Search Results (83)

With the advancement of wireless communication technologies into high-frequency millimeter wave and sub-THz bands, conventional transmission lines such as microstrip and stripline face significant limitations. Under the circumstances, along with the increased application of new transmission lines such as substrate-integrated waveguides (SIWs), the design of transition structures between different transmission lines has become a practical requirement in modern signal transmission systems. This paper presents a novel stripline to SIW transition structure. Drawing inspiration from the classical microstrip probe techniques in metal waveguides, the proposed design employs Low-Temperature Co-fired Ceramic (LTCC) technology for both device fabrication and SIW implementation. The developed structure demonstrates a stable performance, structural simplicity, and manufacturing feasibility. Through fabrication and testing, the transition structure can achieve a return loss below −10 dB across the 89–100 GHz frequency range, with an insertion loss of approximately 0.75 dB. Full article

In bare-die integration based on low-temperature co-fired ceramic (LTCC) multilayer interconnects, broadband signal transmission is often limited by impedance mismatch, parasitic effects introduced by gold-wire bonding, and discontinuities in interlayer transitions. These issues collectively form major bottlenecks for achieving low-loss and wideband interconnections in high-frequency LTCC modules. To address these challenges, this paper proposes a multi-layer collaborative optimization framework for LTCC bare-die interconnects operating from 1 to 20 GHz. The proposed framework jointly considers impedance matching, bonding parameter optimization, and interlayer transition enhancement to achieve broadband and high-performance signal transmission. First, two T-type microstrip matching networks are designed based on the complex input impedance of the bare die, and their parameters are optimized using ADS (an integrated circuit design software, version 2020). Second, a microstrip–gold-wire bond–bare-die interconnect model is established to analyze bonding-induced parasitic effects, revealing that a bond center spacing of 0.12 mm provides optimal high-frequency performance. Third, for the stripline–via–microstrip transition, a coaxial-like via structure combined with a square defected ground structure (DGS) is introduced to improve impedance continuity and electromagnetic field confinement. Full-path cascaded simulations demonstrate that the proposed interconnect achieves a return loss better than −23.1 dB and an insertion loss below 0.45 dB across the 1–20 GHz frequency range. Compared with conventional LTCC interconnect structures, the proposed method improves return loss by more than 7 dB and reduces insertion loss by approximately 0.12 dB. The results confirm the effectiveness of the proposed collaborative optimization strategy and provide reusable design guidelines for broadband bare-die integration in high-frequency LTCC multilayer modules. Full article

A new composite microwave–dielectric system, (1 − x)Li_2.08TiO₃-xLi₂ZnTi₃O₈ (x = 0.3–0.7), was systematically investigated to identify the optimal composition for low-temperature co-fired ceramic (LTCC) applications by correlating sintering behavior, microstructural evolution, and microwave–dielectric properties. Although the undoped compositions exhibited excellent intrinsic dielectric performance, they required sintering at 1100 °C, making them incompatible with Ag-based LTCC processing. Among the investigated formulations, 0.6Li_2.08TiO₃–0.4Li₂ZnTi₃O₈ was identified as the most suitable base composition. To reduce the sintering temperature, 0.3–1.0 wt.% V₂O₅ was introduced as a sintering aid, enabling densification at 900 °C for 30 min (97.0% relative density) while preserving the coexistence of Li_2.08TiO₃ and Li₂ZnTi₃O₈ without XRD-detectable secondary phases. Microstructural observations indicated that V₂O₅ promoted liquid-phase sintering, leading to enhanced densification and Li_2.08TiO₃-selective abnormal grain coarsening without altering the intrinsic permittivity. Complementary dilatometry provided process-level evidence for this liquid-phase sintering mechanism: large total shrinkage at 900 °C ($∆L/L_o$≈ −17–19%), earlier ${\mathrm{T}}_{\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{e}\mathrm{t}}$/${\mathrm{T}}_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}$ with ${\mathrm{T}}_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}$ lowered by ~250 °C, and an increased ${\mathrm{R}}_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}$, collectively supporting 900 °C/30 min as the practical firing window. The optimized 0.6Li_2.08TiO₃–0.4Li₂ZnTi₃O₈ composition containing 0.3 wt.% V₂O₅ exhibits excellent microwave–dielectric properties (${\epsilon }_{\mathit{r}}$ = 23.32, Q × f = 68,400 GHz, and ${\tau }_{\mathit{f}}$ = −1.55 ppm/°C). Higher V₂O₅ contents (>0.3 wt.%) caused a gradual reduction in Q × f due to increasing microstructural non-uniformity. Ag co-firing tests confirmed electrode stability with no interfacial reactions at 900 °C for 30 min. Overall, 0.3 wt.% V₂O₅-assisted 0.6Li_2.08TiO₃–0.4Li₂ZnTi₃O₈ provides a practical sub-950 °C processing window that satisfies key LTCC requirements, including moderate permittivity, high Q × f, near-zero ${\tau }_{\mathit{f}}$, and compatibility with Ag electrodes. Full article

Phased array radar, with its electronic scanning, high reliability, and multifunctionality, has become a core equipment for unmanned aerial vehicle detection, modern air defense, meteorological monitoring, and satellite communication. The T/R module is the core equipment of the active phased array radar, and its performance largely determines the performance of the phased array. At the same time, the application scenario requires relatively high transmission gain and transmission power, so attention should be paid to its heating situation. In addition, the overall size requirements for components are gradually becoming stricter, and miniaturization has become a trend in the development of T/R modules. This paper presents a four-channel T/R module in an X-band based on LTCC technology. In order to reduce weight and have high-density electronic devices, this module uses the latest technologies such as low-temperature cofired ceramic substrate (LTCC), Monolithic Microwave Integrated Chip (MMIC), and the MIC assembly process, and is hermetically sealed. The transmission channel of this module has high gain and high power, and the RF signal is transmitted through an eight-layer LTCC board to reduce interference between adjacent signal transmission lines and reduce the module size at the same time. The method of dividing the transmission and reception channels using a metal shell frame reduces crosstalk between the input and output ports of the transmission channel. Good heat dissipation design ensures the thermal management of the module. The test results show that the size of the TR module is 70 mm × 55 mm × 10 mm, the transmission power is ≥39 dBm, the reception gain is >28 dB, and the noise figure is <3 dB. Full article

Modification of the composition by doping is an effective way to develop new substrate materials for 5G/6G communication systems. This paper aims to study the impact of AlF₃-CaB₄O₇ doping on dielectric properties at very high frequencies, sintering temperature, microstructure, and feasibility in LTCC/ULTCC (low/ultra-low temperature cofired ceramics) technology of four low dielectric permittivity materials based on CuB₂O₄, Zn₂SiO₄, LiBO₂, and Li₂WO₄. Sintering behavior, microstructure, elemental and phase composition, and dielectric properties in the terahertz range were characterized using a heating microscope, SEM, EDS, XRD methods, and time domain spectroscopy. The developed ceramics exhibit excellent dielectric behavior at terahertz frequencies and are feasible in ULTCC or LTCC technology. These properties make them good candidates for substrates in 5G/6G communication systems. Full article

With the rapid evolution of 5G wireless communications, millimeter-wave (mmWave) technology has become a crucial enabler for high-speed, low-latency, and large-scale connectivity. As the critical interface for signal transmission, mmWave antennas directly affect system performance, reliability, and application scope. This paper reviews the current state of mmWave antenna technologies in 5G systems, focusing on antenna types, design considerations, and integration strategies. We discuss how the multiple-input multiple-output (MIMO) architectures and advanced beamforming techniques enhance system capacity and link robustness. State-of-the-art integration methods, such as antenna-in-package (AiP) and chip-level integration, are examined for their importance in achieving compact and high-performance mmWave systems. Material selection and fabrication technologies—including low-loss substrates like polytetrafluoroethylene (PTFE), hydrocarbon-based materials, liquid crystal polymer (LCP), and microwave dielectric ceramics, as well as emerging processes such as low-temperature co-fired ceramics (LTCC), 3D printing, and micro-electro-mechanical systems (MEMS)—are also analyzed. Key challenges include propagation path limitations, power consumption and thermal management in highly integrated systems, cost–performance trade-offs for mass production, and interoperability standardization across vendors. Finally, we outline future research directions, including intelligent beam management, reconfigurable antennas, AI-driven designs, and hybrid mmWave–sub-6 GHz systems, highlighting the vital role of mmWave antennas in shaping next-generation wireless networks. Full article

In this work we investigate the integration possibility of a thermistor paste from ESL (ElectroScience Laboratory, now Vibrantz) to see if it is adapted for Vibrantz Low Temperature Cofired Ceramics (LTCC) L8 and A6M-E materials. An alumina-based sample is used as a reference circuit throughout this study. Square, two-squares-in-parallel and two-squares-in-series thermistors are tested, placed internally and externally. Resistive values are measured in a range from 25 °C to 300 °C. The variation in the resistive values among similar thermistors is significant, with a maximum standard deviation of 67%. However, in all cases, there is a positive linear relationship between resistance and temperature. The Temperature Coefficient of Resistance (TCR) value is calculated before and after annealing. In general, the L8 and Al₂O₃ samples exhibit higher TCR values than the A6M-E sample. Additionally, when placed internally, the TCR value decreases approximately 30% for both tested LTCC materials. An Energy-Dispersive X-ray Spectroscopy (EDX) material analysis has also been conducted on the samples, revealing that the main chemical components are oxide, silicon, calcium, and ruthenium but also some barium and titanium, which indicates SiO₂, TiO₂, BaTiO₃ and RuO₂ oxides in the thermistor paste. The possibility to implement thermistors internally and externally on Vibrantz LTCC without delamination problems is endorsed by this study. Full article

Micromixing is a crucial process in microfluidic systems. In biochemical and chemical analysis, the sample is usually tested with reagents. These solutions must be well mixed for the reaction to be possible, generally using micromixers manufactured with sophisticated and expensive technology. The present work shows the design and evaluation of micromixers fabricated with LTCC (low-temperature co-fired ceramics) and FDM (fused deposition modeling) technologies for the development of functional and complex geometries. Two-dimensional planar serpentine and 3D chaotic convection serpentine micromixers were manufactured and implemented in an automated microanalytical system using photometric methods. To evaluate the performance of the micromixers, flow, mixing and absorbance measurements were carried out. Green tape and PP materials were used and showed good resistance to the acidic chemical solutions. The devices presented achieved mixing times in seconds, a reduced dispersion due to their aspect ratio, high sensitivity, and precision in photometric measurement. The optical sensing cells stored sample volumes in a range of 10 to 600 µL, which allowed the reduction of reagent consumption and waste generation. These are ideal characteristics for in situ measurement, portable, and low-cost applications focused on green chemistry and biochemistry. Full article

In order to meet the demand for high-frequency current sensors in 5G communication and new energy fields, there is an urgent need to develop high-performance nickel-zinc ferrite-based co-fired ceramic magnetic cores. In this study, a nickel-zinc ferrite core based on low temperature co-fired ceramic (LTCC) technology was developed. The regulation mechanism of BaCo_0.06Bi_0.94O₃ doping on the low-temperature sintering characteristics of NiZn ferrites was systematically investigated. The results show that the introduction of BaCo_0.06Bi_0.94O₃ reduces the sintering temperature to 900 °C and significantly improves the density and grain uniformity of ceramics. When the doping amount is 0.75 wt%, the sample exhibits the lowest coercivity of 35.61 Oe and the following optimal soft magnetic properties: initial permeability of 73.74 (at a frequency of 1 MHz) and quality factor of 19.64 (at a frequency of 1 MHz). The highest saturation magnetization reaches 66.07 emu/g at 1 wt% doping. The results show that BaCo_0.06Bi_0.94O₃ doping can regulate the grain boundary liquid phase distribution and modulate the magnetocrystalline anisotropy, which provides an experimental basis and optimization strategy for the application of LTCC technology in high-frequency current sensors. Full article

Monitoring internal pressure and temperature in lithium-ion batteries is essential for investigating internal chemical reactions, failure mechanisms, and providing early warnings of thermal runaway. The existing sensors face challenges in withstanding the high temperatures and corrosive electrolytes inside lithium-ion batteries. This work develops an integrated sensor with high robustness using low-temperature co-fired ceramic (LTCC) technology, which incorporates a multilayer ceramic circuit board, a digital pulse temperature sensor, a MEMS pressure sensor, and a microcontroller. It offers the real-time monitoring of pressure and temperature with digital output and calibrated accuracy, achieving a pressure resolution of 1 kPa with 0.085% F.S. accuracy and a temperature resolution of 0.1 °C with deviations under 0.5 °C. The pressure and temperature signals are independently output with drift below 0.067 kPa/°C. The integrated sensors were implanted into a pouch and prototype lithium-ion battery, respectively, for charge–discharge cycle monitoring. The results demonstrated that the integrated sensors could detect cyclic variations in pressure and temperature during charging and discharging until battery failure. Furthermore, the integrated sensors showed high stability after being immersed 60 days in the corrosive electrolyte, suggesting their potential as a novel method for monitoring the internal pressure and temperature of lithium-ion batteries. Full article

Reactive bonding can overcome the issues associated with conventional soldering processes, such as potential damage to heat-sensitive components and the creation of thermomechanical stress due to differing coefficients of thermal expansion. The risk of such damage can be reduced by using localized heat sources like reactive multilayer systems (RMS), which is already a well-established option in the field of silicon or metal bonding. Adapting this process to other materials, such as low temperature co-fired ceramics (LTCC), is difficult due to their differing properties, but it would open new technological possibilities. One aspect that significantly affects the quality of the bonding joints is the pressure applied during the bonding process. To investigate its influence more closely, various LTCC samples were manufactured, and cross-sections were prepared. The microscopical analysis reveals that there is an optimum range for the bonding pressure. While too little pressure results in the formation of lots of voids and gaps, most likely in poor mechanical and electrical properties, too high pressure seems to cause a detachment of the metallization from the base material. Full article

In this work, a small amount of AlN whiskers (ranging from 2 wt.% to 8 wt.%) was incorporated into CaO-MgO-ZnO-B₂O₃-SiO₂ (CMZBS)–glass/Al₂O₃ composites so as to obtain glass-ceramics with a thermally conductive network through sintering between 700 °C and 1000 °C. Special attention was given to the densification behavior, dielectric properties, and thermal conductivity of CMZBS/Al₂O₃/AlN–glass–ceramic composites with varying AlN whisker contents. According to the results, composites with desirable thermal, mechanical, and dielectrical properties were successfully fabricated. Notably, the composites containing 6 wt.% AlN whiskers, sintered at 800 °C, exhibited the most optimal comprehensive properties (dielectric constant of 7.06, dielectric loss of 383 × 10⁻⁵, thermal expansion coefficient of 6.40·10⁻⁶/K, flexural strength of 180 MPa, and thermal conductivity of 5.17 W/(m·K)). Given these attributes, this CMZBS/Al₂O₃/AlN composite holds great potential for applications in LTCC (low-temperature co-fired ceramic). Full article

In this paper, we examine an ultra-compact on-chip balanced filter based on novel hybrid resonators (NHRs) comprising short transmission line sections (STLSs) and series LC blocks using low-temperature co-fired ceramic (LTCC) technology. Based on a rigorous theoretical analysis, the proposed NHR demonstrates the potential for intrinsic ultra-wideband differential-mode (DM) and common-mode (CM) suppression without any additional suppressing structures. Furthermore, the resonance of NHRs was determined by four degrees of freedom, providing flexibility for miniaturization. Theoretical extensions of the Nth-order topology can be easily achieved by the simple coupling schemes that occur exclusively between STLSs. For verification, a balanced filter covering the 5G band n78 with an area of 0.065λ_g × 0.072λ_g was designed using the proposed optimization-based design procedure. An ultra-low insertion loss of 0.8 dB was obtained. The quasi-full CM stopband with a 20 dB rejection level ranged from 0 to 12.9 GHz. And the ultra-wide upper DM stopband with a 20 dB rejection level ranged from 4.4 to 11.5 GHz. Good agreement between the theoretical, simulated, and measured results indicate the validity of the proposed design principle. Full article

M²⁺N⁴⁺Nb₂O₈-type ceramics (where M = Mg, Ca, Mn, Co, Ni, Zn and N = Ti, Zr) are essential for satellite communication and mobile base stations due to their medium relative permittivity (ε_r) and high quality factor (Q × f). Although ZnTi_0.2Zr_0.8Nb₂O₈ ceramic exhibits impressive microwave dielectric properties, including an ε_r of 29.75, a Q × f of 107,303 GHz, and a τ_f of −24.41 ppm/°C, its sintering temperature of 1150 °C remains a significant barrier for integration into low-temperature co-fired ceramic (LTCC) technologies. To overcome this limitation, a strategy involving the partial substitution of Zn²⁺ with Cu²⁺ and the addition of LiF as a sintering aid was devised for ZnTi_0.2Zr_0.8Nb₂O₈. The dual impact of Cu²⁺ partial substitution and LiF as a sintering enhancer facilitated the successful sintering of Cu_0.3Zn_0.7Ti_0.2Zr_0.8Nb₂O₈ ceramics at a reduced temperature of 950 °C using the conventional solid-state reaction method. These ceramics exhibited excellent microwave dielectric properties. Notably, Cu_0.3Zn_0.7Ti_0.2Zr_0.8Nb₂O₈ ceramic with 40 mol% LiF addition demonstrated optimal microwave dielectric properties without any reaction with a silver electrode at a sintering temperature of 950 °C, yielding ε_r = 32, Q × f = 45,543 GHz, and τ_f = −43.5 ppm/°C. Full article

In this paper, a compact capacitive-loaded quarter-mode substrate integrated waveguide (CL-QMSIW) resonator is proposed and analyzed. This resonator is created by loading a metal–insulator–metal (MIM) capacitor inside the QMSIW resonator. A miniaturized hybrid bandpass filter with deep stopband suppression is designed based on the CL-QMSIW resonator and the stripline resonator. The filter generates a transmission zero (TZ) that can be adjusted flexibly through cross-coupling in its lower stopband, which significantly enhances the filter’s selectivity. To verify the correctness of the proposed filter, a third-order filter was created and produced, utilizing the low-temperature co-fired ceramics (LTCC) technique. The measurement outcomes align with the results from the electromagnetic simulations. The filter is characterized by a center frequency of 7 GHz, while the core size is only $0.33{\lambda }_g\times 0.17{\lambda }_g$, and the lowest insertion loss (IL) within the band is 1.4 dB, achieving a TZ at 5.1 GHz. The proposed filter features a compact dimension, excellent selectivity, and low insertion loss. Full article