TY - GEN
T1 - A >1W 2.2GHz switched-capacitor digital power amplifier with wideband mixed-domain multi-tap FIR filtering of OOB noise floor
AU - Bhat, Ritesh
AU - Zhou, Jin
AU - Krishnaswamy, Harish
N1 - Publisher Copyright:
© 2017 IEEE.
PY - 2017/3/2
Y1 - 2017/3/2
N2 - Digital power amplifiers and transmitters have drawn significant interest in the recent past due to their reconfigurability, compatibility with CMOS technology scaling and DSP, and potential for automated design synthesis [1-5]. While significant progress has been made in achieving moderate output power levels in CMOS, wideband modulation, and high efficiency under back-off, out-of-band emissions remain an unsolved problem. The elimination of the analog reconstruction filter that follows the DAC in a conventional analog transmitter implies that broadband DAC quantization noise appears at the output of the transmitter unfiltered. Quantization noise can be suppressed by increasing resolution and/or sampling rate, but to meet the challenging -150 to -160dBc/Hz out-of-band (OOB and specifically RX-band) noise requirement of FDD with conventional duplexers, nearly 12b at 0.5GS/s is required. Such a high effective number of bits (ENOB) is extremely challenging in digital PAs given their strong output nonlinearity. Consequently, while low-power modulators are able to approach -150dBc/Hz RX-band noise floor and below [6], state-of-the-art digital transmitters achieve -130 to -135dBc/Hz RX-band noise, nearly 20dB or 100× away [2-4]. Embedding mixed-domain FIR filtering into digital transmitters to create notches in the RX band has been proposed [4,7], but, while successful in low-power modulators [7], nonlinearity significantly limits notch depth to <10dB in digital PAs [4]. Further, notch bandwidth (BW) is far less than 20MHz, the typical LTE BW, in the simple two-tap FIR structures that have been explored [4].
AB - Digital power amplifiers and transmitters have drawn significant interest in the recent past due to their reconfigurability, compatibility with CMOS technology scaling and DSP, and potential for automated design synthesis [1-5]. While significant progress has been made in achieving moderate output power levels in CMOS, wideband modulation, and high efficiency under back-off, out-of-band emissions remain an unsolved problem. The elimination of the analog reconstruction filter that follows the DAC in a conventional analog transmitter implies that broadband DAC quantization noise appears at the output of the transmitter unfiltered. Quantization noise can be suppressed by increasing resolution and/or sampling rate, but to meet the challenging -150 to -160dBc/Hz out-of-band (OOB and specifically RX-band) noise requirement of FDD with conventional duplexers, nearly 12b at 0.5GS/s is required. Such a high effective number of bits (ENOB) is extremely challenging in digital PAs given their strong output nonlinearity. Consequently, while low-power modulators are able to approach -150dBc/Hz RX-band noise floor and below [6], state-of-the-art digital transmitters achieve -130 to -135dBc/Hz RX-band noise, nearly 20dB or 100× away [2-4]. Embedding mixed-domain FIR filtering into digital transmitters to create notches in the RX band has been proposed [4,7], but, while successful in low-power modulators [7], nonlinearity significantly limits notch depth to <10dB in digital PAs [4]. Further, notch bandwidth (BW) is far less than 20MHz, the typical LTE BW, in the simple two-tap FIR structures that have been explored [4].
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U2 - 10.1109/ISSCC.2017.7870347
DO - 10.1109/ISSCC.2017.7870347
M3 - Conference contribution
AN - SCOPUS:85016241098
T3 - Digest of Technical Papers - IEEE International Solid-State Circuits Conference
SP - 234
EP - 235
BT - 2017 IEEE International Solid-State Circuits Conference, ISSCC 2017
A2 - Fujino, Laura C.
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 64th IEEE International Solid-State Circuits Conference, ISSCC 2017
Y2 - 5 February 2017 through 9 February 2017
ER -