This work details the design of single- and double-stage maximum gain and low-noise high-frequency amplifiers at 2.4GHz using a compact carbon nanotube field-effect transistor model, which is initially calibrated with hysteresis-free experimental data from a technology suitable for high-frequency applications. Parameters of the compact model represent CNTFETs with maximum high-frequency gain and reduced highfrequency noise by eliminating the metallic tubes contribution. Studies on linearity of the amplifiers as well as the impact of the quality factor of the inductors used in the stabilization network and the density of the nanotubes on amplifier performance are presented. Results of RF amplifiers show that CNTFETs are credible contenders for developing applications in S-band because of their gain (around 12 dB for a double-stage gain design), low noise (NFmin = 1:5 dB for a single-stage LNA) and linearity performance (OIP3 around 15dBm for a single-stage gain amplifier design).

This article presents the design of high-frequencydown-conversion mixers using a carbon nanotube fieldeffecttransistor (CNTFET). An experimentally-calibrated semiphysicalcompact model for high-frequency CNTFET technologieshas been used. The designed mixer is proposed using atopology composed of a 90º hybrid coupler at a frequencyof 25 GHz with a coupling factor of 3 dB, a CNTFET andmicrostrip-based coupling networks. The mixer operates in theupper band for 5G communications.The RF signal is used at afrequency of 25 GHz for an intermediate frequency conversion(IF) of 1 GHz using a LO of frequency 24 GHz. The designyields a conversion gain of 20 dB whereas the RF/LO isolationis -18.9 dBm and the LO/IF isolation is -25.6 dBm with ananotube density of 40 CNT/μm. By increasing the densityof nanotubes to 100 CNT/ μm, the conversion gain and portisolation RF/LO figures of merit improve to 26 dB and -20.7dB, respectively. The mixer consumes 9.52 μW from a -1.5 V supply.

The United Nations has pushed for improved mobile connectivity, ensuring that 97% of the world’s population lives within reach of a mobile cellular signal. This is within the framework of objective nine regarding industry, innovation, and infrastructure for sustainable development. The next challenge is for users to know the quality of this service. The Long-Term Evolution (LTE) network’s quality of service (QoS) is evaluated with key performance indicators (KPI) that only specialists can interpret. This work aims to assess the QoS and effectiveness of the fourth-generation (4G) LTE network using a weighted fuzzy inference system. Analytic Hierarchy Process (AHP) is integrated to rank the fuzzy rules. The KPIs that are considered for the evaluation are download speed, upload speed, latency, jitter, packet loss rate, reference received signal power (RSRP), and reference received signal quality (RSRQ). The evaluated data were collected collaboratively with end-user equipment (UEs). Different usage scenarios are contemplated to define the importance according to the positive impact of the QoS of the LTE mobile network. The advantage of the weighted fuzzy inference system concerning the fuzzy inference system is that each KPI is assigned a different weight, which implies having rules with hierarchies. In this way, the weighted fuzzy inference system provides two indices of quality and effectiveness. It can be a valuable tool for end users and regulatory bodies to identify the quality of the LTE mobile network.