A modulated RF carrier produced at the output of the polar transmitter's switch-mode power amplifier (SMPA) is conveyed to an output filter network comprising a harmonic low-pass filter (LPF) connected in parallel with an absorptive high-pass filter (HPF). Together the harmonic LPF and absorptive HPF pass the fundamental component of the modulated RF carrier to the polar transmitter's load while also absorbing higher harmonic components that would otherwise be undesirably reflected back toward the output of the SMPA.

When the ultra-low power mm-scale sensor node does not have a crystal oscillator and phase-lock loop, it inevitably exhibits significant carrier frequency offset (CFO) and sampling frequency offset (SFO) with respect to the reference frequencies in the gateway. This disclosure enables efficient real-time calculation of accurate SFO and CFO at the gateway, thus the ultra-low power mm-scale sensor node can be realized without a costly and bulky clock reference crystal and also power-hungry phase lock loop. In the proposed system, the crystal-less sensor starts transmission with repetitive RF pulses with a constant interval, followed by the data payload using pulse-position modulation (PPM). A proposed algorithm uses a two-dimensional (2D) fast Fourier transform (FFT) based process that identifies the SFO and CFO at the same time to establish successful wireless communication between the gateway and crystal-less sensor nodes.

When the ultra-low power mm-scale sensor node does not have a crystal oscillator and phase-lock loop, it inevitably exhibits significant carrier frequency offset (CFO) and sampling frequency offset (SFO) with respect to the reference frequencies in the gateway. This disclosure enables efficient real-time calculation of accurate SFO and CFO at the gateway, thus the ultra-low power mm-scale sensor node can be realized without a costly and bulky clock reference crystal and also power-hungry phase lock loop. In the proposed system, the crystal-less sensor starts transmission with repetitive RF pulses with a constant interval, followed by the data payload using pulse-position modulation (PPM). A proposed algorithm uses a two-dimensional (2D) fast Fourier transform (FFT) based process that identifies the SFO and CFO at the same time to establish successful wireless communication between the gateway and crystal-less sensor nodes.

Provided herein are apparatus and methods for wideband receivers. In certain configurations, a radio frequency (RF) communication system includes two or more receiver slices that operate in parallel with one another to process an RF input signal. The receiver slices generate digital signals by processing different sub-bands of the RF input signal. For example, the RF communication system can include a first receiver slice that processes a first sub-band of the RF input signal and that generates a first digital signal representing the first sub-band, and a second receiver slice that processes a second sub-band of the RF input signal and generates a second digital signal representing the second sub-band. The RF communication system further includes a clock generation circuit that generates one or more clock signals to control timing of the receiver slices, and a sub-band processing circuit that processes the digital signals from the receiver slices.

Systems and methods for transpositional modulation and demodulation are provided. One such method for generating a signal includes the steps of providing a look-up table having a plurality of quarter-cycle waveforms, each of said quarter-cycle waveforms associated with a respective input level; receiving an input signal; and outputting quarter-cycle waveforms associated with levels of the received input signal. Systems for transpositional modulation are also provided. One such system for generating a signal includes a look-up table having a plurality of quarter-cycle waveforms. Each of the quarter-cycle waveforms are associated with a respective input level, and the look-up table is configured to receive an input signal, and output quarter-cycle waveforms associated with levels of the received input signal.

In one aspect, a method for estimating residual carrier frequency offset (CFO) in a phase-modulated wireless signal having pseudo noise (PN) spreading is provided. The method includes receiving, at a digital transceiver, a plurality of PN spread blocks of in-phase and quadrature (I/Q) samples of the phase-modulated wireless signal and performing sample-level de-rotation, symbol-level de-spreading, and sign alignment. The method also includes estimating a phase difference and determining an estimated residual CFO based on the phase difference.

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for modulating and demodulating transpositional modulated (TM) signals. One aspect features a method of modulating a carrier signal that include the actions of generating a TM signal by generating a sinusoidal signal, and modulating the sinusoidal signal based on a data signal to provide the TM signal. Inserting the TM signal into a carrier signal to provide a TM modulated carrier signal. Modulating the TM modulated carrier signal with a non-TM signal to provide a combined signal. Transmitting the combined signal.

Device, system and method of securely transmitting information from a mobile device or application or a user device to a mobile phone or other acoustic aware devices using audio frequency encoded data and security token transmission.

A method for transmitting information includes: determining a target frequency range involved in an in-device interference in user equipment when the in-device interference is likely to occur, the target frequency range including a target downlink frequency range and at least one target uplink frequency range; adjusting a transmission resource configuration within the target frequency range; and transmitting information over a transmission resource after adjustment of the transmission resource configuration within the target frequency range, to avoid occurrence of the in-device interference.

Provided herein are apparatus and methods for wideband receivers. In certain configurations, a radio frequency (RF) communication system includes two or more receiver slices that operate in parallel with one another to process an RF input signal. The receiver slices generate digital signals by processing different sub-bands of the RF input signal. For example, the RF communication system can include a first receiver slice that processes a first sub-band of the RF input signal and that generates a first digital signal representing the first sub-band, and a second receiver slice that processes a second sub-band of the RF input signal and generates a second digital signal representing the second sub-band. The RF communication system further includes a clock generation circuit that generates one or more clock signals to control timing of the receiver slices, and a sub-band processing circuit that processes the digital signals from the receiver slices.