## 3 Memristive Analog Design
### Memristive RF Circuits
#### 3.2.1 High-Performance RF Switches
In [45], a nanoscale RF switch is implemented using a nonvolatile memristive device with a pair of electrochemically asymmetric metal electrodes separated by a nanometer-scale air gap, which allows for the efficient and reliable switching of radio frequency signals. The use of a nonvolatile memristive device ensures that the switch retains its state even when the power is turned off, providing long-term stability and durability. Also, it allows for reliable and stable switching operations, while the asymmetric metal electrodes provide efficient control over the switch's performance. The nanometer-scale air gap ensures minimal interference and maximizes the switch's overall efficiency. The switch uses silver (Ag) as the active metal, offering low bulk resistivity and an effective dielectric constant, and its nanoscale feature size provides low insertion loss, high isolation, competitive linearity, and power-handling capabilities. The switch's nanoscale feature size also allows for improved thermal management, reducing the risk of overheating and increasing its overall reliability. Furthermore, the use of silver as an active metal enhances the switch's durability and longevity, making it suitable for long-term applications in various industries. The nanoscale RFMS can operate with a voltage as low as 0.4 V and boasts an ON/OFF conductance ratio of up to 10\({}^{12}\). This nanoscale RFMS offers significant advantages in terms of low power consumption and high performance. Its ability to operate at such a low voltage makes it suitable for various applications, including energy-efficient electronics and sensor devices. The switch's performance up to 110 GHz is measured, showing low insertion loss (0.3 dB at 40 GHz), high isolation (30 dB at 40 GHz), an average cutoff frequency of 35 THz, competitive linearity, and power-handling capabilities. Additionally, the RFMS exhibits excellent reliability and stability over extended periods of operation, making it suitable for a wide range of applications in high-frequency communication systems. Furthermore, the switch's compact size and low power consumption make it an attractive choice for integration into portable electronic devices. A non-volatile memristive RF switch with a Copper/Nafion/Gold structure on a coplanar waveguide is proposed in [46]. The design incorporates compensation for its parasitic effect and investigates the feasibility of its fabrication process. The compensation for parasitic effects ensures the reliable and efficient operation of the switch, further en hancing its performance. Full-wave simulations up to 10 GHz predict good performance, with ON-state insertion and return losses better than 0.54 and 25 dB, respectively, and OFF-state isolation higher than 22.8 dB. The proposed design also demonstrates low power consumption and high linearity, making it suitable for various applications in microwave and millimeter-wave systems. The simulation results validate the effectiveness of the compensation technique, confirming the feasibility of the fabrication process and highlighting the potential of this coplanar waveguide structure for practical implementation. In [47], a novel switching device for microwave systems using nanoionics is presented. The device uses an electrochemical process to form and remove a conductive metallic bridge, resulting in low insertion loss, isolation, voltage, power, and energy consumption. Its simple planar geometry allows for easy integration into microwave power distribution circuits. Table 2 summarizes the performances of the discussed memristor-based RF switches. The table includes key metrics such as frequency range, insertion loss, and isolation for each switch design. These performance metrics provide valuable insights for comparing the efficiency and effectiveness of different memristor-based RF switches. Furthermore, the data presented in Table 2 allows for a comprehensive evaluation of the capabilities of each switch in terms of RF signal processing.