Double-sided Parallel-strip Line Research Articles

Double-Sided Parallel-Strip Line Resonator for Dual-Polarized 3-D Frequency-Selective Structure and Absorber

Double-sided parallel-strip line (DSPSL) resonator is employed in the unit cell (UC) of a 3-D frequency-selective structure (3-D FSS) in order to exhibit the desired response (bandstop, bandpass, and absorption) under an incident wave of arbitrary polarization. It is found that this UC supports the propagation of three quasi-TEM modes. The first and third modes are concentrated in the substrate and air regions of the UC, respectively. While the second mode is concentrated in the interface between air and substrate of the UC, the polarization of the second mode is perpendicular to the polarization of the first and third modes. Detailed analysis of these propagating modes is provided with equivalent circuit models to explain the operating principle. A dual-polarized bandstop 3-D FSS is then proposed. It exhibits a stable frequency response with a constant out-of-band bandwidth under a large range of oblique incidence angle. A dual-polarized absorber is also realized employing a UC with DSPSL resonator. By properly exciting and absorbing the second mode of the modified UC, an ultra-wideband absorber is constructed, which has −10 dB fractional bandwidth of 148% from 1.51 to 10.1 GHz with an absorber thickness of $0.1~\lambda _{0}$ at the lowest absorption frequency.

Antipodal Vivaldi antenna with novel differentially fed structure for lowering cross‐polarisation level

A novel differentially fed double-slot structure with two metal layers is proposed for an antipodal Vivaldi antenna. When fed differentially, the slots can have their E-field vectors summed to an E-field vector parallel to the layers, which endows the antenna with a significantly lowered cross-polarisation level by comparison with a typical antipodal Vivaldi antenna whose E-field vectors in the slot are skewed to the layers. A wideband balun based on a double-sided parallel stripline is used to realise the demanded differential feeding. The simulation and measurement are carried out to validate the remarkable characteristic of a two-layer structure, which is simpler than a three-layer structure of a balanced antipodal Vivaldi antenna.

Three‐dimensional high‐isolated dual‐band balun using double‐sided parallel‐strip line with inserted conductor plane

A novel three-dimensional high-isolated dual-band balun is proposed for the first time. A horizontal feeding plane, a vertically mounted plane, and four grounded resistors constitute the entire structure. By introducing the double-sided parallel-strip line with an inserted conductor plane to the middle of the vertical plane, the output matching and isolation, frequency-independent phase difference, and complete ground in the bottom layer of the horizontal plane are perfectly integrated in this novel balun. To prove this conception, a practical balun operating at 1.3/2.5 GHz is designed. As expected, remarkable consistency between the simulation and measurement is obtained.

A Nonbalancing End-Fire Microstrip Dipole With Periodic-Offset DSPSL Substrate

A nonbalancing microstrip dipole with end-fire capability is presented. The proposed antenna consists of a simple microstrip-fed dipole with a periodic-offset double-sided parallel-strip line (DSPSL) substrate, which is used to replace the balun of a conventional end-fire antenna. The periodic-offset DSPSL substrate exhibits phase shift characteristics and excites the odd mode of the microstrip dipole. A director and a truncated ground are used to increase the directivity of the antenna. After placing the DSPSL, the bidirectional radiation pattern is converted to a unidirectional one. The measured and simulated results indicate that the antenna operates at 2.4 GHz. End-fire directional radiation patterns are obtained with this novel periodic substrate. When compared with the original design of the microstrip dipoles, the proposed microstrip dipole uses the periodic-offset DSPSL substrate to replace the balun. The front-to-back ratio is about 10 dB. The design method of the end-fire antenna is a new technique and can be easily applied in other antennas.

A Low-Profile Omnidirectional Circularly Polarized Antenna Using Planar Sector-Shaped Endfire Elements

A single-layer circularly polarized (CP) antenna with omnidirectional radiation in the azimuth plane has been designed and evaluated. The concept is the combination of multiple identical endfire CP antenna elements in a circular array configuration. The design of each element is based on the superposition of two closely spaced complementary current sources, which are, respectively, realized by a sectorial parallel-plate cavity and arc-shaped strip arms. A meandered double-sided parallel strip line is introduced to adjust the phase relationship between two orthogonal linear polarized components. All antenna elements can be simultaneously excited by adopting a single coaxial probe in the center of the overall structure. Take 5.8-GHz Industrial Scientific Medical (ISM) band applications (5.725–5.875 GHz), for example, a prototype with a diameter of $0.62\lambda _{0}$ and a low profile of $0.029\lambda _{0}$ was fabricated. Experimental results show that the designed antenna has a usable bandwidth from 5.68 to 5.91 GHz (the common overlapped bandwidth limited by the −10 dB $\vert S_{11}\vert $ and the 3-dB axial ratio). Within the operation band, good omnidirectivity and a wide coverage can be obtained.

Out-of-Phase Power Divider with Complex Impedance Transformation Based on Miniaturized Isolation Network

ABSTRACTA compact three-layer circuit structure based on the double-sided parallel-strip lines (DSPSLs) is proposed in this article to design an out-of-phase power divider (PD) with miniaturized isolation network. This PD, of which the source- and load-impedances are both complex, consists of three DSPSLs for the signal transmission, a conduct plane in the middle, and two resistors for high outputs isolation. The traditional even- and odd-mode method is used to obtain the close-form equations of this proposed PD, and its scattering parameters are also derived. Finally, a practical out-of-phase PD, which operates at 1.8 GHz, is designed and fabricated. The simulated and measured results in terms of scattering parameters as well as the phase difference of two output signals show that this PD features equal power division with out-of-phase, good ports matching, and high isolation, which verify the design theory.

A Printed LPDA Antenna Fed by a Microstrip Line to Double Sided Parallel Strip Line from Backside

A novel planar printed log-periodic dipole array (LPDA) antenna fed by tapered microstrip line (MSL) to double sided parallel strip line (DSPSL) is proposed in this paper. The proposed antenna adopts MSL feeding approach from backside. Using this feeding technique makes the printed LPDA antenna easier to be integrated into radio frequency (RF) circuits. In this paper, four layers are used to construct the antenna. The four layers of the printed LPDA antenna are printed on three thin dielectric substrates which are integrated together. To validate this approach, a printed LPDA antenna is simulated and fabricated for operating in the S and C bands (2.5–6 GHz). The antenna showed a good result over the whole frequency range with 2 : 1 VSWR, an average gain of 6.5 dB, and stable radiation patterns. The measured results are in very good agreement with simulations.

A Miniaturized 4 : 1 Unequal Wilkinson Power Divider Using Artificial Transmission Lines and Double-Sided Parallel-Strip Lines

A 4 : 1 unequal Wilkinson power divider using microstrip artificial transmission lines (ATLs) is proposed. For the ATL, a series of meandered-line inductors, parallel-plate capacitors, and interdigital capacitors are employed. The designed power divider is composed of three ATLs, and a method has been proposed using technology of ATLs and double-sided parallel-strip lines (DSPSLs) to design line of high characteristic impedance. Microstrip line with very high characteristic impedance of over 150 Ω has been achieved by this method, which cannot be easily achieved by conventional transmission lines because of comparably thin conductor width. The fabricated 4 : 1 unequal power divider has good operational performance and occupies55.3 mm×37.8 mm, which is only about 40% of area compared to a conventional one at 0.9 GHz.

Single-Layer Circularly Polarized Antenna With Fan-Beam Endfire Radiation

A single-layer single-fed endfire antenna with circularly polarized radiation has been designed and evaluated. The concept is the superposition of two closely spaced complementary dipoles. In terms of implementations, a shorted parallel-plate cavity serves as the magnetic dipole, while double-side-printed conductor arms act as the electric dipole. To satisfy the required magnitude/phase relationship between two dipoles, a T-shaped double side slot-coupled line and a meandered double-side parallel strip line are introduced. With analyses of equivalent models, the operation mechanism and design guidelines can be obtained. Taking 5.8-GHz ISM band (5.725–5.875 GHz) for example, the measured results show that the designed antenna has an impedance bandwidth $({| {S_{11}} | from 5.7 to 5.9 GHz (3.5%) and a 3-dB axial-ratio (AR) bandwidth from 5.65 to 5.9 GHz (4.3%). The effective beamwidth in the azimuth/elevation plane is 85°/168° at 5.8 GHz.

A Broadband Offset-Parallel-Parallelograms Printed Endfire Antenna

A broadband offset-parallel-parallelograms printed endfire antenna is presented. The proposed antenna consists of a pair of offset parallel parallelograms, the driver dipoles, the offset double-sided parallel-strip line, and a reflector. The top and bottom patches are printed in parallel on two sides of a substrate plane. The characteristics of the offset parallel parallelograms are studied and discussed. The calculated results fit in well with the results obtained by simulation with ANSYS HFSS. The broadband endfire radiating patterns were achieved. The measured bandwidths were 73.3% for the frequency band (0.89-1.92 GHz), and the gain was about 3.3-4.8 dBi in the operating band.

A Generalized Lossy Transmission-Line Model for Tunable Graphene-Based Transmission Lines with Attenuation Phenomenon.

To investigate the frequency shift phenomenon by inserting graphene, a generalized lossy transmission-line model and the related electrical parameter-extraction theory are proposed in this paper. Three kinds of graphene-based transmission lines with attenuation phenomenon including microstrip line, double-side parallel strip line, and uniplanar coplanar waveguide are analyzed under the common conditions where different chemical potentials are loaded on graphene. The values of attenuation constant and phase constant, and the real and imaginary parts of the characteristic impedance of transmission lines are extracted to analyze in details. When the attenuation constant and the reactance part of the characteristic impedance are approximately equal to zero, this kind of transmission line has low or zero insertion loss. On the contrary, the transmission line is under the radiation mode with obvious insertion loss. The phase constant changes linearly under the transmission mode and can be varied with changing of chemical potentials which attributes to the property of frequency tunability. Furthermore, a bandwidth reconfigurable uniplanar coplanar waveguide power divider is simulated to demonstrate that this theory can be applied to the design of three-port devices. In summary, this work provides a strong potential approach and design theory to help design other kinds of terahertz and mid-infrared reconfigurable devices.

A broadband out-of-phase gysel power divider based on a dual-band circuit with a single fixed isolation resistor

Based on the double-sided parallel-strip lines with an inserted conductor as a virtual ground, a high power divider with dual-band/broadband response and frequency-independent 180° phase difference between the output ports is implemented in this paper. The circuit topology employs a single commercially available external isolation resistor as well as moderate line impedances (15–100 ohm), making it suitable for high-power applications. Precise closed-form design equations on the basis of even- and odd-mode analysis are derived. In addition to the wide range of frequency band ratios from 1 to 2.65, broadband response is also obtained by selecting the proper value of frequency band ratios. To substantiate the design equations and theory, a circuit with 2:1 frequency ratio and 84.5% bandwidth referring to 16 dB isolation and 12 dB return loss values is developed. To the authors' knowledge, this is the widest bandwidth reported for out-of-phase high power dividers. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016.

Dual-Band Out-of-Phase Power Divider with Impedance Transformation and High Power-Handling Capability

ABSTRACTA novel dual-band out-of-phase power divider with inherent impedance transformation and high power-handling capability is presented in this article. This proposed power divider essentially consists of four sections of double-sided parallel striplines for the signal transmission, an inserted middle conductor plane as the common ground, and two resistors to improve the isolation between two outputs. Closed-form design equations are derived based on the conventional even- and odd-mode analytical methods and the transmission-line theory. Finally, a practical three-layer out-of-phase power divider is designed and fabricated. The experimental results show that good ports matching, excellent isolation between two outputs, and out-of-phase performance are simultaneously achieved at both 1 and 2.6 GHz.

Two‐arm Archimedean spiral antenna fed by broadband double sided parallel strip line

ABSTRACTThis paper is intended to introduce a two‐arm Archimedean spiral antenna fed by a novel feed structure based on DSPSL (Double Sided Parallel Strip Line). A DSPSL provides an ease perpendicular matching network and an impedance transition between input impedance of a spiral antenna and system's impedance of 50 Ω in broadband frequency range. Measured and simulated VSWR and radiation pattern results show a good performance over ultra‐wide band from 2 to 20 GHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1879–1883, 2016

A Balanced-to-Balanced Network With Unequal Power Division and Wideband Common Mode Suppression

A novel wideband balanced-to-balanced network with unequal power division is proposed in this letter. Two open stubs and half-wavelength transmission lines are used to realize wideband common mode suppression, two ideal double-sided parallel-strip line (DSPSL) 180 $^{\circ}$ phase inverters with isolation resistors are used to realize high isolation for the power dividing output ports. A planar wideband balanced network with bandwidth of 38.6% (power division ratio: $1:2^{2}$ ) for the differential mode and over 113.6% common mode suppression (1.06–3.56 GHz, $| S_{{cc}21,31}| ) is designed and fabricated.

UWB balun with complete ground based on vertically mounted planar structure

A novel UWB balun with complete ground based on vertically mounted planar structure is presented. Two mutually perpendicular planes comprise the proposed balun. The vertical configuration of double-sided parallel-strip line ensures complete ground in the horizontal plane and the cascading of seven-section quarter-wavelength transformers facilitates UWB functionality. For verification, a prototype balun is designed, fabricated and measured. The simulation and measurement agree well, exhibiting a bandwidth from 0 up to 8 GHz with good return loss, flat insertion losses and high stability of 180° phase difference.

Dual‐band GaN power amplifiers with novel DC biasing networks incorporating offset double‐sided parallel strip line

This study presents a novel dual-band DC biasing network and its application in the design of GaN power amplifiers (PAs). By integrating offset double-sided parallel strip line which can easily realise high characteristic impedance and thus narrow microstrip line, the proposed biasing network can obtain much higher operation frequency ratio than the conventional design. To demonstrate the new methodology, two dual-band GaN PAs applying the presented dual-band DC biasing network are implemented. The operation frequencies are 1.8/3.5 and 0.9/3.5 GHz. Three-section networks for complex load are used for dual-frequency input and output matching. Good agreement between the simulation and measurement is observed, which fully demonstrate the feasibility and validity of the presented DC bias networks in power amplifier designs.

A novel three-dimensional dual-band balun with frequency-independent phase difference and complete ground

A novel three-dimensional (3D) dual-band balun employing the double-sided parallel-strip line (DSPSL) with inherent impedance-transforming capability and complete ground is presented in this paper. The proposed balun is mainly composed of two mutually perpendicular printed circuit boards (PCBs), one of which is a horizontal feeding plane with a slender slot and the other of which is a mounted board vertical to the former.An unbalanced input port and two balanced output ports are totally located at the feeding plane. Utilising the configuration of DSPSL, two different dual-band impedance transformers of two sections are placed in the top and bottom layers of the vertical mounted board respectively. Thus, the transformers are applicable to transform impedances at two frequencies simultaneously. Furthermore, the 180° phase difference is frequency-independent, which facilitates the broadband operation. For verification, two numerical examples with different frequency ratios are designed and simulated, one of ...

A Dual-Band Printed End-Fire Antenna with DSPSL Feeding

A novel dual-band printed end-fired antenna with double-sided parallel-strip line (DSPSL) feeding is presented. The DSPSL acts in wideband transition using balanced transmission. Two different modes of the parasitic patches allow the antenna to work in different bands. The printed antenna is designed as a quasi-Yagi structure to achieve directivity in the lower band, and the parallel rectangular patches serve as the parasitic director. These patches act as radiation patches with end-fire direction characteristics in the upper band. The measured bandwidths were 18.3% for the lower frequency band (2.28–2.74 GHz) and 12.6% for the upper frequency band (5.46–6.2 GHz).

Planar Image-Reject Bow-Tie Antenna With Gain Enhancement for Superheterodyne Applications

A planar bow-tie antenna loaded with open stubs is proposed to realize image rejection and gain enhancement for superheterodyne applications. The loading open stubs are two open-circuit double-sided parallel-strip lines symmetrically connected to the feedline of a planar bow-tie antenna, which functions as a bandstop filter in frequency band lower than the operating frequency to reject image interference and simultaneously as a reflector across the operating frequency band to enhance the antenna gain. Simulated results show that the realized gain of the proposed antenna in the main radiation direction is suppressed by 25 dB at the image frequency and is enhanced by about 3 dB at the operating frequency compared to that of an unloaded antenna. Good agreements between the simulated and the measured results have been observed.