26.6 A 5-to-6GHz Current-Mode Subharmonic Switching Digital Power Amplifier for Enhancing Power Back-Off Efficiency

Zhang, Aoyang; Yang, Ce; Ayesh, Mostafa; Chen, Mike Shuo-Wei

doi:10.1109/isscc42613.2021.9365998

Cited by 11 publications

(9 citation statements)

References 11 publications

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“…Thus, the coefficient t is about 6.275 according to (16). The variable m is about 2 according to (24), which means that the load impedances of main and auxillary PAs are 2R opt at state C or G. Then, the number n is calculated to be about 0.5N. Nearly, half of the unit cells are set to be switched ON.…”

Section: B Switched/floated Capacitor Unit Cellmentioning

confidence: 99%

“…The measured DE and SE of the proposed SFCPA with two typical conditions versus output power at 2.4 GHz are shown in Fig. 24 [38]. The proposed DPA adopts the power digital-to-analog converters (DACs) based on zero-order hold (ZOH) interpolations, which introduces spectral images at integer multiples of the sampling frequency [39].…”

Section: Fabrication and Measurementmentioning

confidence: 99%

“…To increase the efficiency of PA at PBOs, various techniques are developed, such as envelop tracking (ET) [1], [2], outphasing [3]- [7], Doherty [8]- [13], load modulation [14], [15], and Class-G [16], [17]. To further improve the PA efficiency at deep PBO, the multi-way combined Doherty PA with switched transformer [18], Class-G Doherty [19]- [21], subharmonic switching (SHS) [22]- [24], and hybrid Doherty with impedance boosting [25] are developed. The multi-way combined PA with switched transformer introduces various efficiency peaks due to the load modulation [18], which suffers from relatively large circuit size and limited passive efficiency.…”

mentioning

confidence: 99%

“…To mitigate the degradation from supply switching, the Class-G voltage-mode Doherty is proposed with extra hardware overhead [20], [21]. The SHS PAs [22]- [24] can enhance the PA efficiency at deep PBO by using subharmonic component of carrier frequency, which sacrifices the circuit size due to multiple power combined ways. The technique of hybrid Doherty and impedance boosting [25] increases the PA efficiency at deep PBO with less power-combining ways and dc power supplies.…”

mentioning

confidence: 99%

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Quadrature Switched/Floated Capacitor Power Amplifier With Reconfigurable Self-Coupling Canceling Transformer for Deep Back-Off Efficiency Enhancement

Yang

Qian

Luo

2021

IEEE J. Solid-State Circuits

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This article presents a quadrature switched/floated capacitor power amplifier (SFCPA) with deep back-off efficiency enhancement. The SFCPA is introduced to decrease the dynamic power consumption at power back-off (PBO), which could improve the system efficiency (SE). The reconfigurable self-coupling canceling transformer (RSCCT) with enhanced tuning range of turn ratio is used to achieve impedance boosting for further improved efficiency at deep PBO. Based on the proposed SFCPA, a watt-level quadrature digital power amplifier (DPA) with IQ cell sharing, hybrid Doherty, and impedance boosting is proposed for deep PBO efficiency enhancement. Implemented in 40-nm CMOS, the proposed DPA with 1.2-/2.4-V supply achieves 30.3-dBm saturated output power ( P out ) with 36.6%/32.9%/29.1%/23.7%/18.6%/13.2% SE for 0-/3-/6-/9-/12-/15-dB PBOs at 2.4 GHz. For 60-MHz 256-QAM modulation signal, it delivers 23.32-dBm average output power ( P avg ) with an error vector magnitude (EVM) of −31.9 dB and an average drain efficiency (DE) of 30.7%. For 40-MHz 1024-QAM signal, it shows 20.44-dBm P avg with an EVM of −35.9 dB and an average DE of 22.6%.

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Section: B Switched/floated Capacitor Unit Cellmentioning

confidence: 99%

Section: Fabrication and Measurementmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Quadrature Switched/Floated Capacitor Power Amplifier With Reconfigurable Self-Coupling Canceling Transformer for Deep Back-Off Efficiency Enhancement

Yang

Qian

Luo

2021

IEEE J. Solid-State Circuits

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“…In addition, RFDACs 1 typically offer improved energy efficiency when compared to analog PAs. At sub-6-GHz frequencies, RFDAC structures have been recently improved with many innovations that focus on increasing the back-off efficiency using switched transformers [12]- [14] or sub-harmonic LO techniques [15], [16]. A key challenge with RFDACs is that they have mostly been limited in operational frequency due to the limited ability for a transistor to switch at higher frequencies.…”

Section: Introductionmentioning

confidence: 99%

A mm-Wave Switched-Capacitor RFDAC

Nguyen

Walling

Zhu

et al. 2022

IEEE J. Solid-State Circuits

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This article proposes an interleaving switchedcapacitor RF digital-to-analog converter (RFDAC) using an edge combiner within the output stage to implicitly triple its effective clock carrier frequency and enable the mm-wave (mmW) operation. Tripling in the output stage allows for increased energy efficiency, which is further improved by employing an edgecombining-based frequency-tripling delay-locked loop (DLL) in the clock generation network. The clock tripling is performed in each slice of the switched-capacitor PA (SCPA), which allows yet another 3× frequency reduction for the global clock distribution. Finally, a new layout structure accounts for transmission-line (TL) effects, due to the large physical size of the passive capacitor array. Implemented in 22-nm FD-SOI, the prototype achieves P out > 21 dBm, drain efficiency >36%, and system efficiency >22% while operating in the Ka-band at 28 GHz. Modulation at 2.4 Gb/s results in 3.3% EVM and 30.8-dBc adjacent channel leakage ratio (ACLR).

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A Compact CMOS Broadband Bidirectional Digital Transceiver Frontend With Capacitor Bank and Transformer Matching Network Reuse

et al. 2022

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This article presents a fully integrated bidirectional class-G digital Doherty switched capacitor transmitter (TX) and N-path Quadrature receiver (RX) in CMOS. Through sharing on-chip capacitor banks, typically occupying a major portion of the digital TX or RX chip area, as well as the RF passive matching networks, the overall size can be radically reduced. Moreover, the overall performance could be further improved by eliminating the need for an integrated T/RX switch and its corresponding loss and area overhead. The class-G operation is used within the Doherty TX to increase the output power and backoff efficiency, while the capacitive stacking technique is used in the RX to increase the voltage gain. A transformer network is used to present the optimum impedance for both the parallel Doherty TX and RX mode of operation, as well as the class-G Doherty active load modulation. As a proof-of-concept, the joint bidirectional class-G digital Doherty switched-capacitor TX and N-path Quadrature RX through capacitor bank sharing is implemented in a 45-nm CMOS SOI process. The TX demonstrates a Pout 1dB bandwidth (BW) of 1.6-3.1 GHz, a fractional BW >63%, and peak output power (Pout) of 22.5dBm at 2.4GHz. The peak drain efficiency (DE) of the TX is 49.5% at 1.8GHz and 41.5%/38.7%/31.6%/18.1% for the peak/2.5/6/12dB power back off (PBO) at 2.4GHz. The DE improvement compared to class-B PA is 1.24×/1.51×/1.72× at 2.5/6/12dB PBO. The TX is measured using 64-QAM/20MHz modulation without the use of AM-PM pre-distortion or pattern based DPD. It achieves an excellent -27.1dB EVM, -31.31dBc ACLR, 14.6dBm average Pout and 25.8% average DE at 1.6GHz. The RX achieves a noise figure (NF) of 7.6dB at 2.2GHz and a conversion gain of 17dB with a 12 MHz bandwidth. In addition, the proposed RX front-end achieves < -60 dBm LO leakage over the operating frequency range INDEX TERMS capacitor stacking, class-G DPA, CMOS, digital front-end, Doherty, linearity, N-path filter, polar modulation, power back off, transformer.

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26.6 A 5-to-6GHz Current-Mode Subharmonic Switching Digital Power Amplifier for Enhancing Power Back-Off Efficiency

Cited by 11 publications

References 11 publications

Quadrature Switched/Floated Capacitor Power Amplifier With Reconfigurable Self-Coupling Canceling Transformer for Deep Back-Off Efficiency Enhancement

Quadrature Switched/Floated Capacitor Power Amplifier With Reconfigurable Self-Coupling Canceling Transformer for Deep Back-Off Efficiency Enhancement

A mm-Wave Switched-Capacitor RFDAC

A Compact CMOS Broadband Bidirectional Digital Transceiver Frontend With Capacitor Bank and Transformer Matching Network Reuse

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