# A 60 GHz CMOS I/Q Receiver for High-Speed Wireless Communication System
###### Abstract  
This paper presents a 60 GHz CMOS I/Q receiver for the high-speed wireless communication system. It consists of a low noise amplifier, single-to-differential (S2D) amplifier, passive mixer, buffer amplifier with passive I/Q generator, and wideband baseband amplifier (BBA) stage. The measured conversion gain of 51 dB is achieved. The baseband bandwidth of 300 MHz is achieved from 57 GHz to 60 GHz. The 90 deg tandem coupler was implemented for I/Q signal generation, which has a phase error of <7 deg and an amplitude imbalance of <2 dB from 55 to 62 GHz. The Marchand balun is used to convert the I/Q signal to the differential, which has a phase error of <4 deg. A 60 GHz CMOS I/Q receiver is designed and fabricated, using a commercial 40 nm CMOS bulk process. The size of the receiver is 2.02 \(\times\) 1.45 mm\({}^{2}\), including the pads. The circuit is operated from a 0.9 V supply. The power consumption is 172 mW at maximum gain mode.  
60 GHz; 802.11 ad; WiGig; I/Q receiver; millimeter wave +
Footnote †: journal: Applied  
the proposed 60 GHz I/Q receiver is shown in Figure 1. It consists of a low noise amplifier (LNA), single-to-differential (S2D) amplifier, double-balanced passive mixer, LO buffer amplifier, quadrature generator (IQGEN), and baseband amplifier (BBA). The LNA is a single-ended design, with the first two stages being a common source amplifier with source degeneration to achieve an optimal noise figure (NF) so that it can amplify the RF signal around 60 GHz with low noise figure [7; 8; 9; 10; 11]. Since the mixer is double balanced and mixes in phase (I) and quadrature phase (Q) individually, the amplified RF signal from the LNA, which is a single-ended design, is converted to the differential form using an S2D amplifier. In an S2D amplifier, the single-ended RF signal is converted into the differential form using S2D balun. Balun, being a passive device, introduces some attenuation to the RF signal from the LNA, thus we need to compensate for the loss using the amplifier in the S2D stage. The RF signal from an S2D and local oscillator signal (LO signal) is mixed in the passive mixer. Since the mixer is passive, there is conversion loss in the mixing process, thus we need a LO buffer amplifier that ensures the LO signal has enough swing to switch on the passive mixer switches. For image rejection, the receiver is designed for I and Q mixing. The I and Q signals are generated before the LO buffer amplifier stage using the I/Q generator. The I/Q generator consists of a quadrature tandem coupler and balun. The quadrature tandem coupler generates the I and Q signal from the local oscillator input [12; 13; 14]. The I and Q signals are then converted to differential signals using a balun and fed to the LO buffer amplifier. The down-converted intermediate frequency (IF) baseband signal is amplified using BBA. The BBA consists of six stages of the amplifier to increase the signal level suitable for further processing for ADC and demodulation of the signal. The last stage is a buffer circuit to drive the external 50 \(\Omega\) load of the base-band signal. Since all the amplifiers are gain controllable, based on the control bit, the receiver can operate in required gain states [15; 16].