Reverse Intermodulation in Multi-Tone Array Transmitters

Atanasov, Anton N.; Alink, Mark S. Oude; Vliet, F.E. van

doi:10.1109/bcicts48439.2020.9392972

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…In this work we have further explored the relationship between IMD and RIMD and applied the RIMD estimator proposed in [6] to identify which stage enters compression first in a two-stage PA device using only linear measurement equipment. To validate our assumptions we measured seven two-stage DUTs consisting of combinations E-PHEMPT and HBT-based single-stage PAs.…”

Section: Discussionmentioning

confidence: 99%

“…In our previous work [6] we examined the reverse intermodulation products generated when a PA is transmitting power at one frequency while reverse power, at a close frequency offset, is injected into its output. We showed how they relate to regular IMD products generated using the same power levels.…”

Section: Stage Compression Identification Using Rimd a Rimd Estimator...mentioning

confidence: 99%

“…In this paper we present a simple method for identifying the compressing stage in two-stage amplifiers based on an empirical relation used to estimate reverse intermodulation distortion (RIMD) from intermodulation distortion (IMD) measurements [6]. The proposed method is similar in nature and complexity to measuring hot S-parameters [7] and offers good insights into the behaviour of a two-stage PA while being simple and easy to implement without requiring expensive nonlinear VNAs.…”

Section: Introductionmentioning

confidence: 99%

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A Simple and Efficient Procedure for Identifying the Compressing Stage in Two-Stage Amplifiers

Atanasov

Ahmad

Alink

et al. 2021

2021 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS)

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We propose a fast and simple method to accurately determine the compressing stage in a two-stage amplifier system based on reverse intermodulation and hot S-parameter measurements. The method uses no specialized hardware and needs little reconfiguration, simplifying the measurements. We demonstrate its validity over a broad range of amplifiers designed in various semiconductor technologies. This method is a very useful tool in understanding or debugging amplifier designs.

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Section: Discussionmentioning

confidence: 99%

Section: Stage Compression Identification Using Rimd a Rimd Estimator...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Simple and Efficient Procedure for Identifying the Compressing Stage in Two-Stage Amplifiers

Atanasov

Ahmad

Alink

et al. 2021

2021 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS)

Self Cite

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“…As long as the crosstalk is low enough to not result in bitflips, the digital signals are unaffected. Coupling between the analog RF outputs can still be present and can result in reverse intermodulation distortion (RIMD) [32]. In [33], it is however shown that class D architectures, such as the SCPA driver cells, show little RIMD.…”

Section: Nonlinear Couplingmentioning

confidence: 99%

A Predistortion-Less Digital MIMO Transmitter With DTC-Based Quadrature Imbalance Compensation

Zanen

Klumperink

Nauta

2023

IEEE J. Solid-State Circuits

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A four-element multi-input multi-output (MIMO) switched capacitor power amplifier (SCPA) in 22-nm fully depleted silicon-on-insulator (FD-SOI) is presented as a softwaredefined radio. To omit the digital predistortion (DPD) and digital quadrature correction power consumption of this wide modulation bandwidth MIMO transmitter, constant-conductance SCPA drivers and a wideband low-impedance power supply are used for linearization. Digital-to-time converter (DTC)-based clock calibration is used for quadrature imbalance correction, improving image rejection to >53 dB. This allows for up to 80-MHz DPD-less single carrier 1024-quadrature amplitude modulation (QAM) transmission, with an error vector magnitude (EVM) <−39.4 dB. RF bandwidths up to 160 MHz are demonstrated for multicarrier 1024 QAM signals, supporting data rates up to 1.18 GBps. A second-order Chebyshev bandpass filter using bondwires as inductors is used as a matching network, supporting carrier frequencies from 1.64 to 3.28 GHz, while omitting the required chip area for integrated inductors. MIMO experiments demonstrate the beamforming capabilities for single and multibeam communication.Index Terms-CMOS integrated circuits, digital beamforming, digital-to-time converter (DTC), radio frequency digital-to-analog converter (RF-DAC), switched capacitor power amplifier (SCPA).

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“…As long as the crosstalk is low enough to not result in bit-flips, the digital signals are unaffected. Coupling between the analog RF outputs can still be present and can result in reverse intermodulation distortion (RIMD) [32].…”

Section: Nonlinear Couplingmentioning

confidence: 99%

Linear Predistortion-less MIMO Transmitters

Zanen

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In order to support ever increasing data rates and simultaneous numbers of users, high-order modulation schemes such as 1024-QAM and multipleinput multiple-output (MIMO) techniques are applied. Power amplifier (PA) power efficiency in MIMO systems benefits from beamforming array gain, but these MIMO systems require complex digital predistortion (DPD). It is shown that for some MIMO DPD algorithms and wide bandwidths, the overall DPD power consumption can exceed the overall PA power consumption already for transmitters (TXs) for scenarios with more than two antennas. In these scenarios, it can be beneficial for system power efficiency to employ more linear transmitter which do not need DPD, even when this comes at the cost of reduced PA power efficiency.Switched capacitor power amplifiers (SCPAs) are a class of digital transmitters which have shown promising results for high linearity with good drain efficiency (DE). Power efficiency of both the polar and two forms of quadrature implementations are investigated analytically, and in simulations. It is shown that for a given array capacitance and supply voltage, the polar architecture is the most power efficient. Compared to polar modulation, the switched capacitor (SC) loss for 64QAM is fundamentally 18% higher for quadrature modulation with a clock duty cycle of 50% (Q50) and 46% higher for quadrature modulation with a clock duty cycle of 25% (Q25) SCPAs, whereas the generated output powers are fundamentally 6 and 3dB lower, respectively. SCPA linearity is limited by AM-PM distortion, caused by a difference in output conductance in switching and non-switching driver cells. In a first chip, a driver cell implementation as an inverter with drain resistors is proposed which has equal output conductance in both cases, aiming to eliminate AM-PM distortion. This removes the need for DPD, along with the corresponding power consumption. An SCPA with these driver cells is implemented in a 22nm fully depleted silicon-on-insulator (FD-SOI) CMOS process, and demonstrates excellent DPD-less linearity with an adjacent channel leakage ratio (ACLR) of -50 dB and an error vector magnitude (EVM) of -45.5 dB for 5 MHz 1024 QAM signals at a DE of 8.8%. A matching network exploiting bondwires as high-Q inductors removes on-chip inductors and significantly reduces chip area.

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Reverse Intermodulation in Multi-Tone Array Transmitters

Cited by 7 publications

References 11 publications

A Simple and Efficient Procedure for Identifying the Compressing Stage in Two-Stage Amplifiers

A Simple and Efficient Procedure for Identifying the Compressing Stage in Two-Stage Amplifiers

A Predistortion-Less Digital MIMO Transmitter With DTC-Based Quadrature Imbalance Compensation

Linear Predistortion-less MIMO Transmitters

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