IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 46, NO. 11, NOVEMBER 1998 1757 A Novel Integrated Antenna for Millimeter-Wave Personal Communications Systems K. Hettak, G. Delisle, and M. Boulmalf Abstract— This paper presents the design and experimental results of a coplanar waveguide (CPW) aperture-coupled patch antenna for the extremely high frequency (EHF) band around a center frequency of 37 GHz. The antenna is implemented on a high dielectric constant substrate , which is close to the dielectric constant of GaAs and demonstrates the feasibility of integration of such an antenna structure into monolithic circuits. The major advantage of this configuration is that the reverse side of the antenna can be used for the active and feed components. The antenna structure combines the advantages of CPW with the those of the aperture-coupled microstrip antenna and simplifies the structure of the antenna by reducing the number of metallization level, from three down to two. In addition, this type of coupling is advantageous when applied to millimeter-wave monolithic phased arrays. A unique feed design eliminates the competition for surface space between the antenna elements and the feed network. In addition, the ground plane shields the antenna half-space from spurious radiation emitted by feed lines and active devices. Finally, aperture coupling avoids problems associated with probe feeds at millimeter-wave frequencies, such as complexity of construction and large probe self reactances. This new type of antenna opens the ways to a large number of a new possibilities such as active antennas for millimeter-wave personal communications using monolithic microwave integrated circuits (MMIC’s) on the same substrate and a combination of optical and radio transmission. Index Terms—Coplanar waveguides, microstrip antennas. I. INTRODUCTION The development of appropriate antennas and associated technol- ogy will be important to the success of millimeter-wave wireless personal communication systems. Research in these areas and also on the processes of indoor propagation has been carried out [1] with particular emphasis on integrating antennas with multifunction GaAs monolithic microwave integrated circuits (MMIC’s). The choice between antenna and circuit type depends on many factors such as the intented application, the type of device being used and considerations involving unwanted radiation from the circuit elements and the significance of substrate surface modes. As it is well known, planar antennas consisting of patches, dipoles or slots, fed by a microstrip transmission line, are extremely useful due to their low cost, light weight, and flexibility of design. In general, a combination of slot and patch antennas lead to convenient geometries. Of these the most likely candidate for integration with GaAs MMIC’s is the coplanar waveguide (CPW) aperture-coupled patch antenna that uses a single substrate. Indeed, for components including active devices, in particular, MMIC’s, the popularity of CPW has increased significantly in recent years because the advantages of CPW like wider bandwidth, smaller mutual coupling between two adjacent lines, and easier integration with solid-state active devices on one side of the planar substrate, thus avoiding via hole connections. Over the past few years, a considerable number of studies have been carried out on the linearly polarized antennas, loop antennas, and slot antennas [2], but only a few attempts have so far been made at realizing antenna patch fed by CPW in the millimeter-wave region. In light of this, considering Manuscript received November 4, 1997; revised July 13, 1998. The authors are with the Personal Communication System Group, INRS- Telecommunications, Ile des Soeurs, Quebec, H3E 1H6 Canada. Publisher Item Identifier S 0018-926X(98)08904-2. Fig. 1. Layout of the test-patch antenna and feeder network. the recent development that shows that microstrip patch antennas can be coupled with CPW transmission lines [3]–[7] via a slot in the ground plane, a new structure of the printed antenna fed by CPW that conjugates the advantage of aperture-coupled microstrip antenna and the wide range of flexibility is proposed using the innovation that uniplanar technology offers. Indeed, the patch antenna is an extremely useful configuration for millimeter-wave wireless applications. When the patch is excited by CPW, a CPW to slotline junction is required to ensure the antenna works at high efficiency. The paper proposes the use of the CPW stub patterned on the center conductor to obtain optimum matching. It is important to note that the design of CPW coupled microstrip patch antenna with the CPW series stub within the center conductor leads to greater field confinement resulting in suppression of spurious radiation emitted by this stub and provides both low loss and longitudinal symmetry whose eliminates the need for air bridges. This arrangement provides additional degrees of freedom compared to classical topologies resulting in extremely compact con- figuration. The feasibility of integrating this novel antenna topology on high-dielectric constant substrate , which is close to the dielectric constant of GaAs in millimter wave region is also demonstrated. The measured results shows the usefulness of the proposed antenna configuration and the effectiveness of uniplanar technology both in terms of performance and cost. II. ANTENNA TOPOLOGY As the popularity of the CPW transmission line has increased significantly in recent years, antenna elements that are suitable for CPW feed configuration have also become important. In light of this, design guidelines for the CPW-fed patch antenna is presented herein. The configuration of the proposed slot-coupled planar antenna is illustrated in Fig. 1. A rectangular microstrip patch is placed on one side of the substrate, while a slot fed by a coplanar line is arranged opposite to the patch in the ground plane on the other side of the substrate. A CPW stub patterned in the ground plane is used as matching network. Furthermore, the design of the aperture-coupled patch elements involves the following steps: first, the dimensions of the antenna patch are determined by a cavity model [2] to be resonant at the operational frequency of 38 GHz. The side length of the squared patch is found to be 1.1 mm. The width of the aperture (slot) is chosen to be 0.1 mm. It has to be large enough to 0018–926X/98$10.00  1998 IEEE