Very Small Multi-Layers Proximity Coupled Antenna for ISM-band Applications Jalal Naghar (1) , Otman Aghzout (2), Azzeddin Naghar (1) , Mohamed Essaaidi (3) . jalalnaghar@gmail.com, azz.naghar@gmail.com, o.aghzout@gmail.com,essaaidi@gmail.com. (1) Faculty of Sciences, Abdelmalek Essaadi University,Tétouan ,Morrocco (2) National School of Applied Sciences,Abdelmalek Essaadi University,Tétouan,Morrocco. (3) National School of Computer Science and Systems Analysis,Mohamed V-Souissi,Rabat,Morocco Abstract- A very small new design of a multilayer antenna for wireless communication systems is proposed in this paper. It consists of three different combination layers, separated by air gaps and feeding by the electromagnetic coupling scheme. The low cost FR4, Arlon and Roger substrates with a Cooper thickness of50μm, are used in the proposed antenna design. The feed line is inserted between the two first substrates and the slotted radiating patch on top of the second layer, while the third has a square parasitic element located on the top of the higher substrate. The total size of the proposed antenna is 6x6x4.92mm3, taking in consideration the two air gaps. The antenna operates in the Industrial, Scientific and Medical (ISM) frequency band at 2.45 GHz. It covers a several standards of communication like Wi-Fi (IEEE 802.11b), Bluetooth (IEEE 802.15.1), Zigbee (IEEE 802.15.4), WIMAX (IEEE 802.16) and WLAN (802.11b,g). A study based on the slotted radiating patch and square parasitic element has been firstly introduced to reduce the antenna surface. In order to improve the antenna performance in term of resonance frequency, volume size, return loss and bandwidth, a study of substrate materials is introduced and new antenna designs are achieved. Simulation results obtained by CS MWs demonstrate that the antenna is a good candidate for the systems in package operating at 2.45 GHz. Index Terms-Very small antenna, Multilayer patch antenna, antenna in package. I. INTRODUCTION Rapid progress in wireless communication systems lead to a fast evolution in the antenna design to take up the challenges in size, performance and cost. Each type of antenna is good in its own properties and usage. Nowadays, microstrip antennas are very well suited for applications such as wireless communications system, cellular phones, pagers, radar systems, and satellite communication system. Microstrip antennas have several advantages such as lightweight, small volume, and that they can be made conformal to the host surface. In addition, they are manufactured using printed- circuit technology, so that mass production can be achieved at a low cost. Therefore, it is challenging to design and miniature microstrip antennas to have better radiating properties with a compact size. The size of the antenna printed on the substrate with high dielectric constants is nearly a factor of √  ௥ and smaller than the antennas designed on the air substrate, in which is the dielectric constant of the substrate [1]. However, this technique not only raised the cost of the antenna, but also not applicable to integrated communication systems whose substrate dielectric constant is always small. In the literature, authors use several techniques to design patch antennas with miniaturized size. Some of them consist on insertion of shorting posts and pin [2], short circuit [3] and cutting slots in radiating patch [4-5]. The optimization is obtained also by partially filled high permittivity substrate[8], using fractal microstrip patch configuration [6] and increasing the electrical length of the antenna by optimizing the shape [7] and ching periodical slow wave structures on the ground plane [8]. Not that, the maximum percentage of size reduction using these techniques is about 65% [9]. A small mutilayer antenna mounted on the different substrates is proposed in this contribution, to operate in the Industrial, Scientific and Medical (ISM) frequency band at 2.45 GHz. The antenna has three layers separated by air gapping with feed line in the first, a slotted radiating patch in the second and a square parasitic patch in the third layer. The FR4, Arlon and Roger substrates with a Cooper thickness of 50μm are combined together to obtain the best results and design for the proposed antenna. An optimization study of size and performance based on different dielectric substrates is also introduced. The resulting antenna configurations are presented and compared, refereeing to the conventional design. The total size, center frequency and bandwidth of each case are studied in detail to achieve the optimal design. The CST MWs electromagnetic simulator is used to perform the antenna characteristics. The antenna results show a good return loss of -50dB and bandwidth of 2.1 GHz with a low fabrication cost and small size. These performances demonstrate that the proposed antenna is good candidate wireless communication systems operating at 2.45GHz. As additional features, the antenna can be easily integrated with active devices due to its relatively small size. II. MULTI-LAYERS PATCH ANTENNA DESIGN A. Geometry of the proposed antenna Our objective in this paper is to design a novel antenna based on wireless application systems developed previously [10-11]. The proposed multi-layer structure antenna is composed by multi-layers substrates and multi-conductor. A long detailed study on the antenna parameters was taken into account to miniaturize the dimensions of the antenna, precisely the effect of the slotted radiating patch and square parasitic element. After a long procedure design, a exploded view of this antenna is can be shown in Fig. 1.As a first step, the antenna is implemented on FR4 substrate with dielectric constant of 4.4 and thickness of 1.6 mm. The ground plane dimensions are  ௚ × ௚ = ͸ × ͸  2 .