9. M. Sellone, N. Shoaib, and P. Terzi, Characterization of the Vector Network Analyzer used as primary S-parameter standard, Technical report no. 3/2015, Istituto Nazionale di Ricerca Metrologica (INRIM), Turin, Italy, (2015), 1–202. 10. MATLAB 2011- The Language of Technical Computing. Informa- tion Available at: http://www.mathworks.com. 11. G.F. Engen and C. Hoer, A Thru-reflect-line: An improved tech- nique for calibrating the dual six port automatic network analyzer, IEEE Trans Microwave Theory Tech MTT 27 (1979), 987–993. 12. B.W. Wier, Automatic measurement of complex dielectric constant and permeability at microwave frequencies, Proc IEEE 62 (1974), 33–36. 13. A.R. Von Hipple, Dielectric Materials and Applications, Artech House, 1995. V C 2016 Wiley Periodicals, Inc. A 60-GHz MULTI-BEAM ANTENNA ARRAY DESIGN BY USING MHMICs TECHNOLOGY Elham Erfani, Emilia Moldovan, and Serioja Tatu Institute National De La Recherche Scientifique (INRS), Montr eal, QC, Canada; Corresponding author: elham.erfani@emt.inrs.ca Received 23 December 2015 ABSTRACT: The integration feasibility of two technologies including Miniaturized Hybrid Microwave Integrated Circuit (MHMIC) and Printed Circuit Board (PCB) are experimentally demonstrated at milli- meter wave frequencies through the design of a switched beam antenna array. A 1 3 4 array of aperture coupled patch antennas etched on a RO5880 substrate is fed by a 4 3 4 butler matrix etched on a piece of high permittivity ceramic substrate. By using the proposed combined fabrication technologies, the feeding part on the ceramic substrate can be easily integrated with MMIC active component, while the radiation part is individually improved. Comparison of simulated and measured results show that the proposed switched beam antenna offers a 210 dB matching bandwidth of 6 GHz ranging from 58 GHz to 64 GHz and a multi beam radiation pattern which is focused in 458, 158, 2158, 2458 directions. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1844–1847, 2016; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.29926 Key words: millimeter-wave; MHMIC technology; Butler matrix 1. INTRODUCTION Recently, the use of unlicensed 60 GHz band has drawn significant attention due to increasing demand of ultra-high data rate communi- cations over 1 Gbit/s for the wireless local area network (WLAN) and short range multimedia download [1]. As a paramount compo- nent of such communication links, different kinds of millimeter wave antennas have been proposed so far [2–6]. In most of these works, high gain antennas have been developed to overcome the propagation path loss of this frequency band and hence improve the system signal-to-noise ratio. Besides, employing an antenna array with a beam forming property is also required to achieve directive radiation beams in the desired spatial directions [7,8]. Beam forming can be cost-effectively realized by using a Butler matrix network, which provides appropriate phases and amplitudes as excitations of array elements according to the desired beams’ directions [9–11]. In this perspective, selecting an appropriate material platform for system integration is an important task in the design of a low cost, compact, and high performance beam forming struc- ture. Having excellent high-frequency performances, there are many new thin materials such as liquid crystal polymer (LCP), low temperature co-fired ceramic (LTCC), and ceramic which have been explored for millimeter wave applications [7,10,11]. Among them, ceramic technology has received considerable atten- tions for antenna/microwave applications specifically because of its inherited low-loss and high dielectric constant features. Indeed, this results in realization of an efficient and compact circuit design at such high frequency range. In addition, the ceramic substrate is compatible with the usual 100 mm thick MMIC active component for integration, in which MMIC chips are placed in rectangular cuts on the ceramic allowing easy wire bonding with MHMIC components [12]. Although, ceramic is optimal choice for millimeter-wave frequency band, integrating an array antenna with a feeding network on the same substrate causes to deteriorate the antenna radiation pattern and its efficiency [12]. Separating antenna and feeding network is deemed to be an effective approach to enhance the antenna radiation pattern and its bandwidth. In this work, to address this challenging problem, ceramic multilayer lamination capability has been investigated by inte- grating a piece of ceramic material (MHMIC technology) with RO55880 substrate (PCB technology). Therefore, a 60 GHz cir- cuit characterization of passive MHMIC element on thin ceramic substrate has been carried out to build a Butler matrix that is used as a feeding network of an aperture coupled patch antenna array. Although, demonstrated with linearly polarized aperture coupled patch element, this structure can be used with different planar radiating elements to have other radiation char- acteristics such as circular polarization or higher gain perform- ances, while the passive beam forming network can be easily integrated with other active circuits such as LNA and switches. 2. DESIGN OF BUTLER MATRIX AND ANTENNA The proposed 60 GHz switched beam antenna consists of a 4 3 4 Butler matrix and a 1 3 4 aperture coupled patch antenna array as illustrated in Figure 1. In this structure, in order to avoid the adverse influence of the feeding network on the antenna radiation pattern and also have a high efficient radiator, the Butler matrix and antenna array have been implemented with two different substrates. The antenna array is etched on a piece of RT/duroid 5880 substrate with e r 5 2.2 and thickness of 254 lm, while the feeding network is etched on a piece of thin ceramic material with e r 5 9.9 and thickness of 127 lm. Two substrates are stacked together with a thin layer of glue with e r 5 3.4 and thickness of 5 lm. Indeed, by utilizing this structure Figure 1 Configuration of the developed switched-beam antenna using Butler matrix feeding network. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com] 1844 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 58, No. 8, August 2016 DOI 10.1002/mop