In this paper, we describe a fixed-beam broadband planar antenna array at millimeter-wave frequencies. The antenna is fed by waveguide-feed and microstrip-feed networks. In order to ensure fixed beams and a broad bandwidth, a subarray concept is introduced. For efficient coupling, a novel waveguide-to-slot transition consisting of a slot pair and a narrow conductive bar is proposed. Simulated and mea- INTRODUCTIONWith the growth of millimeter-wave communications, especially broadband multimedia wireless services, the demand for a lowcost broadband planar-array antenna has increased. Although microstrip patch antennas with a microstrip-feed network are widely used because of their low fabrication cost, they have serious problems in millimeter-wave large-array applications, such as large feed-line loss and gain degradation [1]. In contrast, slottedwaveguide array antennas have low loss and high efficiency, but high fabrication costs [2]. To obtain both low cost and low loss, standing-wave waveguide/microstrip feed networks have been reported [3, 4]. However, the arrays fed by these standing-wave feed networks have a very narrow bandwidth because the peak position of the E-and H-fields of the standing wave shifts with the operating frequency. Another problem of standing-wave arrays is the frequency-dependent main-beam direction. These characteristics restrict their application within a narrow band [5].This paper presents a beam-fixed broadband array antenna with high gain operating at 40.5-43.5 GHz. To reduce the feed-line loss, the antenna is fed by a waveguide-feed network in the E-plane direction. The microstrip-feed network is distributed in the H-plane direction in order to decrease fabrication costs. The two feed networks are coupled using the waveguide-to-microstrip transition proposed in this paper. The proposed transition consists of a slot pair and a conductive bar and is more efficient than a conventional transition. We also introduced the subarray concept, which widens the reflection bandwidth and fixes the main-beam direction for variant frequencies. The whole array is divided into four subarrays that consist of eight coupling slots and 30 ϫ 8 antenna elements. Figure 1 shows the geometry of the proposed waveguide-to-microstrip transition. The incident wave from Port 1 is coupled through the slot pair and propagates toward Ports 2 and 3 where the microstrip feed network is attached. The slot pair consists of two center-inclined slots that are placed equidistant from the center of the slot pair. The slot is 3.3 mm in length and 0.6 mm in width and is etched on the ground plane of the substrate. The etched ground plane also serves as the upper conductor plate of the waveguide. The dielectric constant of the substrate is 2.2 and its height is 10 mil. Figure 2 shows the ratio of the coupled power to the input power for various slot spacings d. The simulation has been performed using Ansoft's finite-element-method simulator HFSS [6]. The coupled power is calculated as sum of the square of scatterin...

This study presents a very short pyramidal horn antenna for monitoring the radiation characteristics of mobile base‐station (BS) antennas operating in the long‐term evolution (LTE)/cellular band. The proposed short pyramidal horn is integrated with metal strips/rods to overcome deficiencies of the shortened horn, especially in its front‐to‐back (F/B) ratio. The proposed short horn antenna improves the average F/B ratio by at least 8 dB in the frequency range from 690–960 MHz by controlling the edge diffraction. The total length of the antenna, including a waveguide flange, is only approximately 0.6 λ at 800 MHz. The proposed antenna also retains good characteristics such as a monotonically increasing gain, wide bandwidth, and a good purity of polarisation. The proposed antenna can replace the dipole antenna as a reference gain antenna for both indoor and outdoor measurement systems below the L‐band.

In this paper, a new bandpass filter inserting a microstrip‐line resonator between two ring dielectric resonators is described in an MIC environment. This filter is designed using the general filter design technique, and is analyzed using the FDTD method. The designed result shows good agreement with the experimental and simulated ones. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 319–322, 2001.

In this paper the problem of rectangular microstrip antenna printed on a uniaxial substrate with a super-strate loaded is treated. The effects of superstrate on a complex resonant frequency of a rectangular microstrip antenna on a uniaxial substrates were studied. Special constitutive relations are used in describing the uniaxial properties of matrial, as the Dyadic Green's Function can be formulated. Electromagnetic fields and boundary conditions in spectral region were used in finding Green's function. Using Galerkin's method in solving the integral equation, the complex resonant frequency of the antenna is studied with sinusoidal basis functions, which show fast numerical convergence. Numerical results jndicate that both resonant frequency and bandwidth are transformed on a substrate loaded by substrate.