The theory, design, fabrication, and measurement of a new class of planar ultrawideband modular antenna (PUMA) arrays are presented. The proposed PUMA array class achieves twice the bandwidth (from 3:1 to 6:1) of the conventional shorted via-based PUMA without using an external matching network and while retaining convenient unbalanced feeding, manufacturing, and assembly characteristics. The chief enabling technical innovation hinges upon the reconfiguration of shorting vias into capacitively-loaded vias that simultaneously: 1) mitigate low-frequency bandwidth-limiting loop modes and 2) shift problematic common-mode resonances out-of-band. A simple theoretical model based on ridged waveguides is proposed that qualitatively and quantitatively explains this novel common-mode mitigation. An infinite array operating over 3.53–21.2 GHz (6:1) is designed to achieve active VSWR < {2, 2.5, 3.8} while scanning to {broadside, 45°, 60°}, respectively, without oversampling the aperture. D-plane cross-polarization is around {−15, −10} dB for {45°, 60°} scans with high efficiency, i.e., 0.5 dB co-polarized gain loss on average. A dual-polarized prototype 256-port (128 elements per polarization) array is fabricated and measured having good agreement with full-wave finite array simulations.

A New Class of Planar Ultrawideband Modular Antenna Arrays With Improved Bandwidth

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

Electric andmagnetic currents are essential to describe electromagnetic-stored energy, and the associated antenna Q and the partial directivity to antenna Q-ratio, D/Q, for arbitrarily shaped struc ...

https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2014.0897

Stored energies in electric and magnetic current densities for small antennas

Design of small antennas is challenging because fundamental physics limits the antennas performance. Physical bounds provide basic restrictions on the antenna performance solely expressed in the available antenna design space. These bounds offer antenna designers a priori information about the feasibility of antenna designs and a figure of merit for different antenna designs. Here, an overview of physical bounds on antennas and the development from circumscribing spheres to arbitrary shaped regions and embedded antennas are presented. The underlying assumptions for the methods based on circuit models, mode expansions, forward scattering, and current optimization are illustrated and their pros and cons are discussed. The physical bounds are compared with numerical data for several antennas. (Less)

/pdf/physical-bounds-of-antennas-483eq80v1p.pdf

Physical bounds of antennas

A bandwidth limit was recently developed for antenna arrays backed by a PEC ground plane, under pure TE or TM polarization . In this paper, we extend this result to account for simultaneous excitation of both TE and TM modes, yielding a more general bandwidth limit for lossless and reciprocal PEC-backed arrays (LRPBA) under arbitrary polarization. For a linearly polarized LRPBA, the result is a simple expression for the maximum realizable impedance bandwidth as a function of scan angle. For a circularly polarized LRPBA, there appears to be a fundamental trade-off between polarization purity and impedance bandwidth. Overall, the maximum possible impedance bandwidth of a LRPBA at broadside is twice that of the same array whose polarization is held constant over frequency.

Bandwidth Limits for Lossless, Reciprocal PEC-backed Arrays of Arbitrary Polarization

This letter defines a physical-bound-based array figure of merit for both single and multiband array antennas. It provides a measure to compare their performance with respect to return loss, bandwidth(s), thickness of the array over the ground plane, and scan range. The result is based on a sum-rule result of Rozanov-type for linear polarization. For single-band antennas, it extends an existing limit for a given fixed scan-angle to include the whole scan range of the array, as well as the unit-cell structure in the bound. The letter ends with an investigation of the array figure of merit for some wideband and/or wide-scan antennas with linear polarization. We find arrays with a figure of merit >0.6 that empirically defines high-performance antennas with respect to this measure.

Array Antenna Limitations

This letter defines a physical bound based array figure of merit that provides a tool to compare the performance of both single and multi-band array antennas with respect to return-loss, thickness of the array over the ground-plane, and scan-range. The result is based on a sum-rule result of Rozanov-type for linear polarization. For single-band antennas it extends an existing limit for a given fixed scan-angle to include the whole scan-range of the array, as well as the unit-cell structure in the bound. The letter ends with an investigation of the array figure of merit for some wideband and/or wide-scan antennas with linear polarization. We find arrays with a figure of merit >0.6 that empirically defines high-performance antennas with respect to this measure.

N. Hussain

Papers

Array Antenna Limitations

Array Antenna Limitations