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Slow wave and localized field are conducive to terahertz (THz) modulators with deep and fast modulation. Here we propose an electrically controlled THz modulator with slow wave effect and localized field composed of a high electron mobility transistor (HEMT) integrated metasurface. Unlike previously proposed schemes to realize slow wave effect electrically, this proposal controls the resonant modes directly through HEMT switches instead of the surrounding materials, leading to a modulation depth of 96% and a group delay of 10.4ps. The confined electric field where HEMT is embedded, and the slow wave effect, work together to pave a new mechanism for THz modulators with high performance.

A transmissive metasurface polarization beam splitter (MPBS) with three-layer dielectric substrate was designed to meet the application requirements of polarization beam splitting devices. The micr...

A high-resolution near-field focusing metasurface lens (MSL) was proposed to meet the high-resolution and miniaturization requirements of focusing devices in the Ka-band passive millimeter wave (PM...

In this Letter, we propose an approach to generate high-purity orbital angular momentum (OAM) vortex waves using an amplitude-and-phase metasurface (APM). By varying the square split ring opening and orientation angles, the cross-polarized reflection response of the proposed structure can yield full phase and amplitude coverage. Based on the traditional phase-only metasurface (POM), the Chebyshev synthesis method (CSM) is applied to array the metasurface amplitude distribution. Metasurfaces with modes l of 1, 2, 3, and 4 are designed. Compared with the POM, the APM can effectively improve the vortex beam quality and OAM mode purity. The measured results agree well with full-wave simulations. The presented method provides a new, to the best of our knowledge, way to design high-purity OAM generators based on metasurfaces.

A novel dual-wideband dual-polarised magnetoelectric (ME) dipole antenna for the fourth generation (4G)/fifth generation (5G) microcell base station is proposed. Using a pair of orthogonal ME dipoles and Γ-shaped tapered cross feeding lines, the initial antenna achieves dual-band and dual-polarised. Then, four U-shaped gaps, added in electric dipoles, effectively extend the lower impedance bandwidth. Finally, a circular parasitic patch with capacitive properties is innovatively loaded above the ME antenna, which obviously reduces the high-resonant frequency from 5.5 to 4.9 GHz. Meanwhile, a box-shaped reflector is employed to achieve stable gain and radiation patterns. As a result, the measured results show the good dual-wideband performance of 52.4% (2.14–3.66 GHz) and 7.4% (4.68–5.04 GHz) with voltage standing wave ratio (VSWR) 25 dB) and high gain (9.5 and 5.5 dBi, respectively). In addition, a stable radiation pattern with a half-power beam width of 63.5 ° ± 6.8 ° and good cross-polarisation discrimination (>20 dB) on the E-plane is realised over these two bands.

In order to improve the sensitivity of liquid dielectric constant measurements, a liquid dielectric constant sensor based on a cubic container structure is proposed for the first time. The cubic container, which consists of a dielectric substrate with a split resonant ring (SRR) and microstrip lines, can enhance the electric field intensity in the measuring area. High sensitivity can be obtained from measuring the dielectric constant with the characteristics of the structure resonate. The research results show that the resonant frequency of the sensor is shifted from 7.69 GHz to 5.70 GHz, with about a 2 GHz frequency offset, when the dielectric constant of the sample varied from 1 to 10. A resonance frequency offset of 200 MHz for the per unit dielectric constant is achieved, which is excellent regarding performance. The permittivity of oil with a different metal content is measured by using the relation between the fitted permittivity and the resonant frequency. The relative error is less than 1.5% and the sensitivity of measuring is up to 3.45%.

In this article, several miniaturized microstrip fifth-order lowpass filters with structure of unit artificial transmission line are presented. Reactive elements including inductors and capacitors are constructed by microstrip structures directly by parameter extraction from electromagnetic simulation. A transmission zero in stopband can be achieved by inductors and capacitors (LC) series-resonant circuit composed by parallel-plated capacitors and connecting lines. Meanwhile, loading interdigital capacitors would bring in another transmission zero. In comparison, fifth-order Butterworth and Chebyshev lowpass filters with one and two transmission zeros are fabricated, respectively, to verify the extra transmission zero effect caused by LC shunt resonant-circuits with interdigital capacitors. The proposed lowpass filters are compact and their sizes occupies less than 40% of conventional microstrip lowpass filters. The simulated and measured results demonstrate good agreements between them, which ver...

In order to solve the problem of mono-working frequency and monofunction of traditional metasurface, a design approach for realizing dual-band dual-function metasurface based on beam polarization characteristics is proposed. Based on the principle of the dipole that it can only induce the parallel electric field while maintaining unsensitive to vertical electric field, a T shaped unit structure consist of two dipole is designed, which could realize the flexible control on reflecting phase and operating frequency independently. According to the generalized Snell's law and the spiral phase factor required to generate orbital angular momentum (OAM) electromagnetic waves, the two dipoles are respectively coded to construct 3-bit metasurfaces. Numerical simulation and measured results show that the metasurface designed according to the above method has beam deflection function at 18 GHz when the x-polarized wave is incident, and the vortex electromagnetic wave can be generated at 32 GHz when the y-polarized wave is incident, which proves the correctness and effectiveness of the proposed method. The proposed design method can be extended to the terahertz band or even the optical band. The metasurface designed according to this method has potential application value in multiple input multiple output (MIMO) communication systems.

In this article, a broadband dual-polarized dipole antenna for mobile communication systems is proposed. The design is based on improvements to conventional bowtie dipole antennas, thereby simultaneously achieving wider bandwidth and a more compact size. The antenna consists of a metallic plate reflector and a pair of orthogonal planar dipoles with U-shaped slots, which are separately excited by T-shaped feeding lines. The application of U-shaped slots and T-shaped feeding lines effectively extends the impedance bandwidth. Additionally, using a new approach of adding metallic cylinders to each dipole improved impedance matching. Experimental results indicated that the designed dual-polarized antenna achieved a notably wide bandwidth (1.58–2.82 GHz). Further, the measured isolation between the two ports was better than 30 dB and cross-polarization level was less than –25 dB on the axis. Moreover, the antenna had stable radiation patterns with half-power beam width of 65° ± 5° on the horizontal plan...

A broadband dual-polarized base station antenna is proposed in this paper. The antenna consists of loop cross-dipoles, Y-shaped coupling feeding lines, and a metal box reflector. An equivalent circuit model including a signal flow diagram is established to analyze the mechanism of the proposed antenna in detail. Moreover, the Y-shaped coupling feeding lines are introduced to control the coupling with the antenna to achieve broadband and good impedance matching. The prototype of the antenna is fabricated and measured. The measured results show that the antenna with simple structures can operate at the band of 3.2&ndash, 5.22 GHz (48%) with high port-to-port isolation (35 dB) and stable gain (9 &plusmn, 1 dBi). The measured results show good agreement with simulated results, especially in cross-polarization discrimination ratio (&gt, 27 dB) and the half power beam width (61&deg, &plusmn, 3&deg, at the E-plane, 68&deg, at the H-plane). In summary, the proposed antenna could be a good candidate for 5G sub-6 GHz base station applications.

In this paper, aiming at the problems that the DMR mobile terminal equipment susceptible to noise signal interference, a frequency synthesizer with high integration, low phase noise function is designed by using fractional phase locked frequency synthesis technology. Based on the phase noise model of the phase locked loop synthetic frequency source, it is concluded that the selection of loop bandwidth determines phase noise performance of the frequency source by analyzing the characteristics of the phase noise transfer function of each noise source. The test results show that the phase noise is better than -95dBc/Hz@lkHz within the frequency range of 400MHz-470MHz.

A wideband filtering power divider (FPD) with wide rejection bandwidth and good isolation is presented, based on conventional Wilkinson structure. Parallel coupled lines and two pairs of open-circuit stubs are used for achieving bandpass filtering response and enhancing the performance of the rejection bandwidth. Furthermore, by properly choosing two resistors between two pairs of open-circuit stubs allows good isolation performance. Measured results indicate that the FPD operates at 2.35 GHz ( f 0 ) with a − 20 dB bandwidth of 55.3%. In the upper stopband range from 3.7 to 8.8 GHz (3.74 f 0 ), the minimum rejection is 20 dB. Within working band, the isolation between the output ports is higher than 24 dB. In addition, ultra-wide isolation better than 20 dB from DC to 10 GHz is obtained.

Based on the definition of the azimuth angle of the wave vibration and the reflection theory of the reflectance theoretical calculations of the multilayer optical films with Takashashi model, the dependences of the polarization azimuth angle of the reflected wave from the 1/4 wave piled HR thin film on the temperature, the incident wavelength and the incident angle are discussed. The research results show that the temperature, the incident wavelength and the incident angle of the wave have a significant effect on the polarization azimuth angle of the reflected wave. By the theoretical and experimental analysis, it is pointed out that the phenomenon of the change of the polarization azimuth angle with the temperature can be used to study the weak absorption of the optical thin film and can obtain higher sensitivity under the optimal conditions. The proposed novel method enriches the theory of the photothermal technology.

A novel wideband dual-polarized printed dipole antenna fed by two integrated feeding networks is presented. The feeding network, a kind of compact halfwave balun, delivers equal amplitude (within 0.1 dB) and 180° (±5°) phase difference between the two output ports from 1.65 to 2.8 GHz. By employing an H-shaped slot in each arm of the dipole, wide impedance bandwidth has been obtained. Experimental results show that the proposed antenna can operate from 1.7 to 2.7 GHz with low voltage standing wave ratios ( 25 dB) and high isolation (>31 dB) are also achieved over the entire bandwidth. Moreover, stable radiation patterns and low back lobes are obtained by using a modified reflector.

In this paper, a unit of microstrip artificial transmission line (ATL) with right-angled triangle shape based on stepped-impedance structure is proposed. The transmission line consists of stepped-impedance lines folded into right-angled triangle shape to reduce size of transmission lines. The interdigital capacitors placed in the middle of triangle structure have a function of harmonics suppression. Compared with conventional transmission lines, the ATL has a more compact size, and occupies area of 28.2 mm × 12.5 mm. The ATL works at a center frequency of 0.9 GHz, and the bandwidth can achieve 293.33% bandwidth, ranged from 0 GHz to 2.64 GHz. Simulated results show that it has a good performance with high return loss and low insertion loss. Meanwhile, the harmonics suppression is efficiently obtained.

This paper studies the sampling method for interpolation/extrapolation of electromagnetic response in time and frequency domains. To avoid sub-sampling or over-sampling, a new adaptive sampling method is proposed. With the proposed approach, the length of sampling depends on the required accuracy of interpolation/extrapolation, while its calculation format needs little modification. Finally, this adaptive sampling method is used to calculate the wideband electromagnetic response through interpolation/extrapolation, and some numerical results are given to prove the effectiveness of this method.

Object coated with plasma has stimulated great interests of many people because of its stealth capability. The study on a conducting cylinder coated with coaxial plasma is very much, but there are little works on a conducting cylinder coated with eccentric plasma. In this article, a model for a conducting cylinder coated with eccentric unmagnetized plasma is set up, the scattering cross section of the object cylinder is studied by adopting the superposition of cylindrical wave functions and the coordinate transformation, where these wave functions are the solutions of Maxwell's equations with boundary conditions in cylindrical coordinates. The results show that the radar cross section for a conducting cylinder coated with eccentric plasma in every direction decrease obviously with an increase of the distance between two eccentric axes, but is almost not impacted by electron–neutral collision frequency of plasma, and the backscattering cross section of the target reduce with the increase of electron densit...

The photothermal detuning technique (PTDT) is a novel photothermal technique and can be used to measure the absorption of the optical coatings, which utilizes the spectral shift of optical coatings caused by absorption-induced temperature rise. The measurement sensitivity depends on the slope of the spectrum band edge and the character of the probe beam, and is limited by the temperature coefficient of the reflectivity or transmission. Based on the preliminary study, the impact of the spectrum band slope and the probe beam character on the measurement sensitivity are detailed studied. Experiments are performed with a highly reflective coating. The results show that the measurement sensitivity is determined by the structure and the optical–thermal parameters. Appropriate wavelength, incident angle and polarization properties of the probe beam can improve the measurement sensitivity. The results provide a theoretical and experimental basis for the application of the photothermal detuning technique for absorption loss of the thin film.

The uniformity of optical coatings becomes more and more important as large diameter optical devices are widely used. Absorption loss in optical components, particularly in optical coatings, is a limiting factor in high-power laser applications. This article analyzes the main factors, which affect the spatial resolution of three techniques for surface absorption loss measurement, including the photothermal deflection technique, the surface thermal lens technique, and the photothermal detuning technique. The influence of the size of the heating and probe beam on the photothermal detuning technique is studied in detail. Experiments are conducted to study the photothermal signal of the photothermal detuning technique for absorption measurement of the optical coating point by point. The results show that the main factors, which affect the spatial resolution of imaging measurements for absorption loss of coatings, are the heating beam size and the step accuracy of the sample translation stage. The heating and probe beam sizes has a significant impact on the application of the photothermal detuning technique. Experimental result shows that the photothermal detuning technique can be used for imaging of absorption loss measurements of optical coatings. The results provide theoretical and experimental supports for further application of the photothermal detuning technique.

The industrial use of polyimide film is limited because of undesirable properties such as poor wettability. In the present paper, a new kind of equipment called water cathode atmospheric pressure glow discharge was used to improve the surface properties of polyimide films and made them useful to technical applications. The changes in hydrophilicity of modified polyimide film surfaces were investigated by contact angle, surface energy and water content measurements as a function of treatment time. The results obtained show good treatment homogeneity and that the variation trends of contact angles are different for polar and non-polar testing liquids, while surface energy and water content are significantly enhanced with the increase of treatment time until they achieve saturated values after 60 s plasma treatment. Also, the thickness of liquid layer plays an important role in plasma processing and directly affects the treatment effect. Changes in morphology of polyimide films were analyzed by atomic force microscope and the results indicate that surface hydrophilicity after plasma treatment are improved partly due to the increase in the roughness. In addition, polyimide films treated by plasma are subjected to an ageing process to determine the durability of plasma treatment. It is found that the hydrophilicity is still better than untreated ones though the hydrophobic character partly recovers after long-term storage in ambient air.