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Modern communication networks require improved signal quality and spectrum efficiency. Modern wireless communication relies heavily on the multiple input multiple output (MIMO) technology to improve spectrum efficiency and achieve faster data rates. However, the performance of MIMO systems is significantly hampered by non-linear distortions in power amplifiers (PA), especially under dynamic operating conditions. Traditional methods to reduce these distortions often lack the adaptability required for effective optimization. The proposed dynamic nonlinear distortion adaptive optimization analysis (DNDAOA) therefore introduces an adaptive approach that dynamically adjusts the pre-distortion signals using real-time feedback mechanisms. DNDAOA effectively reduces non-linear distortions and thus improves the performance of MIMO systems. Simulation results show that DNDAOA significantly increases spectrum efficiency, reduces error rates, and improves signal quality. This method is widely used in areas such as wireless telecommunications, internet of things (IoT), autonomous vehicles, and smart infrastructure, driving advances in connectivity, reliability, and data integrity. [ABSTRACT FROM AUTHOR]

This paper presents a new high-efficiency two-way Doherty Power Amplifier (DPA) with a modified output matching structure for Wideband Code Division Multiple Access (W-CDMA) low-to-medium power base station applications. A blended design is proposed using the symmetrical topology of equal rated power amplifying devices with unequal output impedances for the carrier and peaking amplifier to achieve enhanced efficiency and desired linearity in 1900 MHz band. The proposed output circuit modifications encompass the usage of parasitic capacitor compensation technique for the carrier amplifier, optimum offset line along with the Doherty combiner to achieve high efficiency over 6 to 10 dB extended range of back-off operation. The measured results of the DPA demonstrate a Power Added Efficiency (PAE) of more than 49.9% at +34 dBm W-CDMA signal power, which is between 8 and 8.5 dB back-off from the peak power level of 42.2 dBm. The DPA has a large signal power gain of 13 dB at 1960 MHz. Further, the PAE is 39.5% and linearised Adjacent Channel Power Ratio (ACPR) is −46.2 dBc, both at 10 dB back-off from peak power. In these back-off power levels, this implementation provides significant efficiency improvement using symmetrical devices and with excellent linearity. [ABSTRACT FROM AUTHOR]

Computational intelligent systems are becoming an increasingly attractive solution for power amplifier (PA) behavioural modelling, due to their excellent approximation capability. This paper utilizes an adaptive fuzzy logic system (AFLS) for the modelling of the highly nonlinear MIMIX CFH2162-P3 PA. Moreover, PA’s inverse model based also on AFLS has been developed in order to act as a pre-distorter unit. Driving an LTE 1.4 MHz 64 QAM signal at 880 MHz as centre frequency at PA’s input, very good modelling performance was achieved, for both PA’s forward and inverse dynamics. A comparative study of AFLS and neural networks (NN) has been carried out to establish AFLS as an effective, robust and easy-to-implement baseband model, which is suitable for inverse modelling of PAs and capable to be used as an effective digital pre-distorter. Pre-distortion system based on AFLS achieved distortion suppression of 84.2%, compared to the 48.4% gained using the NN-based equivalent scheme. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear autoregressive with exogenous inputs (NARX) digital pre-distortion scheme to linearize power amplifiers is proposed. The proposed NARX digital pre-distortion gives better accuracy and spectral leakage suppression compared with other commonly used Volterra-based techniques. The stability criterion of the NARX digital pre-distortion is derived from the frequency domain analysis. Simulation is carried out with a 20 MHz single carrier long-term evolution signal and two-carrier long-term evolution signal and instantaneous to average ratio of 6.2 dB at 0.01% complementary cumulative distribution function (CCDF). The results of simulation analysis show a slight improvement in adjacent channel leakage ratio performance with 30% reduction in the number of floating point operations compared with conventional pre-distortion techniques. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A digital polar transmitter is introduced using 9-b thermometer-coded uniform cells for wideband signal. By analyzing amplitude and phase paths impairment which causes both in-band and out-of-band distortions, a 960-MHz delay tuner is designed for precise amplitude and phase alignment. Furthermore, two digital pre-distortion algorithms for digital power amplifier (DPA) are implemented and compared. Importantly, an on-chip dc–dc converter is included for direct battery connection and output power control. Boosted cascode gate bias improves PA efficiency at low power region. The proposed design is fabricated using a 55-nm RF CMOS technology. This DPA including digital amplitude modulation (AM) filtering achieves peak power of +21.9 dBm with 41% drain efficiency in continuous-wave measurements. It achieves EVM of 2.9% with 20-MHz IEEE 802.11ac compliance of 256-QAM OFDM signal, and also achieves EVM of 4.5% (CC0)/4.8% (CC1) with 40-MHz LTE-A carrier aggregation compliance of 64-QAM OFDM signal. [ABSTRACT FROM AUTHOR]

Power amplifier (PA) plays a key role in transceivers for mobile communication systems and the improvement of the linearity of the PA becomes an objective of first importance. This paper proposes a novel linearization method for PA based on the Legendre wavelet possessing rich properties, so as to this technique combines the advantages of piecewise linear functions and orthogonal polynomials for pre-distortion linearization. Pre-distorter (PD) has been identified and power spectrum also has been compared based on the data of the PA characteristics for WCDMA and OFDM signals, respectively. The computational results demonstrate that a quite significant improvement in linearity is achieved and the PD is stable and effective. The most attractive aspects of the presented method is that the Legendre wavelet bases can approximate static nonlinearity of the PA with different level of resolution and lower order piecewise polynomials than that of other polynomials. [ABSTRACT FROM AUTHOR]

OFDM technology has become the core technology of DTMB system. The high Doherty power amplifier can effectively improve the peak-average power ratio of OFDM system, but with poor linear performance. This paper starts with improving linear performance of Doherty power amplifier, analyzes the nonlinear model of power amplifier, presents a construction method of nonlinear performance model of Doherty power amplifier, gets the corresponding nonlinear performance curve, and then presents a design of pre-distorter which can improve system linear performance. The nonlinear performance curve is used to do the simulation. The result shows that the system linear performance is improved greatly. [ABSTRACT FROM AUTHOR]

A phase-delay cold-FET pre-distortion linearizer technique is proposed to improve the gain compensation ability compared with the conventional cold-FET pre-distortion linearizer. The gain expansion analysis of the power amplifier (PA) cascading with a pre-distortion linearizer and the comparison with the conventional linearizer and the proposed phase-delay linearizer are provided in this paper. To demonstrate the feasibility of this concept, a single-ended V-band cascode PA with the 90^\circ phase-delay linearizer and a differential K-band common-source PA with the 180^\circ phase-delay linearizer are developed to verify the characteristics. The V-band PA implemented in 90-nm CMOS process exhibits the output 1-dB compression power (OP1~dB) of 13.7 dBm and the power-added efficiency (PAE) at OP1~dB of 14.3%. The K-band PA implemented in 0.18- \mum CMOS process demonstrates 17.5-dBm OP1~dB and 13.6% PAE at OP1~dB. [ABSTRACT FROM AUTHOR]

For adaptive improvement of linearity above a 12 dB PAPR for 64QAM WiMAX, a complementary feedback loop in a differential amplifier is adopted as a pre-distorter that is realized using an NMOS cell operating in the triode region in order to compensate the gm3, the third order transconductance, of the differential amplifier. The power amplifier has been implemented in 0.18 μm CMOS technology, and the chip size is 870 μm × 1050 μm. The proposed PA obtains the 42% efficiency at P1dB while improving the IMD by more than 10 dB above 15 dBm output power levels. It shows a gain of as much as 14.5 dB, and a return loss below -12 dB for 2.3–2.4 GHz operation. Finally, the fabricated PA complies with the spurious emission of WiMAX standards up to 22 dBm. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:833–836, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25062 [ABSTRACT FROM AUTHOR]

This paper deals with the system and circuit-level aspects of an ultra-low-power robust wireless node for an asymmetric wireless link. A single building block TX front-end for a frequency hopping spread spectrum (FHSS) transmitter implemented in silicon-on-anything (SOA) bipolar technology is presented. It is realized with a directly modulated RF cascoded Colpitts power voltage-controlled oscillator (VCO), a frequency locked loop for center frequency calibration, and a digital pre-distortion algorithm for accurate frequency bins synthesis. The TX front-end draws only 1 mA at -18 dBm output power. By combining digital system techniques for frequency hopping and merging the VCO and the power amplifier (PA), a robust solution is obtained for indoor ultra-low-power wireless links. The proposed pre-distortion concept allows reduction of the hardware complexity, while the combination of a cascode output buffer and a common-collector Colpitts VCO allows us to reduce the complete FHSS front-end to a single building block that directly drives the antenna through a balun. A dedicated digital algorithm on the receiver side reduces the center frequency offset from a maximum value of 8.2 MHz to less than 8 ppm avoiding the use of any crystal on the transmitter side. Precision in the hopping synthesis is obtained by employing a ST-DFT based demodulator with differential encoding and an offset sending technique. The novel FHSS-predistortion concept has been verified by realizing a full wireless link that achieves a bit error rate better than 1.1% at -25 dBm output power while transmitting across an 8 meters indoor non-line-of-sight (NLOS) path. [ABSTRACT FROM AUTHOR]