In the present work, a metamaterial‐based insulator is proposed as a mean to achieve both highly compact and loosely coupled array of antennas. Its main working principle is summarized through a general qualitative analysis. The theoretical results are supported by experimental evidences. The chosen operating frequency is 2.4 GHz considering that it is a usual frequency for many indoor wireless applications. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1420–1423, 2017

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Deployment of 5G network infrastructure is a timely opportunity for millimeter-sized battery-free sensors. However, millimeter-wave (mmW) devices often suffer from high conversion loss and path loss that are heavily limiting their communication/detection distance, especially for the case of harmonic transponders based on Schottky diodes. A deep and comprehensive parametric understanding of the second-harmonic generation mechanism of Schottky diodes in the mmW 5G bands can help us to identify suitable diodes or guide diode fabrication to reduce transponder conversion loss. This work reveals that both diode nonlinear junction resistance and capacitance contribute to the second-harmonic generation across the mid-band (sub-7 GHz) and high-band (mmW) 5G frequency bands. However, the nonlinear junction capacitance dominates the second-harmonic generation in the mmW bands. Without Joule heating during the conversion process, the capacitive nonlinearity is more efficient than the resistive nonlinearity, which means that a Schottky diode with a lower junction capacitance will efficiently reduce its associated conversion loss. The VDI GaAs zero bias diode with a low zero bias nonlinear junction capacitance (19.19 fF) shows superior conversion loss performance, which indicates that it can be employed to enhance the detection distance of battery-free harmonic transponders in the mmW 5G bands.

A closed-form solution for the continuous inverse class E (class E À1 ) design space is presented for the first time 1 . Analogous to the class-E power amplifier (PA) modes, the zero current and its derivative conditions needed for the class E À1 switching action can also be shown to be satisfied with any second harmonic susceptance. The complementary relationship between the continuous PA modes for class E and class E À1 are analytically proven. Signal integrity limitations on the continuous class E and class E À1 PA modes are demonstrated to exist and to limit the useful range of solutions of the design space. 2 Consequently, the maximum achievable bandwidth using the continuum of solutions in both class E/E À1 is not 2 octaves as previously reported but only 1 octave.