Frequency-Selective Predistortion Linearization of RF Power Amplifiers (original) (raw)
Related papers
2007
Digital predistortion of a baseband signal is a well-known method of power amplifier (PA) linearization used to reduce adjacent channel interference (ACI) in a non constant envelope modulation system. This paper discusses the application of adaptive digital baseband predistortion linearization to radio frequency (RF) power amplifiers (PAs) that exhibit memory effects. This technique is a highly cost- effective way to linearize Power amplifiers (PAs), but most existing architectures assume that the PA has a memoryless nonlinearity. For wider bandwidth applications such as wideband code-division multiple access (WCDMA) or wideband orthogonal frequency-division multiplexing (W- OFDM), PA memory effects can no longer be ignored. In this paper a new technique for adaptation of digital predistorter that considers memory effects in power amplifiers is proposed. This method is a combination of two techniques, memory polynomial predistortion and slope-dependent method. This new technique is validated by using a 1.9 GHz 60 W LDMOS power amplifier and various signals such as 2- carrier CDMA and 3-carrier CDMA.
Linearization of RF power amplifiers using an enhanced memory polynomial predistorter
NORCHIP 2012, 2012
Radio frequency power amplifiers (PAs) play a keyrole in transceivers for mobile communications and their linearity is a crucial aspect. In order to meet the linearity requirements dictated by the standard at a reasonable efficiency, the usage of a linearization technique is required. In this paper we propose a linearization by means of a new type of digital predistorter, defined directly in the I-Q domain. The architecture of the proposed predistorter can be understood as an enhancement of the memory polynomial model (MPM) by means of additional I-Q terms. The usage of the proposed predistorter allows a more robust linearization of the whole RF transmitter because the enhancement of the model with additional I-Q terms can guarantee a more versatile compensation which is beneficial when the distortion comes from the joint contribution of the PA and the quadrature modulator. The proof of concept is achieved by measurements on a commercial PA in GaN technology and the performance of the proposed predistorter is illustrated.
Analog predistortion linearizer for high-power RF amplifiers
IEEE Transactions on Microwave Theory and Techniques, 2000
Analog predistortion linearizer for the high power amplifier of CDMA base station has been developed. To suppress the spectral regrowth in the adjacent channels effectively, the odd order intermodulation distortions should be cancelled. For the purpose, the predistorter, which can cancel the 3rd and 5th intermodulation distortions independently, has been employed. The implemented predistorter linearized the RF amplifier with average power 45 dBm at 2.37-2.4GHz band. 9dB suppression of spectral regrowth was achieved for CDMA signal over 30MHz bandwidth. 0-7803-5687-X/00/$10.00 0 2000 IEEE
Efficient RF power amplifiers used in third generation systems require linearization in order to reduce adjacent channel inter-modulation distortion, without sacrificing efficiency. Digital baseband predistortion is a highly cost-effective way to linearize power amplifiers (PAs), but most existing architectures assume that the PA has a memoryless nonlinearity. For wider bandwidth applications such as wideband code-division multiple access (WCDMA) or wideband orthogonal frequency-division multiplexing (W-OFDM), PA memory effects can no longer be ignored. In this paper we proposed a technique for adaptation of digital predistorter that considers memory effects in power amplifiers.
2012
This paper presents an overview of different Digital Predistortion (DPD) techniques used in microwave Power Amplifier (PA) linearization. Different DPD approaches are considered with both static and dynamic (memory effects) behavioral models. The most suitable solutions for facing the new challenges to linearize high-bandwidth amplifiers are discussed, which is demanded by most of the new telecommunications standards and emergent technologies.
A Convergence-Free Predistortion Technique for Adaptive Linearisation of RF Power Amplifiers
Analog Integrated Circuits and Signal Processing, 2004
Adaptive digital baseband predistortion is a well-known linearisation technique for removing intermodulation products that radio frequency power amplifiers (PAs) introduce. This paper proposes a new baseband predistortion method that is based on a non-iterative, fast adaptation algorithm without convergence restrictions. The response of the PA in a batch of training magnitude stimuli is used for the computation of the predistortion gain. The latter is directly extracted in rectangular form without prior transformations and AM/AM and AM/PM non-linearities sequential estimation. The influence of the gain table size and the imperfections of the modulator and demodulator in the method's performance are examined. Experimental measurements of an in-house prototype show a linearity improvement of about 25 dB.
Adaptive digital baseband predistortion for RF power amplifier linearization
High Frequency Electronics, 2006
Power amplifiers (PAs) are vital components in many communication systems. To be transmit-ted wirelessly, a signal must be amplified with high fidelity so as to account for attenuation through the channel or propagation medium. The linearity of a PA response constitutes ...
Analysis of amplitude dependent memory effects in RF power amplifiers
Memory effects are usually defined as amplitude or phase changes in intermodulation (IM) products, caused by changes in modulation frequency. Since 5th degree nonlinearity causes not just IM5 but also IM3 terms, and since the amount of 5th degree nonlinearity from IM3 is amplitude-dependent, memory effects also become amplitude-dependent. These effects are caused by varying node impedances inside the frequency zones (dc, fund, 2nd harm...), and the total amount of amplitude-dependent memory is the sum of the memory converted from all the frequency zones. The flatness of the normalized IM3 presented in this paper is a good measure of how much memory exists and how easily a PA can be linearized.
Optimum design of a predistortion RF power amplifier for multicarrier WCDMA applications
IEEE Transactions on Microwave Theory and Techniques, 2000
This paper provides a design guide for optimum design of an RF power amplifier with a predistortion linearizer. For a two-tone signal, three performance degradation factors, higher order terms, amplitude, and phase mismatches are analyzed quantitatively. The results are implemented to the design of optimized predistortion power amplifier for a WCDMA signal application. For the experiments, a 2.4-GHz class-AB power amplifier is fabricated using an LDMOSFET with a 30-W peak envelope power. A simple third-order predistorter is used to measure the relative phases of the harmonics, as well as to linearize the amplifier. The performance of the optimized predistortion power amplifier is excellent for a IS-95 code-division-multiple-access signal. Finally, a method for reducing the memory effects of the amplifier is devised to get a good cancellation performance for a wide-band signal, and the performance degradation caused by the memory effects is analyzed. For a forward-link four-carrier WCDMA signal, the predistortion power amplifier delivers an adjacent channel leakage ratio of 46 dBc at a 4-W average output power with a cancellation of 13.4 dB.