Magneto-dielectric antennas (MDAs) provide small sizes, enhanced bandwidths, and frequency/polarization agility. We describe the fabrication and efficiency characterization at 0.4–0.8 GHz of five microstrip MDAs, whose gradually thicker substrates were 3D-printed using an off-the-shelf polylactic acid (PLA) filament doped with ferromagnetic particles. It was experimentally discovered that efficiency increases monotonically from 12% (−9.2 dB) to 37% (−4.3 dB) as substrate thickness goes from 1.6 to 4.3 mm; the rate is faster than expected for microstrip antennas. Numerical analysis indicated that the apparent magnetic loss tangent of the MD substrate experiences a threefold decrease as the 3D printer deposits more layers of iron-doped PLA. The MDAs exhibit radiation quality factors that are 3.7–7.2 times better than the dielectric counterparts. Moreover, a simple optimization of ground plane size could increase efficiency to 55% (−2.6 dB). The reduction in magnetic loss is attributed to a reduction in eddy current loss due to the separation of agglomerate iron particles. Therefore, despite the inherently lossy material used, the potential of 3D-printed MD substrates in providing acceptable antenna efficiencies is demonstrated together with unprecedented design freedom and fabrication flexibility.

This note proposes a log-periodic microstrip antenna (LPMA), particularly after developing possible feed structures. The process develops an appropriate feed such that the LPMA can exhibit almost end-fire characteristics such as a log-periodic dipole antenna. The study simulated two LPMAs, one with five elements and the other with seven elements, followed by measurements on a five-element prototype. The five-element prototype LPMA with such a feed exhibits a bandwidth of 2.2–3 GHz. Over this band, radiation patterns remain consistent with a gain of 9.8 dBi. Simulated results follow the measured ones closely.

Time-domain characterization of a microstrip patch antenna with circular corner truncation to achieve polarization reconfigurability is presented. By applying zero bias, forward bias, and reverse bias to the four PIN diodes, the antenna can radiate with linear polarization (LP), right hand circular polarization (RHCP), and left hand circular polarization (LHCP). The circular cuts reduce centre-frequency shift from linear to circularly polarized states, compared with conventional straight cuts. Time-domain simulation and measurement are carried out to show the switching characteristics of the proposed antenna, and it is established that satisfactory switching speed can be obtained using a simple low-cost driver circuit.

In this work we assess the feasibility of fabricating a matrix of antennas for the millimeter (mm)-wave band using the “Multi Chip Module – Deposited (MCM-D)” process. The main focus of the design is to minimize the cross coupling between the antennas fabricated on the common substrate. We investigate the use of a virtual cavity formed by metalized vias in order to reduce the cross coupling to the neighboring cells. The radiation efficiency is analyzed in detail, and experimental results of a 2 × 2 array are presented.