SINGLE STAGE RF AMPLIFIER AT 5.8GHZ ISM BAND WITH IEEE 802.11a STANDARD A. R. Othman 1 , I. M. Ibrahim 2 , M. S. A. S. Samingan 3 , A. A. A. Aziz 4 , M. F. M. Selamat 5 , H. C. Halim 6 1,2,3,4,5,6 Fakulti Kejuruteraan Elektronik Dan Kejuruteraan Komputer, Universiti Teknikal Malaysia Melaka, 75450 Ayer Keroh, Melaka. Email: 1 rani@utem.edu.my, 3 mdsaifulazri@gmail.com Abstarct - This paper describes the circuit design and measurement of a single stage RF amplifier for 5.8 GHz-band with IEEE 802.11a standards for WLAN applications. The circuit was simulated using Ansoft Designer where a 14dB of gain; input and output return loss less than -10dB were observed. The GaAs Hetrojunction FET (HFET), capacitors and resistors are combined with the microstrip line pattern by silver epoxy. A 1dB output power compression point (P 1dB ) of 17dBm and 14.56dB of gain when -1dBm power injected under 6V and ½ I dss biasing are measured. Index Terms: RF Amplifier; Gain; Matching Circuit; Wireless LAN. I. INTRODUCTION Current solutions exploit the worldwide license-free 2.4 GHz frequency band. Unfortunately, many applications nearly overcrowd this band such as high-power microwave ovens, cordless phones, Bluetooth ® and HomeRF applications, WLAN, game pads, etc. As a consequence, significant RF interference is present within the 2.4 GHz band [1]. Recently, wireless LAN system have been developed for the C-band (4~8 GHz) frequency. Proposals for wireless data system in the C-band range such as 5.8 GHz (Wireless LAN for U.S.A) and 5.2 GHz (Hiper LAN for Europe) have been submitted [2]. The license-free 5.8 GHz frequency band provides wider spectrum frequency. Furthermore, investigations showed that 5 GHz applications in narrow surroundings can provide better performance than 2.4 GHz applications as the shorter wave length propagates farther. In addition, 5.8 GHz system nearly always be operated at higher data rates than 2.4 GHz systems in form of bandwidth [3]. The power amplifier is the most important and expensive device in the RF block of Wireless LAN system [4]. Like all other amplifiers, stability is a major concern [5]. This paper is focused on the development of RF amplifier for point-to-point WLAN application. A single-stage RF amplifier is fabricated using GaAs HFET on microstrip substrate. The size of the circuit is reduced by utilizing high dielectric substrate. Figure 1 shows the block diagram of RF amplifier module. Fig. 1. Schematic diagram of RF amplifier module The RF amplifier consists of input and output matching network as passive part and amplifier chip driven by DC bias circuit as an active part. The impedance of the circuit is relatively 50. II. CIRCUIT DESIGN In short, basic concept of high frequency amplifier design is matching input/output of transistor for high frequency having [S] frequency characteristics at a specific DC-bias point with source impedance and load impedance. I/O matching circuit is essential to reduce unwanted reflection of signal and to 1-4244-1435-0/07/$25.00©2007 IEEE