Dual-Slot Cavity Antenna for mm-Wave Beamforming Array

Abstract

A cavity-fed, dual-slot element and its 4-element linear array configurations for beam-steering applications at 28 GHz are described. The element cavity is formed from rectangular substrate integrated waveguide (SIW), perturbed at one of its corners to excite dual slots for increasing the impedance bandwidth. With a mobile terminal in mind, we look to both classical array principles and to the available theories for finite arrays with mutual coupling, to help guide the design. The impact of the finite ground-plane required to support the slot elements and array is investigated by simulation, including the impact on the patterns of using a cellphone chassis as a platform. A chassis-born 4-element (8 slots) configuration, suitable for beamforming in 28 GHz 5G networks is demonstrated for both linear polarizations. The simulation results are supported by pattern measurements of prototypes, a challenging task at 28 GHz. 48 C. BEAM FORMING ARRAYS 49 Recent designs for multiple cavity-fed slot antennas for 50 beamforming are now summarized. In [7], orthogonally 51 polarized, 2-element arrays at 2.5 GHz were realized using 52 orthogonally oriented slots on adjacent cavities arranged as a 53 VOLUME 10, 2022 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ From Figure 10(a), for a 4-element array of isotropic 512 elements, the array antenna directivity in a hemisphere has 513 a maximum of 10.7 dBi for an element spacing of 0.8λ 0 . 514 The array action adds 7.7 dB to the hemispheric element 515 directivity of 3 dBi. For the 2-element array, this spacing for 516 maximum directivity is 0.7λ 0 . For this isotropic element case, 517 only the array factor governs the optimum spacings. But for 518 directive elements, it is perhaps not widely understood that 519 the element pattern, featured in (7), also impacts the optimum 520 element spacing for maximum broadside directivity, meaning 521 that the array directivity cannot be separated from the element 522 directivity. 523 For a directive element pattern model using exponents n = 524 m =1, the maximum array antenna directivity of 14.5 dBi is 525 for a spacing of 0.9 λ 0 . This changing spacing for maximum 526 array antenna directivity is from the element patterns acting 527 to suppress grating lobes. The 4-element array action for this 528 spacing adds 6.7 dB to the element directivity of 7.8 dBi.

mmWave Yagi-Uda Element and Array on Liquid Crystal Polymer for 5G

“…The array antenna pattern was instead found from the array pattern formulation in [31] which contains the S-parameters and the embedded element patterns (simulated) with the remaining elements open circuited. (We have found this more recent formulation to be accurate [32].) For the without mutual coupling case in Fig.…”