Low-loss Transmission Lines Research Articles

Two CMOS Wilkinson Power Dividers Using High Slow-Wave and Low-Loss Transmission Lines.

This work presents two Wilkinson power dividers (WPDs) using multi-layer pseudo coplanar waveguide (PCPW) structures. The PCPW-based WPDs were designed, implemented, and verified in a standard 180 nm CMOS process. The proposed PCPW features high slow-wave and low-loss performances compared to other common transmission lines. The two WPDs are based on the same PCPW structure parameters in terms of line width, spacing, and used metal layers. One WPD was realized in a straight PCPW-based layout, and the other WPD was realized in a meandered PCPW-based layout. Both the two WPDs worked up to V-band frequencies, as expected, which also demonstrates that the PCPW guiding structure is less susceptible to the effects of meanderings on the propagation constant and characteristic impedance. The meandered design shows that the measured insertion losses were about 5.1 dB, and its return losses were better than 17.5 dB at 60 GHz. In addition, its isolation, amplitude imbalance, and phase imbalance were 18.5 dB, 0.03 dB, and 0.4°, respectively. The core area was merely 0.2 mm × 0.23 mm, or 1.8 × 10-3λo2.

Two coupled resonant-tunneling-diode oscillators with an air-bridged transmission line for high-power coherent terahertz radiation

We developed a two-coupled resonant-tunneling-diode (RTD) terahertz (THz) oscillator with a high output power to fill the THz gap. We arranged two RTD mesas in a low-loss air-bridged transmission line for strong mutual coupling and generation of a unique operation mode and integrated a planar ring-slot antenna for efficient THz radiation while satisfying the impedance matching condition. The device structure was fabricated using a multilayer resist process and a carefully controlled wet etching process. The fabricated device exhibited coherent operation and a high output power of approximately 0.24 mW at a high frequency of 925 GHz.

Circularly Polarized Leaky-Wave Antenna Based on Low-Loss Transmission Line

A leaky-wave antenna with circular polarization property is proposed in millimeter-wave band, which can be applied in the wireless communication systems and remote sensing. The radiation is produced by the periodic patches on both sides of the dielectric slab of the antenna based on a low-loss planar Goubau line structure. The circular polarization unit cell of this antenna is made of two pairs of H-shaped patches, orthogonally set on each side of the dielectric substrate, which can efficiently reduce the cross polarization. This antenna is excited by a central strip line on the upper surface of the slab, removing the ground of the traditional microstrip structure, to reduce the loss of the antenna. The circular polarization property is achieved by optimizing the size and the distribution of the radiation unit cell and the structural periodicity. The radiation performance of this antenna is analyzed by CST simulation, which shows that the overlapping bandwidth of this antenna for 3 dB axial ratio with S11 < −10 dB is about 5.3%, with cross polarization 23 dB lower than copolarization. The simulated maximum directivity is l5.5 dBi with efficiency over 90% during the whole band.

Progress in ITER ECE diagnostic design and integration

The ITER electron cyclotron emission (ECE) diagnostic system has primary roles in providing measurements of the core electron temperature profile and the electron temperature fluctuation associated with the neoclassical tearing modes. The ITER ECE system includes a radial and oblique line-of-sight. Four 43-meter long low-loss transmission lines (TLs) are designed to transmit millimeter wave power in the frequency range of 70–1000 GHz in both X- and O-mode polarization from the port plug to the ECE instrumentation room in the diagnostic building. The measurement instrumentation includes two Fourier transform spectrometer (FTS) systems and two radiometer systems. The Indian Domestic Agency (IN-DA) and United States Domestic Agency share the responsibility. The IN-DA scope excluding instrumentation and control has passed its preliminary design review and is progressing towards the final design review (FDR). In parallel, the diagnostic integration in different areas is ongoing. Several captive components for the TLs have passed FDR and will be manufactured for installation in the tokamak building soon. A peer review meeting has been held on the prototype hot calibration source, and its integration and new thermal analysis in the diagnostic shield module are continuing. A prototype TL is being tested. A prototype polarizing Martin-Puplett type FTS, operating in the frequency range 70–1000 GHz, features an in-vacuo fast scanning mechanism and a cryo-cooled dual-channel THz detector system. Its performance has been assessed in detail against ITER requirements.

A Novel Method to Broaden the Single-Mode Bandwidth of the Rectangular Waveguide

In this paper, a new class of broadband and low-loss transmission line called slotted rectangular waveguide (SRW) is proposed and analyzed. The proposed SRW consists of the rectangular waveguide and the inverted low-loss slotline, which can selectively suppress the higher-order mode (TE20 mode) and broaden the single dominant mode (TE10 mode) bandwidth in a rectangular waveguide (RW). The design principle and transmission characteristics of the SRW are illustrated and analyzed in this work. The transmission dominant mode bandwidth of the proposed SRW is analyzed and compared with the classic rectangular waveguide (RW), in which the dominant mode bandwidth of 60–155 GHz (88.4% bandwidth) is broader than the RW bandwidth of 60–116 GHz (63%). Two feed structures that can excite the two operating bandwidths (W and D band) of them separately are also designed. The SRW and transition exhibit broadband and low-loss characteristics from 75 GHz to 155 GHz, in which the transmission loss is lower than 0.68 dB and the return loss is over 18 dB.

Design of Terahertz Low-Loss Transmission Line and Band-Stop Filter Based on Spoof Surface Plasmon Polaritons

Design of Terahertz Low-Loss Transmission Line and Band-Stop Filter Based on Spoof Surface Plasmon Polaritons

50 Ω transmission lines with extreme wavelength compression based on superconducting nanowires on high-permittivity substrates

We demonstrate impedance-matched low-loss transmission lines with a signal wavelength more than 150 times smaller than the free space wavelength using superconducting nanowires on high permittivity substrates. A niobium nitride thin film is patterned in a coplanar waveguide (CPW) transmission line geometry on a bilayer substrate consisting of 100 nm of epitaxial strontium titanate on high-resistivity silicon. The use of strontium titanate on silicon enables wafer-scale fabrication and maximizes process compatibility. It also makes it possible to realize a 50 Ω characteristic impedance across a wide range of CPW widths from the nanoscale to the macroscale. We fabricated and characterized an approximately 50 Ω CPW device with two half-wave stub resonators. Comparing the measured transmission coefficient to numerical simulations, we determine that the strontium titanate film has a dielectric constant of 1.1×103 and a loss tangent of not more than 0.009. To facilitate the design of distributed microwave devices based on this type of material system, we describe an analytical model of the CPW properties that gives good agreement with both measurements and simulations.

Low-Loss Gap Waveguide Transmission Line and Transitions at 220–320 GHz Using Dry Film Micromachining

This article presents a novel microfabrication technique to manufacture gap waveguide (GW) components operating at submillimeter-wave (sub-mmWave) frequency range. The conventional metal waveguide component manufacturing has a low resolution and low throughput and is not suitable for applications above 100 GHz. The micromachining techniques have matured and applied in various applications. Several micromachining techniques have been developed to address the specification requirements of different fields. Conventional micromachining techniques suffer from fabrication issues, such as nonvertical sidewall, nonuniform surface, and time-consuming fabrication process. The proposed dry film photoresist offers a significant amount of benefits, such as fewer processing steps, reduced production cost, and shorter prototyping time over existing micromachine techniques. To validate the proposed fabrication method, SUEX dry film photoresist is used to demonstrate three GW transmission lines. Different transitions from rectangular waveguide (RW) to GW have also been designed to characterize the newly fabricated GW components with a standard measurement setup. All the designed and fabricated devices operate from 220 to 320 GHz. The fabricated devices showed a good agreement with the simulation result over this frequency band and the measured average insertion losses were in the order of 0.048 and 0.075 dB/mm for groove GW and ridge GW, respectively. Thus, dry film photoresist provides fabrication precision of the structures and consequently opens the path for low-cost fabrication of high-frequency waveguide components.

Silver-seed Plating Technique for fabricating Low-Loss Transmission Lines

Silver-seed Plating Technique for fabricating Low-Loss Transmission Lines

A Compact, High-Efficiency, Reflectionless Leaky-Wave Antenna

A compact, high-efficiency leaky-wave antenna (LWA) is presented in this letter. Comprised by a novel periodic transmission line structure, the developed LWA could radiate its input power by a peak radiation efficiency of 93% with a compact size of 3.63λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> × 0.24λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> . Besides, the LWA exhibits good reflectionless performance characteristics from dc to 19 GHz. The equivalent circuit representations are utilized to reveal its operation mechanism. It is verified that the LWA operates as a slotted half-mode substrate integrated waveguide with high-efficiency leaky-wave radiation in the upper leaky band. Meanwhile, it could serve as a low-loss slow-wave transmission (SW-TL) line with spoof surface plasmon polariton structure in the lower band. For verification, an LWA prototype was fabricated and measured, which has experimentally confirmed its simulated radiation performances.

Dual-band substrate integrate waveguide slot antenna for 5G applications

The current fifth generation (5G) and millimeterwave technologies are urgently needed to provide huge bandwidth, dual-bands, multi bands, high gain and high directivity radiation pattern beams antennas. However, antennas at millimeterwave suffer from radiation loss and component loss with narrow bandwidth, especially when it is implemented using microstrip structures. Different transmission lines such as waveguide and substrate integrated waveguide (SIW) are studied and introduced for realizing antennas at millimeterwave bands. SIW structures are good candidate for implementation of antenna due to its property of low loss transmission line comprises the properties of microstrip and waveguide technology. However, SIW antennas and structures at millimeterwave have unwanted radiation losses comes from the vias holes. In addition, the vias separation distance is depended on waveguide size, which leads to a bigger size for massive antenna array network at proposed 26 GHz and 28 GHz. Hence, this paper proposed a dual band, compact size, and optimal SIW antenna structure to reduce the vias losses and provides higher bandwidth and gain at 26 GHz and 28 GHz. The proposed design is implemented using three slots to achieve the dual band property and increases the return loss. The proposed design is simulated and studied using CST software. The outcomes of dual-band response at 26 GHz and 28 GHz with a return loss more than 10 dB and a fractional bandwidth of 15% are achieved. A good gain around 8 dB is achieved. These results give a promising solution for realizing a full antenna array based on SIW technology at millimeterwave and 5G technology.

Application of Low-Loss Transmission Lines with an EHF Radiometer in Gas-Dynamic Experiments

The possibility of using oversized rectangular metal waveguides as elements of the transmission line of an EHF radiometer, which is designed to study fast gas-dynamic processes, is analyzed. The results of a numerical simulation and experimental research of a flexible waveguide for coupling metal waveguides of standard and oversized cross sections, which is constructed on the basis of a dielectric waveguide, are presented. A quantitative estimation of the signal attenuation in the transmission line, which is a combination of a flexible waveguide and an oversized metal waveguide, is performed.

Ku 대역 저손실 소형 4×4 버틀러 매트릭스의 구현

The Ku-band (12~18 GHz) is mainly used for long-range satellite communications and radar applications. Because the signal power is weak in a long-range communication, it is important to reduce the loss of the transmitter and receiver. In this paper, we propose a low-loss compact 4×4 Butler matrix structure that operates in the range of 15.7~16.7 GHz. To achieve low-loss characteristics, a low-loss transmission line was designed based on the suspended transmission line. To miniaturize the structure, the internal circuit of the Butler matrix was designed as a 100 Ω system, and the input/output stage was matched at 50 Ω. The size of the Butler matrix circuit manufactured through the optimized design was 45×22×2.3 mm. The insertion loss, isolation between terminals, and return loss of each terminal measured within the operating frequency band were 1.36 dB (including connector loss), 20.5 dB, and 15.3 dB, respectively, demonstrating a performance similar to that of the simulated performance. The proposed 4×4 Butler matrix can be utilized as a low-loss beam-switching circuit for a 1×4 linear array antenna.

Preliminary design overview and performance assessment of the ITER low-field side reflectometer

The design of the ITER low-field side reflectometer (LFSR) has matured to a complete end-to-end preliminary design. LFSR will supply three important plasma measurements: (1) electron density profile, (2) electron density fluctuations, and (3) poloidal rotation. Simultaneous measurements of the three quantities are enabled by an array of six monostatic antennas which inject from an equatorial port on the outboard side of the ITER vessel. Low-loss transmission lines, consisting of corrugated, overmoded waveguide and miter bends, transmit the 30–165 GHz, O- and X-mode signals to and from the ITER plasma. Integrated transmission-line components serve a range of purposes, such as protection from high-power stray radiofrequency radiation, accommodation of transmission-line displacement, and simultaneous measurement of reference and plasma phases during the discharge. Broadband transmission signals are realized by full-band microwave transceivers combined with quasi-optical multiplexing. A field-programmable gate array (FPGA) processor demodulates the profile reflectometer signals, enabling real-time density profile measurements for plasma control system feedback. A full-scale transmission line test facility provides an integrated environment to assess the performance of critical LFSR components. Theoretical modeling together with insertion loss measurements provide the basis for a comprehensive power budget, which accounts for transmitted output power, transmission-line losses, antenna coupling, and plasma effects. Results indicate that high signal-to-noise ratios are achievable with the current design. A synthetic reflectometer model, using real design parameters and baseline ITER profiles, has been developed to estimate the return signal. With evolving microwave and data acquisition technologies, full-band, ultrafast sweeps (<1 μs) will be realizable for ITER.

Slot antenna excited by novel substrate integrated coaxial line cavity for millimetre wave application

In this Letter, a novel compact slot antenna has been realised using substrate integrated coaxial line (SICL) cavity. SICL technology helps to achieve cavity size of 0.41 λ 0 × 0.48 λ 0 while maintaining its inherent advantage of self shielded and low loss transmission line at millimetre frequencies. A SICL cavity is designed by shorting the middle conductor at the two edges and keeping the other two edges separated from the sidewall. The eigenmode analysis affirms the presence of a dominant TEM mode at 28 GHz along with the presence of SICL even and odd modes. A half wavelength diagonal slot is etched on the bottom plate of the cavity to disturb the TEM mode surface current at 28 GHz. Measurement results show the SICL cavity backed slot antenna exhibits a gain of 5.6 dBi at 28.6 GHz and high front-to-back ratio better than 17 dB. The SICL-based cavity exhibits millimetre wave resonance with much smaller size, which helps to improve the compactness of the design. The proposed antenna can be used for millimetre wave applications like handheld mobile devices at millimetre-wave frequencies.

Millimeter-Wave Butler Matrix Beamforming Circuit Using Finline in Double-Layer Dielectric Substrate

This article presents a new kind of finline in double-layer dielectric substrate and its beamforming circuit of Butler matrix in the millimeter-wave band. The finline is constructed by inserting a slotline between two dielectric substrate layers. In this configuration, it is bounded within a closed structure composed of a double-layer dielectric substrate and two rows of via-hole arrangement, contributing to low dispersion and low radiation loss of the finline characteristics. The proposed finline design aims to provide a low-complexity and low-loss transmission line which is applied to the Butler matrix design. A $4\times 4$ Butler matrix for 4 switchable beams is realized by using the finline in the double-layer dielectric substrate. In addition, a waveguide-to-finline transition is developed as a feeding circuit for the Butler matrix. Characteristics of the proposed transition and the Butler matrix were analyzed by electromagnetic analysis of the finite element method and demonstrated by experiments at 79 GHz. The proposed Butler matrix obtains a wideband characteristic and an acceptable insertion loss of 2.42 dB. The array factor which is calculated from the measured amplitude and phase outputs 4 switchable beams with the beam directions of +14°, −46.5°, +46.5° and −14°, respectively. The proposed beamforming circuit using finline in double-layer dielectric substrate would be attractive for millimeter-wave applications due to its performance and low cost.

168-195 GHz Power Amplifier With Output Power Larger Than 18 dBm in BiCMOS Technology

This paper presents a 4-way combined G-band power amplifier (PA) fabricated with a 130-nm SiGe BiCMOS process. First, a single-ended PA based on the cascode topology (CT) is designed at 185 GHz, which consists of three stages to get an overall gain and an output power higher than 27 dB and 13 dBm, respectively. Then, a 4-way combiner/splitter was designed using low-loss transmission lines at 130-210 GHz. Finally, the combiner was loaded with four single-ended PAs to complete the design of a 4-way combined PA. The chip of the fabricated PA occupies an area of 1.35mm 2 . The realized PA shows a saturated output power of 18.1 dBm with a peak gain of 25.9 dB and power-added efficiency (PAE) of 3.5% at 185 GHz. A maximum output power of 18.7 dBm with PAE of 4.4% is achieved at 170 GHz. The 3-dB and 6-dB bandwidth of the PA are 27 and 42 GHz, respectively. In addition, the PA delivers a saturated output power higher than 18 dBm in the frequency range 140-186 GHz. To the best of our knowledge, the power reported in this paper is the highest for G-band SiGe BiCMOS PAs.

Transmission lines and resonators based on quantum Hall plasmonics: Electromagnetic field, attenuation, and coupling to qubits

Quantum Hall edge states have some characteristic features that can prove useful to measure and control solid state qubits. For example, their high voltage to current ratio and their dissipationless nature can be exploited to manufacture low-loss microwave transmission lines and resonators with a characteristic impedance of the order of the quantum of resistance $h/e^2\sim 25\mathrm{k\Omega}$. The high value of the impedance guarantees that the voltage per photon is high and for this reason high impedance resonators can be exploited to obtain larger values of coupling to systems with a small charge dipole, e.g. spin qubits. In this paper, we provide a microscopic analysis of the physics of quantum Hall effect devices capacitively coupled to external electrodes. The electrical current in these devices is carried by edge magnetoplasmonic excitations and by using a semiclassical model, valid for a wide range of quantum Hall materials, we discuss the spatial profile of the electromagnetic field in a variety of situations of interest. Also, we perform a numerical analysis to estimate the lifetime of these excitations and, from the numerics, we extrapolate a simple fitting formula which quantifies the $Q$ factor in quantum Hall resonators. We then explore the possibility of reaching the strong photon-qubit coupling regime, where the strength of the interaction is higher than the losses in the system. We compute the Coulomb coupling strength between the edge magnetoplasmons and singlet-triplet qubits, and we obtain values of the coupling parameter of the order $100\mathrm{MHz}$; comparing these values to the estimated attenuation in the resonator, we find that for realistic qubit designs the coupling can indeed be strong.

60 GHz square open‐loop resonator (SOLR) based on planar Goubau line (PGL) technology

This study presents the design, fabrication, and measurement of a square open-loop resonator (SOLR) on high resistivity silicon substrate feed with a planar Goubau line (PGL), which is a very low-loss transmission line around 60 GHz fabricated through a very simple and low-cost process. Electromagnetic simulations using ANSYS high frequency structure simulator are performed for the PGL structure, in order to determine the PGL characteristics (impedance, losses and quality factor) versus the line width. The geometrical parameters of the SOLR structure are studied to observe their impact on reflection and transmission properties. An equivalent lumped element circuit is extracted from the distributed planar design to study and optimise the resonating structure using Advanced Design System. This electrical circuit response is successfully compared to the planar electromagnetic structure one, and a parametric study permits to better understand the role of the different circuit elements. Field displays lead to a better understanding of the SOLR behaviour. For measurement purpose of the fabricated structure, a coplanar waveguide-PGL transition is optimised with 0.9 dB losses. Simulation and measurement results show good performances for filter applications with 1 dB losses and small size at 60 GHz for 10% bandwidth.

Developments for collective Thomson scattering equipment with a sub-THz gyrotron in LHD

Plan of collective Thomson scattering (CTS) experiment for the Large Helical Device (LHD) in NIFS with a 303 GHz gyrotron is under way. Use of a sub-THz gyrotron expands the CTS-applicable region of plasma parameters. In LHD, sub-THz CTS can be applied to the high density operation region, plasmas with impurity hole, etc. Moreover, sub-THz CTS is expected to be free from ECE noise. Its “collective” use with 77 GHz and 154 GHz CTS will compose a powerful diagnostic system. A high power sub-THz gyrotron with a frequency of 303 GHz has been developed. Its maximum power is 320 kW. It oscillates in pulse mode and the maximum pulse width is around 100 μs, which is sufficient for use in CTS experiments. A whispering gallery mode TE22,2was adopted for this gyrotron to avoid mode competition. Careful frequency measurement has proved purely single mode oscillation of the TE22,2mode including turn-on and turn-off phases of the oscillation pulse. This is consistent with mode competition calculations taking account of a finite voltage rise time. A low loss transmission line is necessary for CTS. We have two possibilities. One is a new line with 1.25 inch corrugated waveguides that are optimized for the 300 GHz band. Transmission test with the 303 GHz gyrotron has been carried out and a sufficiently low loss coefficient has been confirmed. The other is to use an existing line with 3.5 inch corrugated waveguides for lower frequencies such as 77 GHz and 154 GHz. Transmission test has been carried out with the 303 GHz gyrotron and a sufficiently low loss coefficient has been confirmed also for 3.5 inch corrugated waveguides. An existing line with 3.5 inch corrugated waveguides will be used in the initial phase of 303 GHz CTS experiment.