Substrate Integrated Suspended Line Research Articles

A Ka-Band Two-Channel Two-Beam Receiver Based on a Substrate-Integrated Suspended Line

To realize the miniaturization and high performance for the key transceiver components of a phased array antenna, we proposed a two-channel two-beam receiver based on a substrate-integrated suspended-line (SISL). Multi-layer composite substrate printing circuit is used in the SISL structure to replace the metal cavity and passive circuits. The active components are placed in the air cavity in the SISL structure. The substrates forming the cavity are soldered together to ensure the hermetic seal and high performance. The SISL circuits have the advantage of low loss, low cost, light weight, self-packaging, and high inter-channel isolation. The proposed Ka-band two-channel two-beam receiver shows a gain of >28 dB, a noise figure of <2.6 dB, with functions of 6-bit phase shifting and attenuation.

Novel 6‐GHz/80.8% fractional bandwidth filtering power divider with ultra‐large coupling coefficient using air‐dielectric broadside‐coupled lines

AbstractIn the letter, a wideband filtering power divider (FPD) with ultra‐large coupling coefficient using air‐dielectric broadside‐coupled lines is proposed. The broadside‐coupled line and single transmission line are alternately connected to construct three resonators, which can be used for large bandwidth and high selectivity filtering. An improved substrate‐integrated suspended line (SISL) structure with two inner layers is developed. In the structure, the broadside coupling occurs by the air. The overall structure is implemented based on the low‐cost FR4 dielectric material. The designed FPD is simulated and fabricated. The results demonstrate its excellent performance, with center frequency of 6 GHz, a fractional bandwidth (FBW) of 80.8%, a maximum coupling coefficient of 0.84, an insertion loss of less than 0.29 dB, and an out‐of‐band rejection of more than 52 dB.

Synthesis Design of In-Line Pseudoelliptic SISL Bandpass Filter Employing Non-Resonating Mode in Low-Loss Patch Resonators

This paper presents a novel type of patch resonator suitable for the design of high selectivity in-line pseudoelliptic bandpass filters (BPFs) based on a substrate-integrated suspended line (SISL) platform. The proposed structure is a rectangular patch resonator that allows the propagation of the fundamental mode and high order modes. By controlling the position of input and output feedlines, the proposed resonators can provide both a reflection and a transmission zero simultaneously. Thus, a pole-zero pair can be produced (behaving as a singlet). The position of poles and zeros can be fully controlled by varying the position and orientation of the feeding lines. To verify the proposed concept, a detailed study about the behavior of the patch singlet and a validated third-order filter BPF with three TZs ( canonical BPF) located in the lower and upper passband is presented in this brief. The measured results exhibit an extended stopband with rejection better than 58 dB in the lower passband and 40 dB in the upper passband. The tested return losses and insertion loss are better than -15.7 dB and 1.31 dB, respectively.

A wideband and self-packaged D-CRLH diplexer based on substrate-integrated suspended line

A wideband and self-packaged D-CRLH diplexer based on substrate-integrated suspended line

A compact differential branch‐line coupler using folded substrate integrated suspended parallel strip line

AbstractThis letter presents a compact fully differential branch‐line coupler. It is composed of folded substrate integrated suspended parallel strip line (SISPSL), which can generate slow‐wave effect and help reduce the circuit size. The used SISPSL type line is a fusion of double‐sided parallel‐strip line (DSPSL) and substrate integrated suspended line (SISL), which has the advantage of self‐packaging as compared with traditional DSPSL exposed to air. A DC to 30‐GHz differential transition from grounded coplanar waveguide (GCPW) to SISPSL is designed to test the SISPSL differential coupler. The implemented SISPSL branch‐line coupler has a compact size of 0.056 λg × 0.05 λg.

Design of Ka-Band SISL High Selectivity Bandpass Filter With Controllable Zeros

In this letter, high selectivity bandpass filters (BPFs) using folded stepped-impedance resonators (SIRs) are proposed based on substrate-integrated suspended line (SISL) platform. It is easy to change the position of transmission zeros (TZs) by controlling the strength of electric/magnetic coupling, separately. Also, the structure is compact with double-layer wiring and via holes. To validate the proposed method, two SIR electromagnetic coupling BPFs are implemented on FR-4 substrates. The rectangular coefficients (BW <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{20\, \text{dB}}}$</tex-math> </inline-formula> /BW <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{3\, \text{dB}}$</tex-math> </inline-formula> ) of the second-order and the fourth-order filters are only 2 and 1.3, respectively. In addition, air cavity, metal shielding wall, and substrate excavation methods also dramatically reduce the loss in substrates.

Novel Miniaturized Self-Packaged Filters Based on Metasubstrate in SISL Platform

In this paper, a novel strategy is proposed to design miniaturized self-packaged filter based on the proposed metasubstrate in substrate integrated suspended line (SISL) platform. Multi-layer SISL and periodic metasubstrate structures contribute to the miniaturization and self-packaging of second-and fourth-order quarterwavelength hairpin filters, caused by the higher permittivity. The designed dumbbell-shaped metasubstrate shows a high relative permittivity of 15.4. The proposed FR4-based second/fourth-order filters with a reduced insertion loss of 1.13 dB/1.49 dB only show the miniaturized size of 0.26 λg ×0.19 λg and 0.27 λg ×0.32 λg, respectively. And the circuit areas of the above two designed filters with metasubstrate are reduced by 46% and 34%, compared with the cases without metasubstrate, successively.

Compact wideband filtering Balun Based on SISL Technology

AbstractA new compact wideband filtering balun based on substrate-integrated suspended line technology is presented in this brief. The proposed device is composed of a λg/4 suspended stripline open-circuited stub, a λg/2 suspended stripline resonator, and a λg/2 suspended slotline resonator. These striplines and slotline are encapsulated in an electromagnetic (EM) shielding box consisting of air cavity, surrounding substrate layers, and metal layers to achieve EM shielding performance. By properly exciting the suspended stripline and slotline resonators, three transmission poles are generated to achieve high frequency selectively. The intrinsic 180∘ phase difference between the two output ports can be obtained by using the electric field distribution caused by the perpendicular coupling between the suspension stripline and the slotline resonator. The wideband passband is achieved with magnitude balance and out-of-phase properties. To validate our proposal, a wideband filtering balun operating at 2.56 GHz with fractional bandwidth of 65.6% is designed and fabricated.

A negative‐resistance oscillator using dual‐cavity based on SISL technology

AbstractThis article presents a low‐phase noise negative resistance oscillator using the dual‐cavity resonator (DCR) based on substrate integrated suspended line (SISL) technology. Two air cavities are stacked without increasing the footprint areas of the oscillator. A coupling hole is introduced to realize weak coupling between the two air cavities. The DCR can enhance the roll‐off of the equivalent resonator. The measured Q factor of the DCR is increased by 15% compared with the single cavity resonator. The measured phase noise of the designed oscillator is −135.32 dBc/Hz at 1 MHz offset from the carrier frequency of 12.44 GHz, and the measured FOM at 1 MHz offset is −204 dBc/Hz. Besides, the designed oscillator based on SISL technology has the advantages of low cost, compact size, and self‐packaging properties.

3-D SISL Feeding Network for 2-D Cavity-Backed Endfire Dipole Array at 24 GHz

This letter presents a 4×4 cavity-backed endfire dipole array with a novel feeding structure named as three-dimensional substrate integrated suspended line (SISL) feeding network (TSISLFN). Based on the SISL's structural superiority, air-filled substrate integrate waveguide (AF-SIW) can be vertically integrated with planar SISL in a self-packaged manner to form the TSISLFN. TSISLFN can be easily integrated with 2-D cavity-backed dipole array and the overall architecture can be realized through printed circuit board (PCB) technology. Then, the cost and weight of the whole structure are significantly reduced compared to the metal-waveguide counterpart. TSISLFN possess merits of self-packaging, low cost, and low loss. Both 2×2 and 4×4 cavity-backed endfire dipole arrays fed by TSISLFN are fabricated and measured. At 24.5 GHz, high efficiency of better than 91% and 79%, gain of 15.2 and 20.6 dBi are all obtained for the proposed 2×2 and 4×4 array respectively. Similar narrow beam widths in both E and H planes are also obtained.

A High-Efficiency SISL-Based Slot Antenna Array for Wireless Power Transmission Application

A high-efficiency slot antenna array based on substrate integrated suspended line (SISL) technology operating at 24 GHz is presented for wireless power transmission (WPT) application. Because of the feature of self-shielding and low loss of SISL technology, double-side SISL (DSISL) is used to further reduce substrate and conductor loss in antenna design. Besides, four radiating slots are etched on the top ground layer of DSISL and serially fed as a subarray without any extra feeding network. By utilizing DSISL and avoiding network loss, a high efficiency subarray is realized with simulated efficiency of up to 89% at 24 GHz. In addition, the subarray is fabricated and measured. The measured results of subarray show that the 10 dB impedance bandwidth is from 23.75 to 24.1 GHz, which covers the WPT band (24 GHz ± 100 MHz). The measured gain of 13.1 dBi and radiation efficiency of 83.5% is achieved at 24 GHz. Besides, the width of air cavities can be further reduced to 0.384λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free space wavelength at 24 GHz), benefiting from the basic mode tangential electromagnetic (TEM) mode of DSISL, which is good for wide scanning phased array design. Based on the subarray, a 1×8 phased array is designed and fabricated. The measured results show that |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | of −32 dB, isolation of 19 dB, and gain of 19.5 dBi is obtained at 24 GHz, while a wide scanning range of ±50°with gain drop less than 3.3 dB is achieved also at 24 GHz.

A Low Phase Noise Oscillator Employing Weakly Coupled Cavities Using SISL Technology

A Ku-band low-phase noise oscillator, using a weakly coupled cavities resonator (WCCR), is proposed based on substrate-integrated suspended line (SISL) technology. Different from using a bandpass filter as the frequency selector for the feedback oscillator, we use weak coupling between resonators to form a resonator with a higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> . The theoretical analysis of weak coupling is derived. Under weak coupling, the equivalent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> and insertion loss of the WCCR is given based on the mathematical deduction. The proposed WCCR can double the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> factor of the single cavity resonator (SCR) at the expense of an increase in the insertion loss. Two oscillators using WCCR and SCR are designed and fabricated to verify the theoretical analysis. The measured results show that the loaded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of WCCR increases by 80% compared with the SCR. The proposed oscillator has a low measured phase noise of −137.36 dBc/Hz at 1 MHz offset from the carrier frequency of 12.355 GHz, and the FOM is −207.12 dBc/Hz. Compared with the oscillator using SCR, the measured phase noise is improved by 5.13 dB. Moreover, the proposed oscillator based on SISL technology has the advantages of low cost, compact size, and self-packaging properties.

A Filtering Antenna with Slots and Stacked Patch Based on SISL for 5G Communications

A filtering antenna based on the Substrate Integrated Suspended Line (SISL) platform applied for the n78 band of 5G is presented in this paper. The antenna has a segmented feed line, a rectangular driven patch etched with a double I-slot, and a squared stacked patch with grooves at the edges of both sides. The etched slots and the stacked patch introduce two new resonance frequencies increasing the bandwidth. Furthermore, the etched slots excite a deep radiation null in the low-frequency band, and the stacked patch coupled with the driven patch produces two deep radiation nulls in the high-frequency band. Three radiation nulls enable high selectivity of the antenna. The filtering antenna works at 3.2–3.89 GHz, which can be applied to the 5G (n78, 3.3–3.8 GHz) frequency band. The peak gain in the band can reach 9.21 dBi, and the out-of-band suppression levels are higher than 18.47 dB.

Hybrid Integration of Chips Using SISL for Ka-Band High Combining Efficiency Power Amplifier

Hybrid integration of millimeter-wave (mm-wave) chips for power combining amplifier using substrate-integrated suspended line (SISL) is studied for the first time in this letter. A bond wire compensation structure with small size, wide bandwidth, and cavity mode suppression is proposed, and the wire bonding interconnect obtains the bandwidth of 0–48 GHz. A power combining amplifier based on this structure is proposed and the heat dissipation optimization is carried out. Finally, a four-way full Ka-band spatial power combining amplifier with high combining efficiency is fabricated. From 26 to 40 GHz, the maximum output power at the 1-dB compression point is 31 dBm, and the power combining efficiency is 78%–93%.

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.

A Low-Cost SISL Differentially Fed Dual-Polarized Stacked Patch Antenna With Enhanced Common-Mode Suppression Using Characteristic Mode Analysis

A wideband differentially fed dual-polarized stacked patch antenna with high common-mode (CM) suppression is proposed in this article using the characteristic mode analysis (CMA) and the substrate integrated suspended line (SISL) technology. Based on the CMA, orthogonal slots are loaded within the stacked patch to enhance the directivity of the second-order degenerate modes and reallocate the resonating frequency of the fundamental degenerate modes. A crossed dipole is introduced within the driven patch to ensure polarization uniformity between the two paired degeneracies. The CM suppression level ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{\mathrm {CC}}11$ </tex-math></inline-formula> ) is enhanced from–10 to–1.30 dB within the frequency range of 4.0–7.0 GHz by embedding circular slots embedded within the stacked patch and controlling the slot radius. Measured results demonstrate a–10 dB differential impedance bandwidth of 28.4% (4.62–6.18 GHz) and high isolation of better than–39.5 dB between the differential ports. The antenna depicts stable measured radiation patterns with low cross-polarization (<–30 dB). The measured average antenna gain and efficiency are 9.55 dBi and 85.5% within the DM passband. In addition, a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{\mathrm {CC}}11$ </tex-math></inline-formula> better than–1.05 dB is measured within the desired DM band.

A Low-Cost Miniaturized Filtering Dielectric Resonator Antenna Based on SISL for 5G Applications

To realize a low-cost, miniaturized, and high selective design, the filtering dielectric resonator antenna (FDRA) for 5G applications is first proposed based on the substrate-integrated suspended line (SISL). The FDRA consists of two same rectangular DRs embedded in air cavities, which are fixed by the hollowed substrate rings. A T-shape feeder, rectangular feeder, and metalized holes are introduced to excite the fundamental <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {TE}}_{\delta 11}^{x}$ </tex-math></inline-formula> mode of DRA. The substrate rings and DR are regarded as a composite dielectric to miniaturize the antenna and have effects on the radiation nulls. Because of the different loading effects from the different feeders, the resonance frequency of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {TE}}_{\delta 11}^{x}$ </tex-math></inline-formula> mode excited by the different feeders is slightly different. Therefore, a wide bandwidth can be achieved. In the hybrid feed scheme, three radiation nulls are introduced near the edge of the frequency band without an extra filtering circuit. To improve the suppression level, the effective size of the radiator is increased by increasing the width of the substrate rings without changing the size of the whole structure. Therefore, two prototype antennas with different widths of substrate rings are designed, manufactured, and measured. Good agreement can be observed between simulated and measured results.

A 3 dB SISL coupler design by multi‐objective evolutionary algorithm based on decomposition

In this article, a 3 dB substrate integrated suspended line (SISL) coupler design by multi-objective evolutionary algorithm based on decomposition (MOEA/D) is proposed. SISL technology can provide electromagnetic shielding performance and realize the low loss, lightweight, and self-packaging. The highly time-consuming problem of adopting traditional electromagnetic (EM) simulation software to assist coupler design is always the main problem for the design of couplers. To solve the problem, this article applies MOEA/D based on one-dimensional convolutional autoencoders (1D-CAE) to assist coupler design. 1D-CAE model builds the surrogate model to help MOEA/D find out better responses faster. MOEA/D has some advantages of saving time and getting good performance easily.

A sequentially rotated feeding circularly polarized stacked patch antenna array based on SISL

AbstractA sequentially rotated feeding circularly polarized stacked patch antenna and its array based on substrate integrated suspended line (SISL) are presented. The resonant frequencies of 5.05 and 5.35 GHz are obtained by using the cross slot on the driven patch, which can also realize circular polarization. The windmill stacked patch is introduced to generate another resonant frequency of 5.85 GHz and expand 3‐dB axial ratio (AR) bandwidth (BW). The measured 10‐dB impedance BW of 18.2% (4.98–5.98 GHz) and the 3‐dB AR BW of 3.6% (5.45–5.65 GHz) are obtained from the proposed antenna element. The measured peak gain is 9.0 dBi. A sequentially rotated feeding is used to excite the proposed 2 × 2 antenna array. The measured peak gain is 13.31 dBi. The measured 10‐dB impedance BW is 28.3% (4.80–6.38 GHz) and the 3‐dB AR BW is 8.9% (5.35–5.85 GHz).

FR‐4‐based Ka‐band SISL bandpass filters using folded half‐wavelength resonators

AbstractIn this letter, bandpass filters (BPFs) with folded short‐circuited half‐wavelength (λ/2) resonators are proposed based on the substrate integrated suspended line (SISL) platform for satellite communications. Each λ/2 resonator is folded, to achieve an overlapping structure, which not only reduces the size, but more importantly, reduces the loss. In addition, air cavity, metal shielding wall, and substrate excavation method also dramatically reduce the loss in substrates. Note that professional material term (FR‐4) material is chosen for the design, therefore, it is low‐cost and more suitable for production application. Finally, a second‐order and a fourth‐order combline BPFs are fabricated and measured to verify the design method. The insertion loss of the second‐order and the fourth‐order filters are only 0.78 and 1.19 dB at the center frequency of 29.2 GHz, respectively. The presented SISL filters using FR‐4 material demonstrate the advantages of low‐loss, low‐cost, and self‐packaging.