A hybrid-fed dual-polarized antenna with matesurface coverage is proposed in this paper, which can be used for 5G mobile communication base station antennas. By placing the two feeding ports on different layers of dielectric plates in an orthogonal manner, and using electromagnetic coupling and slit coupling for feeding respectively, the antenna can achieve inter-port isolation higher than 35 dB in the operating frequency band. In order to widen the bandwidth and obtain higher gain, the metasurface covering unit is loaded above the patch. The metasurface layer contains an array of 5 × 5 square patch units printed on the top surface of the dielectric plate. The measurement results show that the proposed antenna has an impedance bandwidth of 12% (3.24 to 3.66 GHz). In addition, the antenna obtains a stable gain of about 5.32 dBi at 3.5 GHz. The proposed antenna meets all the requirements of base station antennas and can be a promising candidate for application in 5G base station systems.
A novel wideband circularly polarized (CP) dipole antenna for RFID/WiMAX/WLAN applications is presented. A pair of crossed fan-shaped dipoles printed on both sides of the substrate are used as the primary radiating elements. The antenna achieves circular polarization by using a 90° phase shifted microstrip line between the dipoles. By changing the edge of fan dipoles into Minkowski fractal curve, miniaturization and wide bandwidth of the antenna can be realized. Besides, incorporating the U-slot into the fractal crossed dipoles can obtain a wider bandwidth. The test results show that the proposed antenna achieves a wide impedance bandwidth of 63.2% (1.9-3.7 GHz) for VSWR < 2 and a 3-dB axial ratio (AR) bandwidth of 42.9% (2.2-3.4 GHz). The maximum gain in the operating frequency band can reach 7 dBi. The proposed antenna has good radiation characteristics in both low and high frequencies, which makes it a candidate for applications of RFID, WLAN, WiMAX, and other communication systems.
This letter presents a compact constant absolute bandwidth (ABW) frequency tunable bandpass filter (BPF) with bandwidth and tuning range enhancement. The fundamental structure consists of two varactor-loaded step-impedance resonators (SIRs) and input/output feeding lines. By adjusting the position of varactors, the slope of coupling coefficient between the two resonators can bechanged easily, which is crucial to realizing constant ABW. The tuning range is improved due to the application of varactor-loaded SIR. To expand the bandwidth, interdigital coupling structures between varactor-loaded SIRs are adopted. Besides, source-load coupling is introduced, and two transmission zeroes (TZs) are generated on both sides of the passband to enhance the rejection level of stopband. The measured results show that the proposed BPF achieves a center frequency tuning range from 0.79 to 1.2 GHz (41.2%), and the 3-dB ABW remains 108 ± 5 MHz. The insertion loss (IL) is 1.8-2.2 dB, and the return loss is greater than 10 dB during the whole tuning range.
A low cost and compact chipless Radio Frequency Identification (RFID) humidity sensor with the size of 18 * 18 * 0.5 mm3 is designed for environmental humidity monitor. The sensor consists of a circular resonator and a rectangular substrate, which utilizes the polyvinyl alcohol (PVA) humidity sensitive material for relative humidity (RH) sensing. The PVA humidity sensitive material covers the sensor surface. The working principle of the sensor is that the change of environmental humidity results in the changing of dielectric constant of PVA and thus shifting of the resonant frequency of the sensor. The real-time humidity can be observed by monitoring the resonant frequency. The simulation results show that the humidity sensing range of the designed humidity sensor is 21.9% RH~52.5% RH, corresponding to the resonant frequency range of the sensor from 2.76 GHz to 2.51 GHz with the total offset 250 MHz. The maximum humidity sensitivity was 23.08 MHz/% RH within the monitoring range. The designed humidity sensor has the advantages of low cost, compact and simple structure, which is suitable for humidity monitoring in various complex environments.
This letter presents a compact ultra-wideband circularly polarized (CP) crossed-dipole antenna with enhanced axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW). It consists of four modified arms which are fed by vacant-quarter phase delay rings to excite CP radiation. Four parasitic elements are utilized rotationally between the dipoles and the reflector. Not only does inducing vertical currents on the parasitic patches excite additional impedance resonance to realize an ultra-wideband operating, but also reinforced radiation is obtained to improve the ARBW and HPBW. The experimental results show that the proposed antenna realizes a -10 dB impedance bandwidth of 134.3%, and a 3 dB axial-ratio (AR) bandwidth of 115.0%, while holding a compact volume of 0.25λL × 0.25λL × 0.09λL (λL: wavelength at the lowest operating frequency). Furthermore, an HPBW and ARBW of more than 110° and 160° are realized within a broad operating band of 67.5% and 55.0%, respectively.
Reconfigurable antenna arrays play a major role in the current and future wireless communication systems due to their multifunctional capabilities and many other advantages. Conventionally, the array pattern reconfigurations were usually achieved by controlling the excitation amplitudes and phases of all or most of the array elements which are generally costly and complex methods. In this paper, a simple method for controlling the reconfigurability of beam-patterns of the linear and planar arrays is presented. It can be easily switched between narrow and wide beams using thinned-elements strategy. First, the array elements are divided into three groups based on their locations namely central, middle, and outer elements. Their amplitude weights are chosen to be unity, adaptive, and zero respectively. To add some desired constraints on the array beam-patterns such as limited sidelobe level and specified nulls placement, the excitation weights of the middle elements are optimized such that an abrupt change in the array taper is avoided. This also avoids an undesired change in the sidelobe pattern. A genetic algorithm is used to perform such optimization so that the produced beam-patterns are best matched to the desired ones. Moreover, the size of the thinned region controls the resulting beam width.
The problem of defeating a swarm of unmanned aerial vehicles (UAVs) is of considerable importance to the modern warfighter. In recent studies high power radio frequency (HPRF) directed energy weapons (DEWs) have been shown to be suitable for this purpose. Hence there is a need to develop mathematical modelling frameworks to quantify HPRF DEW performance, especially when they are operating in a wideband or ultrawideband mode. Consequently this paper introduces a novel mathematical model, based upon a new interpretation of UAV vulnerabilities to HPRF DEW, which permits performance assessment to be undertaken. The key to this is to view each UAV through its vulnerabilities to HPRF DEW energy at given frequencies and analyse its impact on the lifetime of each of the UAVs. This results in the definition of an appropriate stochastic process to count the number of UAVs still active in the swarm over a given time interval. Consequently this permits the determination of minimum HPRF DEW power levels at given frequencies in order to guarantee likelihood of defeat of the swarm before it reaches the HPRF DEW source. Hence the results in this paper will provide a novel framework for determining the specifications of an HPRF DEW's required power distribution over target vulnerabilities to ensure a desired level of system performance.
In this paper, a novel dual-band series-fed array (SFA) has been proposed. By introducing a new dual-band series-fed network (SFN) consisting of uniform transmission lines (TLs) and C-sections, independent beam direction can be realized. The design procedure for the proposed dual-band SFA has also been presented in this paper. To validate the design method, a prototype antenna has been fabricated and measured. The experimental results verify the performance of the proposed dual-band SFA.
A highly packaged coupler using vertically placed inductors and capacitors (LC)-elements is proposed for 1 and 1.5 Tesla (T) magnetic resonance imaging (MRI) applications. The coupler is made on a 24-layer thickness low temperature co-fired ceramic (LTCC) substrate, and the full integration is reached by heaping up LC-elements in the vertical dimension. The coupler has a smallest reported size of only 0.0035 × 0.0021 × 0.001λg and a wide fractional bandwidth (FBW) of 44%. The measured in-band phase difference between the coupled and through ports and the amplitude imbalance are less than 91°±0.5° and 0.75 dB, respectively. Comparisons and discussions are also implemented.
This paper presents a coplanar waveguide (CPW)-fed tri-mode hybrid antenna that is suitable for quad-band applications. The antenna design is compact, measuring only 30×30 mm2, and consists of a zeroth-order resonator (ZOR) antenna, a torch-shaped monopole antenna, and a T-shaped slot antenna. The most significant feature of this design is its ability to provide three independent working modes, making it a hybrid antenna. By incorporating a Composite Right/Left-Handed Transmission Line (CRLH-TL) unit cell, the first mode is excited as a ZOR antenna, corresponding to the lowest resonance at around 1.57 GHz. The second mode relies on the torch-shaped monopole antenna with two resonances at about 2.5 GHz and 3.5 GHz. The third mode employs the T-shaped slot antenna with a resonance at around 5.5 GHz. Experimental results demonstrate that the proposed antenna exhibits a wide and multi-band behavior with impedance bandwidths of 60 MHz (1.56-1.62 GHz), 210 MHz (2.30-2.51 GHz), 370 MHz (3.40-3.77 GHz), and 1100 MHz (5.05-6.15 GHz). This antenna can not only support the current GPS/WLAN/WiMAX systems but can also be considered as one element of a multiple-input-multiple-output (MIMO) antenna array for the fifth-generation (5G) mobile communication in the sub-6 GHz frequency range.
A frequency selective absorber for harmonic absorption (HA-FSR) is proposed in this paper. It consists of a miniaturized frequency selective surface (FSS) for harmonic suppression and a circuit analog absorber (CAA) for harmonic absorption. The frequency selective rasorber (FSR) unit is 6.7 mm × 6.7 mm (0.129λ × 0.129λ, where λ is the free space wavelength of 5.8 GHz). The simulation and measurement show that the HA-FSR can generate a transmission band from 4.51 GHz to 7.47 GHz and a -10 dB absorption band from 11.96 GHz to 22.31 GHz, which covers more than 3 times of the main passband harmonic band. In addition, the FSR has good polarization stability and angle stability within 30˚ of oblique incidences under both TE and TM polarizations, which can be applied to electromagnetic interference shielding field and low-observable platforms.
This paper presents a novel test platform for passive intermodulation measurement on planar microwave circuits using a filter design strategy. A finger planar band-pass filter is proposed and optimized to have an evenly distributed stimulation field on the surface. The layout is optimized with symmetrical coupling lines from two directions, and the feed line is with a tapered transformer. A pair of T-type resonators is adopted to improve the flatness of the field distribution. In the application of this test platform, print circuit boards with different layouts are tested, and the passive intermodulation difference of different layouts can be differentiated. As this platform is with open space, the device under test can be easily changed without suspending the passive intermodulation test system, which can be applied in the production line to speed up the production quality inspection.
An ultra-compact band-pass filter is presented in this paper. The filter is designed to operate in the medical implants communication service (MICS) band ranging from 401 MHz to 406 MHz. The filter is designed on a Rogers RT/duroid substrate with εr = 2.94 and tanδ = 0.0012. The overall size of the proposed filter is only 30.6 mm x 18.5 mm (0.058λg x 0.035λg), making it suitable for compact, portable devices. An equivalent circuit model is also proposed for the analysis of the filter geometry. From the circuit model, it can be concluded that the filter exhibits the characteristics of a dual-composite right left-handed (D-CRLH) transmission line. This is also confirmed from the dispersion characteristics. The salient features of the proposed filter include ultra-compactness at low operating frequency, harmonic suppression of 3.7 times of the passband frequency, fractional bandwidth of 4.45%, and good roll-off rate of 297.6 dB/GHz in the lower stopband and 116.4 dB/GHz in the upper stopband.
A new miniaturized patch antenna based on a metal strip is proposed in this paper. The antenna is designed by adding a middle metal strip layer to the substrate of a traditional rectangular patch antenna. By increasing the length of the metal strip, the working frequency of the patch antenna can be continuously reduced without significantly impacting the radiation pattern. The simulation results indicate that as the metal strip length increases from 5 mm to 25 mm, the working frequency of the patch antenna decreases from 2.39 GHz to 1.84 GHz, and its gain decreases from 6.72 dBi to 5.4 dBi. Two antenna samples with metal strip lengths of 5 mm and 20 mm are fabricated. The experimental results indicate that their working frequencies are 2.64 GHz and 2.43 GHz, respectively. And the radiation patterns of two antennas are consistent with the simulated results. All results confirm the effectiveness of the proposed miniaturization method.
The quality of a honey can be affected by adulteration through the addition of often unauthorized substances such as sugar syrups or water. The water content in honeys is restricted to 20% according to CODEX ALIMENTARIUS. This research proposes a method which will allow to detect the water content in the honey directly in the jar. The method uses electromagnetic probing with several antennas around the jar. This method is based on the knowledge of the dielectric contrast between a pure honey and a honey containing different water contents. To validate this contrast, a campaign of dielectric measurements has been investigated on two different commercial honeys (H1 and H2) with arbitrary and controlled added water. The added water content in the honey has been varied from 0% to 15%. The experimental setup uses a coaxial transmission line with a sample holder. The frequency range extends from 100 MHz to 5000 MHz. The mixtures of honeys with water have been measured at an ambient temperature (25˚C).
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