Transmission Line Filters Research Articles

Transmission-Line Schematic for Harmonic-Controlled Bandpass Filters

This article presents a rigorous synthesis method of a transmission-line filter whose second passband can be placed at any multiple of the center frequency, in theory. Two coupled-line schematics for harmonic-controlled bandpass filters are derived from fundamental <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> filter prototypes. Their design parameters are provided in closed-form expressions so filter dimensions can be acquired rigorously without relying on EM-simulation-based coupling tests. Three filters were designed and fabricated for verification purposes, and their measurement results exhibited excellent agreement with the theory.

Transmission-Line Bandpass Filter Structures With Infinite Reflectionless Range

This article is to present a complete method to design transmission-line reflectionless filters. Our approach can be used to accord a transmission-line filter to feature an infinite frequency range of reflectionless response. It can be applied to reflectionless filter prototypes consisting of filtering and matching sections that comply the Cauer topology. Hence, it does not limit by the filter order and/or the filter response type. Design equations supporting our approach are provided, and their applications to actual filter designs will be elaborated via various filter examples with distinct features. The measurements authenticate our design approach.

Estimation of Ferroelectric Material Properties and Phase-Shifter Design Key Parameters Influence on Its Figure of Merit for Optimization of Development Process

A model of the estimation of the ferroelectric-based phase-shifter figure of merit concerning the material properties and phase-shifter design parameters is presented. The influence of ferroelectric material tunability and losses on phase-shifter characteristics are analyzed. Two approaches to phase-shifter design (transmission line and band-pass filter) are considered. The review of the published results on the ferroelectric phase-shifter design was performed to approve the method proposed. Recommendations to optimize the phase-shifter development process are suggested on the basis of the elaborated model and analysis performed.

A new carbon nanotube-based filter for quantum computing applications

A new article introduces a compact, high-performance lossy transmission line filter based on carbon nanotubes that successfully improves coherence times of a superconducting qubit.

Carbon nanotube-based lossy transmission line filter for superconducting qubit measurements

In superconducting qubit measurements, stray infrared photons lead to damping processes that degrade quantum coherence. In this Letter, we show that a thermal blocking filter made of multiwalled carbon nanotubes diluted in stainless steel powder can significantly improve the energy relaxation time, T1, and the pure dephasing time, Tφ, of a qubit. By using two independent measurement lines, with and without the filter, and switching between them in situ, we observe that with the filter there is an increase of more than 61% in T1 and 291% in Tφ. We characterize the filter, demonstrating that the scattering parameters remain stable down to 8 mK over a wide range of frequencies, spanning from 10 MHz to 50 GHz. We also show that the cutoff frequency of the filter is easily controlled by selecting the concentration of nanotubes.

Design of broadband high‐efficient PA based on hybrid continuous modes

An ultra-wide band high-efficient power amplifier (PA) which employs both series of continuous modes and series of inverse continuous modes is presented for the first time. Consequently, the solutions space of fundamental impedance is expanded greatly. The operation frequency range of this mode can achieve more than two-octave bandwidth. Multistage transmission-line low-pass filter matching network has been utilised for matching fundamental impedance and suppressing of high-order harmonic. To verify this method, a high-efficient PA, which operates across 0.3–2.7 GHz (160% bandwidth) is designed. Simulation and experimental results show that the drain efficiency of this PA achieves 61.4–81.9%, and 8.3–16.6 W output power in the target band.

Holistic design strategy for high‐selectivity low‐loss integrated millimetre‐wave image‐reject filters

To alleviate practical limitations in the design of millimetre-wave on-chip image-reject filters, systematic design methodologies are presented. Three low-order filters with high-selectivity and low-loss characteristics are designed and compared. Transmission zeroes are created by means of a quarter-wave transmission line (filter 1) and a series LC resonator (filters 2 and 3). Implemented on silicon germanium, the filters occupy 0.125, 0.064 and 0.079 mm2 chip area including pads. The measured transmission losses across 81–86 GHz E-band frequency range are 3.6–5.2 dB for filter 1, 3.1–4.7 dB for filter 2 and 3.6–5 dB for filter 3 where rejection levels at the image band are >30 dB.

The MTT-S Historical Collection [MTT World

The at the 2014 International Microwave Symposium (IMS2014) in Tampa, Florida, USA, marked the 35th anniversary of the IEEE Microwave Theory and Techniques Society (MTT-S) Historical Collection. The collection was started and first displayed at IMS1980 in Washington, D.C. According to a report by Ted Saad: At the 15 January 1980 MTT-S Administrative Committee (AdCom) meeting in Washington, D.C., Dr. Steve Adam, the then AdCom president, gave me the task of preparing a historical exhibit for the 1980 MTT-S Symposium to be held in Washington on 28–30 May 1980. No specifications or instructions were given. The was an outgrowth of a suggestion on the part of Dr. John Horton, who for several years had proposed some type of microwave hall of fame. The collection has grown steadily over the years and now consists of more than 1000 cataloged items. At the end of 2014, there were 522 pieces of hardware, 328 books, 196 miscellaneous documents, and 14 videos. The hardware artifacts comprise; 353 tubes, including gridded types, klystrons, magnetrons and other crossed-field types, radar transmit‐ receive (T/R) tubes, and tube components; 76 subassemblies or modules, including amplifiers, oscillators, and various test equipment; 56 transmission line items, including couplers, slotted lines, variable attenuators, phase shifters, and filters; 37 individual solid-state components. Some of the artifacts are one-of-akind experimental pieces like the copper- foil-lined wooden block that was used as a waveguide coupler. Many are samples of mass quantities taken from the production line. The oldest truly microwave items are two 1932 splitanode magnetrons from Ross Kilgore of Westinghouse. The newest is a 1996 Litton mini traveling-wave tube (TWT). The books include engineering texts such as a complete 28-volume set of the MIT Radiation Laboratory (Rad Lab) series, biographies of various individuals, company histories, and manufacturers' catalogs.

Reflectionless Filter Structures

This paper expands on the previously described reflectionless filters - that is, filters having, in principle, identically-zero reflection coefficient at all frequencies - by introducing a wide variety of new reflectionless structures that were not part of the original publication. In addition to extending the lumped-element derivation to include transmission line filters, this is achieved by the introduction of a novel method wherein the left- and right-hand side stop-band terminations are coupled to each other using a two-port sub-network. Specific examples of the sub-network are given which increase the stop-band attenuation per filter cell and steepen the cutoff response without disrupting the reflectionless property or increasing the insertion-loss in the pass-band. It is noteworthy that a common feature of all the structures derived by these methods is that most, if not all, of the reactive elements are of equal normalized value. This greatly simplifies the tuning requirements, and has facilitated their implementation as monolithic microwave integrated circuits (MMICs). A number of examples of MMIC reflectionless filters constructed in this way are presented and their results compared to the theory.

Using Via Stubs in Periodic Structures for Microwave Filter Design

This paper presents a novel form of microwave filter construction using vias (plated through holes) available in generic printed circuit boards as the main building block. It is demonstrated that for a certain arrangement of vias, the resonant behavior of via stubs can be used to create a low- or a high-pass filter using open- or short-circuited vias, respectively. These stubs are periodically cascaded, resembling an analogous implementation using transmission-line stub filters. It will be shown that such a via filter structure can achieve insertion loss lower than 0.1 dB and return loss of about -60 dB in the passband at GHz frequencies. Measurements, full-wave, and physics-based simulations are presented to verify this novel filter concept and to provide design guidelines in the frequency range from 1 to 20 GHz.

Design of Artificial Transmission Line and Low-Pass Filter Based on Aperiodic Stubs on a Microstrip Line

Among many microstrip configurations, the open-circuited shunt stub is probably the most common and versatile one. It is capable of performing a wide range of functions. Despite extensive studies and applications of the open-circuited shunt stub, comparatively little is known about aperiodic stubs on a microstrip line. In this paper, aperiodic stubs on a microstrip line are exploited to implement a high-performance low-pass filter and a joint design of the artificial transmission line and low-pass filter. The experimental results validate the performance of the proposed circuits. For the low-pass filter application, the proposed circuit outperforms a seventh-order Butterworth filter while their circuit sizes are comparable. For the joint design, it may potentially enhance the degree of integration in RF and microwave systems.

Impedance matched absorptive thermal blocking filters

We have designed, fabricated, and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match 50 Ω and its response has been validated from 0 to 50 GHz. The observed return loss in the 0 to 20 GHz design band is greater than 20 dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.

A Balanced Digital Phase Shifter by a Novel Switching-Mode Topology

A balanced digital phase shifter by a novel switching-mode topology is proposed. A 3-bit balanced digital phase shifter is given as an example, the working bandwidth of which is from 2.3 to 2.7 GHz. The proposed 3-bit balanced phase shifter comprises two balanced loaded-line phase shifters (90° and 45°) and six twist-line broadband 180° phase shifters. The balanced loaded-line digital phase shifter changes phases while the even- or odd-mode signal is excited. The 180° phase shifter controls the balanced signal to be even or odd mode. The commensurate transmission line filter is used as the biasing circuit.

Transmission Line Filters with Harmonic Parallel Foster Sections

Conventional wideband bandstop filters use Cauer prototypes, but become nonrealizable with Kuroda–Levy transforms for bandwidths of 150% or more. Transmission line filters with harmonic stubs have been shown to be realizable at these bandwidths, but have limited performance ranges due to the fixed positions of the transmission zeros. In this article, two structures that use shunt Foster resonators that enable the shift of the transmission zeros are described. Simulated and measured properties show that greatly improved performance can be realized while not adding to the complexity of the structure. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1724–1728, 2013

Microstrip filters for measurement and control of superconducting qubits

Careful filtering is necessary for observations of quantum phenomena in superconducting circuits at low temperatures. Measurements of coherence between quantum states require extensive filtering to protect against noise coupled from room temperature electronics. We demonstrate distributed transmission line filters which cut off exponentially at GHz frequencies and can be anchored at the base temperature of a dilution refrigerator. The compact design makes them suitable to filter many different bias lines in the same setup, necessary for the control and measurement of superconducting qubits.

High efficiency GaN current‐mode class‐D amplifier at 2.6 GHz using pure differential transmission line filters

In class-D operation the impedances of the output network at each harmonic frequency at the intrinsic terminals of the transistors are of main importance. This reported work demonstrates a new concept using pure differential transmission line filters for the matching of these impedances. Furthermore, de-embedding techniques are used to compensate the impedance transforming characteristics of the package parasitics. A current-mode class-D (CMCD) amplifier with a power-added efficiency (PAE) of 62% and a corresponding output power of 29.5 W at 2.6 GHz has been demonstrated. To the authors' knowledge, these are the highest reported values of the PAE as well as the output power at this frequency for a CMCD.

Slow-wave slot microstrip transmission line and bandpass filter for compact millimetre-wave integrated circuits on bulk complementary metal oxide semiconductor

In this study, a novel on-chip low-loss slow-wave slot (SWS) microstrip transmission line is proposed. Unlike conventional slow-wave structures such as photonic bandgap and ladder microstrip transmission line, which usually deal with either the substrate, ground plane or the signal line separately, the periodic patterns of SWS structures are etched along both the conductive metal strip and the ground plane of the microstrip line. The proposed structure, unlike other slow-wave structures does not require extra drilling through the substrate or complex three-dimensional multi-layer structures, only requires coplanar slot etching. The proposed SWS microstrip demonstrates excellent size reduction with minimal increase in loss. To show the utility of the proposed method, two second-order rectangular open-loop filters with and without implementing the proposed SWS microstrip have been designed with similar bandwidths and fabricated in the millimetre-wave (mm-wave) range on 65-nm bulk complementary metal oxide semiconductor (CMOS). Both simulations and measurements demonstrate that the on-chip filter implemented using the proposed SWS has a 52.7% reduction in size while suffering only an additional 0.5 dB in transmission loss penalty. To the best of authors’ knowledge, this compact filter is the first reported mm-wave filter using slow-wave structure on bulk CMOS.

Application of Stepped-Impedance Technique for Bandwidth Control of Dual-Band Filters

This paper demonstrates application of the popular stepped-impedance technique to control the bandwidths of dual-band filters independently. Unlike previous dual-band stepped-impedance filters, the role of the stepped-impedance technique is to control the bandwidths of the two bands rather than to provide dual-band performance. The exact relationship between stepped-impedance ratios and the ratio of the two absolute bandwidths is obtained through rigorous analysis. Moreover, since the proposed filters can be synthesized with popular transmission lines and coupled lines that are very-well characterized, time-consuming full-wave simulation can be minimized. Along with the complete set of design equations, experimental results for transmission-line and coupled-line dual-band filters are provided that verify the proposed approach.

Web-Based Virtual Laboratories for Antenna Arrays, Radiowave Propagation, and Filter Design

This tutorial explains in detail the creation of a Web-based application using the MATLAB Web Server (MWS) toolbox of MATLAB. It aims to enable readers who are familiar with MATLAB but don't have Web-programming skills to prepare their own Web-based applications. Three Web-based virtual laboratories, AntenGUI, SSPEGUI, and FilterGUI, created using MWS, are presented. The AntenGUI application illustrates the array factor of linear, rectangular, and circular arrays. The SSPEGUI application visualizes radiowave propagation over a non-smooth Earth's surface through a non-homogenous atmosphere. The FilterGUI tool designs lumped-element (LC) filters, and obtains the corresponding transmission-line and microstrip-line filters. These Web-based virtual tools can be accessed on the Internet.

Wideband bandstop filter with sub-harmonic stubs

The performance of a wideband bandstop transmission line filter employing a series overlay inductor over two stubs resonating at, respectively, one half and one quarter of the centre frequency is described. The structure contributes seven transmission zeros to the stopband and the performance compares to that of a Cauer filter. The structure has the advantage of having impedance levels that are readily realisable.