Coupled Line Structure Research Articles

Coupled line based unequal dual band power divider

ABSTRACTThis article presents theoretical design of dual band unequal power divider based on coupled line structure. The structure consists of two coupled line segments along with five transmission line segments used to satisfy unequal matching characteristic. The isolation is achieved using a circuit, which is a combination of inductor, capacitor, and resistor. Design equations of proposed power divider and the circuit providing isolation are based on circuit representation of ideal transmission lines. Simulation and measured results are given to verify the theoretical design equations. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:953–956, 2016

Compact NB BPF is using modified slow wave resonator with wide upper stopband

ABSTRACTA compact narrowband band pass filter (NB BPF) with wide stop‐band has been designed and fabricated. The presented filter based on modified slow wave resonator of microstrip is designed to achieve narrow bandwidth. The bandwidth of this filter capability of changing with the coupled lines is used in the middle of this structure filter. For the first time, by using transmission line theory and coupled line structure, the new design methodology of a narrowband BPF is employed and resonant frequency has been clearly explained. The filter has been designed for operating at center frequency 3.82 GHz, that suitable for WiMAX applications. The measured insertion loss (s21) and return loss (s11) are −0.38 dB and −33 dB, respectively at 3.82 GHz resonant frequencies. The proposed filter is designed, simulated and fabricated and the simulation results are in good agreement with measurement result. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:616–619, 2016

Wideband filtering power divider with high selectivity

A wideband filtering power divider (PD) with high selectivity is introduced, based on a terminated coupled line structure. The bandwidth tuning, isolation and impedance matching performances optimisation are presented and explained. Finally, the filtering PD is designed and implemented with a centre frequency (f 0) of 3.0 GHz and a fractional bandwidth of 70%. The upper stopband is achieved up to 2.6 f 0, with a rejection of better than 13 dB. The measured minimum in-band insertion loss is 0.3 dB (not including the splitting loss). Isolation of higher than 16.7 dB between the output ports is observed up to 2.7 f 0.

Balanced Dual-Band Bandpass Filter With Multiple Transmission Zeros Using Doubly Short-Ended Resonator Coupled Line

This paper presents a novel balanced dual-band bandpass filter with in-band common-mode suppression via multiple transmission zeros from the doubly short-ended coupled line. Through the analysis of coupled line structures, the transmission zeros in the differential- and common-mode equivalent circuits are extensively studied. In differential-mode, the transmission zeros, produced by both short-ended coupled line and open stub, are independently controlled, and the desired two resonant frequencies of the dual-band bandpass filter are achieved by studying the characteristics of the doubly short-ended half-wavelength resonator. For the common-mode suppression, the intrinsic transmission zeros of short-ended coupled line in differential-mode structure appear in the same frequency locations due to the proposed common-mode strcuture. With proper adjustment of the impedances and electrical lengths of the terminated stepped-impedance resonators (SIRs) on the symmetric plane, additional transmission zeros are introduced and relocated at the differential-mode resonant frequencies, thus producing good in-band common-mode signal attenuation as highly expected. As the attractive advantage of proposed balanced structure, the common-mode performance is independent of differential-mode one. To verify the proposed design method, a prototype balanced dual-band filter is theoretically analyzed, simulated, and experimentally measured, good agreements between simulated and measured results are obtained. The measured balanced dual-band bandpass filter is centered at 900 MHz and 2.49 GHz, and in-band common-mode rejection for first and second passbands are presented with higher than 30 and 40 dB, respectively.

Compact tunable bandpass filter with wide tuning range using ring resonator and short‐ended coupled lines

A tunable bandpass filter with wide tuning ranges for both the centre frequency and bandwidth is presented. The filter is based on using a ring resonator connected to a short-ended coupled-line structure. Two transmission zeros are generated in the upper stopband resulting in a sharp cutoff and harmonic suppression across a wide stopband. A thorough procedure is used to analyse the proposed filter. A prototype is fabricated and tested. The achieved results indicate a wide centre frequency and bandwidth tuning ranges of 0.52–1.42 GHz and 90–320 MHz, respectively.

In brief

PAGE 570 Based on split-ring resonators and source-load coupling, a compact dual-band bandpass filter has been presented, analysed and implemented by researchers in China. With low insertion loss and high return loss characteristics, the filter has very narrow 3 dB band widths at the two centre frequencies. PAGE 566 Researchers in the US have developed a method to predict the response of a metal-insulator-metal diode at terahertz frequencies from DC current-voltage measurements. Their method is the first where the current responsivity is determined as a function of both the frequency and the DC bias. Low return loss and high return loss are important for filter performance PAGE 548 Researchers in China have proposed a wideband filtering antenna with four resonant modes. Previous filtering antennas have been limited to two resonant modes and suffered from narrow bandwidth, and by fully incorporating all the coplanar structures into the same plane, the new design can be easily integrated with modern communication components. The terahertz response of MIM diodes can be determined from simple information PAGE 568 A tunable bandpass filter using a ring resonator and short-ended coupled-line structure has been presented by researchers in Australia. The proposed structure is more compact in size, and achieves a wider tuning range of centre frequency as well as bandwidth. The antenna's design means it can be integrated into existing technologies PAGE 553 A new power model for active-matrix organic light-emitting diode (AMOLED) displays has been presented by researchers in Korea. Their technique considers both the efficiency of an AMOLED DC-DC converter and the dependency of driving circuits and so gives rise to better accuracy. The filter is suitable for integration with reconfigurable software-defined transceivers Power-saving and power-management techniques for AMOLED displays is improved by considering efficiency and driving circuits

Novel Multi-way Broadband Differential Phase Shifter With Uniform Reference Line Using Coupled Line Structure

Conventional passive differential phase shifters (DPSs) usually require different reference lines to realize varied differential phase shifts, this results in both complex structure and bulky size for multi-way poly-phase applications. To resolve the problem, a DPS configuration with uniform reference line is proposed. It is constructed using basic coupled lines with simplicity in both design and fabrication procedures. The delay lines of the phase shifter have a similar structure and maintain desired constant phase shift compared with the uniform reference line over a wide bandwidth. To verify the proposed configuration, a four-way DPS which is comprised of 3 delay lines and a reference line, is designed, fabricated and measured. The delay lines provide the corresponding constant phase shifts (45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , 90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , 135 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> compared to the reference line. Over a bandwidth of 45%, excellent performance is achieved with small insertion loss and phase deviation.

A dual‐band branch line coupler based on Pi‐shaped coupled lines

ABSTRACTThis article presents a coupler using Pi‐shaped coupled lines for dual‐band operations. In this design, two open circuited stubs are tapped at both ends of a coupled line structure to realize the 90° phase changes at two frequencies. The designed structure is used in place of a conventional quarter wavelength transmission line for dual‐band application. For verification, a 3‐dB branch line coupler with operating frequencies of 0.95 and 1.52 GHz is designed. The simulated and measured results are in good agreement with each other. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:501–504, 2015

A Novel Harmonics-Suppression Coupled-Line Gysel Power Divider for Complex Terminated Impedances

A novel symmetrical coupled-line circuit structure is proposed to design a kind of harmonics-suppression coupled-line Gysel power divider that has the advantages of a compact structure and complex source to load-terminated impedances. It consists of four pairs of coupled lines, three pairs of transmission line stubs, and two grounded isolation resistors. Based on the traditional even- and odd-mode technique, closed-form mathematical equations for both circuit electrical parameters and scattering parameters are obtained. For demonstration purposes, two typical simulation examples with realized physical dimensions in microstrip technology are presented, indicating equal power division, good return loss, perfect isolation, and harmonics suppression on three different frequencies or wide operating frequency band. Finally, two practical microstrip coupled-line Gysel power dividers are designed and fabricated to operate at approximately 1 GHz. Good agreement between the simulated and measured results verify the design.

Analysis of Three-Conductor Coupled-Line 180&lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$^{\circ}$&lt;/tex&gt;&lt;/formula&gt; Hybrid for Single-Balanced Subharmonic Mixer Design in 0.15-&lt;formula formulatype="inline"&gt; &lt;tex Notation="TeX"&gt;$\mu{\hbox {m}}$&lt;/tex&gt;&lt;/formula&gt; pHEMT Technology

A novel 180 ° hybrid with two λ/4 sections of three-conductor coupled-line structure inhered different operating frequencies with overlapped characteristic and perfect isolation between the Σ-port and Δ-port is employed to implement a Ka- to M-band single-balanced subharmonic mixer (SHM) in a 0.15- μm GaAs pHEMT process with a compact die size of less than 0.82 × 0.83 mm 2 . The thorough analysis based on the scattering matrix of the 180 ° hybrid is also presented. Incorporating the inherent features of the 180 ° hybrid with an antiparallel diode pair configuration, the proposed SHM achieved a wide operating bandwidth from 37 to 85 GHz with low conversion loss from 9 to 14 dB, enhanced local oscillation (LO)-to-RF isolation and 2LO-to-RF isolation under 10-dBm LO power level. This proposed architecture is really attractive to SHM design in modern millimeter-wave territory.

Design of cascaded three‐conductor coupled line filter

ABSTRACTThis article presents analysis approach and applications of symmetrical three‐conductor coupled microstriplines with aperture in the ground plane for the design of microwave filters. Analysis is based on splitting the entire symmetrical three‐conductor coupled line structure into simple two‐conductor coupled lines. Various possible terminations have been shown in three‐conductor coupled lines to derive a class of structures for the construction of filters. These coupled line structures are analyzed based on even‐ and odd‐mode propagation characteristics to design filters in this article. An experimental cascaded three‐conductor coupled line band stop filter with defected ground has been designed using the method of circuit model analysis. Defected ground has been used under the coupled lines to widen the filter's bandwidth. Measured results of the designed band stop filter have been compared against the circuit model analysis for the purpose of validation. Results are in good agreement between them. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2431–2436, 2014

Differential broadband filter based on microstrip coupled line structures

A coupled line schematic is proposed to build the differential filter featuring broadband, low insertion loss and good common-mode suppression. The proposed filter is composed of four quarter-wavelength coupled lines and four quarter-wavelength microstrip lines. The calculated, simulated and measured results are in good agreement with each other. The differential-mode signal can propagate with low insertion loss, whereas the common-mode signal will be suppressed below −10 dB. The fractional bandwidth of the proposed filter is 82% centred at 3 GHz.

A novel high-power dual-band coupled-line Gysel power divider with impedance-transforming functions.

A novel coupled-line structure is proposed to design dual-band and high-power Gysel power dividers with inherent impedance-transforming functions. Based on traditional even- and odd-mode technique, the analytical design methods in closed-form formula are obtained and the accurate electrical parameters analysis is presented. Due to the usage of coupled-line sections, more design-parameter freedom and a wider frequency-ratio operation range for this kind of dual-band Gysel powder divider are obtained. Several numerical examples are designed and calculated to demonstrate flexible dual-band applications with different impedance-transforming functions. A practical microstrip power divider operating at 2 GHz and 3.2 GHz is designed, fabricated, and measured. The good agreement between the calculated and measured results verifies our proposed circuit structure and analytical design approach.

A Novel Coupled-Line Gysel Power Divider for Dual-Band and High-Power applications&lt;sup&gt;&lt;/sup&gt;

A novel coupled-line structure is proposed to design dual-band and high-power Gysel power dividers. Based on traditional even-and odd-mode technique, the analytical design theory is given and the electrical parameters analysis is provided. Four numerical examples are presented to demonstrate the flexible dual-band applications. A practical power divider operating at 1GHz and 2 GHz is designed. The calculated and full-wave simulated results verify our proposed idea.

Miniaturized branch-line hybrid coupler with broadband impedance matching network

This paper presents a compact broadband branch-line hybrid coupler. It is composed of a miniaturized branch-line hybrid coupler and broadband impedance matching networks. A coupled-line structure is used for the broadband impedance matching network. The branch-line hybrid coupler is realized by using high-impedance transmission lines and distributed capacitors. In order to further reduce the circuit size, the distributed capacitors are placed in the center space of the hybrid coupler and the coupled lines are effectively meandered. For validation, a prototype of the compact hybrid coupler was designed and fabricated at the center frequency of 1 GHz. For given conditions, the proposed hybrid has 29.4% bandwidth which is from 870 to 1170 MHz. Compared to the conventional 3-dB branch-line hybrid coupler, it exhibited a size reduction of 50.8% and an extended operating bandwidth of 66.7%.

A Compact Microstrip Wideband Arbitrary Branch-Line Coupler with Coupled-Line Impedance-Transforming Structures

Abstrct A novel coupled-line impedance-transforming structure with two parallel short-circuit stubs is proposed to design a wideband branch-line coupler with arbitrary power division in this article. In order to design this modified wideband branch-line coupler, analytical synthesis equations are obtained. As typical examples, four wideband branch-line couplers with different power dividing ratios are presented. The widest 20-dB return loss and isolation fractional bandwidth in these four numerical examples is almost 38%. Finally, two microstrip branch-line couplers operating at 1 GHz are fabricated and measured. One of these couplers has equal power division and a measured 13.9-dB return loss and isolation fractional bandwidth of 32.8%. The other one has 3-dB unequal power division and a measured 12.7-dB return loss and isolation fractional bandwidth of 37.6%. Obviously, this proposed branch-line coupler has several advantages, including a wide band, a compact size, an unequal power division, easy implementation (simple structure), and an analytical design method.

A COMPACT MICROSTRIP QUADRUPLEXER USING SLOTLINE STEPPED IMPEDANCE STUB LOADED RESONATORS

In this paper, a novel compact quadruplexer is imple- mented by using slotline stepped impedance stub loaded resonators (SISLRs) in ground plane. Four folded dual-mode slotline SISLRs with one input and four output coupled line structures are designed at difier- ent frequencies for the quadruplexer operation. By properly adjusting the geometrical parameters of a single dual-mode slotline SISLR, its flrst two resonant frequencies can be controlled, and thus it can be uti- lized to implement a second-order bandpass fllter when these resonant frequencies are suitably assigned. Furthermore, because the proposed quadruplexer utilizes the distributed coupling technique, a small circuit size can be obtained. As a result, the proposed quadruplexer occupies an extremely small area, i.e., 0:22‚0£0:25‚0 (0:36‚g£0:41‚g). Finally, good agreement between measurement and EM simulation verifles the design method successfully.

NEW NEGATIVE COUPLING STRUCTURE FOR SUBSTRATE-INTEGRATED CAVITY RESONATORS AND ITS APPLICATION TO DESIGN OF AN ELLIPTIC RESPONSE FILTER

This paper presents a new type of a negative coupling structure for designing elliptic-response fllters with cross-coupling. The proposed coupling structure consists of short-circuited coupled transmission lines. Using the fact that insertion phase of the coupled line structure is difierent from that of an inductive iris, it is shown that the proposed coupling structure can be used as the negative coupling structure. In order to verify the proposed coupling structure, we designed a 4th-order cross-coupled elliptic-response bandpass fllter with substrate integrated waveguide resonators. A pair of transmission zeros in measurement and simulation results validates that the proposed structure can be used as the negative coupling structure.

NOVEL IN-LINE MICROSTRIP COUPLED-LINE BANDSTOP FILTER WITH SHARP SKIRT SELECTIVITY

This paper presents a novel design approach to design in- line microstrip bandstop fllter with accurate design theory and sharp skirt selectivity. This kind of bandstop fllter is based on a simple coupled-line structure, indicating compact and ∞exible circuit layout for microstrip implementation. For a single-section bandstop fllter, the scattering parameters and their constrain conditions are achieved, which provides an efiective design guide for multi-section bandstop fllters. Theoretical analysis indicates that the even-mode and odd- mode characteristic impedances can be easily used to determine the desired bandstop performance while the total circuit layout keeps very compact. For demonstration, seven numerical examples are designed, calculated, and compared. Finally, both experimental and simulation results of a two-section two-cell microstrip bandstop fllter operating at 1GHz are presented to verify the theoretical predications.

Design of Transmission-Type $N$th-Order Differentiators in Planar Microwave Technology

In this paper, we propose and demonstrate a new technique for the design of arbitrary-order differentiators, intended for ultra-wideband (UWB) applications in microwave coupled-line technology. The technique employs an exact analytical series solution for the synthesis problem derived by the authors from the coupled-mode theory. This solution allows for the synthesis of microwave devices with arbitrary frequency responses, only limited by the principles of causality, passivity, and stability. The method has been successfully applied in the past to the design of two-port waveguide and transmission-line components operating in a reflection-type configuration. Here, the synthesis technique is extended to coupled-line structures, where the input port is matched at all frequencies and the reflected signal is redirected to the coupled port, enabling an effective transmission-type operation for the device. First-, second-, third-, and fourth-order UWB differentiators have been successfully designed, fabricated, and measured, validating the general design technique proposed.