## 4 Simulation Results  
The SIC receiver was designed in 40 nm CMOS technology and has a 1.8 V voltage supply. The active canceler draws a maximum current of 3 mA (AMP1 only) or 6 mA (AMPQ only) depending on the self-interference power level and its phase. The LNTA draws a current of 4 mA, while the TIAs draw 1.8 mA each. The total power dissipation is 25 mW. The simulated performance of the canceler alongside the entire receiver chain is reported as follows. Figure 12a shows cancellation of the SI versus frequency when the SI is programmed for optimum cancellation at 2 GHz. 30 dB of cancellation over a bandwidth of 250 MHz is achieved when no delay is introduced between the TX signal and the SI. The 30 dB cancellation bandwidth shrinks to 10 MHz with a delay of 2 ns. Figure 12b also shows the cancellation of the SI as a function of the coupling phase over the entire 360\({}^{\circ}\). The simulated receiver NF is plotted in Figure 13. When the receiver NF is 4 dB, the noise contribution of the canceler is around 16%, the LNA contributes around 42% and the remaining blocks (Mixer and TIAs) 2%, as illustrated in Figure 13c. The system NF with the canceler turned off is shown in Figure 13a. The system NF without canceler has a NF of 3-3.7 dB in the range of 1.7 and 2.4 GHz. When the canceler is turned ON, it goes from 3.9 dB to 4.5 dB as a function of the coupling phase. The pattern of the noise shown in Figure 13b is consistent with the analysis in Section 3. When AMP1 with degenerated resistor, is turned ON more noise is generated, while when only AMPQ is turned ON the noise decreases. Figure 12: Self-interference cancellation (**a**) over RF frequency; (**b**) as a function of canceler phase. Figure 13: RX NF (**a**) vs. input frequency; (**b**) with and without canceler as a function of canceler phase; (**c**) Noise summary of the system. Figure 14 shows the result of a two-tone test, with one from the TX and one from the blocker at 100 MHz offset. The signal spectrum is shown in Figure 14a. Plotted in Figure 14b is the ratio between blocker and IM3 (HD3) as well as the TX leakage attenuation as a function of canceler gain setting for \(-6\) dBm TX leakage at the receiver input. For the canceler without feedback resistors the peak in HD3 does not correspond to where optimum cancellation is achieved. At the point of optimum SI cancellation, the HD3 is dominated by canceler nonlinearities which is a product of the cross-modulation between the TX signal at the canceler input and the blocker at the LNA input. Adding the feedback resistors re-aligns the peak in HD3 with the peak in SI cancellation. Figure 15a shows the receiver IIP3 vs the self-interference frequency for both in-band and OOB signals while the canceler is disabled. The two tones \(\mathrm{f_{RF1}}\) (TX leakage) and \(\mathrm{f_{RF2}}\) (blocker) are swept over a range of frequencies such that the intermodulation term is constantly observed at \(\mathrm{f_{IM3}}(=2\mathrm{f_{RF1}}-\mathrm{f_{RF2}})\) equal to 1 MHz and the LO is at 2 GHz. When the canceler is disabled (dashed line) the receiver IIP3 ranges from 4 dBm in-band to 18 dBm when \(\mathrm{f_{RF1}}\) and \(\mathrm{f_{RF2}}\) are placed 100 MHz and 199 MHz respectively away from the LO. The in-band IIP3 is limited by the TIA. When the canceler is enabled the receiver IIP3 ranges from 36.3 dBm in-band to 34.8 dBm OOB. The effective IIP3 improvement is strictly related to the cancellation. Ideally, for every 1 dB of SI cancellation, the effective IIP3 should improve by 1 dB, i.e., the IM3 should decrease with the square of cancellation. In plots in Figure 15a, the SI cancellation changes with frequency from 32 dB in-band  
Figure 14: Two-tone test: (**a**) spectrum with blocker at 10 MHz offset; (**b**) with SI at the RX input as a function of canceler control bits. Figure 15: Receiver gain and effective IIP3 before and after cancellation: (**a**) vs. two-tone frequency spacing; (**b**) vs. input power for a frequency spacing of 45 MHz. to 28 dB OOB.