking cell is locked, the two gates are enabled such that the locked (i.e., latched) signal passes through both transmission gates and both inverters. In one advantageous aspect, the tracking cell only involves two transmission gates. Due to the circuit topology, the first embodiment is operable from a low supply voltage at a high operating frequency while consuming a low amount of supply current. In a second and third embodiment, the tracking cell involves a pair of inverters. The sources of the transistors of the inverters are, however, coupled together thereby resulting in performance advantages over conventional circuits.

Abstract: A differential input envelope detector receives an unamplified Near Field Communication (NFC) input signal from an NFC antenna and downconverts an NFC intelligence signal to baseband. In one example, the NFC input signal includes the NFC intelligence signal modulated onto a carrier. The differential input envelope detector downconverts and outputs the downconverted NFC intelligence signal onto an output node in such a way that the fundamental and odd harmonics of the carrier are canceled on the output node. There is substantially no signal of the frequency of the carrier present on the output node and this facilitates filtering of the downconverted NFC intelligence signal from interference and data recovery. An NFC data recovery circuit receives the downconverted NFC intelligence signal from the envelope detector output node. The NFC data recovery circuit can be a low power digital circuit involving an ultra-low power ADC and subsequent low power digital processing circuitry.

Abstract: In a high-precision signal detection apparatus and method for a high-speed receiver, signal detection occurs asynchronously of the incoming data. A comparison clock is generated by an oscillator whose effective capacitance is varied by a second, lower speed oscillator connected to the capacitance. This prevents the asynchronous sampling that occurs in a zero-crossing position in the incoming data from remaining in that position in subsequent sampling cycles, so that a valid signal is not missed by the detector.

Abstract: A circuit that reduces the effect of noise in a receiver that includes a plurality of filters and a plurality of samplers. The plurality of filters are configured discreetly filter a digital signal to form a plurality of filtered signals. The plurality of samplers are configured to sample the plurality of filtered signals.

Abstract: Methods and apparatus for a gray-coded phase rotating frequency divider. A phase selector is provided that includes two or more selectors, each selector configured to receive multiple clock phases and output a respective clock phase based on one or more selection bits that are part of a selection input, and a gray code generator configured to generate a gray coded output that forms the selection input so that when the gray coded output changes state only selection bits associated with a single selector change. A method includes grouping a plurality of clock phases into two or more groups, for each group, selecting a respective clock phase based on one or more selection bits that are part of a selection input, and generating a gray coded output that forms the selection input so that when the gray coded output changes state only selection bits associated with a single group change.

Abstract: A quadrature output high-frequency RF divide-by-two circuit includes a pair of differential complementary logic latches. The latches are interconnected to form a toggle flip-flop. Each latch includes a tracking cell and a locking cell. In a first embodiment, the locking cell includes two complementary logic inverters and two transmission gates. When the locking cell is locked, the two gates are enabled such that the locked (i.e., latched) signal passes through both transmission gates and both inverters. In one advantageous aspect, the tracking cell only involves two transmission gates. Due to the circuit topology, the first embodiment is operable from a low supply voltage at a high operating frequency while consuming a low amount of supply current. In a second and third embodiment, the tracking cell involves a pair of inverters. The sources of the transistors of the inverters are, however, coupled together thereby resulting in performance advantages over conventional circuits.

Abstract: In a high-precision signal detection apparatus and method for a high-speed receiver, signal detection occurs asynchronously of the incoming data. A comparison clock is generated by an oscillator whose effective capacitance is varied by a second, lower speed oscillator connected to the capacitance. This prevents the asynchronous sampling that occurs in a zero-crossing position in the incoming data from remaining in that position in subsequent sampling cycles, so that a valid signal is not missed by the detector.

Abstract: An LR polyphase filter implemented with inductors and resistors and capable of operating at high frequencies is described. In one design, the LR polyphase filter includes first and second paths, with each path including an inductor coupled to a resistor. The first and second paths receive a first input signal and provide first and second output signals, respectively, which may be in quadrature. For a differential design, the polyphase filter further includes third and fourth paths, which receive a second input signal and provide third and fourth output signals, respectively. The four output signals may be 90° out of phase. The first and second input signals are for a differential input signal. The first and third output signals are for a first differential output signal, and the second and fourth output signals are for a second differential output signal. Each inductor may be implemented with a transmission line.

Abstract: A local oscillator communicates a signal of relatively low frequency across an integrated circuit to the location of a mixer. Near the mixer, a frequency-multiplying SubHarmonically Injection-Locked Oscillator (SHILO) receives the signal and generates therefrom a higher frequency signal. If the SHILO outputs I and Q quadrature signals, then the I and Q signals drive the mixer. If the SHILO does not generate quadrature signals, then a quadrature generating circuit receives the SHILO output signal and generates therefrom I and Q signals that drive the mixer. In one advantageous aspect, the frequency of the signal communicated over distance from the local oscillator to the SHILO is lower than the frequency of the I and Q signals that drive the mixer locally. Reducing the frequency of the signal communicated over distance can reduce power consumption of the LO signal distribution system by more than fifty percent as compared to conventional systems.

Abstract: A method for reducing noise in a frequency synthesizer includes selecting a design variable k, calibrating a feedback time delay (Td), such that Td=kTVCO, where TVCO is the period of the synthesizer output signal. The method further includes estimating an instantaneous quantization error to a number of bits equal to q, defining a reference bias current of Icp/(k2q), where Icp is a charge pump current signal, and applying the estimated instantaneous quantization error to a current array to produce a down modification signal (?I). The current array is biased by the reference bias current. The down modification signal (?I) is summed with the charge pump current signal Icp to modulate a down current portion of the charge pump current signal Icp.