Low Noise Figure and High Gain Single Stage Cascoded LNA Amplifier With Optimized Inductive Drain Feedback for WiMAX Application Othman A.R* 1 , Pongot K #,*2 , Zakaria Z* 3 , Suaidi M.K* 4 , Hamidon A.H* 5 # Bahagian Sumber Manusia, Majlis Amanah Rakyat (MARA) Tingkat 17 & 18 Ibu Pejabat MARA, Jalan Raja Laut , 50609 Kuala Lumpur , Malaysia kamilpongot@yahoo.com.sg * Centre of Telecommunication and Innovation (CETRI), Faculty of Electronics and Computer Engineering Universiti Teknikal Malaysia Melaka (UTEM), Karung Berkunci, No.1752, Pejabat Pos Durian Tunggal, 76109, Durian Tunggal, Melaka, Malaysia. kamilpongot@yahoo.com.sg , rani@utem.edu.my, zahriladha@utem.edu.my, kadim@utem.edu.my, hamid@utem.edu.my Abstract— This project presents a low noise and high gain cascoded LNA amplifier for direct conversion RF front end receiver architecture, which operates at 5.8 GHz unlicensed band. The LNA used Transistor FHX76LP superHEMT low noise FET. This LNA was designed and used inductive feedback and T- matching network consisting of lump reactive at the input and output of the LNA circuit. A single cascoded LNA design was built to meet the standard of IEEE 802.16. The cascoded LNA produced low noise figure of 0.83 dB with high gain of 26.26 dB. The S-parameter for the input reflection S 11 , output reflection S 22 , and return loss S 12 are of -11.05 dB, -10.5 dB and -30.92 dB respectively. The bandwidth measured is 1.56 GHz, while the input sensitivity is -82.6 dBm which is compliant WiMAX standards. The single stage LNA amplifier simulated using Ansoft Designer SV. Keywords- RF front-end; Direct Conversion; WiMAX; Receiver Sensitivity; IEEE 802.16; Cascoded LNA; inductive feedback. 1. INTRODUCTION Radio-frequency (RF) transmission is one of the best examples to show a very challenging technological demands in communication systems. Systems built using RF transmission often used in daily life such as mobile phones, notebooks, wireless sensors, among other, require an increasing versatility and suggest an ability to storage of data transmission rates of a huge information and size reduction. In this paper, we want to discuss, the solutions needed to be done to address the increasing number of wireless personal communication systems demand for Radio Frequency (RF) front-end receivers capable to handle standard specification difference, i.e.| WiMAX, WLAN, WiFi. According to the standard IEEE 802.16 (WiMAX) it can transmit data rates exceeding speeds of 70 Mbps and a service area of about 50km for fixed stations and 5-15 km for mobile stations [2]. For a RF front-end receiver used in WiMAX system at 5.8 GHz would have to be designed for desired frequency, gain, bandwidths and noise figure. Multiple parameters such as gain and noise figure in the RF component for the front – end receiver would have to be compensated. These trade-offs are the challenges that RF designers have to consider in designing a high performance communication system. In Fig. 1 it shows a direct conversion RF front-end receiver . It consists of an antenna, cascaded LNA and a filter. The RF input signal fed through the system is very weak. Since the RF front-end requires amplifiers to amplify the RF signal and at the same time lowering the noise figure that passes through it, this can only be done by using an LNA. To design a low noise amplifier of the RF front-end receiver, we will be face many drawbacks. Moreover, the circuit must meet certain specifications as well as to provide suitable input impedance match, sufficient gain power and low noise figure (NF) within the required band [4]. Othman A.R et.al / International Journal of Engineering and Technology (IJET) ISSN : 0975-4024 Vol 5 No 3 Jun-Jul 2013 2601