Wide-Angle Radome Design for Low-Cost Additive Manufacturing

Abstract

The radome, a portmanteau of the words radar and dome, is a protective dielectric cover to protect a radar from its surrounding environment. The surrounding
environment can be rain, wind, sand, dust and whatever else that might harm
the radar. Radomes come in many different shapes, materials and thicknesses,
where each of these parameters are decided based on the need for the given radar
application. The challenge is that the protective radome decreases transmission
and increases reflection of the electromagnetic wave; especially for larger angles of
incidence which limits the effective field-of-view.
In this project we present methods to more easily design and optimize multilayered radome structures that decrease reflections and increase transmission for
a larger range of angles of incidence. Our method is to combine transmission line
calculations and optimization algorithms with finite element method simulations
software, where the transmission line calculations can considerably speed up and
simplify an initial design. The optimization is performed for all angles of incidence
of interest simultaneously, as well as the possibility to optimize for both transverse
electric and transverse magnetic polarization. The design method can be used with
any material and at frequencies for mmWave applications to achieve a goal of designing radomes that have reflectance below −25 dB up to 50◦ angles of incidence.
In our thesis we found, for flat multilayer radome structures, that the transmission
line calculations are very consistent with the finite element method simulations.
Furthermore, measurements of prototype radomes have been performed in order
to validate the simulated structures and the viability of the design procedure.

Popular Abstract (Swedish)

En radar använder elektromagnetiska vågor för att kunna skicka och motta signaler. Precis på samma sätt som att våra öron, ögon och tungor är mottagare
och vår röst och vårt kroppsspråk är sändare av signaler till världen omkring oss.
För både människan och för radarn så behövs det skydd mot omgivningen. Till
exempel, har våra ögon ögonlock och vår röst är dold inne i halsen. Utan ögonlock
skulle ögonen torka ut och potentiellt bli skadade av dammpartiklar. På samma
sätt behöver de känsliga antennerna, som fungerar som mottagare och sändare
av information, också ett visst skydd från till exempel vatten, damm, vind och
även fåglar [1]. Det är här radomen, som är en kombination av de engelska orden
radar och dome, kommer in i bilden. Radomen har den enkla, men mycket viktiga,
uppgiften att skydda radarn. Men radomen måste vara så transparent som möjligt
för de elektromagnetiska vågorna, samtidigt som den måste vara tillräckligt robust
för att skydda radarn. Detta är en svår ge och ta balans som en radomdesigner
behöver ha i åtanke. Utvecklingen och de bredare användningsområden av radar,
inom till exempel säkerhetsövervakning samt bilindustrin, har ökat dramatiskt
sedan andra världskriget [2]. Radar har blivit vardagliga produkter, billigare och
används idag för mycket kortare avstånd. Av den anledningen har behovet för
att radarn kan ”se” för bredare vinklar ökat. Precis på samma sätt som att man
kommer se fler reflektioner på ett fönster när ljuset träffar vid vissa vinklar, kommer en radar också uppleva reflektioner vid vissa vinklar. Under detta projekt
har vi utvecklat generella designmetoder för att minska dessa reflektioner för ett
brett vinkelintervall. Vårt fokus har varit på så kallade sandwich-radomer, som
är precis som namnet antyder, en radom med flera lager av olika material. Detta
betyder att en radomdesigner, genom att använda dessa metoder, lättare kan designa och optimera en radom for breda vinklar. Det har varit särskilt intressant
att med hjälp av vår föreslagna metod kan en initial, relativt enkel och potentiellt
billig design med låga reflektioner för breda vinkelintervall beräknas utan behov
av långsam och beräkningsintensiv simuleringsprogramvara.

Popular Abstract

A radar utilizes electromagnetic waves to send and sense signals. Exactly in the
same way as our ears, eyes and tongue are sensors and our voice and body language
are transmitters to the outside world. In both the human case and the radar
case, the essential sensory system needs protection from the environment around
us. For example, our eyes have eyelids and our vocal cord is hidden inside our
throat. Without the eyelids, our eyes would dry out and potentially be damaged
from dust. In the same way, the delicate antennas, that act as receivers and
transmitters of electromagnetic signals of the radar, also need protection from for
example humidity, dust, wind and even birds [1]. This is where the radome, a
combination of the words radar and dome, steps in.
The radome has the simple but very important function to protect the radar.
However, the radome should be as transparent as possible to the electromagnetic
waves which are received and transmitted; as well as being sufficiently robust in
order to protect the radar. This is a difficult give and take balance that a radome
designer needs to keep in mind; the solution in a given situation is not trivial. The
development and broader usage of radars within for example surveillance and the
automotive industry has increased dramatically since World War II [2]. Radars
have become more mainstream and considerably cheaper as well as used for much
shorter ranges. Due to this, the need for the radar to be able to “see” within
wide angles has increased. Just as you will see more reflections on a window when
the light hit at certain angles, the radar will also experience reflections from the
radome at some angles. During this project we have developed general design
methods to decrease these reflections at wide angles. Our focus has been on
sandwich radomes, which is as its name implies, a radome with multiple layers
of different materials. This means that, using these methods, a radome designer
will be easier able to design and optimize a radome for wide angles for a given
problem. What has been especially interesting is that with our suggested method,
an initially, relatively simple and potentially cheap design with low reflections for
a wide range of angles can be quickly calculated without the need for slow and
calculation intensive simulation software.

• author: Fajerberg, Martin and Nylander, Mattias
• supervisor: Johan Lundgren
• organization: Department of Electrical and Information Technology
• course: EITM01 20221
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Radar, Radome, A-Sandwich, B-Sandwich, Multilayer, Polarization, Angle of Incidence, Finite Element Method, Differential Evolution Optimization, Transmission Line Theory, Honeycomb, Additive Manufacturing, Electromagnetic Theory
• report number: LU/LTH-EIT 2022-866
• language: English
• id: 9086052
• date added to LUP: 2022-06-14 16:35:52
• date last changed: 2022-06-14 16:35:52