Embodiments of this application disclose a signal processing method and a communication apparatus, to obtain an estimated value of a receive end-direct current (Rx DC) component based on a sampling point of a signal. In this application, for a specified data frame including one or more direct current (DC) subcarriers or a field in the data frame, the signal is sampled in a first time period to obtain at least one first sampling point, the signal is sampled in a second time period after the first time period to obtain at least one second sampling point corresponding to the at least one first sampling point, and then the estimated value of the Rx DC component is obtained based on the at least one first sampling point, the at least one second sampling point, and a normalized frequency offset.

An apparatus and a method for synchronizing a Digital Frequency Shift (DFS) for a signal to be transmitted over a wireless channel are disclosed. For example, the method, by a synchronizer, transmits a DFS trigger to a Digital Front End (DFE) processor and a Local Oscillator (LO) trigger to an LO in a synchronous manner, the method, by the DFE processor, applies a DFS on received data in response to receiving the DFS trigger, the method, by the LO, applies a complementary shift on a carrier signal in response to receiving the LO trigger, the method, by the upconverter, digital-to-analog converts and radio frequency modulates the digital frequency-shifted received data and the complementary-shifted carrier signal. In another example, the method, by the synchronizer, transmits a phase error to a phase error corrector that performs a phase error correction.

Embodiments of a station (STA) and method for communication in accordance with phase noise compensation are generally described herein. The STA may determine, based at least partly on one or more operational parameters, whether to perform phase noise compensation of data symbols of a received protocol data unit (PDU). For instance, the STA may compare the operational parameters with one or more thresholds. The STA may further determine a method of phase noise compensation based at least partly on one or more operational parameters. As an example, the STA may determine a type of interpolation to be used for an interpolation of phase noise estimates of pilot symbols to determine phase noise estimates of data symbols. Example operational parameters may include a signal quality metric, a carrier frequency offset (CFO) measurement and/or modulation and coding scheme (MCS).

System for adjusting a reference constellation for demodulating an optical signal include a coherent electro-optical receiver configured to convert a received optical signal to a plurality of electrical signals, an array of analog-to-digital convertors configured to digitize the plurality of electrical signals, and processor logic. The processor logic is configured to process the digitized plurality of electrical signals using a reference constellation to yield a plurality of decoded signals and a signal quality measurement. The reference constellation includes an inphase component equal to an ideal inphase component plus an inphase offset and a quadrature component equal to an ideal quadrature component plus a quadrature offset. The processor logic is configured to determine an optimal inphase offset and optimal quadrature offset. The processor logic is configured to update the reference constellation using the optimal inphase offset and the optimal quadrature offset.

In a communication receiver circuit, an amplifier circuit can include an adjustable gain. A signal corresponding to a portion of a transmitted frame can be received, and a gain of the receiver circuit can be adjusted such as automatically, and such adjustment can be referred to as automatic gain control (AGC). An offset correction can be performed to adjust for an error in a received representation of a transmitted carrier, and such offset correction can be referred to as carrier frequency offset (CFO) correction. A portion of the received signal can be dynamically allocated between AGC and CFO correction, such as allocating a longer duration to CFO correction when AGC results in a relatively higher receiver gain, and allocating a shorter duration to CFO correction when AGC results in a relatively lower receiver gain.

Techniques and systems for extending the capture range of frequency offset error detection are described. For instance, the present disclose describes efficient frequency estimation structures (e.g., zero crossing minimum/maximum (min/max) structures) that may extend carrier frequency offset error capture range by running a bank (e.g., a set) of parallel capture range structures trialing different frequency errors. In some aspects, a set of frequency offset estimation circuits and a set of correlation circuits (e.g., 1-bit correlators) may be used on parallel streams to perform correlation operations on each branch of a received bit stream to determine correlations with known preamble patterns (e.g., to accurately estimate large frequency offset errors).

A system and method for an NFC card for use in asynchronous NFC card emulation mode transmission. The method comprises estimating carrier frequency offset between a carrier frequency of a NFC reader and a carrier frequency of the NFC card, adjusting digital baseband sampling of the baseband sample output at the NFC card emulation mode transmitter based on the estimated carrier frequency offset to obtain an adjusted baseband sample output and modulating a RF transmitter in the NFC card emulation mode transmitter based on the adjusted baseband sample output.

System for adjusting a reference constellation for demodulating an optical signal include a coherent electro-optical receiver configured to convert a received optical signal to a plurality of electrical signals, an array of analog-to-digital convertors configured to digitize the plurality of electrical signals, and processor logic. The processor logic is configured to process the digitized plurality of electrical signals using a reference constellation to yield a plurality of decoded signals and a signal quality measurement. The reference constellation includes an inphase component equal to an ideal inphase component plus an inphase offset and a quadrature component equal to an ideal quadrature component plus a quadrature offset. The processor logic is configured to determine an optimal inphase offset and optimal quadrature offset. The processor logic is configured to update the reference constellation using the optimal inphase offset and the optimal quadrature offset.

Embodiments of the present disclosure describe mechanisms for radio frequency (RF) ranging between pairs of radio units based on radio signals exchanged between units. An exemplary radio system may include a first radio unit, configured to transmit a first radio signal, and a second radio unit configured to receive the first radio signal, adjust a reference clock signal of the second radio unit based on the first radio signal, and transmit a second radio signal generated based on the adjusted reference clock signal. Such a radio system may further include a processing unit for determining a distance between the first and second radio units based on a phase difference between the first radio signal as transmitted by the first radio unit and the second radio signal as received at the first radio unit. Disclosed mechanisms may enable accurate RF ranging using low-cost, low-power radio units.

A method is disclosed for synchronization, comprising obtaining baseband signal samples of a baseband information signal having an in-phase signal sample and a quadrature signal sample, the baseband information signal having been generated by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency, the modulated carrier signal being an in-phase signal and quadrature signal having a substantially uncorrelated nature and derived from different input data sets; determining an offset frequency rotation based on an estimated residual correlation between the in-phase signal samples and the quadrature signal samples; and, deriving synchronization information from the offset frequency rotation, wherein the received modulated carrier signal is a quadrature-modulated signal with arbitrary orthogonal in-phase and quadrature signal components.