This paper presents a miniaturized branch-line coupler with suppression of wideband harmonics based on a unit of transmission-line section with triple-stub. This fundamental unit produces three transmission zeros and exhibits wide stopband response due to the triple stubs. It is used to replace a quarter-wavelength line in conventional branch-line coupler, leading to size reduction and wideband harmonics suppression. The closed-form equations are given for the coupler design. As an example, a branch-line coupler operating at 1.0 GHz is designed, fabricated and measured. Measurements agree well with simulations, and show that the proposed branch-line coupler occupies 56% size of a conventional one and achieves wideband harmonics suppression (better than 17 dB) from 1.8 GHz to 6.4 GHz. The 2nd, 3rd, 4th, 5th, and 6th harmonics are suppressed better than 34 dB, 19 dB, 30 dB, 17 dB, and 32 dB, respectively. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and wideband harmonics suppression.
In this paper, a wide-band, polarization-insensitive, wide-angle terahertz metamaterial absorber is presented. Simulated results show that the absorber can achieve polarization-insensitive, wide-angle absorptions in a wide band from 4.15 to 4.85 THz. The retrieved impedance shows that the impedance of the absorber could be tuned, in the absorption band, to match approximatively that of free space on one side and to mismatch on the other side, rendering both the reflectance and transmission minimal and thus the corresponding absorbance maximal. The simulated absorbances under three different loss conditions suggest that high absorbance is mainly due to the metallic absorption (Ohmic loss). The dielectric loss of the substrate is minor compared with the metallic absorption. The distribution of the surface current density indicates that the electric and magnetic responses are mainly caused by the front structure. This wide-band terahertz metamaterial absorber has potential applications in many functional devices such as microbolometers, thermal detectors, and solar cells.
An important application of electromagnetic band-gap (EBG) structures is reducing the mutual coupling and eliminating the scan blindness for array antennas. However, some array antennas have small element spacing,and traditional mushroom-like EBG materials are too large. Under this condition, miniature EBG structures are desired for these array antennas. In this paper, a novel method using spiral ground plane is proposed to reduce EBG structure sizes. A low frequency band-gap can be obtained by adjusting the width and length of the spiral arms. An experimental prototype is fabricated to validate the analysis. The measurement results show a good agreement with the simulation data. Compared with traditional mushroom-like EBG structures, the proposed EBG achieves more than 77% size diminution.
We propose single metal layer metamaterial bandpass filters based on compact complementary u-shaped resonators. Previously, metamaterial bandpass filters could only be achieved if a second conducting layer was utilized. Here, we propose a resonator concept that can directly be integrated with a single sided coplanar waveguide, enabling low fabrication costs and simple system integration. Furthermore, already a single unit cell yields a pronounced bandpass behavior without the need for cascading multiple resonators. Both, measurements and numerical simulations are presented. Using RO3003 as substrate, a low insertion loss of 1.71 dB and a corresponding 3-dB bandwidth ratio of 3.1% is achieved.
A fiber laser with 180 GHz ultrabroad linewidth is developed using a broadband light source and a bandpass filter. Active phase locking of two fiber amplifiers with 180 GHz linewidth is successfully realized using stochastic parallel gradient descent technique. The fringe contrast of the interference pattern is as high as 65% when active phase control is implemented. The reported results indicate a promising power scalability of fiber amplifier modules developed for phase locking.
In this paper, a compact stepped-impedance hairpin resonator (SIHR) low-pass filter (LPF) with an improved split-ring resonator defected ground structure (ISRR DGS) and two elliptical DGSs is presented. The proposed LPF exhibits the advantages of low insertion loss, sharp cutoff characteristic, wide stopband over the ordinary LPFs. The introduced DGSs are presented to improve the in-band and out-band characteristic. An equivalent RLC circuit model of the two kinds of DGSs is presented and analyzed. Combining with these two structures, a new SIHR LPF having 3-dB cutoff frequency of 2.5 GHz is fabricated and measured. Measured results show that the selectivity of the proposed LPF is more than 100 dB/GHz and the insertion loss is less than 0.5 dB in the passband. A wide stop-band bandwidth with 20 dB attenuation from 2.58 up to 7.5 GHz is achieved. Moreover, the occupied area is only 20×25 mm2.
In this paper, a novel compact wideband bandpass filter (BPF) is proposed using quadruple-mode resonator formed by attaching a short-circuited stub at the center plane and two identical impedance-stepped open stubs to high impedance microstrip line. The resonator can generate two even-modes fm1, fm3 and two odd-modes fm2, fm4 in the desired band. The even-mode resonant frequencies can be flexibly controlled by the short-circuited stub, whereas the odd-mode ones are fixed. When the open stubs are attached to the center plane nearby, they can be mainly applied to adjust fm3, fm4 into desired passband as the high odd-mode and even-mode resonant frequencies are vulnerable to their electronic lengths. Two transmission zeros near the lower and upper cut-off frequencies are separately created by the short-circuited stub and interdigital feeding lines, leading to a high rejection skirt. A wideband BPF with the fractional bandwidth 64% is simulated, fabricated and measured. The measured results agree well with the EM simulations.
A novel design of a compact dual inverted C-shaped slots antenna for dual-band (IEEE 802.11b/g, 2.4-2.484 GHz and IEEE 802.11a, 5.15-5.35/5.725-5.825 GHz) WLAN applications is proposed in this paper. The antenna is based on dual inverted C-shaped slots and a μ-shaped feeding structure. These fundamental configurations are applied to achieve two operating bands with resonating frequencies at about 2.45 GHz and 5.5 GHz to cover the dual WLAN bands. The proposed antenna is fabricated and tested. The simulated and measured results show that the slot antenna obtains two independent operation bands of 2.4-2.515 GHz and 5.14-5.85 GHz for S11≤-10 dB, and also stable gain characteristic with peak gain variations less than 1 dBi for both the bands. Details of the analysis and research progresses are shown in the following sections to illustrate the design steps and the performance of the proposed antenna.
A compact 9-21 GHz monolithic image reject mixer (IRM) with a chip dimension of 0.9×0.74 mm2 has been designed and fabricated using a standard 0.18 μm CMOS technology. The compact configuration is composed of a 90°coupler for local oscillator (LO) and two doubly balanced ring mixers for mixing core. Particularly, a radio frequency (RF) dual balun with advanced intermediate frequency (IF) extraction technique can not only eliminate the use of power divider in IRM design, and simultaneously provide balanced signals for ring mixing, but also obtain high side band suppression without any additional IF low-pass filter. Moreover, the entire passive circuits are constructed by utilizing broad side coupling structure to achieve high-level integration further. From the measured results, the IRM exhibits a 19.4-22.4 dB conversion loss, a maximum image rejection ratio (IRR) of 34 dB, all port-to-port isolations better than 28 dB over RF frequency range of 9 to 21 GHz, and an input 1 dB compression power of 14 dBm.
A novel fractal structure using Koch and Sierpinski fractal-shapes is proposed. By inserting the Sierpinski carpets into the single patch and etching the inner and outer patch edges according to Koch curves, the resonant frequency of the patch antenna can be lowered significantly. And the higher of the iteration order of the fractal shapes, the lower the resonant frequency becomes. In this paper, a novel small-size single patch microstrip antenna based on the proposed fractal-shapes is designed, fabricated and measured. It is experimentally found that the size reduction can reach 80.3%. Compared to the conventional square single patch antenna, the proposed antenna maintains comparable radiation patterns. Therefore, the small-size single patch microstrip antenna considered here can be applied to portable wireless communication systems requiring small devices.
We numerically investigate the interaction of nonlinear pulses in coupled transmission lines with regularly spaced Schottky varactors. The c mode and π mode are two different propagation modes that can be developed on a coupled line. Recently, we have found that both modes can support soliton-like pulses due to the presence of the Schottky varactors and proposed a method of doubling repetition rate of the incident pulse stream. Through numerical evaluations, we find that small c-mode pulses are generated by colliding two π-mode pulses traveling in the opposite directions. Utilizing this unique property, the repetition rate of incident pulse stream can be increased by the factor greater than 2.
In this paper, single-crystalline silver filaments with periodic, pearl-chain-like structures are fabricated by electrodeposition without using any templates, surfactants, and additives. Simulations demonstrate that excited surface waves may sustain on silver pearl chains in middle infrared (Mid-IR) range. Based on the propagation features of surface waves on the silver filaments, this structure can be applied for electromagnetic wave transmittance in Mid-IR range. The propagation features of surface waves on the silver filaments indicate the structure application for Mid-IR wave transmittance.
A miniaturized internal wideband antenna suitable for integration with the printed circuit board (PCB) of a wireless universal serial bus (WUSB) dongle is presented in this paper. The proposed antenna mainly consists of a folded metal plate with two sides beveled. By introducing a short-circuited pin connected to the system ground and etching a pair of slots in the bevel sides of the folded metal plate, a large impedance bandwidth from 2.4 GHz to more than 11 GHz is obtained, which easily covers the 2.4 GHz WLAN, WiMAX, S-DMB and UWB frequency bands. The effects of the short-circuited pin and the narrow slots on the impedance matching of the proposed antenna are investigated. The proposed antenna is easy to be fabricated by bending a sample metal plate due to its miniaturized geometry of 5×12×12.5 mm3. Details of the antenna design are described, and experimental results of the constructed prototypes are presented and discussed.
A novel dual-wideband printed monopole antenna is proposed for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna consists of a T-shaped monopole on top and dual combined G-shaped slots located symmetrically on the ground plane to achieve a dual-wideband performance. Prototype of the proposed antenna has been constructed and tested. The measured 10 dB bandwidths for return loss are 1.76 GHz from 2.13 to 3.89 GHz and 0.92 GHz from 5.03 to 5.95 GHz, covering all the 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX bands. And this antenna also has omni-directional patterns over the lower operating range.
In this paper, an ultra-wideband (UWB) bandpass filter (BPF) with a notch-band at 5.8 GHz is presented. The proposed filter is constructed with multiple-mode resonator (MMR) using novel dumbbell stubs and one-arm-folded interdigital coupled lines in the input and output sides. The MMR consists of three pairs of shunt dumbbell stubs and a high impedance microstrip line. By adjusting the dimensions of the dumbbell stubs, the resonant modes of MMR are allocated in the UWB band. The arm-folded interdigital coupled lines are used to obtain a notch-band at 5.8 GHz. Finally, the proposed UWB BPF is fabricated. The simulated and measured results are in good agreement with each other.
A Coplanar Wave guide (CPW) fed printed monopole antenna with reduced radiation hazard from a mobile handset is presented. The printed metal stripes in the back side of the monopole modify the far field pattern ideal for mobile handset. The antenna offers a bandwidth of 200 MHz when printed on a substrate of dielectric constant (εr) 4.4 and thickness 1.6 mm with an overall dimension of 42x31.7 mm2. Experimental and simulation studies of the antenna radiation characteristics of the proposed antenna are presented and discussed. A 20 dB reduction of radiated power in one quadrant of the radiation pattern offers a reduction of radiation towards the users head.
In this paper, we present a procedure to calculate the discrete modes propagated with Crank-Nicolson FDTD in metallic waveguides. This procedure enables the correct excitation of this kind of waveguides at any resolution. The problem is reduced to solving an eigenvalue equation, which is performed, both in a closed form, for the usual rectangular waveguide, and numerically in the most general case, validated here with a ridged rectangular waveguide.
A novel and simple antenna applicable to active RFID tags is designed. The designed antenna has been skillfully integrated with the active RFID tag circuit. The antenna consists of two parts. One part comprises stacked shorted patches and a ground plane. The other one is an active tag circuit mounted on the bottom of the antenna. By using the offset shorting posts technique, the proposed antenna can achieve an enhanced operating bandwidth with a small size. The measurement results reveal that the antenna has return loss less than -10 dB within the bandwidth of 42 MHz (from 914 MHz to 956 MHz), which totally covers the 5MHz bandwidth from 920MHz to 925 MHz (The band is also allowed for passive RFID) requirement for active RFID in China.
This paper outlines typical issues in the design and fabrication of microstrip Wilkinson power dividers. As a practical solution, a modified Wilkinson divider configuration is proposed and designed for millimeter-wave antenna feeding networks. In this design, all microstrip branches and the resistive strip exhibit the same characteristic impedance. Probe measurements of Sparameters underline good matching, transmission and isolation characteristics of the proposed divider.
In order to reduce the monostatic signature of the junction between a radome and the metallic structure to which it is attached, a tapered resistive sheet can be used. In this paper, we describe an easy method to realize this tapering using geometric variations on a subwavelength scale, with a significant reduction of the number of processing steps as a result.