Tomislav Debogovic

Low Loss MEMS-Reconfigurable 1-Bit Reflectarray Cell With Dual-Linear Polarization

We present a X-band 1-bit reconfigurable reflectarray (RRA) cell capable of independent reflection phase control of each linear component of a dual-polarized wave. It presents the lowest loss ever reported in an operational RRA cell at microwave frequencies, thanks to particular design considerations and implementation in a monolithic micro-electromechanical systems (MEMS) process. The average reflection loss, including oblique incidence up to θ = 40°, is below 0.6 dB at the operating frequency. Low phase error and loss are preserved in a 12.5% bandwidth. Measurements demonstrate the viability of the concept as well as very good agreement between simulated and measured results.

MEMS-Reconfigurable Metamaterials and Antenna Applications

This paper reviews some of our contributions to reconfigurable metamaterials, where dynamic control is enabled by microelectromechanical systems (MEMS) technology. First, we show reconfigurable composite right-/left-handed transmission lines (CRLH-TLs) having state of the art phase velocity variation and loss, thereby enabling efficient reconfigurable phase shifters and leaky-wave antennas (LWA). Second, we present very low loss metasurface designs with reconfigurable reflection properties, applicable in reflectarrays and partially reflective surface (PRS) antennas. All the presented devices have been fabricated and experimentally validated. They operate in X- and Ku-bands.

Broadband Fabry-Pérot antenna with non-Foster metasurface - how to test the basic idea?

Recently, an idea of a broadband Fabry-Perot (FT) antenna, ground plane of which is replaced by a non-Foster surface has been introduced theoretically. In this contribution, a basic concept of FP antenna with non-Foster metasurface is renewed together Kith a brief analysts of stability issues. Finally, a simple ID hardware demonstrator, intended for experimental verification of the basic idea, is proposed.

Ramsey-mode Rb cell clock demonstration with a 3D-printed microwave cavity

We demonstrate operation of a Ramey-mode Rb vapor-cell atomic clock based on a microwave cavity realized by additive manufacturing (3D-printing). The cavity design is based on a loop-gap approach and its critical electrode structure is realized in one monolithic piece by stereolithography of a polymer which simplifies the assembly of the cavity. The microwave magnetic field in the cavity shows excellent uniformity and high homogeneity across the Rb cell, which results in high-contrast Ramsey fringes observed on the clock transition. A measured clock stability of 2.2∗10−13 τ−1/2 demonstrates the feasibility of the approach. We discuss aging studies performed on 3D-printed test samples that are of relevance for long-term operation of the clock.

Study of additive manufactured microwave cavities for pulsed optically pumped atomic clock applications

Additive manufacturing (AM) of passive microwave components is of high interest for the cost-effective and rapid prototyping or manufacture of devices with complex geometries. Here, we present an experimental study on the properties of recently demonstrated microwave resonator cavities manufactured by AM, in view of their applications to high-performance compact atomic clocks. The microwave cavities employ a loop-gap geometry using six electrodes. The critical electrode structures were manufactured monolithically using two different approaches: Stereolithography (SLA) of a polymer followed by metal coating and Selective Laser Melting (SLM) of aluminum. The tested microwave cavities show the desired TE011-like resonant mode at the Rb clock frequency of ≈6.835 GHz, with a microwave magnetic field highly parallel to the quantization axis across the vapor cell. When operated in an atomic clock setup, the measured atomic Rabi oscillations are comparable to those observed for conventionally manufactured cavitie...

3D printed feed-chain and antenna components

This paper presents a set of additive manufactured (AM) monolithic waveguide-based feed-chain and antenna components, namely a Ku-band diplexer, a Ka-band dual-polarized directional antenna and W-band straight waveguides. These components provide representative examples of the current capabilities of AM technologies. Examples are provided over a large frequency spectrum and for diverse applications. Good performance and agreement between simulation and measurement results validate the presented designs and showcase the achievable performance of this new manufacturing technology.

Mm-wave antennas and components: Profiting from 3D-printing

The goal of this manuscript is to show the potential of additive manufacturing (AM) to produce cost-effective high-performance passive mm-wave components and antennas. We focus on the particular AM technique developed by SWISSto12 based on the so called Stereolithography (SLA), which consists on the 3D-printing of a skeleton of the component using a non-conductive polymer. Chemical copper plating is then applied in order to make all component surfaces RF-conductive. One of the most relevant advantages associated to this approach stems from its ability to produce low-weight monolithic devices. Two 3D-printed RF-devices operating at mm-waves are here presented: a Ka-band radiating element and a V-band orthomode-transducer. Both devices have been firstly designed using full-wave solvers, then manufactured and finally validated through measurements.

Low-profile tunable radiator for small satellite application

A tunable radiator for space application has been developed to meet stringent requirements in terms of electrical and environmental specifications but also low mass, simple manufacturing and low cost. The element is based on the folded planar inverted F-antenna, with size of one quarter of wavelength. It is mechanically tunable to adjust input impedance for any various positions on the satellite body and possible obstacles and protrusions. Results in terms of radiation pattern, S parameters, shock and vibration tests are presented. The antenna operates in ultra-high frequency band (400 MHz) in linear polarization. It has been designed to act as the basic element for miniaturized multi-function antenna systems on board of small satellites that can operate in three different radiating modes and in both left and right hand circular polarizations.