Distortion Cancellation Research Articles

A Dual-Mode CMOS Power Amplifier with an External Power Amplifier Driver Using 40 nm CMOS for Narrowband Internet-of-Things Applications

The narrowband Internet-of-Things (NB-IoT) has been developed to provide low-power, wide-area IoT applications. The efficiency of a power amplifier (PA) in a transmitter is crucial for a longer battery lifetime, satisfying the requirements for output power and linearity. In addition, the design of an internal complementary metal-oxide semiconductor (CMOS) PA is typically required when considering commercial applications to include the operation of an optional external PA. This paper presents a dual-mode CMOS PA with an external PA driver for NB-IoT applications. The proposed PA supports an external PA mode without degrading the performances of output power, linearity, and stability. In the operation of an external PA mode, the PA provides a sufficient gain to drive an external PA. A parallel-combined transistor method is adopted for a dual-mode operation and a third-order intermodulation distortion (IMD3) cancellation. The proposed CMOS PA with an external PA driver was implemented using 40 nm-CMOS technology. The PA achieves a gain of 20.4 dB, a saturated output power of 28.8 dBm, and a power-added efficiency (PAE) of 57.8% in high-power (HP) mode at 920 MHz. With an NB-IoT signal (200 kHz π/4-differential quadrature phase shift keying (DQPSK)), the proposed PA achieves 24.2 dBm output power (Pout) with a 31.0% PAE, while satisfying −45 dBc adjacent channel leakage ratio (ACLR). More than 80% of the current consumption at 12 dBm Pout could be saved compared to that in HP mode when the proposed PA operates in low-power (LP) mode. The implemented dual-mode CMOS PA provides high linear output power with high efficiency, while supporting an external PA mode. The proposed PA is a good candidate for NB-IoT applications.

A Multi-GHz Inverter-Based ASDM With Distortion Cancellation

A Multi-GHz Inverter-Based ASDM With Distortion Cancellation

Enhanced Pre/Post Compensation of Fiber Link Nonlinear Distortion by a Stepwise Parameter Profiled Fiber and Phase Conjugation Module

Compensation of nonlinear distortion in long distance communication links from the power induced Kerr effect is demonstrated at the transmitter or receiver by the combination of optical phase conjugation (OPC) and propagation in a stepwise parameter profiled fiber (SPF). The SPF tailored with an increasing nonlinearity and decreasing dispersion parameter on average with distance as well as Raman gain induces a distortion more closely matching that of the link to improve propagation symmetry for enhancing overall distortion cancellation by OPC. Measurements show for a module inserted at the transmitter or receiver with a 60 km long SPF comprising of three different fibers, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q²</i> -factor is improved by 2.3 and 1.7 dB, respectively, compared to without for transmitting 5 channel WDM dual polarization 12 Gbaud 16-QAM signals in 2×160 km fiber spans that both include dispersion compensation. Similarly, recirculating loop transmission of the same signal over 18×80 km (1440 km) shows improved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q²</i> -factors of 1.9 and 1.3 dB, respectively. This corresponds to extending the transmission reach by 125 and 80%, respectively, for matched performance at equal launch power, highlighting the greater nonlinear distortion tolerance achievable with advanced OPC designs.

Numerical evaluation of bidirectional high-speed data transmission over turbulence tolerable FSO link employing WDM-OAM multiplexing and DP-QPSK modulation techniques

Orbital angular momentum (OAM) mode multiplexing is achieving utmost interest for the enhancement of transmission capacity and spectral efficiency. We have reported a (2 × 8 × 112 Gbps) 1792 Gbps bi-directional FSO link based on WDM-OAM multiplexing and dual-polarization quadrature phase-shift keying (DP-QPSK) modulation technique. An optical frequency comb lines (OFCL) generator, capable to generate 44 comb lines with flatness∼0 dB is employed as a broadband laser source. The efficiency of the system is not only checked for clear weather but also for different turbulence situations (weak, moderate, and strong atmospheric turbulence). According to the best of our knowledge, this is the first one where the effect of atmospheric turbulence on DP-QPSK data carrying OAM modes has been checked for a bidirectional link. The combination of coherent detection with digital signal processing is utilized for compensating wave-form distortion and noise cancellation due to atmospheric turbulence. A very low power penalty of 1.65 dB in clear weather and 4.91 dB in strong atmospheric turbulence at a BER∼10 −9 with open eye and clear constellation diagrams depicts the feasibility of the proposed system.

PMSM Combination Modeling for Multiparameter Estimation Using Bayesian Learning With Inverter Distortion Cancellation and Temperature Compensation

Permanent magnet synchronous machine (PMSM) drives with better efficiency are highly demanded, and accurate flux linkage and inductance models or maps are critical to achieve such drives. However, precise modeling and estimation of these parameters should employ redundant data and are affected by magnetic saturation and inverter distortion. This paper firstly derives a flux linkage combination model from machine model for flux linkage and inductance estimation, in which inverter distortion is cancelled and thus inverter influence is minimized for performance improvement. To consider magnetic saturation, radial basis functions are employed to model the nonlinear flux linkages with a small number of relevance vectors, which can effectively depict the nonlinear variation. Bayesian learning approach is then explored to estimate the sparse coefficients of the flux linkage model in the context of radial basis functions, which can deal with non-Gaussian noise to improve the estimation accuracy and guarantee flux linkage model with better computation efficiency and less memory occupation. Moreover, temperature effect is considered to ensure the model accuracy under temperature rise. The proposed approach is validated with experiments and comparisons on a laboratory PMSM drive.

Load-Modulating Loop Combiner for Linear Power Amplification

This work presents a novel power amplifier (PA) architecture employing a feedforward-like loop structure for the linearization of a load-modulated PA. The load-modulating loop combiner (LMLC) is related to a feedforward amplifier, but with the interaction between the main and auxiliary amplifiers to generate both distortion cancellation and load modulation. A brief overview of the underlying theory is presented, followed by a hardware demonstrator operating at 3.5 GHz with 42-dBm peak output power and 55% peak drain efficiency in CW. When excited by a 100-MHz LTE signal, it maintains a 3-ppt EVM improvement and a 2–5-ppt average drain efficiency improvement compared to its standalone main amplifier.

Autoencoder‐based deep learning for massive multiple‐input multiple‐output uplink under high‐power amplifier non‐linearities

In this paper, the authors study the compensation of high-power amplifier (HPA) non-linear distortion in the multi-user (MU) massive multiple-input multiple-output (MIMO) systems and focus on uplink transmission, where the base station (BS) uses a large antenna array. First, the authors present a non-linear distortion iterative cancellation (NDIC) algorithm-based MMSE and approximate message passing (AMP) at the receiver level, in order to estimate and mitigate jointly a non-linear distortion and the channel noise. Second, the authors propose a novel distortion cancellation technique based on deep learning. At this level, the authors first introduce a multilayer neural network, trained in the Levenberg–Marquardt algorithm by eliminating HPA non-linearities on the ‘Pre distortion’ transmitter and ‘Post distortion’ receiver side. Next, the authors developed a novel end-to-end (E2E) learning approach for the joint transmitter and non-coherent receiver in the Rayleigh fading channel. The basic idea lies in the use of deep neural networks (DNNs), auto encoder (AE) for unknown channels, where DNNs are applied to perform several functions and modules existing in the transmission chain. The simulation results demonstrate the strong potential of the proposed approach E2E in terms of improving the link quality and symbol error rate (SER) compared to other compensation techniques presented in this work.

Load-Modulation-Based IMD3 Cancellation for Millimeter-Wave Class-B CMOS Power Amplifiers Achieving EVM &lt; 1.2%

This letter presents a novel load-modulation-based 3rd-order intermodulation distortion (IMD3) cancellation technique for class-B CMOS power amplifiers (PAs). In a class-B PA, the IMD3 generated by the 3rd-order transconductance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$g_{m3}$ </tex-math></inline-formula> ) and the gain compression have opposite signs, and thus, they can cancel each other at specific bias and loading conditions. The proposed Doherty topology allows adjusting the gain compression by modulating the effective loading, facilitating IMD3 cancellation over the entire load modulation region. The proposed approach is verified using a 28 GHz 40 nm CMOS series-Doherty PA (DPA) topology. The experimental result demonstrates 10/17 dB IMD3 improvement compared to class-B/DPA operation. Without using any digital pre-distortion, the measured EVM of the proposed technique for a 50 MHz 64-QAM OFDM signal with 8.9 dBm average output power is −38.7 dB (1.2%), which is 5.7/11 dB better than a standard class-B/DPA operation.

A 60‐GHz low‐noise amplifier with +7.258‐dBm third‐order input intercept point using current reuse feedforward distortion cancellation for 5G emerging communication

AbstractIn the ever‐growing 5G technology, the millimetre‐wave (mmWave) frequency spectrum is the inevitable mainstream for high‐speed wireless communication. The wide‐ranging spectrum bandwidth of the mmWave frequency attracts interest in radio frequency (RF) front‐end design which will be very much beneficial for security and cellular‐based applications such as intersatellite communication and automotive vehicle‐to‐vehicle communication. The RF front end requires low‐power and low‐noise receiver architecture for effective satellite communication, and it needs high throughput with maximum data transfer for cellular‐based applications. To address these challenges, this paper presents a novel low‐noise amplifier (LNA) operating from 57.12‐ to 66.25‐GHz frequency. The design is implemented using UMC 65‐nm CMOS process technology, and the post‐layout simulations are carried out using the Cadence Spectre RF tool. At 60 GHz, the LNA exhibits a power gain of 15.46 dB, minimum noise figure (NF) of 1.32 dB while consuming 6.59 mW from a 1.2‐V supply. The LNA employs the current reuse feedforward distortion cancelation technique to improve the third‐order input intercept point (IIP3) to +7.258 dBm. The proposed LNA provides a relatively better figure of merit compared to some of the recently proposed mmWave LNA architectures.

Low-Noise, High-Linearity Sine-Wave Generation Using Noise-Shaping Phase-Switching Technique

To develop a lower cost on-chip characterization solution for postsilicon validation, this article proposed a &#x201C;noise-shaping phase-switching&#x201D; technique on a sigma&#x2013;delta modulated digital-to-analog converter (DAC) to realize a low-noise, high-linearity sinusoidal-wave generator. The proposed technique combines the fifth-order cascade of resonators with distributed feedback (CRFB) type delta&#x2013;sigma modulation (DSM) and the two-way time-interleaving phase-switching harmonic distortion (HD) cancellation technique without additional cost. The theoretical analysis is verified with MATLAB and further implemented using a low-cost arbitrary waveform generator (AWG) as the output DAC. Compared with a nonideal 12-b DAC, the proposed technique achieved at least 2-dB enhancement in spurious-free dynamic range (SFDR) (measurement) while maintaining an improvement of at least 18 dB in the medium dynamic range (DR) (simulation) over the entire signal bandwidth.

A 12-b 1-GS/s 61-dB SNDR Pipelined-SAR ADC With Inverter-Based Residual Amplifier and Tunable Harmonic-Injecting Cross-Coupled-Pair for Distortion Cancelation Achieving 6.3 fJ/conv-step

A 1GS/s 12-bit single-channel successive approximation register (SAR) assisted pipeline analog-to-digital converter (ADC) is presented. It consists of three stages (4b-4b-6b) with two one-bit interstage redundancies implemented. A novel Harmonic-injecting Cross-Coupled Pair (HXCP) is proposed in an inverter-based residual amplifier (RA) as a critical part of the presented ADC. By implementing the HXCP, the linearity of the RA is effectively improved and meanwhile the gain of the RA is boosted to about 8. The HXCP is designed to be tunable to enhance its robustness against PVT variation. The prototype single-channel ADC was fabricated in 28-nm CMOS process and achieves &#x003E;60dB SNDR and &#x003E;70dB SFDR up to 320MHz, corresponding to a 6.3fJ/conv. step FoMw and 170.5dB FoMs.

A Uniformed DC Magnetic Generator Using Ferromagnetic Slot Cage by Geomagnetism Distortion Cancellation

A widely uniform and highly ambient robust DC magnetic field generator for precise motion sensors using inertial measurement units (IMUs) is newly proposed in this paper. Chronic problems such as low uniformity of magnetic field and geomagnetic disturbance of conventional Helmholtz, Merritt, Rubens, Lee-Whiting, and Tetra coils can be significantly mitigated by the proposed uniform DC magnetic field generator (UFG). Different from the previous air coils, the proposed UFG adopts a core-cage so that a strong and uniform DC magnetic field distribution can be generated inside the cage and that the UFG may be quite magnetically robust to ambient changes such as geomagnetic field and ferromagnetic objects. A dedicated power supply was developed for providing not only a DC current to generate the required magnetic field but also an exponentially decaying AC current to demagnetize the residual magnetic field in the core-cage. Design procedures for the UFG are fully established, considering the manufacturing cost, performance, and mechanical robustness for commercialization. Detailed designs of the UFG for magnetic field generation, enhancing uniformity, geomagnetic cancellation, and demagnetizing of the UFG are provided. Experimental results verified by a 30 cm × 30 cm × 30 cm prototype UFG showed that the geomagnetic field inside the UFG was significantly attenuated by 22 dB while the DC magnetic field uniformity (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>t</i></sub> < 5.0°) was achieved over 85% of the total volume of 27,000 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

A Wideband Noise and Harmonic Distortion Canceling Low-Noise Amplifier for High-Frequency Ultrasound Transducers.

This paper presents a wideband low-noise amplifier (LNA) front-end with noise and distortion cancellation for high-frequency ultrasound transducers. The LNA employs a resistive shunt-feedback structure with a feedforward noise-canceling technique to accomplish both wideband impedance matching and low noise performance. A complementary CMOS topology was also developed to cancel out the second-order harmonic distortion and enhance the amplifier linearity. A high-frequency ultrasound (HFUS) and photoacoustic (PA) imaging front-end, including the proposed LNA and a variable gain amplifier (VGA), was designed and fabricated in a 180 nm CMOS process. At 80 MHz, the front-end achieves an input-referred noise density of 1.36 nV/sqrt (Hz), an input return loss (S11) of better than −16 dB, a voltage gain of 37 dB, and a total harmonic distortion (THD) of −55 dBc while dissipating a power of 37 mW, leading to a noise efficiency factor (NEF) of 2.66.

A 2.4 GHz sub 1-mW highly linear differential LNA using balun transformer gm-boosting technique

This paper presents a passive gm-boosting differential low noise amplifier (LNA) for low power applications using a single-to-double transformer. This LNA improves noise figure and linearity with no extra power penalty by using the front-end balun together with noise and distortion cancelation. To address the excess power and noise that are introduced by the auxiliary amplifier, both the current reuse and resistive feedback techniques are used. The input balun provides the differential signals from the single ended input signal and boosts the gm of the amplifier. gm-boosting together with the distortion reduction technique improve both the second and third order nonlinearity. The detailed analysis and simulations including Gain, NF, and Linearity in a standard 65nm CMOS technology are given. Simulation results reveal that the LNA achieves over 23.5 dB gain, 2.8 dB NF, IIP3 and IIP2 of +4.3 dBm and +46 dBm, respectively. It consumes 620 µW from a 0.8 V supply voltage while the total effective die area is 0.21mm2.

A Dual-Mode InGaP/GaAs HBT Power Amplifier Using a Low-Loss Parallel Power-Combining Transformer with IMD3 Cancellation Method

A dual mode InGaP/GaAs heterojunction bipolar transistor (HBT) power amplifier (PA) using a parallel power-combining transformer (PCT) is presented herein. A low loss transformer is implemented on a printed circuit board (PCB) to improve the passive efficiency of a PCT. Dual-mode operation is applied to reduce the current consumption at a low power level. In the low-power (LP) mode, one of the individual amplifiers is turned off to reduce the current consumption. Additionally, a third-order intermodulation distortion (IMD3) cancellation method using a PCT combiner is proposed to improve linearity performance. Nonlinear IMD3 components from each amplifier cancel each other out through magnetic coupling in the secondary winding of the PCT. The implemented PA achieves a saturated output power of 33.8 dBm and a peak power-added efficiency (PAE) of 54.5% at 0.91 GHz with a 5-V power supply. An average output power of 25.2 dBm with an adjacent channel leakage ratio (ACLR) of −42 dBc is delivered when the PA is tested with an orthogonal frequency division multiplexing (OFDM) 64-quadrature amplitude modulated (64-QAM) signal with a bandwidth of 10 MHz and peak-to-average power ratio (PAPR) of 7.8 dB. When compared with the high-power (HP) mode operation, the LP mode operation could save 48% of the current consumption at an average output power of 10.4 dBm.

Shock-wave distortion cancellation using numerical recalculated intensity propagation phase holography

Digital holography is a three-dimensional (3D) measurement technique that can be used to quantitatively determine the size and 3D location of the objects inside a field-of-view. However, in systems where refractive index gradients are present, variations in optical phase due to high-speed shock-waves or low-speed thermal gradients can cause distortions that obscure objects. While techniques like phase-conjugate digital in-line holography and iterative phase measurement techniques have been developed in the past for phase removal or phase measurement, they require either nonlinear four-wave-mixing or iterative algorithms to operate. In this paper, we demonstrate a novel recalculated intensity propagation phase holography (RIPPH) method that captures distorted holograms using low-power continuous lasers, refocuses the hologram to the plane of the distortion, and cancels the phase distortion numerically in a single post-processing step. The resulting hologram can be numerically refocused to provide distortion-free 3D information describing objects that absorb or scatter light. In RIPPH, only the approximate z-locations of the phase distortions are needed, making this method significantly faster to compute than phase retrieval methods. Theoretical simulations are first used to describe and assess the distortion removal process. Experiments are then conducted to demonstrate at least 3× lower edge distortion for RIPPH compared to traditional digital in-line holography. We demonstrate, for the first time, how phase distortions from supersonic air jets, particle-laden spherically expanding shock-waves, and convectively-driven thermal gradients are numerically cancelled and show how objects of interest are accurately recovered.

A 0.061-mm² 1–11-GHz Noise-Canceling Low-Noise Amplifier Employing Active Feedforward With Simultaneous Current and Noise Reduction

This article proposes a novel wideband common-gate (CG) common-source (CS) low-noise amplifier (LNA) with active feedforward for simultaneous current and noise reduction. By employing an active feedforward stage in the main path, the current dissipation and the thermal noise are effectively suppressed, while the noise and distortion cancelation properties of CG-CS topology are preserved. Moreover, no extra noise is introduced since the additional g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> -boost amplifier follows the same noise-canceling (NC) principle as the CG amplifier, and its noise can be fully canceled at the output theoretically. Thus, the proposed LNA benefits from the g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> -boosting and NC technique simultaneously to obtain a good tradeoff between gain, noise figure (NF), and power consumption. Fabricated in standard 40-nm CMOS technology, the measured results show the proposed LNA exhibits a peak gain of 17 dB, NF of 3.5-5.5 dB from 1 to 11 GHz and an IIP3 of -2.8 dBm at 6 GHz. It consumes 9 mW from a 1.2-V supply and occupies a very compact die area of 0.061 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Spline-Based Adaptive Cancellation of Even-Order Intermodulation Distortions in LTE-A/5G RF Transceivers

Radio frequency transceivers operating in in-band full-duplex or frequency-division duplex mode experience strong transmitter leakage. Combined with receiver nonlinearities, this causes intermodulation products in the baseband, possibly with higher power than the desired receive signal. In order to restore the receiver signal-to-noise ratio in such scenarios, we propose two novel digital self-interference cancellation approaches based on spline interpolation. Both employ a Wiener structure, thereby matching the baseband model of the intermodulation effect. Unlike most state-of-the-art spline-based adaptive learning schemes, the proposed concept allows for complex-valued in- and out-put signals. The optimization of the model parameters is based on the stochastic gradient descent concept, where the convergence is supported by an appropriate step-size normalization. Additionally, we provide a gain control scheme and enable pipelining in order to facilitate a hardware implementation. An optional input transform improves the performance consistency for correlated sequences. In a realistic interference scenario, the proposed algorithms clearly outperform a state-of-the-art least mean squares variant with comparable complexity, which is specifically tailored to second-order intermodulation distortions. The high flexibility of the spline interpolation allows the spline-based Wiener models to match the performance of the kernel recursive least squares algorithm at less than 0.6% of the arithmetic operations.

A 4–6 GHz Single-Ended to Differential-Ended Low-Noise Amplifier for IEEE 802.11ax Wireless Applications with Inherent Complementary Distortion Cancellation

With the emergence of the internet-of-things (IoT), many devices process data through the IEEE 802.11 wireless networks. To satisfy the increased data processing, the wireless fidelity (Wi-Fi) networks must have sufficient capacity. IEEE 802.11ax is formulated to provide higher data processing capabilities for IoT applications. The IEEE 802.11ax receiver operating at 5[Formula: see text]GHz must be able to withstand interference from nearby IoT applications. Hence, the low-noise amplifier (LNA) employed in such receivers must have a high input-referred third-order intercept point (IIP3). This paper aims to present a wideband LNA operating at 5[Formula: see text]GHz with high IIP3 for modern IoT transceivers using IEEE 802.11ax protocol. The LNA is designed and implemented in UMC 65[Formula: see text]nm CMOS technology using the Cadence virtuoso design tool. The proposed LNA can provide a maximum gain of 17.64[Formula: see text]dB while consuming 8.18[Formula: see text]mW of power from a 1.2[Formula: see text]V supply. It can be noted that the minimum noise figure (NF) achieved is 3.67[Formula: see text]dB and the corresponding IIP3 is 9.44[Formula: see text]dBm at 5[Formula: see text]GHz from the pre-layout simulations.

A 660 MHz–5 GHz 6-Phase/3-Phase Transmitter With Cancellation of Counter-Intermodulation Distortion and Improved Image Rejection

In the transmit signal path of a cellular terminal that supports the Long-Term Evolution (LTE) standard, the third-order counter-intermodulation (CIM3) product can be a significant contributor to spurious emissions in protected bands, primarily in cases where all the transmit power is concentrated in one resource block at the edge of the allocated bandwidth. This problem can be addressed with a harmonic rejection architecture for the up-conversion mixer in the transceiver. Prior work in this area retains the four-phase baseband inputs of a conventional quadrature mixer, utilizes various techniques in the local oscillator (LO) path involving overlapping LO waveforms to suppress harmonics and requires the digitally-controlled oscillator (DCO) to be operated at two or more times the LO frequency. The harmonic rejection architecture presented in this paper has six baseband phases and six non-overlapping LO phases and, for higher-frequency bands, allows the DCO to run at 1.5 times the LO frequency. It also provides an inherently higher uncalibrated image rejection than architectures with quadrature baseband inputs, which is advantageous for any wireless communication standard that supports higher-order quadrature amplitude modulation (QAM) schemes such as 1024-QAM and 4096-QAM.