A Low Power Impedance Transparent Receiver with Linearity Enhancement Technique for IoT Applications

Sizheng Chen,Lei Ma,Na Yan,Cheng Kang,Tingting Shi,Hao Min

doi:10.1155/2018/9130910

Abstract

A low power receiver with impedance transparent RF front end is presented. By using the 4-path passive mixer and the active feedback of LNA, the baseband impedance profile is further transferred to receiver input. While a LO-defined input matching is formed by RF front end, the linearity of entire receiver chain is improved. Furthermore, derivative superposition technique is employed to cancel the distortion of the CMOS LNA. A 3rd-order active-RC filter is designed with current-efficient feedforward compensated OTA. And a digital-to-time converter (DTC) assisted fractional-N all-digital phase-locked loop (ADPLL) is codesigned with receiver to meet the IoT requirements. The presented receiver is fabricated in 55 nm CMOS technology with an active area of 2.3 mm2 and power consumption of 20 mW. Measurement results show that the receiver achieves 5.3 dB NF with 78 dB gain from 0.6 to 1 GHz, the RX out-of-band IIP3 is +8 dBm, and in-band IIP3 is −10 dBm, and the ADPLL achieves −94 dBc/Hz in-band PN and −120.5 dBc/Hz at 1 MHz offset.

Highlights

The need for low power and low cost transceivers has been growing with the expansion of portable wireless devices and wireless sensor networks
This paper proposes a low power impedance transparent receiver with linearity enhancement technique
A low power impedance transparent receiver for IoT application is proposed in this paper

Summary

Introduction

The need for low power and low cost transceivers has been growing with the expansion of portable wireless devices and wireless sensor networks. Different techniques are proposed in recent researches to realize the low power and low cost receiver for IoT protocols. Others proposed a noise-cancelling receiver to achieve very low noise figure by employing two paths of downconversion which increases the hardware complexity [6], but extra calibration is needed to provide precise gain and phase matching. An impedance transparent receiver architecture is proposed which only uses one downconversion path. The proposed reconfigurable RF front end employs an active feedback LNA to transfer the baseband filter character to the input of receiver, which can attenuate out-of-band interferers. This paper proposes a low power impedance transparent receiver with linearity enhancement technique. Parameters RF frequency Channel bandwidth Max. receive level Sensitivity Noise figure P-1dB OB-IIP3 In-band IIP3 ∗Range 2 of NB-IoT protocol

System Description

Building Block Designs

Measured Results

Conclusion