# Ku-Band Mixers Based on Random-Oriented Carbon Nanotube Films
## 4 Conclusions  
In summary, based on randomly oriented carbon nanotube films, we have designed and fabricated twenty-finger transistors with 50 nm gate length and 100 \(\upmu\)m gate width. The design of the multi-finger structure can reduce the resistance of the device and reduce the power loss due to impedance mismatch. In particular, we investigated the frequency conversion capabilities of active mixers built on CNT FETs in the X and Ku bands. Thanks to the large-scale uniformity of the randomly oriented carbon nanotube film material in which the CNTs are approximately parallel under the small channel, the RF performance of our CNT FETs showed a cut-off frequency (\(\left\langle f_{T}\right\rangle\)) of 78 GHz and a maximum oscillation frequency (\(f_{max}\)) of 60 GHz, respectively. The carbon nanotube-based mixers had conversion gains of \(-11.4\) dB to \(-17.5\) dB for input RF signals at 10 GHz to 15 GHz in the X and Ku bands and an IIP3 of 18 dBm. Without an on-chip matching network and tuning instruments assistance, our CNT-based mixer had a better frequency conversion capability in the Ku band compared to other nanomaterials such as graphene. These results demonstrate the performance advantages of CNT FETs and lay a foundation for the application of CNT-based mixers in the Ku band. Further, the mixers in this work are compatible with the carbon nanotube amplifiers in ref. [21] and silicon-based CMOS, which provide the possibility of Ku-band RF transceiver systems and more complex system-on-chip integration on silicon in the future.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/nano14050450/s1](https://www.mdpi.com/article/10.3390/nano14050450/s1)]([https://www.mdpi.com/article/10.3390/nano14050450/s1](https://www.mdpi.com/article/10.3390/nano14050450/s1)), Figure S1: Schematic diagram of device fabrication process; Figure S2: Structure and DC characteristics of a two-finger configuration RF transistor based on randomly oriented carbon nanotube films; Figure S3: Variation in conversion gain of CNT mixer under different measurement bias conditions; Figure S4: 1 dB compression point measurement; Figure S5: Statistical results of CNT-based RF mixers; Table S1: Comparison of the performance of CNT-based mixers with other materials mixers.  
Conceptualization, L.D. and Y.W.; methodology, J.Q.; validation, J.Q., M.C., X.C. and J.C.; formal analysis, M.C.; writing--original draft preparation, Z.L. and L.D.; writing--review and editing, M.C. and L.D.; visualization, L.F., X.C. and Z.L.; supervision, L.D. and Y.W.; project administration, L.D. and Y.W.; funding acquisition, L.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key Research and Development Program, grant number 2022 YFB4401603, and the National Natural Science Foundation of China, grant number 62171004.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.  
Figure 4: Benchmarking of mixers: comparison of (**a**) the conversion gain and (**b**) IIP3 of our CNT-based active mixers with those based on other nanomaterials [23; 24; 25; 26; 27; 34] and conventional semiconductors [35; 36].