Low-temperature Co-fired Ceramic Bandpass Filter Research Articles

A 4th-Order LTCC Bandpass Filter with Both Tunable Center Frequency and Bandwidth

Reconfigurable filters are one of the key components in microwave communication systems. This letter presents a 4th-order low-temperature cofired ceramic (LTCC) bandpass filter with both a tunable center frequency and bandwidth. This filter has four resonators, and each resonator consists of a circular patch, a center-through via, and two varactors. The varactors are placed on the top and bottom layers of the ceramic medium, which can effectively reduce the size of the 4th-order tunable filter. Three transmission zeros (TZs) are introduced to improve the upper stopband rejection. This filter demonstrates a 3-dB bandwidth (BW) range of 170–220 MHz around 2.86 GHz and a 3-dB BW range of 190–320 MHz around 3.2 GHz with a 13 dB minimum return loss. Insertion loss ranging from 3.5 dB to 6.85 dB has been obtained. The overall circuit size, including the package, is 11 mm × 6 mm × 1.6 mm.

LTCC Bandpass Filter Chips With Controllable Transmission Zeros and Bandwidths Using Stepped-Impedance Stubs

A novel bandpass filter (BPF) chip using stepped-impedance stubs (SISs) embedded in coupled lines (CLs) based on the low-temperature cofired ceramic (LTCC) technology is proposed in this brief. The controllable bandwidth (BW) is mainly realized by the wide range of variable coupling strength of the broadside CLs, and the controllable transmission zeros (TZs) can be generated by SISs to obtain high selectivity. Furthermore, in order to obtain a general design method for the proposed BPF with different BWs, the analytical (closed-form) process based on the even- and odd- mode analysis method is presented. For verification, a prototype for the proposed BPF operating at 3.5 GHz with the 3-dB fractional bandwidth (FBW) of 32.0% is designed, simulated, fabricated, and measured, respectively. Finally, the measured results that are in good agreement with the simulation show good performance of the proposed circuit.

Compact semi-lumped bandpass filter with sharp rejection

ABSTRACT A novel compact low-temperature-cofired ceramic (LTCC) bandpass filter with sharp rejection and wide stopband is presented in this paper. Semi-lumped resonant cells composed of multilayer ceramic capacitors and via-hole inductors are utilized with source–load coupling, thus two transmission zeros (TZs) can be generated near both sides of the passband, resulting in a high skirt selectivity and wide harmonic suppression. A LTCC bandpass filter works from 2.1 to 2.3 GHz has been designed and fabricated in a four-layer substrate to verify the proposed topology. With an extremely compact size of 2.0 mm × 1.25 mm × 0.9 mm, the design is highly integrated and suitable for miniaturized modern wireless communication applications.

Ultra-Low-Loss Millimeter-Wave LTCC Bandpass Filters Based on Flexible Design of Lumped and Distributed Circuits

The design of ultra-low-loss millimeter-wave (mm-wave) low-temperature cofired ceramic (LTCC) bandpass filters is proposed by merging the lumped and distributed circuits in this breif. By inserting a ground plane inside the filter, the cross talk between quasi-lumped capacitors and distributed microstrip lines can be highly reduced. Accordingly, the lumped or distributed circuits can be analyzed and designed flexibly for further performance improvements. To alleviate the design complexity, a lossy equivalent circuit model is introduced and verified for the proposed LTCC bandpass filter. Based on the equivalent circuit, the techniques for enhanced stopband rejection and low insertion loss can be both obtained. For experimental verification, two 27 GHz LTCC bandpass filters are designed, fabricated, and measured. Very low insertion losses of only 0.73 dB and 0.84 dB, wide stopband, and multiple transmission zeroes are realized, indicating the proposed LTCC filters good candidates for 5G system-in-package applications.

Compact Ku‐band LTCC bandpass filter using folded dual‐composite right‐ and left‐handed resonators

A compact Ku-band bandpass filter is proposed by using low-temperature cofired ceramic (LTCC) technology in this Letter. For miniaturisation, the folded dual-composite right- and left-handed (D-CRLH) resonator is introduced. By folding the inter-digital capacitor and microstrip section inductor in multiple metal layers, the circuit size of D-CRLH resonator can be reduced to one third of the planner one. Furthermore, the additional transmission loss caused by reverse currents is also investigated. To this end, a very compact LTCC filter is designed, fabricated, and measured, with the core circuit size smaller than 0.91 × 0.95 × 0.29 mm 3 . The minimum insertion loss is 1.95 dB at 13 GHz while with wide stopband suppression from 14.3 to 33.1 GHz.

LTCC Wideband Bandpass Filters With High Performance Using Coupled Lines With Open/Shorted Stubs

Two compact low-temperature co-fired ceramic (LTCC) wideband bandpass filters using coupled lines with open/shorted stubs are proposed in this paper. Two conventional coupled lines with open/shorted stubs are used to increase the passband order for the wideband filters. Two independent transmission zeros realized by the open/shorted coupled lines are used to further improve the passband selectivity and harmonic suppression. Due to the 3-D LTCC circuit, the coupled lines and stubs can be located at different layers to overcome the large circuit size. Two fifth-order wideband LTCC bandpass filters centered at 3.1 GHz with multiple transmission zeros are designed and fabricated for verification. The theoretical and measured results are in good agreement and show good in-band performances.

Synthesis and Implementation of LTCC Bandpass Filter With Harmonic Suppression

In this paper, we utilize the coupling matrices to design a compact low-temperature cofired ceramic (LTCC) bandpass filter with wide stopband and high selectivity. One coupling matrix at the fundamental frequency is synthesized to obtain required passband responses. The other one at the third harmonic is manipulated to realize wide stopband. Two transmission zeros are appointed at both sides of the passband to enhance the skirt selectivity. They are generated by multiple cross-coupling paths, which are easy to realize in the multilayer LTCC structure. To reduce the circuit size, two coupled quarter-wavelength resonators are folded vertically and horizontally on different layers. An experimental filter is designed for verification. High skirt selectivity and wide stopband are observed in the measurement. Due to the LTCC techniques, the proposed circuit has a compact size of $2~\text {mm}\times 1.7~\text {mm}\times 2$ mm or $0.042\lambda _{g}\times 0.035\lambda _{g}\times 0.042\lambda _{g}$ . It is suitable for system-in-package applications.

BPF integrated amplifier module using LTCC technology for millimeter‐wave applications

ABSTRACTA compact amplifier module integrating a low‐loss stripline (SL) band‐pass filter (BPF) using low‐temperature cofired ceramic (LTCC) technology is presented for millimeter‐wave (mm‐wave) applications. A parasitic resonance‐free SL BPF is proposed by modifying a distribution of ground vias in the SL LTCC BPF. The SL BPF fabricated in the 6 LTCC layers showed a 3‐dB bandwidth of 8.4% at the center frequency of 41.8 GHz. Its measured insertion and return loss were as small as 1.7 dB and 10.2 dB, respectively. The SL BPF integrated amplifier LTCC module was implemented in the single LTCC substrate in a size of 11.3 × 12.2 × 0.6 mm3. Its gain of 10 dB and output power of 18 dBm is achieved in the pass band from 39.5 to 42 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1821–1825, 2015

Synthesizing a Multiband LTCC Bandpass Filter With Specified Transmission- and Reflection-Zero Frequencies

This paper presents a vertically expandable low-temperature cofired ceramic (LTCC) bandpass filter (BPF) structure to increase the number of operating bands of the BPF without changing the area of the footprint. To design efficiently the proposed LTCC BPFs with highly configurable passbands and stopbands, a new method of synthesizing multiband BPF prototypes with specified transmission- and reflection-zero frequencies is developed. A dual-band BPF and a triple-band BPF were designed and implemented in LTCC. Both BPFs have the same area of 1.25×2.0 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Comparisons of the S-parameters among the synthesized prototypes, postlayout simulations and measurements exhibit a strong correlation.

Compact LTCC Bandpass Filter With Wide Stopband Using Discriminating Coupling

This paper presents a novel compact low-temperature cofired ceramic (LTCC) bandpass filter (BPF) with wide stopband and high selectivity. The proposed circuit consists of two coupled λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> /4 transmission-line resonators. A special coupling region is selected to realize a novel discriminating coupling scheme for generating a transmission zero (TZ) at the third harmonic frequency. The mechanism is analyzed and the design guideline is described. The source-load coupling is introduced to generate two TZs near the passband and one in the stopband. Thus, wide stopband can be obtained without extra circuits. Due to the LTCC multilayer structures, the filter size is 0.058 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ×0.058 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ×0.011 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> , or 2.63 mm × 2.61 mm × 0.5 mm. The simulated and measured results of the demonstrated LTCC BPF are presented to validate the proposed design.

Double-folded substrate integrated waveguide band-pass filter with transmission zeros in LTCC

A miniaturized substrate integrated waveguide (SIW) band-pass filter with two transmission zeros is proposed in low-temperature co-fired ceramic (LTCC) technology. The miniaturization of the filter is achieved by vertically stacking three double-folded SIW resonators. To strengthen the coupling between the feeding structure and the resonators, a new meandered microstrip feeding line is introduced. In addition, to realize better out-of-band rejection performance, two short-circuited lines are adopted in the filter design to achieve two transmission zeros outside the passband. To verify the design concept, an X-band LTCC band-pass filter was designed, fabricated, and measured. Both simulation and measurement results indicate that the proposed filter has good frequency response, high selectivity, and a size reduction of about 87% in comparison with conventional planar direct-coupled waveguide filter.

Modified constrained explicit knowledge-embedded space mapping using circuit tuning based on physical augmentation as parameter extraction

A new constrained space mapping algorithm is presented. This algorithm is based on aggressive space mapping type algorithm. Orthogonal projection is used to handle the constraints. The new method has advantage of simplicity without sacrificing mathematical robustness of space mapping. Proof of the convergence of the proposed method for convex constraints case is presented. Modified Broyden's method is used to improve the method's stability. The proposed algorithm is used to optimize a multilayer low-temperature cofired ceramic bandpass filter. Parameter extraction is done using circuit tuning based on physical augmentation. The results show the proposed algorithm is effective and efficient. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.

Compact LTCC bandpass filter with vertically folded structure

This work designs miniaturized stub-type microstrip bandpass filters and develops a novel vertical interconnection scheme in a multilayer structure to design vertically folded filters for size reduction. The current study exploits the fabrication process of low-temperature cofired ceramic (LTCC) for filter realization and fabricates two LTCC Chebyshev stub-type filters at 28 GHz and 5.8 GHz to verify effectiveness of the proposed structure with a maximum size reduction of 50%. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1389–1394, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26024

Super Compact Low-Temperature Co-Fired Ceramic Bandpass Filters Using the Hybrid Resonator

A novel low-temperature co-fired ceramic (LTCC) resonator is proposed based on the hybrid resonant circuits. The resonator exhibits a very compact size and is also able to introduce a transmission zero in the filter design. A super compact bandpass filter with high performance was designed at the center frequency of 2.45 GHz and fabricated using the proposed LTCC hybrid resonator. This filter has a very compact size of 0.9 mm 0.688 mm 0.652 mm and exhibits a low insertion loss of less than 1.2 dB in the passband. Moreover, the transmission zero that is located at 4.5 GHz efficiently suppresses the spurious responses. In order to improve the stopband suppression even more, the revised resonator is used for the second filter design. Besides occupying an even smaller volume of 0.76 mm 0.748 mm0.67 mm, the second filter exhibits a wide stopband suppression higher than 35 dB from 3.4 to 8 GHz. In addition to the super compact size and wide stopband suppression, insertion losses of less than 2.5 dB were achieved in the passband. A transmission zero at 5.8 GHz was also achieved.

기생 성분을 고려한 Wi-Fi와 WiMAX용 LTCC 무선 전단부 모듈의 구현

In this paper, a compact RF Front-end module for Wireless Fidelity(Wi-Fi) and Worldwide Interoperability for Microwave Access(WiMAX) applications is realized by low temperature co-fired ceramic(LTCC) technology. The RF Front-end module is composed of three LTCC band-pass filters, a Film Bulk Acoustic Resonator(FBAR) filter, fully embedded matching circuits, an SPDT switch for mode selection, an SPDT switch for Tx/Rx selection, and an SP4T switch for band selection. The parasitic elements of 0.2~0.3 pF are generated by the structure of stacking in the top pad pattern for DC block capacitor of SPDT switch for mode selection. These kinds of parasitic elements break the matching characteristic, and thus, the overall electrical performance of the module is degraded. In order to compensate it, we insert a parallel lumped-element inductor on capacitor pad pattern for DC block, so that we obtain the optimized performance of the RF Front-end module. The fabricated RF front-end module has 12 layers including three inner grounds and it occupies less than .

An FBAR‐ and LTCC‐based RF front‐end module for Wi‐Fi and WiMAX dual‐mode systems

AbstractA compact quad‐band RF front‐end module (FEM) is proposed for Wi‐Fi and WiMAX dual‐mode systems using film bulk acoustic resonator (FBAR) and low temperature co‐fired ceramic (LTCC) technologies. The quad‐band RF FEM consists of three LTCC bandpass filters, two diplexers, one FBAR filter, two single‐pole‐double‐throw switches, and one single‐pole‐four‐throw switch. The diplexers with the bandpass filters for each mode are fully embedded in the LTCC substrate, whereas the FBAR filter and three RF switches are placed on top of the substrate. The measured performance of the embedded diplexers with the bandpass filters is compared to the simulated one, resulting in good agreement between both performances. The implemented quad‐band RF FEM provides relatively low insertion loss with high attenuation at other passband for each mode. The overall size of the module is 6.0 mm × 5.0 mm with a substrate thickness of 0.6 mm. © 2010 American Association of Anatomists Microwave Opt Technol Lett 52: 753–757, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25023

Design of Low-Temperature Co-Fired Ceramic Bandpass Filters With Modified Coupled Inductors

With the assistance of modified coupled inductors, novel multilayered bandpass filters are developed in this paper. Two or three transmission zeros appear on both sides of the passband skirt easily by incorporating the proposed structures. In order to fabricate compact multilayered bandpass filters, the low-temperature co-fired ceramic technology is also employed. In addition, the equivalent circuits of the modified coupled inductors are also proposed. Consequently, the measured results of the fabricated bandpass filters agree well with the responses of the full-wave electromagnetic design.

Quasi-Static Derived Physically Expressive Circuit Model for Lossy Integrated RF Passives

This paper presents a novel approach for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deriving</i> a physically meaningful circuit model for integrated RF lossy passives such as spiral inductors on a silicon substrate. The approach starts from a quasi-static partial element equivalent circuit (PEEC) model. The concept of complex inductance and capacitance is introduced to uniformly deal with the conductor and dielectric losses. Basic Y- Delta network transformation is used to ldquoabsorbrdquo the insignificant internal nodes of the original PEEC network and to reduce the order of the circuit model. The physically expressive circuit model given here can be very concise while preserving the major physical meanings and attributes of the original circuit layout. A low-temperature co-fired ceramic bandpass filter and two practical inductors fabricated using a 0.18-mum CMOS process are studied by the model to demonstrate the validity of this new approach. Furthermore, the stability condition of the model is also discussed.

Design of low-temperature co-fired ceramic bandpass filter with transmission zeros in the stopband

A multilayered bandpass filter with low-temperature co-fired ceramic technology is proposed. By integrating two types of filters as one filter, four transmission zeros can be generated. Each type of filter with a source-load coupling capacitor and a grounded coupling inductor, simultaneously, can generate two transmission zeros located on the opposite side of the passband skirt separately. Moreover, the fabricated filter provides good matching with the electromagnetic simulation and can prove the availability of the filter configuration.

A Novel Compact Balanced-to-Unbalanced Low-Temperature Co-Fired Ceramic Bandpass Filter With Three Coupled Lines Configuration

This paper proposes a novel compact balanced-to-unbalanced bandpass filter. Firstly, a pre-design circuit is presented, which is composed of an inductive coupled-line bandpass filter and an out-of-phase capacitive coupled-line bandpass filter. A novel compact circuit with three coupled lines configuration, derived from the pre-design circuit, is then proposed for miniaturizing the balanced-to-unbalanced bandpass filter. A 2.4-GHz multilayer ceramic chip type balanced-to-unbalanced bandpass filter with a size of 2.0 mm times 1.2 mm times 0.7 mm is developed to validate the feasibility of the proposed structure. The filter is designed by using circuit simulation, as well as full-wave electromagnetic simulation softwares, and fabricated by the use of low-temperature co-fired ceramic technology. The measured results agree quite well with the simulated. According to the measurement results, the maximum insertion loss is 1.65 dB, the maximum in-band phase imbalance is within 3deg, and the maximum in-band magnitude imbalance is less than 0.32 dB.