Parallel-strip Line Research Articles

A Broadband Ultra-Thin Polarization Rotator Using Periodically Loaded Parallel Strip-Lines

A polarization rotator based on loaded parallel strip-lines is theoretically and experimentally investigated. The unit cells are short-stub loaded parallel strip-lines. The arrays on the front and back layers are rotated by 90° to each other. By loading the stubs, good coupling between the two layers is obtained. Such a structural rotation along with the loading stubs allow the $y$ -polarized wave to be converted to $x$ -polarized wave through field coupling. A broad transmission bandwidth of 30% (86-116 GHz) by using the proposed structure has been reached. In addition, the PTFE substrate is only 0.25 mm thick, which is less than $0.1\lambda $ at 86 GHz. Such a thickness allows the polarization rotator to be easily mounted on antenna radomes. The fabricated prototype demonstrates good agreement between simulation and measurement results.

Common-Mode Noise Absorption Circuit Using Double-Sided Parallel-Strip Line

This letter presents a common-mode noise absorption (CMNA) circuit using the double-sided parallel-strip line (DSPSL). The circuit behaves as a pair of conventional transmission lines (TLs) under differential-mode (DM) excitation. The common-mode (CM) noise is suppressed and absorbed by the surface-mounted resistors between the two TLs. Based on analytical design equations, the values of the surface-mounted resistors can be calculated, and a high-efficiency CM absorption at the wide frequency band can be obtained. Finally, a practical CMNA circuit with wideband CM absorption is designed and fabricated to verify the design theory.

High Performance Balanced Bandpass Filters With Wideband Common Mode Suppression

Two compact and high selectivity balanced bandpass filters with excellent common mode rejection are designed in this brief. Compared with the half-wavelength microstrip transmission line, 180° phase shift is realized by two small swap structures, which are composed by double-sided parallel-strip line (DSPSL), and this way can easily realize a wideband common mode rejection with compact circuit size. Two out-of-band transmission zeros are introduced by the dual-mode ring resonator in the first proposed structure; thus, high selectivity can be achieved. In the second filter, shorted/open coupled microstrip lines are added between the dual-mode ring resonator and 180° swap structure, two additional transmission zeros can be achieved. Finally, two prototypes center at 2.2 GHz are fabricated, and the measured 3-dB bandwidths for the differential mode are 23.6% and 11.8%, respectively.

A Patch Antenna Coupling of Periodic Leak-Wave Structure With Tri-Frequency Capability

A patch antenna coupling of a periodic leak-wave structure with tri-frequency capability is proposed. The periodic offset double-sided parallel stripline (DSPSL) leaky wave structure (LWS) is embedded in the direction of the whole ground of the microstrip patch substrate, then the capability of tri-frequency could be obtained by the different Floquet mode of the propagation constant. According to the design principle, a unified formula was derived to calculate the tri-frequency points at the same time. Though applying of antenna design principle and the simple tri-frequency formula, a tri-frequency patch antenna was designed and tested. Experiment results show that the antenna operated at 1.71, 2.05, and 2.72 GHz. The measured and calculated results show high consistency.

General Design Technique for High-Gain Traveling-Wave Endfire Antennas Using Periodic Arbitrary-Phase Loading Technique

This article proposes a general design technique for high-gain traveling-wave endfire antennas using a periodic arbitrary-phase loading technique. This work extends the periodic phase-reversal techniques reported in previous work to application scenarios where phase reversals are difficult to realize (e.g., single-layer circuits). It also relaxes the substrate permittivity requirement in phase-reversal techniques. To verify the proposed technique and theory, two design examples using different phases other than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> are provided. Double-side parallel stripline and coplanar stripline are employed to provide vertical and horizontal polarizations, respectively. Double-side parallel stripline antenna achieves a maximum endfire gain of 15.6 dBi with vertical polarization. The coplanar-stripline antenna exhibits a maximum endfire gain of 16.6 dBi with horizontal polarization. The experimental results of these two examples validate the proposed technique.

A Three-Dimensional Design of Ultra-Wideband Microwave Absorbers

A three-dimensional (3-D) structure is proposed in this article for ultra-wideband absorber design. The ultra-wideband absorber is implemented by properly combining two subabsorbers. The first subabsorber operates in its fundamental mode ( $f_{0}$ ) and the third-order mode ( $3f_{0}$ ). Its lossy layer is designed with an infinite impedance at the second-order mode frequency ( $2f_{0}$ ). The second subabsorber is designed to operate in its fundamental mode frequency, which is corresponding to $2f_{0}$ of the first subabsorber. A double-sided parallel-strip line (DSPSL) is employed to produce the required infinite impedance of the first absorber. A simple equivalent circuit model of the DSPSL is established to explain the operating principle. A conventional parallel LC circuit is also provided for comparison to show the advantages of the DSPSL. Single-polarized and dual-polarized ultra-wideband absorbers are designed by combining these two subabsorbers, and their simulated fractional bandwidths (FBWs) of 151.6% and 150.9% are achieved, respectively. A prototype of the dual-polarized ultra-wideband absorber is fabricated and measured to validate the design concept. Its measured absorption band from 1.50 to 12.31 GHz with an FBW of 156.6% is in a good agreement with the simulated one. The proposed absorber features a wide absorption band and few lumped elements, which makes it more useful in practical applications.

A compact wideband balun design using double‐sided parallel strip lines with over 9:1 bandwidth

A simplified miniaturized wideband balun design covering (0.38-3.5 GHz) is presented. The broadband balun structure occupies a small area of 20.7 mm × 20.8 mm. The balun is designed using low loss double-sided parallel strip lines and is comprised of a two-stage Wilkinson divider followed by loading, symmetrically, the two output ports. One port with a phase inverter circuit; while a very similar but non-inverting circuit is placed in the other port for loading-balance compensation. To realize the balun's function, different smooth transitions have been employed and were accounted for. The fabricated balun circuit demonstrated phase and amplitude imbalance of less than ±5° and ± 0.4 dB, respectively, over the band.

A Novel Leaky Wave Endfire Filtering Antenna Based on Spoof Surface Plasmon Polaritons

A novel leaky wave endfire filtering antenna based on spoof surface plasmon polaritons (SSPPs) is proposed. The structure of leaky wave antenna consists of multiple radiating elements and one double-sided parallel strip line (DSPSL), and the filtering performance is realized by adding stubs with via holes. The structure with a periodic arrangement of the radiating elements has similar dispersion curves of SSPPs, which has low-pass transmission characteristic and also can radiate energy to the free space. According to the measured results, a peak gain of 8.65 dBi at a center frequency of 7.7 GHz and a bandwidth of 36.36% can be achieved for the leaky wave endfire filtering antenna based on SSPPs. The out-of-band rejection is over 13 dB.

Multi-way differential power divider with microstrip output interfaces

Abstract The design and implementation of planar multi-way differential power dividers remain a challenge in terms of the compactness and especially, for the achievable characteristic impedance of the quarter-wavelength transformer when considering large number of outputs. In this work, the double-sided parallel stripline is recommended to realize such a power divider with out-of-phase outputs, and explicit design methods are provided. The proposed multi-way power divider was developed without the use of lump elements on a single substrate. For system applications, a prototype operating at 41.6 MHz with 12 pairs of out-of-phase outputs that utilize the microstrip line as the output interfaces was fabricated and examined. At the center frequency of 41.6MHz, the developed prototype measured insertion losses akin to 14.3 dB as compared with the theoretical data of 13.8 dB. The attainable impedance bandwidth ranges from 10 MHz to 80 MHz under a magnitude imbalance of ±0.3 dB. The isolations of the adjacent outputs are about 13.1 dB as compared with the theoretical values of 14.428 dB, and are better than 34 dB for more distant ones. Parameter measurements are in good agreement with the numerical predications, thus demonstrating the realization of the proposed multi-way power divider.

Characteristics of the Angled Printed Dipole Array Antenna with Different Numbers of Dipole Elements

This paper investigated the characteristics of series-fed angled dipole antennas as the number of dipoles increased from one to two, four, and eight. A parallel strip line printed on both sides of the substrate was used to connect angled printed dipoles of the same size in a series with equal spacing. As expected, although the gain increased as the number of dipoles increased, the impedance and gain bandwidths decreased. In addition, as the number of dipoles increased, the half-power beamwidth (HPBW) differences between the xz- and yzplanes decreased and the radiation pattern of the xz-plane became more symmetric. Antennas with one, two, four, and eight-dipole elements in a series were designed, and their peak gains were 5.0 dBi, 7.2 dBi, 9.4 dBi, and 10.4 dBi, respectively. The differences between the xz- and yz-plane HPBWs of the four antennas were 160.4°, 41.7°, 14.2°, and 5.3°, respectively. As the number of dipoles in the antenna increased, the differences between the HPBWs in the xz- and yz-planes decreased.

Re-adjustments for MOM calculations of microstrip and stripline power dissipation

AbstractMicrostrip and stripline losses in Method of Moments (MOM) calculations have an error arising from the large current density at the strip edges, characterized by an integration limit (W/2-d) in the equation for current density in thin strips (width W), where d is a fitting parameter. It depends primarily on the width of the MOM subsection on the edge of the strip. By comparing with the integration limit (W/2-Δ) for an actual strip with finite thickness, a correction factor is estimated. The equations incorporating d are confirmed by comparing with MOM calculations of isolated stripline, uniformly spaced parallel strips, striplines and microstrips close to ground planes, and with a strip in a uniform, externally applied magnetic field. The results are also consistent with measurements with copper. This makes the accuracy of the loss estimates commensurate with the excellence of the other aspects of MOM simulations.

Bandpass Absorptive Frequency-Selective Structure Using Double-Sided Parallel-Strip Lines

A novel design method of bandpass absorptive frequency-selective structure (AFSS) is presented in this letter. The proposed AFSS is based on double-sided parallel-strip lines (DSPSLs), which is different from those based on the conventional parallel L-C resonator. Its lossy layer of a unit cell consists of the DSPSLs and striplines loaded with four lumped resistors, in which one end of the DSPSL connects to the stripline and the other end is open. The proposed AFSS is implemented by mounting the lossy layer in front of a bandpass FSS, which is constructed by a square-loop slot etched on a metal plate. In the transmission band, the lossy layer is designed as an infinite impedance by introducing the DSPSLs, and then, the lossy layer is transparent to the incident wave. In the absorption bands, the incident wave is reflected by the bandpass FSS and then dissipated by the lossy layer. The proposed AFSS is fabricated and measured. It has a passband of 5.49-6.09 GHz, two absorption bands of 2.63-5.19 GHz and 6.37-8.45 GHz, and stable performance under oblique incidence. It has a compact structure of 0.18λ a × 0.18λ a × 0.09λ a , where λ a is the wavelength of the lowest absorption frequency.

A High-Gain and Wideband Series-Fed Angled Printed Dipole Array Antenna

In this communication, we have proposed a nonuniform series-fed angled dipole array antenna with a high gain, a wide bandwidth, a good sidelobe level (SLL), and a high front-to-back ratio characteristics. The proposed array antenna structure consisted of eight dipole elements, and each dipole was connected to a parallel stripline printed on the front and back sides of the substrate. From the first dipole element near the ground plane to the eighth dipole element at the end of the parallel stripline, the length of each dipole was reduced by ΔL <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> . As with dipole length, the spacing between the dipole elements decreased by ΔS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> from each previous dipole spacing. Compared to uniform array antennas, the impedance and gain bandwidths were greatly increased, and the SLL and front-to-back (F/B) ratio characteristics were improved. The proposed array antenna had an |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB, an impedance bandwidth of 23.3-51.0 GHz, and a 3 dB gain bandwidth of 22.0-44.0 GHz. At 28 GHz, the E- and H-plane SLLs of the proposed array antenna were -24.1 and -18.8 dB, respectively. The F/B ratio of the proposed antenna was less than -30 dB.

A UHF Deployable Log Periodic Dipole Antenna: Concept, Design, and Experiment

A deployable log periodic dipole antenna (DLPDA) is proposed. The antenna consists of pairs of collapsible steel tape springs (as the dipoles), a novel stretchable zigzag double-sided parallel stripline (ZDPS) (as the boom), and a coplanar waveguide on one side of the parallel striplines to guide the electromagnetic wave from the backend to the frontend. As a result, the proposed antenna becomes foldable and can be stored in a small volume prior to deployment. A design guideline for the DLPDA is given based on the simplified circuit model. Furthermore, the ZDPS, which is found as a slow wave structure, has been studied. The empirical equations are derived to obtain its characteristic impedance and propagation constant, which are the key parameters for the design guideline. One prototype of the DLPDA has been fabricated and tested. The deployment mechanism of the prototype has been successfully demonstrated using compressed air in a lab. The prototype has a stowed volume of <; 2000 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , which is only 2% of the volume in fully deployed state.

Novel planar quasi‐TEM transmission line with high isolation and its application to T‐junction power divider

In this study, a novel quasi-transverse electromagnetic (TEM) transmission line (TL) on a single-layer substrate is presented. The proposed structure comprises bilateral metalised vias and two longitudinal slots on the top and bottom plates, respectively. This two-conductor TL separated by the two slots allows the quasi-TEM mode and guarantees high isolation due to the vias which constrain the electromagnetic field. Additionally, the proposed structure provides a remarkable high range of the characteristic impedance, enabling a more flexible design. Furthermore, an empirical analytical formula is derived to calculate the characteristic impedance of the proposed TL adopting conformal mapping, and modified by a polynomial fraction. The transitions to the double-sided parallel-strip line and the microstrip line are proposed with which the propagation constant of this TL is extracted. The comparisons of the far-end couplings of several types of microwave TLs have been provided by the simulation and measurement to verify the isolation property of the proposed TL. Finally, the proposed TL is applied to the T-junction wideband power divider design to demonstrate its practicability. A prototype is fabricated and measured with a wide operating bandwidth from 6.8 to 17.6 GHz.

Ultra-compact spoof surface plasmon polariton waveguides and notch filters based on double-sided parallel-strip lines

In this paper, we propose a new variety of strong field confinement, ultra-compact size, easy-to-integrate spoof surface plasmon polariton (SSPP) waveguides based on double-sided parallel-strip lines (DSPSL), which are formed by etching opposite spiral grooves on the upper and lower metal layers of the DSPSL. By analyzing the dispersion characteristics, we found that the opposite spiral grooves can significantly reduce the asymptotic frequency of the dispersion curve. Compared with the conventional comb-shaped SSPP structures at the same asymptotic frequency, the size of the structure is reduced to 19.85%, which facilitates miniaturization and integration of microwave devices. A broadband transition is also designed to achieve smooth impedance and momentum matching for the proposed SSPP waveguide. Owing to the dual-conductor structure, the proposed waveguides can be easily integrated with active devices and can also support low-frequency or time-domain signals without causing distortions. The proposed SSPP waveguides have strong field confinement and can concentrate the field around the spiral groove, implying great potential applications in sensing and detection. In parallel, we also designed two notch filters based on the proposed SSPP waveguide, which can achieve adjustable narrowband or broadband filtering by loading different capacitors. The proposed design can be widely used in various plasmonic devices, which opens up a new door to build up large-scale plasmonic integrated circuits in the microwave and terahertz regimes.

Novel Differential Bandpass Filter Using Spoof Surface Plasmon Polaritons

In this article, a novel differential bandpass filter based on periodic spoof surface plasmon polaritons (SSPPs) is proposed. It consists of a pair of double-layer SSPPs using double-sided parallel-strip line (DSPSL), a pair of single-layer SSPPs, and a 180° phase inverter. The transmission characteristics of the proposed SSPPs’ structure are analyzed by the differential-mode and common-mode method, and also applied to design the differential filter. To validate the design concept, a differential filter sample has been designed, fabricated, and measured. The simulated and measured results indicate a 3-dB fractional bandwidth of 25.5% (frequency 5.5 GHz), and a wide 20-dB common-mode suppression from 2.9 to 8 GHz can be achieved for the differential filter.

A Low-Profile and High-isolated MIMO Antenna for 5G Mobile Terminal.

An eight-element multiple-input multiple-output (MIMO) frame antenna array in the 3.5 GHz band (3400–3600 MHz) for 5G mobile terminal systems was presented. By using the adjacent grounding and electromagnetic coupling feeding technology, the loop antenna element could generate two resonant frequencies, thus effectively expanding its bandwidth. By adopting double-sided parallel strip line (DSPSL) technology, the electromagnetic coupling inside the loop antenna could be adjusted, and the size of the loop antenna could be effectively reduced so that the MIMO antenna array could obtain a low-profile structure. The total size of the MIMO array was 150 mm × 75 mm × 5.3 mm. Without additional isolation measures, the measured −6 dB impedance bandwidth (BW) was 3400–3660 MHz, and the minimum isolation between antenna elements was better than −20 dB. The proposed antenna was expected to be applied to 5G mobile terminals based on its low-profile, high-isolated characteristics, and good MIMO performance.

A new dual‐band single‐ended‐to‐balanced filtering power divider

This article proposes a new dual-band single-ended-to-balanced (SETB) filtering power divider (FPD), which shows the excellent characteristics of wideband common-mode (CM) suppression and good selectivity. By employing the structure of double-sided parallel-strip line with a mid-inserted conductor and a T-shaped defected ground structure etched in the mid-inserted conductor, out-of-phase behavior and high CM suppression can be achieved successfully. Besides, to realize dual-wideband filtering performance and high selectivity, two pairs of step impedance stubs (SIS) loaded quarter-wavelength central line-terminal-shorted three parallel-coupled microstrip lines structure are adopted. Meanwhile, two pairs of resistors are introduced so as to realize excellent isolation. To verify effectiveness of the design method, a prototype of dual-band SETB FPD which operates at 3.2 and 4.9 GHz is designed, fabricated, and tested. Final results exhibit that the new dual-band SETB FPD possess high selective dual-band differential mode response, wideband CM suppression, and excellent isolation between the balanced output ports.

Wideband Balanced Bandpass Filter With Common-Mode Noise Absorption Using Double-Sided Parallel-Strip Line

In this letter, a wideband balanced bandpass filter (BPF) with the feature of common-mode (CM) noise absorption (CMNA) is presented. The whole circuit is realized with the double-sided parallel-strip line (DSPSL). The resistors placed at the two sides of the circuit work only when the CM signals are excited. The even/odd-mode equivalent circuits of the proposed BPF are analyzed and a systematic design method is introduced to guide the design. Finally, a practical BPF with CMNA is designed and fabricated. A good performance and the consistency between the simulation and the measured results verify the design theory.