Millimeter-wave Filter Research Articles

Substrate Integrated Waveguide Filter: Basic Design Rules and Fundamental Structure Features

The electromagnetic (EM) spectrum is becoming more crowded, and it is densely populated with various wireless signals and parasitic interferers in connection with communication and sensing services. Increasingly sophisticated radio-frequency (RF), microwave, and millimeter-wave filters are required to enable the selection and/or rejection of specific frequency channels. This will occur in future generations of the wireless system, such as the current hotly debated fifth-generation communication systems, where the spectral channelization of a heterostructured wide-band signals will be critical in support of a host of coexisting bandwidths or speeds and applications. Bandpass filters have been the most useful and popular types for such applications and are the most difficult to design and develop in practice. Other types of filters such as notch (stopband) and lowpass filters have also been widely used in many systems, and their design is generally perceived less critical with respect to band-pass filters. This article will focus on the presentation and discussion of bandpass filters. Design factors or parameters of filters, such as selectivity, cost, miniaturization, sensitivity to environmental effects (temperature and humidity, for example), and power handling, combined with predefined in-band and out-of-band performance metrics, are critical specifications of the design with respect to the development of RF and microwave front ends. This is indispensable for the efficient utilization of frequency spectrum resources and the cost-effective enhancement of wireless system performances.

Tunable Low-Pass MEMS Filter Using Defected Ground Structures (DGS)

In this paper, fully monolithic tunable millimeter-wave filters using defected ground structures (DGS) are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass filters were designed, fabricated, and tested. The cascaded CPW-based periodic structures, with low-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. In the first order tuning, the 3-dB cut-off frequency changes from 8.2GHz to10.5GHz, and the second order tuning is 8.2GHz to 16.8GHz. The tested results show that the pass-band ripple is less than 1.2dB and the maximal out-of-band rejection is better than 27dB. The chip size of the low-pass filter is 2.5mm×1.2mm.

A 19.2 mW, ${> 45}~{\rm dB}$ Gain and High-Selectivity 94 GHz LNA in 0.13 $\mu{\rm m}$ SiGe BiCMOS

In this letter, a high-gain and selectivity W-band LNA using 0.13 $\mu{\rm m}$ SiGe BiCMOS is proposed. A Q-enhanced cascode approach with a filter synthesis passband-forming technique was employed to achieve gain and selectivity improvement simultaneously. The amplifier achieved a gain of above 45 dB and a noise figure of 6–8.3 dB at 77–101 GHz with a power consumption of 19.2 mW. The LNA has high selectivity with a 3 dB-to-35 dB shape factor of 2.1, which is comparable with silicon-based passive millimeter-wave filters.

High-Performance Shielded Coplanar Waveguides for the Design of CMOS 60-GHz Bandpass Filters

This paper presents optimized very high performance CMOS slow-wave shielded CPW transmission lines (S-CPW TLines). They are used to realize a 60-GHz bandpass filter, with T-junctions and open stubs. Owing to a strong slow-wave effect, the longitudinal length of the S-CPW is reduced by a factor up to 2.6 compared to a classical microstrip topology in the same technology. Moreover, the quality factor of the realized S-CPWs reaches 43 at 60 GHz, which is about two times higher than the microstrip one and corresponds to the state of the art concerning S-CPW TLines with moderate width. For a proof of concept of complex passive device realization, two millimeter-wave filters working at 60 GHz based on dual-behavior-resonator filters have been designed with these S-CPWs and measured up to 110 GHz. The measured insertion loss for the first-order (respectively, second-order) filter is -2.6 dB (respectively, -4.1 dB). The comparison with a classical microstrip topology and the state-of-the-art CMOS filter results highlights the very good performance of the realized filters in terms of unloaded quality factor. It also shows the potential of S-CPW TLines for the design of high-performance complex CMOS passive devices.

Investigation of the Silicon Substrate With Different Substrate Resistivities for Integrated Filters With Excellent Performance

In this paper, the impact of substrate resistivity on the functional passive components of radio frequency (RF) complementary metal-oxide-semiconductor circuits for system-on-a-chip applications is investigated. This paper carefully extracted the dielectric constant and loss tangent of the silicon substrate with different substrate resistivities by using the aluminum coplanar waveguide. The different dielectric relaxation (cutoff) frequencies as a function of silicon substrate resistivity are compared under different requirements for substrate noise isolation, RF passive device design, and 3-dB-level RF passive device design. It is found that the new dielectric relaxation frequencies of the silicon substrate, which can be used for the implementation of 3-dB-level RF passive device design, are much higher than for the substrate noise isolation. Finally, the integrated millimeter-wave filter example, a low-pass filter with a filter cutoff frequency of fc = 31 GHz, was designed and evaluated directly on the silicon substrates with different resistivities. Experimental results of the fabricated filter showed good agreement with the simulated results and designed concept.

Design of broadside-coupled parallel line millimetre-wave filters by standard 0.18-μm complimentary metal oxide semiconductor technology

An equivalent circuit technique is used to design a class of compacted millimetre-wave band-pass filters in the standard 0.18-mu m complimentary metal oxide semiconductor (CMOS) process. Thin film microstrip is fabricated on a lossy silicon substrate to r

Miniature and tunable millimeter-wave lowpass filter with MEMS switch

In this paper, fully monolithic tunable millimeter-wave filters with tapped-line feedings are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass filters were designed, fabricated, and tested. The cascaded CPW-based periodic structures, with low-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. The measured results of the reconfigurable low-pass filter show the 3-dB cutoff frequency change from 19 to 11 GHz with very small change in the average insertion loss from 1.3 to 1.9 dB. The chip size of the low-pass is 4.0 mm × 1.6 mm.

A MINIATURIZED CMOS ON-CHIP 60-/110-GHZ DUAL BAND BANDPASS FILTER

This paper presents the design and implementation of a 60-/110-GHz millimeter-wave CMOS dual-band on-chip bandpass filter. This miniaturized dual-band filter using embedded metamaterial resonators (EMRs) and half wavelength open-loop resonators has been proposed. The EMRs are designed to have both left and right hand modes, which are simultaneously excited by the composite right/lefthanded (CRLH) structure. The half wavelength open-loop resonator is designed to provide another passband. Without using an external dual-band impedance transformer, the proposed structure can provide two transmission passbands. The dual-feed structure is presented to control the external quality factors of the first and second bands. Such an approach leads to a significant reduction for the on-chip area. Also, the frequency selectivity and impedance matching are further improved. Finally, this designed bandpass filter with the core size of 0.351 mm × 0.245 mm has been fabricated on a 0.18-μm standard CMOS process. The insertion losses at the frequencies 60 and 110 GHz are 3.5 and 3.4 dB, respectively. Up to 110 GHz, the EM simulated and measured results of the proposed filter are shown in a good agreement.

Compact Millimeter-Wave CMOS Bandpass Filters Using Grounded Pedestal Stepped-Impedance Technique

This paper presents compact CMOS millimeter-wave bandpass filters based on a new stepped-impedance technique by incorporating a grounded pedestal into the microstrip line. The characteristic impedance of a microstrip line can be effectively changed by varying both the height of pedestal and the width of line. Therefore, the stepped-impedance resonators and stubs can be realized in the compact three-dimensional forms in CMOS. Two millimeter-wave bandpass filters were designed by using the new stepped-impedance resonators and stubs. Their chip sizes are significantly miniaturized to 0.37 x 0.2 mm2, equivalently 0.012 λg2 . The first chip filter has the insertion loss of 3.1-3.4 dB in 59-71 GHz and the second filter has the insertion loss of 3.5-3.8 dB in 53-64 GHz. Both chip filters have good stopband suppression attributed from the existence of transmission zeros.

A Millimeter-Wave E-Plane Band-pass Filter using Multilayer Low Temperature Co-Fired Ceramic (LTCC) Technology

This paper presents a substrate integrated waveguide (SIW)-based millimeter-wave E-plane band-pass filter (BPF) with multilayer Low Temperature Co-fired Ceramic (LTCC) technology. The vertical metal walls of SIW and metal fins of the evanescent waveguides are realized by closely spacing metallic via-holes. A three-order Chebyshev E-plane BPF is developed and verified by full-wave simulation. The proposed filter is fabricated using LTCC technology, and a tapered line is designed as the transition between the SIW and microstrip line. Good agreement between simulated and measured results is observed.

A GCPW CMOS Bandpass Filter for Local Multipoint Distribution Systems

In this paper, an integrated millimeter-wave bandpass filter (BPF) using a standard CMOS process was designed and fabricated successfully for Local multipoint distribution systems (LMDS). Ground coplanar waveguide (GCPW) line, instead of the microstrip line, is used for realizing the proposed filter without extra transition between the CPW and microstrip, reducing the design complex. Moreover, the bandwidth of the proposed filter can be easily tuned by varying the structural parameters. The design procedure, including the electromagnetic (EM) and circuit simulation, is addressed. The measured results of the circuit have a center frequency of 39.6 GHz, an insertion loss of 5.5 dB, and a 3dB bandwidth of 33%. In addition, a transmission zero at 51.49 GHz appears near the passband edge, improving the band selectivity.

Design of Novel Millimeter-Wave Wideband Bandpass Filter Based on Three-Line Microstrip Structure

A novel three-line microstrip structure wideband bandpass filter is presented. Diamond structures of input/output ports are employed as matching circuits. Compared with the traditional three-line filter, the proposed three-line filter not only retains virtues of the traditional three-line filter, but also resolves drawbacks of it, which include discontinuities between adjacent sections, number of design parameters, and no effective matching circuits at input/output ports. To validate the proposed three-line filter, an eleven-pole millimeter-wave wideband bandpass filter is designed and fabricated. Good agreement between simulated and measured responses is observed.

Micromachined RF-Coupled Cantilever Inverted-Microstrip Millimeter-Wave Filters

This paper introduces a new concept for implementing millimeter-wave filters intended for monolithic integration. The approach uses silicon micromachining and wafer bonding techniques to create inverted-microstrip transmission lines in air and radio frequency (RF)-coupled cantilevers. A third-order filter demonstrated a measured insertion loss of only 0.54 dB at 76.5 GHz. Simple MEMS tuning of 60-GHz coupled-line resonators has also been demonstrated for the first time. This paper could form the basis for a new type of low-loss tunable distributed-element RF microelectromechanical system filter technology for millimeter-wave applications.

Ceramic Layer-By-Layer Stereolithography for the Manufacturing of 3-D Millimeter-Wave Filters

Three-dimensional (3-D) ceramic stereolithography has been developed and used to manufacture RF devices using periodic structures. To our knowledge, it is the first time that zirconia and high-performance Ba3ZnTa2O9 ceramics are used with that process to manufacture high unloaded quality factor resonant structures and bandpass filters working in the Ka-band. A theoretical study on the performances of periodic arrangements of high-permittivity structures has been carried out and has led to the manufacture of a high unloaded quality factor cavity and narrow three-pole filter (1% bandwidth) measured at a working frequency of 33 GHz

Novel compact low-loss millimeter-wave filters using micromachined overlay and inverted overlay coplanar waveguide transmission lines with defected ground structures

This paper describes two types of novel compact low-loss millimeter-wave filters using an overlay coplanar waveguide (OCPW) line for lowpass filters and an inverted overlay coplanar waveguide (IOCPW) line for bandpass filters with periodic defected ground structures (DGSs). The OCPW and IOCPW lines are utilized to reduce the conductor and the substrate dielectric loss of the transmission lines. Also, these lines can provide a wide impedance range by controlling the overlapped area. The DGSs implemented on the transmission line have the role of size reduction and harmonic suppression of the filters. The combination of transmission lines having suspended structures and DGSs can provide great potential in terms of compact size, band rejection property and low-loss characteristics. The proposed filters are fabricated by using a micromachining technology and their RF performances are measured and analyzed. One of the proposed filters is a lowpass filter with a five-section stepped impedance topology having a periodic high–low impedance section. In this filter, the low impedance section is composed of the OCPW line with dumbbell-shaped DGSs and its length can be reduced by 52.7% compared to the OCPW line without DGSs. The measured insertion loss of this filter is lower than 0.2 dB up to 9 GHz, and significant spurious bands are not observed up to 40 GHz, resulting in a wide stop band. The other work that is presented here deals with a pi-shaped bandpass filter. This filter consists of three high impedance sections and two low impedance sections, and the line length of the high impedance section can be reduced by using the IOCPW line with spiral-shaped DGSs. The measured center frequency of the fabricated filter is 19 GHz, and the passband loss is 2.3 dB at the measured center frequency. The use of DGSs on the transmission line also enables us to suppress effectively the third-order harmonic component at 57 GHz.

A Low Loss Multi-Layer Dielectric Waveguide Filter for 60-GHz System-on-Package Applications

For V-band applications, this paper presents a fully embedded multi-layer dielectric waveguide filter (DWGF) with very low insertion loss and small size, which does not need any more assemblies such as flip-chip bonding and bond wires. The top and bottom plane are grounded, and therefore, although we make a metal housing, there will be no resonance occurrences. Especially, the proposed structure is very suitable for MMICs interconnection because the in/output pads consist of conductor backed co-planar waveguide (CBCPW). The filter is formed incorporating metallized through holes in low temperature co-fired ceramic (LTCC) substrates with relative dielectric constant of 7.05. The total volume of the filter including transitions is 4.5 mm × 2.65 mm × 0.4 mm. A fabricated DWGF with four transitions shows an insertion loss and a return loss of 2.95 dB and less than 15 dB at the center frequency of 62.17 GHz, respectively. According to the authors' knowledge, the proposed filter shows the lowest insertion loss among the embedded multi-layer millimeter-wave filters ever reported for 60 GHz applications.

Compact Millimeter-wave filters using distributed capacitively loaded CPW resonators

In this paper, a method for reducing the size of coplanar-waveguide (CPW) resonators, used in the design of compact bandpass filters, is presented. This is accomplished by incorporating a distributed array of capacitive loads along a resonant CPW line. Design of a miniaturized bandpass filter using capacitively loaded CPW resonators, which are inductively coupled, is presented. Inductively coupled bandpass filters with the proposed capacitively loaded CPW line resonators are designed and a size reduction of 25%, compared with filters using a standard CPW line resonator, is demonstrated. It is shown that, through this size reduction, the insertion loss is minimally increased (<0.4 dB). A hybrid algorithm, combining the method of moments (MOM) and circuit simulation is used to facilitate design process. Few filters using this technique are designed, fabricated, and measured at W-band. An excellent agreement between the simulation and measurement responses of these filters is presented.

Implementation of millimetre-wave filter using wafer transfer technology

A novel millimetre-wave CPW bandpass filter implemented with the wafer transfer technology has been realised. An insertion loss of 1.2 dB, a return loss of 16 dB centred at 26 GHz and a fractional bandwidth of 12% have been achieved. Good agreement has been achieved between the measured data and simulated results.

Millimeter-wave MEMS tunable low pass filter with reconfigurable series inductors and capacitive shunt switches

In this paper, a new type of reconfigurable inductor is proposed for mm-waves based on the reconfiguration of slow-wave coplanar waveguide (CPW) lines using multiple-contact switches. It is then employed together with micro-electro-mechanical systems (MEMS) capacitive shunt switches to realize a reconfigurable low-pass filter, where the values of both inductors and capacitors are changed independently to achieve optimum filter characteristics. The measured 3-dB cut-off frequency of the reconfigurable low-pass filter changes from 53 GHz to 20 GHz while maintaining Tchebycheff low-pass prototype characteristics. The out-of-band rejection characteristics are also improved in this way. To our knowledge, this is among the first demonstrations that both types of MEMS contact switches and capacitive switches are used simultaneously to construct a monolithic tunable filter with independent L/C controlling capability.

Reconfigurable millimeter-wave filters using CPW-based periodic structures with novel multiple-contact MEMS switches

In this paper, fully monolithic reconfigurable millimeter-wave filters are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass and band-pass filters were designed, fabricated, and tested. Three cascaded CPW-based periodic structures, with low-pass and band-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. By using the multiple-contact MEMS switches, the insertion loss can be reduced and the operating frequency ranges are extended to millimeter-waves with little increase of loss. Additionally, the number of the switching elements has been reduced and the bias-decoupling circuits are not required, resulting in a very small chip size. The measured results of the reconfigurable low-pass filter show the 3-dB cutoff frequency change from 67 to 28 GHz with very small change in the insertion loss from 0.32 to 0.27 dB. The center frequency of the reconfigurable band-pass filter is tuned from 55 to 20 GHz, and the measured 3-dB cutoff bandwidth changed from 32 to 12 GHz, while the average insertion loss changed from 1.27 to 1.61 dB. The chip size of the low-pass and band-pass filter including dc bias line is 1.2 mm /spl times/ 1.5 mm and 1.2 mm /spl times/ 4.5 mm, respectively.