Ultrawideband (UWB) communications, whether as integrated services within 5G wireless communications systems or as dedicated systems, holds the promise of rapid connections for voice and data as well as blazingly fast transfers of large amounts of data. Of course, an essential component in any UWB system is the antenna, which must provide the gain and efficiency to recover a wide range of UWB signals from the ambient noise.
A team of professors at the Patuakhali Science and Technology University (Patuakhali, Bangladesh) among other institutions developed a broken-heart-shaped microstrip patch antenna for UWB applications with electrical dimensions of 0.29ƛ × 0.17ƛ and maximum gain of 5.3 dBi across the broad frequency range of 2.90 to 10.70 GHz. It was designed and simulated with the aid of various software approaches, including the finite-element-method (FEM) high-frequency structure simulator (HFSS) from ANSYS and the time-domain-based Microwave Studio simulator from Computer Simulation Technology (CST).
The frequency range of the broken-heart-shaped microstrip patch antenna is just a shade beyond the range recognized as UWB by the IEEE, which is 3.1 to 10.6 GHz. Demand has been growing for UWB electronic systems in recent years because of their relative simplicity (and low cost) and their high-data-rate capabilities. One of the challenges facing UWB system designers has been the size of UWB antennas—microstrip patch antennas for UWB applications are typically large.
The UWB antenna consists of a broken-heart-shaped patch with slotted ground plane. The microstrip patch is printed onto one side of the substrate. The substrate has a dielectric constant of 4.6 in the z-direction, with a loss tangent of 0.02.
To determine an optimum antenna configuration, four designs with the same outer dimensions were simulated and compared: circle shape, dumb-bell shape, heart shape, and broken-heart shape. The circle-shaped and dumb-bell-shaped antennas fail to cover the full UWB frequency range. The heart-shaped patch antenna covers the range from 2.90 to 10.50 GHz with two resonances at 3.40 and 6.90 GHz, but the broken-heart-shaped patch covers from 3.0 to 10.80 GHz with three resonances at 3.5, 7.0, and 9.5 GHz for the most complete frequency coverage of the different antenna configurations.
The broken-heart-shaped microstrip patch antenna was fabricated on commercial printed-circuit-board (PCB) material and characterized with a commercial microwave vector network analyzer (VNA). Measurements closely approached the predictions/simulations by the different software simulation programs.
The antenna has high input impedance below 2.9 GHz, meaning that current flow is interrupted at those frequencies. The real part of the input impedance is close to about 50 Ω throughout the bandwidth from 2.90 to 10.70 GHz. Thus, the design is an excellent candidate for a variety of different UWB applications while maintaining relatively small dimensions for its wide bandwidth with high gain and 86.6% UWB efficiency.
See “The Broken-Heart Printed Antenna for Ultrawideband Applications,” IEEE Antennas & Propagation Magazine, Vol. 60, No. 6, December 2018, pp. 45-61.