# Design of a Broadband and High-Isolation CMOS Active Quasi-Circulator
## 3 Results  
In the case of Vds1, the bias condition is 0.5 V with a current of 71.1 mA, while the bias requirement for Vds2 is 1 V with a current of 5.7 mA. The overall power consumption came to 41.25 milliwatts. As functions of frequency, the insertion loss of the quasi-circulator is depicted in Figure 8a, which displays the measured values. S21 is around 4.8 to 10 dB, and S32 is approximately 3.4 to 9.1 dB. Based on the results of the simulation, the amplitude imbalance is found to be within the range of 1.5 dB. On the other hand, the result that was measured displays a greater deviation, which can be attributed to the excessively high \(g_{m1}\) transconductance. It can be observed from the figure that the simulation results of insertion loss are basically consistent with the measured results. The isolations of S31 and S13 are shown as a function of frequency in the range of 5 to 35 GHz in Figure 8b. These isolations were measured individually. Measured results show \(\mid\)S31 \(\mid\) is around 35-55 dB, and \(\mid\)S13 \(\mid\) is approximately 40-60 dB. There are some differences between the measured results and the simulation results, which may be caused by the parasitic capacitance of the internal circuit. Due to the fact that it is located in the forward path of the signal flow, high \(\mid\)S31 \(\mid\) isolation is often the most difficult to achieve in the active quasi-circulator design. By  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Components** & **Parameters** & **Components** & **Parameters** \\ \hline M1 & \begin{tabular}{c} 3 \(\upmu\)m/10/3 \\ Width/Finger/Number \\ \end{tabular} & Cs1 & 0.289 pF \\ \hline M2 & \
\begin{tabular}{c} 2 \(\upmu\)m/20/2 \\ Width/Finger/Number \\ \end{tabular} & Cs2 & 0.45 pF \\ \hline M3 &
\begin{tabular}{c} 3 \(\upmu\)m/43/1 \\ Width/Finger/Number \\ \end{tabular} & Cs3 & 0.3 pF \\ \hline L1 & 2 nH & Rb & 3.5 K\(\Omega\) \\ \hline L2 & 3.6 nH & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Circuit parameters of the active quasi-circulator.  
Figure 7: (a) Schematic and (b) photograph of the fabricated broadband and high-isolation quasi-circulator.  
adjusting the dimensions of the M3 FET, the phase cancellation approach is able to provide superior isolation of the S31 band while maintaining broadband operation.  
As can be seen in Figure 9, the measured NF in the 5-35 GHz band falls somewhere between 13 and 14 decibels, which is approximately 1 decibel higher than the simulation. At a frequency of 15 GHz, the simulated result of the input power 1 dB compression point (IP1 dB) is 2.8 dBm, while the measured result is 3 dBm from port 1 to port 2. There is a significant degree of concordance between the outcomes of the simulation and those of the experiment.  
The performance of the suggested quasi-circulator is compared with the performance of previous quasi-circulators that have been described [9; 11; 12; 13; 14]. The results are summarized in Table 2. It is possible for the quasi-circulator that has been designed to offer an extremely broad bandwidth of 28 GHz (147%). All of the insertion losses are lower than 10 decibels, and the isolation of the S31 signal that was produced is higher than 35 decibels. Not only does the proposed quasi-circulator have good port-to-port isolations, but it also maintains wideband functioning while maintaining a compact size. This is in comparison to the data that were presented.  
Figure 8: Measured (**a**) insertion loss and (**b**) isolation between port 1 and port 3 of the fabricated quasi-circulator as functions of frequency at 5–35 GHz.  
Figure 9: Measured and simulated (**a**) noise figure and (**b**) P1 dB of the quasi-circulator as functions of frequency at 5–35 GHz.