Compact dual-fed distributed power amplifier

Abstract

Abstract-The dual-fed distributed amplifier (DFDA) allows efficient combining of field-effect transistors (FETs) at the device level without using -way power combiners. However, the FETs must be spaced 180 , resulting in physically large circuits. In this paper, meandered artificial transmission lines (TLs) comprised of microstrip lines periodically loaded with short open-circuit stubs can be used in place of TLs to reduce the size. The approach incorporates FET input and output capacitances with the artificial TLs, thereby eliminating their detrimental effects on bandwidth and performance. Both simulation and experimental results of a class-A three-FET single-ended DFDA designed to operate at 1.8 GHz demonstrate the feasibility of this approach and the validity of the design method. The size reduction is approximately one-third compared to realization using microstrip lines only, and the maximum efficiency is greater than 35% over a bandwidth of 15%.Index Terms-Distributed amplifiers, microstrip circuits, microwave field-effect transistor (FET) amplifiers, microwave power FET amplifiers.

Dual Fed Distributed Amplifier With Controlled Termination Adjustment

“…Similar technique, by adding Lange couplers or Wilkinson combiners at the input and output of the DA to improve output power, gain and power-added efficiency (PAE), was demonstrated by [7,8]. A compact DFDA with single-ended termination was shown in [9] demonstrating a practical realization with meandered artificial transmission lines loaded with short-circuit stubs. Other works related to DFDA approach were demonstrated by [10,11].…”

Integrated Combined Amplifiers for Planar Circuits

“…FET input and output capacitances mean that these line lengths need to be shortened [21] to maintain correct phasing of the FETs [17]. Although shortening of the transmission lines is desirable, bandwidth is also reduced [22]. An alternative approach is to implement the gate and drain I I lines with artificial transmission lines.…”

“…An alternative approach is to implement the gate and drain I I lines with artificial transmission lines. Using this approach, not only is the transverse width, W, reduced, the FET input and output capacitances are absorbed into the artificial transmission line structure without reducing bandwidth [22]. Fig.…”

“…4 shows the photograph of 3-FET single-ended dual-fed distributed amplifier that operates at 1.8 GHz. This amplifier achieved and output power of 23 dBm over an 11 00 bandwidth and over 35 00 efficiency over a 15 00 bandwidth [22]. Another approach to reduce size is to use the metamaterial approach to realize finite length zero-phase shift transmission lines [23].…”

“…4. 3-FET 1.8 GHz single-ended dual-fed distributed amplifier that uses artificial transmission lines [22] IV. COMBINING OF FETs USING PERIODIC LooP STRUCTURES One of the drawbacks of the optimum dual-fed distributed amplifier is that the load seen by the FET is N times the amplifier load impedance.…”