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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...

A suitable large signal design method of distributed power amplifiers, based on the optimum FET load requirement for high power operation, is proposed in this article. The gate and drain line characteristic admittances are determined, providing both the initial values and right directions for an optimum design. To validate the proposed design method, a FET amplifier demonstrator with a gate periphery of 1.2 mm has been manufactured at the Texas Instruments foundry. The MMIC distributed amplifier demonstrated an improved power density performance of 340 mW/mm over the 2–18‐GHz frequency band associated with a minimum of 13% power‐added efficiency and 24% drain efficiency at 1‐dB compression in CW operation. © 1996 John Wiley & Sons, Inc.

A suitable and effective design method of distributed power amplifiers, based on the optimum FET load requirement for power operation, is proposed in this paper.An analytical determination of the gate and drain line characteristic admittances provides both the initial values and right directions for an optimum design. The best trade-offs between wide band and high power operation have been investigated.To validate the method, a FET amplifier demonstrator with a gate periphery of 1.2 mm has been manufactured at the Texas Instruments foundry. The MMIC amplifier demonstrated state of the art power density performance of 340 mWlmm over the 2-18 GHz band associated with 14.2 % power added efficiency, 26.5 % drain efficiency and 26.1 dBm output power at 1 dB compression in CW operation. 94CH3351-4/94/0000-0125$01.OCl 0 1994 IEEE IEEE 1994 Microwave and Millimeter-Wave Monolithic Circuits Symposium

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