Miniaturized High-Q Tunable RF Filters

This dissertation focuses on the investigation and development of novel efficient tuning techniques and the design of miniaturized high-Q tunable RF filters for high-performance reconfigurable systems and applications. First, a detailed survey of the available tuning concepts and state-of-art tunable filters is provided. Then, a novel so-called inset resonator configuration is presented for the applications of fixed and tunable coaxial filters. The design procedure of frequency tunable filters with constant absolute bandwidth (CABW) is described, and various tunable inset filters are implemented, offering many desirable merits, including the wide tuning range and stable high-Q with minimum variation. For wide octave frequency tuning ranges with CABW, a second novel concept is presented using so-called re-entrant caps tuners. Beside simplicity and compactness, this technique also features enhanced spurious performance and wider tuning capabilities than the conventional means. Also, in this dissertation, various miniaturized reconfigurable dual-band/dual-mode bandpass filters and diplexers are presented using compact dual-mode high-Q TM-mode dielectric resonators. Furthermore, a novel microfluidic-based ultra-wide frequency tuning technique for TM010-mode dielectric resonators and filters is introduced in this dissertation. In addition to the very wide tuning window, this mechanism has key advantages of low-cost, simplicity, and intrinsic switch-off. Lastly, the dissertation includes a novel bandwidth reconfiguration concept with multi-octave tuning using a single element for coaxial bandpass filters. This mechanism brings many features including the fast tuning, constant high-Q, intrinsic switch-off, and wide BW-reconfiguration

Miniaturized Dual-Band Dual-Mode TM-Mode Dielectric Filter in Planar Configuration

This paper reports a new class of compact inline dual-band bandpass filters using TM-mode dielectric resonators in planar configuration. Thanks to the employment of the dielectric-loaded TM-mode waveguide configuration and the dual-mode TM120 and TM210 resonances, substantial size miniaturization and volume saving (>70%) can be obtained in comparison with conventional waveguide technology. Additionally, the planar topology of the presented concept offers highly desirable advantages for industry and mass production including the ease of manufacturing, assembly, and tuning. Furthermore, the resonating doublets and the nonresonating TM110 mode are effectively utilized to introduce and control both inter-band and outer-band transmission zeros, advantageously increasing the isolation between the two passbands and enhancing the outer-band rejection regions. The general design procedure of the proposed filter is discussed in detail. A three-pole C-band dual-band dual-mode TM-mode dielectric filter is designed, implemented, and measured to validate the proposed configuration

Very Compact Diplexer Based on Dual-Mode Dielectric TM-Mode Resonators

A very compact in-line C-band diplexer is reported in this letter based on dual-mode dielectric TM-mode resonators in planar coupling configuration. In addition to the advantages of substantial volume-saving and easy assembly, the proposed diplexer features high-quality factor, enhanced spurious performance, high-power handling, and efficient tuning process with independent control of each passband. For verification purposes, a C-band diplexer is designed, implemented, and tested. The final assembled diplexer unit has a compact overall volume of 43 × 40 × 15.9 mm 3 . It operates at 4.73 and 5.03 GHz with the same bandwidth of 24 MHz, an insertion loss better than 0.9 dB, and a return loss higher than 21 dB. In addition, a high-power breakdown analysis shows that the introduced diplexer can handle high levels of input power up to 5200 W

Widely Tunable TM-Mode Dielectric Filters With Constant Absolute Bandwidth Using Re-Entrant Caps

This paper reports octave tunable dielectric combline bandpass filters with constant absolute bandwidth (CABW) using a novel re-entrant cap tuning technique. The resonant frequency is tuned by the hollow re-entrant cap penetrating into the filter cavity as an envelope around the dielectric resonator. This mechanism of tuning provides wider tuning capabilities and better spurious performance than the conventional screw-based tuning. Also, the cap tuners can be employed effectively to tune the input-output and inter-resonator couplings simultaneously with the frequency reconfiguration, enabling a CABW over a wide frequency tuning window. For proof of concept purposes, a single widely tunable resonator is presented with octave tuning ratio of 2.64:1, high quality factor from 1705 to 5480, and spurious-free band up to 3.44⋅ f0 . Afterwards, two octave tunable re-entrant cap filters are designed, fabricated, and tested. The first filter is a 78% widely tunable two-pole filter with a CABW of 43.5 ± 12% MHz, low insertion loss equals to 0.28 ± 0.03 dB, and a compact volume of 39 cm 3 . The second design is a four-pole octave tunable bandpass filter from 2.96 GHz to 1.36 GHz with a constant 69 ± 13% MHz bandwidth, low insertion loss better than 0.6 dB, return loss higher than 16 dB, and a compact 62 cm 3 structure. According to our own knowledge, thanks to the proposed tuning mechanism, the presented designs are the first CABW octave tunable high Q waveguide-based filters, having the widest tuning ranges over all similar state-of-the-art-designs

Tunable Coaxial Bandpass Filters Based on Inset Resonators

A new class of compact, high-Q, tunable coaxial filters is presented in this paper based on a novel inset resonator concept. The tuning concept is based on the displacement of movable resonators inside a properly modified metallic housing which features wide tuning capabilities and stable high Qfactor performance with minimum variation throughout the tuning window. Various prototypes are designed and implemented to demonstrate and validate the proposed concept. A single tunable inset resonator is first designed and measured showing distinctive results of a 43% tuning range, stable high-Q of 4100±4%, spurious-free band up to 3.8·f0, and volume-saving up to 50% when compared to the conventional combline and half-wavelength structures. The design procedure for constant absolute bandwidth (CABW) tunable filters is then presented, and two different tunable inset filters are designed and implemented. Firstly, a manually tunable four-pole filter is demonstrated with the merits of a wide 39.3% tuning range, while maintaining a constant bandwidth of 116 MHz±6%, and a stable high-Q of 1820±6%. Next, an automatically tunable 3rd-order inset filter is designed and measured using high-accuracy piezomotors. Similarly, the measured results exhibit a wide 1.3 GHz tuning range from 2.65 GHz - 3.95 GHz with a stable insertion loss that is less than 0.35 dB, a return loss that is better than 15 dB, and a good spurious performance up to 2.8·f0. To our own knowledge, the proposed tuning technique and tunable components represent state-of-the-art tuning range and stable high-Q with minimal variation when compared with similar loaded-waveguide designs

Design of Compact Quasi-Elliptic Bandpass Filters Based on Coaxial Inset Resonators

This article reports a novel inset resonator configuration for coaxial filter applications with quasi-elliptic responses. The design and analysis of the inset resonator are discussed in detail and accurately modeled as a capacitively-loaded stepped-impedance half-wavelength resonator featuring more compactness, high quality factor, and enhanced spurious responses in comparison with conventional half-wavelength and combline resonators. Additionally, the operating frequency can be tuned intrinsically through the displacement of the coaxial resonator, eliminating the need for any additional tuning elements and maintaining a stable quality factor. Two quasi-elliptic inset resonator type filters are implemented in planar and longitudinal coupling configurations, respectively. The first takes the form of a folded four-pole 2.93 GHz filter with two symmetrical transmission zeros. The fabricated filter has a compact structure of 29.76 cm3, an insertion loss better than 0.73 dB, a return loss better than 18 dB, and a wide spurious-free band up to 3.5⋅f0 . The second inset-type quasi-elliptic filter is realized in a longitudinal inline arrangement. An example of a 2.53 GHz three-pole filter is presented with a closely-positioned transmission zero, wide spurious-free band ( ≈3⋅f0), and a very compact structure of 55.7×33×33 mm3

Bandwidth-Reconfigurable Coaxial Bandpass Filter With Multioctave Tuning Using a Single Element

A bandwidth (BW) tunable coaxial-loaded waveguide filter is presented in this letter based on a novel concept using a single tuning element. The operation principle relies on the rotation of coaxial resonators with respect to fixed irises in order to change the inter-resonator (IR) coupling strengths that control the BW. This mechanism features multioctave tuning while maintaining a fixed operating frequency and a stable unloaded quality factor with only one rotary post. Furthermore, the filter can be switched off by using the same tuning mechanism. A prototype is manufactured and measured to verify the proposed filter. The measured results demonstrate multioctave BW tunability from 12 to 83 MHz (tuning ratio > 6.9:1), promoting the technique for multistandard communication systems and applications

Comparison of Tuning Means

“TESLA” is an EU-funded project under Horizon 2020 research and innovation programme. The goal of TESLA project is to conduct a research on advanced technologies for future European satellite applications. The first work package of TESLA: “Technologies for satellite flexible payloads” aims to propose compact, high-performance, and efficient tuning solutions for next generation flexible satellite systems. As part of WP1, this document presents an extensive review on the different tuning techniques and means of microwave filters. This deliverable provides a general overview of tunable filters and their importance in enhancing the capabilities of communication and satellite systems. The document also discusses the mechanism of tuning for filters and its different types: capacitance tuning, inductance tuning, and capacitance-inductance tuning. A discussion of the major tuning techniques (mechanically, electrically, and magneticallybased techniques) is presented in terms of operation concepts, advantages, and limitations. Also, the different means utilized in the realization of the available state-of-the-art tunable filters are discussed in detail. Some of the new and promising tuning components and methods are also considered in the report content including ferroelectric components and resonators, liquid crystal-based tuning, and microfluidically reconfigurable filters. TESLA ESR 7 project: “Synthesis, design, and fabrication of novel tunable components for satellite communication” will use the outcome of this deliverable to propose novel tunable filters and efficient tuning configurations for future satellite communications

A novel Re-entrant Cap Tuning Technique For TM-Mode Dielectric Resonators and Filters

his paper reports a new tuning technique for TM mode dielectric resonators and filters. The proposed concept is based on the use of a hollow envelope (cap) to tune the resonant frequency instead of/in addition to the conventional intruding screw/rod-based method. The presented technique provides highly desirable advantages of tunable components including the wider tuning capabilities, simple configuration, high-power compatibility, and the improved Q factor. For proof of concept purposes, a tunable resonator is designed, fabricated, and measured. Also, a comparison with the conventional tuning technique is presented. The measured results demonstrate a wide tunability > 90% with a high Q-factor up to 3119 promoting the application of the proposed mechanism in high-performance tunable components

Miniaturized Dual-Band TM-Mode Dielectric Filter and Its Reconfiguration Capabilities

Abstract—A new miniaturized C-band dual-band dual-mode filter is reported in this paper using TM mode dielectric resonators. The filter is realized in planar topology to offer easy tuning and assembly for the applications of reconfigurable filters. High isolation between the two channels is obtained through the introduction of an inter-band transmission zero. Also, two asymmetrical transmission zeros are generated to enhance the out-of-band rejections. Both passbands can be tuned either simultaneously at the same time, or independently. A two-pole dual-band dual-mode TM dielectric filter is designed, implemented, and measured with the investigation of its tuning capabilities