# Ku-Band Mixers Based on Random-Oriented Carbon Nanotube Films
###### Abstract  
Carbon nanotubes (CNTs) are a type of nanomaterial that have excellent electrical properties such as high carrier mobility, high saturation velocity, and small inherent capacitance, showing great promise in radio frequency (RF) applications. Decades of development have been made mainly on cut-off frequency and amplification; however, frequency conversion for RF transceivers, such as CNT-based mixers, has been rarely reported. In this work, based on randomly oriented carbon nanotube films, we focused on exploring the frequency conversion capability of CNT-based RF mixers. CNT-based RF transistors were designed and fabricated with a gate length of 50 nm and gate width of 100 \(\upmu\)m to obtain nearly 30 mA of total current and 34 mS of transconductance. The Champion RF transistor has demonstrated cut-off frequencies of 78 GHz and 60 GHz for \(f_{T}\) and \(f_{\mathrm{m}xtr}\), respectively. CNT-based mixers achieve high conversion gain from \(-11.4\) dB to \(-17.5\) dB at 10 to 15 GHz in the X and Ku bands. Additionally, linearity is achieved with an input third intercept (IIP3) of 18 dBm. It is worth noting that the results from this work have no matching technology or tuning instrument assistance, which lay the foundations for the application of Ku band transceivers integrated with CNT amplifiers. carbon nanotubes; radio frequency transistor; mixer; conversion gain; linearity Article  
Klu-Band Mixers Based on Nanotube Films  
[PERSON], [PERSON], [PERSON], X.  
made good progress. And in the past two years, the cut-off frequency of carbon nanotube-based radio frequency transistors (RF FETs) has increased from 100 GHz [11; 17] to more than 300 GHz [18; 19] in the terahertz field, making important breakthroughs. Randomly oriented carbon nanotube film materials are often considered to be limited to medium- and low-performance devices and circuits. The large-scale uniformity of randomly oriented carbon nanotube films and the emergence of quasi-parallel arrangements in ultra-short channels (with significantly reduced overlap between carbon nanotubes) enable the construction of high-speed RF devices and circuits based on randomly oriented carbon nanotube films. High-performance transistors and ICs built by randomly oriented carbon nanotube films have been realized, such as ring oscillators (ROs) with 5.54 GHz of oscillation frequency [20] and RF transistors with over 100 GHz of pad de-embedding cut-off frequency [11]. Besides the potential in speed, randomly oriented carbon nanotubes have also been reported in works on preliminary RF devices such as amplifiers. For example, in 2021, [PERSON] et al. demonstrated RF amplifiers [21] with 11 dB of power gain and 15 dBm of output third intercept point (OIP3) in the X to Ku band for potential application in satellite communication. CNT-based devices could be used for frequency conversion, including frequency multipliers or mixers applied in RF transceivers. Mixers are very common in communication systems, which use a local oscillation (LO) signal to transmit (receive) an input signal of a certain frequency through an up-conversion (down-conversion) operation. Mixers based on transistors generally work in two ways [22], namely, passive and active. To date, most of the reported carbon-based mixers (including CNT and graphene) have been passive resistance mixers. The double-gate Bernal stacked double-layer graphene transistor passive mixer reported by [PERSON] et al. exhibited \(-\)12.7 dB conversion gain at 2 GHz [23]. [PERSON] et al. reported that passive mixers based on graphene exhibit 27 dBm of IIP3 (input third intercept) and \(-\)14 dB conversion gain at 2 GHz [24]. [PERSON] et al. demonstrated a double-balanced gate-pumped passive mixer integrated circuit that exhibited 21 dBm IIP3 and \(-\)33 dB conversion gain at 3.5 GHz [25]. Compared to passive resistance mixers, there have been fewer reports on active transconductance mixers than graphene-based active mixers, reported by [PERSON] et al. to exhibit \(-\)27 dB conversion gain at 4 GHz [26].