## 4 Results and Discussions
The CIR after the calibration is \(-\)40.2 dBc at 420 MHz, which is very close to the in-band, and gradually improves up to \(-\)71.2 dB as the blocker  
Figure 9.1 IM2 calibration performance measurements. (**a**) Spectrum, (**b**) results over the UHF band. frequency moves farther away out of the band. The measured CIR can also be translated to the maximum tolerable two-tone blocker power of \(-49.8\)--\(18.8\) dBm. Then, considering \(P_{offset}=6.56\) dB as discussed in Section 2, we can conclude that the equivalent OFDM blocker power of \(-43.2\)--\(12.2\) dBm can be tolerated by this RF receiver. Another important interference tolerance is against a single tone blocker. The measured results are plotted in Figure 9.2 The desired signal power is set to \(-98\) dBm at 403.5 MHz, which is 3 dB higher than the sensitivity level. The single-tone blocker signal across the VHF and UHF band is injected together, and its power is raised up to a point such that the output SNR becomes 17 dB in the same reason described earlier. The CIR at a frequency that is only 4 MHz away from the desired tone is found to be \(-41\) dBc, which corresponds to the maximum tolerable single-tone blocker power, is \(-57\) dBm. However, in general, the maximum tolerable CIR shows much better performance as low as \(-70\)--\(77\) dBc for the rest of the band between 50-370 MHz and 430-900 MHz. One exception is observed at a half LO frequency near 200 MHz, where the CIR is observed to be \(-49\) dBc. Although the MedRadio standard [1] does not clearly state this, such a limited set of exceptions would be generally accepted for the overall system operations because it can be avoided through high-level channel classification and a search process as is typically done in the Bluetooth receiver for internet-of-things (IoT) applications [28; 29]. Figure 9.3 Measured maximum tolerable CIR against single-tone blocker. Figure 9.4 Measured maximum tolerable CIR against two-tone blocker. The 1 dB gain desensitization against the single-tone blocker is measured and shown in Figure 9.5 The worst point appearing at 403.5 MHz corresponds exactly to the input-referred 1 dB compression power (\(IP_{1 dB}\)) of the receiver, which is \(-40.8\) dBm. As the blocker frequency moves away from the in-band, the 1 dB desensitization power continually grows from \(-26.7\) dBm at 350 MHz to \(-9\) dBm at 100 MHz for the lower band and also from \(-32.7\) dBm at 450 MHz to \(-16.8\) dBm at 900 MHz for the upper band. Key performances of this work are summarized and compared with previous CMOS MedRadio receivers in Figure 9.6 It should be noted that most of the previous works [4; 5; 12; 14; 15; 16] did not address the OOB blocker tolerance performances. Only a few works reported selectivity performances. [PERSON] et al. [18] reported an OOB CIR of \(-30\) dBc against the VHF band interference between 30 and 70 MHz, and [PERSON] et al. [12] demonstrated the ACR performance of 15 dB in their MedRadio receiver. [PERSON] et al. [19] reported the CIR of \(-10\) dB in their 915 MHz OOK receiver. Such performances should be compared to the CIR against the single tone blocker of this work. As discussed in Figure 14, this work shows much better performance, which is better than \(-41\) dBc without an exception, or even better than \(-70\) dBc if two exceptions are allowed at the half LO and 4 MHz away in-band frequencies. As can be seen in Table 1, this work is the first reporting the OOB CIR performances against the two-tone and single-tone blockers, which can be translated to the maximum tolerable OOB blocker power levels. Additionally, the maximum tolerable CIR against the two-tone blocker can be translated to the maximum tolerable CIR against the OFDM blocker when the \(P_{offset}\) of Equation (8) is taken into account.