Abstract
This paper reports on the design and practical validation of monopole antenna arrays with reduced half-power beamwidth (HPBW) variation in a bandwidth (BW) greater than one octave of the RF spectrum. The HPBW variation is reduced by feeding the antenna elements with frequency-dependent feed networks. The feed networks are designed in such a way that the element power is gradually shifted from the outer elements at low frequencies to the inner elements at high frequencies. The operating principles of the proposed concept are explored through simulated examples of four-element arrays made of isotropic elements and then realistic monopole elements. Scalability of the concept to eight-element arrays is also explored using ideal simulations. For practical validation purposes, a four-element monopole antenna array and its corresponding feed network are designed and measured. The prototype resulted in a HPBW variation of 78% in a 2.6:1 BW, which is significantly reduced compared to the uniformly fed array, having a 216% variation.
Highlights
Next-generation radar, spectrum sensing, and wideband instrumentation systems are increasingly calling for broadband antennas that can cover multiple octaves of the spectrum [1], [2]
Despite the need for frequency-independent half-power beamwidth (HPBW), most of the research has been focusing on widening the antenna bandwidth (BW) in terms of input reflection or other radiation pattern characteristics such as gain, side-lobe level (SLL), and/or the direction of the beam
Considering the limitations, this paper presents a new class omnidirectional linear antenna arrays with reduced HPBW in beyond one octave of BW
Summary
Next-generation radar, spectrum sensing, and wideband instrumentation systems are increasingly calling for broadband antennas that can cover multiple octaves of the spectrum [1], [2]. Despite the need for frequency-independent HPBWs, most of the research has been focusing on widening the antenna bandwidth (BW) in terms of input reflection or other radiation pattern characteristics such as gain, side-lobe level (SLL), and/or the direction of the beam. The design methods in [7]-[10] proposed to feed sets of antenna elements varying amounts of power throughout the frequency range. Their practical implementation requires two separate PCB boards connected through cables, leading to a large size. The array displays a HPBW variation of only 23%, but it exhibits high SLLs (up to -6 dBc) and its complex network is manufactured on a multi-layer board.
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