Showing papers on "Waveguide filter published in 2017"

Dual-Mode Substrate Integrated Waveguide Filter With Flexible Response

Abstract: This paper proposes a novel dual-mode substrate integrated waveguide (SIW) filter technique. Based on the conventional dual-mode SIW structure, further investigation is performed. Multiple transmission zeros can be obtained at one side or both sides of the passband for an SIW cavity. Therefore, flexible design and high performance response can be available for dual-mode SIW filter. A dual-mode SIW bandpass filter with quasi-elliptic response and a dual-mode SIW diplexer with asymmetric channel response are simulated, fabricated, and measured to demonstrate and verify the novel property.

Bandpass Class-F Power Amplifier Based on Multifunction Hybrid Cavity–Microstrip Filter

Abstract: This brief presents a filter-integrated high-efficiency class-F power amplifier (PA). The hybrid cavity–microstrip filtering circuit is employed not only to realize output impedance matching and the third-harmonic manipulation but also to provide high-selectivity bandpass responses. To fulfill the requirements of high-efficiency class-F PAs, cavity resonators and microstrip feeding structures are involved, and their benefits are fully exploited. The metal cavity resonator features a high $Q$ value and, thus, low loss in the passband, resulting in high efficiency. Moreover, metal walls of cavities act as heat sink for the transistor. The microstrip feeding structures are used to improve the skirt selectivity and manipulate the third harmonic. Moreover, it features easy integration with the transistor, and thus, the transition between cavity and microstrip lines is eliminated. The hybrid filter is characterized based on filter synthesis theory. Complex impedance conversion analysis is carried out to guide the impedance transformation from 50 $\Omega$ to a complex one desired by the transistor. For demonstration, a filtering PA operating at 2.4 GHz is designed and measured. It exhibits both high-selectivity bandpass responses and good PA performance with maximum power-added efficiency of 70.9% at 40.8-dBm output power.

Enhancing the Performance of Waveguide Filters Using Additive Manufacturing

Abstract: This paper describes the development of resonator and coupling architectures that enhance the insertion loss and far out of band rejection of single-mode waveguide filters. The inherent geometrical freedom of 3-D additive manufacturing techniques is exploited to realize complex geometries monolithically. It also has the added benefit of reduced manufacturing lead time. Resonator and coupling structures using complex geometries are introduced and examples of manufactured direct-coupled-cavity filters are given. Analysis and measurements show excellent agreement. The suitability of the manufacturing process for standard and complex geometries is discussed.

Electrical-Thermal Co-Simulation for Analysis of High-Power RF/Microwave Components

Abstract: An electrical-thermal co-simulation based on the finite element method is presented for analysis of high-power RF/microwave circuits. The co-simulation integrates a full-wave electromagnetic analysis and a transient thermal analysis through an iterative scheme, and is devised for the design and analysis of RF/microwave circuits operated at high frequencies and high power levels. To enhance the efficiency in solving large-scale problems, a domain decomposition scheme called the finite element tearing and interconnecting and an adaptive time-stepping scheme based on the algorithm of proportional-integral-derivative control are incorporated into the co-simulation. Temperature stability analysis is performed with the proposed co-simulation for a matching network in high-power RF amplifiers and for a substrate integrated waveguide filter.

WR-3 Band Quasi-Elliptical Waveguide Filters Using Higher Order Mode Resonances

Abstract: Two types of WR-3 band quasi-elliptical waveguide bandpass filters (BPFs) using higher order mode resonators are presented based on physical cross coupling and modal bypass coupling, respectively. Under the situation of physical folded structure, a TE102-mode in an oversized waveguide resonator is utilized to reverse the magnetic field direction of main path to implement a negative cross coupling (Filter-I). Limited to the structure of Filter-I itself, the simulated 3 dB fractional bandwidth (FBW) of 8.5% is slightly narrower than desired 10% FBW. For the other case, two TE101/TE201 overmode resonant cavities with suitable input and output coupling locations are employed to generate two transmission zeros in the vicinity of the passband through modal bypass couplings (Filter-II). The benefit from the realization of the wideband source and load couplings in the fringe first and fourth oversized cavities is that the FBW of 10% is achieved in the Filter-II. The two BPFs fabricated by computer numerical control milling technology exhibit an insertion loss (IL) of about 0.7 dB and a 3 dB FBW of 8.77% centered at 257.7 GHz (Filter-I), IL of around 0.5 dB, and FBW of 9.83% with center frequency of 256.3 GHz (Filter-II), which are all in good agreement with the simulations. The performance of the two BPFs based on one or two oversized waveguide resonators is highlighted comparing with the reported similar terahertz waveguide filters.

Compact Waveguide Dual-Band Filters and Diplexers

Abstract: This paper presents a new class of dual-band filters and diplexers, realized based on dual-band resonators. The proposed dual-band filter and diplexer do not require junctions and can achieve equivalent performance with fewer cavities, thus offering a significant reduction in size compared with traditional approaches. The concept is potentially applicable to most dual-band cavities and is demonstrated in this paper using elliptical and rectangular waveguide cavities. The first design is an inline structure employing elliptical cavities, whereas the second design is implemented through a unique layout that combines the use of dual-band and single-band rectangular cavities. The result is a group of highly compact dual-band filters and diplexers that offer increased Q and an improved spurious-free window. To verify the concept, an eighth-order Ku-band elliptical dual-band filter and a fourth-order Ku-band rectangular diplexer are designed, manufactured, and tested to allow comparisons with traditional designs.

Additive manufacturing of Ku/K-band waveguide filters: a comparative analysis among selective-laser melting and stereo-lithography

Abstract: This study describes an experimental research activity on the manufacturing of passive waveguide components by means of two additive technologies, namely the selective-laser melting and the stereo-lithography processes. The former is a power-bed fusion process, for which aluminium, titanium, and steel powders have been considered in this study. The latter is based on the photopolymerisation of a resin vat. This technology has been applied in conjunction with an acrylonitrile–butadiene–styrene-like polymer and a subsequent electrolytic copper plating for the metallisation of the internal channels. Wideband filters operating in Ku/K band have been developed as benchmarks, for which detailed comparisons between simulations and measurements are reported.

Substrate Integrated Waveguide Filters Based on a Dielectric Layer With Periodic Perforations

Abstract: This paper presents a novel class of substrate integrated waveguide (SIW) filters, based on periodic perforations of the dielectric layer. The perforations allow to reduce the local effective dielectric permittivity, thus creating waveguide sections below cutoff. This effect is exploited to implement immittance inverters through analytical formulas, providing simple design rules for the direct synthesis of the filters. The proposed solution is demonstrated through the design and testing of several filters with different topologies (including half-mode SIW and folded structures). The comparison with classical iris-type SIW filters demonstrates that the proposed filters exhibit better performance in terms of sensitivity to fabrication inaccuracies and rejection bandwidth, at the cost of a slightly larger size.

Ka-band compact and high performance bandpass filter based on multilayer air-filled SIW

Abstract: A substantial reduction of Substrate Integrated Waveguide (SIW) insertion loss can be achieved through the use of air as dielectric instead of usual dielectric material. However, Air-Filled SIW (AFSIW) circuits exhibit larger footprint compared to their dielectric-filled counterparts. In this letter, a compact multilayer AFSIW bandpass filter is proposed to realize both high performance and small footprint. For demonstration purpose, a Ka-band multilayer 4th order AFSIW bandpass filter has been designed and fabricated. Measured and simulated results are in good agreement. Retro-simulations, taking into account fabrication tolerances, are also presented. Finally, a performance comparison with other multilayer technologies is presented.

Quarter-mode circular cavity substrate integrated waveguide filtering power divider with via-holes perturbation

Abstract: A compact filtering power divider composed of two quarter-mode circular cavities based on the substrate integrated waveguide is proposed. Two extra perturbing via-holes added in each side of the quarter-mode circular cavity achieve a selective bandpass filtering response and improve the performance of the upper stopband. The proposed FPD operates at 9.1 GHz with a 3 dB fractional bandwidth of 19.8%. The insertion loss in operating band is <; 1.6 dB and the input return loss is better than 16 dB. The amplitude and phase imbalances between the two outputs are measured better than 0.6 dB and 3.5°, respectively. The measured results exhibit good agreement with the simulated ones.

275–500 GHz Waveguide Diplexer to Combine Local Oscillators for Different Frequency Bands

Abstract: Development of local oscillator (LO) sources based on amplifier multiplier chains (AMC) have steadily progressed in recent years, with more power and more bandwidth available at mm and sub-mm wavelengths. Recent radio astronomy receiver projects are, however, aiming at duplicating the RF bandwidth, with fractional bandwidth around 60%, even at frequencies as high as 500 GHz. In particular, National Astronomical Observatory of Japan (NAOJ) is developing wideband SIS mixers for a combined Atacama Large Millimeter/Submillimeter Array (ALMA) band 7 and 8 receiver, extending from 275 to 500 GHz. Currently, LO sources are not available for such a wide frequency band. To solve this problem, we have developed a waveguide diplexer to combine the output power of two different LO sources for ALMA band 7 (275-373 GHz) and band 8 (385-500 GHz). The proposed waveguide diplexer is based on hybrid couplers and waveguide filters. Two units of the designed component have been fabricated and S-parameters have been measured with good agreement with simulations. Initial tests to combine the LO power of band 7 and 8, LO sources at cryogenic temperature to pump a wideband 275-500 GHz SIS mixer have been successful.

Bandpass Filters Designed by Transmission Zero Resonator Pairs With Proximity Coupling

Abstract: The concept of transmission zero resonator pair (TZRP) is used in this paper. Based on this TZRP, a new method to induce a passband is demonstrated, by which different types of bandpass filters can be designed. The proposed TZRP is structured by a pair of resonators with different resonant frequencies, which lead not only to two transmission zeroes, but also to a transmission pole between them. Passband filters can then be built by designing the proximity coupling between the TZRPs, as the TZRP works as a basic resonant element. The passband of these filters can be flexibly controlled by the resonators of TZRPs, which determine the locations of the transmission zeroes and poles. By carefully allocating the transmission zeroes, high selectivity and large out-of-band rejection can be realized. This design method is applied to design filters in two different transmission media, namely, microstrip line and rectangular waveguide. Simulated and measured results demonstrate the effectiveness of this new approach of bandpass filter design. The designed filters have the properties of small size, easy fabrication, low cost, and low loss.

Microwave Voltage-Controlled Oscillator With Harmonic-Suppressed Stepped-Impedance-Resonator Filter

Abstract: This brief proposes a new low-phase-noise microwave voltage-controlled oscillator (VCO) with a harmonic-suppressed stepped-impedance-resonator (SIR) filter. Since the filter is synthesized by multiple resonators, it can provide a high-quality factor to improve the phase-noise performance. In addition, the harmonic-suppressed property of the filter adopted in this brief can alleviate the noise contributed from the oscillation harmonics. By applying the two techniques mentioned, the proposed VCO is designed at 2.4 GHz with a three-pole Butterworth filter, which is synthesized by the parallel transmission-line SIRs to reduce the circuit size. The proposed VCO using a three-pole filter has a measured phase noise of −147 dBc/Hz at 1-MHz offset frequency with a corresponding figure-of-merit of −203.18 dBc/Hz.

Micromachined multilayer bandpass filter at 270 GHz using dual-mode circular cavities

Abstract: In this paper, we present a microfabricated fourth-order sub-THz WR-3.4 bandpass waveguide filter based on TM110 dual-mode circular-shaped cavity resonators. The filter operates at the center frequency of 270 GHz with fractional bandwidth of 1.85% and two transmission zeros are introduced in the upper and in the lower stopband using a virtual negative coupling. The microchip filter is significantly more compact than any previous dual-mode designs at comparable frequencies, occupying less than 1.5 mm2. Furthermore, in contrast to any previous micromachined filter work, due to its axially arranged interfaces it can be directly inserted between two standard WR-3.4 rectangular-waveguide flanges, which vastly improves system integration as compared to previous micromachined filters; in particular no custom-made split-block design is required. The cavities are etched in the handle layer of a silicon-on-insulator (SOI) wafer, and coupling is realized through rectangular slots fabricated in the SOI device layer. Couplings of the degenerate modes in one cavity are facilitated by means of small perturbations in the circular cavity shapes. The measured average return loss in the passband is −18 dB and worst-case return loss is −15 dB, and an insertion loss of only 1.5 dB was measured. The excellent agreement between measured and simulated data is facilitated by fabrication accuracy, design robustness and micromachined self-alignment geometries.

A Hybrid Miniaturized-Element Frequency Selective Surface With a Third-Order Bandpass Response

Abstract: A new architecture for a miniaturized-element frequency selective surface (MEFSS) capable of providing a third-order bandpass response is presented and experimentally verified. The proposed MEFSS consists of three metal layers separated from one another by two dielectric substrates. The exterior metal layers are nonresonant inductive wire grids, while the center layer is a hybrid resonator composed of an inductive wire and an I-shaped resonator. The exterior metal layers and the dielectric substrates act as two inductively coupled series resonators sandwiching the hybrid resonator layer in the middle. This results in a filter with a third-order bandpass response that can also provide an out-of-band transmission null at a frequency higher than that of the main passband. An equivalent-circuit-based synthesis procedure for this MEFSS is also presented in this letter that allows for designing the FSS from its desired system-level performance indicators (e.g., center frequency of operation, bandwidth, etc.). The validity of this design procedure is verified by presenting a design example and conducting full-wave electromagnetic simulations. Finally, an experimental proof-of-concept demonstration is performed by characterizing the unit cell of this MEFSS designed to operate in a WR-112 waveguide environment.

Substrate integrated waveguide dual-band filter with wide-stopband performance

Abstract: The first substrate integrated waveguide dual-band bandpass filter with wide-stopband performance is presented. This filter is synthesised and designed with fourth-order Chebyshev responses and identical fractional bandwidths for the two passbands centred at 12 and 16 GHz. Multiple spurious resonances have been intrinsically suppressed by introducing the harmonics-staggered technique and the centred coupling windows. Good agreements can be observed between the measured and simulated results, and better than 25-dB rejection level up to 2.05 f 1 has been successfully achieved.

Analysis of 220-GHz Low-Loss Quasi-Elliptic Waveguide Bandpass Filter

Abstract: A 220-GHz low-loss and wideband waveguide bandpass filter with fourth-order quasi-elliptic response is presented and analyzed in this letter. An electric cross-coupling realized by easily manufactured capacitive iris is introduced in the classical folded quadruplet topology. The prototype fabricated by conventional computer numerical control (CNC)-metal-milling technology exhibits meaningful results of an insertion loss of around 0.6 dB and a 3-dB fractional bandwidth of 9.8% centered at 214.3 GHz, which are in excellent agreement with the simulated ones. The effects of tolerance and surface roughness on the filter performance are discussed in detail. All the results indicate that the present CNC process can meet the accuracy and roughness requirement of such waveguide filter in WR-4 band.

Realising advanced waveguide bandpass filters using additive manufacturing

Abstract: This study describes the realisation of an advanced waveguide bandpass filter using shaping of the resonator and coupling structures to enhance the radiofrequency performance. Additive manufacturing's inherent geometrical freedom is exploited in these structures. The method of creating a good starting point for optimisation using electro-magnetic (EM) simulation tools is compared with standard techniques for waveguide filters. A simple filter is given as an example to demonstrate the suitability of the structures and manufacturing techniques followed by a more advanced filter function. Simulations are presented and compared with both measured performance and rectangular waveguide realisations. The advantages and disadvantages of the manufacturing process and complex geometries are discussed.

Dual-Mode Dual-Band Bandpass Cavity Filters With Widely Separated Passbands

Abstract: A dual-mode dual-band cavity is proposed for the integration of compact dual-band filters with widely separated passbands. The basic structure is a cavity working on two distinct dual-modes, realizing a four-pole dual-band filtering function. An intermediate structure is also designed to validate coupling between dual-band cavities. Finally, two dual-mode dual-band cavities are coupled together for implementing an eight-pole filter with two passbands at 5 and 7.5 GHz, respectively. Prototypes are fabricated and measured for validating all designs, showing the relevance of the proposed concept.

Two-Layered Substrate Integrated Waveguide Filter for UWB Applications

Abstract: In this letter, an ultra-wideband (UWB) substrate integrated waveguide (SIW) filter using ridge resonator is presented. The filter relies on designing SIW ridge resonator. The comb-shaped resonator makes the filter to be realizable for UWB characteristics. The upper edge of the passband can easily be adjusted by the width of small rod in the ridge resonator. A parametric study is done to show how bandwidths can be adjusted. The measurement results show that a reflection coefficient of better than −14 dB has been obtained over the frequency band of 3.1–10.6 GHz. The maximum insertion loss in passband is almost 1 dB. Moreover, a stopband from 11.4 to 17.4 GHz with a suppression magnitude better than 47 dB has been achieved.

Spoof surface plasmonic waveguide devices with compact length and low-loss

Abstract: A spoof surface plasmon polaritons (SSPPs) waveguide structure with periodic T-grooves is proposed and investigated in this paper. Compared to the conventional plasmonic waveguide with periodic rectangular-grooves, the proposed waveguide support the guided SSPPs wave with enhanced propagation confinement. Moreover, the waveguide with T-grooves can achieve 39.4% decrease in length compared with the rectangular-grooves waveguide. The propagation properties of the SSPPs with enhanced confinement are able to improve by adjusting the shape dimensions of T-grooves. The effects of bend radius of 90° T-grooves waveguide on propagation performance are analyzed, and the good transmission characteristics of waveguides with small bend radius are verified. The experimental verifications of the T-grooves plasmonic waveguide filter and 3 dB power divider in microwave region are realized, S21-parameter of waveguide filter is very close to 0 dB from 0 GHz to 5.6 GHz. And 3 dB power divider achieves very good power equipartition from 0 GHz to 5.5 GHz.

Continuously Tuned Ku-Band Cavity Filter Based on Dielectric Perturbers Made by Ceramic Additive Manufacturing for Space Applications

Abstract: This paper presents a concept of a tunable cavity resonator composed of a resonating cavity and a dielectric perturber. This tunable resonator is designed and measured to prove the tuning mechanism obtained by varying the angle of rotation of the perturber. A rotation from 0 to 90 produces a tuning ratio of 1:1.25, i.e., a tuning range of 22.2% around 11.5 GHz while maintaining an unloaded Q factor between 1500 and 2300. After this first experimental validation, a third-order bandpass filter is then designed and measured using the same base principle. Using a single mechanical movement, all three resonators’ perturbers are synchronously rotated to create a third-order Chebyshev bandpass filter maintaining a 516±38-MHz bandwidth (for a return loss better than 10 dB) from 9.915 to 12.189 GHz. A 20.6% tuning range is then obtained at approximately 11 GHz with an estimated Q factor from 1400 to 2150. These performances have been obtained by using specifically shaped dielectric perturbers, which have been made by a ceramic additive manufacturing (AM) process (stereolithography). This technology has enabled the perturbers’ specific geometries and embedded supporting elements to be feasible. A sixth-order Chebyshev bandpass filter has also been theoretically proposed using full wave simulations.

Size-reduced dual-band HMSIW cavity filters loaded with double-sided SICSRRs

Abstract: Two size-reduced dual-band half-mode substrate integrated waveguide (HMSIW) cavity filters double-side-loaded with the conventional and stepped-impedance complementary split-ring resonators (SICSRRs) are presented. The SICSRR can exhibit larger equivalent electrical length than the conventional CSRR and thus provides a method to implement size-miniaturisation. By loading both CSRR and SICSRR into the two sides of the HMSIW cavity, a dual-band resonator is formed. Since sizes of the CSRR and SICSRR on the two sides are controlled independently, the two passbands of the proposed resonator can be tuned flexibly. With the proposed HMSIW-DS-SICSRR cavity resonators, two dual-band filters are realised. Compared to other dual-band SIW filters, the two proposed dual-band filters can achieve sized-reduction about 48.5 and 50%, with the measured results in good agreement with the simulated ones.

Balanced hybrid SIW–CPW bandpass filter

Abstract: This Letter proposes a balanced hybrid substrate-integrated waveguide (SIW)–coplanar waveguide (CPW) bandpass filter, which combines a hybrid SIW–CPW filter and a balanced structure for the first time. High performance common mode suppression can be achieved with high quality factor, compact size, and quasi-elliptic differential mode response.

An Alternate Circuit for Narrow-Bandpass Elliptic Microstrip Filter Design

Abstract: This letter demonstrates the dual transmission zeros (TZs) of bandpass elliptic prototype filters that can be directly implemented with two resonators in microstrip. An experimental filter based on the proposed alternate circuits is designed and fabricated. In order to improve the rejection of stopband, two additional TZs are introduced to the proposed filter. By means of directly implementing an elliptic bandpass filter in microstrip, the insertion loss of the presented filter can be less than 0.8 dB, and the $\Delta {f}_{3~\mathrm {dB}}/\Delta {f}_{20~\mathrm {dB}}$ result is better than 0.583, which means the proposed filter has a good selectivity.

W-band waveguide filter based on large TM120 resonators to ease CNC milling

Abstract: A W-band waveguide bandpass filter, based on coupled TM 120 resonators, fabricated using CNC milling, is presented. TM 120 resonators are superior to conventional TE 101 resonators, in terms of having a larger size and reduced aspect ratio, which facilitates the fabrication process as well as allowing larger tolerances in the milling process. This type of resonator also offers a high unloaded quality factor, and ultimately yields a small insertion loss for the filter. A W-band filter, with a centre frequency of 100 GHz and a fractional bandwidth of 6%, is designed using four TM 120 resonators and constructed from three brass shims which directly fit to the waveguide flanges. This filter is measured to have a median passband insertion loss of 0.5 dB and a return loss better than 13 dB across the whole passband.

Realisation of carved and iris groove gap waveguide filter and E-plane diplexer for V-band radio link application

Abstract: The gap waveguide technology is a promising candidate as a cost-effective and low-loss platform for realizing microwave devices particularly at frequencies higher than 40GHz. In this study, two types of groove gap waveguide filters and also a diplexer are presented. Coupling mechanism of these filters is based on carving on the pin plate and iris between adjacent cavities. Two fifth-order Chebyshev filters are realised at 62.5GHz. The proposed diplexer consists of RX and TX iris groove gap waveguide filters at the centre frequency of 59.5 and 62.5GHz and an E-plane groove gap waveguide T-junction. The required transition of the groove gap waveguide to WR-15 is designed and used as an input port of the filters. Moreover, E-plane groove gap waveguide T-junction is designed as the connecting part of the groove gap waveguide filters to the WR-15 antenna port. Finally all parts are integrated. The proposed diplexer is manufactured in aluminium by sawing and milling and then silver plating is done. The RX and TX passbands of the diplexer is around 1.7 and 2.4% with the measured return loss better than 13.6dB and minimum insertion loss of 0.9 and 0.8dB, respectively.

3-D Printed Customizable Inserts for Waveguide Filter Design at X-Band

Abstract: This letter presents the design of a customizable 3-D printed insert that can be placed into a standard WR-90 waveguide to realize an inline waveguide filter. These 3-D printed inserts have a significantly lower manufacturing cost and turnaround time compared to the conventional solid copper or bronze waveguide. A two-pole X-Band filter insert has been designed to demonstrate this unique approach. A Stratasys Fortus 400mc 3-D printer is used to print the exchangeable waveguide inserts with support material that is then removed using a basic lye solution. A seed layer of nickel is then spray coated on, and used to electroplate the inserts with copper. Measured results are in good agreement with simulation results for the two-pole bandpass filter with less than 1.05-dB insertion loss over X-Band. The weight of these inserts electroplated with copper is only 6.65 g. The ease and flexibility of this approach provides an excellent option for tuning and customizing filter designs with a fast turnaround using 3-D printing manufacturing technology.

A New Synthesis and Design Method for Wideband Bandpass Filters With Generalized Unit Elements

Abstract: A new synthesis and design method for wideband bandpass filters has been proposed using the concept of generalized unit elements (GUEs). The synthesis starts with a lumped-element LC circuit, which is obtained by some well-known circuits and classic methods, such as the ladder-type circuit and the coupling matrix method. A GUE is an equivalent circuit, which is represented by either a coupled LC circuit or a section of the transmission line coupled by stubs. In this view, an LC circuit is transformed into the transmission line circuit directly via a general network of a GUE. This contributes to the key idea behind the synthesis procedure. Detailed analysis on the GUE and its equivalent circuits are discussed in terms of the equivalent characteristic impedance and the extended Richard’s transformation. Based on these two variables, frequency and constant mapping functions are proposed to explicitly obtain characteristic impedances in the transmission line circuit. In the final part, three prototype filters, namely, the classic Chebyshev ladder-type filter, the general box-shaped Chebyshev filter of symmetrical filtering responses, and the cascaded trisection filter in an asymmetrical transmission zero distribution are designed and fabricated, respectively. All the experimental results agree well with the predicted ones and thus it verifies the proposed synthesis and design method.

An X-band lightweight 3-D printed slotted circular waveguide dual-mode bandpass filter

Abstract: This paper presents an X-band eighth-order quasi-elliptic circular waveguide dual-mode bandpass filter (BPF) that is manufactured using a fast and low-cost stereolithography-based 3-D printing technique. The 3-D printed filter has advantages of a more convenient integration free of either assembly or post fabrication tuning and furthermore a lightweight of 111 g. A ceramic-filled resin with an enhanced thermal handling capability is used as the filter's building material, which makes the filter capable of operating under much higher temperatures than the one made from ordinary photosensitive resins. Surface metallization of the filter is realized by a layer of electroless plated copper. In the measured passband 8.01–8.44 GHz, the filter exhibits a return loss over 10 dB and a corresponding insertion loss of 0.32–0.68 dB.