# A 12 dBm B1 dB N-Path Notch Filter for Transmitter Leakage Suppression in Wideband Receiver
## 5 Measurement Results
### Linearity and NF  
A single tone at f\({}_{\mathrm{LO}}\) is used to measure BldB. A single tone at \(f_{LO}\) + 20 MHz is used to measure P1 dB in the passband. The third-order input-intercept-point (IIP3) profile is measured by injecting two-tone tests with a frequency at \(f_{LO}\) + 20 MHz and \(f_{LO}\) + 21 MHz.  
Figure 14: (**a**) Measured S21 of the proposed notch filter across the RF tuning range; (**b**) measured S21 and S11 at \(f_{LO}\) = 450 MHz. Some variations between measurements (solid) and simulations (dashed) were observed.  
Figure 13: Chip micrograph and assembled board of the notch filter with CLC inductor L\({}_{\mathrm{T}}\).  
The large block signal causes compression of the desired signal. The measured blocker B1 dB is 12.3 to 13.6 dBm. The measured P1 dB is 12.8 to 14 dB, and the IIP3 ranges between 22.3 and 25.2 dBm across the tuning range, as shown in Figure 15.  
Figure 16a shows rejection for a bandwidth of 800 khz versus block power at \(f_{LO}\) = 450 MHz. The notch depth was degraded by 1 dB for a 12 dBm block power, and the filter maintained >20 dB of rejection for a bandwidth of 800 kHz. In the RF tuning range, the min NF is 3.58 dB to 4.78 dB, as shown in Figure 16b. The NF at 600 MHz goes up by 1.2 dB. The blocker noise figure (BNF) is measured in the presence of a TX signal located at \(f_{LO}\) = 450 MHz and is plotted in Figure 17. The NF increases to around 9 dB with a 12 dBm TX leakage.  
Figure 16: (a) Rejection versus block power at \(f_{LO}\) = 450 MHz; (b) measured min NF across RF tuning range.  
Figure 15: (a) Measured and simulation B1 dB across the RF tuning range; (b) measured and simulation P1 dB and IIP3 across the RF tuning range.  
Table 1 summarizes the power consumption at different frequencies when the proposed notch filter is tuned from 0.3 to 0.6 GHz. With a 12 dBm TX leakage, the clock power consumption is 186 to 242 mW over the tuning range. Table 1 shows that the switch buffers mainly consume power, which drives the large switches with eight-phase nonoverlap 12.5% duty cycle clocks. The buffer power consumption is proportional to the switch size, with smaller switch sizes leading to lower insertion loss.  
Table 2 summarizes the performance of the proposed notch filter and compares the measured results with state-of-the-art N-path-based passive notch filters. The filter linearity and maximum rejection are substantially improved compared to the conventional LNA shunt notch structure [19]. Compared to the N-path bandpass filter with a series notch architecture presented in [12], the proposed filter demonstrates advantages in both B1 dB and P1 dB, while also meeting the requirements of wideband receivers and reducing power consumption simultaneously. Compared with [20,21], the proposed filter exhibits improved B1 dB and P1 dB. It is comparable to that in [22] in terms of noise and rejection performance, but with a large improvement in passband IIP3. Furthermore, compared to the design in [16], which utilizes an N-path inverted shunt notch architecture, the proposed filter incorporates an adjustable transmission line structure. This design effectively reduces insertion loss by optimizing impedance and achieves a smaller insertion loss shortfall across the RF tuning range.  
\begin{table}
\begin{tabular}{c c c} \hline
**With 12 dBm TX Leakage** & **Frequency = 0.3 GHz** & **Frequency = 0.6 GHz** \\ \hline Clock Balun & 7.2 & 9.1 \\ Divider & 5.1 & 8.5 \\ NANDs and Duty Cycle & 26.5 & 28.6 \\ Calibration & & \\ Buffers & 147.2 & 195.8 \\ Total & 186 & 242 \\ \hline \end{tabular}
\end{table}
Table 1: Power consumption table with 12 dBm TX leakage.  
Figure 17: Measured and simulated BNF with a blocker located at 450 MHz.