Systems and methods of performing decomposition of baseband and bandpass signals into a sum of time truncated periodic components with spectral masks defined by the set of Fourier coefficients of the components and the pulse used for time truncation are provided. In one exemplary embodiment, a user equipment device includes a circuitry operable to output a set of truncated periodic components that collectively represents a sample of an input signal having information and a set of power amplifier circuitry electrically coupled to the circuitry and operable to amplify the set of truncated periodic components that collectively represents an amplified sample of the input signal.

An amplifier (100) is provided for amplifying a complex input communication signal (109) having an in-phase and quadrature component. The amplifier has a modulation circuitry (110) configured to convert the input signal to quantized samples (111) by performing oversampling, where the quantized samples represent a finite set of constellation points; and a phase mapping circuitry (120) configured to map the quantized samples onto two constant-envelope phase-modulated signals (121, 122) selected from a finite set of constant-envelope phase-modulated signals (172, 221-224) having a carrier frequency f.sub.c (171) and (different) constant phases. A first and second power amplifier (130, 140) is configured to amplify the two constant-envelope phase-modulated signals by a gain G; and a combiner (150) is configured to combine the two amplified constant-envelope phase-modulated signals (131, 141) thereby obtaining a complex output communication signal (151) with the carrier frequency f.sub.c representing an amplification (161) of the complex input communication signal (109).

An amplifying apparatus includes: a signal splitter that splits an amplification-target signal into a first input signal and a second input signal on the basis of the amplitude of the amplification-target signal; a first amplifier that amplifies the first input signal; a second amplifier that amplifies the second input signal; a synthesizing circuit that synthesizes a signal obtained after the amplification by the first amplifier and a signal obtained after the amplification by the second amplifier; and a discrete variable power supply that switches a power supply voltage applied to the output side of each of the first amplifier and the second amplifier on the basis of an amplitude range in which the amplitude of the amplification-target signal is included.

An outphasing amplifier includes a first amplifier, a second amplifier, a first coupler coupling a first signal and a third signal, a second coupler coupling a second signal and a fourth signal, a first impedance converter inputting the first signal coupled with the third signal, a second impedance converter inputting the second signal coupled with the fourth signal, a combiner combining the first and the second signals output from the first and the second impedance converters and outputting an output signal, and a signal processor outputting the first signal having a first phase to the first amplifier, outputting the second signal having a second phase to the second amplifier, outputting the third signal having at least one of a third phase and a first amplitude to the first coupler, and outputting the fourth signal having at least one of a fourth phase and a second amplitude to the second coupler.