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In this study, we proposed a pre-distorted driver of a power amplifier in which the driver stage can serve as a pre-distorter of the power stage. In order to secure the linearity of the power amplifier, AM-PM distortions according to the input power of the common-source (CS) and two stacked-FET structures were analyzed and compared with the simulated results. Based on the analyzed AM-PM distortions of the two structure, it was verified that the driver stage with CS structure can act as a pre-distorter of the power stage with the two stacked-FET structure by optimizing the bias voltages of the two structures. The Ka-band power amplifier was designed with a 65-nm CMOS process to verify the feasibility of the proposed pre-distorted driver stage. At 28 GHz, the measured P1dB, saturated output power (P $_{\mathrm {SAT}}$ ), and peak power-added efficiency (PAE) were 18.6 dBm, 19.7 dBm, and 32.9%, respectively. The measured small signal gain was 24.1 dB. When 5G-NR modulation signals (64-QAM, 100-Msym/s, 9.7-dB PAPR) were used, under conditions where the EVM was less than –25 dB, the measured output power and ACLR were 13.3 dBm and –29.4 dBc, respectively.

One of the major problems faced in digital communication systems is Inter-Symbol Interference (ISI), induced by the propagation channel in the single carrier based systems. Classic digital equalization techniques based on pilot training sequences become tedious in the presence of nonlinear power amplifiers. The existing techniques for digital pre-distortion need a high transmitter computation complexity and those for the post-distortion require pilot overhead. In this review, we focus on fully generic blind processing for both channel equalization and power amplifier post-distortion. We propose a receiver based on two complex-valued neural networks (CV-NN). The first CV-NN is dedicated to generic blind equalization (GBE) to mitigate ISI. The second one is used for generic blind post-distortion compensation (GBPDC) of the power amplifier nonlinearity (PANL). The GBE and the GBPDC have no prior information about the transmission channel, the used constellation, and the PA model. For the first CV-NN, we consider an updated probability density fitting (PDF) based criteria, corresponding to many assumed possible constellations, that are used jointly with an automatic modulation classification (AMC) based on the k-nearest neighbors (KNN) algorithm. For the second CV-NN, we use the final updated PDF criterion resulting from the first CV-NN training process. Numerical results show that our generic blind Deep learning-based signal receiver formed with the two CV-NNs is effective in alleviating the two coupled signal distortions: the ISI and the PANL. Compared with the state-of-the-art methods, banking on a supervised post-distortion compensation and channel equalization, the proposed generic blind DL-based scheme exhibits good detection performance.

Lookup table (LUT) is an efficient digital predistortion technique for mitigating the pattern dependent distortion in the field of underwater wireless optical communication (UWOC) system. However, the complexity of LUT grows geometrically when applied with high-order QAM modulation formats with multi-pattern length sequences. The complexity reduction of LUT is essential for practical applications. In this paper, we study the patterning effects of LUT predistortion and propose to reduce the LUT complexity by pruning its table entries aided with multi-modulus weighted strategy. The size of LUT has been reduced significantly in experiments, which shows that the complexity of the proposed MMW-RLUT only accounts for 17.6%, 9.8%, 4.9% and 14% of full-size LUT for 64QAM, normal 32QAM, square geometrical shaping (SGS) 32QAM and 16QAM modulated UWOC system, without degradation of performance. [ABSTRACT FROM AUTHOR]

In this article, we propose a CMOS active balun targeting high linearity up to high voltage swing and over wide bandwidth for direct RF sampling applications. All the blocks of this active balun are derived using a common highly linear building block (HLBB). The HLBB is designed using an inverter with strong source degeneration. To increase the linearity of this HLBB further, its nonlinearity mechanisms are analyzed in detail. A bootstrapping technique is included in the HLBB to reduce the dominant nonlinearity. Furthermore, a pre-distortion technique cancels most of the non-linearity of the output driving stages. All the linearization techniques proposed are robust to process, voltage, and temperature (PVT) changes. The measured results of the active balun realized on-chip in a 22-nm FDSOI CMOS shows $ < -$ 44-dBc third harmonic distortion (HD3) up to 1.5- $\text{V}_{\textrm {p-p}}$ output swing over 0.01–5.4 GHz. The measured gain and phase errors of the balun action are less than 0.5 dB and $\pm 5{^\circ }$ , respectively. The chip is powered from a 5-V supply and dissipates 925 mW. [ABSTRACT FROM AUTHOR]

Mutual interference is a crucial issue for the visible light communication (VLC) systems to be addressed, including both co-channel interference (CCI) and inter-carrier interference (ICI). In this paper, to solve the CCI problem, a novel optical attocell network is introduced, which can be regarded as a hybrid network based on both single frequency network and multi-frequency network. Meanwhile, to eliminate the ICI, a pre-distorted enhanced asymmetrically clipped DC biased optical orthogonal frequency division multiplexing (PEADO-OFDM) approach is designed. In addition, the corresponding properties of PEADO-OFDM are analyzed, and different modulation schemes are employed for downlink and uplink in the same ADO-OFDM modulation framework to reduce the complexity of user processing. Simulation results indicate that the proposed PEADO-OFDM scheme outperforms the conventional ADO-OFDM approach in terms of bit error rate, while the processing latency and computational complexity are greatly reduced at the receiver.

In this paper, an adaptive modulation scheme for visible light communication (VLC) system based on partially pre-distorted layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) is proposed. The clipping noise that falls on the higher layers in the conventional LACO-OFDM results in inter layer interference, which can be eliminated by the operation of pre-distortion at the expense of extra power consumption. The proposed partially pre-distorted scheme makes a tradeoff between error propagation and power cost to suit different transmission environments. The probability distribution functions of the conventional and pre-distorted LACO-OFDM schemes are analyzed and compared and the layers that should be pre-distorted in the proposed scheme is decided adaptively by maximizing the achievable rate. The computational complexity of the proposed scheme is also investigated, which is acceptable compared with the previous schemes. Simulation results show that the proposed scheme has a superior bit error rate performance compared with the conventional and pre-distorted LACO-OFDM schemes.

Organic photo-detector (OPD) is lightweight and physically flexible. It can transform plastic or glass into smart surfaces. Visible light communication (VLC) is considered as one of the promising technologies for the future wireless communications. VLC combines the advantages of lighting and communication simultaneously. Besides, it can be deployed using existing lighting infrastructure; hence little extra cost is needed to provide this wireless communication. As the OPD has a large optical detection area, it would be interesting to employ the OPD as VLC receiver (Rx). If the OPD can be used in the VLC systems, it can benefit the Internet-of-Thing (IoT) networks by providing efficient human-to-machine and machine-to-machine communications. However, implementing VLC using OPD Rx is challenging. Due to the slow charging and discharging processes of the OPD, the optical-to-electrical response speed is limited. Besides, the OPD requires external bias to be operated. Here, we propose and demonstrate using pre-distortion scheme for pulse-amplitude-modulation (PAM) signal to a self-powered PCBM:P3HT OPD to enhance the VLC transmission performance. The operation of the self-powered PCBM:P3HT OPD is discussed. Both experiments using PAM-2 and PAM-4 (with and without pre-distortion) are evaluated. The performance, requirement and capability limitations of the pre-distortion schemes are also analyzed and discussed by using numerical simulations.

A 10-GHz sub-sampling phase-locked loop (PLL) (SSPLL) with wideband low-noise frequency modulation for frequency-modulated continuous-wave (FMCW) radar applications is presented. It uses a low-power charge-integrating digital-to-analog converter (QDAC) to tune the voltage-controlled oscillator (VCO) in a two-point modulation architecture. A full background calibration engine corrects for the nonlinearities in the QDAC modulation path. Implemented in a 28-nm CMOS process, the SSPLL consumes 11.7 mW (of which less-than 0.5 mW from the QDAC) to generate a 23.6-MHz/ $\mu \text{s}$ sawtooth chirp-slope with 28-kHz rms-frequency-error for 1.21-GHz chirp-bandwidth. [ABSTRACT FROM AUTHOR]

Mutual interference is a crucial issue for the visible light communication (VLC) systems to be addressed, including both co-channel interference (CCI) and inter-carrier interference (ICI). In this paper, to solve the CCI problem, a novel optical attocell network is introduced, which can be regarded as a hybrid network based on both single frequency network and multi-frequency network. Meanwhile, to eliminate the ICI, a pre-distorted enhanced asymmetrically clipped DC biased optical orthogonal frequency division multiplexing (PEADO-OFDM) approach is designed. In addition, the corresponding properties of PEADO-OFDM are analyzed, and different modulation schemes are employed for downlink and uplink in the same ADO-OFDM modulation framework to reduce the complexity of user processing. Simulation results indicate that the proposed PEADO-OFDM scheme outperforms the conventional ADO-OFDM approach in terms of bit error rate, while the processing latency and computational complexity are greatly reduced at the receiver. [ABSTRACT FROM AUTHOR]

Semiconductor optical amplifier (SOA) is regarded as a promising candidate to amplify the optical signal in next-generation access network, especially for O-band signal transmission. However, the SOA-based system suffers from the pattern-dependent effect due to its gain saturation. Compared to digital signal processing (DSP) at receiver, DSP in the transmitter can reduce implementation complexity, which is attractive for the multi-user system. In this paper, we propose three methods to mitigate the pattern-dependent effect in SOA and compare their performance based on: 1) look-up-table (LUT) considering pattern-dependent effect, 2) pre-distortion without considering pattern-dependent effect, 3) probabilistic shaping (PS). The performance of three mitigation methods is investigated in an intensity modulation with direct detection (IM/DD) 4-ary pulse-amplitude-modulation (PAM-4) transmission system at O-band. Our research results show that all these schemes can improve the receiver dynamic range of PAM-4 signals at 50 Gbit/s and 100 Gbit/s. Moreover, PS and LUT can also improve the receiver dynamic range of 75-Gbit/s PAM-8 signals. [ABSTRACT FROM AUTHOR]

In this paper, we propose and experimentally demonstrate an optical self-interference cancellation (OSIC) system with baseband predistortion for wideband over-the-air in-band full-duplex (IBFD) communication. The key factors of OSIC bandwidth limitation are analyzed, and the solution toward it is proposed for the first time. Experimental results show that, by traditional OSIC under over-the-air condition, only narrow even zero band is with enough cancellation depth to satisfy IBFD. But with our proposed baseband predistortion scheme, deep OSIC depth is achieved over the whole 1 GHz/5 GHz baseband within the total 7–25 GHz available band of horn antennas. The employment of baseband predistortion obviously broadens the cancellation bandwidth of an EML-based OSIC system. The largest OSIC bandwidth for over-the-air IBFD communication is demonstrated so far.

In this paper, an adaptive modulation scheme for visible light communication (VLC) system based on partially pre-distorted layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) is proposed. The clipping noise that falls on the higher layers in the conventional LACO-OFDM results in inter layer interference, which can be eliminated by the operation of pre-distortion at the expense of extra power consumption. The proposed partially pre-distorted scheme makes a tradeoff between error propagation and power cost to suit different transmission environments. The probability distribution functions of the conventional and pre-distorted LACO-OFDM schemes are analyzed and compared and the layers that should be pre-distorted in the proposed scheme is decided adaptively by maximizing the achievable rate. The computational complexity of the proposed scheme is also investigated, which is acceptable compared with the previous schemes. Simulation results show that the proposed scheme has a superior bit error rate performance compared with the conventional and pre-distorted LACO-OFDM schemes. [ABSTRACT FROM AUTHOR]

An adaptive compression method in intermediate frequency band digitized radio over fiber is proposed for mobile fronthaul, aiming at reducing the transmission rates. The proposed method uses radio channel state information parameters to control fronthaul compression. The simulation results demonstrate the ability of the proposed method on reducing the quantization error, allowing the use of lower (4-bits) quantizer resolution for 64-QAM modulated signals, providing 2:1 compression rate with near zero EVM. In addition, our proposed method surpasses $\mu $ -law and $A$ -law compression techniques and performs in shorter times than 5G latency target (1 ms). Finally, the performance of uncompressed and compressed signal is assessed experimentally in 20 km of fiber transmission. [ABSTRACT FROM AUTHOR]

This paper describes a 23-GHz digital bang–bang phase-locked loop (PLL) fabricated in 65-nm CMOS for millimeter-wave frequency-modulated continuous-wave radars. The presented circuit aims to generate a fast sawtooth chirp signal that grants significant advantages with respect to the more conventional triangular waveform. Such a signal, however, features a very large bandwidth that requires the adoption of a two-point injection scheme. This paper, after intuitively discussing how the nonlinearity of the digitally controlled oscillator affects the accuracy of frequency modulation, presents a novel automatic pre-distortion engine, operating fully in background, which linearizes the tuning characteristic. The 19.7-mA fractional-N PLL having an rms jitter of 213 fs and an in-band fractional spur of −58 dBc is capable of synthesizing fast chirps with 173-MHz/ $\mu \text{s}$ maximum slope and an idle time of less than 200 ns after an abrupt frequency step with no over or undershoot. [ABSTRACT FROM AUTHOR]

We present high-speed single-channel discrete multitone (DMT) operations of directly modulated 850-nm vertical-cavity surface-emitting lasers (VCSEL). Successful transmission of 135 Gb/s over 10 m of OM4 multi-mode fiber (MMF) and 114 Gb/s over 550 m is demonstrated below the 7 % overhead hard-decision forward error correction (FEC) bit error rate (BER) limit. At higher BER limits, i.e. 20%overhead soft-decision FEC, which are of arising interest for these high-speed short-range links, data rates of up to 161 Gb/s are presented. This is enabled by high-bandwidth low-noise VCSEL, which operate in quasi-single mode to overcome the mode dispersion limitations of the MMF. The applied modulation format is DMT in combination with a Volterrafilter- based pre-distortion approach, which pre-compensates the linear and nonlinear behavior of the transmission system, primarily the digital-analog converter, the VCSEL, the MMF, and the photoreceiver. Furthermore, a detailed investigation of the predistortion is given by experimental means, showing that the optimum amount of pre-distortion depends on the applied components and the signal bandwidth. This makes it challenging to predict the optimum; however, a pure electrical pre-distortion offers already a fair gain in performance. [ABSTRACT FROM AUTHOR]

In this paper, a low-complexity symbol-based equalizer that performs non-linear distortion cancellation is proposed for application at the user terminal in the DVB-S2X satellite forward link. The channel is comprehensively modeled, including the non-linear travelling wave tube amplifier characteristics, the input-multiplexing and output-multiplexing filter responses at the satellite transponder, and the phase noise at the user terminal, according to the very-small aperture terminal reference scenario. Two detectors in the cancellation loop are considered, comparing the packet-error rate (PER) performance of simple maximum likelihood demodulation with hard decision to soft information exchange with low-density parity-check decoder, and showing only marginal improvement with the latter solution. The PER performance is compared against a number of pre-distortion techniques at the transmitter, such as dynamic data pre-distortion, successive data pre-distortion, and static data pre-distortion. The novel receiver demonstrates superior performance even with one iteration of distortion cancellation, while the joint application of successive data pre-distortion and iterative symbol-based equalization shows up to 4.95-dB energy efficiency gain for 32-level amplitude and phase-shift keying (32-APSK). The computational complexity is also evaluated. The improved receiver is particularly suitable for application with higher order modulation, a wide-band carrier, and low roll-off factors. [ABSTRACT FROM PUBLISHER]

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]

We propose a pre-distortion scheme in transmitter DSP to reduce the peak-to-average power ratio (PAPR) in multi-intermediate-frequency (IF)-over-fiber mobile fronthaul (MFH). In optical spectral efficient MFH, multiple modulated sub-bands are transmitted with different IFs serving multi-in multi-out and carrier aggregation in 5G. By applying phase pre-distortion on sub-bands in the transmitter DSP, we reduce the PAPR by more than 2.2 dB with 1% complementary cumulative distribution function value in MFH for 5G mobile networks and significantly increase the transmitted signal power and quality without modifying the system linearity and resolution. The proposed scheme generates small latency. It is DSP efficient and compatible with current mobile devices, without additional noise. With 32 sub-bands served, we demonstrated a 2-dB sensitivity improvement experimentally by applying the proposed scheme. [ABSTRACT FROM PUBLISHER]

A nonlinear pre-distorter (NLPD) at the transmitter, and a maximum-a-posteriori probability (MAP) detector, time-domain Volterra nonlinear equalizer (VNLE), or sparse-VNLE at the receiver are compared for compensation of the pattern-dependent distortion that can occur in high baud rate transmitters and receivers. Experimental results are presented for a 1.206-Tb/s dual-polarization 16-ary quadrature-amplitude-modulation (16-QAM) superchannel signal with three subcarriers. The NLPD with iterative calculation of the pre-distortion provides the best performance in back-to-back systems and transmission systems followed by the MAP detector, VNLE, and sparse-VNLE. At the FEC threshold of 1.9\times 10^-2 , the NLPD provides an increase in the transmission distance of 300 km compared with the sparse-VNLE, VNLE, and MAP detector. For transmission over 1500 km of SMF, the VNLE and MAP detector exhibit additional optical signal-to-noise ratio margins of 0.16 and 0.47 dB relative to the sparse-VNLE. Compared with the VNLE, the sparse-VNLE exhibits a 55% reduction in number of kernel coefficients. [ABSTRACT FROM PUBLISHER]

Data-dependent channel cross-modulation (XM) in multiband radio-over-fiber (RoF) systems have been investigated and illustrated for the first time. Nonlinear XM behaviors induced by a Mach-Zehnder modulator (MZM), including the intra-band XM between in-phase (I) and quadrature (Q) components of vector signals, as well as the inter-band XM between multiple bands of scalar/vector signals, have been studied by a closed-form theoretical analysis, and validated by experimental measurements. Consistent results have been obtained by both theoretical and experimental investigations. It was demonstrated that scalar signals only suffer from inter-band XM; whereas vector signals suffer from both intra- and inter-band XMs. Intra-band XM induces constellation compression distortion to vector signals, while inter-band XM induces eye-diagram degradation to scalar signals, and constellation scaling distortion to vector signals. To mitigate the signal distortions induced by data-dependent XM, arcsine pre-distortion technique was implemented to compensate the nonlinear response of MZM. Effective cancellations of both intra- and inter-band XM were achieved. [ABSTRACT FROM PUBLISHER]

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]

This letter discusses the implementation of microwave backscatter links in CMOS technology which are similar to existing systems at mid-UHF for RFID, but intended for use at the 5.8 GHz ISM band for supporting future low-power WLAN applications. In order for backscatter links to operate in highly channelized environments we introduce a pulse-shaping technique to reduce out-of-band emissions as well as a symbol pre-distortion technique to improve the constellation spacing. Both techniques are introduced into a 65 nm prototype backscatter modulator chip and are shown to operate with QPSK modulation at 54 Mb/s (typical of WLAN standards). The backscatter modulator chip was shown to consume 1.61 mW of power. [ABSTRACT FROM PUBLISHER]

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]

It is well known that HPAs (High Power Amplifiers) are inherently nonlinear devices and many researches have focused on the predistortion for memoryless HPAs. However, memory effects of HPAs can no longer be ignored when communication systems have wider bandwidth. Memoryless predistortion techniques proposed previously seldom have satisfactory effectiveness for typical wideband applications such as OFDM (Orthogonal Frequency Division Multiplexing) systems. In this paper, an improved adaptive predistortion method called 2D LUT (2-dimension look-up table) with different accuracy levels is presented to linearize HPAs with memory effects. Simulation and experimental results show that 2D LUT implements excellent performance in mitigating the signal deterioration caused by memory effects, both rectifies the signal constellation distortion and suppresses the spectrum emission. Large scale matrix computation is also avoidable in these adaptive algorithms, which makes them feasible when a real-time system is necessary. [ABSTRACT FROM AUTHOR]

The nonlinearity inherent in the traveling wave tube (TWT) amplifier distorts amplified signals and results in reduced efficiency and bandwidth, limiting its use in communication and electronic countermeasure applications. Signal predistortion is an effective technique for suppressing nonlinear distortion in TWTs that provides high suppression and requires simple circuits for implementation. While conventional predistortion linearizers are based on third-order intermodulation (MM) injection, this paper proposes using second-order (second-harmonic) signal injection in predistortion circuits. A detailed experimental investigation and comparison of second-order versus third-order signal predistortion is presented. It is observed that both schemes result in suppression of up to 30 dB (55 dBc) for the 31M distortion products. However, experimental results indicate that second-harmonic signal injection performs better than 31M in suppressing higher order products. The paper also investigates spatial evolution of the wave spectrum along the TWT axis with and without injection, and sensitivity of the suppression to injected signals amplitude, phase and the fundamental frequency. [ABSTRACT FROM AUTHOR]

For the power amplifier (PA) used in code-division multiple-access cellular phones, the supply voltage is switched from around 1.5 to 3.5 V at the boundary transmission power of several decibels higher than 10 dBm using a dc-dc converter to improve operation efficiency. Recently, however, this boundary transmission power is being raised. We applied the second harmonic injection to reduce distortion and maximize the boundary transmission power under low supply voltage. This paper presents the design concept of the PA's load impedance and bias network with second harmonic injection using Volterra-series analysis. We also present a design of the final stage of the PA under low supply voltage and show that the final stage has a drain efficiency of 53% at an output power of 21 dBm. [ABSTRACT FROM AUTHOR]

A built-in pre-distortion linearizer using cold-mode MOSFET with forward body bias is presented for 60 GHz CMOS PA linearization on 90 nm CMOS LP process. The power amplifier (PA) achieves a P sat of 10.72 dBm and OP 1~dB of 7.3 dBm from 1.2 V supply. After linearization, the OP1~dB has been doubled from 7.3 to 10.2 dBm and the operating PAE at OP1~dB consequently improves from 5.4% to 10.8%. The optimum improvement of the IMD3 is 25 dB. [ABSTRACT FROM PUBLISHER]