Digital potentiometers are substantial components for the design of many mixed-signal electronic circuits and systems. Their capability to program resistance value almost instantly provides hardware designers an additional level of freedom. Unfortunately, this feature is limited to DC and lower frequencies, due to parasitic effects. Nowadays, memristors as continuously tunable resistors are becoming candidates for potentiometer successors. Memristors are two-terminal non-volatile devices which have less significant parasitic effects and a wide resistance range. The memristance value can be changed on the fly. Using nanotechnology, memristor implementation has a nanoscale footprint with nanosecond transition between resistive states. In this paper, we present a comparison between the frequency characteristics of digital potentiometers and the only commercially available memristors. Memristor parasitic effects dominate at higher frequencies which extends the bandwidth. In order to present the advantages of memristive circuits, we have analyzed and implemented tunable circuits such as a voltage divider, an inverting amplifier, a high-pass filter, and a phase shifter. A commercially available memristor by KnowM Inc. is used for this purpose. Experimental results obtained by the measurements verify that a memristor has equal or better characteristics than a digital potentiometer. Memristive realizations of voltage dividers and inverting amplifiers have a wider bandwidth, while filters and phase shifters with a memristor have almost identical frequency characteristics as the corresponding realizations with a digital potentiometer.

When the memristor was fabricated for the first time, it launched an entirely new field of research. Many of the published papers regarding memristors are primarily theoretical and are based on computer simulations. Some recent papers analyze the memristor’s programming circuits, but to the best of the authors’ knowledge, no memristor has been embedded into a commercial analog circuit. This paper is practically oriented and it is based on the experimental results obtained by measurements on the circuit prototype. We present a solution for automated programming of a commercially available memristor and its implementation in tunable active bandpass filter design. The novelty of this paper is that the active bandpass filter’s central frequency could be programmed during the filter operation, so a pause for memristor state-switching is not required. The experimental results are promising, and open up possibilities for the memristor’s application in analog systems.

This paper presents a dual-band bandpass filter with passband switchability controlled by using memristors. The memristor is a good choice as a control element due to its characteristics, such as low-power consumption, no bias needed, good electrical characteristics, and no moving parts. The filter’s reconfigurability is achieved by using memristors to selectively connect filter elements to ground. For the filter realization, multilayer technology with quasi-lumped elements has been chosen because of filter size miniaturization. Circuit-level simulations were initially used for quick analysis, followed by 3D EM simulations to validate the expected functionality of the proposed design concept. The results confirm the feasibility of a very small dual-band bandpass filter with independently controllable passbands. The frequency response of each of the two passbands (3.5 GHz and 5.8 GHz) can be tuned with negligible impact on the other passband by controlling the states of the memristors. The filter footprint area is equal to 0.10 λ_g × 0.12 λ_g, where λ_g is the guided wavelength at 3.5 GHz.

As reported in the open literature, there are many memristor models for the circuit-level simulations. Some of them are not particularly suitable for microwave circuit simulations. At RF/microwave frequencies, the memristor dynamics become an important issue for the transition process. In this paper we present a number of different SPICE memristor model groups. Each group is explained using representative models, which are analysed and compared from the microwave circuit analysis viewpoint. We consider the model behaviour at RF/microwave frequencies and the memristance setting issues. Results are compared and the best models are recommended.

This paper discusses the possibility of applying memristors in microwave passive circuits such as filters. Basic information about memristor like theoretical assumptions, realisation, structure, and physical properties of the component are presented. We analyze behavior of two microwave filters: end-coupled bandpass filter and hairpin filter. They are both bandpass filters, where the end-coupled filter is designed to operate at the center frequency of 6 GHz, and the hairpin filter is designed at the center frequency of 1 GHz. We analyze these filters with LTspice. The filters are realized in two ways, namely when using resistors, and when using memristors. Ideal memristors are used, and idealized circuits are analyzed in order to confirm functionality of implementations. The results show that the application is possible, without losing the quality of the filter characteristics