Search Results (89)

This paper presents a miniaturized ultra-wideband high-pass filter integrated with a notch function based on low-temperature co-fired ceramic (LTCC). The design motivation is to realize continuous wideband high-pass transmission while rejecting a narrow in-band interference/leakage component in compact RF front-end modules. The proposed design employs a cascaded structure of a seventh-order quasi-elliptic HPF and a three-section $\lambda /4$ stub notch filter in a single multilayer LTCC chip. Multiple transmission zeros (TZs) are introduced to improve the lower-stopband selectivity, while the three-section coupled-line NF produces a tunable localized rejection band. The LTCC implementation further integrates multilayer capacitors, three-dimensional helical inductors, shielded strip-line coupling stubs, a grounding compensation capacitor, and an isolation wall to balance compactness, impedance matching, and parasitic suppression. The fabricated chip achieves an ultra-wide bandwidth of 2.35 octaves, a notch 20 dB FBW of 8.5%, an insertion loss below 2 dB, a 60 dB roll-off rate of 154.1 dB/GHz within the lower stopband, and a voltage standing wave ratio (VSWR) less than 2. Experimental results validate that the proposed compact chip meets communication requirements and is suitable for 5G base stations, radar systems, and other applications. The chip dimensions are 4.5 mm × 3.2 mm × 2.5 mm. Full article

The high-density integration of low-temperature co-fired ceramic (LTCC) filters inevitably induces complex parasitic coupling. Traditional designs rely on forced isolation to mitigate this issue, often at the expense of increased physical footprints. To overcome this limitation, this paper proposes a strategy for the controlled utilization of parasitic effects. Methodologically, localized grounding structures are introduced to construct a controlled electromagnetic boundary. The system’s main path exhibits alternating inductive-capacitive (L-C) coupling, with a single explicit capacitive cross-coupling introduced between specific nodes (resonators 2 and 5). Based on the principle of multi-path signal cancellation, this explicit path synergizes with the implicit parasitic environment. By satisfying conditions of equal amplitude and a 180° phase difference at specific frequencies, a high-order hybrid network is equivalently reconstructed, generating four transmission zeros (TZs). A compact sixth-order LTCC filter was fabricated and tested. Measured results demonstrate a fractional bandwidth (FBW) of 38.6%, a shape factor of 1.16 (based on the 20-dB/3-dB bandwidth ratio), and a 20-dB upper stopband extending beyond $4.28f_0$. In conclusion, the rational utilization—rather than forced isolation—of inherent parasitic effects provides an effective solution for enhancing frequency selectivity and stopband performance in high-density integrated RF front-ends. Full article

With the growing simultaneous demands for miniaturization and high performance, thermal issues such as hotspots severely degrade the high-speed signal transmission performance of low temperature co-fired ceramic (LTCC) substrate in system-in-package (SiP) modules. This paper proposes a high-speed transmission line design for LTCC substrates, using a G-S (Ground-Signal) structure to ensure reliable signal transmission quality. Based on this structure, finite element simulations are performed to investigate the electromagnetic signal transmission characteristics under both uniform and non-uniform thermal fields, confirming that signal transmission efficiency exhibits strong temperature dependence. The results indicate that when the temperature exceeds 50 °C, non-uniform temperature distributions exert a significantly stronger influence on electromagnetic performance, leading to aggravated signal reflections and reduced transmission efficiency. At 300 °C, the transmission efficiency under non-uniform temperature drops to 35.0%, which is a 61.8% decrease compared with the optimal scheme obtained under ideal electric field conditions. Under electromagnetic-thermal coupling, a comparative study of different schemes shows that the optimal design derived from a single electric field is not suitable for electromagnetic-thermal coupled working conditions. The optimized Scheme 2 increases transmission efficiency to about 75.3%, with smoother S-parameter curves and smaller fluctuations. These findings provide valuable references for subsequent reliability-oriented design and experimental verification. Full article

(Li_0.4Co_0.2Ni_0.2Cu_0.2Zn_0.2)WO₄ high-entropy ceramics were prepared by a conventional solid-state reaction route. This study thoroughly explores the interrelationships between their crystal structure, bond properties, and microwave dielectric characteristics. X-ray diffraction analysis verified that all specimens crystallized in a single-phase ZnWO₄-type structure. According to Rietveld refinement of the XRD data, the lattice parameters are affected by the ionic radii of the constituent elements, confirming their dissolution and random distribution at Zn sites. Relative density exhibited a strong dependence on sintering temperature. Bonding analysis highlights the crucial role of the W–O bond in governing the dielectric response of the (Li_0.4Co_0.2Ni_0.2Cu_0.2Zn_0.2)WO₄ (LCNCZW) ceramics. Moreover, sinterability can be improved through optimizing the sintering process. Notably, samples sintered at 850 °C attained suitable dielectric performance, characterized by εᵣ = 11.697 ± 0.204, Q × f = 23,851 ± 0.126 GHz, and τ_f = 21.335 ± 0.232 ppm/°C. These results demonstrate that high-entropy design can effectively improve the sinterability and microwave dielectric performance of wolframite-type ceramics, offering a promising strategy for the development of microwave dielectric ceramics for communication devices. Full article

Based on monolithic microwave integrated circuit (MMIC) technology, this paper presents the design and implementation of a low-cost, highly integrated Ka-band sixteen-channel transmit/receive (T/R) module, specifically tailored to meet the application requirements of phased array antennas in airborne and spaceborne radar systems, satellite communications, and 5G/6G millimeter-wave networks. The proposed module employs an MMIC-based single-channel dual-chip discrete architecture, optimally integrating amplitude-phase multifunction chips and transmit-receive multifunction chips in terms of both fabrication process and performance characteristics, achieving a favorable balance between high performance and high-integration density. Using low-cost, low-temperature co-fired ceramic (LTCC) substrates, full-silver conductive paste, and a nickel–palladium–gold plating process, a novel “back-to-back” thin-slice packaging technique is presented to improve integration, lower manufacturing costs, and boost long-term reliability. Furthermore, the design incorporates glass insulators and a direct array interconnection scheme, which significantly minimizes transmission losses and reduces interface dimensions. The final module measures 70.3 mm × 26.2 mm × 10.9 mm and weighs only 34 g. Experimental results demonstrate a transmit output power of at least 23 dBm, a receive gain exceeding 26 dB, and a noise figure below 3.5 dB, achieving a 22.5–58% reduction in volume per channel while maintaining competitive RF performance. To improve testing effectiveness and guarantee data consistency, an automated radio frequency (RF) test system based on Python 3.11.5 was also developed. This work provides a practical technical approach for the engineering realization of Ka-band phased array systems. Full article

New glass-free low-temperature co-fired microwave dielectric composites with compositions (1–4x/3)Ba₃(VO₄)₂–xBaWO₄–(2x/3)Li₃VO₄ (x = 0.3–0.7) were fabricated by reactive liquid-phase sintering of (1–x)Ba₃(VO₄)₂–xLi₂WO₄ mixtures at 850 °C. During sintering, Li₂WO₄ is fully consumed by reacting with Ba₃(VO₄)₂ to form BaWO₄ and Li₃VO₄ while providing a transient liquid phase that promotes densification. As a result, the sintered ceramics achieve high relative densities of ≈94–98% at 850 °C. The relative fractions of Ba₃(VO₄)₂, BaWO₄, and Li₃VO₄ can be systematically tailored by adjusting the initial Li₂WO₄ content, enabling effective control of the temperature coefficient of the resonant frequency (${\tau }_f$) and the quality factor (Q × f). With increasing Li₂WO₄ content, the ${\tau }_f$ values shift from +23.97 to −45.48 ppm/°C, owing to the increasing contributions of the negative ${\tau }_f$ phases BaWO₄ and Li₃VO₄, while the Q × f values increase moderately from 44,300 to 47,300 GHz. The optimal microwave dielectric properties are obtained for x = 0.5, meaning ${\epsilon }_r$ = 9.19, Q × f = 45,900 GHz, and ${\tau }_f$ = −1.15 ppm/°C when sintering at 850 °C for 1 h. Chemical compatibility tests confirmed that the composites exhibit no detectable reaction with Ag electrodes, indicating that the Ba₃(VO₄)₂–BaWO₄–Li₃VO₄ system is a promising glass-free dielectric for LTCC applications requiring low firing temperature, near-zero thermal drift, and reliable electrode compatibility. Full article

Low-Temperature Co-Fired Ceramic (LTCC)-based mechanical sensors are inherently limited by the thickness and rigidity of multilayer ceramic stacks, which restrict miniaturization and mechanical compliance. To overcome these constraints, this work presents a hybrid LTCC/Kapton^® platform enabling high-sensitivity mechanical sensing through mechanically tunable RF passive components. The proposed approach integrates a flexible polyimide membrane, bonded onto an LTCC substrate at low temperatures using selectively electroplated indium pillars that simultaneously define the air gap and provide mechanical fixation. Inductance tuning is achieved via metal-shielding proximity effects, whereas capacitance tuning relies on force-controlled air-gap modulation in a metal–insulator–metal configuration. The fabrication process ensures precise gap control, high compliance, and structural robustness without requiring deformable ceramic membranes. Experimental characterization, including three-dimensional surface profiling and impedance measurements, demonstrates a 48% inductance tuning range with a sensitivity of 0.715 nH/mN and a 36% capacitance tuning range with a sensitivity of 47.3 fF/mN at 1 MHz. The proposed hybrid platform provides a compact and scalable solution for high-sensitivity sensors and mechanically reconfigurable RF components suitable for harsh-environment and adaptive electronics applications. Full article

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