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

Applied Electromagnetics and Electromagnetic Compatibility

A novel parallel-series feeding network for microstrip antenna arrays has been presented. A three-way power divider is utilized to connect the subarrays with the series-fed transmission lines. The proposed power divider is composed of seven transmission lines with different characteristic impedances and two isolation resistors. By changing the characteristic impedance of the transmission lines, the power division ratio can be adjusted. Meanwhile, good match and reasonable isolation performance can be obtained simultaneously. The proposed approach has been verified experimentally by using a 20-unit road side unit (RSU) antenna array operating at 5.815 GHz frequency range for a electronic toll collection (ETC) system. The proposed feeding network can be simply implemented on a single-layer substrate.

The mode-matching method is a useful technique for formulation of boundary-value problems, especially for structures consisting of two or more separate regions. It is based on matching the fields at the boundaries of different regions and hence lends itself naturally to the analysis of microwave boundary-value problems. The mode-matching method has widely been used for scattering and transmission problems, as well as transmission line analysis. Scattering problems include discontinuities in waveguides and transmission lines, such as the microstrip line and the coplanar waveguide (CPW), and obstacles in a medium. Transmission problems include analysis of filters, such as fin line bandpass filters, impedance transformers, and power dividers and transitions such as waveguide-to-microstrip line. Transmission line analyses include determination of the transmission line's propagation constant and characteristic impedance, such as those of a microstrip line, a CPW, and coplanar strips (CPSs). In this chapter, we describe the mode-matching method for analyzing planar transmission lines. Coplanar strips with finite strip metallization thickness are used to illustrate the formulation process. We also describe the mode-matching method for the analysis of planar transmission line discontinuities. A CPW is used to serve this purpose.

This work presents a Ka-band two-way 3 dB Wilkinson power divider using synthetic quasi-transverse electromagnetic (TEM) transmission lines (TLs). The synthetic quasi-TEM TL, also called complementary-conducting-strip TL (CCS TL), is theoretically analyzed. The equivalent TL model, whose production is based on the extracted results, is applied to the power divider design. The prototype is fabricated by the standard 0.18 mum 1P6M CMOS technology, showing the circuit size of 210.0 mumtimes390.0 mum without contact pads. The measurement results, which match the 50 Omega system, reveal perfect agreements with those of the simulations. The comparison reveals the following characteristics. The divider exhibits an equal power-split with the insertion losses (S21 and S31) of 3.65 dB. The return losses (S11, S22 and S33) of the prototype are higher than 10.0 dB from 30.0 to 40.0 GHz.

A Wilkinson power divider has ideal transmission characteristics and it enables easy realization in planar transmission line technology. However, the conventional Wilkinson power divider features a large component footprint because of its quarter-wavelength line components and narrow bandwidth. In this paper, two modified Wilkinson power divider are proposed in order to achieve size reduction and wide bandwidth. The first structure presents Wilkinson power divider using compact folded step impedance transmission lines (FSITL) rather than the uniform microstrip line design for operating center frequency of 3 GHz. While the second structure presents the FSITL with delta-stub for 2.4 GHz. The proposed folded microstrip line structure is capable of reducing the size of the power divider circuit. The impedance ratio of SITLs is taken into account as the total electrical length of the lines for every wavelength 0 1 and 0 2 in order to enhance size reduction to the optimum. The study managed to get an overall dimension of 15 mm × 9.5 mm for the first proposed design achieving a reduction of 75.6 % and bandwidth of 4 GHz. For the second proposed structure, the size was 15 mm × 15 mm with a reduction of 56 %. The proposed structures provided an extra 80 % fractional bandwidth based on the −15 dB return loss as a reference. The proposed power divider used RT/duroid 5880 substrate with 0.38 mm thickness. Simulation and measurement results indicated that the modified power divider showed equal power division, good phase balance, high isolation between output ports, and good return loss better than −15 dB covering the operating frequency range.

PurposeThis paper aims to establish the mathematical model and solve the complex calculation multi-field coupling problem for an electromagnetic overhead transmission line galloping excitation test system.Design/methodology/approachAn electromagnetic excitation test system is introduced. To calculate the vibration response of the transmission line, a transient coupled finite element model containing electromagnetic repulsive mechanism and transmission line system was established. Considering the advantages of Newmark-ß algorithm and fourth-order Runge–Kutta algorithm, the two algorithms are combined to solve the model. Compared with the simulation results of existing commercial finite element software, the accuracy of the calculation model of electromagnetic force and wire vibration response are verified.FindingsComparison results show that the proposed calculation model can accurately obtain the force of electromagnetic mechanism and the vibration response of the overhead power lines, and improve the calculation efficiency. The calculation results show that vibration under electromagnetic excitation presents a double half-wave mode, and the galloping amplitude varies according to the charging voltage.Originality/valueThis paper built the transient simulation model for a galloping test system. The Newmark-ß algorithm and the fourth-order Runge–Kutta algorithm are used to solve the model. The research results are of great significance for the actual galloping test system design.

In this paper, the spoof surface plasmon polaritons (SSPPs) transmission line (TL) of periodical grooved bow-tie cells is proposed. The complex propagation constant and characteristic impedance of the SSPPs TLs and microstrip lines (MLs) are extracted using the analytical method of generalized lossy TL theory. The properties of the SSPPs TLs with different substrates and the same geometrical configuration are experimented. Then, for comparison, two ML counterparts are also experimented, which shows that the SSPPs TL is less sensitive to the thickness, dielectric constant and loss tangent of the chosen substrate below the cutoff frequency, compared with the ML ones. The single-conductor co-planar quasi-symmetry unequal power divider based on this SSPPs TL is presented in microwave frequencies. For experimental validation, the 0-dB, 2-dB, and 5-dB power dividers are designed, fabricated, and measured. Both simulated and measured results verify that the unequal power divider is a flexible option, which offers massive advantages including single-conductor co-planar quasi-symmetry structures, wide-band operation, and convenient implementations of different power-dividing ratios. Hence, it can be expected that the proposed unequal power dividers will inspire further researches on SSPPs for future design of novel planar passive and active microwave components, circuits and systems.

This paper presents a two-dimensional transmission line (2-D TL) that supports quasi-TEM propagation mode and reduces problems associated with compacted meandering of microstrip (MS) on propagation constants and the characteristic impedances commonly observed in conventional one-dimensional MSs. The proposed 2-D TL comprises two layers of metallic surfaces on either side of a dielectric substrate. The top metal surface is a meandered connection of a unit cell with a central patch and connecting arms. The bottom surface is a meshed 2-D periodical ground plane, whose etched portion complements the patch portion of the top surface, forming a complementary-conducting-strip (CCS) TL, enabling a combination of an MS and MS with the tuning septa in a unit cell. Both theoretical and experimental investigations of the CCS TL agree well and demonstrate that it is much less susceptible to the effects of meanderings on the propagation constant and characteristic impedance than an MS for the same meandered pattern. Two design examples are presented to demonstrate the potential for a CCS TL for miniaturizing microwave passive circuits with minimal losses. The first example involves a 5.4-GHz CCS four-port rat-race hybrid realized in RO4003 and reduces the area of original MS design by 87%. The second example illustrates the applicability of a CCS TL to a monolithic RF integrated circuit using a first-pass design of a 5.2-GHz CMOS oscillator incorporating a CCS TL as a resonator with an area totaling 500/spl times/600 /spl mu/m/sup 2/ including pads base on Taiwan Semiconductor Manufacturing Company's 0.25-/spl mu/m 1P5M CMOS process techniques.

In this work, a defected microstrip structure (DMS), methods to calculate the new characteristic impedance of DMS line, and, as an application example, a design of microwave wilkinson power dividers using DMS pattern are described.DMS patterns are inserted for the desirable effects of periodic structure such as size-reduction and increased line width for high characteristic impedance.In order to calculate the proper characteristic impedance of DMS microstrip line, the quarter-wavelength transformer model method and an analytic calculation method are adopted.As an example, the DMS microstrip line with 70.7 characteristic impedance is designed, calculated and inserted into the wilkinson power divider.The size of designed power divider with DMS patterns is only 82% of a reference power divider composed of normal microstrip lines, while the circuit performances are very well preserved even after the size-reduction.

A novel Gysel power divider with uniform impedance transmission lines is presented. The arbitrary power-dividing ratio is obtained only by adjusting the electrical lengths of the transmission lines, avoiding the use of high impedance lines that are involved in the conventional Gysel power divider design with large power-dividing ratio. All the transmission lines are with the same characteristic impedance, which is independent of the power-dividing ratio and provides a freedom to control the operation bandwidth. For verification, a 9:1 Gysel power divider operating at 1 GHz is designed, fabricated, and measured. The measured results are in good agreement with the simulated ones. The measured results show a bandwidth of 13.7% with better than 20 dB return loss and 29.2 dB isolation from 0.95 to 1.09 GHz.

This article presents a broadband substrate integrated coaxial line (SICL) radial power divider with high output isolation. The proposed power divider mainly consists of input impedance matching circuits, microstrip isolation circuits, and radial SICL circuits. The two‐layer substrate of the input impedance matching circuit acts as a quasi‐coaxial structure and is connected to the coaxial input port to provide the function of impedance matching. The star‐type microstrip isolation circuits are employed to enhance the isolation performance between the output ports of the power divider. Two designed substrates sandwiching the air cavity layer constitute the radial SICL circuit, and the input microwave signal is evenly divided into 8 channels of signals with the same power. The designed power divider using SICL technology has the characteristics of supporting transverse electromagnetic mode transmission, being broadband, and compatible with substrate integration. A prototype of the multi‐layers eight‐way SICL power divider is designed, fabricated, and measured. The measured results show that the relative bandwidth of 15 dB input/output return loss is 34% and 43%, respectively. The absolute bandwidth of 15 dB input/output return loss is 5–7 GHz and 4.5–7.1 GHz, respectively, and the isolation between output ports is greater than 20 dB in the above frequency bands.

If it exists an ungrounded copper plane to be electrically isolated from a surrounding ground plane on the underside of a microstrip transmission line, this transmission line can operate as the microstrip line or the coplanar line according to open or short connection between the ungrounded copper plane and grounded plane on the base plane. Two different type operation of the transmission line means that one transmission line can have two different characteristic impedances. This paper proposes and fabricates the circuit to be operated 2-ports power transmission line or 2-way power divider with the stable input matching characteristic by using this dual-impedance transmission line. The proposed circuit operates 2-ports power transmission line in case of the coplanar line or 2-way power divider line in case of the microstrip line. The fabricated circuit shows S21 > -0.2 dB and S11 -3.8 dB, S11 < -10 dB and S21/S31 < ±0.3 dB above 700 MHz when the circuit operates 2-way power divider.

This paper designs a five-bit microelectromechanical system (MEMS) time delay consisting of a single-pole six-throw (SP6T) RF switch and a coplanar waveguide (CPW) microstrip line. The focus is on the switch upper electrode design, power divider design, transmission line corner compensation structure design, CPW loading U-shaped slit structure design, and system simulation. The switch adopts a triangular upper electrode structure to reduce the cantilever beam equivalent elastic coefficient and the closed contact area to achieve low drive voltage and high isolation. The SP6T RF MEMS switch uses a disc-type power divider to achieve consistent RF performance across the output ports. When designed by loading U-shaped slit on transmission lines and step-compensated tangents at corners, the system loss is reduced, and the delay amount is improved. In addition, the overall size of the device is 2.1 mm × 2.4 mm × 0.5 mm, simulation results show that the device has a delay amount of 0–60 ps in the frequency range of 26.5–40 GHz, the delay accuracy at the center frequency is better than 0.63 ps, the delay error in the whole frequency band is less than 22.2%, the maximum insertion loss is 3.69 dB, and the input–output return rejection is better than 21.54 dB.

The reciprocity theorem of antenna is introduced in this paper in researching the coupling between the spatial electromagnetic wave and transmission line on PCB; the complex calculation of the scattering field is avoided. The coupling voltage of the loads is studied in this paper with spatial EM wave incidence upon a transmission line on PCB.

A design method for unequal filtering power dividers (PDs) working at 2 bands is presented in this article. Compared with conventional unequal PDs, in this method, each section of the proposed circuit uses transmission lines whose characteristic impedances are controllable to avoid high‐impedance line. Meanwhile, the conventional λ/4 transmission line in PDs is substituted with a pair of proper dual‐mode resonators. To prove the effectiveness of the proposed design principle, a miniaturized unequal filtering PD working at 3.5 and 4.9 GHz is designed, fabricated and measured. Eventually, it is clear that the simulated results and the measurements have favorable agreement.