Artificial Transmission Lines Research Articles

Compact microstrip patch antenna loaded with Artificial Transmission Line for wireless applications

ABSTRACT This article presents an efficient yet simple spiral antenna design methodology for 2.44 GHz Wireless Local Area Network (WLAN) applications. In the suggested design, the antenna’s radiating section is redesigned with a particular Artificial Transmission Line (ATL) construction that allows for good downsizing. Circuit analysis and electromagnetic solver are used to verify the design, which demonstrate good agreement with the measured results. The electromagnetic simulation and passive component analysis reveal that the new design matches the traditional designs in terms of frequency tuning and size reduction. The overall footprint of the proposed ATL design is (33 × 25 × 1.6) mm3 which equals to 0.2684λ×0.2033λ×0.013λ, where λ is the distance travelled by the wave per cycle at the operating frequency of 2.44 GHz. The antenna has a gain of 3.8dBi and a 50Ω impedance. Modifying the interdigital capacitance and inductance used in the ATL structure to achieve a longer electrical length of the line can also improve the wave guide mode of excitation. As a result, the phase constant is regulated, allowing for good antenna size minimisation. The effect of interdigital inductance and capacitance on the operating bands is also analysed.

High kinetic inductance NbTiN films for quantum limited travelling wave parametric amplifiers

A wide-bandwidth and low-noise amplification chain in the microwave regime is crucial for the efficient read-out of quantum systems based on superconducting detectors, such as Microwave Kinetic Inductance Detectors (MKIDs), Transition Edge Sensors (TESs), Magnetic Microcalorimeters (MMCs), and RF cavities, as well as qubits. Kinetic Inductance Travelling Wave Parametric Amplifiers (KI-TWPAs) operated in a three-wave mixing fashion have demonstrated exceptional dynamic range and low-noise performance, approaching the quantum limit. These amplifiers can be fabricated using a single layer of a high kinetic inductance film as weakly dispersive artificial transmission lines, with the ability to control the phase-matched bandwidth through dispersion engineering. In this study, we present the optimisation of the rf sputter-deposition process of NbTiN films using a Nb80%Ti20% target, with the goal of achieving precise control over film characteristics, resulting in high kinetic inductance while maintaining a high transition temperature. The parameter landscape related to the different sputtering conditions, such as pressure, power, and nitrogen flow, has been explored and the film thickness has been used as a fine-tuning parameter to adjust the properties of the final NbTiN films used for the fabrication of KI-TWPAs. As a final result, we have obtained a NbTiN film with a kinetic inductance of 8.5 pH/sq which we have exploited to fabricate KI-TWPA prototype devices, showing promising amplification performance.

Analysis and Design of Novel 180° Hybrid for U-Band Monolithic Subharmonic Mixer in 0.15-μm GaAs pHEMT Technology

In this brief, a novel reduced-size 1800 hybrid is presented to implement a U-band subharmonic mixer (SHM) via a 0.15-μm GaAs pHEMT process. The isolations between Σ-port and -port of the proposed 1800 hybrid are significantly enhanced by two structures: one is a compact multiconductor edge-coupled line balun with artificial transmission line and the other is an in-phase power divider composed of λLO/4 coupled line. As a proof-of-principle demonstration, a single balanced SHM with an antiparallel diode pair configuration is designed and fabricated, which exhibits a conversion gain of -12.25 dB 1 1.55 dB within the operating RF frequency of 40 to 60 GHz under 14 dBm LO pumping power. The improved isolations of LO-to-RF and 2LO-to-RF are 33 to 47 dB and 44 to 57 dB, respectively. The measured results surpass previously reported performance of SHMs.

A Compact Fully-Differential Distributed Amplifier with Coupled Inductors in 0.18-µm CMOS Technology

This paper presents a compact fully-differential distributed amplifier using a coupled inductor. Differential distributed amplifiers are widely required in optical communication systems. Most of the distributed amplifiers reported in the past are single-ended or pseudo-differential topologies. In addition, the differential distributed amplifiers require many inductors, which increases the silicon cost. In this study, we use differentially coupled inductors to reduce the chip area to less than half and eliminate the difficulties in layout design. The challenge in using coupled inductors is the capacitive parasitic coupling that degrades the flatness of frequency response. To address this challenge, the odd-mode image parameters of a differential artificial transmission line are derived using a simple loss-less model. Based on the analytical results, we optimize the dimensions of the inductor with the gradient descent algorithm to achieve accurate impedance matching and phase matching. The amplifier was fabricated in 0.18-μm CMOS technology. The core area of the amplifier is 0.27 mm2, which is 57% smaller than the previous work. Besides, we demonstrated a small group delay variation of ±2.7 ps thanks to the optimization. the amplifier successfully performed 30-Gbps NRZ and PAM4 transmissions with superior jitter performance. The proposed technique will promote the high-density integration of differential traveling wave devices.

Compact Bandwidth-Enhanced 180-Degree Phase Shifter Using Edge-Coupled Multi-Microstrip and Artificial Transmission Line.

Compactness has obtained sufficient importance in wideband phase shifter design considerations, as it is directly related to fabrication cost. In this paper, a novel structure was presented to create compact broadband 180-degree phase shifter, which has the advantages of enhanced bandwidth and significantly reduced chip area. The proposed configuration consists of edge-coupled multi-microstrip lines (ECMML) and an artificial transmission line (ATL) with dual-shorted inductors, both of which have the periodic shunt load of capacitors. The ECMML can provide a high coupling coefficient, leading to an increase in the bandwidth, while the introduced capacitors can greatly reduce the line length (35.8% of the conventional method). To verify the relevant mechanisms, a wideband switched network with compact dimensions of 0.67 × 0.46 mm2 was designed via 0.15-micrometer GaAs pHEMT technology. Combined with the measured switch transistor, it was shown that the proposed phase shifter exhibits an insertion loss of less than 2 dB, a return loss of greater than 12 dB, a maximum phase error of less than 0.6° and a channel amplitude difference of less than 0.1 dB in the range of 10 to 20 GHz.

On the design of miniaturized C-shaped antenna based on artificial transmission line loading technique

This article presents an effective miniaturized antenna based on an artificial transmission line loading approach. The proposed antenna is a compact C-shaped radiating element backed by defected ground plane structure and fed by a line transition structure. The antenna is modelled to operate at 2.4 GHz with −32.99 dB return loss and operates from 2.33 GHz to 2.52 GHz with 77.55% fractional bandwidth and a gain value of 2.1 dBi. Equivalent circuits are extracted using the transmission line modelling technique. Moreover, the design has an overall substrate dimension of (20 × 30 × 1.6) mm3, which is suitable for compact wireless devices. Here antenna miniaturization is carried out through patch and ground extensions along with artificial transmission line structures incorporated. The antenna is fabricated and the measured result is in good agreement with the calculated and simulated results. In addition, by transmission line loading in the proposed design, the radiator is configured to work at 2.4 and 3.7 GHz.

A Millimeter-Wave GaN MMIC Front End Module with 5G NR Performance Verification

This paper proposes a millimeter-wave (mmWave) 5G front end module (FEM) based on multiple gallium nitride (GaN) monolithic microwave integrated circuits (MMICs) with 5G new radio (NR) performance verification. The proposed structure is configured by a wide band GaN single-pole double-throw (SPDT) switch MMIC, a GaN low-noise amplifier (LNA) MMIC, and a GaN power amplifier (PA) MMIC with the target operation band from 26.5 GHz to 29.5 GHz. The LNA and PA MMICs are designed with 150 nm GaN/SiC technology, and the SPDT MMIC is designed with 100 nm GaN/Si. The LNA MMIC shows the measured noise figure less than or equal to 2.52 dB within the operation band. The PA MMIC is based on a two-stage configuration and shows about 35 dBm measured saturated power with power-added efficiency better than 34% within the operation band. Also, the SPDT MMIC is based on an artificial transmission line configuration for wideband performance and shows that the measured insertion loss is less than 1.6 dB, and the measured isolation is higher than 25 dB within the operation band. Furthermore, all MMICs are integrated within a single carrier as an FEM and successfully verified by 5G NR test signals.

A Superconducting RF Low-Pass Filter Based on Ti/TiN Artificial Transmission Line for Detector and Qubit Readout

A Superconducting RF Low-Pass Filter Based on Ti/TiN Artificial Transmission Line for Detector and Qubit Readout

Design of 2–16 GHz Non-Uniform Distributed GaN HEMT MMIC Power Amplifier with Harmonic Suppression Network

In this paper, an ultra-wideband (UWB) power amplifier (PA) on a 0.25 μm gallium-nitride (GaN) on silicon carbide (SiC) high-electron-mobility transistor (HEMT) process, operating in Ku-band, is presented. The broadband PA design is based on the four-stage non-uniform distributed amplifier structure. In order to improve the efficiency of the PA, a harmonic suppression network is added at the output of the drain artificial transmission line. At the same time, a capacitor is connected in series at the input of the gate, which is used to compensate for the phase offset of the gate and increase the cut-off frequency of the PA. The final gate width of the first stage is 0.56 μm, and the other three-stage gate widths are all 0.32 μm. Over the frequency range of 2–16 GHz, the simulated results of this NDPA exhibit a power-added efficiency (PAE) of 16.6–27%, a saturated continuous wave (CW) output power of 35–37 dBm, a small signal gain of 9.1–11.6 dB, and output return losses of 5–15 dB.

A K-Band CMOS Standing Wave Oscillator Using Digital-Controlled Artificial Dielectric Differential Transmission Lines

This letter presents a K-band standing wave oscillator (SWO) based on digital-controlled artificial dielectric differential transmission lines (DiCAD-DTLs). By combining the unique property of constant phase and digitally controlled wide tuning range, the proposed design achieves a better balance between phase noise and tuning range. A compact layout and high operating frequency are, hence, possible, since DiCAD-DTLs in this design behave like a resonator instead of a capacitor bank. This chip was fabricated in a standard 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process with an area of 0.035 mm2. It achieves a tuning range from 19.2 to 21.6 GHz. The measured phase noise is around −104.7 dBc/Hz at a 1-MHz offset. This oscillator including buffer consumes 5 mA from a 1.5-V supply, demonstrating a figure of merit (FOM) and FOM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {_{T}}$ </tex-math></inline-formula> of −181.8 and −183.3 dBc/Hz, respectively.

Analysis and Design of a DC-12-GHz Distribution Power Amplifier for Quantum Key Distribution Application

A CMOS distributed power amplifier (DPA) for quantum key distribution (QKD) system to drive an electro-optical phase modulator is developed. Due to the requirement of amplifying high-speed non-return-to-zero (NRZ) signal, our design is supposed to provide enough bandwidth, including dc. To achieve sharp roll-off performance, the m-derived filter section is applied to realize the artificial transmission line rather than the constant-k section. Combining the theory analysis and simulation, the bridges between gain ripple, group delay fluctuation, or maximum linear output power and the parameters of time domain waveform are established. Furthermore, through analyzing the attenuation and delay of the transmission line, approaches to improving the frequency performance, such as gain variation and group delay fluctuation, are provided. The DPA is implemented in the 0.25- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process and achieves a bandwidth of dc-12 GHz, a gain of 11.54 dB with variation of ±1.34 dB, a group delay of 400 ps with fluctuation of about 100 ps, and a maximum output 1-dB compression point of 20.6 dBm. When a 1-Gb/s NRZ signal is applied to the DPA, the rise and fall times are both about 90 ps. The amplifier occupies an area of 2.8 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times0.94$ </tex-math></inline-formula> mm including pads and adopts the flip-chip package with low-temperature co-fired ceramic (LTCC) substrate.

Analysis and Demonstration of Mm-Wave Distributed Amplifiers With Modified Artificial Transmission Line Model

In this article, we analyze the mm-wave distributed amplifiers (DAs) with a modified artificial transmission line (M-ATL) model which includes the parasitic inductance and capacitance of the transistors. The characteristic impedance and the cutoff frequency are analytically derived with the M-ATL model. It is found that the parasitic inductance reduces the cutoff frequency, thus limiting the DA bandwidth and can be optimized for the group-delay equalization. To confirm the accuracy of the M-ATL model, two mm-wave DAs – ultra-wideband DA (UWDA) and variable-gain DA (VGDA) – were demonstrated using a 250-nm InP DHBT process. The on-chip bias network and group-delay equalization of the DAs are analyzed to improve the bandwidth and gain flatness. The measurement shows that the UWDA exhibits an average gain of 11 dB over the frequency from 6 to 261 GHz. The VGDA shows an average gain variation from 1.5 to 11.1 dB over the frequency from 6 to 200 GHz.

Flux-Pumped Josephson Travelling-Wave Parametric Amplifiers Based on Bi-SQUID Cells

We have proposed a new design of the Josephson traveling-wave parametric amplifier (JTWPA) capable of providing much higher spurious-free dynamic range (SFDR). For this purpose, we substitute dc SQUIDs for bi-SQUIDs in the used artificial signal transmission line driven by external travelling-wave magnetic flux. The increase of SFDR follows from the increased linearity domain of the phase-current relation in bi-SQUID as compared to dc SQUID. Optimal parameters for bi-SQUIDs have been determined. The first version of JTWPA was modeled to be fabricated using niobium process.

A Self-Matching Rectifier Based on an Artificial Transmission Line for Enhanced Dynamic Range

In this paper, self-matching rectifiers for enhanced input dynamic range are demonstrated. The method is based on an artificial transmission line, which consists of a stepped-impedance transmission line loaded with shunt varactors. The output DC voltage of the rectifier is fed back to the varactors to control the effective electrical length and characteristic impedance of the line. Because this bias voltage changes as the power input to the rectifier changes, a matching network that maintains impedance matching regardless of the input power can be developed without additional circuits, thus substantially improving the input dynamic range. The experimental results for prototype rectifiers show a dynamic range as wide as 25 dB with only a single Schottky diode, an improvement of 11 dB over the rectifier with a conventional matching scheme, in which the conversion efficiency remains above 50%. The effectiveness of the proposed method is also verified with the experimental results for rectennas based on the demonstrated rectifiers.

Broadband Josephson parametric amplifier using lumped-element transmission line impedance matching architecture

We present a fishbone-like lumped-element artificial transmission line to overcome impedance mismatch in a reflection-type Josephson parametric amplifier between a nonlinear resonator and an external transmission line. Using this easily prepared architecture, we design and fabricate a broadband Josephson parametric amplifier, which has gain in an excess of 20 dB with a bandwidth of hundreds of MHz. Furthermore, by varying the working point of the device, the operating frequency of amplification can be tuned in a wide frequency range of 1 GHz while the amplifier operates in the mode of either three-wave mixing or four-wave mixing. Such a parametric amplifier is suitable for engineering applications of superconducting circuit quantum electrodynamics.

Near‐field radio frequency identification leaky‐wave antenna based on artificial transmission line

The artificial transmission line (ATL) has a good characteristic of wavelength shortening, which can effectively cut down the size of microwave devices. In this article, the near-field radio frequency identification antenna based on an ATL was proposed. It mainly includes the radiating unit structure on the upper layer and the feeding structure on the lower layer. The two layers are connected by copper pillars for feeding. The height of the copper pillars is 16 mm (h0), which can obtain the maximum bandwidth. The antenna unit based on ATL consists of three curved microstrip lines, two interdigital microstrip lines, and four open microstrip lines. The interdigital structure on the upper layer of the antenna unit mainly affects the resonant frequency of the antenna unit, and the asymmetric interdigital microstrip lines increase the impedance matching bandwidth of the antenna unit. Compared with previous antennas, the proposed antenna features a low profile, and a good miniaturization based on an ATL by bending inductance and interdigital capacitance. The leaky-wave characteristic makes the energy radiate at a certain angle on the surface of the antenna. The leaky-wave characteristic and circular polarization characteristic of the antenna achieve a uniform field distribution. The simulated and measured bandwidth cover from 0.78 to 1.1 GHz for |S11| less than −10 dB. More importantly, the antenna has a large recognition area. The measured results demonstrate that the proposed reader antenna has a 100% read rate in 400 × 350 × 400 mm3 area in the metal shelf.

Compact two-position phase shifter

The paper proposes and investigates the topology of a phase shifter based on a directional coupler. The dimensions of such a device are reduced by using artificial transmission lines instead of quarter-wave sections. By connecting several pairs of phase-shifting cells instead of the usual one, it was possible to obtain a phase shifter design with two phase shifts (instead of one).

3D Printed RFID Tag Antenna Miniaturized Through Volumetric Folding and Slow-Wave Structures

Radio-frequency identification (RFID) is becoming important with emerging applications for smart cities. RFID Tags are required to be small in size, low in cost and must exhibit as long read range as possible. There is a direct tradeoff between Tag antenna size and its read range. In this work, we study this tradeoff through the use of a relatively higher dielectric constant substrate, volumetric folding, and slow-wave structures (SWS). A 3D antenna design is chosen due to two reasons, 1) it can be folded on a 3D structure, 2), the 3D structure can be used as a package for electronics (in case of active RFID implementation). To enable a low-cost realization, the antenna substrate (package) has been 3D printed with filaments of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\varepsilon }_{r}={5}.{3}$ </tex-math></inline-formula> . A dipole antenna has been folded on this 3D substrate, in a way that the electromagnetic fields radiating from various segments of the antenna do not cancel with each other. Finally, the antenna is loaded with specially designed SWS, whose values have been estimated using artificial transmission line theory. The final antenna design, operating at 866.9 MHz, has a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${ka}$ </tex-math></inline-formula> of 0.26 and demonstrates a radiation efficiency of 32%. The antenna is integrated with a commercial RFID chip (Monza R6) through a silver paste and the measured read range is 2.73 m, while the corrected read range is 4.05 m when the impedance mismatch is considered. Despite being one of the smallest and the lowest cost design (involving 3D printing), the Tag demonstrates one of the highest read range.

Highly compact and harmonic suppressed branch line balun using artificial transmission lines

In this article, a compact and harmonic suppressed microstrip branch line balun is designed using artificial transmission line (ATL) units. The stopband response of open-stubs present in the ATL units has been utilized to suppress the spurious passbands. Design guidelines are given with graphs and equations based on the lossless transmission line model and an even-odd mode technique. To demonstrate the proposed design theory, an experimental prototype branch line balun operating at 0.9 GHz, having 10% relative circuit area and up to 5th harmonic suppression is presented.

Dual-Band/Dual-Mode Rat-Race/Branch-Line Coupler Using Split Ring Resonators

A novel dual-band/dual-mode compact hybrid coupler which acts as a dual-band branch-line coupler at the lower band and as a rat-race coupler at the higher band is presented in this paper. One of the most interesting features of the proposed structure is that outputs of the proposed coupler in each mode of operation are on the same side. This unique design is implemented using artificial transmission lines (ATLs) based on open split ring resonators (OSRR). The low-cost miniaturized coupler could be operated as a dual-band 90° branch-line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz. The proposed coupler could be utilized in the antenna array feeding circuit to form the antenna beam. The structure’s analytical circuit design based on its equivalent circuit model is provided and verified by measurement results.