Conductor-backed Coplanar Waveguide Research Articles

Modeling and Analytical Description of Parasitic Probe Effects in Measurements of Conductor-Backed Coplanar Waveguides

Abstract. On-wafer measurements are of fundamental importance to the characterization of active and passive devices at millimetre-wave frequencies. They have been commonly known to be ambitious and challenging due to the occurrence of parasitic effects originating from probes, multimode propagation, crosstalk between adjacent structures and radiation. While a lot of investigations have been performed for conventional coplanar waveguides (CPW) measured on ceramic chucks, the parasitic effects occuring in conductor-backed CPWs (CB-CPWs) have not been fully understood yet. Therefore, this paper presents a thorough study for CB-CPWs based on electromagnetic simulations. Additionally, this paper proposes an analytical description accounting for the probe geometries to predict the occurrence of resonance effects due to the propagation of the parallel-plate-line (PPL) mode. For the first time, a new analytical description including the effects of the probe geometries is presented and validated by both measurements and simulations.

A novel S-shaped frequency and pattern reconfigurable patch antenna for 4G LTE, WLAN/Wi-Max application

PurposeIn wireless communication system, use of multiple antennas for different requirements of system will increase the system complexity. However, reconfigurable antenna is maximizing the connectivity to cover different wireless services that operate different frequency range. Pattern reconfigurable antenna can improve security, avoid noise and save energy. Due to their compactness and better performance at different applications, reconfigurable antennas are very popular among the researchers. The purpose of this work, is to propose a novel design of S-shaped antenna with frequency and pattern diversity. The pattern and frequency reconfiguration are controlled via ON/OFF states of the PIN diode.Design/methodology/approachThe geometrical structure of the proposed antenna dimension is 18 × 18 × 0.787 mm3 with εr = 2.2 dielectric constant. Three S-shaped patches are connected to a ring patch through PIN diodes. The approximate circumference of ring patch is 18.84 mm and length of patch is 5 mm, so approximate length of radiating patch is 14.42 mm and effective dielectric constant is 1.93. Conductor backed coplanar waveguide (CPW) is used for feeding. The proposed antenna is designed and simulated on CST microwave studio and fabricated using photolithography process. Measurements have been done in anechoic chamber.FindingsAntenna shows the dual band operation at 2.1 and 3.4 GHz frequency. The first band remains constant at 2.1 GHz resonant frequency and 200–400 MHz impedance bandwidth. Second band is switched at seven different resonant frequencies as 3.14, 3.45, 3.46, 3.68, 3.69, 3.83 and 3.86 GHz with switching of the diodes. The −10 dB bandwidth is more than 1.4 GHz.Research limitations/implicationsPattern reconfigurability can be achieved using mechanical movement of antenna easily but it is not a reliable approach for planar antennas. Electronic switching method is used in proposed antenna. Antenna size is very small so fabrication is very crucial task. Measured results are deviated from simulation results due to fabrication error and effect of leads of diodes, connecting wires and battery.Practical implicationsThe reconfiguration of the proposed antenna is controlled via ON/OFF states of the three PIN diodes. The lower band of 2.1 GHz is fixed, while second band is switched at five different resonant frequencies as 3.27, 3.41, 3.45, 3.55 and 3.88 GHz, with switching of the PIN diodes with all state of diodes and exhibit pattern reconfigurability at 2.1 GHz frequency. At second band center frequency is significantly changed with state of diodes and at 3.4 GHz pattern is also changed with state of diodes, hence antenna exhibits frequency and pattern reconfigurability.Originality/valueA novel design of pattern and frequency reconfigurable antenna is proposed. Here, work is divided into two parts: first is frequency reconfiguration and second is radiation pattern reconfiguration. PIN diodes as switch are used to select the frequency band and reconfigure the radiation pattern. This proposed antenna design is novel dual band frequency and pattern reconfigurable antenna. It resonates at two distinct frequencies, i.e. 2.1 and 3.4 GHz, and has a pattern tilt from 0° to 355°. The conductor backed CPW feed technique is used for impedance matching.

Design process for dual coplanar waveguide directional couplers for power transmission

In this paper, a design process for power directional couplers using dual conductor-backed coplanar waveguides (CBCPW), is presented. The proposed methodology is applied to the design of a 50 Ω impedance coupler with 10 dB coupling factor for a central frequency of 2.5 GHz. The resulting coupler is validated through simulation by obtaining its dispersion parameters using ANSYS High Frequency Structure Simulator (HFSS). From the analysis of the return loss, insertion loss and coupling factor, in a range of 1 to 4 GHz, it was found that the coupling factor complies with the design specification for frequencies from 2 to 3 GHz, with insertion losses between -1 and -2 dB around the center frequency and return losses of -15 dB.

Novel Calibration Method for the Asymmetric Probing in the Near-Field Measurement With a Dual Probe

Dual probe is capable of simultaneously measuring electric and magnetic fields in the same position, given that perfectly symmetric design is realized on the transmission paths connecting the detection loop and the probe outputs. For general application, a calibration method for the asymmetric probing in near-field measurement with the dual probe is presented, in order to deal with the failure of the traditional calibration due to the asymmetric transmissions in both paths. The asymmetric probing measurement is modeled, and then the proposed calibration to eliminate the asymmetry is further derived based on two independent measurements at two directions (0° and 90°) between the probe and the microstrip line providing a known electromagnetic field at the surface. The calibration method is demonstrated with two kinds of dual probes of different coupling structure. The proposed calibration is validated by introducing the asymmetry to the probing process in the measurement of the standing wave along a conductor-backed coplanar waveguide transmission line.

Coplanar waveguides on BCB measured up to 760 GHz

The integrated THz pattern over any MMIC appears to be a good opportunity to enclose calibration kit suitable for accurate measurements. An original technology based on polymer has been developed. Sub-millimeter single-mode conductor-backed coplanar waveguides using benzocyclobutene polymer and interconnecting via between ground planes are processed and measured up to 760 GHz. The experimental performances show good agreement with analytical and numerical modeling. A two-tier Thru-Reflect-Line correction and a square root of Thru de-embedding are applied to extract the attenuation factor of about 3 dB/mm at 600 GHz, the relative phase velocity to light of about 0.716 and the characteristic impedance around 50 Ω. The fundamental propagating mode remains unique in this wide frequency range, enabling this technological to be integrated over existing circuit for THz applications. The loss performance of the coplanar waveguide ranges in the state-of-the-art opening the road for fully integrated THz circuits.

A Nanoplasmonic Branchline Coupler for Subwavelength Wireless Networks

This article presents the new nanoplasmonic branchline coupler (BLC) by using an edge coupled coplanar waveguide (CPW) with a finite length suspended backed conductor. The proposed coupler is designed by using the theoretical transmission line (TL) method, which is established based on the basic characteristics of the related CPW structures. For this purpose, the normalized propagation constant, propagation length, and characteristic impedance of the conductor backed coplanar waveguide (CBCPW) structure are studied and analyzed by applying a fullwave analysis using CAD simulation software tool CST microwave studio suite. Mainly, the coupling coefficient of the BLC can be controlled by changing the length of the backed conductor. In this article, the BLC is designed and analyzed by using a finite length backed conductor based on the theoretical TL method at a 3-dB coupling coefficient. This newly designed coupler can operate at two arbitrary optical frequency bands (O-band and L-band). Hence, it allows us to exchange many other couplers with their narrow bandwidths using this branchline coupler for subwavelength nanoscale wireless network applications and photonic integrated circuits (PICs).

Mode-Selective Transmission Line—Part II: Excitation Scheme and Experimental Verification

In Part I of this two-part work, we have presented the theoretical foundation and physical mechanism of the mode-selective transmission line (MSTL). This part is devoted to its excitation scheme, practical transition design, and experimental verification. The MSTL excitation is first explained by comparison with a conductor-backed coplanar waveguide (CBCPW). To produce the specific mode excitation, an ultrabroadband transition between CBCPW and MSTL is proposed. It has a tapered structure operating as a tapered-mode coupler, which supports smooth evolution from the fixed CPW mode of CBCPW to the frequency-dependent dominant mode of MSTL. This modal evolution along the transition is analytically treated based on a local normal mode theory. Couplings between the local normal modes are negligible as a result of gradual tapering, thereby effectively suppressing higher order modes in MSTL and sustaining a mode purity over an ultrabroad frequency range. For experimental demonstration purposes, back-to-back CBCPW-to-MSTL transition circuits are physically realized. The measured results are in agreement with the prediction, showing a return loss of 15 dB from 3 to 109 GHz; the single transition introduces a relatively low insertion loss of 1.84 dB at 100 GHz. The propagation characteristics of MSTL are also extracted from the measured S-parameters, which provides an excellent validation of the proposed structure.

A compact modified wideband antenna with CBCPW, stubline and notch-staircase for breast cancer microwave imaging application

Controlling desired frequency without affecting physical size of wideband microstrip antenna is a challenging issue especially for breast cancer microwave imaging application. This paper presents a solution for improving the lower frequency operation and achieving wider frequency bandwidth by introducing Conductor Backed Coplanar Waveguide (CBCPW) feeding and adopting stubline with notch-staircase shape on radiating patch design.The dimension of the proposed design is 43 × 43 × 1.6 mm3 which reducing 23% in size compared to the antenna without CBCPW feeding. The antenna operates from 1.85 to 8.37 GHz with 127.6% of fractional bandwidth. It showed a good reflection coefficient with mostly below −15 dB and gain varies from 1 dBi to 5.27 dBi across the impedance bandwidth. The proposed antenna is also experimentally verified, achieving acceptable agreement between the simulation and measurement results. In addition, time domain performance such as input and received signal response and group delay are also observed for the proposed antenna. Owing to its compact size, wideband frequency operation and other acceptable performance, the proposed antenna is suitable for breast tumor imaging implementation.

Finite Ground CB-CPW Bandpass Filter using Vertically Installed Coupled Open-ended Stubs

In this paper, a conductor backed coplanar waveguide (CB-CPW) 3rd order bandpass filter is designed using coupled open-ended stub resonator placed vertically to the signal line. Vertically loaded open ended stubs are designed at quarter wavelength so as to behave like a short circuit at the input terminal thus giving a band-accepted response with lesser metallic area or minimum size. Four such coupled open ended resonators are placed in series and also in closely manner to provide greater field confinement of the proposed bandpass filter. The bandpass filter is designed for a center frequency of 2.5 GHz with FBW of 97.89%, insertion loss of <0.5dB, rising and falling edge selectivity of 30.75 dB/GHz and 27.01dB/GHz respectively with a wide stopband of around 4GHz after the desired passband. Further to validate the design technique six such resonators are placed to obtain 5th order bandpass filter.

A Low-Profile Planar Surface-Wave Antenna With Metasurface for Endfire Radiation

A low-profile planar surface-wave antenna with metasurface is proposed for endfire radiation. The antenna has the advantages of low profile, high gain, and wide bandwidth of endfire radiation. The surface-wave structure is based on a substrate integrated waveguide (SIW) structure, which can be considered as a laterally-bounded conductor-backed coplanar waveguide (CPW) with a metasurface that is made of periodic staggered patches. The propagation properties are analyzed with a magnetic-field integral equation method. With the analysis, it is found that the structure supports an improper leaky mode and a proper mode that behaves as a surface-wave mode in lower frequency range. With the surface-wave mode, an endfire surface-wave antenna is designed. A prototype of the antenna is fabricated and measured. The measurement results show that the antenna provides a 3 dB gain bandwidth of 32%, with the gain varying from 12.3 to 15.3 dBi in the operation band from 9.6 o 13.6 GHz at a fixed direction close to endfire.

Compact, Isolation Enhanced, Band-Notched SWB–MIMO Antenna Suited for Wireless Personal Communications

Herein, a Conductor Backed Co-Planar Waveguide fed, compact, slotted Multiple–Input–Multiple–Output or MIMO antenna having Super Wideband (SWB) response and tunable band-notching feature is presented. In addition, an improved method for cut-off frequency prediction of the antenna is formulated. A super wide frequency response from 01.21 to 34.0 GHz and notches at Wireless Local Area Networks or WLAN bands (04.92–05.83 GHz) and Worldwide Inter-operability for Microwave Access or WiMAX bands (03.30 GHz–03.70 GHz) are obtained. By fine tuning the dimensions of the Split Ring Resonator Structure introduced in the radiating element, band-notched characteristics centered at 05.50 GHz WLAN band is obtained. A second band notch having centre frequency at 03.50 GHz for the WiMAX band is obtained by the introduction of a Spiral Microstrip Defected Structure in the feeding segment. The antenna is 20 × 36 × 1 mm3 in dimension. Acceptable gain all through the functional bandwidth, excepting the notched bands makes the MIMO antenna a novel contender for SWB operations particularly for Wireless Personal Communications.

Ultralow-Loss Substrate-Integrated Waveguides in Glass-Based Substrates for Millimeter-Wave Applications

This letter, for the first time, presents low-loss substrate-integrated waveguides (SIWs) in fused silica and borosilicate glass and a comparison of their performance with various organic-based low-loss substrates for millimeter-wave applications. Utilizing ring resonators designed for frequencies in the 5G New Radio (NR) n257 band (26.5–29.5 GHz), this letter begins with the determination of the dielectric constant of fused silica to model SIWs. This letter also introduces the designs of SIWs that are fed by conductor-backed coplanar waveguides and discusses the fabrication and measurement results with deembedding analysis. In addition to the excellent correlation between simulations and measurements, the characterization results show more than $2\times $ reduction in the insertion loss compared to those of low-loss organic-based SIWs at the 28-GHz frequency band.

A Microwave Sensor With Operating Band Selection to Detect Rotation and Proximity in the Rapid Prototyping Industry

This article presents a novel sensor for detecting and measuring angular rotation and proximity, intended for rapid prototyping machines. The sensor is based on a complementary split-ring resonator (CSRR) driven by a conductor-backed coplanar waveguide (CBCPW). The sensor has a planar topology, which makes it simple and cost-effective to produce and accurate in measuring both physical quantities. The sensor has two components, a rotor and a stator: the first of these (the CSRR) can rotate around its axis and translate along the plane normal to the ground of the CBCPW. A detailed theoretical and numerical analysis, along with a circuit model, of the unique sensor design is presented. The proposed sensor exhibits linear response for measuring angular rotation and proximity in the range of 30°-60° and 0-200 μm, respectively. Another distinctive feature of the rotation and proximity sensor is the wide frequency band of applicability, which is an integral part of its novel design and is implemented through various dielectric material loadings on the CSRR. In the prototype of the proposed device, the stator (CBCPW) is fabricated on a 0.508-mm-thick RF-35 substrate, whereas the CSRR-based rotor is fabricated on TLY-5 and RF-35 substrates. The angular rotation, proximity, operating band selection, and sensitivity are measured using a vector network analyzer and are found to be good matches to the simulated and theoretical results.

Characteristics of Coplanar Waveguide of Small Cross Section on BCB with Coplanar Ground to Conductor-Backed Plane Interconnection

Conductor-backed coplanar waveguide on 30-μm-thick BCB polymer is fabricated. In order to eliminate unwanted propagation modes for these lines designed for frequencies up to 1 THz, electroplated vias interconnect each coplanar ground to the backed conductor. Transmission line properties are extracted here up to 67 GHz, showing a characteristic impedance of about 50 Ω, but with high conduction losses for this frequency range due to the thin metal layer used. Thru-reflect-line correction and a de-embedding with electrical circuit of accesses are applied to extract line properties. The comparison with a coplanar waveguide model leads to a relative permittivity of 2.676 for the BCB in this low-frequency range.

Compact transition from CBCPW to substrate integrated suspended line (SISL) for operation up to 46 GHz

AbstractA compact transition between conductor-backed coplanar waveguide (CBCPW) and substrate integrated suspended line (SISL) is presented. Compared to the reported transitions from CBCPW to SISL, performance and compactness are improved. For demonstration purpose, a multilayer transition is designed and fabricated for operation up to 46 GHz. Experimental results, based on an electronic calibration and thru–reflect–line calibration allowing measurement in the 0.01–50 GHz frequency range, demonstrate an insertion loss of 0.59 ± 0.51 dB with a return loss of better than 10 dB in the 10 MHz to 46 GHz frequency range.

Simultaneous Measurement of Electric and Magnetic Fields With a Dual Probe for Efficient Near-Field Scanning

A near-field scanning is usually time-consuming to map the electromagnetic field along the surface of a device. In this communication, a dual probe is proposed with a U-shaped loop to sense radio frequency (RF) magnetic and electric fields simultaneously, so that the one-time scanning by the dual probe can replace the two-time scanning by single-detector probes. Different from the traditional near-field scanning by using a single-detector probe and spectrum analyzer, the proposed scanning can be achieved by the two-output probe and a two-port vector network analyzer connecting to the probe. The efficient near-field scanning measurements of the electric and magnetic field on a conductor-backed coplanar waveguide transmission line and an RF power divider by using the dual probe are in agreement with those by using two single-detector probes.

Application of Aerosol Jet 3-D Printing With Conductive and Nonconductive Inks for Manufacturing mm-Wave Circuits

In this paper, an application of aerosol jet 3-D printing with conductive and nonconductive inks for the realization of millimeter (mm)-wave circuits well above 30 GHz is presented and investigated. The Optomec 5X aerosol jet 3-D printing system is used together with polyimide (PI) and silver inks to fully-additive manufacture various microstrip circuits. A section of microstrip transmission line with a transition to a via-less conductor-backed coplanar waveguide was designed together with a T-junction and a branch-line coupler. These circuits were designed to operate within the Ka and V frequency bands. The measured thickness of the PI dielectric substrate is $20.7 \pm 1.35~\mu \text{m}$ , while the silver traces are $2.6 \pm 1.35 ~\mu \text{m}$ . A section of the transmission line with the developed transitions was measured up to the W-band, exhibiting a total loss of 0.65 dB/mm at 100 GHz. The T-junction power divider yielded a total loss at its center frequency of 34 GHz of 0.55 dB. The 3-dB branch-line coupler yielded a loss at its center frequency at 42 GHz of 1.1 dB. The experimental results demonstrate the application of this approach for fast and high-resolution mm-wave circuit fabrication.

Sequential Buildup of Broadband Equivalent Circuit Model for Low-Cost SMA Connectors

This paper presents a measurement-based technique for equivalent circuit modeling of various types of SubMiniature version A (SMA) connectors. The 50- $\mathbf {\Omega }$ microstrip (MS) lines and conductor-backed coplanar waveguides are designed on high-frequency laminates. Three types of low-cost SMA connectors are mounted on the manufactured transmission lines. The presented technique for sequential buildup of the equivalent circuit model generates an equivalent circuit model of the SMA connector composed of ideal transmission lines and ideal lumped elements suitable for implementation in various circuit simulators. The SMA connector modeling is performed up to 12 GHz. The accuracy of the developed models is assessed by examination of the obtained $S$ -parameter results using the feature selective validation.

Width‐varying conductor‐backed coplanar waveguide‐based low‐pass filter with a constant signal trace to adjacent grounds separation

In this study, the authors introduce a new and systematic procedure for the design and optimisation of a conductor-backed coplanar waveguide low-pass filter (LPF). The width of the centre conductor (i.e. signal trace) is modelled in a truncated Fourier series, whereas the gap to the adjacent grounds is maintained constant relative to the width variation. Transmission lines theory is adopted to model the LPF and establish an optimisation setup. Three optimisation techniques; namely, trust-region-reflective algorithm, symbiotic organism search, and genetic algorithm are investigated to minimise the developed bound-constrained non-linear objective function. To verify the proposed procedure, an LPF with a cutoff frequency of 2 GHz is optimised, simulated, and measured. The transmission parameter in the passband is found to be in the range -0.3 ± 0.1 dB, and better than -30 dB in the stopband.

High Selective Balanced Bandpass Filters Using End-Connected Conductor-Backed Coplanar Waveguide

In this paper, an end-connected conductor-backed coplanar waveguide (CBCPW) balanced bandpass filter and a size reduction one with adjustable multiple transmission zeros have been developed by using the separated electric and magnetic coupling, and quarter-wavelength short-circuited stubs. The differential mode (DM) and the common mode (CM) equivalent transmission line circuits have been modeled and verified, and the DM/CM parts can be designed individually. The proposed CBCPW balanced bandpass filters have been fabricated and measured, and their advantages of multiple transmission zeros, high out-of-band suppression, and high common mode suppression characteristics have been demonstrated.