Compact UWB bandpass filter with dual‐notch bands using asymmetric tri‐section stepped impedance resonator

In this study, a novel high selective UWB band pass filter (BPF) with dual notch band is presented. UWB BPF is realized using stub‐loaded multiple‐mode resonator (MMR). The MMR is constructed by loading a quintuple mode open stub at the centre in an asymmetric tri‐section stepped impedance resonator (ATSSIR). Five modes, including two odd modes and three even modes, placed within UWB band. Two transmission zeros generated by the fractal stub improve the passband selectivity greatly. Two half wavelength long fractal Hilbert resonators are embedded near I/O line to achieve notch bands at 5.1 and 5.9 GHz. Aperture‐backed interdigital coupled‐lines are implemented to improve the coupling. The proposed prototype is fabricated and tested. The measured insertion loss is observed to be within 1.5 dB over the passband. By virtue of two transmission zeros (TZs), on either side of the passband, at 5.1 and 5.9 GHz, respectively, the passband selectivity is achieved with measured roll‐off factor at around 34 dB/octave. The out‐of‐band rejection of the filter is greater than 22 dB up to 18 GHz. The simulated results are in good agreement with the measured responses.     

A compact balun‐diplexer using interdigital line resonators

A novel compact balun‐diplexer applying new interdigital line resonators (ILRs) is presented in this article. It is found that the proposed ILR can not only reduce circuit size and but also realize high common mode rejection in differential mode operation frequency. By properly converting the symmetric four‐port balanced bandpass filter (BPF) to a three‐port device, a balun BPF with high selectivity and compact size are accomplished using ILRs. Then, the balun‐diplexer can be realized by combining two well‐designed balun filters with two 50 Ω transmission lines. The demonstrated balun‐diplexer with operation at 1.8 and 2.45 GHz have been designed, fabricated, and measured. Excellent performances have been observed. Specifically, 0.4 dB in‐band amplitude error, 1.8 in‐band phase error, more than 50 dB selectivity and 45 dB isolation are obtained. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:485–489, 2015.     

LTCC‐based monolithic system‐in‐package (SiP) module for millimeter‐wave applications

A miniature LTCC system‐in‐package (SiP) module has been presented for millimeter‐wave applications. A typical heterodyne 61 GHz transmitter (Tx) has been designed and fabricated in a type of the SiP module as small as 36 × 12 × 0.9 mm³. Five active chips including a mixer, driver amplifier, power amplifier, and two frequency multipliers were mounted on the single LTCC package substrate, in which all passive circuits such as a stripline (SL) BPF, 2 × 2 array patch antenna, surface‐mount technology (SMT) pads, and intermediate frequency (IF) feeding lines have been monolithically embedded by using vertical and planar transitions. The embedded SL BPF shows the center frequency of 60.8 GHz, BW of 4.1%, and insertion loss of 3.74 dB. The gain and 3‐dB beam width of the fabricated 2 × 2 array patch antenna are 7 dBi and 36 degrees, respectively. The assembled LTCC 61 GHz Tx SiP module achieves an output power of 10.2 dBm and an up‐conversion gain of 7.3 dB. Because of the integrated BPF, an isolation level between a local oscillation (LO) and RF signal is below 26.4 dBc and the spurious level is suppressed by lower than 22.4 dBc. By using a 61 GHz receiver (Rx) consisting of off‐the‐shelf modules, wireless communication test was demonstrated by comparing measured IF spectrums at the Tx and Rx part.     

Miniaturized frequency‐agile bandpass filter integrated single‐pole double‐throw switch

This article presents a miniaturized frequency‐agile bandpass filter (BPF) integrated single pole double throw (SPDT) switch using common LC resonator. The BPF‐integrated on‐sate channel is constituted by the capacitively coupled LC resonators with loaded varactor diodes and reverse‐biased p‐i‐n diodes. The off‐state channel with high suppression is built when the p‐i‐n diodes loaded LC resonators is forward‐biased. As an example, a frequency‐agile BPF‐integrated SPDT switch with constant 3‐dB fractional bandwidth of 18.4% is designed. Its fabricated circuit area including bias circuit but excluding feeding lines is 0.105 λ_g × 0.079 λ_g. Measured results show that its 3 dB operating frequency bandwidth covers from 0.499 to 1.077 GHz with in‐band insertion loss varying from 4.15 to 3.15 dB. Off‐state suppression better than 37.8 dB, port‐to‐port isolation better than 51.1 dB, and good return loss can be also observed.     

Design and performance analysis of double cantilever type capacitive shunt RF MEMS switch

This paper presents a novel structure of capacitance shunt type RF switch for 5G applications. The proposed RF MEMS switch is having Cantilever type designed with optimized dimensions to operate in V-band applications. The electromechanical analysis is done by using the COMSOL tool. The actuation voltage of the proposed switch is 10.5 V with the air gap of 1 µm and gold as a beam material. The proposed switch with the meanders and perforations show the scattering parameters in HFSS software such as insertion loss (S₁₂) of − 0.033 dB and return loss (S₁₁) less than − 48 dB and the isolation (S₂₁) calculated in off-state as − 62 dB at 50 GHz.

     

Band‐pass filter design using modified CSRR‐DGS

In this article, a novel compact band‐pass filter (BPF) with sharp cutoffs and a wide stop‐band is presented. The BPF is basically designed by cutting a modified complementary split‐ring resonator (CSRR) from the ground of two separated microstrip feed lines and has a 71% fractional bandwidth from 4.1 to 9 GHz. Because of the high insertion loss, the designed filter should be packed in a metallic cavity that has undesirable resonances in the stop‐band of the BPF. For eliminating cavity resonances, an evolutionary optimization technique based on changing the pixels of the CSRR defected ground structure is used. A prototype of the final structure obtained from the optimization technique is fabricated. The measurement results show that the optimized filter have a pass band from 4 to 8 GHz with a rejection better than 15 dB from 4 to 15 GHz. The designed filters have compact dimensions of 12 × 12 × 0.787 mm³. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:544–548, 2014.     

A Ka band microstrip to waveguide transition using a quasi‐triangle probe

In this article, a new Ka band microstrip to waveguide transition with combination of electric and magnetic coupling is introduced by using a quasi‐triangle structure. Consequently, the length of the proposed transition has been significantly diminished. A back‐to‐back prototype was fabricated based on the optimized dimensions to validate the design concept. The measured and simulated results are in a good alignment. The experimental results show that the return loss is better than 14.8 dB across the frequency range of 32‐40 GHz with an insertion loss of lower than 0.9 dB. The conversion efficiency for the single transition, therefore, is larger than 90.5%. Because of its broad operation bandwidth, low insertion loss, and compact size, the proposed embedded transition could find wide applications in most modern miniaturized MMIC devices and systems.     

A metasurface‐based slit‐loaded wideband circularly polarized crossed dipole antenna

A metasurface‐based low‐profile crossed dipole antenna with wide circularly polarized bandwidth for 2.45 GHz ISM band wireless communications is proposed and fabricated in this article. Consisting of four slit‐loaded rectangular patches, the double‐sided printing crossed dipoles are fed by a pair of vacant‐quarter printed rings which circularly polarized (CP) radiation could be generated. With slits loaded, by properly combining the fundamental mode of the two inverted L‐shaped dipole, the slot mode and extra resonance generated by the AMC surface, a wideband circularly polarized operation can be obtained. After optimization, the final design with an overall size of 0.44λ₀ × 0.44λ₀ × 0.1448λ₀ at 2.4 GHz had measured a 31.6% (2–2.75 GHz) impedance bandwidth and 3 dB axial ratio bandwidths of measured were 23.2% (2.1–2.65 GHz), respectively. In addition, the antenna performed a small gain variation (7.0–7.5 dBic) and a front‐to‐back ratio (FBR) of over 25 dB across the whole CP region.     

Novel configuration of ultra‐wide band uni‐planar configuration of complementary split ring resonator composite right/left‐handed based band pass filter with sharp roll off and good stopband attenuation

In this paper, a compact novel simple design of ultra‐wide bandpass filter with high out of band attenuation is presented. The filter configuration is based on combining an ultra‐wide band composite right/left‐handed (CRLH) band pass filter (BPF) with simple uni‐planar configuration of complementary split ring resonator (UP‐CSRR). By integrating two UP‐CSRR cells, the ultra‐wideband CRLH filter roll‐off and wide stopband attenuation are enhanced. The filter has 3 dB cutoff frequencies at 3.1 GHz and 10.6 GHz with insertion loss equals 0.7 dB in average and minimum and maximum values of 0.48 dB and 1.05 dB, respectively over the filter passband. Within the passband. The transition band attenuation from 3 dB to 20 dB is achieved within the frequency band 1.9 GHz to 3.1 GHz (48%) at lower cutoff and the frequency band 10.6 GHz to 11.4 GHz (7%) at upper stopband. Moreover, the filter has a wide stopband attenuation >20 dB in frequencies 11 GHz to 13.6 GHz (21%) and ends with 3 dB cutoff frequency at 14.8 GHz. Furthermore, the designed filter size is very compact (23 × 12 mm²) whose length is only about 0.17 λ_g at 6.85 GHz. The filter performance is examined using circuit modeling, full‐wave simulations, and experimental measurements with good matching between all of them.     

A lateral RF MEMS capacitive switch utilizing parylene as dielectric

A novel lateral RF MEMS capacitive switch was reported in this paper. This switch employed parylene as the dielectric material, taking advantages of its low temperature deposition and conformal coating. The low resistivity single crystalline silicon served as the material of the mechanical structures. The switch was fabricated by bulk micromachining processes with only two lithographic masks and a shadow mask. The dynamical response, parylene insulation performance, and RF performances of the fabricated switch were characterized, respectively. The switching time from the open state to the close state was 105 μs at a loaded voltage of 78 V, while 15.6 μs from the close state to the open state. The isolation was better than 15 dB from 20 to 40 GHz, and the maximal isolation was 23.5 dB at 25 GHz; while the insertion loss was below 1.4 dB at 25 GHz, when bonding wires connected the ground lines. These results verify that the parylene is a good candidate material to act as sidewall dielectric to realize the lateral capacitive switch.     

Novel slotted stepped‐impedance resonator and its application to compact and high performance bandpass filter and diplexer design

By etching slots in the low‐impedance section of the conventional stepped‐impedance resonator, a novel slotted stepped‐impedance resonator (SSIR) is proposed. As two examples, a fourth‐order bandpass filter (BPF) operating at 1 GHz with a size of 0.078 λ_g × 0.062 λ_g and a miniaturized diplexer operating at 0.9/1.57 GHz with a size of 0.054 λ₀ × 0.086 λ₀ are designed based on the proposed SSIR. The fabricated BPF exhibits a high selectivity and a wide ?30 dB rejection upper stopband from 1.13 f₀ to 6.52 f₀, while the fabricated diplexer has up to ?60 dB output isolation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Novel planar balanced bandpass filter with wideband common‐mode suppression and in‐band common‐mode noise absorption

This paper presents a novel planar balanced bandpass filter (BPF) with wideband common mode (CM) noise suppression and in‐band CM noise absorption using coupled lines (CLs) with short‐circuited stubs to realize high selectivity and wideband differential mode (DM) filtering performance. Two one‐quarter wavelength stubs loaded with grounded resistors are introduced to realize wideband CM noise suppression. Thus, CM noise can be suppressed under a certain level at all frequencies. Four resistors are used to achieve CM noise absorption by dissipating the CM noise into heat, which can avoid the noise being reflected to the communication system and realize a wide absorption bandwidth with 90% absorption efficiency. For demonstration, an absorptive balanced BPF operating at 3.5 GHz with wide 3‐dB fractional bandwidth (FBW) of 79.43% is fabricated and experimentally validated. It is worth noted that the absorptive balanced BPF can realize broadband CM noise suppression from 0 to 8 GHz, and the CM noise is well absorbed more than 10 dB from 2.41 to 4.63 GHz. Besides, wideband CM noise absorption with 90% efficiency from 2.51 to 4.60 GHz is realized, which indicates potential applications in improving the performance of the balanced radio frequency (RF) circuits. Good agreements between the simulated and measured results are observed.     

Through-silicon via technologies for interconnects in RF MEMS

In this paper, we describe the application of through-silicon via (TSV) interconnects in Radio Frequency Micro-electro-mechanical systems (RF MEMS). Using TSV technologies as grounding connections, a Ku band miniature bandpass filter is designed and fabricated. Measured results show an insertion loss of 1.9 dB and a bandwidth of 20%. The chip size is 9.6 × 4 × 0.4 mm³. Using TSV as interconnections for 3 dimensional millimeter-wave integrated circuits, a silicon micromachined vertical transition with three layers is presented. TSV, alignment, bonding and wafer thinning technologies are used to fabricate the sample. This transition has an insertion loss of less than 6.7 dB from 26 to 34 GHz and its amplitude variation is less than 2 dB. The total size of the chip is 6.3 × 3.2 mm².     

A tunable balanced dual‐band BPF with quasi‐independently controlled center frequency and bandwidth

In this paper, a balanced dual‐band bandpass filter (BPF) with high selectivity and low insertion loss performance is presented by employing stub loaded resonators (SLRs) and stepped impedance resonators (SIRs) into balanced microstrip‐slotline (MS) transition structures. The balanced MS transition structures can achieve a wideband common‐mode (CM) suppression which is independent of the differential‐mode (DM) response, significantly simplifying the design procedure. Six varactors are loaded into the resonators to achieve the electrical reconfiguration. The proposed balanced dual‐band BPF can realize quasi‐independently tunable center frequencies and bandwidths. A tuning center frequency from 2.48 to 2.85 GHz and a fractional bandwidth (20.16%‐7.02%) with more than 15 dB return loss and less than 2.36 dB insertion loss are achieved in the first passband. The second passband can realize a tuning center frequency from 3.6 to 3.95 GHz with more than 12 dB return loss and less than 2.38 dB insertion loss. A good agreement between the simulated and measured results is observed.     

Coupled‐line band‐pass filter with T‐shaped structure for high frequency selectivity and stopband rejection

A coupled‐line band‐pass filter (BPF) with T‐shaped stub structure is presented. Five transmission poles within the passband and eight deep transmission zeros (TZs) from 0 to 2f₀ (f₀ denotes filter's center frequency) are realized through input impedance calculations. With the simple T‐shaped structure, the positions of six TZs can be appropriately adjusted to achieve high frequency selectivity and stopband rejection. For demonstration, a BPF prototype centered at 2.05 GHz is designed and fabricated, whose measured rejection levels are of over 45.5 dB at lower stopband and better than 19.5 dB at upper stopband. The simulation and measurement results are in good agreement, which validates the design idea.     

Broadband radio frequency MEMS series contact switch with low insertion loss

A new radio frequency (RF) micro-electro-mechanical-system (MEMS) single cantilever series contact switch is designed as a low-insertion-loss and low-power electronic component that is intended to provide integrated control of the opening and closing signals of other MEMS devices operating over a wide frequency range (DC–60 GHz). The MEMS switching element consists of an A-type top electrode that is fixed onto coplanar waveguide lines through anchor points to reduce the insertion loss in the on-state of the device. The air gap between the top electrode and the actuation electrode of the designed MEMS switch is optimized to improve the isolation characteristics of the switch. In addition, the switching voltage required is approximately 24 V. The simulation results presented here show that the insertion loss of the switch in the on-state is less than 0.71 dB, while the minimum isolation is 20.69 dB in the off-state at 60 GHz. The proposed RF MEMS switch will be useful for communication devices and test instruments used in broadband applications.

     

Analysis of a novel RF MEMS switch using different meander techniques

In this paper, two types of RF MEMS switches namely step structure and Normal beam structure are designed and analyzed using different meander techniques. Three techniques namely plus, zigzag and three-square meander were used to lower the pull-in voltage. The actuating beam is designed with the rectangular perforations affects the performance of a switch by lowering the pull-in voltage, switching speed and results in better isolation. In this paper a comparative analysis is done for all three meander techniques with and without perforations on the beam. Total six structures have been designed with the combination three meanders and two different beam structures. The proposed stepdown structure exhibits high performance characteristics with a very low pull-in voltage of 1.2 V having an airgap of 0.8 µm between the actuation electrodes. The gold is used as beam material and HfO₂ as the dielectric material such that the upstate and downstate capacitance is seen as 1.02 fF and 49 fF. The FEM analysis is done to calculate the spring constant and thereby the pull-in voltage and behavior of the switch is studied with various parameters. The switch with a step structure and three-square meander configuration has shown best performance of all by requiring a pull-in voltage of 1.2 V and lower switching time of 0.2 µs. The proposed switch also exhibits good RF performance characteristics with an insertion loss below − 0.07 dB and return loss below − 60 dB over the frequency range of 1–40 GHz. At 28 GHz a high isolation of − 68 dB is exhibited.

     

Wideband bandpass filter based on U‐slotted SW‐HMSIW cavities

A wideband bandpass filter (BPF) is designed based on U‐slotted slow wave half mode substrate integrated waveguide (SW‐HMSIW) cavities. Similar to the substrate integrated waveguide (SIW), the SW‐HMSIW can also achieve a highpass characteristic while the lateral dimensions can be reduced by about 50%. By etching a U‐shape slot on the SW‐HMSIW cavity, a multiple‐mode resonator (MMR) can be realized, which can achieve a wide passband response and make the overall dimension of the filter much more compact. A wide passband, covering from 6.0 GHz to 10.65 GHz with a FBW about 58.13% is achieved. The measured minimum insertion losses including the losses from SMA connectors are 1.1 dB and return losses are better than 10 dB. Besides, the group delay varies between 0.2 and 0.5 ns within the passband. To validate its practicability, a wideband SW‐HMSIW BPF fabricated on a double‐layer printed circuit board (PCB) is designed and examined. The proposed filter has a more than 54% size reduction compared to the other designs reported in open literatures. The measured results have a good agreement with the simulated results. The effective size of the fabricated filter is about 27 mm × 8.55 mm.     

Micromachined W-band polymeric tunable iris filter

A tunable filter working in the W-band spectrum has been successfully demonstrated using a combined plastic molding and electroplating process. The prototype filter architecture has two deformable membranes of 1.6 mm in diameter on top of a WR-10 waveguide based, two-cavity, polymeric iris filter. The membranes can be actively adjusted to deform and alter the cavity geometry concurrently for frequency tuning applications. The tunable filter was simulated using High Frequency Structure Simulator and theoretically analyzed using the perturbation method. Experimentally, a prototype band-pass filter has bandwidth of 4.05 GHz centered at 94.79 GHz and a minimum insertion loss of 2.37 dB with return loss better than 15 dB. As a tunable filter, a total of 2.59 GHz center frequency change has been recorded when the membranes deflected from 50 μm into, to 150 μm out of the waveguide. These results imply that the demonstrated tunable filter could be potentially applicable for waveguide-based mm-wave systems.     

RF-MEMS for 5G applications: a reconfigurable 8-bit power attenuator working up to 110 GHz. Part 1: design concept,technology and working principles

RF-MEMS technology is indicated as a key enabling solution to realise the high-performance and highly-reconfigurable passive components that future 5G communication standards will demand for. In this work, a novel design concept of an 8-bit reconfigurable power attenuator manufactured in the RF-MEMS technology available at the CMM-FBK, in Italy, is tested and discussed. In the current Part 1 of the contribution, the RF-MEMS power attenuator design concept is discussed. The device features electrostatically controlled MEMS ohmic switches, in order to select/deselect resistive loads (both in series and shunt configuration) that attenuate the RF signal, and comprises eight cascaded stages (i.e. 8-bit), thus implementing 256 different network configurations. In Part 2 of the article, fabricated samples are measured (S-parameters) from 10 MHz to 110 GHz in a wide range of different configurations, and modelled/simulated in with a Finite Element Method software tool. Despite the attenuator complexity, the simulation approach leads to accurate prediction of the experimental behaviour. The device exhibits attenuation levels (S21) in the range from − 10 to − 60 dB, up to 110 GHz. In particular, the S21 shows flatness from 15 dB down to 3–5 dB, from 10 MHz to 50 GHz, while less linear traces up to 110 GHz. A comprehensive discussion is developed around the voltage standing wave ratio, employed as quality indicator for the attenuation levels. Finally, margins of improvement at design level are also discussed, in order to overcome the limitations of the presented RF-MEMS device.