Volume 73, Issue 9-10 -

A compact third-order triplexer using a common lumped-element triple-mode resonator (LE-TMR) and LC resonators is presented in this paper. Every channel of proposed third-order triplexer has three resonant modes, i. e. one resonant mode from the common LE-TMR and another two resonant modes from two LC resonators. Step-to-step design procedure is given to guide the third-order triplexer design. As an example, a 0.9/1.8/3.5 GHz third-order triplexer with ripple bandwidths of 150/210/290 MHz is designed, fabricated and measured. The fabricated third-order triplexer has a compact circuit size of 0.163λ g  × 0.104λ g , and high electrical performance can be also acquired.

This work presents an approach to developing dual-mode dual-band substrate integrated waveguide (SIW) bandpass filter based on multilayer process. TE102/TE201 and TE101/TE102 modes are used to feature the two passbands, respectively. To begin with, large range of band location ratios are decided by the effective dimension of the SIW resonator. With reference to the field distribution, independent coupling schemes of the dual-modes are then realized by slots or circular apertures etched on the middle metal layer. It allows to not only introduce a large design freedom of bandwidth but also keep compactness. Finally, source-load and mixed couplings are deployed to produce transmission zeros around the passband in providing a sharp selectivity in the two filters, respectively. The details to independently control the center frequencies and bandwidth of two passbands are also presented. A two-order double-layered and a triple-layered SIW dual-band bandpass filter are prototyped to evaluate the proposed design approach, respectively. Results show a good agreement between simulations and measurements. The proposed filter exhibits flexible design freedom, high selectivity as well as good out-of-band rejection.

In this paper, a tunable power divider (PD) with a good band-pass filtering response using quarter-wavelength stepped impedance resonators (SIRs) is presented. By appropriately adjusting the impedance and electrical length ratio of SIR, the proposed structure can achieve wide stopband performance. Meanwhile, four varactor diodes are loaded to the external resonators to achieve electrical reconfiguration. In addition, a pair of transmission zeros (TZs) can be generated by applying source and load coupling on each side of the passband, which can effectively improve passband selectivity and out-of-band rejection. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed filtering power divider (FPD) with tunable center frequency is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

A two dimensional photonic crystal biosensor with high quality factor, transmission and sensitivity has been theoretically investigated using two dimensional finite difference time domain method (FDTD) and plane-wave expansion (PWE) approach. The studied biosensor consisted of two waveguide couplers and one microcavity formed by removing one air pore. Following analyte injection into the sensing holes and binding, the refractive index changes inducing a possible shift in the resonant wavelength. For the optimized structure, the biosensor quality factor is found to be over 49,767 and the obtained sensitivity is of order 15.2 nm/fg. Also, we investigated this structure in case of all air holes are applied as the functionalized holes with a sensitivity was found to be approximately equal to 292.46 nm∕RIU (refractive index units). According to the resonance cavity characteristics, the demultiplexing of different wavelengths can be achieved by regulating the radius of defects “r” inside the cavity. For this, A new design with 2D PCs for two-channel demultiplexer optofluidic biosensor has been proposed. The analysis shows that the response of each channel has a different resonant cavity wavelength and the filling of analyte in the selected holes cause resonant wavelength shifting, independently.

In this work circularly polarization diversity has been achieved by utilizing two Schottky diodes on low profile cavity-backed substrate integrated waveguide (CBSIW). In comparison with other studies in the literature, the size of antenna has been reduced to 0.54λg × 0.76λg by helping a 50-Ohm coaxial feed line. The impedance bandwidth, axial ratio bandwidth and antenna gain are improved to 10.02 %, 5.2 % and 7.68dBi, respectively. In addition, the proposed antenna can generate either a left-hand circularly polarized (LHCP) or a right-hand circularly polarized (RHCP) radiation. The developed antenna was fabricated and tested and the achieved results were in good agreement with the simulated one.

Novel and miniaturized hexagonal Microstrip patch antenna design is presented in this paper. Patch is fractured using Sierpinski and Koch structures to make the antenna applicable for multiband applications. Additionally ground is defected to enhance the bandwidth and further size is reduced. Material FR-4 (εr = 4.4)has been chosen to design proposed antenna and substrate thickness as 1.59 mm. Microstrip feed technique is used as it provides better results. Gain obtained in this case is 5.57 dB, 7.49 dB and 4.02 dB with bandwidth as 606.8 MHz, 507 MHz and 2 GHz at 8.3 GHz, 12.6 GHz and 17.6 GHz resonant frequencies. The antenna is better to other designs in terms of parameters like bandwidth, directivity, polarization, gain, return loss and dimension. The antenna provides application for military appliances. A good concord is obtained in Simulated and measured results.

A broad-band substrate-free planar metamaterial lens fed by a horn antenna is proposed. A geometric transformation of polygon is introduced in order to make gradient tuneable unit cells out of ordinary metamaterial structures. A circular lens with gradient epsilon along its surface is designed and fabricated based on the transform theory. Measurement results indicate that the proposed lens is capable of improving the gain of the horn antenna within the frequency band of 78–89 GHz which is more than doubled as comparing with existing substrate-free metamaterial lenses.

A novel dual-band rectangular slot antenna is presented for dual-sense reconfigurable polarization. A W-shaped microstrip feedline and two rectangular parasitic patches are used to obtain dual-band circular polarization. Further, the feedline is modified so that the senses of polarization at the two bands are opposite. By introducing PIN-diodes in the feed lines, polarization can be switched among left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP). A prototype dual-band dual-sense antenna with f 01  = 1.9 GHz and f 02  = 3.45 GHz is fabricated in a 1.6 mm thick FR4 substrate. The measured circular polarized bandwidths are more than 7.6 % for the lower band and 5 % for the upper band.