A DC to 20 GHz Ultra-Broadband High-Gain-Linear Distributed Power Amplifier with 19.5% Drain Efficiency Hadi Bameri, Ahmad Hakimi, Masoud Movahhedi Dept. of Electrical Eng. Shahid Bahonar University of Kerman Kerman, Iran hakimi@mail.uk.ac.ir Hossein Abdollahi Dept. of Electrical and Computer Eng. Tarbiat Modares University Tehran, Iran abdollahi@modares.ac.ir Abstract— In this paper an ultra-broadband linear distributed power amplifier (DPA) is presented. This amplifier consumes only 100 mW DC power and amplifies input powers up to -3.7 dBm with a power gain of 16.7 dB linearly. Output power at 1-dB compression point is 13 dBm in the linear-mode. By increasing the level of input power, the amplifier no longer works in the linear-mode, drain efficiency and non-linear distortions are increased, and power consumption is decreased to 90 mW. S 21 parameter is 18±0.9 dB over DC to 20 GHz. The architecture of all power gain cells (including three stages) is cascade of inductively coupled common source. This amplifier is simulated in a 0.13 um CMOS technology. Keywords- distributed amplifier; ultra-broadband; cmos technology I. INTRODUCTION There is a trade-off between frequency bandwidth and power gain of a PA in both wired and wireless communication systems. Meanwhile, the amount of noise presented in existing systems, decrease channel capacity [1]. To overcome the coming noise effect and then constructing an immune system, the frequency bandwidth and transmitted power should be desirably increased. By increasing frequency bandwidth or transmitted power, data rate would be also increased in an immune way [1]. Radiography systems gain special data of an object by sending and receiving waves over a wide-bandwidth. Therefore, a complete recognition of the object is available by radiography. On the other hand, an increasing demand of sending data with high rates has increased the design of wide- band systems. As a result, design and fabrication of wide- bandwidth transceivers is an interesting problem to RF circuit designers. The most important part of a transceiver is power amplifier (PA), which has an intrinsic role in supporting wide- bandwidth as well as high gain. The most proper concept to increase frequency bandwidth is distributed amplifier structure . Until now, many papers have been reported in which distributed voltage amplifiers have been designed and manufactured [3-7]. In this paper, a DC to 20 GHz ultra-broadband distributed power amplifier (DPA) is presented. This class-A DPA has a power gain of around 16.7 dB and PAE of 19.5% while delivers output power of 13 dBm at 1-dB compression point to a 50  load. The technology foundation used to simulate this DPA is 0.13 um CMOS. II. CIRCUIT ANALYSIS Single stage linear PAs are categorized into four classes: A, AB, B, and C based on duty cycles of their drain currents. Different duty cycles are made by altering input DC bias voltage [8]. However, class-A PAs have the least drain efficiency, but their high output power (higher power gain for a constant input power) and highest linearity are interested in this work. Owing to the limited output power of a single sage PA, parallel power combining is the best idea to support high output power, as though, power losses due to the N-way power dividers and combiners makes it less practical [9]. On the other hand, distributed amplification technique is used to increase frequency bandwidth, could also solve the power losses of N-way paths at input/output of parallel power dividing/combining. Furthermore, every single amplification stage in a distributed power amplifier (DPA) should linearly amplify signals and then distributed amplification theory and artificial transmission line analysis can be applied. A DPA absorbs the input and output parasitic capacitances of the gain cell (which have the main role to limit the bandwidth) into transmission line like structures which form a high order LC ladder filter, while combining gain in an additive fashion. Fig. 1 shows a basic distributed amplifier. A distributed amplifier consists of a gate line and a drain line implemented either by artificial transmission lines (comprising of cascade of LC filter sections to form a ladder type structure) or by uniform transmission lines. The characteristic impedance of these transmission lines and its phase velocity can be found, respectively, as 0 , P L Z LC C ν = = (1) Proceedings of ICEE 2010, May 11-13, 2010 978-1-4244-6761-7/10/$26.00 ©2010 IEEE 409