James B. West

Fabrication and measurement of a large, monolithic, PCB-based AESA

This paper discusses a fabrication approach and experimental validation of a very large, planar active electronically scanned array (AESA). The planar AESA architecture employs a monolithic printed circuit board (PCB) with 768 active antenna elements at X-Band. Manufacturing physically large arrays with high element counts is discussed in relation to construction, assembly and yield considerations. Measured active array patterns of the ESA are also presented.

A SiGe-based Ku-band digital beamforming array for high speed on-the-move comm/radar system

A digital beamforming (DBF) prototype that uses compact and low cost Balanced Antipodal Vivaldi Antenna (BAVA) array and SiGe based-receiver is presented. An example is given for a Ku-band DBF system that demonstrates simultaneous reception of two or more full motion videos in a portable device.

Broadband bowtie-shaped current sheet antenna array

In this paper, the concept of a current sheet array (CSA) is expanded to design a broadband bowtie-shaped antenna array. The present approach has the potential to achieve a 7∶1 bandwidth over the VHF and UHF frequency bands with wide-angle beam. A 3 by 3 array of overlapping bowtie-shaped elements, with center feeding, was simulated. Printing was carried out on both faces of the dielectric slab and kept at a defined distance from the ground plane. A selected design was fabricated and tested experimentally to verify the simulated results for concept validation.

Measured Results of a Dual-Band Dual-Mode Millimeter Wave Analog EMXT Waveguide Phase Shifter Electronically Scanned Antenna (ESA)

A proof-of-concept dual-band dual-mode 25/44-GHz electronically scanned array (ESA) is realized using electromagnetic crystal (EMXT) waveguide sidewalls developed at the Rockwell Scientific Company (RSC) and Rockwell Collins, Inc. (RCI). A 15-element one-dimensional (1-D) linear array was tested at the RCI near field antenna range to show frequency independence and beam steering capability. The results of these tests are presented herein.

Charateristics of decade-bandwidth, Balanced Antipodal Vivaldi Antenna (BAVA) phased arrays with time-delay beamformer systems

The first part of this paper presents measured performance of the Balanced Antipodal Vivaldi Antenna (BAVA) with U-shaped metallic channels. This new BAVA array is dual polarized with decade bandwidth and wide scan volume. Its depth is half-wavelength at the highest frequency of operation. It can be constructed as modular individual BAVA elements or as a subarray with integrated transmitter / receiver (T/R) modules. This is a unique feature that reduces manufacturing complexity and the cost of field repair. The second part of this paper overviews performance of the BAVA array scanned at wide scan angles using AFRLs Transformational Element Level Array (TELA) Time-Delay Units between 2 GHz to 8 GHz and using fixed delay lines between 2 GHz to 18 GHz. The authors offer guidelines for minimum aperture size to realize decade bandwidth beam scan performance without beam squinting at the lower end of the frequency band.

Electromagnetic bandgap waveguide (EBG) phase shifters for low cost electronically scanned antennas (ESA)

Tunable electromagnetic bandgap (EBG) structures are used as variable surface impedance in the sidewall of waveguides to provide three generations of agile analog phase shifters for low cost ESA applications. A design methodology is discussed using a periodic unit cell approach. Three unique millimeter wave varactor diodes (heterojunction barrier varactor, Schottky varactors and flip chip Schottky varactor diode) have been developed. They have been introduced in monolithic form for the first two-generations and flipchip varactors for the last generation of EBG phase shifters. Results from each generation are reported with a phase shift of 36 to 16.8 deg/mm and the lowest insertion loss of 0.3 dB/mm at 38 GHz. A surface impedance model predicts the increase in the inductance/capacitance ratio of the unit cell components provides the lowest insertion loss. This is validated from the measured results from the three generations of the phase shifter circuits. Our results indicate that the approach of the electronically tuned EBG waveguide phase shifters could provide the low cost-high performance components for an ESA architecture without the need for TR modules.

Limitations of AESA's on monopulse beamforming

This paper discusses the limitations of controlling sidelobes with Monopulse Beamforming Networks in Active Electronically Scanned Antenna Arrays (AESAs). Uniform, Taylor, split Taylor and Bayliss amplitude weightings are presented from a system level perspective, when balancing the need for sidelobe control versus Size, Weight, Power and Cost (SWAP-C).

Low Profile, Frequency Scanned Weather Radar Waveguide Feed Manifold

In this paper, a novel approach to achieving a low profile, low loss feed manifold for center-fed frequency scanned radar systems has been presented. Inclusion of a reactive buffering region, allowing independent control of the slot in each waveguide, has been shown to increase degrees of freedom in design efforts and decrease mechanical tolerance requirements, thus permitting the use of standard low cost machining practices