## 5 Conclusions  
In order to find the location of the marker, the existing method uses radiography-based fluoroscopic radiography to find the location through images [25]. However, the fluoroscopic radiography is large and heavy. In addition, fluoroscopic radiography has a high unit price. Therefore, the heavy size will induce difficulty in performing surgery. However, sensors to find markers are low in unit price and light in weight; the sensor is also small in size. Therefore, it is easy to handle during surgery. The most important thing in these  
Figure 8: Experimental results for the designed oscillator (V\({}_{\text{DS}}\) = 3 V, I\({}_{\text{D}}\) = 40 mA): (**a**) phase noise, (**b**) output power, and (**c**) second harmonic suppression. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Reference**} & \multirow{2}{*}{**Frequency** **(GHz)**} & \multicolumn{2}{c}{**Phase Noise** **(dBc/Hz) at**} & \multirow{2}{*}{**Output** **Power**} & \multirow{2}{*}{**Q\({}_{\text{L}}\)**} & \multirow{2}{*}{**FOM (dBc/Hz)**} \\  & & **100 kHz** & & **(dBm)** & & \\ \hline This work & 10.08 & \(-138.13\) & 18.66 & 632 & \(-195.7\) \\ [10] & 10.98 & \(-121.6\) & 1.800 & \(-\) & \(-182.3\) \\ [11] & 10.00 & \(-95.40\) & 10.16 & 190 & \(-135.3\) \\ [12] & 9.883 & \(-97.60\) & 3.020 & 260 & \(-182.2\) \\ [13] & 9.010 & \(-104.3\) & 1.800 & 104 & \(-104.3\) \\ [14] & 10.11 & \(-108.7\) & 4.600 & 520 & \(-172.2\) \\ [15] & 9.850 & \(-124.8\) & 3.600 & 243 & \(-189.1\) \\ [16] & 6.200 & \(-104.62\) & 14.68 & 430 & \(-156.2\) \\ [17] & 9.960 & \(-128.30\) (@ 1 MHz) & 8.570 & 66.7 & \(-193.2\) (@ 1 MHz) \\ [20] & 8.080 & \(-109.94\) & 2.140 & \(-\) & \(-174.2\) \\ [21] & 8.172 & \(-112.0\) & 4.000 & \(-\) & \(-174.2\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison between the parameters of the proposed oscillator and those of oscillators developed in previous studies. sensors is the oscillator. Since the oscillator has a very low phase noise, it is considered to have excellent performance. The designed oscillator consists of a plane shape. The resonator has an open structure, and this resonator has not applied a via design method. Therefore, the resonator has a high loaded quality factor (Q\({}_{\text{L}}\)) because there is no loss of concentration of via energy [26,27]. When applying the proposed oscillator to a sensor, if the amplifier is connected, it can be used as a radar-based sensor with high performance, which would be very useful in finding markers installed on tumors. The reason is that markers are made of metal. When a signal generated from the oscillator is reflected through a metal marker, the sensor may detect a reflected signal to locate the tumor. Therefore, it will be important that the performance of the sensor to locate the tumor suppress the phase noise of the oscillator. In this paper, a low-phase-noise-X-band oscillator with a high-Q\({}_{\text{L}}\) resonator using an open-loaded T-type stub and split-ring structure is presented. The proposed oscillator has a high Q\({}_{\text{L}}\) and low phase noise because it is a resonator in which an open-loaded T-type stub and a split-ring structure are combined. The proposed oscillator can increase the Q\({}_{\text{L}}\) of a resonator by adjusting the length of an open-loaded T-type stub; thus, the phase noise of the oscillator can be sufficiently reduced. In addition, the resonator is very small. The oscillator has a high output power and can perform second harmonic suppression. The measurement results indicate that an output power of 18.66 dBm and second harmonic suppression of \(-\)34.40 dBc (at 13.26 GHz) can be realized. At an operating frequency of 10.084 GHz, the phase noise is \(-\)138.13 dBc/Hz at a 100 kHz offset. This low-phase-noise X-band oscillator can be fabricated with a monolithic microwave integrated circuit (MMIC) technique, owing to its entirely planar structure. It can be applied to sensors to detect the location of tissues during laparoscopic surgery.