Suspended Microstrip Line Research Articles

Broadband flip‐suspended‐microstrip transition for millimeter‐wave MMIC package

AbstractIn this letter, a novel millimeter‐wave chip packaging method based on flip‐suspended‐microstrip technology is proposed. The flip‐suspended‐microstrip contains a waveguide probe, a suspended microstrip line, input and output matching lines, and a terminal pad. The waveguide probe realizes energy coupling from the rectangular waveguide, and the terminal pad above the signal pad of chip achieves power transmission via electronic contact. Thus, the bonding wires which will bring parasitic inductance at high frequencies are avoided. To validate the proposed packaging method, back‐to‐back modules with coplanar waveguide/low noise amplifier were fabricated. The measured insertion loss of the back‐to‐back transition with a 1.75‐mm‐long coplanar waveguide is 2.6–4.2 dB over the entire D‐band, while the packaging loss of the low noise amplifier module with the back‐to‐back transition is less than 2.2 dB at 120–170 GHz, which indicate that the proposed broadband transition is feasible for millimeter‐wave chip packaging.

A study of substrate effect on dispersion characteristics of suspended microstrip line

In this paper suspended microstrip lines are studied for their dispersion characteristics using Galerkin Technique in Spectral Domain. Basis functions for the unknown strip current are chosen according to the geometry of the structure of the line. For theoretical analysis, Fourier transform of the basic functions from space domain to spectral domain are considered. The line is analyzed for dispersion characteristics in the X-band corresponding to different values of the thickness of the suspended dielectric substrate and also studied for the different values of the relative permittivity of the substrate.

Design of a Novel Broadband Microstrip Line-Suspended Microstrip Line Transition Circuit

Based on the application requirements of the suspended microstrip circuit, a novel broadband microstrip line-suspended microstrip line transition circuit is designed in this paper. The transition structure uses “V-grooved” ground structure to realize the transition from microstrip line to suspended microstrip line in the direction of electric field, and uses gradient signal line for impedance matching to expand the bandwidth. The final simulation results show that the echo loss of the structure is better than 15 dB and the insertion loss is less than 0.165 dB in the frequency range of 0-40 GHz, and the sensitivity of circuit performance to circuit size is low. This design combines the ultra-low loss suspension line with the most commonly used microstrip line circuit, and has the advantages of broadband, low insertion loss, easy processing and compact structure. It improves the application scope of the suspension microstrip circuit and can be better integrated with other circuits or systems.

Design of Multi-Layered Suspended Microstrip Line Type Antenna-Filter Using Patch Antenna and λ/2 Resonator

Design of Multi-Layered Suspended Microstrip Line Type Antenna-Filter Using Patch Antenna and λ/2 Resonator

Comparative investigation of reflection and band gap properties of finite periodic wideband artificial magnetic conductor surfaces for microwave circuits applications in X‐band

In this study, novel designs of artificial magnetic conductors (AMCs) for wideband operation are introduced. By using two techniques of the planar parasitic patches and stacked elements, AMC unit cells are achieved. The first design of the AMC unit cell is composed of four symmetric patches with two arms, which are coupled to a rhombic patch at the center. The second AMC design is configured of two stacked patches, which are connected together through the air spacing. The first and second AMC designs operate at the frequencies of 10.15 and 10.65 GHz with ±90° reflection phase bandwidths of 8 to 12.38 GHz (43.15%) and 8 to 12.90 GHz (46%), respectively, for X-band operation. The proposed AMC unit cells present prominent features such as symmetric structures and wide bandwidths with distinct capabilities. To achieve an accurate evaluation of AMC performance, the reflection and band gap properties of the finite periodic AMC surfaces are investigated. The finite periodic arrays of the AMC reflectors are implemented and tested. The measured results show that they can be applied for wideband applications in microwave circuits and low profile antennas. The 15 × 15 AMC planar and stacked arrays under normal incidence operate at the frequencies of 9.89 and 10.25 GHz with the measured bandwidths of 7.85 to 12.02 GHz and 7.77 to 12.58 GHz, respectively. In addition, to identify the band gap properties of the finite periodic planar and stacked AMC arrays, the method of the suspended microstrip line is applied. For this purpose, the measured band gaps of the planar and stacked arrays include the ranges of 8.12 to 12.63 GHz and 7.81 to 12.10 GHz below −20 dB, respectively.

1.1 THz tenth harmonic mixer based on planar GaAs Schottky diode

Here, the tenth harmonic mixing technology based on planar GaAs Schottky diode is first proposed for the 1.1 terahertz (THz) frequency conversion module. The first higher order mode cut-off frequency of the suspended microstrip line has been investigated to determine the appropriate cross-sectional dimension of transmission line shield cavity in the radio frequency (RF) circuit portion. The height of shield cavity of transmission line is designed to be discontinuous in order to facilitate the assembly of the diode. A modelling approach combining field and circuit is used to achieve joint simulation of linear passive structure and diode non-linear characteristics. The simulation results show that the frequency conversion loss of this mixer is <55 dB in the RF frequency range of 1.03–1.154 THz, and the best frequency conversion loss is 50 dB at RF of 1.098 THz.

Isolation enhanced circularly polarized patch antenna array using modified electric‐field‐coupled resonator

A modified electric-field-coupled (MELC) resonator featuring negative permittivity is proposed to enhance the inter-element isolation of a circularly polarized (CP) patch antenna array operated at Chinese compass navigation satellite system (CNSS) downlink band. The resonator comprises two capacitive gaps and a common inductive strip connected to the ground plane by two metal vias. A suspended microstrip line excitation is employed to efficiently design and investigate the MELC resonator whose constitutive parameters are subsequently extracted. A dual-element CNSS antenna array has been prototyped and measured. The experimental results demonstrate that under the assistance of the proposed MELC resonator, a mutual coupling reduction of 15 dB has been achieved while maintaining good impedance matching and CP radiation performance. Details of the design considerations along with simulation and measurement results are presented and discussed.

The LPF with improved stopband response designed for wideband microwave detectors

To achieve an improved stopband response including expanded stopband width, increased rejection level, and a smooth S11 phase response, a lowpass filter (LPF) is proposed based on the suspended microstrip line with naturally high characteristic impedance and the radial stub with intrinsic transmission zero. The usually unmentioned phase response, are critical to obtaining a wide and flat operating band for the microwave detector, since a smooth phase response exerts small load effects to the diode. As a demonstration, a detector employing the LPF is fabricated and measured. The measured results show that a wide operating band from 1.8 to 13.5 GHz with flat detection outputs of ripple less than 1 dB is obtained for the detector, which coincides with the smooth-phase range of the LPF.

A 220 GHz subharmonic mixer based on schottky diodes with an accurate terahertz diode model

ABSTRACTThis article introduces the design process of a 220 GHz subharmonic mixer with low conversion loss, which is comprised of a pair of anti‐parallel Schottky diodes (SBD). For terahertz circuits, the wavelength of the electromagnetic (EM) wave is very close to the size of devices, which results in complicated parasitic effects. This will leads to a very limited optimization space for circuits design when matching the impedance. To solve this problem, we developed the precise 3D EM planar SBD model and the field‐circuit co‐simulation method to design this terahertz mixer. The diodes are mounted on the quartz‐based suspended microstrip line. The measured results show that the single side band conversion loss is less than 12 dB during radio frequency (RF) range from 211 to 226 GHz and the minimum loss is about 5.9 dB. With the intermediate frequency fixed at 1 GHz, the conversion loss varies from 8 dB to 11.2 dB over the RF bandwidth of 211 to 221 GHz. The mixer can be applied in heterodyne receivers of terahertz systems. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2311–2316, 2016

Design of LPF using suspended substrate microstrip lines as high‐Z sections for stopband extension

ABSTRACTThis article introduces the use of suspended substrate microstrip lines (SSMLs) as high‐Z sections in the design of lowpass filters (LPFs) to extend the stopband. The SSMLs are formed by etching slots on the backside of microstrip lines and placing the substrate on an aluminum base with grooves that cover these slots. The higher characteristic impedance property of SSMLs brings about not only shorter length for high‐Z lines but also a larger high‐to‐low impedance ratio, thus deepening the stopband suppression and shifting the spurious passband away. As a demonstration, a wide stopband LPF combining this structure with hammer‐shaped stubs is designed, fabricated, and measured. The 20 dB stopband is obtained from 1.45 to 11.77 GHz. Compared with reported LPFs, this shows the widest fractional bandwidth (FBW) of 156% without sacrificing other performances. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1204–1207, 2016

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.

Modeling and characterization of spiral resonators embedded in suspended microstrip line for application in low‐loss diplexer

ABSTRACTThis article presents the design and realization of anovel, low‐loss, compact diplexer providing high selectivity and verygood separation between very narrow spaced working channels for application in the ESEO satellite transceiver. The diplexer is based on spiral resonators (SR) embedded in the suspended microstrip line and forming band‐stop filter structures. For design purpose, the equivalent‐circuit model of the SR resonator embedded in microstrip line is derived, analyzed, and verified. The influence of the model parameters on S11 and S21 characteristics has been studied and discussed. The double stage filter with embedded SR resonators has been described. A novel method is proposed to precisely control the filter selectivity, bandwidth, and the position of S11 minimum. The filter has been applied in the diplexer design. The measured performance of the manufactured diplexer prototype exhibits good properties and good agreement with the simulation results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:131–135, 2014

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

Assembly materials like 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 right 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 wave guides or 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. In- and outlets allow filling the cavity with fluids after an initial S-parameter measurement of line properties (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.

Finite Element Approach of Shielded, Suspended and Inverted Microstrip Lines

In this paper, we present finite element method (FEM) to investigate the electromagnetic analysis of two-dimensional (2D) shielded, suspended and inverted microstrip lines for microwave applications. In the proposed method, we specifically determine the values of capacitance per unit length, inductance per unit length, and characteristic impedance of the microstrip lines. Extensive simulation results are presented and some comparative results are given with other methods and found them to be in excellent agreement. We extend the analysis by designing our new model of shielded, inverted microstrip lines and compared it with shielded, suspended microstrip lines; we found them to be very close. Also, we determine the quasi-TEM spectral for the potential distribution of these microstrip lines.

Finite Element Approach of Shielded Suspended and Inverted Microstrip Lines

Finite Element Approach of Shielded Suspended and Inverted Microstrip Lines

Design of High Impedance Electromagnetic Surfaces for Mutual Coupling Reduction in Patch Antenna Array.

A compact planar meander-bridge high impedance electromagnetic structure (MBHIES) was designed and its bandgap characteristics, mutual coupling reduction abilities were studied and compared in detail. Several parametric analyses were performed to obtain optimized design values and the transmission responses were calculated through the suspended microstrip line and waveguide simulation methods. The achieved bandgap is 2.3 GHz (2.55–4.85 GHz) with −61 dB minimum transmission coefficient level at the center frequency of 3.6 GHz. To see the effectiveness, the proposed design was inserted between a microstrip patch antenna array which operates at 3.8 GHz and whose operating bandwidth falls within the MBHIES bandgap. The surface wave suppression phenomenon was analyzed and simulated results are verified by measuring the fabricated prototypes, both are in good agreement. The configuration reduced the mutual coupling by 20.69 dB in simulation and 19.18 dB in measurement, without affecting the radiation characteristics of the array but increasing the gain slightly.

Printed Frequency Beam-Scanning Antenna With Flat Gain and Low Sidelobe Levels

A frequency beam-scanning antenna with backfire-to-endfire beam-steering capability is proposed and investigated. This antenna is with printed planar structure that consists of a low-loss slow-wave printed meander line based on the even-mode bilateral broadside-coupled suspended microstrip line (BSML). The propagation properties of the meander-line unit and its principles for frequency-scanning applications are studied extensively. This printed antenna achieves the measured beam scanning of -27.5° to 46° with the frequency sensitivity of 43.24°/GHz and a maximum gain of 15.5 dBi. The antenna exhibits flat gain of more than 13 dBi in the whole frequency range from 8.9 to 10.6 GHz. The sidelobe levels are near 20 dB. The design flexibility of this kind of antenna is shown.

A NOVEL COMPACT SPLIT RING SLOTTED ELECTROMAGNETIC BANDGAP STRUCTURE FOR MICROSTRIP PATCH ANTENNA PERFORMANCE ENHANCEMENT

A novel design of an electromagnetic bandgap (EBG) structure based on the uniplanar compact EBG (UCEBG) concept is proposed in this paper. The structure is realized by inserting split- ring slots inside two reversely connected rectangular patches, which is known as a split-ring slotted electromagnetic bandgap (SRS-EBG) structure. The bandgap properties of the EBG structure are examined by the suspended microstrip line and flnite element methods (FEM). The achieved bandgaps have widths of 4.3 (59.31%) and 5.16GHz (38.88%), which are centered at 7 and 13GHz, respectively. The SRS-EBG is applied to enhance the performance of a single-element microstrip patch antenna (at 7GHz) and a two-element array (at 13GHz) conflguration. A wider bandwidth is obtained with a better re∞ection coe-cient level for the single element antenna; a reduction in mutual coupling of more than 20.57dB is obtained for the array design. In both cases, the gain and radiation characteristics are improved. The results are verifled by measuring the fabricated lab prototype, and a comparison with the computed results showed good agreement.

Development of wideband low-loss directional coupler with suspended stripline and microstrip line

A novel K/Ka band directional coupler with low insertion loss over a wideband is proposed. The design combines the advantages of suspended stripline (SS) and microstrip line (MS). This novel directional coupler is suitable for high output power detection and can be seamlessly integrated with low-loss SS power combiners and MS circuits. The measured insertion loss is less than 0.2 dB, coupling is within 20.5–22 dB with more than 15 dB directivity, and return loss of all ports is better than 15 dB over 20–30 GHz.

Wideband 3 dB Branch Line Coupler Based on $\lambda/4$ Open Circuited Coupled Lines

This letter introduces a new 3 dB branch line coupler for wideband applications. The wideband matching property of the coupler with four λ/4 open circuited coupled lines is briefly derived. The coupler with a suspended microstrip and microstrip line structures has been simulated with HFSS and fabricated. Measurement results show insertion loss better than 3.6 dB with a power imbalance of 0.5 dB; return loss and isolation characteristics both better than 20 dB over 49% fractional bandwidth.