# A Full-Duplex 60 GHz Transceiver with Digital Self-Interference Cancellation
## 1 Introduction  
The increasing demand for high-speed communication has urged researchers to develop new communication systems. Currently, wireless data transmission with a data rate that is higher than one gigabit per second (Gbps) is essential due to the proliferation of internet-enabled devices. The spectrum at 60 GHz, reserved internationally for the industrial, scientific, and medical (ISM) bands with an available 9 GHz unlicensed bandwidth, draws much attention. There have been significant research efforts toward the 60 GHz applications related to high-data-rate wireless communications. The high-performance, high-data-rate 60 GHz transceivers are reported in [1; 2; 3; 4]. The designs [1; 2] target the next generation of WiFi standard 802.11 ay with a wider bandwidth and higher-order modulation. The work in [1] presents an area-efficient bidirectionaltransceiver that utilizes a bidirectional amplifier to entirely share the mixer and LO between the transmitter and receiver modes. The measured link error vector magnitude (EVM) for a single channel is \(-\)24.3 dB for 16-QAM at 0.12 m. In [2], a single transceiver with 50.1 Gbps with 8.35 GSym/s in 64-QAM and 3.52 GSym/s with a 128-QAM modulation is reported. The reported single-channel communication with 64-QAM in 0.15 m achieves an EVM of \(-\)28.2 dB. In [3], a low-power, small-size on-off keying (OOK) transceiver is reported with 12.5 Gbps and an energy efficiency of 2.65 pJ/bit. All the reported works in [1; 2; 3] suffer from shorter communication distances limited by the noise floor bandwidth, and they all rely on half-duplex (HD) operation only. The work in [4] presents 2 \(\times\) 64- and 2 \(\times\) 256-element dual-polarization transceiver arrays with maximum equivalent isotropic radiated power (EIRP) values of 38 dBm and 44 dBm, respectively, which provide good signal coverage but consume a large chip area and power consumption. The FD operation is another way to deliver a high data rate by doubling the system's achievable spectrum efficiency [5; 6]. Moreover, the ultra-low latency demand for the upcoming wireless communication system [7] is another benefit for the FD system. With optical communication-like propagation characteristics and a narrow beamwidth, the FD system is a good candidate for a 60 GHz transceiver to work in FD mode. However, the FD system suffers from an enormous RF signal power difference between the power imposed by its transmission and that received from the remote transmitter. Self-interference (SI) suppression or cancellation is critical for an FD system. The work in [8] presents a 60 GHz transceiver with a polarization-based antenna with RF cancellation. It achieves an SI suppression of 70 dB from the transmitter to its receiver. The work in [9] involves SI cancellation for an FD transceiver in a single-antenna system. It achieves 40 dB SI cancellation by using an RF circulator to separate the transmitter and receiver and a reconfigurable impedance mismatched circuit to modify the frequency response of the SI channel. The work in [10] demonstrates an E-band backhaul solution achieving 8 Gbps under the frequency division duplex (FDD) mode. The isolation between the transmitter and receiver is greater than 50 dB. However, the active RF frontend cancellation-based FD systems involve a complex circuit design and work for a specified bandwidth only. This paper proposes a low-power 60 GHz transceiver prototype that is fully compatible with the IEEE 802.11 ad wireless standard. Other than the traditional IEEE 802.11 WiFi standards, which work in HD mode, this work supports both FDD and FD operations. Additionally, the system supports hybrid schemes with reconfigurable switching between the HD, FDD, and FD operation modes. The proposed system's SI requirements are relaxed compared to the works in [8; 11] due to a low transmission power for a comparable communication distance. The organization of this paper is as follows: Section 2 describes the design challenges of the proposed transceiver through the link budget estimation.