wideband BPF for DM and CM operations, respectively. The measured and simulated results are seen to agree very well with each other for both modes of operations. For the DM response, the measured (simulated) passband is centered at 4.68 (4.65) GHz, with a 3-dB frequency range from 2.89 (3.02) to 6.41 (6.35) GHz. The measured (simulated) DM minimum IL is 0.7 (0.3) dB. For the CM response, the measured (simulated) IL is greater than 20.3 (20.1) dB. Note that CM signals are sup- pressed not only in the DM passband but also in the displayed frequency range of 1–10 GHz. Some small discrepancies are observed between the measured and simulated results, which could be attributed to slight misalignment of the top and bottom circuit patterns. 4. CONCLUSIONS A new balanced wideband BPF has been proposed and con- structed using a single piece of SLMMR with tightly coupled feeding lines. The wideband DM response has been achieved by designing the first three resonant modes of the SLMMR to locate evenly in the designated passband. With the in-band com- mon modes effectively suppressed, a CM suppression of larger than 20 dB in all the displayed frequency range of 1–10 GHz has been achieved. ACKNOWLEDGMENTS This work was supported by the National Science Council of Tai- wan (The Republic of China) under Grant NSC 100-2221-E-018- 030-MY2. REFERENCES 1. C.H. Wu, C.H. Wang, and C.H. Chen, Novel balanced coupled- line bandpass filters with common-mode noise suppression, IEEE Trans Microwave Theory Tech 55 (2007), 287–295. 2. C.H. Wu, C.H. Wang, and C.H. Chen, Stopband-extended balanced bandpass filter using coupled stepped-impedance resonators, IEEE Microwave Wireless Compon Lett 17 (2007), 507–509. 3. C.H. Wu, C.H. Wang, and C.H. 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Hong, Ultra-wideband (UWB) bandpass filter with embedded band notch structures, IEEE Microwave Wireless Compon Lett 17 (2007), 193–195. V C 2012 Wiley Periodicals, Inc. X-BAND GaAs MMIC HIGH POWER AMPLIFIER FOR TRANSMITTER SPACE MODULE Rocco Giofre, Paolo Colantonio, Franco Giannini, and Luca Piazzon Department of Electronics Engineering, University of Roma ‘‘Tor Vergata,’’ via Del Politecnico n.1, 00133 Roma, Italy; Corresponding author: giofr@ing.uniroma2.it Received 28 February 2012 ABSTRACT: In this letter, the design, realization, and test of an X- band GaAs microwave monolithic integrated circuit high power amplifier (HPA) are reported. The HPA is designed in a two stage configuration to fully match a 50 X input and output impedance. Experimental results show that the HPA reaches an output power higher than 38 dBm with a gain higher than 17 dB and a ripple lower than 0.5 dB from 9 to 10.2 GHz frequency range. The power added efficiency is around 40%. The good level of performance and the low sensitivity to the environment temperature make this amplifier an excellent candidate for X band applications in phased array active antennas. V C 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2633–2635, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27109 Key words: high power amplifier; GaAs; space application 1. INTRODUCTION Microwave monolithic integrated circuit (MMIC) power ampli- fiers with high performances are key elements in many applica- tions such as radar transmitters, satellite systems, and military equipments [1]. Actually, at least in the satellite segment, the most adopted and reliable technology is based on gallium arse- nide (GaAs) semiconductor. Conversely, the high power ampli- fier (HPA) is the most power-consuming subsystem. The devel- opment of compact and performing transmitter module requires very performing HPAs, especially for space application. In the past, for such applications, the final power stage was usually realized by hybrid amplifiers [2] or prematched FET mini-mod- ules [3], delivered in hermetic sealed ceramic packages. Nowa- days, the sustainability of GaAs processes gives the opportunity to synthesize these functions in a monolithic die, with obvious advantages in terms of cost, space, reliability, and performance reproducibility. Conversely, as the power density is usually lower than 1 W/mm 2 , to achieve high levels of output power using GaAs technology several single transistors have to be combined together. Therefore, the most challenging step in such designs is represented by the ability to find a power combining- structures characterized by low losses, small sizes, and high power handling. In this context, a MMIC HPA for X-band satellite systems (synthetic aperture radar, SAR) was designed and developed exploiting a 0.4 lm p-HEMT power process developed at SELEX-SI (Italy) foundry. At the nominal bias point, the HPA reaches an output power higher than 38 dBm with a gain larger DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 54, No. 11, November 2012 2633