Inverted Microstrip Line Research Articles

Liquid crystal-based reconfigurable antenna for 5G millimeter-wave

This paper proposed a frequency reconfigurable antenna that utilizes a multilayer structure of liquid crystal (LC) material. This antenna design incorporates a three-layer stacked structure to create an LC-injected cavity. The inverted microstrip line structure is designed to be in contact with the LC, serving as both a radiating element and a bias electrode. A parasitic patch is placed at the top of the antenna to enhance bandwidth. To prevent interference with DC and RF sources, a bias tee is integrated into the microstrip line input. Experimental results demonstrate that the proposed antenna exhibits excellent impedance matching and stable radiation patterns within the operational frequency range. By comparing the simulated performance of the existing LC antenna with our proposed design, the bandwidth is tripled at a center frequency of 30.3 GHz. In addition, the effective area of the proposed reconfigurable antenna (154 mm2) is 24.6% of the area of the previous reconfigurable antenna (625 mm2).

Symmetry Implications of a 60 GHz Inverted Microstrip Line Phase Shifter with Nematic Liquid Crystals in Diverse Packaging Boundary Conditions

Symmetry Implications of a 60 GHz Inverted Microstrip Line Phase Shifter with Nematic Liquid Crystals in Diverse Packaging Boundary Conditions

A Study on Dispersion Characteristics for Inverted Microstrip Lines

Inverted microstrip lines are studied for their dispersion characteristics for three different values of permittivity of the substrate using Galerkin Technique in Spectral Domain. This structure is very much useful as the current strip is attached at the lower surface of the dielectric substrate. Therefore it is rarely exposed to the outer medium results no effect due to external hazards and almost zero possibility to expose to electro- magnetic interference. Basis functions for the unknown strip current are chosen according to the ones specified in [1]. Basis functions in [1] were for slot magnetic currents and consequently they are modified for the particular problem by considering the modified boundary conditions for Maxwell’s field equations for this structure. For the theoretical development the Fourier transformation of the basis functions from space domain to spectral domain are considered. Variation of effective permittivity with available dielectric thickness has also been studied and the result shows a saturating tendency with increase in dielectric thickness.

Ferrite-Loaded Inverted Microstrip Line-Based Artificial Magnetic Conductor for the Magnetic Shielding Applications of a Wireless Power Transfer System

In this paper, we propose a ferrite-loaded inverted microstrip line (IML)-based artificial magnetic conductor (AMC) with a novel design that can provide complete magnetic shielding at the backside of the transmitting (Tx) coil while slightly improving the power transfer efficiency (PTE) of a wireless power transfer system (WPTS). The target frequency of the WPTS application is approximately 6.78 MHz. In the proposed design, the AMC is placed behind the Tx coil, and its magnetic shielding capability and PTE performance were verified through simulations and measurements. The size of the proposed AMC is 528 × 528 × 6.6 mm3. The measurement results verified that, compared with the Tx coil without an AMC surface, the proposed ferrite-loaded IML-based AMC can provide complete magnetic shielding while improving the PTE of the WPTS by approximately 8.05%.

Rethinking Liquid Crystal Tunable Phase Shifter Design with Inverted Microstrip Lines at 1–67 GHz by Dissipative Loss Analysis

Growing 5G/6G phased-array beam-steering applications, for which liquid crystal (LC) is one of the enabling technology candidates, have sparked interest in the modulation of the phase (and amplitude) of microwave and millimeter-wave signals. In this communication, fresh insights into the systematic design analysis of a 1–67 GHz passive inverted microstrip line (IMSL) phase shifter filled with highly anisotropic LC as tunable dielectric media are obtained. Based on waveguide disturbance tests to characterize the dielectric properties of the non-tunable PCB and tunable LC used in the IMSL phase shift device filled with a GT3-24002 LC layer (125 µm thick) partially enclosing a 220 µm wide, 17 µm thick, 1.35 cm long copper core line, a 0–π differential phase shift in the 1–67 GHz range with less than 2 dB insertion loss is reported. Dissipative loss analysis shows that the dielectric absorption of the LC is 21.28% of the input signal power at 60 GHz. Further investigation is performed to quantify the impacts of dielectric substrate thicknesses (PCB and LC) on the wave-occupied volume ratio (and hence the phase tuning range), as well as on dissipative losses (including conductor loss and dielectric loss). Specifically, conductor loss is observed to follow a linear relationship with the reciprocal of the LC thickness.

Determining dielectric properties of nematic liquid crystals at microwave frequencies using inverted microstrip lines

ABSTRACT In this paper, we have investigated the dielectric properties of nematic liquid crystals (NLCs) by measuring the resonant frequencies of inverted microstrip lines (IMSLs) of NLC being the substrate material at the microwave frequency band. The designed IMSL devices consist of a cavity for NLC mixture between the inverted microstrip line and the ground plane. The anisotropy values of the NLCs were determined by observing the change of the resonant frequency when the strength of external electric fields applied on the NLCs varied. The experiments demonstrated that the effective dielectric constant of the NLC can be manipulated by the proposed devices via external bias voltage for tuning. The accuracy of the method for determining the dielectric constants of JC-M-LC-E7 (JC-E7) and QYPD-036 LCs was analysed with several prototypes based on two separate designs. The high accuracy of 91% in permittivity determination was demonstrated, and the design and fabrication techniques are beneficial for making microwave components of high tunability.

Ka-Band Inductor-Shared SP${n}$ T DP${n}$ T Switches and Their Applications to TTD Phase Shifter

This paper describes Ka-band inductor-shared RF switches and their applications to a 35.2-ps 6-bit true-time-delay (TTD) switched-line (SL) phase shifter (PS). The inductor-shared RF switches share an inductor to match the input and output (I/O) ports of different states, which are realized with a switched inductor for SP ${n}\text{T}$ case and with a shared matching network for DP ${n}\text{T}$ case. The switches are applied to controlling most significant 3 bits of the proposed TTD SL PS. The delay lines and reference lines of the PS are implemented with microstrip lines and inverted microstrip lines in the same space, respectively. The dual-side microstrip lines allow it to have not only a small size but also compensation of the loss difference between the signal lines with different lengths. The least significant 3 bits are implemented with the modified structure of the SL PS, which reduces the size further by replacing a reference line by a series switch. The test chip is fabricated in a 65-nm CMOS process. It operates in the range of 20–30 GHz occupying a 0.18 mm2 core size. Its measured insertion loss and IP1dB are 11 dB and 6.5 dBm at 28 GHz, respectively. The measured gain error and rms delay error are less than 2 dB and 0.7 ps at operation frequencies.

Circularly polarised printed tilted beam antenna

A cavity-backed printed crank-line array antenna is presented as an inverted microstrip line structure for producing high gain circularly polarised (CP) tilted beam. The crank-line antenna element, in travelling wave condition, is fed with a printed Z-feed and terminated at the other end with a vertical open-ended printed stub. Single element exhibits an impedance bandwidth of 20% (3.6-4.4 GHz) for a VSWR<;2. A beam tilt of 35° with CP gain around 7.8 dBic is measured for an axial ratio of 2 dB at 4 GHz. A cavity-backed printed crank-line array with a tilted beam is formed by connecting two open crank-line radiation elements. The measured gain of the array is around 10.5 dBic across the operating frequency for an axial ratio <;3 dB. A beam tilt of 46° is achieved.

Tunable Microwave Bandpass Filters With Complementary Split Ring Resonator and Liquid Crystal Materials

In this paper, a novel planar waveguide filter based on liquid crystal materials is devised, and a half-mode corrugated substrate integrated waveguide (HMCSIW) tunable bandpass filter with complementary split ring resonator (CSRR) structure is proposed. The HMCSIW uses an array of quarter-wave open-circuit stubs to replace conventional substrate integrated waveguide (SIW). While retaining the original cut-off frequency of corrugated substrate integrated waveguide (CSIW), we reduce the circuit size by splitting the central axis to achieve the miniaturization. By utilizing band-stop features of the CSRR in microstrip structure and combining with the electronically controlled dielectric constant of liquid crystal materials with high modulation efficiency of inverted microstrip line structure, a CSRR-loaded HMCSIW bandpass filter with liquid crystal materials is implemented. The experimental results demonstrate that the center frequency of the new filter can be adjusted in a range of 0.65 GHz, the pass-band insertion loss is less than 3.4 dB, the return loss is less than -10 dB, and the structure size is 32 mm $\times \,\, 76$ mm, which verify that the designed tunable band-pass filter achieves good frequency selection performance.

A Frequency and Pattern Reconfigurable Antenna Array Based on Liquid Crystal Technology

A reconfigurable antenna array based on liquid crystal (LC) technology is proposed, which can dynamically tune operation frequency and achieve beam steering. The antenna element is composed of two parts: a microstrip patch array and a phase shifter using the inverted microstrip line (IMSL). The LC substrate is used to support the patch array for controlling its resonance frequency, while the LC-based IMSL phase shifter is adopted to tune the transmission phase by changing the effective permittivity of the LC. In order to verify the reconfigurable characteristics, the antenna array consisting of 1 × 4 elements are designed and numerically investigated. Simulation results show that this antenna can realize beam steering with a scanning angle range of (–20°, 20°), while its operation frequency can be actively tuned between 14.5 and 16.4 GHz.

Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

A novel tunable inverted microstrip filter based on liquid crystal

In this work, a microwave tunable filter of inverted microstrip with dual-mode resonator using liquid crystal (LC) technology has been designed, manufactured, and characterized. It comprises a thin LC layer between a ground plane and a directly coupled and inverted microstrip line. Central frequency tunability was realised by applying low ac voltages, thus involving low power consumption. The transmission characters of the filter were specifically designed for working at C-band microwave frequency range, which are allocated for many communication applications such as satellite, cordless telephone or weather radar systems. Additionally, its compact structure allows the device to be integrated on circuit board to adapt with other MW components for expanded applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1626–1628, 2016

A G-band terahertz monolithic integrated amplifier in 0.5-μm InP double heterojunction bipolar transistor technology**Project supported by the National Natural Science Foundation of China (Grant No. 61501091) and the Fundamental Research Funds for the Central Universities of Ministry of Education of China (Grant Nos. ZYGX2014J003 and ZYGX2013J020).

Design and characterization of a G-band (140–220 GHz) terahertz monolithic integrated circuit (TMIC) amplifier in eight-stage common-emitter topology are performed based on the 0.5-μm InGaAs/InP double heterojunction bipolar transistor (DHBT). An inverted microstrip line is implemented to avoid a parasitic mode between the ground plane and the InP substrate. The on-wafer measurement results show that peak gains are 20 dB at 140 GHz and more than 15-dB gain at 140–190 GHz respectively. The saturation output powers are −2.688 dBm at 210 GHz and −2.88 dBm at 220 GHz, respectively. It is the first report on an amplifier operating at the G-band based on 0.5-μm InP DHBT technology. Compared with the hybrid integrated circuit of vacuum electronic devices, the monolithic integrated circuit has the advantage of reliability and consistency. This TMIC demonstrates the feasibility of the 0.5-μm InGaAs/InP DHBT amplifier in G-band frequencies applications.

A novel tunable microwave filter integrated power dividers using liquid crystal

ABSTRACTThis article presents design considerations of a tunable microwave filter integrated power divider based on highly anisotropic liquid crystals (LCs), which helps to reduce the circuit size. The proposed device comprising a thin LC layer between a ground plane and a directly coupled inverted microstrip line exhibits the equal power splitting function with a tunable bandpass response. The integrated device results in sharp rejection and smaller circuit area, as compared with the cascaded connection of an equal power divider and tunable microwave filter. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2539–2543, 2015

An Effective Modeling Framework for the Analysis of Interconnects Subject to Line-Edge Roughness

This letter proposes a complete and efficient simulation framework to assess the effects of line-edge roughness appearing in on-chip lines. The modeling approach consists of three steps. First, a stochastic macromodel is created for the per-unit-length RLGC parameters of the line. Secondly, random conductor edge profiles are generated using randomized splines. These are combined with the stochastic macromodel to readily provide place-dependent RLGC parameters. Finally, the resulting nonuniform transmission line is analyzed by means of a fast and accurate perturbation technique. To validate the proposed approach, a statistical analysis of the response of a coupled inverted embedded microstrip line is carried out for different roughness parameters.

Microfluidically Tunable Microstrip Filters

A new approach for the development of tunable and reconfigurable microstrip (MS) devices is proposed. The basic idea consists of using a suspended substrate with an integrated network of plastic tubes, which can be selectively filled in with a high-permittivity dielectric fluid, e.g., water. The local change of the substrate effective permittivity achieved in such a way enables one to change, in a controlled and reversible manner, the electrical length of certain elements of MS circuits. As a proof-of-concept, tunable stub resonators based on suspended and inverted MS lines are designed and characterized in frequency and time domains. The same principle is then applied for the development of a fourth-order bandpass filter with 40% fractional bandwidth operating at 5 GHz. A tunable range of 19.5% with the insertion loss of 0.6 dB is demonstrated. The performance of the stub resonators and filter is validated successfully via prototyping.

Microstrip-Ridge Gap Waveguide–Study of Losses, Bends, and Transition to WR-15

This paper presents the design of microstrip-ridge gap waveguide using via-holes in printed circuit boards, a solution for high-frequency circuits. The study includes how to define the numerical ports, pin sensitivity, losses, and also a comparison with performance of normal microstrip lines and inverted microstrip lines. The results are produced using commercially available electromagnetic simulators. A WR-15 to microstrip-ridge gap waveguide transition was also designed. The results are verified with measurements on microstrip-ridge gap waveguides with WR15 transitions at both ends.

Wide Band Measurement of Dielectric Properties of Electronic Assembly Materials Inside an LTCC Fluidic Structure

Assembly materials such as underfillers or glob top epoxies are typically not specified regarding their dielectric properties for frequencies higher than 1 MHz. However, their behavior should be known for a wider frequency range in order to implement the appropriate parameters for RF and microwave simulations and designs. Typical methods to measure permittivity and loss tangent are based on parallel plate capacitor measurement with an impedance or network analyzer (up to about 1 GHz), S-parameter measurement of filled waveguides, coaxial transmission lines, or resonance methods (e.g., split post resonator, slit cavity resonator, ring resonator, open resonator). Most of these methods require specific sophisticated sample preparation. The paper describes a novel method based on suspended or inverted microstrip evaluation in a 3D LTCC structure. Suspended and inverted microstrip lines have lower insertion losses than standard microstrip lines due to the air gap between the line and the ground plane (reduced dielectric losses). Low loss structures are necessary to be able to measure low loss dielectrics. Such suspended or inverted microstrip lines can be easily achieved in LTCC by implementing a cavity structure. Inlets and outlets allow for the cavity to be filled with fluids after an initial S-parameter measurement of line properties (i.e., impedance, insertion loss, phase velocity). Measuring is repeated once the assembly material is cured. The change in impedance, phase velocity, and insertion contains the information about the material under test. Its properties are derived by curve fitting methods with a 3D electromagnetic field simulator. It is also possible to implement line resonators instead of through lines. In the latter case, the resonant frequency shift and the quality factor contains the material information. The procedure is demonstrated on a multilayer LTCC substrate based on low loss DP 9k7 and a commercial underfill material.

50-Gb/s Direct Conversion QPSK Modulator and Demodulator MMICs for Terahertz Communications at 300 GHz

We demonstrate direct quadrature modulator and demodulator monolithic microwave integrated circuits for future terahertz communications at 300 GHz based on the quadrature phase-shift keying (QPSK) modulation format. For the modulating and demodulating signal, we employed half-Gilbert cell mixers, which provide balanced signaling and moderate performance in conversion efficiency with a simple circuit configuration. In order to maintain the balance performance of the modulator and demodulator, passive baluns and couplers are implemented with thin-film microstrip lines, which exhibit less insertion loss than inverted microstrip lines (IMSLs), while the active mixers are based on IMSLs for short interconnections. The half-Gilbert-cell mixers have a wide enough operation bandwidth for high-throughput communications of more than 10% at 300 GHz. According to the static constellation of the modulator, imbalance is expected to be less than approximately ±0.6 dB ∠4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . A nonchip back-to-back experiment was conducted at up to 60 Gb/s, and 50-Gb/s operation was verified with a low bit error rate on the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> or less. The results demonstrate that the QPSK modulation scheme can be applied to double the data rate at terahertz frequencies.

Compact phase shifter based on highly anisotropic liquid crystals for microwave frequency

A compact microwave phase shifter was designed and fabricated using highly anisotropic liquid crystals (LCs). It comprises a thin LC layer between a ground plane and a directly coupled and inverted microstrip line. The proposed folding configuration is beneficial for size reduction. Both simulation and experimental results confirm the compact size devices with reasonably good performance.