Substrate Integrated Coaxial Line Research Articles

A Circularly Polarized Complementary Antenna with Substrate Integrated Coaxial Line Feed for X-Band Applications

This work presents a design for a complementary antenna with circular polarization that has a wide operating bandwidth, stable broadside radiation, and stable gain for X-band applications. The proposed antenna consists of an irregular loop and a parasitic electric dipole, which work together to produce equivalent radiation from the magnetic and electric dipoles. By arranging the dipole and the loop in a specific geometry, this antenna effectively generates circularly polarized wave propagation. A substrate integrated coaxial line (SICL) is applied to feed the antenna through an aperture cutting on the ground. The proposed antenna achieves a wide axial ratio (AR) and impedance bandwidths of 27.4% (from 8.5 to 11.22 GHz, for the AR ≤ 3 dB) and 39.6% (from 7.5 to 11.2 GHz, for the reflection coefficient ≤ −10 dB), respectively. Moreover, the antenna maintains a stable broadside radiation pattern across the operating bandwidth, with an average gain of 10 dBic. This proposed antenna design is competitive for X-band wireless communications.

Design and realization of a compact substrate integrated coaxial line butler matrix for beamforming applications

Abstract This article presents the modeling and realization of a compact substrate integrated coaxial line (SICL) based butler matrix operating at 5 GHz for beam-forming applications. The proposed 4 × 4 butler matrix is developed using SICL-based hybrid coupler, crossover, and phase shifter. A compact 90∘ coupler comprising of center tapped unequal stubs is designed to enhance the size reduction as well as to extend the out of band rejection. Wideband SICL-based crossover operating from DC to 10 GHz is conceived for the proposed butler matrix using a plated through hole as transition. The SICL crossover features very high measured isolation of 65 dB owing to the reduction in coupling between the two signal paths within a lateral footprint of only 0.034 $\lambda_g^2$ . A meandered SICL-based line is used in order to provide the necessary 45∘ and 0∘ phase shift to realize the butler matrix. The fully shielded and self-packaged compact 4 × 4 SICL-based butler matrix is fabricated and experimentally validated to operate at 5 GHz.

Novel Substrate-Integrated Coaxial Line Phase Inverter and Magic-T

Novel Substrate-Integrated Coaxial Line Phase Inverter and Magic-T

Compact Broadband Substrate-Integrated Coaxial Line 2-D Beamforming Network and Its Multibeam Array Antenna Applications

Compact Broadband Substrate-Integrated Coaxial Line 2-D Beamforming Network and Its Multibeam Array Antenna Applications

Design of a Dual-Band Planar Sleeve Monopole Antenna With the Substrate-Integrated Coaxial Line Technology

Design of a Dual-Band Planar Sleeve Monopole Antenna With the Substrate-Integrated Coaxial Line Technology

A low-cost 24 GHz single-stage amplifier using SICL based stepped impedance matching network

This paper presents a single-stage amplifier using substrate-integrated coaxial line (SICL) technology. It is implemented with a low-cost PCB technique at 23.35–24.05 GHz. The size of the proposed amplifier is 4.9λg×1.1λg where λg is the guided wavelength at the center frequency. In this circuit, a SICL-based bias-tee network is designed where the mounting pads are introduced for the integration of the components, such as transistor and capacitor. Next, with the help of de-embedding techniques, the input and output matching networks are designed in the SICL environment at 24 GHz. The proposed amplifier circuit exhibits 9.2 dB of peak gain with less than 1 dB of gain ripple and more than 10 dB of input/output return losses in the operating frequency band of 23.35–24.05 GHz. Moreover, the elementary blocks of the amplifier are presented in the circuit. Based on the appropriate modeling of the amplifier’s elementary blocks, the simulated and measured results are in good agreement.

Miniaturized Via-Free Magnetoelectric Dipole Antenna Fed by Substrate-Integrated Coaxial Line on Reactive Impedance Surface

Miniaturized Via-Free Magnetoelectric Dipole Antenna Fed by Substrate-Integrated Coaxial Line on Reactive Impedance Surface

A low‐cost broadband millimeter‐wave bias tee network using SICL technology

AbstractThis article presents a substrate integrated coaxial line (SICL)‐based low‐cost bias tee network operating in K‐ and Ka‐band (20–29 GHz). A butterfly stub is introduced in the direct current (DC) circuit path for the radiofrequency (RF) isolation. A single‐layer ceramic capacitor is used along the RF mainline to provide the DC isolation. The size of the proposed circuit is , where is the guided wavelength at the center frequency of 24.5 GHz. The proposed design exhibits 0.5–1 dB insertion loss in 20–25 GHz and 1–2 dB insertion loss in 25–29 GHz, along with more than 30 dB isolation between RF and DC circuits with good impedance matching. The isolation is improved by adding a series of butterfly stubs. Moreover, a design method for realizing a mounting pad to connect the surface‐mount device (SMD) capacitor with the SICL line is proposed. The proposed method helps integrate SMD component in the SICL environment. The parasitic effects of the pad are analyzed with the help of an equivalent circuit. This circuit is most suitable for 5G FR2 (millimeter‐wave) band application.

Novel circulator design using substrate integrated coaxial line

AbstractThe contribution of this work is to propose a novel circulator design using the substrate‐integrated coaxial line (SICL) structure. Conventionally, the circulator is composed of three‐dimensional waveguide components, and, in contrast, the proposed SICL circulator allows the 3‐D waveguide circulator to be built in a planar form using the printed circuit board (PCB) technology. The proposed SICL circulator is composed of three substrates with two parallel signal strips embedded in the central SICL tunnel. For better impedance matching, a widened section is inserted in each uniform feedline, and the Y‐junction joint on the bottom surface of the middle substrate is connected with three stubs and is loaded with a circular disk on the top surface of the middle substrate. A bandpass filter (BPF) can be embedded in each circulator's branch to improve signal selectivity and the out‐of‐band isolation. Experiments are conducted to verify the circuit design. Agreements are observed between the measured and simulated data.

A Millimeter-Wave Antipodal Linearly Tapered Slot Antenna Array for 5G Wireless Communication

This paper presents an antipodal linearly tapered slot antenna (ALTSA) array with the newly emerging substrate-integrated coaxial line (SICL) technology. Each element of the proposed array consists of two vertically stacked antipodal tapered slot antennas (TSA) with the inner conductor of a SICL as the shared fin. The vertical symmetry of this radiating element structure significantly suppresses the cross-polarization level. By employing a SICL-based power splitter with differential outputs, a two-element array with horizontal symmetry is formed. With the inner conductors of two parallel SICLs combined as the flaring metal shared by adjacent tapered slots, the main beam squint is effectively suppressed. Experimental results show an actual −10-dB impedance bandwidth (BW) of 24.5∼34.4 GHz, and the realized gain range measured is 16.1∼18.7 dBi. The cross-polarization levels are −39.4 dB/−40.7 dB at 30 GHz for the E-/H-planes. The measured results agree well with the simulated data which demonstrates the feasibility of the proposed SICL-based ALTSA scheme in the potential 5 G·millimeter-wave (mmWave) applications.

Broadband eight‐way substrate integrated coaxial line power divider with high isolation

AbstractThis article presents a broadband substrate integrated coaxial line (SICL) radial power divider with high output isolation. The proposed power divider mainly consists of input impedance matching circuits, microstrip isolation circuits, and radial SICL circuits. The two‐layer substrate of the input impedance matching circuit acts as a quasi‐coaxial structure and is connected to the coaxial input port to provide the function of impedance matching. The star‐type microstrip isolation circuits are employed to enhance the isolation performance between the output ports of the power divider. Two designed substrates sandwiching the air cavity layer constitute the radial SICL circuit, and the input microwave signal is evenly divided into 8 channels of signals with the same power. The designed power divider using SICL technology has the characteristics of supporting transverse electromagnetic mode transmission, being broadband, and compatible with substrate integration. A prototype of the multi‐layers eight‐way SICL power divider is designed, fabricated, and measured. The measured results show that the relative bandwidth of 15 dB input/output return loss is 34% and 43%, respectively. The absolute bandwidth of 15 dB input/output return loss is 5–7 GHz and 4.5–7.1 GHz, respectively, and the isolation between output ports is greater than 20 dB in the above frequency bands.

A Compact Dual-Polarized Endfire Antenna Array for 5G Millimeter-Wave Terminal

This paper proposes a compact dual-polarized end-fire antenna array for 5G millimeter-wave (mmWave) application. The dual-polarized antenna unit is constructed by an open-ended substrate integrated waveguide (SIW) cavity for vertically polarized (VP) radiation and a broadband electric dipole for horizontally polarized (HP) radiation. By sharing the side walls of two neighboring SIW channels of the VP elements, the substrate integrated coaxial line (SICL) feeding structure for the HP element is achieved, thus a compact size of the final antenna array can be accomplished. To extend the bandwidth of the VP element, the quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode of the cavity and the slot mode of the end-fire aperture are adopted for the VP element. A corresponding linear array with four units is designed and fabricated. The common -10-dB impedance bandwidth covers from 24.8 GHz to 29.2 GHz. The maximum gain is 10.0 dBi for both polarizations, with an overlapped scanning coverage ranging from -41.5º to 45.5º at 27 GHz. The proposed design has a compact configuration, and a wide scanning range, which is alternative for 5G mmWave terminal application.

Mode Composite Substrate Integrated Coaxial Line Based on Substrate Integrated Coaxial Line and Periodic L-Shaped SSPP Structure

In this paper, a mode composite substrate integrated coaxial line (MCSICL) is proposed for transmitting fundamental mode and first high-order mode in dual frequency bands. The MCSICL consists of substrate integrated coaxial line (SICL) and periodic L-shaped spoof surface plasmon polariton (SSPP) structure etched on the inner conductor of the SICL. By introducing the L-shaped SSPP structure, the bandwidth of the fundamental mode of the SICL can be suppressed without changing the cut-off frequency of the first high-order mode. Therefore, the proposed MCSICL can transmit signals at the low-frequency band with the fundamental mode and at the high-frequency band with the first high-order mode. The equivalent circuit model is built to analyze the propagation properties of the MCSICL. In addition, to excite the two modes independently, a grounded coplanar waveguide (GCPW) to MCSICL transition and a microstrip line (ML) to MCSICL transition are designed. The MCSICL with the transitions is fabricated under the printed circuit boards (PCB) process. Measurement results show that the MCSICL can propagate the fundamental mode from dc to 30 GHz and the first high-order mode from 42 to 60 GHz, and the isolation between the two modes is larger than 30 dB.

Substrate-Integrated Dual-Band Leaky-Wave Antenna With Open Stopband Suppression

This communication presents a substrate integrated dual-band continuous transverse stub (CTS) leaky-wave antenna (LWA). Two kinds of CTS slots, i.e., conventional CTS slots and those ones backed by waveguide slots are interlacing to support the excitation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> =-1 harmonic in two different frequency bands, thus, enabling dual-band beam scanning. Furthermore, the open stop-bands (OSBs) in both bands are suppressed by adding matching stubs and arranging the radiating slots in corrugation, so that the continuous beam scanning from the backward to forward can be obtained. The ultra-wideband linear source generator based on substrate integrated coaxial line (SICL) is subsequently designed to support the radiating structure. For validation, a prototype operating at both 13-20 GHz and 25-37 GHz is implemented. Experimental results show that, the scanning ranges of the LWA are -48° to +50° and -53° to +38° over the low and high frequency bands. During the beam scanning, the peak gain is better than 8.4 dBi and 13.2 dBi at the two operating bands.

Band-Stop Filter Based on Glide-Symmetric Substrate-Integrated Coaxial Lines for Band-Gap Control and Bandwidth Customization

Band-stop filters play an important role in wireless communications by blocking signals within specified frequency bands and allowing useful frequencies to pass through. As a special type of higher symmetry, glide symmetry achieves the reconfiguration of band gaps by manipulating the dispersion relationships of periodic structures, which is of great value for filter designs. However, existing band-stop filters based on glide symmetry are mainly realized with three-dimensional transmission lines, and only one band gap is reconfigured. Here, we explore glide symmetry in planar substrate-integrated coaxial lines (SICL) to reconfigure multiple band gaps and, in the meantime, customize their bandwidths and locations. For practical applications, three types of SICL band-stop filters with different glide symmetries are designed, fabricated, and measured. By changing the geometry of the glide-symmetric inner conductor, two distinct stopbands can be reconfigured and their bandwidths can be customized. The measurement results agree well with the numerical results, demonstrating high controllability and good filtering performance. The proposed glide-symmetric SICL provides a facile method to implement controllable band-stop filters and may facilitate more planar implementations with glide symmetry for dispersion manipulations.

A Wideband Compact Printed Dipole Antenna Array With SICL Feeding Network for 5G Application

A wideband compact printed dipole antenna array with an element size of 0.16 λ0 × 0.34 λ0 is proposed for millimeter-wave (mmW) applications, particularly for 5G applications. The two patches of the dipole are printed on two different layers to achieve a wide bandwidth of 50% (24–40 GHz) for SWR <2. Ground-signal-ground transmission line construction with a height difference between the feeding via and the two shorting vias is employed to achieve a relatively symmetrical radiation pattern. An antenna array consisting of the proposed antenna and a 1 to 8 substrate-integrated coaxial line feeding network is fabricated and measured. Simulations are also used to verify the beam scanning performance (up to ±50°). The proposed compact printed dipole antenna is a good contender for 5G mmW applications due to its wide band, compact size, and good beam scanning performance.

An Ultra-Wideband Electric Field Probe With High Sensitivity for Near-Field Measurement

An ultra-wideband electric field probe with high sensitivity is proposed for near-field measurement. It consists of the coupling part, the transmission part and the output part. In coupling part, the L-shaped tip and the loaded sensing via are designed to improve the sensitivity. In the output part, the horizontal gradual substrate integrated coaxial line (SICL) to grounded coplanar waveguide (GCPW) transition is designed for good field and impedance matching, resulting in wide bandwidth. In addition, the equivalent circuit is established to explain the mechanism of sensitivity improvement and optimize performance of the proposed probe. The proposed electric field probe is made with printed circuit board (PCB) process and applied to measure the electric near field. The measurement results show that the electric field probe has the bandwidth from 10 MHz to 60 GHz and the spatial resolution of 0.7 mm. In addition, the sensitivity of the proposed electric field probe is about 12 dB higher than that of the conventional monopole electric field probe at the same size of the coupling part.

Substrate-Integrated Coaxial Line (SICL) Rotman Lens Beamformer for 5G/B5G Applications

High-band allocations in the millimeter-wave (mm-Wave) frequency spectrum offer high-capacity wireless information transmission as required by fifth generation (5G) communication standards. Among different beamforming structures, the Rotman lens (RL) is an attractive passive-microwave-lens-based beamforming network due to its low fabrication cost, reliability, design simplicity and wide-angle scanning capabilities. Conventionally, the RL is implemented using microstrip line (MSL) technology for which there are inherent radiation losses that become severe when operating in mm-Wave 5G frequency bands. In this context, a novel substrate-integrated coaxial line (SICL)-based RL is designed, fabricated and tested, for accurate beamforming with extremely low feed line insertion loss. This article presents a complete design, development and performance analysis of an SICL-based RL beamformer. By using an SICL, isolation of up to 15 dB is achieved between the input beam ports of the RL, while the mutual coupling is kept at less than 20 dB. The SICL design shows a −10 dB insertion loss between the array and beam ports when compared to the same RL developed using MSL technology having an insertion loss of −15 dB. Due to the use of low-loss SICL technology, a realized gain of up to 14.2 dBi is achieved with an excellent scanning capability of −30 to 30 degrees, verifying for the first time the beamforming capabilities associated with SICL technology. The operational frequency band is 20–45 GHz, while the center operating frequency is 26 GHz making it appropriate for above 6-GHz 5G New Radio (NR) operating bands n257 (26.5 GHz to 29.5 GHz), n258 (24.25 GHz to 27.5 GHz), n261 (27.5 GHz to 28.35 GHz) and n260 (37 GHz to 40 GHz). Owing to the low-loss and stable beamforming performance, the SICL RL is suitable for mm-Wave 5G and is extendable to B5G applications.

A 3D-Printed DRA Shared-Aperture Array for Low Cost Millimeter-Wave Applications

In this article, a K-/Ka-band shared-aperture array with high isolation is proposed using 3D-printed dielectric resonator antennas (DRAs). The design procedure with DRAs enables flexibility while implementing shared-aperture arrays. Furthermore, DRAs as nonmetallic radiators are attractive for millimeter-wave (mm-wave) applications due to the absence of ohmic loss. In addition, 3D-printing technology facilitates the design of complex shapes with high-dimensional accuracy. The K- and Ka-bands DRAs are orthogonally oriented to provide improved isolation and cross-polarization level. Meanwhile, the corresponding feeding networks are implemented using the substrate integrated coaxial line (SICL) and the substrate integrated waveguide (SIW). Thus, further isolation improvement is provided by using two different feeding mechanisms for the K- and Ka-bands radiators. Moreover, the SICL network is shared with the SIW wall to efficiently utilize the feeding aperture. As a proof-of-concept, the 3D-printed shared DRAs are designed and fabricated. The standard printed circuit board (PCB) technology is used for the fabrication of the antenna boards. The measurement data agree with the simulations, realizing high isolation and cross-polarization level. The proposed array features low profile, ease of integration, and wideband operation, which makes it viable candidate for mm-wave applications.

Fully shielded and self‐packaged compact quarter‐mode substrate integrated coaxial line bandpass filter for X and K ‐band

In this work, a dual-mode substrate integrated coaxial line (SICL) bandpass filter supporting single-band and dual-band operation for widely spaced passbands located in X and K - band is proposed. Firstly, a cavity conceived with shorted half-wavelength SICL line is investigated. For enhanced miniaturization, a new SICL cavity is developed from the short-circuited half-wavelength SICL line which is bisected along the fictitious magnetic wall to derive its half-mode and quarter-mode counterparts. A fully shielded compact dual-mode dual-band filter is realized by coupling two quarter-mode cavities. The proposed SICL based filter realized using standard PCB fabrication process demonstrates ease of design and enhanced flexibility in exciting the higher order mode to attain the second-passband. The experimental results indicate widely spaced passbands with 3-dB bandwidth of 3.18 GHz and 0.27 GHz centered at 9.61 GHz and 19.12 GHz, respectively. The proposed compact SICL based quarter-mode filter occupies only 0.15 λ g 2 lateral area.