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This letter proposes a measurement technique for the relative phase of a 5G new radio (NR) signal. The total radiated power (TRP) is measured to evaluate wireless equipment. However, this cannot be implemented using the near‐field measurement system owing to the digitally modulated signal. The relative phase detected by using a vector network analyser (VNA) changes significantly owing to the fast change in the signal in the time domain and the imperfect synchronisation of internal receivers of VNA. This study calculated the cumulative distribution function and medium value for the signal from the multi‐probe measurement system. The detected phase agreed well with the exact value obtained from the continuous wave signal. The proposed technique can be used for TRP calculations using the near‐to‐far field transformation.

We investigated the impact of window penetration loss (WinPL) on the frequency dependence of building entry loss (BEL) from 3.5 to 24 GHz. The WinPL characteristics of an ideal double-glazed glass and an actual double-glazed window were simulated and measured on-site, respectively, and both results showed almost the same oscillatory characteristics with respect to the frequency changes that occurred due to the impedance oscillation of the double glass-like multilayer dielectrics. Two BEL measurement scenarios were examined to analyze the frequency dependence of BEL in a traditional office building with double-glazed windows identical to those analyzed in the on-site WinPL measurements. The experiments included a complex propagation route (the first scenario) from the facade of the building to the corridors through windows and offices and a simple propagation route (the second scenario) through only windows lateral to the building. The two main findings are (i) BEL showed strong frequency-dependent behavior regardless of the propagation route and (ii) the WinPL characteristics of the outer double-glazed window were the main contributors to the frequency dependence of BEL.

In this paper, we present experimental transmittance data at 0.75, 1, 2, 3, 4.5, 6, 10, 18, and 24 GHz from urban and rural environments. All measurements were performed under line-of-sight (LoS) conditions. Reach distances were extracted using the multifrequency alpha-beta- gamma model. Normalized individual and combined ratios were plotted against the frequencies and compared between the two environments. Although our data were obtained under LoS conditions, they can be used to predict the service area over a wide frequency range and establish a public policy for mobile communications.

Wireless communication technologies are expected to become essential in future self-driving vehicles. This study presents an antenna for vehicle wireless communication with a bandwidth of 75 MHz at a Wireless Access in Vehicular Environment frequency of 5.885 GHz. To compensate for the backward link path loss from the vehicle interior and passengers, the antenna is designed to have asymmetric gains of 0 and 6 dBi at 0° and 180°, respectively. The antenna is validated through an outdoor road test. We measured the received continuous-wave (CW) power, received signal strength indicator, and packet-delivered ratio (PDR) of the digital signal under vehicle-to-vehicle communication mode. Similar power is received in both the backward and forward scenarios. The forward and backward PDR are also similar.

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 describes a beam-steering antenna having tunable beamwidth implemented by using Rotman lens and power combiner. Conventional Rotman Lens array antenna has only the fixed beamwidth. However, the proposed array antenna has the variable beamwidth. The operating frequency is 3.55 GHz. The input power can be fed into Rotman lens through the power divider or directly, depending on the synthesizing beamwidth. The simulation results showed the steering beam with tunable beamwidth. Designed antenna and Rotman lens were fabricated.

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.

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.

This paper proposes path loss characteristics for urban high-rise environments based on 0.75, 1, 2, 3, 4.5, 6, 10, 18, and 24 GHz measurements. We conducted a measurement campaign using 10- and 2-m-high omnidirectional antennas for transmitting (Tx) and receiving (Rx) sites, respectively. This paper reports the path loss and the parameters of the alpha-beta (AB). The proposed model would be useful for predicting electromagnetic fields located in real environments, and for planning cellular communication services.

An effect of a building entry loss (BEL) on incident angles has been investigated in a traditional office building from 3.5 to 24 GHz band. The BEL was measured at three different positions in the window, the office center, and the corridor, moving a receiver (Rx) from 1 m away from the window (W) to the inside on the 6th (6F) and 9th (9F) floor of the building. As the Rx location moves from the window (W) to O and C inside of the building, the BEL increases and its slope for the azimuth angle decrease on the 6F, where the signal is directly incident. This tendency was not observed in 9F with an elevation angle of 12.8°. These results reveal that there is a breakpoint and propagation mechanism is different at each Rx location. For cumulative distribution function (CDF) of the BEL, as the frequency increases to 3.5, 6, and 10 GHz, the BEL increases. However, it decreases at 24 GHz at all Rx locations and all elevation angles because of frequency dependency of the input impedance of the air dielectric interface in the double layered-glass window. As the elevation angle increases from 0 to 12.8° in the window, the BEL increases from 4.2 to 11.7 dB at 50 percentile level of the CDF.

Communication between moving vehicles is very important for safety. In this paper, a bidirectional antenna that can be installed inside a vehicle is proposed and tested in a real vehicular environment at 5.8 GHz. The forward link and backward link seated by two persons and three persons were compared in terms of received RF power and the peak-to-average power ratio (PAR). It was found that, even with three persons, the power link fulfilled the communication requirements using the proposed antenna.

In this Letter, novel asymmetric coupled lines are proposed to suppress common-mode (CM) noise in bent differential lines. Based on the concept of the relative permittivity of a single microstrip line, the width of the outer line is made smaller than that of the inner line in bent differential lines to reduce the time skew and the other design parameters are adjusted to account for the differential impedance. To verify the improvement afforded by the proposed method, the simulated and measured results of the proposed structure were compared with two different designs; the conventional bent differential lines and the compensated differential lines using a serpentine inner line. The results of the proposed method show better signal integrity than the other methods.

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.

A feeding antenna that uses a rectangular waveguide with a patch on it to equalise the principle planes is proposed. The patch is printed on a substrate grounded with shorting pins. Typically, corrugated horn antennas are used for feeding antennas, but they are expensive because of the complex fabrication process. In comparison, the proposed antenna is inexpensive because it uses a rectangular waveguide and a dielectric substrate. The simulation and experimental results gave similar 10 dB beamwidths, while the beamwidth of the conventional waveguide was markedly different. The proposed antenna could be used as a feeding antenna for reflectors at low cost.

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.

A single-layer polarization-switchable frequency-band-fixed microstrip square-ring antenna was developed. The copolar plane of the radiation pattern was reconfigured with a single-switch, but the resonant frequencies were identical. A microstrip square-ring antenna was adopted, and the lateral and vertical widths of the microstrip ring were tuned to agree the resonant frequencies of the unloaded or loaded antenna. A single-layer dielectric substrate was used instead of a latest three-layer configuration. Antenna impedance was optimized to a value between those of the loaded and unloaded antennas. The proposed antenna exhibited single-switch polarization–reconfiguration on a single-layer substrate, and could thus be used in mobile communications and microwave imaging systems. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1874–1879, 2014

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 letter proposes an open-ended waveguide antenna with a single split-ring resonator. In contrast to the waveguide antennas incorporating multiple rings reported in a previous study, which exhibited narrow bandwidth, the proposed antenna uses only one ring to achieve broader bandwidth while keeping the aperture small. A single ring has a relatively low quality factor compared to multiple rings. The simulated and measured fractional bandwidth was 4.13% and 4.03%, respectively, which is much broader than the fractional bandwidth of about 1% demonstrated in a previous study. This simple technique can be used in many applications that require small apertures including near-field probes and array elements.

Generally, antenna radiation patterns are measured in an anechoic condition so that the presence of undesired reflections does not skew the final measurements. The objective of this communication is to search for methodologies which can extract meaningful approximate results from non-anechoic measurements. In other words, how to process the reflection contaminated data and extract valuable information when one does not have a good anechoic room and performs measurements with various undesired reflections present in the data. The Chebyshev polynomials are used to extract from the data collected under non-anechoic environment and generate a radiation pattern for the same antenna radiating in free space conditions. The problem with this method is that some a priori information is required about the environment. Measured data has been used to illustrate the applicability of this new methodology and its improved performance over the FFT based methods.

In this paper, Quad-Band small antenna for GSM850, GSM900, DCS1800, DCS1900 is designed and fabricated. The antenna achieved the size reduction of over 67.9 % than the conventional PIFA(Planar Inverted-F Antenna) by using a MD(Magneto-Dielectric) material. A simple feeding microstrip line is used to feed the antenna from a coaxial line, which is capacitively coupled to the grounded patch structure for broadband characteristics. The impedance bandwidth the proposed antenna shows good results as broadband characteristics of 1341 MHz (801 ~ 2142 MHz) in VSWR ) and the gain is -6.67 ~ 4.25 dBi in the operating frequency.

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.

We propose a frequency-tunable waveguide antenna with a size-reduced aperture. Up to now, waveguide antennas with split-ring resonators have exhibited narrow-frequency bandwidths. To expand the operating frequency band, the resonant frequency of a split-ring resonator is tuned by adjusting the capacitance of the gap. A capacitor-loaded split-ring resonator is simulated and experimentally tested to validate its performance, and a varactor-loaded split-ring resonator is then investigated. The effective capacitance of the varactor-loaded split-ring resonator is changed by varying the external dc voltage. The tunable frequency range extends from 1.96 to 2.36 GHz (a fractional frequency range of 18.5%). The simulations and experiments yield good results for the reflection coefficient, radiation pattern, and gain. The proposed antenna retains the 70% aperture reduction of previously developed split-ring-resonator-loaded waveguide antennas.

The far-field pattern and gain obtained using the far-field measurement method can be highly accurate when the distance between the source antenna and the antenna under test (AUT) satisfies the Rayleigh far-field criterion. In this letter, we propose an improved Fresnel region measurement method that can be applied in a shortened distance between two antennas. The many Fresnel fields required are captured by changing angle phi of the scanning plane. This scanning involves rotating the roll positioners of the source antenna and the AUT in the same direction and by the same amount, and rotating the azimuth positioner in the horizontal plane. The radiation pattern and gain from the simulation and experimental measurements agreed closely with the reference far-field pattern and gain. The proposed antenna measurement method in Fresnel region by phi-variation scanning can be easily applied to most popular far-field measurement systems without any additional cost.