In this paper, a novel tunable dual-band bandpass filter (BPF) with independently controlled passbands and constant absolute bandwidth (CABW) is proposed. The CABW passbands of designed dual-band BPF are obtained using manageable electric and magnetic mix coupling. Furthermore, the multiple transmission paths from the input port to the output port are extended for extra transmission zeros, which results in modified selectivity of the proposed dual-band BPF. The tunability and switchability of the developed filter can be implemented by introducing a single bias voltage of varactors for each band. For the tunable dual-band BPF, the simulated results show that the center frequency (CF) of the first passband varies from 2.38 to 2.68 GHz, and the CF of the second passband varies from 3.28 to 3.88 GHz, while 3-dB absolute bandwidths are 101 ± 7 MHz and 98 ± 4 MHz, respectively. Moreover, the two passbands of the filter can also be independently switched by removing the voltage imposed on the varactor CV1 and CV2. The measured results agree well with simulated results, which verify the design theory.

Low loss, ferroelectric, fully-printed varactors for high-power matching applications are presented. Piezoelectric-induced acoustic resonances reduce the power handling capabilities of these varactors by lowering the Q-factor at the operational frequency of 13.56 MHz. Here, a quality factor of maximum 142 is achieved with an interference-based acoustic suppression approach utilizing double metal–insulator–metal structures. The varactors show a tunability of maximum 34% at 300 W of input power. At a power level of 1 kW, the acoustic suppression technique greatly reduces the dissipated power by 62% from 37 W of a previous design to 14.2 W. At this power level, the varactors remain tunable with maximum 18.2% and 200 V of biasing voltage.

Natural structural materials (NSMs) such as nacre, teeth, bones and crustacean exoskeleton are usually made of weak biomaterials arranged in specific structural design imparting them remarkable mechanical characteristics. Such hierarchical structural layouts found in nature encourage designing of mechanically desirable synthetic structural materials (SSMs). Among variety of natural hierarchical layouts, this paper specifically focuses on helicoidal architectural design found in the tough dactyl club of mantis shrimp. We first decode the mechanics behind helicoidal microstructural design and document the development of impact resistant macroscale helicoidal architectured synthetic structural materials (HA-SSMs). Next, near-field electrospinning technique (NFES)- both melt (polycaprolactone) and solution (polyvinylidene fluoride) type has been discussed in detail, as a novel method for developing lab scale 3D biomimetic HA-SSMs in micro-nanoscale. Further, the effect of the helical arrangement, size of substructures and surface treatment on strength and toughness of NFES fabricated HA-SSMs samples is analysed.

We report on the exploration of perpendicular exchange bias in iron platinum/nickel oxide (FePt/NiO) bilayer thin films grown using pulsed laser deposition (PLD) on MgO (100) substrates. Exchange bias is an important property for giant magnetoresistance, and, as such has promise for applications in spin valves, magnetic sensors and magnetic random access memory. The magnetic L10 phase of FePt is known for having high perpendicular magnetic anisotropy, tunable coercivity/grain size and large magnetic storage density. The FePt layer was first deposited directly on MgO, followed by the deposition of the NiO layer on top of the FePt layer. The coercivity of the L10 FePt layer was tuned during growth to form a hard or soft magnetic layer. The FePt/NiO thin films grown for this study exhibit perpendicular exchange bias at 5K, as quantified using our SQUID measurements. XRD confirms parallel plane ordering between the MgO (200), FePt (002) and NiO (111) atomic planes while cross sectional TEM confirms the epitaxial growth of L10-FePt(001)<100>//MgO(100)<001> and the preferential growth of NiO on top of the FePt. Films of only FePt were grown to examine the surface architecture of the ferromagnetic layer and thus the interface of the FePt/NiO bilayer. The results from our XRD, TEM and magnetometry characterization of the FePt films and FePt/NiO bilayer thin films will be discussed.

An L-band frequency and rejection-level tunable SiGe HBT differential amplifier with dual stopband is presented. To achieve frequency and rejection-level tunable performance, dual LCR-tank circuit with an active load is incorporated into the design of the series feedback loops of the differential amplifier. The active load consists of a varactor diode represented as a variable C and a common-emitter transistor represented as a variable R. The frequency and rejection level can be tuned independently by controlling a cathode bias voltage of the varactor diode or a base bias voltage of the transistor. The implemented 0.35 μm SiGe HBT amplifier with dual stopband demonstrates a frequency tuning of 0.53–1.16 GHz and a rejection-level variation up to 9.5 dB. The input and output return losses are better than 17.5 and 11 dB over 0.2–1.5 GHz, respectively. The measured P1dB is+3 dBm and IIP3 is 0 dBm with Vcc = 6 V and Ic = 8 mA.