16-09-2016, 11:47 AM
1454867675-DesignofRFLowNoiseAmplifierusingMODFETfor.docx (Size: 134.76 KB / Downloads: 4)
Abstract
This paper details about the design of Low Noise Amplifier using MODFET for Wireless Communication. The proposed LNA will be operating at 6 GHz and uses two stages for improved gain and low noise figure. The first stage is based on Common source which is followed by the second stage of cascoding configuration. The transistor used in this design is based on p-HEMT technology from Sirenza microdevices. Advanced Design System ADS) is used to design this LNA. The individual stages include capacitors and inductors for DC bias. The input and output matching networks are designed using microstrip transmission lines. The simulation results show gain of 28.27 dB and noise figure as 0.83 dB at 6 GHz with biasing voltage at 3.3 V.
Introduction
Low Noise Amplifier is the key component in almost all wireless communication systems. It plays a vital role of reducing the noise from signal received from antenna. The gain of this amplifier is also important as it will reduce the noise figure of next stages. This concept is mathematically illustrated by Friis formula as
where Ftotal is total noise figure of the system, n is the number of stages, G is the gain of the stage. The proposed design finds its application in IEEE C Band, satellite communication
Amplifier Design
Device Selection
The selected device must satisfy the stability criteria, provide high gain and low noise figure. P-HEMT transistors have high added efficiencies and excellent low noise figures and performance. As our goal being sub-1 dB noise figure, pHEMT GaAs FET may be suitable and is widely used in satellite communication. SPF-2086 TK from Sirenza Microdevices is a high performance 0.25μm pHEMT Gallium Arsenide FET with Schottky barrier gates[1]. This device has 0.7 dB minimum noise figure and maximum gain of 13.5 dB under matched conditions with biasing voltage of 3 V and drain current, 20 mA.
The device has to be verified for its stability using Rollett’s Stability Factor based on S-parameters, defined as
1-|S11|2-|S22|2+|Δ|2
K=
2|S12.S21|
where |Δ|= S11S22 - S12.S21 . The conditions for a transistor to be unconditionally stable are K > 1 and |Δ| < 1. The S-parameter values are obtained from datasheet and the value of K is found to be greater than 1.