A 26-GHz transmitter front-end using double quadrature architecture

RESEARCH ARTICLE A 26-GHz transmitter front-end using double quadrature architecture Hyo-Sung Lee1, Mingyo Park2, Byung-Wook Min ID1* 1 School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea, 2 School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America * a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Lee H-S, Park M, Min B-W (2019) A 26GHz transmitter front-end using double quadrature architecture. PLoS ONE 14(5): e0216474. https:// doi.org/10.1371/journal.pone.0216474 Editor: Esteban Tlelo-Cuautle, Instituto Nacional de Astrofisica Optica y Electronica, MEXICO Received: October 5, 2018 Accepted: April 23, 2019 Abstract A 26-GHz transmitter front-end is designed using 65 nm CMOS technology. The double frequency conversion transmitter consists of an intermediate frequency(IF) mixer, an millimeter-wave(mm-wave) mixer, and a pre-power amplifier. A double quadrature architecture is employed to accomplish image rejection without using an image rejection filter for the first time in the mm-wave frequency band. The IF mixer cores are designed as harmonic rejection mixers to avoid using IF filters. The measured conversion gain is 26.85±0.65 dB, with LO2 (IF LO) at 1–1.5 GHz and 26.9±0.6 dB with LO1 (mm-wave LO) at 27–29 GHz. The measured output return loss is less than -10 dB at 25.7–27.2 GHz. The output 1-dB compression point and the saturation output power measured at 26 GHz are 10 dBm and 14.1 dBm, respectively. The output-referred third-order intercept point (OIP3) measured at 26 GHz is 15.76 dBm. The third-order distortion, suppressed by the harmonic rejection mixer, is -60.5 dBc at an output power of 10 dBm. The error vector magnitude measured for OFDM 16-QAM with a 110-MHz signal bandwidth is -17.7 dB at an average output power of 3.5 dBm. The total power consumption of the proposed 26-GHz transmitter front-end is 267 mW, and it occupies a chip area of 2.31 mm2. Published: May 23, 2019 Copyright: © 2019 Lee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the manuscript. Funding: This work was supported by YSSRC and Space Core Technology Program through the National Research Foundation of Korea funded by the Ministry of Science and ICT (NRF2017M1A3A3A02016255). The CAD tools were supported by IDEC. Competing interests: The authors have declared that no competing interests exist. Introduction With the explosive increase of wireless data capacity, the demand for fifth generation (5G) wireless communication systems has been increasing in recent years [1, 2]. One of the key goals of 5G communications is to procure a wide bandwidth, because they require high data rates. However, it is difficult to secure a wide bandwidth at the existing fourth generation (4G) communication frequencies (below 6 GHz), and future standard 5G communication frequencies are expected to be millimeter wave (mm-wave), in order to procure a wide bandwidth [3– 5]. In particular, the 26 GHz spectrum is a promising candidate for 5G wireless communications in Europe and China. Millimeter waves, including those in the 26-GHz spectrum, inherently suffer from significant propagation loss and less diffraction compared with 4G communication frequencies, which are below 6 GHz. Fig 1 presents a block diagram of a mm-wave switched beam system PLOS ONE | https://doi.org/10.1371/journal.pone.0216474 May 23, 2019 1 / 21 A 26-GHz transmitter front-end using double quadrature architecture Fig 1. Block diagram of a switched beam selection system for 5G communication system for UE. https://doi.org/10.1371/journal.pone.0216474.g001 for 5G communications in UE. Eight high-gain antennas with fixed beams are placed on a circle and can cover a 360˚ azimuth plane [6]. This system does not require phase shifters because beam selection is performed without beam scanning. The UE can select the optimum beam using antenna selection switches. Antenna selection switches and a T/R switch can be integrated as a double-pole eight-throw (DP8T) switch. A double frequency conversion structure was adopted because it has lower local oscillator (LO) feedthrough and LO pulling than the direct-conversion structure. This allows for channel tuning at intermediate frequency (IF). A power amplifier (PA) with power combining techniques was excluded from this design because it would require very high heat dissipation and take up a lot of die area [7, 8]. Instead, a pre-power amplifier (PPA) with a medium output power was implemented to meet the linearity requirement of the system. In this work, a 26-GHz superheterodyne transmitter (TX) front-end for UE was designed using a 65-nm CMOS process. A double quadrature architecture was adopted to reject the image signal without using an image rejection (IR) filter. This enables the integration of a PPA. The IF mixer cores were designed as harmonic rejection mixers (HRMs) to avoid using IF filters for the first time in mm-wave transmitters, and achieve a high integration in the proposed transmitter. In Section II, typical transmitter architectures are discussed and the need for the double quadrature architecture with HRMs is explained. Section III describes the circuit design for the 26-GHz transmitter front-end in detail, followed by our simulated and measured results, presented in Section IV. Transmitter architecture A transmitter based on an I/Q modulator can be classified either as a direct-conversion (homodyne) transmitter or an indirect-conversion (superheterodyne) transmitter. Directconversion transmitters perform frequency up-conversion only once, and therefore have a simpler structure than indirect-conversion transmitters and take up a smaller die area. However, direct-conversion transmitters have some disadvantages which stand out in mm-wave communication systems for 5G. First, LO pulling due to the high output power of the PA occurs because the transmit signal frequency and the LO frequency are the same. This distorts PLOS ONE | https://doi.org/10.1371/journal.pone.0216474 May 23, 2019 2 / 21 A 26-GHz transmitter front-end using double quadrature architecture Fig 2. Block diagram of general double-conversion transmitter. https://doi.org/10.1371/journal.pone.0216474.g002 the oscillation spectrum and degrades the phase noise performance of the system [9]. Secondly, because the desired I/Q modulator has to be designed for mm-waves, carrier leakage due to parasitic elements is relatively large. In contrast, indirect-conversion transmitters, which generally perform a two-step (or more) frequency translation, can be used to alleviate the problems of the direct-conversion transmitter. However, multip (...truncated)