Copyright © 2018 Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unre- stricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering & Technology, 7 (2.6) (2018) 217-220 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET Research Paper Design and Development of a 3dB Quadrature Patch Hybrid Coupler B. Sekharbabu 1* , K. Narsimha Reddy 2 , S. Sreenu 3 1 Assistant professor 2 Assistant professor 3 Assistant professor 1,2,3 ECE department, Vardhaman college of Engineering (Autonomous), Shamshabad, Hyderabad, India. *Corresponding author E-mail: sekharbabu81@gmail.com Abstract In this paper a -3 dB, 90-degree phase shift RF quadrature patch hybrid coupler is designed to operate at 2.4GHz. Hybrid coupler is a four- port device, that’s accustomed split a signaling with a resultant 90 degrees’ section shift between output signals whereas maintaining high isolation between the output ports. The RF quadrature patch hybrid coupler is used in various radio frequency applications including mixers, power combiners, dividers, modulators and amplifiers. The desired hybrid coupler is designed using FR-4 substrate with 1.6mm height in High Frequency Structure Simulation (HFSS) and the same is fabricated and tested. The designed Hybrid coupler is examined in terms of parameters like insertion Loss, coupling factor and return Loss. The simulation and measurement results are compared. Major advantages of the RF quadrature patch hybrid couplers are that they are compatible with integrated circuit technology. Keywords: Coupling factor; FR-4 substrate; Insertion loss; Return loss; Quadrature patch 1. Introduction Microwave couplers are devices whose primary functionality is to divert some amount of information from one path to another path [15]. The signal which is coming from the output side of first path is called “direct signal” Because it is directly connected to the in- put Port. Signal coming from the second path of output side is called the “coupled” signal. In this letter a -3 dB, 90-degree phase shift quadrature patch hybrid coupler is designed to mainly operate at the frequency 2. 4GHz.A -3 dB, 90° hybrid coupler is a four- port device that can split an input signal equally or un equally with a resultant 90° phase shift between two output ports or to combine two signals by maintaining high isolation between the ports. [5] The performance of any hybrid coupler is examined with help of the following parameters [9]. • Insertion loss • Isolation • Coupling factor • Phase shift • Band width 1.1. Insertion Loss: Insertion loss in telecommunication is due to the insertion of a de- vice. the quantity of insertion loss for any device is expressed in terms of decibels and it's indicated with IL. Ideally the insertion loss for hybrid coupler is 3dB. If the power transmitted to the load before insertion is P1 and therefore the power received by the load once insertion is P2, then the insertion loss in dB is calculated by using the below formulae [6], IL (dB) =10 *log10 (P1/P2) (1.a) IL (dB) =10* log10(P1/P3) (1.b) 1.2. Coupling Factor: Coupling factor is the parameter which occurs when the power is transferred from one circuit element to other circuit element [3]. Sometimes coupling factor is also called as coupling loss or Con- nection Loss and it is indicated with C. Normally coupling factor value is expressed in terms of dB. If the power at port1 is P1and power at coupling port is P3, then the coupling factor value can be expressed as [17] C (dB) =10*log10(P4/P1) (2) 1.3. Isolation: Isolation is the parameter which will gives information about power transmitted between the unwanted ports. [4] In quadrature hybrid coupler the port 4 act as back port. Ideally there is no power is transmitted between port 1 and port 4 and isolation is considered as zero. But in practical case there will be some minimum power will be transmitted between port 1 and port 4. The isolation will give how much power is observed at port 4. If the power at port 1 is P1 and power at port 4 is P4 then isolation can be calculated using the formulae [8]. I(dB) = -10*log10 (P4/P1) (3)