In this paper, a new method for radar cross section (RCS) reduction of circularly polarized (CP) microstrip antenna array with small element spacing is proposed. By employing the element rotation technique and loading EBG structures, the in-band and out-of-band RCSs are reduced simultaneously despite the extreme small space between array elements. The simulated results show that the proposed antenna has an average RCS reduction over 10 dB in the X-band for x-polarized and y-polarized incident waves impinging from normal direction compared to the original CP microstrip antenna array, indicating a fractional bandwidth of 40%. The maximum RCS reduction is over 25 dB. Meanwhile, the radiation performance of the proposed antenna array is kept.
This paper presents a testing scheme for the steel corrosion in reinforced concrete based on near-field effect of meter wave. The physical mechanism of the near-field method was introduced, and the structure of the measurement device was presented in detail. The electromagnetic field near the steel bar buried in the concrete structure was simulated by the finite difference time domain method. The simulated data show that the mean radiation power decreases monotonously with the increase of the corroded depth of the steel bar, and the corroded area is promising to be imaged directly due to the localization of near field. The results indicate that the near-field technique can act as a new nondestructive testing technique to detect and even image the corrosion area buried in concrete in engineering structure.
In this paper, a new compact tri-band bandpass metamaterial (MTM) filter based on meander line with a rectangular stub is proposed and designed. The pseudo connections between meander line and ports generate interdigital capacitor (IDC) to provide series capacitance. Meander line a rectangular stub is plotted. The proposed filter offers measured first passbands from 1.88-4.0 GHz; second band starts from 5.4-5.9 GHz; third passband ranges from 7.1-7.4 GHz. It has insertion losses of 0.8 dB, 1.5 dB and 2.0 dB at 2.1GHz, 5.7 GHz and 7.3 GHz centre frequencies, respectively. The designed filter will cover S band (2-4 GHz), ISM band (5.725-5.875) and fixed satellite services (7.25-7.3 GHz). Further, the designed filter shows electrical size of 0.14λ0 × 0.13λ0 at zeroth order resonance (ZOR) frequency 2.1 GHz.
This paper proposes a compact E-Plane five-port waveguide power combining and splitting structure in the V-band. The symmetrical five-port structure guarantees excellent amplitude and phase consistency between the input/output ports. Two isolation ports guarantee high isolation between the input/output ports. Meanwhile, the E-plane waveguide structure is more compact than H-plane structure. A two-way power combing structure working from 59 GHz to 64 GHz is designed, fabricated and measured for validating our structure. The measured results show that the phase and amplitude differences between the input ports are smaller than ±1.0 degree and ±0.1 dB, isolation between the input ports higher than 18 dB, the insertion loss and return loss lower than 0.2 dB and better than 17 dB, respectively.
A single-layer reflectarray antenna using circular patch with four semicircular ring slots is proposed in this paper. By changing the diameter of the circular patch, the proposed phasing element can realize phase range about 500 degrees with relatively stable reflection magnitude. Besides, the reflection phase curve with smooth slope is almost linear. Based on the good phase response, a 421-element reflectarray is designed, simulated and fabricated. The measured results show that 1.5-dB gain bandwidth can attain 24% at the center frequency of 15 GHz.
A novel asymmetrical single-pole double-throw (SPDT) switch for 2.4 GHz application with high power handle ability is developed. The novel asymmetrical topology is discussed. To increase the power capacity, ac-floating and dc-bias techniques are used. Using these techniques, a switch achieves a measured P1 dB of 20.5 dBm, an insertion loss (IL) of 1.16 dB and isolation loss of 20.8 dB in TX mode; an insertion loss of 1.57 dB and an isolation of 21.6 dB in RX mode. The circuit is fabricated using 3.3-V 0.35-μm DNW NMOS transistors in 0.18-μm bulk CMOS process.
In this article, design and analysis of a compact wideband short-ended metamaterial antenna based on composite right and left handed transmission line (CRLH-TL) is presented. The proposed antenna is configured with two different shapes (Half ring and simple gap) of series gaps and short ended boundary condition. It offers wide bandwidth by placing two different shapes of series gaps in such a manner, so that the first resonance frequency, i.e., zeroth order resonance (ZOR), second resonance frequency and third resonance frequency occur near each other, and hence combination offers wide bandwidth. Because of the applied boundary conditions, resonant modes can be controlled by series parameters of the proposed antenna structure. Further, coplanar waveguide feeding technique is used which replaces the requirement of via and allows the fabrication of a single layer antenna prototype. The proposed antenna is modeled by using ANSYS HFSS 14.0, and simulated results are verified with experimental ones of the prototype. The simulated fractional bandwidth of the proposed antenna is 52.38% centered at 3.57 GHz. Furthermore, the proposed antenna provides an average broadside gain of 2.30 dBi with average radiation efficiency of 94.95% in the entire working band of antenna.
A new approach to design of a dual-band power divider with only one section transmission line is proposed. Apart from the isolation resistor, admittance matrix is used to synthesize the dual-band divider. According to the required admittance matrixes at two frequencies, a modified configuration with shunting open/short stubs at each port is presented. A new compact dual-band (operating at 1.0 GHz and 4.5 GHz) is developed to validate this proposal. Experimental results demonstrate that the return loss is better than -19.2 dB, insertion loss less than 0.59 dB, and isolation better than 23.61 dB at two operation frequencies. The measured relative bandwidths of 15 dB return loss are 35.9% and 12.4% for the lower and higher bands, respectively.
In most applications of antenna arrays, side lobe levels (SLLs) are commonly unwanted. Especially, the first side lobe level which determines maximum SLL is the main source of electromagnetic interference (EMI), and hence, it should be lowered. A procedure of finding the optimum side lobe-minimizing weights for an arbitrary linear equally spaced array is derived, which holds for any scan direction, beam width, and type of antenna element used. In this science article, the use of convolution procedure and the time scaling property reduces the side lobe level for any type of linear equally spaced array. Results show that by this procedure, the side lobe level is reduced about two times or even more.
The present work is devoted to the clarification of the conditions necessary for step-by-step justification of the possibility of reduction of the homogeneous system of linear algebraic equations for the spectral problems of 2-D photonic crystals by the plane waves method. The issues related to the algorithms and the numerical solutions of these spectral problems are analyzed. The possibility of analytical regularization is investigated, and the ways to improve the convergence of the obtained results are identified.
We introduce a 212 GHz LO source which could be used to drive sub-harmonic mixer in the radiometer front-end. It mainly includes a phase-locked dielectric resonator, a 71 GHz power source and a 212 GHz tripler. Actually, design of 212 GHz tripler is the key technology in the LO chain because the research on W band source is relatively mature. Based on our former research work, there is a great improvement in the design of 212 GHz tripler. At room temperature, the measured efficiency is more than 9% in 208~218 GHz, and the maximum efficiency is about 14.5% at 215.5 GHz when being driven with 21.8 dBm of input power. Besides demand on the main technical specifications, the stability of each module is also extremely important since the front-end is designed to keep working for three months.
This paper presents the design of a compact E-plane waveguide diplexer with wide stopband characteristics of high rejection level. This is achieved by utilizing a unique E-plane waveguide filter comprising rectangular apertures located along the waveguide's E-plane. The upper and lower sections of the aperture in the septum insert have periodic comb-like ridges. The effect of the septum is (i) to slow the propagating wave that helps to reduce the filter's size, and (ii) widens its stopband property. Dimensions of the periodic ridges of the aperture enable the center frequency of the filter to be controlled without compromising its bandwidth. In addition, the proposed E-plane waveguide filter provides a high isolation between the two diplexer channels, which is necessary to prevent significant cross-talk between the channels. The performance of the proposed design was verified through measurements. There is excellent agreement between the simulated and experimental results.
This paper presents a frequency reconfigurable dual-pole, dual-band waveguide bandpass filter. Varactor diode and chip capacitor loaded planar split ring resonators are used on the transverse plane of a waveguide to form the filter. Numerical simulations are carried out using CST microwave studio (version 14). Measured result shows tuning range of the bands are 8.12-8.58 GHz and 10.22-10.68 GHz, respectively. The measured result shows good agreement with the simulated one. The total length of the proposed filter is 10 mm.
This paper presents an electrical tunable bandpass filter based on tunable LC resonators loaded with semiconductor varactors. Magnetic dominated mixed coupling between the tunable resonators is utilized to compensate the bandwidth of the tunable filter. Cross coupling is created by using magnetic dominated mixed coupling between the resonators and source to load electrical coupling, and two transmission zeros are generated beside the pass band. The tunable mechanism of the proposed filter is studied. The tunable filter is analyzed, designed, fabricated and measured. The measurement shows that the filter can be tuned from 70 MHz to 270 MHz with a fractional bandwidth from 27% to 21%.
Interfering electromagnetic energy could be a very powerful pulse which is generated and incident onto communication system such as linear wire antenna through direct radiation. In this paper, the transient responses of the linear wire antenna such as dipole antenna under the impact of the early-time (E1) high-altitude electromagnetic pulse (HEMP) are investigated using the equivalent circuit due to a primary element used in the modeling of systems for HEMP vulnerability is the linear wire antenna such as dipole antenna. Based on the equivalence concept of HEMP radiation source and linear wire antennas, the response at receiving antenna port is calculated efficiently with an uncomplicated circuit composed of pulse voltage source and lumped elements. Numerical results are presented to confirm the accuracy of the proposed method.
In this letter, a compact ultra-wideband (UWB) bandpass filter based on CPW-to-microstrip transition structure is proposed. Compared with traditional UWB BPF using hybrid structures, the proposed filter has a more sharp selectivity due to a transmission zero located at the lower edge of the passband generated by the combined effect of both CPW-MS-CPW and interdigital coupling line (ICL). Moreover, to further improve its selectivity, the CPW open stubs (CPWOS) are introduced to produce two extra transmission zeros at high frequency. The measured results show that the proposed filter has some good characteristics such as sharp roll-off, compact size (0.54λg × 0.38λg) and a very wide fractional bandwidth of 130%, which is a significant improvement to what has been reported for UWB BPF with similar structures.
In this paper, a broadband circularly polarized (CP) antenna based on slot-loaded dipole with L-shaped arms and parasitic patches is proposed and investigated. Circular polarization is initially obtained at the lower frequency by bending the dipole arms into L-shape. To extend the axial ratio (AR) bandwidth, two pairs of parasitic patches are introduced along the orthogonal sections of the L-shaped arms, so that the modified dipole can yield two additional minimum AR points at the center and higher frequency respectively. Meanwhile, to further extend impedance bandwidth and improve CP performance, circular slots are symmetrically embedded into the tapered-end of each arm design. The measured results of the antenna exhibit a 3-dB AR bandwidth of 61.3% within 10-dB return loss bandwidth of 64.0%. Besides, desirable gains across the wide operation band are also demonstrated.
This paper demonstrates a new class of highly selective bandstop filter based on cascading two identical lossy hybrid dual-band bandstop filters of low resonator Q factor. Each filter is synthesized based on multi-stage predistortion reflection mode technique. To demonstrate the approach, 4th order hybrid dual-band elliptic filter network which is a product of elliptic lowpass and highpass network functions has been predistorted and synthesized with low calculated Q factor. The lossy dual-band bandstop filters are fabricated and realized on microstrip planar structure. Both theoretical and experimental results clearly show good agreements with two stopband rejections up to 35 dB for one stage and 50 dB for two stages with passband loss of more than 10 dB.
This paper describes a frequency-tunable phase inverter based on a slot-line resonator for the first time. The control circuit is designed and located on the defected ground. None of dc block capacitors are needed in the microstrip line. A wide tuning frequency range is accomplished by the use of the slot-line resonator with two varactors and a single control voltage. A 180-degree phase inverter is achieved by means of reversing electric field with two metallic via holes connecting the microstrip and ground plane. The graphic method is used to estimate the operation frequency. For verification, a frequency-tunable phase inverter is fabricated and measured. The measured results show a wide tuning frequency range from 1.1 GHz to 1.75 GHz with better than 20-dB return loss. The measured results are in good agreement with the simulated ones.
A low-profile bandwidth-enhanced zeroth-order resonant (ZOR) antenna based on composite right/left-handed transmission line (CRLH-TL) theory loaded by parasitic element is presented in this paper. The bandwidth and efficiency of the proposed ZOR antenna is improved simultaneously by introducing a parasitic element resonating within the CRLH-TL band-stop. The dispersive behavior of the ZOR antenna is analyzed by performing full-wave simulation using CST microwave studio and compared with the theoretical circuit model. The overall dimensions of the proposed antenna is 0.303λ0×0.248λ0×0.003λ0. The antenna has been fabricated and tested. The experimental results exhibit widem operational bandwidth of 87.1% and excellent radiation efficiency up to 95.7%. Owing to the symmetrical configuration of the proposed design the polarization purity better than -14 dB is obtained. The measured results are in very good agreement with the simulation. The compact, uni-planar and via-less configuration of the proposed antenna with reasonable polarization purity makes it desirable to be used for modern wireless communication systems such as GSM, UMTS, WiMAX, WLAN and LTE.