This paper presents the design of compact second-order bandpass filters based on dual-mode open-loop resonator. A filter design procedure is provided to facilitate the design process. The paper also describes the nature of the inherent transmission zero associated with the structure and presents a method of generating two additional zeros for improving stop-band performance. Finally, a filter design example is presented to validate the argument.
A doubly balanced monolithic microwave passive mixer using novel configurations is designed and fabricated through a 0.15 μm GaAs pHEMT process. The configuration of the doubly balanced mixer (DBM) can eliminate the use of two dual baluns for application in the conventional star mixer, as well as make the mixer more compact and simplify IF extraction to obtain wider IF bandwidth up to 15 GHz. From the measured results, the fabricated DBM exhibits wideband performance, superior isolations and high dynamic range.
In this letter, a compact and high selectivity broadband bandpass filter (BPF) is proposed using the dual-mode folded-T-type resonator and the short stub loaded parallel-coupling feed structure. The resonator can generate one even-mode and one odd-mode in the desired band. Two resonant frequencies can be adjusted easily to satisfy the bandwidth of the BPF. A parallel-coupling feed structure with a cross coupling has been applied to generate two transmission zeros in the lower and upper stopband. Furthermore, the loaded short stub can create two transmission zeros near the upper cut-off frequency and in the upper stopband. Simultaneity, the transmission zero in the lower stopband moves towards the cut-off frequency. One filter prototype with the fractional bandwidth 57% is fabricated for experimental verification of the predicted results. The size for the resonator is only 0.156λg×0.303λg in which λg is the guided wavelength of 50 Ω microstrip at the center frequency.
A simple electromagnetically coupled broadband printed microstrip antenna suitable for multifunctional wireless communication bands is presented. V-slots and corner notches are employed in a rectangular patch to achieve broadband operation. The proposed antenna has a 2:1 VSWR bandwidth of 51% from 3.75 GHz to 6.33 GHz. The simulated and measured reflection characteristics of the antenna along with the radiation patterns and gain are presented and discussed.
Scattering of electromagnetic (EM) waves by many small particles (bodies), embedded in a thin layer, is studied. Physical properties of the particles are described by their boundary impedances. The thin layer of depth of the order O(a), with many embedded small particles of characteristic size a, is described by a boundary condition on the surface of the layer. The limiting interface boundary condition is obtained for the effective EM field in the limiting medium, in the limit a→0, where the number M(a) of the particles tends to infinity at a suitable rate.
This work presents the analytical solution of vector wave equation in fractional space. General plane wave solution to the wave equation for fields in source-free and lossless media is obtained in fractional space. The obtained solution is a generalization of wave equation from integer dimensional space to a non-integer dimensional space. The classical results are recovered when integer-dimensional space is considered.
The total scattering cross section (TSCS) of various targets is computed in this letter from a numerical method in a reverberation chamber (RC). Theoretically TSCS measurements need both a free-space environment (for instance anechoic chamber modeled numerically by absorbing boundary conditions) and various plane waves' stimulations. The method developed allows predicting the TSCS from few simulations in a RC. The foundations and numerical results presented demonstrate the ability of the technique to straightforward compute the TSCS with the finite difference in time domain (FDTD) method. The agreement from these TSCS treatments in RC is finally obtained considering the expected results in free-space.
This is paper discusses the inverse Joukowski mapping, w=z+√{z2-c2} (c>0), which can be classified into active and passive inverse transformation. By using the active inverse Joukowski mapping, the generalized image problems that the line charge ρl is located outside the elliptical conducting cylinder, or the finite conducting plate can be solved. By using the passive logarithmic inverse Joukowski mapping, the capacitance C of a finite conducting plate placed vertically above the infinite conducting plate can be solved. Thus the conformal mapping method can replace the image method and electrical axis method become the uniform method to solve the electrostatic problems.
The effect of shaping the ground plane on the performance of a square loop coplanar waveguide (CPW)-fed printed antenna is reported in this paper. Experimental results are presented on the reflection coefficient and radiation pattern of the investigated antennas. Simulation results are presented on the current distribution and gain. It is observed based on the results that shaping the ground plane significantly affects the reflection coefficients and current distributions.
A planar dual-composite right/left-handed (D-CRLH) transmission line (TL) structure is proposed. The characteristics such as dispersion relation and frequency response of this D-CRLH TL are analyzed by equivalent circuit analysis, Bloch-Floquet theory, full wave simulation and experiment. To demonstrate applications of the proposed structure, both bandstop filter and leaky-wave antenna are designed and implemented by the conventional print circuit board technology. The fabricated filter has a broad application because of its planar structure, small size and tunable stopband. The measured results also suggest that the leaky-wave antenna based on the D-CRLH concept can offer a scanning angle covering almost backfire-to-endfire directions.
We propose a switchable and wavelength spacing tunable multi-wavelength fiber optical parametric oscillator (MW-FOPO) with two cascaded fiber Bragg gratings (FBGs). The MW-FOPO can operate at two multi-wavelength lasing modes with different wavelength spacings, which can be switched by adjusting some polarization controllers (PCs). Stable multi-wavelength lasing at those two different operation modes at room temperature is achieved due to the four wave mixing (FWM) effect and the broadband gain of the fiber optical parametric amplifier (FOPA) based on a highly nonlinear fiber. The wavelength spacing of the proposed MW-FOPO can be tuned by adjusting the wavelength of the pump light or the central wavelength of the FBG at the two multi-wavelength lasing modes.
In this paper, a tunable coplanar waveguide (CPW) line using the bismuth zinc niobate (BZN) thin film has been proposed and demonstrated for low-voltage phase shifter applications. In order to reduce the operation bias voltage the air gaps between the signal strip and ground plane are filled with the tunable thin films. At low E-fields of 1.3 kV/cm, the fabricated CPW line shows the phase difference of 10 degree at 10 GHz.
A miniaturized ultra-wideband (UWB) bandpass filter (BPF) with U-slot etched around the metallic via in the ground is proposed based on a simplified composite right/left-handed transmission line (SCRLH TL) structure. The U-slot etched in the ground makes it feasible to reduce the overall size. A demonstration of FCC standard UWB bandpass filter (BPF) is designed, fabricated and measured. Very good agreement is shown between measurement and simulation.
In this paper the microwave images of two-dimensional section of multiple objects are formed by using the wideband range profiles of the target. Scattered electric field is obtained by the designed two-dimensional imaging system and Fourier transformed into the highly-resolved range profiles while the target rotates. A filtered back-projection (FBP) algorithm is implemented to form the image from the space domain range profiles. Images of multiple cylindrical rods from both numerically simulated and measured data indicate that the approached imaging scheme can achieve high dynamic range and can be potentially implemented for biomedical imaging detections.
A modified UWB power divider formed by installing one delta stub on each branch is proposed. Delta stub is used as a substitution of radial stub that can present wideband characteristic. The proposed structure makes branch line shorter and stub's size smaller than those of similar works based on UWB power divider using radial stub. It also achieves a compact size of 18 mm by 13 mm. The simulation and measurement results of the developed divider are presented and shown good agreement in the UWB range.
This work proposes a substrate integrated waveguide (SIW) power divider employing the Wilkinson configuration for improving the isolation performance of conventional T-junction SIW power dividers. Measurement results at 15 GHz show that the isolation (S23, S32) between output ports is about 17 dB and the output return losses (S22, S33) are about 14.5 dB, respectively. The Wilkinson-type performance has been greatly improved from those (7.0 dB~8.0 dB) of conventional T-junction SIW power dividers. The measured input return loss (23 dB) and average insertion loss (3.9 dB) are also improved from those of conventional ones. The proposed Wilkinson SIW divider will play an important role in high performance SIW circuits involving power divisions.
A new adjustable Electromagnetic Band-Gap (EBG) structure whose frequency response is controllable by adjusting spacer height is proposed. The finite difference time domain method is adopted for the simulations. Results show that the desired frequency response can be selected by adjusting the spacer height. The effects of the air-gap on the polarization dependent and conventional EBG structures have been investigated both theoretically and numerically. The agreement between the theoretical calculations and numerical results is reasonably good.
In this paper, a novel hybrid dielectric resonator (DR) antenna for Ultrawideband (UWB) short-range wireless communications is proposed. The proposed antenna consists of a microstrip fed monopole loaded with a half cylindrical dielectric resonator antenna of Rogers RO3010 mounted on RT5880 substrate with a finite ground plane. The microstrip line fed monopole antenna is on the other side of the substrate. Compared to the conventional circular cylindrical DR mounted on a finite ground plane (reference antenna), the proposed antenna has a reduction in the antenna size by about 30% with a bandwidth increase by about 22% than the reference antenna. The proposed antenna has a good impedance bandwidth. In addition, the proposed antenna has a quite higher and more stable gain than that of reference antenna. Moreover, the antenna has a good omni-directional radiation patterns in the H-plane. The proposed antenna is considered a good candidate for UWB short-range wireless communication systems.
This article presents a simple structure for reducing mutual coupling between two diversity planar monopole antennas for WLAN 5.2/5.8 GHz applications. The structure has two λ/4 (λ-wavelength in the substrate) slots cut into the ground plane between the two monopoles. In 0.5 λo (λo,-wavelength in the air) of the antenna spacing, mutual coupling was -33.3, -21.1 dB at 5.2, 5.8 GHz, respectively. The lowest mutual coupling of -33.3 dB was achieved at 5.2 GHz, which is 20.8 dB improvement over the reference.
A compact ultra-wideband microstrip-fed planar monopole antenna with dual band-notch characteristic is presented. Dual notched frequency bands are achieved by embedding an M-slot in the radiating patch and a W-slot in the ground beneath the feeding line. And the characteristics of the dual band-notched can be controlled by adjusting the length and position of the corresponding slot. Experimental results show that the proposed antenna, with compact size of, has an impedance bandwidth of 2.75~11.30 GHz for VSWR less than 2.0, except two notched bands of 3.25~4.20 GHz and 5.23~6.10 GHz. Moreover, this antenna exhibits good omnidirectional radiation patterns in the H-plane, stable antenna gains over the operation band, and perfect group delay in the time-domain.
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