Search

Two-antenna systems for wideband amplitude-only direction finding (AODF) are demonstrated. Tapered slot antennas (TSAs) are integrated into two flush-mounted configurations to achieve desired performance over 18–45 GHz range. The first system is made of two TSA elements embedded inside an absorptive cavity. Fed by a 90° hybrid, this phased-array topology supports two squinted beams required for AODF. The second system is made of two identical TSA elements physically squinted off boresight to produce required beams without beamforming. This allows each TSA element to be embedded in a separate nonabsorptive and shaped cavity for much improved AODF including widened field of view, higher gain, better dynamic range, and eliminated sidelobes. The system implications for the use of the proposed antenna front ends in terms of bearing errors to amplitude imbalances and receiver noise are also discussed. The construction of both antenna systems is disclosed, and experimental results closely resembling and therefore verifying theory are obtained.

An approach for assessing the quality of antenna patterns for wideband unambiguous amplitude-only direction finding (AODF) at millimeter waves with two squinted antennas is discussed. Several parameter criteria are proposed to evaluate the radiation performance of the standalone antenna element in terms of pattern smoothness and beamwidth stability with frequency. A computational analysis of these criteria is conducted to identify the needed parameters of a considered (horn) antenna suitable for resilient AODF performance. For experimental demonstration, an AODF horn antenna subsystem is constructed as a single all-metal three-dimensional (3-D) printed structure with standard waveguide feed ports. The passive front end performs as expected, where a maximum error of ±1°/dB is maintained across a scanning field of view (FoV) from −20° to +20° over the entire W-band. The proposed design methodology can be generalized to E-plane patterns and different antenna types as suitable for a specific application.

Two passive approaches for improving the isolation between flush-mounted transmitting (TX) and receiving (RX) antennas over 45–110 GHz are investigated. Both configurations exploit a reactive impedance surface (RIS) that suppresses TM polarized surface waves propagating on the ground plane between the TX and RX antennas. Quarter-wavelength corrugated one-dimensional (1-D) RIS is shown to improve isolation by ∼20 dB in an octave bandwidth (45–90 GHz), whereas concentric corrugations around the antennas improve isolation over the same bandwidth with better antenna radiation characteristics at the low end. On the other hand, an isolation improvement of ∼15 dB over the entire bandwidth is obtained with an array of grounded circular patches 2-D RIS. Computational studies are validated with measurements of quad-ridge horns with 3-D printed corrugations and printed circuit board 2-D RIS patches.

A 45–110-GHz double-ridge waveguide, denoted by WRD45110, is designed, fabricated, and tested. A detailed parametric study is carried out to develop a cross section with in-band attenuation for the straight line below 0.06 dB/cm and group delay below 0.06 ns/cm. Ridges are rounded so that the theoretical peak power handling is above 400 W. For practical characterization, various straight lines are built with the direct metal laser sintering (DMLS) 3-D printing process in aluminum and stainless steel. Precision, repeatability, mechanical strength, and electrical performance are then evaluated. A 90° twist, a 90° E-bend, a 90° H-bend, and an open termination load are also developed, 3-D printed, and measured. Good performance of all lines and components and ability to cascade functional pieces are demonstrated.

A square horn antenna with rotationally-stable radiation patterns that are also nearly invariant with frequency across the entire W band (75–110 GHz) is demonstrated. The flaring is designed such that the horn can support two perpendicular linear polarisations with very similar radiation patterns. The antenna is fabricated in two ways; by assembling two computer numerical control (CNC) machined split blocks, and by metallic 3D printing using direct metal laser sintering (DMLS). All fabricated antennas (one CNC aluminium, one DMLS aluminium, and one DMLS stainless steel) have similar performances that agree well with theory. Effect of surface roughness with the DMLS antennas is found to be electrically insignificant which is desired for fast prototyping and many current and emerging applications.

A quad-ridge horn antenna with stabilized gain and minimum difference between E- and H-plane half-power beamwidths (HPBWs) is demonstrated for operation over 45–110 GHz bandwidth. Multistep flaring and corrugations on a finite ground plane are applied to obtain stable radiation patterns with 16-dBi minimum gain over the entire range. The computational studies are validated through measurements of a 3-D printed prototype using the direct metal laser sintering (DMLS) process. Accurate fabrication with achieved surface roughness of $ of the fabricated antenna is verified with digital microscope. The obtained gain variation, VSWR, and HPBW variation with rotation and over 45–110 GHz bandwidth are below 1.7 dB, 1.7:1, and 9°, respectively. This work demonstrates that the DMLS is a viable fabrication process for wideband horn antennas at millimeter-wave frequencies.

A method to reduce RF leakage in split-block fabricated metallic ridged waveguide is presented. By placing a pin wall into the split-block seam, RF leakage and detrimental performance spikes are significantly reduced. Three different split-block double-ridge waveguide components of varying design complexity operating over 18–45-GHz bandwidth are fabricated and measured. It is shown that the addition of the pin wall improves the performance of each component such that results correlate well to simulated models with no split.

The magnetic current in an annular slot is used to enhance the impedance bandwidth of a monopole and preserve consistent radiation patterns from $ {K}$ -band through ${V}$ -band. The equivalent circuit models of monopole, annular slot, and their combination are derived to aid the RF system analysis with this antenna, herein referred to as a combined annular slot-monopole antenna. The proposed antenna is designed using full-wave and circuit simulations and the theory is experimentally validated. The measured VSWR is below 2 from 17.9 to 50 GHz. A consistent far-field characterized with monopole-like E-plane pattern, flat gain around 5.5±1 dBi, and good omnidirectionality (

The analysis and design of a wideband ‘Dewey’ curved-aperture horn antenna, designed to cover 75–110 GHz is presented. The development process features a fitness metric used to minimize radiation pattern variance. The main objective is to achieve H - plane radiation pattern invariance over the active bandwidth. Design data is favorably compared with measurements to fully validate the proposed antenna.

A suit of enabling passive components covering entire V-and W-bands, i.e. 45–110 GHz, is built for the support of future RF repeater research and development efforts. Concerns such as loss, power handling, dispersion, and singlemode bandwidth are considered to design a custom double-ridge waveguide and components including antennas, bends, twists, dividers, hybrids, couplers, filters, and decoupling surfaces, just to name a few. Results show that the developed technology can pave the way for efficient, low-cost integrated wideband or multiband millimeter wave systems.

This paper presents the design, fabrication, and performance of a W-band amplitude-only azimuthal direction finding antenna subsystem, designed to cover 75–110 GHz. The design utilizes curved-aperture pyramidal horn antennas to achieve near frequency independent radiation patterns over the band of interest, and 2-element linear arrays to increase receiver detection range. Two arrays are squinted apart by 30° to realize a high slope and near monopulse direction finding function.

We investigate the impact of placing a thin flat radome in front of an amplitude-only direction finding (AODF) antenna system. The considered system consists of two identical Ka-band, air-filled horn antennas squinted off boresight by 30° for direction finding (DF) error within ±0.82 °/dB over a field-of-view (FoV) from −20° to +20°. Computational results with various radome materials, thicknesses, and placements indicate that it is possible to maintain excellent DF performance if radome is properly designed and located.

We develop a high-gain antenna with wideband operation and compact size by placing a small dielectric superstrate (puck) in front of the feeding antenna. The antenna performance is a combination of the leaky-wave effect, naturally existing in this type of antennas, and the edge diffraction effect occurring at the puck perimeter. Compared to the typical resonant cavity antenna utilizing a large superstrate, the proposed puck antenna has nearly four times enhanced performance (gain-bandwidth combination) while using a square puck of side slightly smaller than two wavelengths (at the design frequency). Further enhancement is achieved by making the puck circular in shape in order to add the diffracted fields in phase. The study is conducted through full-wave simulations and validated through measurements in the $Ku$ band. The effect of puck misalignment is then discussed as a potential practical issue. Last, the ground plane is optimized for maximum antenna performance and relatively acceptable values of aperture efficiency (up to 51%).

A compact four-step 90-degree waveguide twist is designed for operation over the full W- band. The waveguide cross section is modified from the conventional sharp-corners rectangle to comply with the fabrication constraints. The designed twist is fabricated by two processes; CNC machining of the four steps then assembling, and 3D printing through direct metal laser sintering (DMLS). Both of the realized twists measure better performance than that of the commercially-available longer and more expensive twists. Moreover, they are better suited for integrated systems and delicate machining restrictions in W band.

A six-layer dielectric rod antenna is designed for symmetric and stabilized wide-beam radiation from 4 to 40 GHz. The desired HE 11 mode is excited in the rod by means of a 50-Ω Vivaldi feeding within a compact overall antenna structure. The study shows that the antenna has symmetric patterns with VSWR below 2:1, efficiency above 75%, and E/H-plane 10-dB beamwidths over 100° over the examined frequency band.

Two passive techniques for improving the isolation between transmitting (TX) and receiving (RX) antennas in V/W-band repeaters are presented. Specifically, corrugations and 2-D array of grounded circular patches are designed to provide a reactive impedance surface (RIS) between the antennas. It is found, that both approaches enhance the isolation by ∼20 dB compared to the basic case when TX and RX antennas are recessed in a smooth, untreated ground plane. Computational studies are experimentally validated with 3D printed horns fed with a novel 45–110GHz ridge waveguide line.

A V-W band quad-ridge horn antenna with stabilized gain and minimum differential E-H plane half power beamwidth (HPBW) is discussed. Multi-step flaring and corrugations on a finite ground plane are applied to achieve required stable gain above 16 dBi from 45 to 110 GHz. The computational studies conducted in HFSS are verified with CST and it is demonstrated that the designed antenna achieves gain variation < 2 dB, VSWR < 2:1, difference in E-H plane HPBWs of < 10°, and acceptable patterns over the entire frequency band.

A horn antenna with stabilized radiation characteristics over the entire W-band (75–110 GHz) is used for amplitude-only direction finding. Two horns are squinted in H plane to produce a direction finding function that covers a maximum field-of-view (FOV) with minimum uncertainty (errors). Preliminary results show the system's capability to readily cover FOVs of up to 60° with errors less than ±3°.

A novel approach for constructing a low-cost transmission line by stacking machined printed circuit boards (PCBs) is proposed. The line mimics the fully enclosed rectangular coaxial line with over 75% air and, therefore, demonstrates a low-loss and low-dispersion performance. The approach is employed to design and fabricate a transmission line operating up to the Ka band with only 0.15 dB/cm maximum measured insertion loss at 40 GHz. This study demonstrates the suitability of the stacked PCBs for realization of wideband 3D transmission lines for centimeter-wave and millimeter-wave applications with much lower cost than the available microfabrication processes.

We present a simple method to design a resonant cavity antenna (RCA) that resonates in two bands by employing two dielectric superstrates of thicknesses and positions determined by a step-by-step, non-iterative process. The method models the RCA as two cavities, each corresponding to one operational band, which allows for a dynamic control of the separation between the bands. The antenna is analytically designed and performance is evaluated using a commercial software.

We propose a new type of resonant cavity antenna (RCA) that employs a small dielectric puck instead of the large dielectric superstrate layer used in the traditional RCA. The diameter of the puck is studied to determine its influence on the gain-bandwidth product (G·BW) of the RCA. Simulations of the waveguide-fed RCA demonstrate that the G·BW of the RCA with puck can be four times larger than that of the traditional RCA. Moreover, the antenna with puck is compact and can be easily fabricated, which makes it attractive for future high-frequency and very directive point-to-point communication links.

We present a novel technique to design a dual-band resonant cavity antenna that has only one dielectric superstrate. The technique is based on using a superstrate slab of high permittivity and a thickness of an integer number of half wavelengths. In representative examples, we use a ray-tracing theoretical model to study the dual-band behavior and explain it by observing how the reflection coefficient of the superstrate varies with frequency. The results are validated by simulation using commercial numerical electromagnetics software.

A cavity resonance antenna (CRA) with three dielectric superstrates is examined and its performance is compared to those of the single superstrate CRAs of the lowest two resonances. The broadside directivity, bandwidth, and directivity-bandwidth product of all three antennas are investigated. When compared to the single superstrate CRAs, an appropriately designed three superstrate CRA can enhance to the maximum directivity, the bandwidth, or both, a result that is reflected as more than 75% increase to the directivity-bandwidth product in some cases. Theoretical results are validated by simulation using commercial numerical electromagnetics software.

The ray-tracing method is applied to study the radiation of a cavity resonance antenna (CRA) with both single and multiple dielectric superstrate layers. The behavior of the broadside directivity is investigated by analyzing the reflection phase of the antenna superstrates. To enhance the bandwidth of the CRA and maintain its large broadside directivity, a multilayered superstrate of an increasing reflection phase with frequency is presented. When compared to the single-layered CRA, a bandwidth enhancement of more than 100% is attained using a multilayered CRA of three superstrate slabs. Theoretical results are validated by simulations using commercial numerical electromagnetics software.

This paper discusses the development of a dual, broadband antenna, designed to be used for a compact sensor with total size no more than one cubic centimeter (1 cm3). The antenna specifications require more than 100 MHz bandwidth at 2.4 GHz and more than 1 GHz bandwidth at frequencies higher than 6 GHz. The 2.4 GHz radiation is used for the downlink, control data reception, and the wideband radiation is used to support the high data rate transmission to the sensor reader (uplink). A novel folded dual monopole antenna is presented that meets the sensor requirements. It is printed on two faces of a one cubic centimeter box. On one side a “fat” monopole is implemented successfully for the wideband operation and on an adjacent side a folded monopole operates effectively at 2.4 GHz. Both monopoles use the same, common feed line. The sensor IC is embedded inside the 1 cm3 cube.