Historically, Vivaldi arrays are known to suffer from high cross-polarization when scanning in the nonprincipal planes—a fault without a universal solution. In this paper, a solution to this issue is proposed in the form of a new Vivaldi-type array with low cross-polarization termed the Sliced Notch Antenna (SNA) array. For the first proof-of-concept demonstration, simulations and measurements are comparatively presented for two single-polarized $19 \times 19$ arrays—the proposed SNA and its Vivaldi counterpart—each operating over a 1.2–12 GHz (10:1) band. Both arrays are built using typical vertically integrated printed-circuit board cards, and are designed to exhibit VSWR $\theta \!=\!45 {^{\circ }}$ polarization purity improvement at the high frequency. Moreover, the SNA element also: 1) offers better suppression of classical Vivaldi E-plane scan blindnesses; 2) requires fewer plated through vias for stripline-based designs; and 3) allows relaxed adjacent element electrical contact requirements for dual-polarized arrangements.

A 1.2–12 GHz Sliced Notch Antenna Array

A modified broadband antipodal Vivaldi antenna for the operating frequency range of 6–18 GHz is presented. In order to eliminate diffraction from sharp ends, the corners of the patches are rounded. As a result, both the gain and directivity are improved. Moreover, one major addition that is done to the antenna is the background plane. The purpose of the backplane, which is made of metal, is to reflect any radiation going in a direction opposite to that of the required. This would then effectively increase the forward radiation, thus contributing to the gain of the antenna structure. In addition to be small in size, the designed antenna exhibits stable radiation patterns over the entire operating bandwidth, relatively high gain of 7–8.4 dB, and low cross-polarisation. A prototype of the modified antenna is fabricated and verified experimentally. The measured results are in reasonable agreement with the simulation data. Based on the obtained results, the designed antenna can be useful for broadband applications.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2015.0155

Wideband antipodal Vivaldi antenna with enhanced radiation parameters

This article introduces a millimeter-wave (mm-wave) multi-band transmit (Tx) phased-array design supp- orting the fifth-generation (5G) new radio frequency range 2 (NR FR2) bands. An eight-element phased-array module is presented employing two wideband 16–52 GHz <inline-formula> <tex-math notation="LaTeX">$4{\times }1$ </tex-math></inline-formula> Tx beamformer chips and tapered slot Vivaldi antenna array. The beamformer chips are designed in a SiGe BiCMOS process and flipped on a printed circuit board (PCB). The SiGe integrated circuit (IC) has four differential radio frequency (RF) beamforming channels each consisting of an active balun, analog adder-based phase shifter (PS), variable gain amplifier (VGA), and a two-stage class-AB power amplifier (PA). The RF input signal is distributed to the four channels using a compact Wilkinson network. The measured peak gain is 28.3 dB with 13.5–14.7 dBm output <inline-formula> <tex-math notation="LaTeX">$P_{1{\mathrm {dB}}}$ </tex-math></inline-formula> and 14–15.4 dBm <inline-formula> <tex-math notation="LaTeX">$P_{{\mathrm {sat}}}$ </tex-math></inline-formula> at 20–50 GHz. Each channel dissipates 250 mW from 2 V and 3-V supplies at <inline-formula> <tex-math notation="LaTeX">$P_{1\,{\mathrm{ dB}}}$ </tex-math></inline-formula>. The beamformer chip is tested using 64-QAM waveforms and achieves a data rate of 2.4 Gb/s at 5.2% rms EVM and 9.6-dBm average power. The eight-element phased-array module shows a broadband performance with excellent patterns and ±60° scanning capability and with a peak effective isotropic radiated power (EIRP) of 32–34 dBm at 19.5–51 GHz. At an EIRP of 21–22 dBm, 400-MHz 256-QAM 5G-NR compliant waveforms are transmitted with < 2.98% EVM demonstrating 5G NR FR2 operation. To the author’s knowledge, this work achieves the highest bandwidth phased array with a peak EIRP of 34 dBm enabling the construction of multi-standard/multi-band 5G phased-array systems.

A Multi-Band 16–52-GHz Transmit Phased Array Employing 4 × 1 Beamforming IC With 14–15.4-dBm Psat for 5G NR FR2 Operation

A novel wideband-connected parallel slot array for wide-angle scanning applications is proposed in this article. Different from conventional connected slot arrays, the proposed array consists of dual parallel slots, where the introduced parasitic slot acts as an additional series capacitor. The connected parallel slot array can realize low and moderate active input impedances and achieve wide bandwidth without using any complex balun. To improve the wide-angle impedance matching issue and avoid an increase in the array profile, a mixed periodic metallic strips layer with almost zero height and weight was adopted. The metallic strips layer can be regarded as a shunt capacitance between the array and free space. Additionally, equivalent circuit models were established to analyze the function of the introduced parasitic slot and metallic strips layer. The proposed connected parallel slot array achieves a concurrent bandwidth of approximately 69.2% (1.35–2.78 GHz), while covering a scanning area of ±60° in the E-, H-, and D-planes. The profile is only 0.088 $\lambda _{\mathrm {L}}$ , where $\lambda _{\mathrm {L}}$ is the wavelength of the lowest operation frequency in free space. Besides, low cross-polarization in principal planes, planar and simple structure, and light weight are also the merits of the proposed antenna array.

A Low-Profile Light-Weight Wideband Connected Parallel Slot Array for Wide-Angle Scanning

This article presents a dual-polarized Vivaldi array on a triangular lattice. The all-metal ultrawideband Vivaldi features offset radiator pairs that are precision-machined from aluminum stock as a modular tile, similar to earlier reports on more typical all-metal square-lattice Vivaldi arrays. The intent of this work is to validate the embedded element performance of the dual-polarized triangular-lattice Vivaldi, comparing one-to-one with results for a similarly sized dual-polarized all-metal Vivaldi array on a square (egg-crate) lattice, reported previously. The triangular-lattice Vivaldi array is optimally sampled for grating-lobe-free scans with a potential 15.5% reduction in element count compared to a corresponding optimally sampled square-lattice array of similar size. As such, the footprint of the manufactured triangular-lattice Vivaldi array is roughly 8% larger than the square-lattice array, yet has 7% fewer elements. Infinite array predictions are presented and shown to compare favorably with previous findings for the square-lattice Vivaldi array, noting minor performance compromises. Wideband and wide-scan simulations are validated with measurements of prototype hardware, demonstrating that embedded element performance of the triangular-lattice array correlates well with modeling predictions. All told, the triangular-lattice array has similar capability to the square-lattice Vivaldi array in a more efficiently sampled aperture.

Dual-Polarized Vivaldi Array on a Triangular Lattice

A triangular grid single polarized tapered-slot array antenna for radar applications is studied. Compared with a rectangular grid an equilateral triangular grid allows a larger unit cell without any onset of grating lobes. Since single polarized tapered-slots in triangular grids support guided modes, which cause scan blindness, the increase in unit cell size is smaller than the optimal 15%. The design presented in the paper is capable of scan angles out to 60° from broadside in the E and H planes. To improve the match over the radar band a local minimum in the active reflection coefficient is positioned at the most critical scan direction, resulting in a reflection coefficient that is less than -12 dB in the X-band. To reduce the radar cross section for the cross-polarization an absorbing layer is positioned above the ground plane, which affects some of the guided modes that lead to scan blindnesses. An experimental antenna with 16 × 16 elements was built, and it was found that the H-plane performance for large scan angles for the finite antenna deviates more than expected from the infinite array approximation. Otherwise both mutual coupling measurements and embedded element patterns agrees well with the numerical results.

A. Ellgardt

Papers

A Single Polarized Triangular Grid Tapered-Slot Array Antenna