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The design and fabrication of a coupler with three reconfigurable output ports have been proposed. The output ports of the proposed coupler can be adjusted by varying the number of shorting pins. An antenna with a reconfigurable beamwidth has been also involved in this paper. The proposed antenna has a coupler and a 1 × 3 array rectangular patch. The beamwidth is set by the number of output ports. The simulation and experiment show the verification of the proposed coupler and beamwidth variation of array antenna. The broadest measured beamwidth was 66.2° and the sharpest measured beamwidth was 24.1°.

This paper discusses the characteristics and effects of dielectric inner-supports on discone antenna for broadband RF test chamber, and the verification has been performed by simulation. Several design parameters such as the thickness of the gap support, the position of the side support, and the thickness of the side support has been analyzed. The thickness of the gap support affected the reflection coefficient. An effect of the offset of the side support from the center was slight below 3 GHz and significant above 3 GHz. The thickness of the side support did not affect the reflection coefficient or the gain much. The performance of the fabricated discone antenna was in good agreement with the simulated results. This investigation of a dielectric support effects could be used to design a commercial discone antenna for broadband RF test chamber, focusing on electrical performance and mechanical stability.

This paper proposes a reconfigurable microstrip diplexer, also known as a switchplexer, for use with single-switch operation of frequency band and output path. The proposed switchplexer is composed of a rectangular ring resonator and a switch on a shorting pin, which is inserted between the ring resonator and the ground plane. The rotated main current distributions occurring at different switch statuses provide the diplexer’s different operating bands and different output ports. The performance of the simply designed switchplexer is successfully demonstrated via simulation and measurement.

We propose a low-cost measurement technique of commercially available base-station antenna in a compact experimental setting, which may be considerably smaller than the far-field distance. An α-variable positioner was utilized with Fresnel-to-far-field transformation method. Compared with conventional near-field measurements, the technique described here allows for more rapid scanning and transformations. The experimental results show good agreement between the results measured at the far-field and that found using the Fresnel-to-far-field transformation. The experimental validity for commercial base-station antenna has been successfully shown for the first time as far as our knowledge, so that the proposed technique can be easily applied in small anechoic chambers, which are typically possessed by small-/medium-sized companies. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2617–2622, 2015

This paper presents a beam-forming reader antenna system for a new type of RFID based train position detection technology. The required beamwidth of the reader antenna is analytically expressed for different train speeds. The proposed antenna system consists of four rectangular patch elements and two switching couplers which are designed, without any impedance matching networks, for two different antenna modes. The switching coupler is a rectangular quadrature coupler with Pin diodes connecting its center line and the ground plane. The beamwidth of the antenna when the diodes are off and on is and , respectively. The proposed antenna system will be used for a real train test in the near future.

This paper presents a novel frequency-tunable open-ring microstrip antenna for radiated-power measurements in a real environment. In order to elevate the probing up to a few tens of meters, the antenna must have light-weight, narrow-bandwidth, and broad side-beam characteristics. An open-ring microstrip antenna is a good candidate for satisfying these requirements. Varactors are attached to tune the operation frequency, but the conventional position, which is in the vicinity of the ring-opening, shows a much lower gain and poor cross-polarization level. This paper proposes a superior position for the varactors, which is the upper-edge of the left and right sides of the ring. The reflection coefficient (S11) in the simulation and experiment demonstrated that the resonant frequency can be increased by increasing the supply voltage. The proposed tunable antenna can be utilized in the probing apparatus to measure the radiated power.

We propose a way to measure the absorber reflectivity at a low cost. Only one simple antenna with a small radiating aperture and a frequency-domain instrument are utilized. The previously used equation for calculating the reflectivity of an absorber is inaccurate, and, therefore, a new equation is derived based on multiple reflection analysis and three test models. Notably, the reflection coefficient of the antenna is included in the derived equation. The accuracy of the proposed method is proven through simulation and measurements. It can be easily applied to a product examination by absorber manufacturers and customers owing to its advantages of simplicity, cost effectiveness, and non-cutting examination.

This article proposes a reconfigurable microstrip antenna that changes its polarization with only a single switch at a single frequency band. The antenna consists primarily of a square ring and a square patch, with a foam layer. When the connection status between the square ring and the ground is changed between shorted and open status, the linear polarizations are switched. The resonant frequency of the antenna using a single switch reported previously has been shifted, but the proposed antenna in this article exhibits a fixed resonant frequency. The design principle is as follows: The square-ring printed on the dielectric substrate has inherent narrow bandwidth, but we found that its polarization-switching characteristics existed over the broad band. The square patch is placed above the square ring, and it provides a broad bandwidth while maintaining polarization diversity. The performance of the antenna is successfully demonstrated via simulation and measurement. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:57–60, 2014

In this article, we describe a frequency-tunability procedure for a waveguide single-pole bandpass filter adopting a split-ring resonator (SRR). The tuning procedure is, in this article, achieved by inserting a metal or ferrite tuning screw, depending on the desired tuning direction. The screw plays a role in the adjustment of the magnetic field passing through the center of the SRR. The discrepancy between the proposed waveguide filter and the evanescent-mode filter has been included. The aperture size of the waveguide filter is decreased by about 70% in comparison with conventional waveguides. The wide tuning bandwidths and lower insertion losses obtained by both simulation and measurement confirm the validity of the proposed technique. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1649–1653, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27618

This letter describes a broadband planar antenna embedded in LTE700/GSM handheld terminals. The antenna consists of a T-shaped strip fed by a 50-Ω coaxial cable and a shorted strip excited by capacitive coupling. The capacitively coupled shorted strip shows the resonance at the lower frequency band, and the T-shaped strip presents good matching at the higher frequency band, because the characteristics of input impedance are affected by the capacitive coupling. The proposed antenna was simulated and fabricated. The measured bandwidth based on 3:1 VSWR was 0.62–1.53 GHz, which covers the frequencies used for LTE700, GSM800/850/900 mobile communications as well as the military applications. This antenna would be also useful for broadband wireless communications using the technique such as software-defined radio or cognitive radio. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26211

This paper describes the 6-way power divider to be used as a feeding structure of the waveguide array antenna generating the plane wave at the near distance. The SMA connector has been connected at the center of the power divider in order to feed the radiating element. The six output ports made of waveguide are positioned on the peripheral of the divider. This paper proposes the method utilizing the inductive post in order to decrease the return loss. The height of the feeding pin, the diameter of the inductive post, and the distance between the feeding pin and inductive post have been investigated, and as a result, the power divider has been optimized. The simulated and measured results show the low return loss of about -40 dB. The calculated and measured transmission coefficients are -7.78 dB and -8.06 dB, respectively. The output power of the six waveguide port show equal-amplitude and equal-phase distribution. Since the power divider proposed in this paper can be expanded to the divider having several output ports, it could be easily applied to the various array antennas.

The small anechoic chambers built by many small-/medium-sized companies and universities present difficulties in testing electrically large antennas because the chamber size cannot satisfy the far-field criterion of large antennas. In this paper, a method for Fresnel-region measurement on a cylindrical surface with variation of the measurement height is proposed and verified by both calculations and experiments. We implement the proposed method using a direct far-field measurement system by adding a few supporting structures. The results show good accuracy.

We describe a measurement technique to characterize the equivalent isotropically radiated power (EIRP) of electrically large wireless equipment in a compact environment. A modified phase-measurement method was proposed and, thus, the separation of the signal generator and radiating element was not required during the measurement. A Fresnel-to-far-field transformation was used for the fast measurement time in a compact anechoic chamber. An experimental verification of the method was carried out in a compact anechoic chamber, where the source-detector separation was approximately 1/5 of the far-field distance. The measured magnitude and phase pattern exhibited only a small error. The EIRP obtained using a Fresnel-to-far-field transformation was compared with a reference value, and the error was within 0.5 dB.

An artificial magnetic conductor using the split-ring resonators (SRRs) printed on conductor-backed dielectric substrate is presented. The simulation and measurement verify that the magnetic conductor is successfully accomplished around the resonant frequency. As an antenna application, the characteristics of a horizontal wire antenna placed above the SRR array, as well as a conducting ground plane and a grounded dielectric slab, are investigated and compared. A maximum gain of 4.34 dBi is obtained for the wire antenna above the SRR array. The results confirm that the split resonators can successfully be used to replace the antenna ground plane in order to improve their performance. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 329–334, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21341

In this paper, we describe a fixed-beam broadband pla- nar 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- sured bandwidth is found to be more than 7.1% from 40.5- 43.5 GHz. The main beam directions are broadside over all frequencies. The maxi- mum measured antenna gain is 30.2 dBi at 42.0 GHz. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 283-287, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20279

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 article, we propose a new method for predicting the electromagnetic field in the inner area between the source antenna and the antenna under test, utilizing a far-field measurement system. In particular, we describe the selection of the optimum number of data to be measured, as this is critical to the accuracy. The fields are measured and then transformed into the field in the inner area. The accuracy was verified by simulation and experiment. This inward transform method can be used for determining the worker safety area against high-power microwave systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2032–2034, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24541

A simple and effective method of echo cancellation in a nonanechoic chamber with a metal plate is presented in this study. The antenna measurement using standard gain-horn antennas was measured from 3.0 to 3.7 GHz in a fully anechoic chamber with intentionally generated contributions. As a result, when the frequency range is very narrow as one/time delay, the proposed method has better performances than the earlier echo-cancellation techniques such as fast Fourier transformation (FFT) and matrix pencil (MP)-based method.

In this paper, the technique of the reactive near-field to near-/far-field transformation has been proposed. The different thing compared with the previous work is that the environment of the semi-anechoic chamber with the ground plane was assumed during the transformation. The sources of electronic device are reconstructed from the detected reactive near-field. And then, the composite array source using the image theory is built, and then the transformation from the composite source to the near-/far-field are performed. For the verification, the simulated results have been utilized, and their results show small errors. Therefore, the proposed technique in this paper could be applied to predict the radiated field at 3 m or 10 m without the expensive large semi-anechoic chamber.

An X-band six-way waveguide power divider using the metallic wall is proposed. For good impedance matching over the broad frequency band, the metallic wall having an inductive component is positioned on the side of the output waveguide. Simulated and measured results show low return loss and low insertion loss. Compared to the waveguide using an inductive post, the proposed divider has much broader bandwidth, 14.8 and 10.2%, from simulation and measurement, respectively. This broadband waveguide divider can be used in many microwave and millimetre-wave applications.

A 24/spl times/24 slotted-waveguide array antenna is presented in the paper. The subarray concept is introduced to provide a broad reflection and gain bandwidth. A waveguide feed network is proposed to feed equal amplitudes and equal phases to the subarrays; it is composed of two layers, and is thus more compact and simpler than conventional feed networks. The subarray is made up of the feeding waveguide coupling slot, radiating waveguide and radiating slot. The measured reflection bandwidth is 5.5% (VSWR /spl les/2.0) and 9.5% (VSWR /spl les/2.7). The antenna gain varies within 2.1 dB over 4 GHz (9.5%). The maximum gain is 33.8 dBi at 41.5 and 42.5 GHz.

A low-cost broadband millimetre-wave planar 30×30 array antenna is presented. The antenna is fed by a microstrip feed network in the H-plane to decrease fabrication costs, and a waveguide feed network in the E-plane to reduce the feed line loss. The waveguide and microstrip feed network are coupled through the proposed slot pair. The slots are placed one quarter of a guided-wavelength distance apart, so that the reflected waves from the slots cancel each other. A conductive bar is laid above the slots to increase the coupling, which increases the antenna gain by about 1 dBi. The maximum gain is 30.5 dBi at 41.5 GHz. The measured bandwidth is as broad as 7.1%.