## 3 Memristive Analog Design
### Memristive RF Circuits
#### 3.2.1 High-Performance RF Switches  
Radiofrequency switches (RFSs) are electronic devices that use radiofrequency signals to control the flow of current in a circuit [38; 39]. These switches are commonly used in telecommunications and wireless communication systems to route signals quickly and efficiently between different components and accurately switch between different frequency bands. They offer fast switching speeds, low power consumption, and high reliability, making them ideal for applications that require rapid signal switching and minimal power loss. Furthermore, complex systems can seamlessly integrate RFSs with other electronic components. Switches based on microelectromechanical systems and phase-change materials are being explored as potential solutions for achieving higher frequencies and improved performance in RF switches [40; 41]. However, these devices suffer from disadvantages such as large physical dimensions and high actuation voltages. Additionally, these switches \begin{table}
\begin{tabular}{c c c c} \hline
**Ref.** & **Type** & **Frequency Range** & **Memristor Type** & **Results Type** \\ \hline
[33] & Band-pass filter & 19.5 KHz–26 KHz & Commercially memristor & Measurement results \\ \hline
[34] & High-Pass Filter & 50 KHz & TiO\({}_{2}\) memristor model & Simulation results \\ \hline \multirow{2}{*}{[35]} & Low-pass filter with positive feedback loop & 198.94 Hz–771.9 Hz & \multirow{2}{*}{Memristor emulator} & \multirow{2}{*}{Measurement results} \\ \cline{2-2}  & Low-pass filter without a positive feedback loop & 230.8 Hz–803.7 Hz & & \\ \hline
[36] & High pass filter & 60 Hz & Memristor emulator & Simulation results \\ \hline
[37] & Low/High-pass filter & 398 kHz–5.3 MHz & Printed memristor & Measurement results \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of memristor-based filter. Figure 5: Experimental waveforms of magnitude–frequency characteristic of (**a**) topology A, and (**b**) topology B [35]. often have limited durability and reliability due to the mechanical nature of their operation. Efforts are being made to overcome these challenges by exploring alternative materials and designs, such as nanoelectromechanical systems, graphene-based switches, and memristor-based switches, which offer the potential for smaller sizes, lower actuation voltages, and improved performance. These advanced switches also have the potential to enable new functionalities, such as reconfigurable antennas and cognitive radio systems. Furthermore, ongoing research focuses on developing RF switches capable of operating at higher frequencies, including millimeter-wave and terahertz frequencies. This would enable faster data transfer rates and support emerging technologies like 5G networks and wireless communication systems. Additionally, efforts are being made to improve the power handling capabilities of RF switches to meet the increasing demands of high-power applications in fields like radar systems and satellite communications. Low ON resistance and minimal OFF capacitance are essential for low insertion loss and good isolation in RF memristive switches (RFMSs) [42]. Most RFMSs are electrochemical metallization memristors with asymmetric metal electrodes separated by a small gap or insulating layer [43]. This design enables precise control over the switching between high and low resistance states. Memristors are equivalent to parallel RC circuits, where R is the resistive state, and C is the between-electrode capacitance. Losses and substrate capacitance present higher-order effects [44]. These higher-order effects can affect the overall performance of RFMSs, leading to increased insertion loss and decreased isolation. Therefore, optimizing the design of RFMS to minimize these effects is crucial for achieving high-performance radio-frequency applications. Additionally, careful consideration of the materials used for the metal electrodes and insulating layer can further enhance the performance of RFMSs by reducing the parasitic capacitance and improving the switching speed.