This Final Project deals with design of upconverter block on transceiver for radio-frequency (RF) WiMAX chip. The main problem in this kind of design is to obtain optimum linearity so that satisfying WiMAX specification. However, RF circuit has non-linearity as natural characteristic.
The important component of upconverter block is mixer circuit. Considering direct-conversion transmitter architecture, the design is comparing some circuit topology. Hence, active double-balanced Gilbert cell mixer is chosen. Design is continued by modifying amplifier stage (gain stage) where specific linearity range is needed to accommodate baseband signal level from data converter (Digital-to-Analog Converter) output.
Circuits are implemented in AMS (Austria Micro System) SiGe (Sillicon Germanium) 0.35µm BiCMOS (Bipolar and Complementary Metal Oxide Semiconductor) technology. In this case, design of all active devices is using bipolar junction transistor (BJT). Detailed performances are observed with SIMetrix v5.5 simulator tool.
The goal of the design that is to achieve highly linear upconverter has successfully accomplished. With an IIP3 exceeding 15dBm and 1-dB compression point reaching 5.45dBm, the proposed mixer circuit is well suited for transceiver system. Although noise has not been design issue in transmitter, it is also analyzed and giving SNR of the circuits at 92.01dB.
For approximately 40mW of power consumption, the circuits work at 3.5MHz, 5MHz, 7MHz, 10MHz, 14MHz, 20MHz, and 28MHz input bandwidth. This design meets the need of national WiMAX research since output frequency territories are at 2.3–2.39GHz and 3.3–3.4GHz.
Keywords: mixer, amplifier, upconverter, transmitter, direct conversion, transceiver, WiMAX.