# On Self-Interference Cancellation and Non-Idealities Suppression in Full-Duplex Radio Transceivers
## 2 Proposed System Model and Techniques
### Power Level of Different Components of SI. Signal After RF/Analog SI Cancellation  
The power of different components of the SI signal at Rx input without any SI cancellation is shown in Figure 9a. \(P_{SI}\) and \(P_{SI,im}\) are much stronger signal components and have much higher powers compared to the desired signal, which has a power of approximately \(-55\) dBm at an Rx sensitivity level of \(-88.9\) dBm. At Tx power of 5 dBm, \(P_{SI}\) is \(-15\) dBm and \(P_{SI,im}\) I s\(\sim\)\(-40\) dBm, hence \(P_{SI}\) is \(\sim\)40 dBm and \(P_{SI,im}\) is \(\sim\)15 dBm stronger than the desired signal, and \(P_{SI}\) is \(\sim\)73.9 dBm and \(P_{SI,im}\) is \(\sim\)48.9 dBm stronger than the Rx sensitivity. However, \(P_{IMD}\) and \(P_{IMD,im}\) are not very strong but are still higher than the sensitivity level of Rx at higher transmit powers, i.e., above 25 dBm. Figure 9b,c shows the results of the proposed SI cancellation technique, i.e., CSI with LS estimator. With this technique, along with 30 dB antenna isolation as shown in Figure 9b, the power of all the SI signal components drops below the desired signal and Rx sensitivity level, except the image component \(P_{SI,im}\).  
Hence, now the only SI component with a power level above the Rx sensitivity is \(P_{SI,im}\). It can be observed in Figure 9c that by using the CSI technique along with 40 dB antenna isolation, \(P_{SI,im}\) power also falls below Rx sensitivity. For antenna isolation of 30 dB with CSI, \(P_{SI,im}\) remains below the desired signal power level for transmit power levels higher than 20 dBm. Similarly, for antenna isolation of 40 dB with CSI, \(P_{SI,im}\) remains below the desired signal power level for transmit power levels higher than 30 dBm. The receiver can also be protected from high power SI signal by using only a single stage of a Kautz and GALL filter. Figure 9d,e shows that after passing through the Kautz and GALL filter, SI signal power is reduced to a much lower level that is below sensitivity level, and the power received at the input of the Rx is approximately equal to the desired signal, which shows that SI signal is almost cancelled, and the remaining error can be treated as low power noise. From Figure 9, SI signal power is significantly dominant over the desired signal before applying the proposed SI cancellation techniques. As a result, the total power at the Rx input is approximately equal to the SI signal power. However, after applying SI cancellation techniques, the SI power becomes negligibly small, and the total power is predominantly similar to the signal power.  
Figure 8: Link budget analysis: (**a**) Transmitter chain; (**b**) receiver chain.  
Figure 9: Power of self-interfering signal components before and after SI cancellation techniques. SI power at receiver: (**a**) without any SI cancellation; (**b**) with 30 dB antenna isolation and CSI technique; (**c**) with 40 dB antenna isolation and CSI technique; (**d**) with the Kautz filter as an SI cancellation technique; (**e**) with the GALL filter as an SI cancellation technique.