The invention relates to a secondary reflector with a frequency-selective surface to be used in antenna systems in general.

The invention specifically relates to an antenna system that comprises a secondary reflector with circular reflector elements and a support-layer with hexagonal holes.

STATE OF THE ART Generally, the secondary reflector structures consist of metal reflective units located on a Kevlar support-layer. The Kevlar layer is a lightweight, carbon-based, solid fiber layer that has a high production cost and is difficult to manufacture. Transition losses are high in the secondary reflectors with Kevlar as a support layer since the entire surface consists of dielectric material. Patent application no. TR201 110652, which is encountered during technical research, a frequency selective surface integrated into the conductive coating related to a radome and a method to obtain this radome. This document mentions obraining dome shaped radomes which are open to one or more forms of radiation. However, this document does not mention the structure of the frequency selective surface.

The patent application document no. US5471224A, which refers to the frequency selective surface in the state of the art, mentions a frequency selective surface using a dielectric layer with rings with hexagonal form. In this system, however, there is no mention of the existence of a frequency selective surface positioned above the dielectric layer and having a hexagonal hole structure. As a result, improvements are being made in secondary reflectors with frequency selective surfaces, so new structures are needed that will eliminate the disadvantages mentioned above and provide solutions for existing systems.

PURPOSE OF INVENTION The present invention relates to an antenna having a secondary reflector with a frequency selective surface that meets the requirements mentioned above while eliminating all disadvantages and providing some additional advantages.

The main purpose of the invention is to minimize the performance losses caused by dielectrics by using a minimum level of dielectric in the secondary reflector. One purpose of the invention is to maintain the structural stability of the secondary reflector by using a dielectric support structure with closely placed hexagonal holes.

Another purpose of the invention is to reduce the production time and provide ease of manufacturing with 3D printing method. Another purpose of the invention is to reduce the weight of the antenna with the dielectric support structure in the hexagonal hole structure located on the dielectric layer produced by a 3D printing method.

To achieve all of the aforementioned advantages and the ones that can be inferred from the detailed description given below, the invention comprises; a main reflector (3) at which an incoming RF signal (A) from a signal source reaches, a secondary reflector (4) by being reflected from the main reflector (3), a second antenna feed (6) to which a transmitted RF signal (C) through the secondary reflector (4) is directed and a first antenna feed (5) to which a reflected RF signal (B) from the secondary reflector (4) is directed. The surface of the secondary reflector (4) comprises a dielectric support layer (1 ) comprising hexagonal holes and a frequency selective surface (2) located on the support layer (1 ) which comprises circular rings. The structural characteristics and all advantages of the invention will be understood more clearly through the following figures and the detailed explanation written regarding these figures. Therefore, the evaluation should be based on these figures and the detailed description. BRIEF DESCRIPTION OF DRAWINGS

The configuration of the present invention and its advantages with further elements will become clear based on the drawings described below.

Figure 1 is a cell view containing the ring structures used in the two-layer structure of the frequency selective surface used in the antenna system. Figure 2 is an overview of the two-layer structure of the frequency selective surface used in the antenna system of invention:

Figure 3 is a detailed view of the frequency selective surface used in the antenna system of the invention.

Figure 4 is the overview of the antenna system of the invention. REFERENCE NUMBERS

1. Dielectric support layer

2. Frequency selective surface

3. Main reflector

4. Secondary reflector 5. First antenna feed

6. Second antenna feed

A. Incoming RF signal

B. Reflected RF signal

C. Transmitted RF signal DETAILED DESCRIPTION OF THE INVENTION

In the herein detailed description, the preferred embodiments of the secondary reflector with frequency selective surface of the invention are described only for a better understanding of the subject matter, without posing any limitations. Figure 4 is an overview of the antenna system of the invention. The invention basically comprises; a main reflector (3) at which an incoming RF signal (A) from a signal source reaches, a secondary reflector (4) at which the incoming RF signal (A) reaches by being reflected from the main reflector (3), a second antenna feed (6) to which a transmitted RF signal (C) through the secondary reflector (4) is directed and a first antenna feed (5) to which a reflected RF signal (B) from the secondary reflector (4) is directed. The surface of the secondary reflector (4) comprises a dielectric support layer (1 ) comprising hexagonal holes and a frequency selective surface (2) located on the support layer (1 ) and comprising circular rings.

The operating principle of the system is as follows:

After the incoming RF signal (A) from the signal source is reflected from the main reflector (3), it is split into two parts as the transmitted RF signal (C) and the reflected RF signal (B) by the frequency selective surface (2) located on the support layer (1 ) located on this reflector (4). In order to minimize the losses due to the mentioned splitting process, the support layer (1 ) is in the form of a mesh consisting of hexagonal holes (Figures 1 , 2 and 3). The frequency selective surface (2) positioned on the mentioned support layer (1 ) is in the form of a mesh consisting of circular rings placed in hexagonal pattern. Due to the hexagonal hole structure of the said frequency selective surface (2), the loss encountered during the splitting into two parts is at an ignorable level. In the secondary reflector (4), metal units are positioned by means of dielectric material. The use of dielectric materials increases insertion loss on the frequency selective surface and decreases the reflection values. Due to being formed of hexagonal holes, performance losses from dielectrics are minimized by using a minimum level of material in the dielectric support layer (1 ).

Figures 1 , 2 and 3 show the dielectric support layer of the secondary reflector antenna system consisting of hexagonal holes. There are circles around the hexagonal holes. There is no connection between circles and hexagons. In a preferred embodiment of the invention, hexagonal holes and circular rings are concentric in order to ensure mechanical stability.