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Multiferroic materials and devices have attracted intensified recent interests due to the demonstrated strong magnetoelectric (ME) coupling in new multiferroic materials and devices with unique functionalities and superior performance characteristics. Strong ME coupling has been demonstrated in a variety of multiferroic heterostructures, including bulk magnetic on ferro/piezoelectric multiferroic heterostructures, magnetic film on ferro/piezoelectric slab multiferroic heterostructures, thin film multiferroic heterostructures, etc. Different multiferroic devices have been demonstrated, which include magnetic sensors, energy harvesters, and voltage tunable multiferroic RF/microwave devices which are compact, lightweight, and power efficient. In this progress report, we cover the most recent progress on multiferroic heterostructures and devices with a focus on voltage tunable multiferroic heterostructures and devices with strong converse ME coupling. Recent progress on magnetic-field tunable RF/microwave devices are also covered, including novel non-reciprocal tunable bandpass filters with ultra wideband isolation, compact, low loss and high power handling phase shifters, etc. These novel tunable multiferroic heterostructures and devices and tunable magnetic devices provide great opportunities for next generation reconfigurable RF/microwave communication systems and radars, Spintronics, magnetic field sensing, etc.

A gain and bandwidth tunable active-RC multiple-feedback (MFB) fourth-order low-pass filter is presented, which exhibits four different bandwidths of 10, 20, 30 and 40MHz and four different gain settings of 0, 4, 8 and 12dB to meet the requirements of the cellular vehicle-to-everything (C-V2X) standards. The filter uses the cascade of two biquad MFB cells. Gain and bandwidth programmability is achieved by using programmable capacitor and resistor arrays. A logic block is implemented in the filter to adjust the gain transfer function for every tuning option. Also, two-stage miller op-amp topology is chosen to implement biquad MFB cells for minimum complexity and maximum efficiency in low voltage operation. The filter is designed in 65-nm CMOS technology and occupies a 0.181mm² area and it totally consumes 13.41mW from the 1.2V supply voltage. To the best of the author’s knowledge, this work is the first CMOS baseband filter design that includes both gain and bandwidth programmability implemented for C-V2X applications.

Narrow bandwidth and specific incident angle are the main drawbacks in real-life applications for the existed carpet cloaking based on the acoustic metasurface (AM). Here, we tackle to get over the problems by proposing a reprogrammable AM. The unit cell is composed of water sink and filling nozzle. By incorporating an external water pumping system into each individual unit cell, the reflected phase can be readily regulated. Since the pumping process is reversible, the AM is reprogrammable under the control of the water pumping system in the frequency range of 3430–6860Hz. Both the acoustic cloaking and disguising are designed based on the proposed AM. The double security for the target object can be ensured to avoid being detected by combining the two designs. Simulated results with the finite element method indicate that the acoustic cloaking and disguising can work in the broad bandwidth of 66.7% of the central frequency with full-range incident angles from $-90^{\circ }$ to $90^{\circ }$. Our design shows promise for applications in realizing the practical skin cloaking and disguising one step closer.

Metamaterials (MMs) represent a group of exciting artificial materials that interact with electromagnetic waves in unnatural ways. The motivation behind MM research arises not only from fundamental interest in their unique physical properties but also from the desire of creating smarter materials for advanced technological applications. Despite an abundance of studies on numerous shapes, sizes and operating frequencies, the use of conventional metal-dielectric components makes the post-fabrication physical properties of MMs unalterable. Therefore, the integration of other nonlinear materials is necessary for exploring the functional limits of MMs. In this regard, a mono-layer of carbon, the so-called graphene, with its unique electrical conductivity is identified as a promising candidate. This review discusses the recent progress on tunable graphene-based THz MMs for perfect absorption and electromagnetically-induced transparency effects. A short overview of prospect challenges and tendencies is also given for future development of graphene-integrated MMs towards upcoming smart meta-devices.

In this paper, a new active element namely Dual-X current conveyor differential input transconductance amplifier (DXCCDITA) is proposed. The DXCCDITA is utilized in designing four minimum component fully cascadable all pass filter (APF) structures. The designed all pass filters require only single active element and one/two passive elements for realization thus making them a minimum component implementation. Two among the four presented all pass structures require only a single capacitor for implementation. A scheme for realizing nth order all pass filter is also suggested and a fourth order voltage mode (VM) filter is developed from the proposed scheme. The effect of non-idealities on the proposed all pass filters is also studied. A simple oscillator is also developed using one of the all pass filter structure. The oscillator required only one DXCCDITA, two capacitors and one resistor for implementation. The DXCCDITA is implemented in 0.35$\mu$m TSMC CMOS technology parameters and tested in Tanner EDA. Sufficient numbers of simulations are provided to establish the functionality of all pass structures. The experimental results using commercially available integrated circuits (ICs) are also provided.

Traditional filters usually have low Q and gain values and it is difficult to adjust their center frequencies. Moreover, it is very complicated to analyze their transmission charateristics through conventional methods. Therefore, in this paper, a tunable differential N-path bandpass filter that uses a new adjoint network method to analyze the transmission characteristics of the differential N-path structure is proposed. The filter circuit adopts a novel circuit structure consisting of two differential N-path structures, two transconductance amplifiers and an off-chip transformer. The differential structure eliminates even harmonics, the transconductance amplifier increases the circuit gain and the off-chip transformer acts as a balun, improving the filter’s Q value and achieving impedance matching. Unlike the traditional switching capacitance method used for analyzing the differential circuit structure, the method proposed in this paper does not involve complicated calculus operations. In fact, the method greatly simplifies these complex operations, and the transmission function of the circuit can be obtained through simple algebraic operations. The proposed filter was designed using TSMC 180nm CMOS process. Simulation results for a differential four-path bandpass filter formed under 1.2V supply voltage show that the gain of the filter is greater than 8.5 dB, the center frequency can be adjusted from 0.1GHz to 1GHz, the in-band insertion loss S11 is greater than 10 dB, the out-of-band IIP3 is greater than 10 dBm, the out-of-band rejection is 28 dB and the noise figure is less than 2.2 dB at $f_s=300$MHz.