# A Full-Duplex 60 GHz Transceiver with Digital Self-Interference Cancellation
## 2 System Requirement
### Link Budget Model  
The proposed transceiver is targeted for the IEEE 802.11 ad wireless standard up to a communication distance of 3 m. It can support the MCS12 scheme under traditional WiFi operation. The highest raw data rate is 7.04 Gbps under 1.76 GSym/s of 16-QAM with the EVM at \(-\)21 dB. A wideband signal results in an increased in-band noise floor and reduces the SNR. The noise floor can be estimated by using the thermal noise for the given channel's bandwidth together with the additional receiver's noise figure and some implementation losses. Considering a 2.16 GHz channel bandwidth, an additional 5 dB budget for the receiver chain's noise figure, and 5 dB implementation losses, the noise floor of the receiver system will be \(-\)70.6 dBm theoretically.  
Table 1 lists the EVM requirements for some of the key modulation schemes defined in the WiFi standard [12], with the receiver sensitivity level for the system based on the estimated noise floor. As listed in the table, the received signal power at the LNA input must be higher than \(-\)49.6 dBm because of the 21 dB minimal EVM requirement for the targeted modulation scheme at MCS12. To further increase the systems' data rate, either a higher-order modulation scheme or a lower error code rate is required, as can be seen for MCS12.1 to MCS12.6, but with an increased SNR requirement.  
The reference-free space loss for the 60 GHz signal is around 68 dB at a 1 m distance [13; 14]. In this estimation, the additional attenuation items can be ignored because the multipath fading effect is insignificant due to the short communication distance, narrow beamwidth, and good alignment of the antennas. A pair of narrow-beam directional antennas are designed and integrated on the RF-printed circuit board (PCB) to simplify the system's integration and reduce the prototype cost. The integrated antenna provides a 12 dBi antenna gain for both the transmitter and receiver with 17\({}^{\circ}\) half-power beam coverages. The propagation loss for the system reduces to 53.6 dB with the help of such directional antennas. As mentioned in Table 1, the EVM requirement for MCS-12 is \(-\)21 dB and the received power must be larger than \(-\)49.6 dBm. With a 53.6 dB propagation loss,  
\begin{table}
\begin{tabular}{c c c c c} \hline
**MCS** & **Modulation** & **Code Rate** & **EVM Requirements** & **Receiver Sensitivity** \\
**Index** & **Type** & **(dB) 1** & **(dB) 2** \\ \hline
5 & \(\pi\)/2 BPSK & 13/16 & \(-\)12 & \(-\)58.6 \\
6 & \(\pi\)/2 QPSK & 1/2 & \(-\)11 & \(-\)59.6 \\
7 & \(\pi\)/2 QPSK & 5/8 & \(-\)12 & \(-\)58.6 \\
8 & \(\pi\)/2 QPSK & 3/4 & \(-\)13 & \(-\)57.6 \\
9 & \(\pi\)/2 QPSK & 13/16 & \(-\)15 & \(-\)55.6 \\
9.1 & \(\pi\)/2 QPSK & 7/8 & \(-\)16 & \(-\)54.6 \\
10 & 16-QAM & 1/2 & \(-\)19 & \(-\)51.6 \\
11 & 16-QAM & 5/8 & \(-\)20 & \(-\)50.6 \\
12 & 16-QAM & 3/4 & \(-\)21 & \(-\)49.6 \\
12.1 & 16-QAM & 13/16 & \(-\)22 & \(-\)48.6 \\
12.2 & 16-QAM & 7/8 & \(-\)23 & \(-\)47.6 \\
12.3 & 64-QAM & 5/8 & \(-\)26 & \(-\)44.6 \\
12.4 & 64-QAM & 3/4 & \(-\)27 & \(-\)43.6 \\
12.5 & 64-QAM & 13/16 & \(-\)29 & \(-\)41.6 \\
12.6 & 64-QAM & 7/8 & \(-\)31 & \(-\)39.6 \\ \hline \end{tabular} \({}^{1}\) EVM requirements from IEEE Standard 802.11-2016 [12]. 2 Estimated based on a 2.16 GHz channel bandwidth, a 5 dB receiver chain noise figure, and 5 dB implementation losses.  
\end{table}
Table 1: EVM and sensitivity requirements.  
the transmitter's output power should be larger than +4 dBm to satisfy the minimum received power requirements.  
To support a higher modulation scheme with variable amplitude, such as 16-QAM and 64-QAM, a peak-to-average power ratio (PAPR) budget is needed to ensure the linearity of the modulated signal. This can be realized by either increasing the output power of the transmitter or reducing the communication distance to support those high-order modulation schemes.