## 3 Results and Discussions
### 0.34 THz Mixers' Performances  
The SHM performances were characterized by the Y-factor method at room temperature. There have been many excellent reports about noise temperature measurement of THz receivers or mixers, such as [25; 35], where the large temperature difference between LN\({}_{2}\) and ambient loads (295/77 K) ensures test accuracy. In this paper, the ambient calibration load (288 K) and the hot calibration  
Figure 12: Measured (**a**) output power and (**b**) frequency conversion efficiency of the 0.34 THz tripler with different input power levels from 324 GHz to 352 GHz. Figure 13: Performance comparison of (**a**) simulated and measured efficiency with 100 mW input power and (**b**) measured output power of three different tripler modules with 100 mW input power. load (361 K) (from TK Inc.) were presented alternately at the input of the receiver through the feed horn antenna. The setup, illustrated in Figures 14 and 15, was mounted on an optical table, and the experimental platform was relatively simpler. Furthermore, in order to reduce the test error, we removed unreliable data, such as too large or too small data when measuring, and the noise temperature at each frequency point was obtained by averaging multiple sets of valid data. The mixer's LO was provided by a 170 GHz doubler driven by an E-band \(\times\)9 multiplication chain, with a maximum LO power up to 6 mW. As the power level radiated from the hot/ambient load was very low, a 60 dB high gain IF amplifier was cascaded at the IF output port of the mixer. The final amplified power was monitored by Agilent P-Series Power Meter N1911A with a wideband power sensor. The DSB noise temperature and conversion gain of the receiver (including the SHM and IF chain) can be calculated through Y-factor measurement. Since the noise figure and gain of the IF chain were already known, the DSB noise temperature and conversion loss could be extracted according to methods detailed in [36]. Eventually, the measured performances of the SHM. in comparison with simulation results, were curved, as shown in Figure 16. The DSB noise temperature and DSB conversion loss of SHM were lower than 1500 K and 9 dB in the range of 325-352 GHz, respectively, and reached the lowest values of 915 K and 6.9 dB at 335 GHz. In fact, the deviation of the measured noise temperature from the simulation was within expectations. All the measured results included internal waveguide transmission loss, flange connection loss, and feed horn antenna loss. Furthermore, the hot temperature was difficult to ensure precisely and there was an error in the coupling from the horn to calibration loads. Moreover, the measured results of the three mixers at room temperature are  
Figure 14: Schematic diagram of 0.34 THz SHM’s noise temperature test setup. Figure 15: Photograph of the 0.34 THz SHM’s noise temperature test platform using Y-factor method measurement. The ambient/hot calibration load, respectively, radiates broadband noise energy related to real-time temperature into the receiver through feed horn antenna. Every time the calibration load is exchanged the under-test receiver is position fixed. shown in Figure 17. In terms of noise temperature or operating frequency, the performance of different mixer modules was only slightly different. We also investigated published Schottky SHM performances in a similar frequency range, which are listed in Table 3. The DSB noise temperature and conversion loss of this work were close to or better than those reported in the other literature. Additionally, a hybrid integrated circuit with a flip-chip soldered diode chip was adopted in [37; 38; 39], which resulted in the inability to guarantee the consistency of multiple channels in a large array. Figure 16: Simulated and measured performances of 0.34 THz SHM from 320 GHz to 360 GHz (a) double sideband (DSB) noise temperature and (**b**) DSB conversion loss. Figure 17: Comparison of the measured DSB noise temperature of three different mixer modules.