A new metamaterial-inspired polarization reconfigurable microstrip antenna is presented in this paper, in which a square slot is etched on the ground plane and two PIN diodes are mounted across the slot for polarization reconfigurability. A complementary split ring resonator (CSRR) can be formed by integrating the square slot with two diodes. By controlling the working states of two diodes, we can change the gap position of CSRR which will alter the polarization of the microstrip antenna. Therefore, the polarization of the microstrip antenna can be switched among linear polarization (LP), left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), respectively. The planar electromagnetic bandgap (EBG) structure is further introduced to extend the bandwidth of the 3dB axial ratio. In addition, the proposed metamaterial-inspired antenna with agile polarization reconfiguration can be feasibly controlled by using a simple biasing circuit. The simulations and experiments are given to verify the effectiveness and correctness of the proposed reconfigurable antenna design.
A novel ultra wideband (UWB) multiple-input-multiple-output (MIMO) antenna with different polarizations and band-notch characteristics is proposed in this letter. The antenna consists of two monopole antenna radiating elements with gradual change structure, which are placed perpendicularly to each other and printed on each side of the substrate to achieve a wide bandwidth and different polarizations. Band-rejected filtering property in the WLAN band is achieved by etching a H-shaped slot and employing a resonant L-shaped strip on two antenna elements. The proposed antenna has a small size of 27×37×1 mm3 with a bandwidth of 128.6% (2.35-10.82 GHz). Within the required band, the isolation for the two ports exceeds 18 dB. The envelope correlation coefficient is also measured.
A broadband transition design between rectangular waveguide and GCPW is proposed and studied. The E-field of GCPW is designed to be gradually changed to that of waveguide via the simple tapered probes and metallic vias. The planar circuit of the transition is fabricated by low cost standard PCB process. The tolerance analysis for this transition is also given. A back-to-back transition prototype at Ka-band is fabricated and measured. The measurement results show that maximum insertion loss of 0.75 dB and return loss of better than 15 dB are obtained within a desired frequency range from 26.5 to 40 GHz. The measurement results agree well with simulation results, which validate the feasibility of this design.
In this paper, the design of a multiband antenna for WLAN and WiMAX applications is proposed. The proposed antenna comprises a circular radiating patch with a pair of rectangular slits and an inverted U-shaped slot. A hexagon-shaped slot is cut on the ground plane. By adjusting the inverted U-shaped slot, a pair of rectangular slits, and a hexagon-shaped slot, three distinct resonance frequencies centered at 2.4 GHz, 3.52 GHz, and 5.68 GHz can be generated. The measurements show that the proposed antenna can cover three frequency bands with sufficient bandwidth. The proposed antenna exhibits an omnidirectional radiation pattern and acceptable gain.The overall dimension of the proposed antenna is 25 × 39 × 1.59 mm3.
A novel (2×2) high gain circularly polarized rectangular dielectric resonator antenna array integrated with helical-like exciter is proposed. The array offers a maximum gain of 12.9 dBi at the operating frequency. The circular polarization is obtained by incorporating helical-like exciter in the array structure. A prototype of the proposed configuration integrated with helical-like exciter has been fabricated and tested, and the idea has been verified. A good agreement has been obtained between the measured and simulated results.
A new defected ground structure (DGS) with tunable working frequency and reconfigurable bandwidth is proposed in this paper. The prototype combines the conventional DGS with T-shaped patch featuring narrow bandwidth and two such units located symmetrically featuring wide bandwidth. The proposed structure is designed, simulated and measured. By embedding two reversely-set PIN diodes and four varactors, the proposed structure achieves a narrow bandwidth with a tuning range of 21.1% and a wide bandwidth with a tuning range of 24.6%. In comparison, the bandwidth (-10 dB) is about 13.6% for the narrowband state and 49.2% for the broadband state, where an approximately 4-times extension is obtained.
In [1], Hacivelioglu and co-authors criticize my paper, named ``Fringe waves in an impedance half-plane" [2]. Unfortunately, the general scenario of the criticisms is based on misconceptions and lack of basic knowledge in the diffraction theory. Below we give our detailed rebuttals on their comments.
This paper (i.e., [1]) extends PTD to an impedance half-plane problem.
We present a broadband microwave metamaterial (MM) absorber, the unit cell of which consists of a lumped-resistor-loaded electric-inductive-capacitive (ELC) resonator and a cut-wire on the same side of a flexible polyimide substrate. In contrast to the common MM absorber, the metallic pattern layer of the proposed structure is placed parallel to the direction of propagation of the incident wave in order to reduce the radar cross-section (RCS) at frequencies other than the targeted frequency bands. Our experiments show that the proposed absorber exhibits a peak absorption rate of 92% and 93% at 8.6 GHz and 13.4 GHz, respectively, and 88% of the full-width at half-maximum (FWHM) bandwidth is achieved.
This paper presents a low-cost strip-to-bilateral-slotline transition with operating bandwidth from 0.53 to 6 GHz. The low-cost design concept is realized by utilizing conventional cheap FR-4 substrate and wide slotline with large slot width. By virtue of the low price of FR-4, less strict fabrication tolerance of wide slotline and the avoidance of metallic vias, the fabrication cost is reduced significantly compared to schemes using expensive Rogers RT laminates, extremely narrow slotline with strict fabrication tolerance and metallic vias. The broadband impedance matching difficulty caused by the high characteristic impedance of wide slotline is solved by three means. Firstly, bilateral structure is used to lower the characteristic impedance of the slotline. Then an elliptic slotline stub and an innovative half-elliptic strip stub are proposed to provide good impedance matching. Finally, multi-section stepped impedance transformers are used to match the transition from high impedance to standard 50 Ohm. The validity of the design methods is verified through experiments.
Based on Faraday's law of electromagnetic induction and the existence condition of non-trivial solution to a homogeneous and linear differential system of equations, the equivalent self-inductance of N coupled parallel coils has been derived by uing some algebraic techniques. It can be expressed as the ratio of the determinants of two matrices, with ranks of N and N-1, respectively, and constructed with the self and mutual inductance of those coils. In addition, special conclusions are deduced and/or discussed in detail for three particular cases: 1, the completely uncoupled case, 2, the identical and symmetrical case, and 3, the completely coupled case, which are coincident with the existing results in the references.
Element failure distorts the main-lobe pattern and increases side-lobe power level, which is almost impossible to be corrected artificially for space-borne array. It might be solved by redistributing the excitations of the left functional elements; however, this is a nonlinear, non-convex, and NP-hard problem. In this paper, two effective approaches are proposed for failure correction, which is performed for space-borne hexagonal array using digital beamforming (DBF). One method, a modified real-code genetic algorithm (RCGA), is employed that uses reinsertion and worst-elimination schemes, but it pays the high computation complexity. The other approach based on convex optimization chooses the excitations synthesized by RCGA as the initial points, and skillfully transforms the non-convex problem into a sequence of second-order cone programming (SOCP) problem, which is solved iteratively by efficient optimization tool. Numerical results confirm that after the correction based on iterative convex optimization, the average root-mean-square error (RMSE) is reduced by 36%, and the relative side-lobe level (RSLL) is improved by 6.7 dB, with respect to the RCGA-based correction pattern.
A novel wideband multilayer power divider with high isolation and bandpass response is presented in this article. This presented power divider employs microstrip-slotline coupling structure to realize the basic function of dividing input power. One lumped isolation resistor is introduced to improve the isolation between output ports. In order to solder the chip resistor between output branches, bending microstrip structure is utilized. For the sake of rejecting the unwanted signals locating in adjacent channels, interdigital structure and defected ground structure are designed to obtain a bandpass response and a wide upper stopband. The experimental results have indicated that the proposed wideband power divider has good performance on return losses, isolation, amplitude and phase balances, as well as group delay over the band 4.5 GHz-10 GHz.
In this article, a novel band-notched ultra-wideband (UWB) bandpass filter based on hybrid microstrip/slotline structure is proposed. A quad-mode stubs-loaded slotline resonator is fed by two orthogonal microstrip lines and ultra-wideband bandpass characteristic is excited. A stub-loaded dual-mode microstrip resonator is externally loaded to the quad-mode slotline resonator, and a notched band with sharp roll-off characteristic is achieved. The circuit model for the dual-mode microstrip resonator loaded slotline is given and analyzed. The proposed filter is designed and fabricated. Simulated and measured return losses are -12 dB/-18 dB and -18 dB/-10 dB in lower and higher passband. The return loss in the notched band is greater than 15 dB.
In this letter, a new design of dual-band circularly polarized (CP) slot antenna is proposed. By embedding a vertical stub, a T-shaped strip and a slit to the ground plane, the CPW-fed slot antenna can radiate right-handed circularly polarized (RHCP) wave in two bands 3.0 GHz and 5.0 GHz. The designed antenna with a size of 33 × 27 × 1 mm3 is fed by a 50-Ohm SMA connector and fabricated on a low-cost FR-4 substrate. Experimental results show that the measured 10-dB return loss impedance bandwidths are 20.4% for the lower band and 23% for the upper band, and the measured 3-dB axial-ratio (AR) bandwidths are 14.1% and 15.8%, with respect to 3 GHz and 5 GHz, respectively.
In Chinese Compass Navigation Satellite System (CNSS for short), dual-band antennas are more attractive, because they can provide both navigation and communication services. In this paper, we present a dual-band dual-circular-polarized planar spiral-slot CNSS antenna. This antenna works at L Band (1616±5 MHz, left-handed circular polarization, LHCP) and S Band (2492±5 MHz, right-handed circular polarization, RHCP). Numerical results show that the impedance bandwidth (S11<-10 dB), 3 dB axial ratio bandwidth and antenna gain at L Band are about 242 MHz, 79 MHz and 4.92 dB, respectively, while the simulated impedance bandwidth (S11<-10 dB), 3dB axial ratio bandwidth and antenna gain at S Band are about 180 MHz, 58 MHz and 5.25 dB, respectively. An experiment was carried out to verify our design. Measured results show that impedance bandwidth (S11<-10 dB) and 3 dB axial ratio bandwidth L Band are about 300 MHz and 14 MHz, respectively, while the measured impedance bandwidth (S11<-10 dB) and 3 dB axial ratio bandwidth at S Band are about 210 MHz, 10 MHz, respectively. The measured results basically agree with the simulated ones and meet the requirement of CNSS terminal antennas.
A compact wideband planar microstrip-fed quasi-Yagi antenna is presented. In order to achieve a high gain, the traditional rectangular director in one row is replaced by two rows of directors with an angle, and the overall size of the antenna is unchanged. By adjusting the angle between the two rows of directors, a better performance is achieved. The measurement results show that a broadband impedance about 85.5% (1.84-4.59 GHz) for S11 less than -10 dB and a gain about 4.5-9.3 dBi are obtained. Simulation and measurement results are provided and discussed. The agreements between the simulation and measurement results indicate that the antenna is suitable for wireless communication applications and phased arrays.
A PLDRO (Phase Locked Dielectric Resonator Oscillator) with the output frequency of a fractional multiple of reference is proposed and implemented. The key element in the proposed PLDRO is an image rejection mixer placed between a VCDRO (Voltage Controlled Dielectric Resonator Oscillator) and SPD (Sampling Phase Detector). The image rejection mixer shifts the coupled signal from the VCDRO before the signal feeds the SPD. Therefore, the output frequency of the PLDRO can be realized such that it is not harmonically related with its reference frequency. The frequency divider and multiplier generate the IF frequency for the mixer from the reference frequency. The general PLL (Phase Locked Loop) design parameters such as the damping coefficient and the natural frequency are derived for the proposed topology of the PLDRO. A 7.25 GHz PLDRO with a 100MHz reference, intended for use as a local oscillator for a ka band Block-up Converter (BUC), is designed and measured. A BJT (Bipolar Junction Transistor) is used as an active component of the VCDRO and a modified two micro-strip line coupled DR model is presented and used for frequency tuning range estimation. The measured phase noise at 10 kHz/100 kHz offset is 101 dBc/Hz and 115 dBc/Hz, respectively. The fabricated PLDRO size is 100 mm by 105 mm by 23 mm including a 100 MHz reference crystal oscillator.
The paper is devoted to the study of microwave analogue of Tamm states appearing at the boundary of two different periodical chain-like structures in contact. A comparison of numerical and experimental data is provided for periodical chains of quadripoles modelling our system. As it turns out, at the point of contact of two different periodic structures, significant concentration of electromagnetic wave energy takes place. The corresponding concentration of energy is quite similar to those characteristics for Tamm states concentration which takes place at the boundary between two adjacent photonic crystals. We use the term microwave analogue of Tamm states for the considered periodic chain-like structures.
This paper presents the design and fabrication of a feed horn antenna integrated fix-tuned 380 GHz sub-harmonically pumped mixer, based on planar GaAs air-bridged Schottky anti-parallel diode from Rutherford Appleton Laboratory. The diode was designed and fabricated by millimeter technology group, Rutherford Appleton Laboratory, UK. The mixer's circuit configuration and cavity block are realized by joint simulation of ANSOFT's three-dimensional full-wave electromagnetic simulation software HFSS and AGILENT's circuit simulation software ADS. The mixer circuit is fully integrated with the microstrip circuit and the flip-chipped diode on suspended 50 μm thick quartz substrate, and whole fixed-tuned mixer cavity block is integrated with RF feed horn antenna, using least parts to minimize the cost, as well as maximizing its potential convenience for circuit and block manufacture. The simulation and test investigation have good agreement and show state-of-the-art results. The experimental results show that over an IF band of 2.5-3.5 GHz, the mixer's conversion loss is lower than 10 dB with mean value 9 dB, and the mixer's equivalent noise temperature is less than 3000K with mean value 2000 K. Besides, mixer equivalent noise temperature curve's variation trends show good consistency with conversion loss curve.
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