This paper investigates an original concept of electro-geometrical analysis of flexible microstrip antenna. The research work is focused on the analysis of the innovative effect of “V”- shape folding on the resonance frequency and input impedance of microstrip patch antenna. The V-folded antenna is assumed to behave as an arm constituted by horizontal and tilted members which are geometrically characterized by the folding angle, a. The folding is characterized by the angle between the horizontal plane and the folded part of the patch antenna printed on a Kapton flexible substrate. The initially flat-configured planar antenna was designed to operate at about 2.45 GHz. The innovative design method of the V-shape folded flexible antenna is explained. Full wave electromagnetic simulations of different geometrical states of the flexible antenna were performed in the frequency range from 1 GHz to 5 GHz. Exceptional results of tilted surface radiating part of flexible patch antenna were found with a positive folding angle from amin=0° to amax=45°. It was understood for the first time in the area of antenna engineering that the resonance frequency is fluctuating according to typical sine damping in the function of the V-folding angle variation. The folded angle effect, which has never been understood before is discussed. In addition to the angle effect, the input resistance and input reactance of the V-folded flexible patch antenna is also plotted.

This paper introduces a model and design of an innovative bandpass (BP) negative group delay (NGD) distributed circuit. The passive circuit topology under study is constituted by fully distributed elements without lumped components. The NGD passive structure is implemented as a ladder shape topology composed of distributed transmission line (TL) elements. The S-matrix model is established from TL-based equivalent Z-matrix operations with respect to the ladder geometry. As a proof of concept, a two-cell ladder prototype is designed in microstrip technology, which is simulated, fabricated, and tested. The calculated and simulated measurements are in very good agreement with the validation of BP NGD behaviour. NGD value is better than −3 ns with centre frequency between 3.56 and 3.68 GHz over more than 30 MHz NGD bandwidth being observed. The circuit operates under insertion loss better than 5 dB and reflection loss better than 8 dB. This innovative BP NGD passive circuit can be useful in the RF and microwave engineering area, for example, to reduce the signal propagation delay in the upcoming and 5G telecommunication systems.