The present invention is to generate a spatially phase modulated electron wave. A laser radiating apparatus, a spatial light phase modulator, and a photocathode are provided. The photocathode has a semiconductor film having an NEA film formed on a surface thereof, and a thickness of the semiconductor film is smaller than a value obtained by multiplying a coherent relaxation time of electrons in the semiconductor film by a moving speed of the electrons in the semiconductor film. According to the configuration, a spatial distribution of phase and a spatial distribution of intensity of spatial phase modulated light are transferred to an electron wave, and the electron wave emitted from an NEA film is modulated into the spatial distribution of phase and the spatial distribution of intensity of the light. Since the spatial distribution of phase of the light can be modulated as intended by a spatial phase modulation technique for light, it is possible to generate an electron wave having a spatial distribution of phase modulated as intended.

Systems and methods for linearizing a radio system are disclosed. In some embodiments, a radio system comprises an antenna array, transmit branches comprising respective power amplifiers, a predistortion subsystem comprising predistorters for the transmit branches respectively, a receive antenna element, a transmit observation receiver having an input coupled to the receive antenna element, and an adaptor. The predistorters predistort respective transmit signals to provide predistorted transmit signals to the respective transmit branches for transmission via respective active antenna elements in the antenna array. The transmit observation receiver is operable to receive, via the receive antenna element, a combined receive signal due to coupling between the receive antenna element and the active antenna elements. The adaptor is operable to generate a combined reference signal based on the transmit signals and configure predistortion parameters input to the predistorters based on the combined reference signal and the combined receive signal.

Provided is a distortion compensation device performing distortion compensation on a signal to be amplified by an amplifier, of which an internal state affecting a distortion characteristic varies, using a distortion compensation model, wherein the distortion compensation model includes a plurality of calculation models having respective distortion compensation characteristic for the amplifier in different internal states, and a combiner combining the plurality of calculation models at a combination ratio corresponding to the internal state that varies.

Systems and methods for providing wireless communication impairment correction using non-linear iterative precoding by a transmitter device are disclosed. The transmitter may exploit the non-linear transmit indications, and perform digital non-linear multiple input multiple output (MIMO) precoding of a transmit signal to improve the error vector magnitude (EVM) at the intended receiver device and/or reduce the adjacent channel leakage ratio (ACLR) at the unintended receiver devices. The non-linear transmit indications may comprise amplitude modulation to amplitude modulation (AM-AM) and amplitude modulation to phase modulation (AM-PM) indications. In operation, the non-linear transmit indications may be received from the intended receiver devices or may be measured by the transmitter device.

Pre-distorted transmitters operable over a wide range of frequencies including a plurality of predetermined frequency bands are provided. The transmitters include a programmable digital up-converter and a programmable digital down-converter, an ADC, a DAC, a power amplifier and at least one analog filter arranged along a transmit signal path and a feedback signal path.

A transmission method simultaneously transmitting a first modulated signal and a second modulated signal at a common frequency performs precoding on both signals using a fixed precoding matrix and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.

A predistortion circuit for a wireless transmitter includes a signal input configured to receive a baseband signal. Further, the predistortion circuit includes a predistorter configured to generate a predistorted baseband signal using the baseband signal and a select of one of a first predistorter configuration and a second predistorter configuration.

Various embodiments of the present disclosure relate to transmitter systems, methods, and instructions for signal predistortion. The transmitter system includes a primary digital predistortion (DPD) layer and a secondary DPD layer. The primary DPD layer includes a DPD coefficient estimation module configured to update primary signal generation coefficients based on comparing a secondary predistorted signal (U.sub.out) with a detected feedback signal (Y.sub.out), and a primary distortion compensation processing module configured to generate a primary predistorted signal (U.sub.out′) based on the secondary predistorted signal (U.sub.out) using the updated primary signal generation coefficients. The secondary DPD layer includes a signal characteristic estimation module configured to update secondary signal generation coefficients based on comparing an input signal (S.sub.in) with the detected feedback signal (Y.sub.out), and a secondary distortion compensation processing module configured to generate the secondary predistorted signal (U.sub.out) based on the input signal (S.sub.in) using the updated secondary signal generation coefficients.

Systems and methods are disclosed herein for providing efficient Digital Predistortion (DPD). In some embodiments, a system comprises a DPD system comprising a DPD actuator. The DPD actuator comprises a Look-Up Table (LUT), selection circuitry, and an approximate multiplication function. Each LUT entry comprises information that represents a first set of values {p.sub.1, p.sub.2, . . . , p.sub.k} and a second set of values {s.sub.1, s.sub.2, . . . , s.sub.k} that represent a LUT value of s.sub.1.Math.2.sup.p.sup.1+s.sub.2.Math.2.sup.p.sup.2+ . . . +s.sub.k.Math.2.sup.p.sup.k where each value s.sub.iϵ{+1,−1} where k≥2. The selection circuitry is operable to, for each input sample of an input signal, select a LUT entry based on a value derived from the input sample that is indicative of a power of the input signal. The approximate multiplication function comprises shifting and combining circuitry that operates to, for each input sample, shift and combine bits that form a binary representation of the input sample in accordance with {p.sub.1, p.sub.2, . . . , p.sub.k} and {s.sub.1, s.sub.2, . . . , s.sub.k} to provide an output sample.

Systems and methods are disclosed herein for selectively compensating for a specific Intermodulation Distortion (IMO) product(s) of an arbitrary order in a transmitter system. In some embodiments, a method of compensating for one or more specific IMO products in a concurrent multi-band transmitter system comprises generating an IMO correction signal for a specific IMO product as a function of two or more frequency band input signals for two or more frequency bands of a concurrent multi-band signal, the IMO product being an arbitrary order IMD product. The method further comprises frequency translating the IMD correction signal to a desired frequency that corresponds to a Radio Frequency (RF) location of the specific IMO product and, after frequency translating the IMO correction signal to the desired frequency, utilizing the IMO correction signal to compensate for the specific IMO product.