A Single-Pin Antenna Interface RF Front End Using a Single-MOS DCO-PA and a Push–Pull LNA

Kai Xu,Jun Yin,Robert Bogdan Staszewski,Rui P Martins,Pui-In Mak

doi:10.1109/jssc.2020.2991520

Kai Xu, Jun Yin + Show 3 more

Open Access

https://doi.org/10.1109/jssc.2020.2991520

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Abstract

We propose a simple power-efficient sub-1-V fully integrated RF front end (RFE) for 2.4-GHz transceivers. It introduces the following innovations. First, a function-reuse single-MOS digitally controlled oscillator power amplifier (DCO-PA) with full supply utilization improves antenna-to-DCO isolation for better resilience to jammers. Second, a noninverting transmitter (TX) matching transformer with a zero-shifting capacitor suppresses the second-harmonic emission of the DCO-PA and allows a single-pin antenna interface for both TX and receiver (RX) modes eliminating the transmit/receive (T/R) switches in the signal path. Third, a push-pull low-noise amplifier (LNA) reuses the TX matching transformer for passive gain boosting that reduces power consumption. Fabricated in 65-nm CMOS, the RFE occupies merely 0.17 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Through the functional merge of the oscillator and PA, it can transmit 0 dBm at RF, featuring 10.2% power efficiency when delivering the RF power as low as -10 dBm at a 0.3-V supply. Under a 0.5-V supply, the LNA shows 11-dB gain and 6.8-dB noise figure (NF) while consuming 174 μW.

Highlights

U LTRA-LOW-POWER (ULP) radios play a crucial role in the expansion of Internet-of-Things (IoT) connectivity where wireless sensors gather and exchange a massive amount of data
To avoid the mutual coupling resulting from the forced coexistence of oscillation tank and impedance matching network (MN) in the shared six-port transformer of Fig. 3(a), a single-MOS digitally controlled oscillator power amplifier (DCO-power amplifier (PA)) based on source-to-gate (S-to-G) transformer feedback oscillation is proposed in this article
A relatively high efficiency of 10.2% is retained at 10-dB large power back-off by scaling the supply in the TX mode to 0.3 V, which is confirmed by Fig. 14(b)

Summary

INTRODUCTION

U LTRA-LOW-POWER (ULP) radios play a crucial role in the expansion of Internet-of-Things (IoT) connectivity where wireless sensors gather and exchange a massive amount of data. To avoid the mutual coupling resulting from the forced coexistence of oscillation tank and impedance MN in the shared six-port (i.e., three-winding) transformer of Fig. 3(a), a single-MOS DCO-PA based on source-to-gate (S-to-G) transformer feedback oscillation is proposed in this article. This class-F DCO-PA is extremely vulnerable to jammers appearing at the antenna. All the abovementioned techniques are at the expense of introducing additional tradeoffs between system complexity, reliability, and efficiency

S-to-G Transformer-Feedback DCO-PA

HD2 Suppression Through Zero-Shifting Capacitor Cz

SINGLE-PIN ANTENNA INTERFACE

EXPERIMENTAL RESULTS

CONCLUSION