First demonstration of a 0.5 W, 2 to 8 GHz MMIC HBT distributed power amplifier based on a large signal design approach

Abstract

In this paper we report the results of the first demonstration of a 0.5 Watt, 2 to 8 Ghz MMIC HBT distributed power amplifier optimised with a new design methodology. Initially developed for MESFET transistors, this new design methodology has been applied to HBT devices to obtain simultaneously both high power and high efficiency operation. Thus, a power density performance greater than IW/mm has been demonstrated, compared to the MESFET where a typical value of 0.35W/mm can be observed. Moreover, an average value of 20 % power added efficiency between 2 and 8 GHZ has been measured with a peak efficiency of 30 % at 3 Ghz I-INTRODUCTIONElectronic warfare applications or phase array radar require wide and narrow band MMIC amplifier where both power and high efficiency are desired simultaneously. Although lots of improvements have been made on the MESFET, they do not allow to develop power MMIC with high efficiency, especially for wide band amplifiers where 15 YO seems to be the maximum achievable value. At the opposite, heterojunction bipolar transistor (HBT) have already demonstrated very high power added efficiency for both wide and narrow band applications [l], [2]. Consequently HBT is now considered as one of the best component to design highly efficient MMIC power amplifier. While both power and efficiency are determined by the active devices used in the MMIC, the bandwidth depends essentially on the topology of the amplifier. Distributed amplifier is the best solution to develop very wide band amplifier, but leads to small power density performance associated with low efficiency when classical design technique is used. Nevertheless, in [ 3 ] a new design methodology based on a large signal approach is proposed for MESFET to optimise the output power provided by all the active devices. Thus, the aim of this article is to demonstrate that this new method can be applied to HBT to develop a high efficiency wide band power amplifier.To illustrate the proposed methodology, we describe the circuit design and the first run of a 0.5 Watt, 2 to 8 Ghz MMIC HBT distributed power amplifier optimised for power with 8 dB small signal gain and an average value of 20 % power added efficiency. To our knowledge, this is the first reported distributed amplifier optimised in power using HBT. II-CIRCUIT DESIGN METHODDistributed amplifier represents the typical circuit solution when very wide band (more than two octaves) performance is required. The conventional design technique of power distributed amplifiers is to optimise the circuit for small signal gain using the largest possible transistor that will simultaneously provide the required output power with the desired gain at the highest frequency. Therefore this conventional distributed design technique results in a small power density and efficiency, because each active device delivers only a small part of their available output power. Nevertheless, optimum power performance can be obtained in a distributed amplifier by taking into account with special care large signal require...

Two Octave Phemt Power Amplifier for EW Applications

“…But, conventional distributed amplifiers based on small signal design are not suitable for maximum power operation. The 1 W amplifier presented in this paper has been designed using a methodology based on a large signal approach [1,2]. This methodology is based on a specific tapering of gate and drain lines omitting the drain load to optimise power operation.…”

“…In this context, MESFET technology has shown some good results [1], but is still limited in efficiency and gain at high frequencies. HBT technology has demonstrated the best results in power density and some good results in achieving wide band performance [2,3]. Limitations for this technology are poor gain per stage and low impedance operation.…”

Optimum bias conditions for linear broadband InGaP/GaAs HBT power amplifiers

“…After the bias point is selected, the input and output matching is done using standard distributed amplifier design methodology. A major design issue for HBT distributed amplifiers is that the diffusion capacitance dominates the effective input capacitance [6]. This limits the bandwidth of the amplifier and is further exacerbated for power amplifiers since the diffusion capacitance is proportional to the bias current.…”

Design and analysis of ultra-broadband distributed power amplifiers for multi-platform communications

“…Spice Gummel- References -HBT 1,2,3,4 are from [13], [14], [37] and [1] respectively, HEMT 1,2 are from [16] and [35], FET 1 is from [12], BICMOS 1 is from [11]. [13], [14] and [16] designs are powered from 8V supply, mean while [35] is from 35V, [12] is from 3V, [11]and [37] are from 5V and [1]…”

“…Among the broadband amplifier techniques, the distributed amplifier (DA) is a wellestablished technique [11,13,14,46]. The flat gain and the good terminal match are…”