Ultrawideband High-Gain Stacked Microstrip Antenna with Modified E-Shaped Active Exciter and Four Single-Sided Bowtie Passive Elements
Mikhail S. Shishkin
The article presents a method that allows for the high gain of a stacked microstrip antenna on an air substrate in an ultrawide frequency range. The method uses an active exciter in the form of a modified E-shaped patch, as well as four single-sided bowtie passive elements placed in the corners above the active one. The active element can match an antenna in an ultra-wide frequency range (up to 100%) with an impedance bandwidth matching of 10 dB or better, whereas passive elements are able to produce unidirectional radiation in the range of approximately 70-80% with a gain of more than 10 dBi. Based on the method under study, an ultrawideband antenna design was made which operates in a frequency band of 3,915 to 11,046 MHz (95.3%) with an impedance bandwidth matching of 10 dB and a bandwidth about 83% with |S11| ≤ -15 dB; the usable bandwidth with a gain of more than 10 dBi in the normal direction to the antenna plane with a cross-polar discrimination more than 55 dB is 77% (3,925-8,837 MHz). At frequencies below 4 GHz and above 9 GHz, the phase center shifts, and accordingly, the main lobe of the radiation pattern (radiation maximum) deflects. All antenna elements (one active and four passives) are made of sheet metal (e.g., stainless steel) and are connected to the conductive screen by steel or dielectric racks. The antenna dimensions are 1.05λmax × 1.2λmax × 0.1λmax (1.7λ0 × 1.9λ0 × 0.2λ0). Owing to its high performance, the antenna may be used as a measuring device in radio monitoring systems or in laboratories.
