By employing varactor diodes in a metasurface, the resonance frequency of a high-impedance surface (HIS) can be changed by a bias voltage. To modulate the frequency of the reflected wave from such surfaces, a phase variation of more than 360° is required. To overcome the phase variation limitation (<360°) in a conventional active metasurface, we fabricated a metasurface with two resonances and manipulated both poles simultaneously to achieve a phase variation exceeding 360° for smooth modulation of the reflection frequency. Because of this wide variation in the reflection phase, it is possible to modulate a broad range of frequencies between 2.75 and 3.25 GHz with up to 1-MHz variation in the modulation frequency. The best spurious-free dynamic range (SFDR) for this frequency range is 20.7 dBc at 3.25 GHz.

We demonstrate a broadband tunable third-order intermodulation distortion (IMD) cancellation architecture using a left-handed transmission line (LHTL)-based phase shifter for a feedforward amplifier. The fabricated circuit reduces the third-order IMD of the main amplifier up to 17 dB after adjusting for any frequencies between 1.5 and 2.4 GHz when the frequency difference between the two tones is 2 MHz. In addition, the circuit maintains a spurious-free dynamic range that is greater than 55 dBc at the output. This effective broadband third-order IMD cancellation method is possible because of the broadband and linearly phase-tunable characteristics of the LHTL-based phase shifter.

A smooth interaction body force density and torque were evaluated in permanent-magnet (PM) systems by using the virtual air-gap scheme coupled with the finite-element method. The virtual air-gap method has been successfully applied to soft magnetic materials for evaluating the force density, global contact force, and optimal shape design. These force-calculating methods employing the virtual air-gap scheme have been called generalized methods. Unlike the soft magnetic materials, there have been few research works related to force density and global force in PMs. We evaluated the interaction body force density, which represents the smooth and pure interacting force field between PMs and other magnetic components, by withdrawing the self-body force density from the total body force density. From this result, the smooth interaction body force density can explicitly show the trend of resulting mechanical torque. The torque by the self-body force density, of course, was zero and the torque, here, was evaluated by using the total body force density. From the previous results, the torque by total body force density shows some numerical instability, and we used edge-force components in each element for removing the numerical instability. Finally, the global quantities, such as global force from the smooth interaction body force density and torque from the total body force density, were successfully evaluated and verified by the conventional force calculating methods, such as the Maxwell stress tensor method and the virtual work principle method.