63 results about "Amplifier distortion" patented technology

A radio comprises a power amplifier for amplifying a signal to be transmitted; a distortion compensation table storing distortion compensation coefficients for compensating a distortion of the power amplifier; a computing unit for updating the distortion compensation coefficient based on a difference between a transmission input signal and a transmission output signal; a bias voltage controller for applying a bias voltage to the power amplifier, said bias voltage determined based on a transmit control signal so as to maximize a power efficiency of the power amplifier.

The invention relates to linearization of a radio frequency (RF) power amplifier (5) by predistortion. Digital predistortion is performed (1) on received digitized base-band input signals to compensate for amplifier distortion. The resulting signal is converted to an analog signal via two D / A converters (2), after which analog frequency conversion is performed (3) on the analog signal to achieve a radio frequency (RF) signal. This radio frequency signal is exposed to analog predistortion (4) and thereafter amplified by the power amplifier.

A method of processing an Orthogonal Frequency-Division Multiplex (OFDM) signal having a plurality of data carriers and a plurality of unused carriers is disclosed. The method comprises transforming an original frequency-domain OFDM signal into a time domain signal and simulating the effect of a non-linear amplifier on the time-domain signal to provide a potentially distorted time domain signal. The potentially distorted time domain signal is transformed into a potentially distorted frequency domain signal and at least some of any values of the data carriers in the potentially distorted frequency domain signal are restored with corresponding values from the original frequency domain signal. At least some of the unused carriers in the at least partially restored frequency domain signal are scaled with a scaling factor. The scaled frequency domain signal is transformed into a temporary time domain signal and the temporary time domain signal is analysed for the presence of a peak or near zero amplitude value that would lead to distortion by said amplifier. If the signal includes such a peak or near zero value, the scaling, transforming and analysing are repeated with an increased scaling factor.

The augmented twin nonlinear two-box modeling and predistortion method for power amplifiers and transmitters provides power amplifier distortion modeling and predistortion linearization. A memoryless nonlinearity is combined with a memory polynomial function that includes cross-terms. The method can utilize an augmented forward twin-nonlinear two-box model, an augmented reverse twin-nonlinear two-box model, or alternatively, an augmented parallel twin-nonlinear two-box model. The present two-box models are validated in modeling and predistortion applications. Measurement results demonstrate the superiority of the present two-box models with respect to conventional state of the art models. The present two-box models lead to better accuracy with reduced complexity.

The invention is specific to the problem of PAPR (peak to average power ratio) presented by OFDM (orthogonal frequency division multiplexing) modulation of 60 GHz millimeter wave communication system, and provides a method of lowering OFDM signal PAPR by using selectivity mapping combined with LDPC (low density parity check) to generate matrix high density character. By adding a little bit information, PAPR of the millimeter wave OFDM transmission signal is effectively lowered. In a big rate situation, a construction plan of improving an LDPC non-systematic code is provided, which can remarkably lower PAPR and effectively improve the transmission performance in the case of nonlinearity power amplifier distortion of 60 GHz millimeter waves system. Compared with the traditional coding scheme, the invention can remarkably lower PAPR, improve the transmission performance of millimeter wave signal in the presence of device nonlinearity and excels other coding scheme in aspect of anti-power amplifier PA nonlinearity. At the same time, the non-systematic code which is designed and constructed in the method and device can still have a fine performance when the coding rate is big. The arithmetic implementation of the non-systematic code is simple, and parallel computation can be used by the non-systematic code, so that the method and the device of lowering 60 GHz communication system PAPR (peak to average power ratio) based on LDPC (low density parity check) coding mechanism has great practical value in high-speed millimeter waves OFDM system.

Apparatus and a corresponding method for predistorting an input signal applied to a radio frequency (RF) power amplifier, to compensate for amplifier distortion at high powers. The RF amplifier input and output signals are continuously monitored and difference signals are generated in an RF phase discriminator. The difference signals are converted to digital form and stored in a lookup table in the form of running averages of an RF amplifier gain compression value and an RF amplifier output phase value for each observed RF input power value. A predistorter module retrieves these values and predistorts the RF amplifier input by way of compensation.