Ultra-short pulse detection. At least some example embodiments are methods including: receiving by an antenna a series of ultra-short pulses of electromagnetic energy at a repetition frequency, the receiving creates a pulse signal; self-mixing or intermodulating the pulse signal by applying the pulse signal to a non-linear electrical device, thereby creating a modulated signal; and filtering the modulated signal to recover a filtered signal having an intermodulated frequency being the repetition frequency.

A carrier recovery system for a receiver of a phase-modulated signal N-PSK, the system including a first pre-conditioning circuit of the signal received (S(t)), with the pre-conditioned signal (SP(t)) having a component, non-modulated in phase, at the frequency N.sub.c where .sub.c is the carrier used for the modulation N-PSK, and a carrier regeneration circuit to regenerate two sinusoidal signals in quadrature at the frequency .sub.c, with these signals being phase locked with respect to said non-modulated component in phase of the pre-conditioned signal.

A carrier recovery system for a receiver of a phase-modulated signal N-PSK, the system including a first pre-conditioning circuit of the signal received (S(t)), with the pre-conditioned signal (SP(t)) having a component, non-modulated in phase, at the frequency N.sub.c where .sub.c is the carrier used for the modulation N-PSK, and a carrier regeneration circuit to regenerate two sinusoidal signals in quadrature at the frequency .sub.c, with these signals being phase locked with respect to said non-modulated component in phase of the pre-conditioned signal.

The present disclosure relates to a method for demodulating a radio frequency (RF) signal comprising the steps of determining the nearest harmonic of a clock signal from a central frequency (Frx) of a received frequency band; and, if said nearest harmonic is in said frequency band, setting an intermediate frequency (IF) of a Near Zero Intermediate Frequency (NZIF) receiver to the difference (SpurOffset) between said central frequency (Frx) and said nearest harmonic.

Ultra-short pulse detection. At least some example embodiments are methods including: receiving by an antenna a series of ultra-short pulses of electromagnetic energy at a repetition frequency, the receiving creates a pulse signal; self-mixing or intermodulating the pulse signal by applying the pulse signal to a non-linear electrical device, thereby creating a modulated signal; and filtering the modulated signal to recover a filtered signal having an intermodulated frequency being the repetition frequency.

Embodiments of the present disclosure relate to an OFDM-based data transmission method and an apparatus. In one example method, a transmitting device generates a data packet. The data packet comprises at least one orthogonal frequency division multiplexing (OFDM) symbol. The OFDM symbol comprises N sequentially numbered subcarriers. The N subcarriers are divided into L subblocks. Each subblock of the L subblocks comprises N/L subcarriers including M pilot subcarriers. Start subcarriers of adjacent subblocks are adjacently numbered subcarriers. A numbering interval is the same for adjacent subcarriers in each subblock of the L subblocks. Each subblock of the L subblocks corresponds to one phase rotation signal. Signals carried on the subcarriers in each subblock of the L subblocks are signals obtained by multiplying original signals by a corresponding phase rotation signal. The transmitting device sends the data packet.

Systems, methods, and articles of manufacture, including computer program products, are provided for capacitive passive mixer baseband receivers with broadband harmonic rejection. In some embodiments, an apparatus is provided. The apparatus includes a receiver configured to receive an input signal and generate, based on the input signal, an in-phase portion and a quadrature phase portion. The apparatus further includes a harmonic rejection mixer comprising a plurality of capacitors, the plurality of capacitors encoded with a plurality of capacitance values, the harmonic rejection mixer configured to reduce harmonics in the input signal based on applying a quantity of the plurality of capacitance values to the input signal. The apparatus further includes a plurality of switches configured to activate the plurality of capacitors, the quantity of the plurality of predetermined capacitance values applied to the input signal based on a quantity of the plurality of capacitors that are active.

A communication system includes a receiving circuit and a phase error estimating circuit. The receiving circuit receives an input signal x, which has an input phase in a polar coordinate system. According to partial differentiation performed on the natural logarithm of a function f(x, ), the phase error estimating circuit generates an estimated phase error of the input signal x. f(x, ) represents a probability function of receiving the input signal x at the receiving circuit.

Systems, methods, and articles of manufacture, including computer program products, are provided for capacitive passive mixer baseband receivers with broadband harmonic rejection. In some embodiments, an apparatus is provided. The apparatus includes a receiver configured to receive an input signal and generate, based on the input signal, an in-phase portion and a quadrature phase portion. The apparatus further includes a harmonic rejection mixer comprising a plurality of capacitors, the plurality of capacitors encoded with a plurality of capacitance values, the harmonic rejection mixer configured to reduce harmonics in the input signal based on applying a quantity of the plurality of capacitance values to the input signal. The apparatus further includes a plurality of switches configured to activate the plurality of capacitors, the quantity of the plurality of predetermined capacitance values applied to the input signal based on a quantity of the plurality of capacitors that are active.

A 4 frequency-shift keying (4FSK) transceiver is provided. The 4FSK transceiver includes both a 4FSK transmitter and a 4FSK receiver. The 4FSK transmitter includes a voltage-controlled oscillator (VCO) and two data links coupled to the VCO for delivering two parallel streams of input data bits to the VCO. For each pair of parallel input data bits received from the two data links, the VCO outputs a modulated signal having one of four operating frequencies via 4FSK modulation. Separately, the 4FSK receiver includes a power divider, for dividing the multi-frequency modulated signal into two paths of two binary bit streams, and a pair of low-noise amplifiers (LNAs) separately coupled to the two paths and configured as a pair of band-pass filters for filtering two different subsets of the four operating frequencies from the two binary bit streams into two filtered binary bit streams.