A transmitter includes: a modulation circuit that modulates a data sequence using QAM by mapping the data sequence to only four symbols each of which differs in phase by 90 degrees from an adjacent one of the four symbols and at least two of which have different amplitudes; and a transmission circuit that wirelessly transmits the data sequence mapped to the four symbols through the modulation by the modulation circuit, by assigning the data sequence mapped to the four symbols through the modulation by the modulation circuit to different subcarriers for Orthogonal Frequency Division Multiplexing (OFDM).

Provided is a transmission method that improves data reception quality in radio transmission using a single-carrier scheme and/or a multi-carrier scheme. The transmission method includes: generating a plurality of first modulated signals s1(i) and second modulated signals s2(i) from transmission data, the plurality of first modulated signals s1(i) being signals generated using a QPSK modulation scheme, and the plurality of second modulated signals s2(i) being signals generated using 16QAM modulation; generating, from the plurality of first modulated signals s1(i) and the plurality of second modulated signals s2(i), a plurality of first signal-processed signals z1(i) and a plurality of second signal-processed signals z2(i) which satisfy a predetermined equation; and transmitting the plurality of first signal-processed signals z1(i) and the plurality of second signal-processed signals z2(i) using a plurality of antennas. A first signal-processed signal and a second signal-processed signal having identical symbol numbers are simultaneously transmitted at the same frequency.

A transmitter includes: a modulation circuit that modulates a data sequence using QAM by mapping the data sequence to only four symbols each of which differs in phase by 90 degrees from an adjacent one of the four symbols and at least two of which have different amplitudes; and a transmission circuit that wirelessly transmits the data sequence mapped to the four symbols through the modulation by the modulation circuit, by assigning the data sequence mapped to the four symbols through the modulation by the modulation circuit to different subcarriers for Orthogonal Frequency Division Multiplexing (OFDM).

A method of recovering information encoded by a modulated sinusoidal waveform having first, second, third and fourth data notches at respective phase angles, where a power of the modulated sinusoidal waveform is reduced relative to a power of an unmodulated sinusoidal waveform within selected ones of the first, second, third and fourth data notches so as to encode input digital data. The method includes receiving the modulated sinusoidal waveform and generating digital values representing the modulated sinusoidal waveform. A digital representation of the unmodulated sinusoidal waveform is subtracted from the digital values in order to generate a received digital data sequence, which includes digital data notch values representative of the amplitude of the modulated sinusoidal waveform within the first, second, third and fourth data notches. The input digital data is then estimated based upon the digital data notch values.

A system and method of estimating metric values from digital samples of received communications signal carrying symbols modulated in a selected first modulation format and symbols modulated in a second modulation format. The selected first modulation format can be selected from among multiple supported first modulation formats. The system can receive the digital samples in sample blocks a plurality of which constitute a data frame. Each sample block can comprise a first region that contains first samples corresponding to the selected first modulation format or overhead samples regardless of the selected first modulator format or an index of the sample block in the frame; a second region that contains second samples corresponding to a second modulation format regardless of the selected first modulator format or an index of the sample block in the frame; and a third region in which whether the samples are first samples or second samples depends on the selected first modulation format or the index of the sample block in the frame. The system estimates first metrics according to the selected first modulation format for each of the first samples and second metrics according to the second modulation format for each of the second samples. The system also estimates both first metrics and second metrics for each of the third samples and then selects valid ones of the first metrics and second metrics for the third samples in accordance with the selected first modulation format or the index of the sample block in the frame.

A method of recovering information encoded by a modulated sinusoidal waveform having first, second, third and fourth data notches at respective phase angles, where a power of the modulated sinusoidal waveform is reduced relative to a power of an unmodulated sinusoidal waveform within selected ones of the first, second, third and fourth data notches so as to encode input digital data. The method includes receiving the modulated sinusoidal waveform and generating digital values representing the modulated sinusoidal waveform. A digital representation of the unmodulated sinusoidal waveform is subtracted from the digital values in order to generate a received digital data sequence, which includes digital data notch values representative of the amplitude of the modulated sinusoidal waveform within the first, second, third and fourth data notches. The input digital data is then estimated based upon the digital data notch values.

A method and an apparatus for measuring a displacement of an object according to steps of: dividing a signal into an I signal and a Q signal according to a phase of the signal, wherein the signal is reflected by the object after a transmission signal having a plurality of frequencies is emitted toward the object by the radar measurement system; estimating a direct current (DC) component from an N-tuple information acquired from the I signal and the Q signal; removing the estimated DC component to correct the I signal and the Q signal; and measuring the displacement of the object based on the corrected I signal and Q signal are provided.

By changing frequencies of an oscillation signal and an injection signal, a frequency-converted self-injection-locked radar has an oscillation frequency different to a frequency of a transmitted signal from a transceiver antenna element such that the frequency-converted self-injection-locked radar with high sensitivity and penetration or with high sensitivity and low cost is achieved.

A method by which a base station transmits a reference signal in a wireless communication system can comprise the steps of: transmitting, to a terminal, information on a modulation method of a reference signal for estimating a phase difference between symbols in a time domain; and transmitting, to the terminal, the reference signal, for estimating the phase difference between the symbols, to which the modulation method is applied.

A system and method for waveform modulation includes encoding input digital data at selected phase angles of an unmodulated sinusoidal waveform. The encoding includes selectively reducing a power of the unmodulated sinusoidal waveform at the selected phase angles in accordance with bit values of the input digital data so as to respectively define first, second, third and fourth data notches in the modulated sinusoidal waveform. An encoded analog waveform is then generated from a digital representation of the modulated sinusoidal waveform. The encoding is performed so that energies associated with the first and third data notches are balanced and energies associated with second and fourth data notches are also balanced. Each of the energies corresponds to a cumulative power difference between a power of the unmodulated sinusoidal waveform and a power of the modulated sinusoidal waveform over a phase angle range subtended by one of the data notches.