High-impedance Transmission Line Research Articles

Modified photodiode equivalent circuit model considering coplanar waveguide electrodes

Accurate equivalent circuit models can assist in better analyzing the performance of photodetectors. This study proposes a modified photodiode (PD) equivalent circuit model that considers coplanar waveguide (CPW) electrodes. First, the CPW electrodes of the PD are analyzed using high-frequency structure simulation software and advanced design simulation software. Skin effect occurs inside the electrode at high frequencies, increasing the PD loss and reducing the bandwidth. Subsequently, the extraction formula for the proposed model is derived, and the proposed model is compared with two conventional CPW electrode models. The proposed model effectively eliminates the frequency-dependency issue in the parameter extraction process of previous models, thereby demonstrating its accuracy. Furthermore, simulation and experimental results validate the reliability of the proposed model. Among the entire frequency band, the proposed model has good stability and a low error rate and can achieve excellent fitting with the measured results. Compared with previous studies, the average error rate is reduced by over 10%, demonstrating a significant improvement. Finally, the influence of the skin effect and high-impedance transmission lines on PD performance is analyzed and a viable approach to improve the bandwidth of PDs is proposed. The proposed model provides a viable approach to model and optimize CPW structures and is significant for the design of high-performance PDs.

Functional-renormalization-group approach to circuit quantum electrodynamics

A nonperturbative approach is developed to analyze superconducting circuits coupled to quantized electromagnetic continuum within the framework of the functional renormalization group. The formalism allows us to determine complete physical pictures of equilibrium properties in the circuit quantum electrodynamics (cQED) architectures with high-impedance waveguides, which have recently become accessible in experiments. We point out that nonperturbative effects can trigger a breakdown of the supposedly effective descriptions, such as the spin-boson and boundary sine-Gordon models, and lead to qualitatively unique phase diagrams. The origin of the failure of conventional understandings is traced to strong renormalizations of circuit parameters at low-energy scales. Our results indicate that a nonperturbative analysis is essential for a comprehensive understanding of cQED platforms consisting of superconducting circuits and long high-impedance transmission lines.

A Self-Packaged SISL Low-Power Rectifier Based on a High-Impedance Line for C-Band Applications

In this letter, a self-packaged substrate-integrated suspended line (SISL) rectifier is proposed. The rectifier consists of a quarter-wavelength high-impedance transmission line, a diode, a tuning inductor, and a dc pass filter. The lower the power is, the lower the rectifying efficiency is. At a low input power level, the diode impedance real part is almost zero. A tuning inductor is introduced to form a parallel resonator to enhance the diode voltage. A quarter-wavelength high-impedance line is presented to match the rectifying diode to the source. In addition, due to the self-packaging characteristics and air cavity of SISLs, the radiation loss and dielectric loss of the proposed rectifier are reduced. A rectifier was designed, fabricated, and measured at 5.8 GHz. The radio frequency (RF)-dc conversion efficiency reaches 3.5% at −30 dBm, which is close to its theoretical estimated efficiency at 5.8 GHz. This ultralow power rectifier may be used in energy harvesting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band.

Effects of underfill on wideband flip-chip packaging for 5G millimeter-wave applications

This letter investigates the effects of the underfill on the wideband flip-chip packaging for 5G millimeter-wave (mm-Wave) applications. For accurate interconnect design, a new hybrid equivalent circuit model is proposed. Targeting at the phased array systems with high density I/Os, a compact anti-pad structure is implemented and co-designed with the high impedance transmission line and the low-cost 90 μm solder balls, compensating the flip-chip capacitive parasitics and realizing the compact low-loss interconnect. To evaluate the underfill effect on the interconnect parasitics, both theoretical analyses and simulations are undertaken. For demonstration, by using a glass substrate with the fan-out process, back-to-back flip-chip packaging structures are designed, fabricated, and measured. Measured results demonstrate that with and without underfill U8410-99 the interconnect return loss is better than 20 and 10 dB from DC to 90 GHz, with an insertion loss of 0.2 and 0.45dB at 60GHz, respectively.

Mixed Dual-Band Impedance Transformer With Embedded Transmission Zero

Dual- and multi-band impedance transformers are important components in radio frequency (RF) and microwave circuits for contemporary communication systems. This brief presents a mixed transmission zero embedded dual-band impedance transformer that consists of transmission lines and lumped elements, operates at two uncorrelated frequencies. The proposed impedance transformer is appropriate for a load with frequency-dependent complex impedance. The presented transformer has the advantages of compact size and the absence of extremely high or low impedance transmission lines and stubs. In addition, the values of the transformer parameters are determined using the presented closed-form design formula. The proposed structure is validated through simulations and measurements.

Compact Uniform Folded Section Rat-Race Couplers with Harmonic Suppression

In this paper, two 50Ω terminated rat-race hybrid couplers based on uniform folded structures are proposed for equal division of power. The proposed designs are of simple in geometry and have an area of only one-fourth of the conventional coupler. The first technique is two-fold double section topology operating at 1.77 GHz designed with the conventional impedance ratio of √2 between port and transmission line which exhibits good in-band characteristics and requires a minimum track width of 0.8 mm. The second technique is stub-loaded double section topology where the novelty lies in deploying impedance matched stubs which avoids high impedance lines by maintaining an impedance ratio less than 2 between port and transmission line. In addition to good passband characteristics, it also suppresses higher harmonics up to 6.3f 0 and requires a minimum track width of 0.41 mm which makes it easy for realization. The bottom line of both designs is to achieve extreme structural simplicity without using high impedance transmission lines of more than 100Ω, narrow tracks less than 0.4 mm, lumped elements, and via holes. The prototype of the proposed coupler is fabricated and the simulated results are validated using measurements.

A Novel Coupled Line Directional Coupler Design For L-Band Wireless Applications

Directional couplers are commonly used in microwave circuit design. Therefore, miniaturization of these components is very important. This paper presents the miniaturized microstrip coupled line directional coupler (CLDC) for L-band wireless applications. The coupled line directional coupler presented in the article was designed and simulated. In this paper coupler line directional coupler has been proposed with a low coupling factor. The proposed CLDC operates at the L-band and it is designed for use in mostly wireless applications. High and low impedance transmission lines are used to miniaturize the CLDC. The CLDC has been designed using a substrate material of FR-4 with a dielectric constant of 4.3 and substrate thickness of 1.57 mm. The size of the designed CLDC is 33.4 x15.05 〖mm〗^2. This is 58 % less than are of the conventional coupled line directional couplers. Also, The reflection coefficient and isolation level are in the permissible level in order for the proposed CLDC to be utilized in L-band wireless applications. The coupling factor of the designed coupled line directional coupler is between 28 dB and 21 dB at the L-band. The measured return loss value is better than 19 dB. Same time the isolation value is better than 23 dB at L-band.

A novel balanced‐to‐unbalanced branch‐line coupler with large power division ratio

A novel balanced-to-unbalanced branch-line coupler with a large power division ratio (PDR) is proposed in this paper. The proposed coupler consists of six transmission-line sections, which can be easily synthesized with the prescribed PDR. By changing the electrical lengths of two transmission lines, a large PDR range can be obtained without the use of high-impedance transmission lines. The closed-form design equations are provided and discussed. To verify the proposed circuit, a coupler prototype with the PDR of 20 dB and the center frequency of f0 = 1.0 GHz is designed and fabricated. Simulation and measurement results are in good agreement. When the balanced port A is excited, the measured differential-mode to single-ended transmission coefficients at f0 for the unbalanced ports D and C are |SsdDA| = −0.28 dB and |SsdCA| = −20.02 dB, respectively, which meet the desired PDR. The measured |SddAA| at f0 is −33.6 dB with a −10-dB bandwidth of about 12.7% from 0.933 to 1.059 GHz. The |SscDA| and |SscCA| are less than −29.5 dB with a −18-dB bandwidth of 22.4% from 0.924 to 1.157 GHz.

Design and Fabrication of a Low-Cost Mobile Antenna for Low VHF

We propose a wideband, low-cost, and portable antenna that includes three sections of straight wire radiator, high-impedance Transmission Line (TL), and a matching network inside the base antenna, all connected in series in that order. The optimized radiator height is 152 cm which is connected to a matching network by means of implemented 70 cm high-impedance coaxial TL lied along the axis of the radiator. With the help of basic simulations of such a radiator and high-impedance TL without any matching network, it is found that an omni-directional radiation pattern can be obtained within a given frequency of low VHF. For broadening its operating bandwidth and practical implementation of such a structure, a wideband balun and matching network are implemented such a way that it can be embedded in the base section. To validate the simulated results, the designed structure for low VHF (30∼108 MHz) is fabricated and successfully measured. The measurements on such an antenna show a 115% bandwidth with VSWR < 2.6 and a maximum gain of 1.7 dBi at 90 MHz. It is shown that the fabricated antenna has a simple design and short radiator height in comparison with the commercial low-VHF antennas used for mobile applications. In addition, such a low-weight antenna is suitable for mounting on vehicles.

A microstrip planar lowpass filter with ultra-wide stopband using hexagonal-shaped resonators

Abstract A microstrip planar lowpass filter with ultra-wide stopband up to 40 GHz is presented. The filter is designed based on four types of hexagonal-shaped resonators, producing multiple transmission zeroes and extending the stopband. The high-impedance transmission line is folded to make the circuit more compact and form the coupling gaps between the adjacent resonators. A pair of folded open stubs are added to enhance the cut-off rate. As a result, an ultra-wide stopband with 23rd-harmonic suppression has been attained. A demonstration filter has been designed and fabricated with 3 dB cut-off frequency of 1.70 GHz. The measured results show that the relative stop bandwidth of the low-pass filter (LPF) is 182% with suppression level of 25 dB, covering 1.85–40 GHz. The functional area size of the filter is 21.50 × 21.70 mm, which corresponds to 0.198λ g × 0.200λ g (λ g is the guided wavelength at 3 dB cut-off frequency).

Phase-Variation Microwave Sensor for Permittivity Measurements Based on a High-Impedance Half-Wavelength Transmission Line

A phase-variation microwave sensor operating in transmission and implemented by means of a high-impedance half-wavelength sensing line is reported in this paper. The sensor is useful for dielectric constant measurements and dielectric characterization of materials. By forcing the electrical length of the sensing line to be a half-wavelength when it is loaded with the so-called reference (REF) material, perfect matching is obtained regardless of the characteristic impedance of the line. This fact can be used to enhance the sensitivity for small perturbations, by merely increasing the characteristic impedance of the sensing line. An exhaustive analysis that supports such conclusion is reported in the paper. Then, two prototype sensors are designed and fabricated for validation purposes. As compared to the ordinary phase-variation permittivity sensor implemented by means of a matched ( 50-Ω) line with identical length, the sensitivity for small perturbations in the proposed sensor is 2.1 times larger. Further advantages of these sensors are low-cost, small size, implementation in planar technology, and very simple design and fabrication, derived from the fact that the sensing region is a half-wavelength transmission line.

Transmon in a semi-infinite high-impedance transmission line: Appearance of cavity modes and Rabi oscillations

In this letter, we investigate the dynamics of a single superconducting artificial atom capacitively coupled to a transmission line with a characteristic impedance comparable or larger than the quantum resistance. In this regime, microwaves are reflected from the atom also at frequencies far from the atom's transition frequency. Adding a single mirror in the transmission line then creates cavity modes between the atom and the mirror. Investigating the spontaneous emission from the atom, we then find Rabi oscillations, where the energy oscillates between the atom and one of the cavity modes.

Photon-Instanton Collider Implemented by a Superconducting Circuit.

Instantons, spacetime-localized quantum field tunneling events, are ubiquitous in correlated condensed matter and high-energy systems. However, their direct observation through collisions with conventional particles has not been considered possible. We show how recent advances in circuit quantum electrodynamics, specifically, the realization of galvanic coupling of a transmon qubit to a high-impedance transmission line, allows the observation of inelastic collisions of single microwave photons with instantons (phase slips). We develop a formalism for calculating the photon-instanton cross section, which should be useful in other quantum field theoretical contexts. In particular, we show that the inelastic scattering probability can significantly exceed the effect of conventional Josephson quartic anharmonicity and reach order-unity values.

Compact and Tunable Forward Coupler Based on High-Impedance Superconducting Nanowires

Developing compact, low-dissipation, cryogenic-compatible microwave electronics is essential for scaling up low-temperature quantum computing systems. In this paper, we demonstrate an ultracompact microwave directional forward coupler based on high-impedance slow-wave superconducting-nanowire transmission lines. The coupling section of the fabricated device has a footprint of $416\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{2}$. At 4.753 GHz, the input signal couples equally to the through port and forward-coupling port (50:50) at $\ensuremath{-}6.7\phantom{\rule{0.2em}{0ex}}\mathrm{dB}$ with $\ensuremath{-}13.5\phantom{\rule{0.2em}{0ex}}\mathrm{dB}$ isolation. The coupling ratio can be controlled with dc bias current or temperature by exploiting the dependence of the kinetic inductance on these quantities. The material and fabrication processes are suitable for direct integration with superconducting circuits, providing a practical solution to the signal distribution bottlenecks in developing large-scale quantum computers.

GaN МИС малошумящего усилителя Х-диапазона

The purpose of this paper is to design a microwave monolithic integrated circuit (MMIC) for low noise amplifier (LNA) X-band (7-12 GHz) based on technology of gallium nitride (GaN) high electron mobility transistor (HEMT) with a T-gate, which has 100 nm width, on a silicon (Si) semi-insulating substrate of the OMMIC company. The amplifier is based on common-source transistors with series feedback, which was formed by high-impedance transmission line, and with parallel feedback to match noise figure and power gain. The key characteristics of an LNA are noise figure and gain. However, in this paper, it was decided to design the LNA, which should have a good margin in terms of input and output power. As a result, GaN technology was chosen, which has a higher noise figure compared to other technologies, but eliminates the need for an input power limiter, which in turn significantly increases the overall noise figure. As a result LNA MMIC was developed with the following characteristics: noise figure less than 1.6 dB, small-signal gain more than 20 dB, return loss better than -13 dB and output power more than 19 dBm with 1 dB compression in the range from 7 to 12 GHz in dimensions 2x1.5 mm², which has a supply voltage of 8 V and a current consumption of less than 70 mA. However, it should be said that LNA was only modeled in the AWR DE.

A High-Frequency/Power Ratio Wilkinson Power Divider Based on Identical/Non-Identical Multi-T-Sections With Short-Circuited Stubs

In this article, a systematic procedure is presented for the design of a dual-band unequal-split Wilkinson power divider (WPD) with high frequency and power division ratios. The design methodology is based on replacing the impractical high-impedance transmission line in the conventional divider with cascaded T-section structures with short-circuited stubs. The proposed methodology is simple and adopts distributed elements without reactive components to achieve a large power division ratio. The use of short-circuited stubs allows for circuit miniaturization in comparison to counterpart open-stub techniques. Furthermore, a high frequency ratio is obtained through optimizing the electrical and physical parameters of the T-sections based on a transmission lines theory framework as demonstrated in a simulated and measured prototype. To validate the proposed procedure, two WPD prototypes operating at 1/2.7 GHz and 1/4.4 GHz with a 1:10 power division ratio are simulated and measured. The theoretical response, supported by electromagnetic simulations and measurements, justifies the design concept.

Unlimited Power Division Ratio of Microstrip Balanced-to-Unbalanced Gysel-Type Arbitrary Power Divider

A microstrip balanced-to-unbalanced (BTU) Gysel-type arbitrary power divider without the high-impedance transmission-line (TL) section is proposed to eliminate the power division ratio (PDR) limit of the conventional microstrip BTU power dividers. The proposed circuit includes five moderate-impedance TLs having the same characteristic impedance in addition to a grounded resistor. The arbitrary PDR is easily obtained by varying the electrical length of the TLs without changing the characteristic impedances, especially the large PDR, which is difficult to achieve by means of conventional BTU power dividers. When the PDR is ∞, the proposed circuit becomes a balun. The closed-form design equations are derived and discussed. To verify the proposed circuit, three prototypes I, II, and III are designed and fabricated for PDRs of 10 dB, 20 dB, and ∞ dB, respectively. The measured PDRs are in good agreement with the simulations. The measured isolation between the output ports is higher than 31 dB for prototypes I and II. The measured insertion loss of the balun prototype is 0.194 dB. Furthermore, the common-mode suppression of greater than 32 dB and the return loss of higher than 22 dB are obtained for various PDRs.

Observation of quantum many-body effects due to zero point fluctuations in superconducting circuits

Electromagnetic fields possess zero point fluctuations which lead to observable effects such as the Lamb shift and the Casimir effect. In the traditional quantum optics domain, these corrections remain perturbative due to the smallness of the fine structure constant. To provide a direct observation of non-perturbative effects driven by zero point fluctuations in an open quantum system we wire a highly non-linear Josephson junction to a high impedance transmission line, allowing large phase fluctuations across the junction. Consequently, the resonance of the former acquires a relative frequency shift that is orders of magnitude larger than for natural atoms. Detailed modeling confirms that this renormalization is non-linear and quantum. Remarkably, the junction transfers its non-linearity to about thirty environmental modes, a striking back-action effect that transcends the standard Caldeira-Leggett paradigm. This work opens many exciting prospects for longstanding quests such as the tailoring of many-body Hamiltonians in the strongly non-linear regime, the observation of Bloch oscillations, or the development of high-impedance qubits.

Quasi-Reflectionless Microstrip Bandpass Filters Using Bandstop Filter for Out-of-Band Improvement

In this brief, a class of microstrip bandpass filters (BPFs) with quasi-reflectionless behavior on both input and output ports is presented. A single-port reflectionless BPF is proposed by shunt connecting one bandstop filter cell namely one-cell. This one-cell single-port reflectionless BPF is made up of a high impedance transmission line as a series band-pass filter section and a shunt-connected band-stop section with resistively terminated. In the operation passband, the bandpass filter section is used to transmit spectral energy, while the bandstop section is regarded as an open circuit. Besides, the out-of-band energy is absorbed by resistively component in the bandstop filter section. In order to achieve better out-of-band reflectionless characteristic, a two-cell two-port reflectionless BPF is constructed by shunt connecting two cells at input/output ports and one series bandpass filter section in the center. In addition, a three-cell reflectionless BPF is designed to further verify the improvement of out-of-band performance. Finally, two-cell and three-cell two-port reflectionless BPFs are fabricated and tested to verify the design concept. The measured results of these two reflectionless BPFs are in good agreement with the simulation ones.

Development and optimization of RF MEMS switch

Isolation and actuation voltages are important parameters in micro-electro-mechanical switches. These parameters can be destroyed by the effect of creating bulge and erosion in the surface of the beam. In this paper, a fabrication method is proposed to create a smooth and flat beam. Additionally, using two short high impedance transmission lines, the destructive effects on the input/output matching have been reduced. S-parameters and mechanical parameters of the proposed switch are calculated by the network analyzer and laser Doppler vibrometer. According to the results obtained from the proposed switch in the C–K band, the return loss, which is less than − 20 dB, and the highest isolation value, which is equal to − 20 dB, occur at the frequency of 21 GHz. Furthermore, the insertion loss is better than − 1 dB in the full frequency band, which is very desirable. The actuation voltage and resonance frequency were obtained at 18 V and 164 kHz, respectively. Finally, four steps are proposed to optimize the actuation voltage, isolation, stress and switching time, which results in reducing the actuation voltage by 37% and the isolation will increase by 46%. Maximum stress in the initial state is 25 MPa, and decreases to 10 MPa after optimization, which increases the lifetime of the switch.