John T. Logan

Simplified design of 6∶1 PUMA arrays

Advances in Planar Ultra-wideband Modular Antenna (PUMA) array architecture which have culminated into a 6:1 bandwidth design without the use of an external backplane matching network are presented. This paper will examine the additional bandwidth-enhancing operational principles of the proposed dual-polarized 6:1 PUMA array. A design and its respective full-wave simulations will then be presented, with results yielding a 6:1 bandwidth with VSWR <; 2 at broadside, VSWR <; 2.6 scanning out to θ = 45°, and a diagonal plane cross-polarization greater than 15 dB at θ = 45° for the majority of the band.

Planar Ultrawideband Modular Antenna (PUMA) arrays scalable to mm-waves

A new class of Planar Ultrawideband Modular Antenna (PUMA) arrays, the PUMAv3, is introduced. PUMAv3 is scalable to mm-wave frequencies (≈50 GHz) and improves bandwidth by 50% without the use of a matching network or external baluns. The enabling technical innovations include a new feeding mechanism that relies on capacitively loaded shorting vias and an alteration on the superstrate loading scheme. Infinite array full-wave simulations of a dual-polarized PUMAv3 suggest 10.6-47.6 GHz (4.5:1) operation with good VSWR levels out to θ = 45°, high port isolation and low cross-polarization.

On the design of 6∶1 mm-wave PUMA arrays

A matching network is integrated into the latest version of the PUMA array (presented in a fellow paper [1]) to increase the bandwidth. The PUMAv3.2 is scalable to mm-wave frequencies (≈45 GHz) and increases bandwidth from 4.5:1 to 6:1. We investigate the difficulties and possible solutions associated with integrated matching network PUMA designs. Part of the enabling technical aspects is a capacitively loaded coplanar waveguide section etched into the ground plane that connects to a stripline matching network at the backplane. Infinite array full-wave simulations of a dual-polarized PUMAv3.2 suggest 7.5-45 GHz (6:1) operation with good VSWR levels out to θ = 45° and a peak of 8.5 dB cross-pol. in certain diagonal cuts.

Dual-polarized sliced notch array — ultra-wideband flares with exceptional polarization control

Traditional flared notch arrays for ultra-wideband phased-array applications are known for excellent matching but have very poor polarization control in the diagonal scan plane. The sliced notch array is a variant of the flared notch that by contrast has excellent cross-polarization performance at all scan angles and frequencies for the same LxWxH size array. In this paper we report the first experimental results comparing a traditional dual-polarized flared notch array with a sliced notch array of the same element spacing, aperture height and footprint. Both arrays operate over the same frequency range, roughly 2GHz-21GHz (approx. 10:1 bandwidth) with comparable gain. For a 60-degree scan in all planes, the traditional and sliced notch arrays achieve VSWR < 3.0 and VSWR < 2.2, respectively. Near the high frequency limit, for a 45-degree scan in the diagonal plane the traditional flared notch exhibits a complete polarization reversal (cross-pol. 20dB higher than co-pol.), whereas the sliced notch array maintains closer to 20dB of cross-pol. rejection. Measured results are presented that document significant polarization improvements over all scan angles and frequencies.

A 6:1 bandwidth PUMA array at 7mm scale

A Planar Ultra-Wideband Modular Antenna (PUMA) array with 7mm element spacing is presented that operates over roughly 3.5GHz to 21GHz, validating the first PUMA with a 6:1 operational bandwidth. The design consists mainly of plated through vias on Rogers 5880LZ substrate with Rogers 3000-class materials integrated as a radome superstrate. The aperture is less than 0.5 wavelengths thick at the highest frequency of operation. Scan VSWR performance is good, with VSWR < 2.5 for 45-degree scans in all planes, VSWR < 3.8 for 60-degree scans in all planes and over all frequencies. An all-metal flared notch array of the same element spacing and footprint is presented for performance comparison. It is shown that the PUMA has significantly-better polarization patterns than legacy ultra-wideband flared notch arrays over all frequency and scan space. Measured results are presented.

A low cross-polarization decade-bandwidth Vivaldi array

A single-polarized, decade-bandwidth Vivaldi array with low cross-polarization is proposed. The array, termed the Sliced Notch Antenna (SNA) Array, exhibits the wideband impedance performance of Vivaldi arrays, yet it readily over-comes polarization purity degradation while scanned in the non-principal planes. The critical enabling technical innovation is the control of vertical surface current radiation through innovative discontinuities along the flared fins that are designed for decade-bandwidth impedance performance. The concept and performance are demonstrated through infinite array HFSS simulations and finite array Domain Decomposition Finite Element Method (DD-FEM) numerical results of a 19×19 SNA/Vivaldi array PCB-based prototypes.

Low Cross-Polarization Vivaldi Arrays

This paper introduces a Vivaldi-type ultra-wideband antenna array with low cross-polarization, termed the Sliced Notch Antenna (SNA) array. High cross-polarization when scanning in the non-principal planes has long been a problem in Vivaldi arrays without a universal solution. In this paper, we shed light on the root cause of this long-standing issue, clarifying that a high ratio of vertical-to-horizontal current potentials along the upper radiator fin is primarily responsible for elevated cross-polarization (and not strictly the element profile). This finding therein motivates the main technical innovation in the present work—a simple reconfiguration of the upper Vivaldi fin into a series of coupled conductor segments to effectively control the aforementioned current ratio for significant reductions in cross-polarization, without reducing element profile or considerably hindering the excellent match and radiation efficiency of the original Vivaldi. Theory and design methodology for the SNA array are formulated, and followed by a concise set of design guidelines that are applied to reconfigure a representative 10:1 Vivaldi element into an SNA for practical reference, exhibiting a 20 dB reduction in peak cross-polarization ratio. This paper considers the case of single-polarized arrays as a first introduction to the SNA, though the method has been verified to work equally well (if not better) in dual-polarized arrays.

Decade-bandwidth low cross-polarization UWB array

The proposed Sliced Notch Antenna (SNA) array fixes the longstanding problem of high cross-polarization radiation in Vivaldi arrays while maintaining their excellent wideband wide-scan impedance performance with a simple reconfiguration of the Vivaldi fins. The enabling technical innovation is the introduction of discontinuities at the upper region of the flared fins that control the ratio of vertical-to-horizontal current density, without introducing sizable reflections. Measurements and simulations suggest a 10:1 (1.2-12 GHz) SNA array operation with good scanning VSWR out to 45°, and about 15 dB polarization purity improvement over a well-designed Vivaldi counterpart.

Opportunities and advances in ultra-wideband electronically scanned arrays

This paper discusses bandwidth and polarization challenges in modern dual-polarized ultra-wideband (UWB) electronically scanned array (ESA) aperture design and two recent solution advances aiming to remedy such issues: a 6:1 Planar Ultrawideband Modular Antenna (PUMA) array and a 10:1 Sliced Notch Antenna (SNA) array. The proposed arrays enable wide bandwidth, low cross-polarization, and high efficiency from both low-profile and high-profile array research directions to appeal to a wider variety of applications and design embodiments. The proposed UWB-ESAs are analyzed alongside a conventional 10:1 all-metal Vivaldi array to shed light upon modern design trends and implications.

Low cross-polarization ultra-wideband arrays (student submission)

This work presents the development of a low cross-polarization ultra-wideband end-fire notch array element, termed the Sliced Notch Antenna (SNA). The proposed element topology solves the long-standing problem of polarization purity degradation in typical end-fire notch arrays (Vivaldi arrays) when scanned in the non-principal planes by re-configuring the high-profile continuous metal Vivaldi fin into disconnected and vertically stacked metal strips. Single-polarized PCB-based SNA arrays and their Vivaldi array counterparts are designed, fabricated, and measured to comparitively evaluate performance. Dual-polarized implementations of both arrays are alike in that they operate over a 10:1 (1.2–12 GHz) bandwidth with VSWR<2.2 out to θo = 60° scans as infinite arrays; however simulations suggest the proposed SNA array offers around 20 dB polarization isolation improvement near the highest frequency for D-plane scans out to θo = {45, 60}°. The technical approach will be expanded further in the presentation and complete measurement results of 19×19 array prototypes will be provided at the conference.