Abstract: Systems and methods are disclosed for compensating I-Q imbalance in a wireless receiver. The receiver may employ a quadrature downconverter configured to receive an RF signal input and output an in-phase component and a quadrature component at an IF, an IF rotation block configured to downconvert the in-phase and quadrature components to baseband and an I-Q correction block configured to compensate for an I-Q imbalance in the received signal, wherein the I-Q correction block is positioned downstream from the IF rotation block in the signal path. Performing the I-Q correction after conversion to baseband may allow the compensation calculations to operate at a reduced digital rate. Similarly, digitally adjusting the gain of the signal prior to I-Q compensation may reduce the number of bits that are manipulated during the compensation process. These features may represent significant efficiencies as compared to I-Q corrections performed at IF.

Abstract: In a wireless near field communication (NFC) system, a target, such as a smart card, can communicate with an initiator, such as a card reader, by load modulating a radio frequency (RF) signal generated by the initiator. When two or more targets load modulate the RF signal generated, “collisions” can occur with the load modulation. Apparatus and methods detect the presence or absence of collisions in a lower layer or physical layer and report the presence of detected collisions to an upper layer for further handling.

Abstract: Aspects disclosed herein relate to improving acquisition for NFC load modulation. In one example, a communications device is equipped to monitor at least a complex component of load modulation of a carrier signal, detect, using a NFC technology type specific peak detection scheme, a peak associated with at least the complex component, and determine a presence of a packet beginning pattern based on the detected peak. In an aspect, the packet beginning pattern may be associated with a reception of a packet from a target NFC device.

Abstract: A method includes demodulating a load modulated signal at an initiator device based at least partially on a phase adjusted comparison value corresponding to the load modulated signal.

Abstract: Techniques for correcting sampling frequency offset (SFO) and carrier frequency offset (CFO) in a wireless communication system are disclosed. An apparatus for correcting SFO and CFO may include a pilot tone extractor for extracting a plurality of pilot tones from one or more first symbols, a demodulator, an error signal generator, a loop filter, an angle generator, and a device for applying a correction phase to one or more symbols subsequent to the one or more first symbols. The demodulator is configured to demodulate the pilot tones. The error signal generator is configured to generate an error signal by summing and calculating the arctangent of the plurality of demodulated pilot tones. The loop filter is configured to generate an estimated phase rotation due to a residual CFO and the angle generator is configured to generate a correction phase for the plurality of tones.

Abstract: Techniques for correcting sampling frequency offset (SFO) and carrier frequency offset (CFO) in a wireless communication system are disclosed. An apparatus for correcting SFO and CFO may include a pilot tone extractor for extracting a plurality of pilot tones from one or more first symbols, a demodulator, an error signal generator, a loop filter, an angle generator, and a device for applying a correction phase to one or more symbols subsequent to the one or more first symbols. The demodulator is configured to demodulate the pilot tones. The error signal generator is configured to generate an error signal by summing and calculating the arctangent of the plurality of demodulated pilot tones. The loop filter is configured to generate an estimated phase rotation due to a residual CFO and the angle generator is configured to generate a correction phase for the plurality of tones.