Abstract: Exemplary embodiments are related to interfacing a digital module and a radio-frequency (RF) module of a wireless communication device. A device may include a digital module configured to output at least one constant-envelope phase modulated signal. The device may further include an RF module configured to receive the at least one constant-envelope phase modulated signal and generate one or more digital bits in response to receipt of the at least one constant-envelope phase modulated signal.

Abstract: A front end parallel resonant switch is disclosed. In an exemplary embodiment, an apparatus includes an inductor and a capacitor configured to couple a first RF transmission to an antenna, and at least one switch configured to connect the inductor to the capacitor to form a matching network when transmitting the first RF transmission from the antenna, and to connect the inductor to capacitor to form a parallel resonant circuit when transmitting a second RF transmission from the antenna.

Abstract: The present systems and methods may shape signals to meet emission mask requirements, current consumption requirements, and overshoot/undershoot requirements relating to the interaction that, for example, occurs when a near field communications (NFC) target comes within range of an NFC initiator, and the initiator generates and transmits an NFC waveform. In some implementations, a pair of bit patterns are defined whose differential output from an amplifier is a shaped pulse width modulated waveform. Varying individual bits of the bit patterns can vary the shaped pulse waveform with predictability. The pulse width modulated waveform may be filtered using a matching network that reduces higher order harmonics, thereby reducing out-of-band emissions.

Abstract: A method for communication between near field communication (NFC) devices includes generating a transmission signal, an in-phase local oscillator signal, and a quadrature local oscillator signal from edges of an input clock signal. The method further includes mixing a load modulated signal with the in-phase local oscillator signal to generate an in-phase baseband signal. The method further includes mixing the load modulated signal with the quadrature local oscillator signal to generate a quadrature baseband signal. The method further includes adjusting a phase delay of at least one of the in-phase local oscillator signal or the quadrature local oscillator signal in response to a first signal strength of the in-phase baseband signal and a second signal strength of the quadrature baseband signal.

Abstract: An NFC initiator device requests a passive communication mode by modulating a request onto a first carrier signal. In response thereto, the target device transmits a second carrier signal while still receiving the first carrier signal from the initiator device. The target device may modulate data onto the second carrier signal to convey information to the initiator device. The initiator device may detect changes in the load provided by the target device to interpret the data conveyed by the target device.

Abstract: Hardware interrupt functionality associated with a disable pin may be used to place a near-field communication (NFC) device into various operational modes. For example, various intermediate voltage windows may be defined within an I/O voltage domain and a resistive divider running off an I/O rail may generate multiple reference voltages within the I/O voltage domain. In one embodiment, different comparators may compare voltage on the disable pin to the reference voltages generated with the resistive divider to determine whether the voltage on the disable pin falls within one of the intermediate voltage windows. As such, if a particular comparator determines that the voltage on the disable pin falls within one of the intermediate voltage windows, a control signal may be generated to transition the NFC device into a corresponding operational mode.

Abstract: Techniques for providing a transceiver with a sliding intermediate frequency (IF). In an aspect, a PLL generates a single local oscillator (LO) signal used for both up-conversion by a transmit (TX) signal path and down-conversion by a receive (RX) signal path, wherein the LO frequency is chosen as the TX carrier frequency. As the TX and RX carrier frequencies may generally differ by a variable amount, the RX signal path utilizing the (TX) LO frequency for down-conversion may be characterized as having a “sliding” IF. To accommodate the sliding IF receiver architecture, specific processing functions such as charge sampling, discrete-time analog band-pass filtering, and sub-sampling analog-to-digital conversion (ADC) are described.

Abstract: Techniques for improving performance of a transformer shared amongst a plurality of operating modes. In an aspect, first and second primary windings of a transformer are coupled to an AC ground voltage. Primary windings are mutually coupled to a secondary winding of the transformer. To render the second primary winding inactive, e.g., when operating in a first mode, a switch coupling the second primary winding to the common reference voltage is opened. Similarly, when it is desired to render the first primary winding inactive, e.g., when operating in a second mode, a switch coupling the first primary winding to the common reference voltage is opened. In this manner, the inactive primary winding advantageously does not load the secondary winding. Further aspects provide for, e.g., extending the techniques to more than two modes, and alternative techniques to mutually couple the signal from the primary to the secondary winding.

Abstract: A near-field communications (NFC) device includes an NFC antenna, a matching network coupled to the NFC antenna, and a transmitter coupled to the matching network. The transmitter applies a signal to the matching network and varies a frequency of the signal. A parameter is measured while varying the frequency of the signal. A peak value of the parameter is identified and compared to a threshold. A communication protocol is initiated in response to a determination that the peak value satisfies the threshold.

Abstract: A near-field communications (NFC) device includes an NFC antenna, a matching network coupled to the NFC antenna, and a transmitter coupled to the matching network. The transmitter applies a signal to the matching network and a capacitance of the matching network is varied. A parameter is measured while varying the capacitance of the matching network and while applying the signal. A peak value of the parameter is identified and compared to a threshold. A communication protocol is initiated in response to a determination that the peak value satisfies the threshold.

Abstract: Techniques for calculating a real power delivered to a transmit load of a transceiver. In an aspect, two distinct voltages are sampled from a matching network coupling the transmit load to an amplifier output. The voltages are coupled by configurable coupling elements to the down-conversion mixers of the transceiver, and are subsequently converted to digital form for processing by a baseband processor. The baseband processor may calculate a coefficient relating the calculated real power to an actual power delivered to the load. The coefficient may be stored and subsequently applied to a transmit element during normal signal transmission by the transceiver. Note the coupling elements may be configured to decouple the sampled voltages from the down-conversion mixers during normal signal reception by the transceiver, thus avoiding unnecessary loading on the receive signal path.

Abstract: Systems and methods are disclosed that can shape signals to meet emission mask requirements, current consumption requirements, and overshoot/undershoot requirements relating to the interaction that, for example, occurs when a near field communications (NFC) target comes within range of an NFC initiator, and the initiator generates and transmits an NFC waveform. In some implementations, a pair of bit patterns are defined whose differential output from an amplifier is a shaped pulse width modulated waveform. Varying individual bits of the bit patterns can vary the shaped pulse waveform with predictability. The pulse width modulated waveform may be filtered using a matching network that reduces higher order harmonics, thereby reducing out-of-band emissions.

Abstract: Systems, methods, and devices for wireless communication are included herein. An aspect of the subject matter described in the disclosure provides a device configured to detect a transmission. The device includes a receiver configured to receive an inductive communication signal having a center frequency. The device further includes an analog-to-digital converter configured to sample the signal at a rate higher than twice the center frequency. The device further includes one or more processors configured to digitally downconvert the signal. The processors are further configured to compare an energy of the downconverted signal to a detection threshold. The device further includes a transmitter configured to selectively transmit a communication based on the comparison.

Abstract: A front end parallel resonant switch is disclosed. In an exemplary embodiment, an apparatus includes an inductor and a capacitor configured to couple a first RF transmission to an antenna, and at least one switch configured to connect the inductor to the capacitor to form a matching network when transmitting the first RF transmission from the antenna, and to connect the inductor to capacitor to form a parallel resonant circuit when transmitting a second RF transmission from the antenna.

Abstract: An electronic device for communication comprises a processor. The processor comprises a power scan module configured to receive an energy detection signal identifying detection of energy of a page signal or an inquiry signal. The power scan module is further configured to provide, upon receiving the energy detection signal, an instruction to perform a page scan or an inquiry scan.

Abstract: A transceiver system is disclosed for use in a telecommunication system. The transceiver system includes a transmission circuit with a differential transmitter input coupled via a transmitter input stage to a differential input of a transmission amplifier in an embodiment. The transmitter input stage includes a trimmable resistor, one end of which is coupled to a positive transmit input signal, and the other end of which is coupled to a negative transmit input signal. The transceiver system also includes a receiver circuit with a differential receiver output coupled to a differential input of a receiver amplifier, and further includes a transmission line interface circuit coupled to a differential output of said transmission amplifier and to a differential input of said receiver amplifier. In accordance with other embodiments, the receiver amplifier includes an input stage that includes a first plurality of capacitors and a feedback circuit that includes a second plurality of capacitors.

Abstract: A system and method for suppressing RFI receives a differential input signal Vd, and a signal Vcm which varies with the common mode component of Vd. Vcm is phase-shifted and then amplified with a programmable gain G1 to produce an output VA1. A subtractor produces an output Vsub which varies with Vd?VA1. Vsub is amplified with a programmable gain G2 to produce an output VA2. An analog input signal processing circuit receives VA2 at an input which has an associated maximum dynamic range. A processor adjusts G2 such that VA2 covers the maximum dynamic range, adjusts the phase shift and G1 to minimize VA2, and adjusts G2 to increase VA2 such that it again covers the maximum dynamic range. The RFI in Vd is substantially subtracted out, thereby enabling the full dynamic range of the analog input signal processing circuit to be employed in receiving Vd.

Abstract: A JFET switch select circuit including a first current mirror system including a first high current mirror circuit referenced to high rail voltage and a first low current mirror circuit referenced to a low rail voltage, a second current mirror system including a second high current mirror circuit referenced to the high rail voltage and a second low current mirror circuit referenced to the low rail voltage, and a comparator circuit responsive to an input voltage and a reference voltage for directing current from a current supply circuit to one of the first and second high current mirror circuits and one of the first and second low current mirror circuits for saturating a switching device of one of the first and second high current mirror circuits to set a first output voltage proximate to a high rail voltage and for saturating a switching device of one of the first and second low current mirror circuits to set a second output voltage proximate a low rail voltage.

Abstract: A transceiver system is disclosed for use in a telecommunication system. The transceiver system includes a transmission circuit including a differential transmitter input coupled to a differential input of a transmission amplifier, a receiver circuit including a differential receiver output coupled to a differential output of a receiver amplifier, and a transmission line interface circuit that is coupled to a differential output of the transmission amplifier and to a differential input of the receiver amplifier. The transmission line interface circuit providing a second order high pass transfer function.

Abstract: A hybrid matching system is disclosed for use with a transmitter and receiver. The hybrid matching system includes a pair of transmitter output nodes, a pair of receiver input nodes, and a pair of terminals for interfacing to a transmission line. The system further includes a first impedance bridge portion including at least one inductor for coupling to the transmission line terminals via at least one transformer winding, and a second impedance bridge portion interposed between the pair of transmitter output nodes and the first impedance bridge portion, and interposed between the pair of receiver input nodes and the first impedance bridge portion.