Metal-Dielectric Radomes

Avraham Frenkel, Ph.D

Anafa – Electromagnetic Solutions Ltd.

New Metal-Dielectric Window

The basic design is a thick dielectric slab with a central periodic array of conducting inclusions

Dielectric layer thickness is about 0.75

Array spacing and inclusion size are optimized for maximum transmission

Unit-cell of the Periodic Structure

Total thickness :

8.8 mm

Dielectric –polyimid

Eps=3.5

Tangent-loss=

0.0027

Unitcell d=3mm

The Double Pole in Reflection

The Double Pole in Transmission

Bandwidth Dependence on

Dielectric Constant

Typical bandwidth at -0.5db Transmission

loss :

=2.2 BW= 66%

=4.4 BW= 40%

=9.2 BW= 28%

Simplified Equivalent Circuit

377ohm 377ohm

Simplified Circuit

Reflection

Simplified Circuit

Transmission

Radome Transmission

Dependence on Cylinder Radius

Equivalent Radomes

H=0.9 mm , r=0.98 mm

H=1.0 mm, r=0.95 mm

H=1.2mm, r=0.90 mm

Internal Grating Lobes

Unitcell size d< wavelength-in-air/2 to

avoid external grating lobes

But we must avoid unitcell size d<

wavelength-in-dielectric/2 to avoid internal

grating lobes that resonate

We check d=8mm, r=1.7mm

Internal Grating Lobes

TE case

D=8mm, r=1.7mm, h=1.2mm

Internal Grating Lobes

TM case

D=8mm, r=1.7mm, h=1.2mm

THz Window

Two layers of scatterers

Periodic grid of sub-resonant

scatterers

Dielectric constant – 2.94

Total thickness 0.762 mm

=> 1.5 wavelength at 0.35 THz

Metal via : diameter =0.11mm

height=0.127mm ,

periodicity= 0.2mm

Transmission

Dielectric Window vs. Metal-dielectric Window

Reflection

Dielectric Window vs. Metal-dielectric Window

Transmission

Oblique Incidence

Radome Performance

Radome size 54X54 unit-cells,

10.8X10.8 mm

The radome is in the quasi-far

-field of the horn

Horn aperture is about 2X2

Wavelengths

T_solver is used

14.2Mcells

Horn Reflection

Azimuth Cut

with and without Radome

Elevation cut

with and without Radome

Compensation of Thick Skins

Metal inclusions allow the use of thick

skins in a composite radome.

Ku radome design with 5mm foam core

and two skins (r=4.3) of thickness

t=1mm.

Radome with Thick Skins

- Geometry

d= 6mm

Skins 1mm thick

eps=4.3

Core 5mm thick

Eps=1.2

Printed circular patches

Radome with Thick skins

- Transmission Normal Incidence

Radome with Thick skins

- Oblique Incidence

Metal-Dielectric Windows

SUMMARY

Novel thick radomes loaded with periodic array

of sub-resonant conducting inclusions are

presented.

The conducting inclusions allow the tuning of all

dielectric discontinuities.

The method offers many degrees of freedom in

the design.

This metal-dielectric technology is patented.