Reconfigurable Bandpass Research Articles

Design Methods for Reconfigurable Filters: A Review

The new design methods of microwave filter has proved its significance for use in wireless communication systems. Modern wireless communication systems require microwave filters to have stringent specifications such as compact size, robust, conformal, light weight and more importantly cost effective while maintaining its electrical characteristics. Micro-strip filter design and reconfigurable filters present a better prospectus in this regards as it meets the specifications of modern wireless communication applications. Reconfigurable filters can provide control over parameters such as frequency, bandwidth and selectivity while reducing the need of number of switches sandwiched between electrical components. Different methods have provided a new dimension for designing microwave filters .In this article, we present a review on design methods for reconfigurable band-pass filters for next generation wireless technologies such as 4G, 5G and IOT.

Design Methods for Reconfigurable Filters A Review

The new design methods of microwave filter has proved its significance for use in wireless communication systems. Modern wireless communication systems require microwave filters to have stringent specifications such as compact size, robust, conformal, light weight and more importantly cost effective while maintaining its electrical characteristics. Micro-strip filter design and reconfigurable filters present a better prospectus in this regards as it meets the specifications of modern wireless communication applications. Reconfigurable filters can provide control over parameters such as frequency, bandwidth and selectivity while reducing the need of number of switches sandwiched between electrical components. Different methods have provided a new dimension for designing microwave filters .In this article, we present a review on design methods for reconfigurable band-pass filters for next generation wireless technologies such as 4G, 5G and IOT.

Fully reconfigurable hexagonal-shaped comb-line filterplatform for prototyping and education purposes

AbstractIn this paper, a completely reconfigurable comb-line bandpass filter is presented. Due to the modularity, different standard coupling matrix topologies like the folded form, cascaded triplets, and the cul-de-sac form can be implemented and tested. Circuit-based coupling matrices like the extracted pole topology can easily be realized as well. Different types of input-/output- and cross-couplings can be examined before fabrication of a fixed filter set-up takes place. Furthermore, the proposed filter platform can be used to construct a diplexer. By using different heights of the inner and outer conductor of the coaxial resonators, arbitrary center frequencies in the range between 1 and 4 GHz can be realized. Various types of input couplings are available and proposed here to achieve bandwidths between 10 and 110 MHz. A variety of cross-coupling apertures able to realize transmission zeros are presented as well.

Centre frequency and BW reconfigurable multi‐mode band‐pass filter with independently tunable TZs

This study reports the design, development and analysis of centre frequency and bandwidth (BW) reconfigurable multi-mode band-pass filter with independently tunable transmission zeroes (TZs). The designed filter can tune lower TZ () from 1.66 to 1.88 GHz (220 MHz) with lower-side BW tuning range 200–400 MHz and upper TZ () from 2.32 to 2.48 GHz (120 MHz) with upper BW tuning range 430–630 MHz. The centre frequency of the designed filter can be tuned from 1.98 to 2.04 GHz (60 MHz). For the entire tuning range, the insertion loss of the designed filter is around 1.4–2.3 dB and return loss is better than 10 dB within the pass-band.

Frequency- and Bandwidth-Tunable Absorptive Bandpass Filter

In this paper, an analytic design method for a frequency- and bandwidth-tunable absorptive bandpass filter is introduced. The presented design method relies on the transformation from the normalized absorptive low-pass filter prototype to a bandpass filter structure with parallel resonators and admittance inverters. The inverter values for producing a predefined frequency response are given in closed-form expressions so that a filter design needs no heuristic approach and can be carried out in an analytic manner. This work also presents a new tunable stub resonator structure capable of changing not only its resonant frequency but also the slope parameter. As the slope parameter can be adjusted, it is allowed to use static inverters in designing a filter whose bandwidth can be tuned. For demonstrating our design method for a reconfigurable absorptive bandpass filter, a third-order filter having the target to have the frequency tuning range from 1.35 to 1.65 GHz and the bandwidth tuning range from 5% to 10% has been designed and measured.

Multifunctional Bandpass Filters With Reconfigurable and Switchable Band Control

A new series of multifunctional reconfigurable bandpass filters (BPFs) and their analytical synthesis design are presented in this paper. They feature frequency-adaptive characteristics in both their passbands and notched bands, as well as switchable-notched-band capability. Their basic filter architecture is discussed and modeled in a progressive manner. The initial circuit consists of a second-order Chebyshev-type filter to which two stubs are added to increase filtering selectivity through transmission-zero (TZ) creation. Subsequently, to produce an embedded notched band, stubs acting as band-stop structures are also inserted at the input–output terminals. The multifunctional properties of this filter scheme are analyzed attending to the resonance frequencies of the introduced stubs. When these resonance frequencies are tuned while keeping a constant spacing between them, a center-frequency reconfiguration with constant bandwidth is achieved; when the resonance frequency of the notched band is shifted to the TZ positions, the notched band is switched-off. The described filter synthesis methodology is based on the constant and frequency-mapping technique, where the dual-mapping functions are controlled to obtain reconfigurable/switchable properties from a low-pass prototype. For experimental-validation purposes, two reconfigurable lumped-element filter prototypes using the proposed synthesis technique are designed, manufactured, and tested. One exhibits a simple reconfigurable passband, whereas the other one adds a controllable/switchable embedded notched band that results in a quasi-elliptic-type dual-passband response. When compared to some related prior-art designs, these filters have the advantages of explicit design process, quantified analysis, and multifunctional responses.

Analog Gross Fault Identification in RF Circuits Using Neural Models and Constrained Parameter Extraction

The demand and relevance of efficient analog fault diagnosis methods for modern RF and microwave-integrated circuits increase with the growing need and complexity of analog and mixed-signal circuitry. The well-established digital fault diagnosis methods are insufficient for analog circuitry due to the intrinsic complexity in analog faults and their corresponding identification process. In this paper, we present an artificial neural network (ANN) modeling approach to efficiently emulate the injection of analog faults in RF circuits. The resulting metamodel is used for fault identification by applying an optimization-based process using a constrained parameter extraction formulation. A generalized neural modeling formulation to include auxiliary measurements in the circuit is proposed. This generalized formulation significantly increases the uniqueness of the faults identification process. The proposed methodology is illustrated by two faulty analog circuits: a CMOS RF voltage amplifier and a reconfigurable bandpass microstrip filter.

Center Frequency and Bandwidth Reconfigurable Spoof Surface Plasmonic Metamaterial Band-Pass Filter

In this study, we report a design concept to obtain center frequency and bandwidth reconfigurable spoof surface plasmon polaritons (SSPP) band-pass filter using T-shaped spoof SPP resonator. The design, analysis, and implementation of the proposed filter have been given with detailed mathematical analysis. Tuning has been performed using varactor diode which is introduced at different positons in the T-shaped resonator. Since spoof SPP has high field confinement and enhancement, hence it offers low crosstalk and mutual coupling as compared with conventional microstrip which is desirable to make low-loss system. The filter has been fabricated using a 1.52-mm-thick microwave laminate and characterization has been done using Keysight Field-Fox analyzer N9918A. The fabricated filter has a reconfigurable center frequency from 4.2 to 4.4GHz with insertion loss ~4.2 dB and bandwidth reconfigurable from 4.12 to 4.52GHz with ~3.8 dB insertion loss in the tuning range. The proposed reconfigurable band-pass filter will pave an important role in the designing and developing of the flexible plasmonic circuits and systems.

Dynamically Reconfigurable SIR Filter Using Rectenna and Active Booster

A novel dynamically reconfigurable bandpass filter (BPF) employing stepped-impedance resonators (SIRs) that can operate as either a single-band or a dual-band filter is demonstrated. The reconfigurable BPF uses four positive-intrinsic-negative (p-i-n) diodes as switching elements. With the four p-i-n diodes in the “OFF” state, the filter behaves as a low-loss (0.85 dB) single-band BPF with a passband around 2.45 GHz. The reconfigurable SIR filter can operate as a dual-band BPF with two center frequencies at 1.6 and 2.45 GHz. The diodes are dynamically set to the “ON” state in the presence of a 1.6-GHz RF signal that is received by an RF triggered power management unit (PMU), integrated on the back side of the microstrip filter in a dual-layer architecture. The RF triggered PMU consists of a planar inverted-F antenna, a high-efficiency voltage doubler rectifier (47% at −13 dBm) and an active dc-to-dc power booster. The rectified output voltage is used as the enabling voltage for the dc-to-dc power booster. This, in turn, provides the required dc power for the diodes biasing. The filter switches from single-band to dual-band when a wireless input RF signal (> −13 dBm) is received by the RF triggered PMU antenna.

Compact reconfigurable bandpass filter with wide frequency tuning range

ABSTRACTA compact reconfigurable bandpass filter with wide tuning range is proposed in this letter. The reconfigurable function is realized by utilizing two varactor diodes at the end of the bandpass filter. Instead of using the coupling gap to create the desired coupling coefficients, a high characteristic impedance line is applied. A compact reconfigurable filter is designed, fabricated and measured. The measured tuning frequency ranges from 0.38 GHz to 0.96 GHz, which is about 86.6% of the central frequency. The measured insertion loss of the proposed reconfigurable filter is less than 2.5 dB, while the measured return loss is greater than 11 dB.

Novel Reconfigurable Single-to-Balanced, Power-Dividing, and Single-Ended Filter With Frequency and Bandwidth Control

In this paper, a novel tunable filter with reconfigurable single-to-balanced (SE-BAL), power dividing (PD), and single-to-single-ended (SE) filtering functionalities is proposed, for the first time, without any additional switching circuit. The proposed filter only consists of three stepped-impedance resonators, which are loaded and connected by varactors in between. With a very simple and compact configuration, the proposed filter achieves multiple reconfigurable functionalities between SE-BAL filtering, PD filtering, and conventional SE bandpass filtering. Moreover, the reconfigurable SE-BAL, PD, and SE bandpass filter can not only offer continuously frequency tuning over a wide tuning range but also have independent bandwidth tuning and maintain good phase/amplitude balance in each tuning state. The proposed filter is designed and fabricated with the microstrip line technology; the measured results show that the SE-BAL, PD, and SE filtering functions can be continuously tuned from 1.02 to 1.32, 0.96 to 1.27, and 1 to 1.28 GHz, with 1-dB bandwidth tuning from 30 to 60, 30 to 110, and 70 to 130 MHz, respectively. The amplitude and phase imbalances of the SE-BAL and PD bandpass filter are less than 0.4 dB, 1.3° and 0.5 dB, 1.5°, respectively, in the passband of each tuning state. Good agreement was obtained between simulated and measured results.

Spoof Surface Plasmon Polaritons Based Reconfigurable Band-Pass Filter

This letter reports the design and analysis of the bandwidth (BW) reconfigurable band-pass filter using spoof surface plasmon polaritons at THz/microwave frequency. The designed filter consists of a spoof SPP T-shape resonator in which tuning has been introduced using variable capacitor device (having a cutoff frequency in THz regimes). Even and odd mode analysis has been carried out for a better understanding of the phenomenon. The proposed concept of variable bandwidth at a THz frequency in the SSPP structure has been demonstrated through Co-EM simulation. For the experimental validation of the proposed approach, the filter has been designed at microwave frequency, developed on a 60 mil (1.52 mm) thick microwave laminate, and characterized using a Keysight Field-Fox analyzer N9918A . In THz and microwave frequency regime, the designed filter has 3-dB BW reconfigurability of 20 GHz (0.41–0.43 THz) and 300 MHz (100–400 MHz) with the insertion loss of ~3 dB and ~1.7 dB–3.2 dB, respectively. The proposed reconfigurable bandpass filter will have an important role in the design and development of plasmonic circuits and systems.

Active Frequency Selective Surface With Wide Reconfigurable Passband

This paper presents an active frequency selective surface (AFSS) with a wide reconfigurable passband. The tuning mechanism was investigated with an equivalent circuit which consists of a parallel L-C resonant circuit and a series L-C resonant circuit. A cross-loop slot was selected as a unit cell, and varactor diodes were added across the slot to tune the passband. The effects of various bias configurations on the transmission coefficients were studied. The simulation results showed that a reconfigurable passband ranged from 2.92 to 5.74 GHz was obtained with a variable capacitance from 0.8 to 0.1 pF. A prototype of the proposed AFSS was fabricated and measured. The measurement results showed that the passband was altered from 2.94 to 5.66 GHz if the biasing voltage of varactor diodes was increased from 4 to 18V. The measurement and simulation results agree well with each other.

Reconfigurable Compact Bandpass Microstrip Filter of Bandwidth 1.54GHz

A new compact Bandpass Microstrip filter with very wide band is presented using Reconfigurable Bandpass Microstrip Filter, it is reconfigured and simulated to Reconfigured Compact Bandpass Microstrip (RCBM) Filter to minimize the size of the filter and to enhance its bandwidth (BW). The achieved BW is 1.54GHz with minimum amount of insertion loss of -0.5dB and compactness of 1/3^rd size reduction in the filter compared to its original filter size. In this methodology- varying the spacing, length and width of transmission lines of this RCBM is done. Hence by the variation of its dimensions the size of the filter is reduced with enhanced BW. These filters are used in handheld communication systems- here the size of each component, size of overall system and incorporating more number of features to that system is the main goal in recent research of handheld communication and these are the most important parameters. For this purpose compact filters are required, hence the proposed work is to achieve the compactness of the Microstrip Bandpass Filter by reconfiguring the compact Bandpass micro strip filter and increasing their performance. The proposed RCBM Filter is successfully realised in theory and verified by full wave electromagnetic simulation and the experiment. The simulated and measured results are in excellent agreement.

New method of analysis and design of frequency and bandwidth reconfigurable active filter

A new method of analysis and design of reconfigurable active bandpass filter is proposed. The proposed method involves matrix manipulation for equating passive inverter impedances with those of active inverter (both input and output impedances). Designing of active filter involves the designing of active inverter and active resonator. The filter performance is analysed in frequency range 500 MHz to 1.5 GHz. The narrow band filter is switched between two bands with varying fractional bandwidth and centre frequency. The physical implementation comprise elements employing ATF 21186 FET on RT Duroid 5880 substrate with dielectric constant 2.2 and thickness 0.127 mm. Active resonator comprises of an active capacitor and a passive inductor. The active inverter along with active resonator employed in active filter circuit provides reconfigurability in frequency (≈200 MHz) as well as in bandwidth with the variation in gain of approximately 8-10 dB. The electrical performance of active band pass filter shows good agreement with the measured response. To best of my knowledge first time integration of active inverter and active capacitor is done. Intergration of such kind allows for frequency as well as bandwidth tuning. The electrical performance of active band pass filter shows slight deviation from with the measured response.

Design and Simulation of a Miniaturized RF-MEMS Reconfigurable Microstrip Combline Band Pass Filter

Reconfigurable bandpass filter (RBPF) is crucial in various radio frequency (RF) applications. However, the use of lumped element filters have failed to show tuneable integrated solutions with low insertion loss in the high frequency range. Most reconfigurable filter designs are faced with the challenges of narrow bandwidth, high losses, bulkiness, high voltage and high power consumption. To overcome these issues, this research undertakes to develop a miniaturized reconfigurable radio frequency micro-electro-mechanical system (RF MEMS) band-pass filter designed for wireless communication at the center frequency of 30 GHz. The filter is optimized for low insertion loss, broad bandwidth, low applied voltage, lower power consumption and high linearity. The design consists of 3rd order tapped input microstrip combline transmission lines structure integrated with in-plane tunable parallel capacitors and electrothermal actuator. The transmission lines are patterned on a silicon dioxide (Si02) of thickness 1 μm placed on a silicon (Si) substrate with the dielectric constant of ε,. = 11.9. The filter occupies chip area of 1.1 mm x 0.9 mm without the dummy substrate. The 3D structure is designed and simulated in Computer Simulator Technology (CST). The result shows the achieved inband insertion loss of less than 1 dB and the return loss better than 8 dB. The proposed reconfigurable bandpass filter can tune its center frequency with relatively constant absolute bandwidth.

A Compact Reconfigurable Multi-mode Resonator-based Multi-band Band Pass Filter for Intelligent Transportation Systems Applications

A compact wide band reconfigurable bandpass filter (BPF) which utilises a hemi-circular flower shaped multimode resonator (MMR) is presented. The proposed MMR provides three resonant modes which fall within the broad frequency spectra. Among these, two modes are even and one is odd. These modes are optimised by varying the dimensions so as to obtain the desired frequency response. The fractional bandwidth is more than 96 per cent. The filter can be operated as multi-band BPF. In OFF condition of ‘Pin’ diode, the centre frequencies are 2.43 GHz, 3.5 GHz, and 5.9 GHz in ON condition of ‘Pin’ diode centre frequencies are 2.43 GHz, 3.5 GHz, 5.9 GHz, 6.5 GHz, and 8.8 GHz which are used for vehicular, WiMAX, intelligent transportation systems and satellite communication respectively. Microstrip filter structures are integrated with ‘Pin’ diodes. Appropriate biasing has been provided by choosing lumped components with precise values. The insertion loss in OFF condition are 0.5 dB, 0.67 dB, and 0.8 dB and in ON condition 0.5 dB, 0.7 dB, 1.2 dB, and 1.9 dB. The measured results agree well with the full-wave simulated results.

Reconfigurable multilayer dual-mode bandpass filter based on memristive switch

A novel memristor-based multilayer dual-mode resonator is presented, which is suitable for the design of reconfigurable multi-band filters. The memristor is used as an RF/microwave switch. A dual-band bandpass filter is realized with the proposed memristor-based dual-mode resonators. The corresponding memristor setup circuitry is optimized in order to minimize the circuitry influence on the desired filter frequency response.

RF and microwave reconfigurable bandpass filter design using optimized active inductor circuit

In this article, a design methodology of an active bandpass filter (BPF) using tunable active inductor (TAI) achieving wide frequency contiguous tuning range (FTR) is presented. The tunable BPF is realized with a differential TAI (DTAI) employing two-reconfiguration mechanisms one for coarse-tuning using a controllable current source while the fine-tuning is performed through a variable feedback resistance. The center frequency tuning is performed through the variation of the DTAI control voltages. A cross-coupled pair based negative resistance technique is also applied to compensate the resistive losses of equivalent RLC resonator. The filter performances are significantly improved using several optimization techniques such as voltage scaling and multigate finger techniques. The proposed BPF is simulated using 0.13 μm CMOS technology. The filter achieves an insertion loss (IL) of 26.62-33.45 dB over the tuning range 1.16-3.27 GHz with a relative bandwidth of 1.3%-3.4%. The noise figure and input 1-dB compression point at 1.84 GHz are 14.93 dB and 2.72 dBm, respectively. The designed RF filter consumes an average power of 5 mW at 1 V supply voltage.

Spoof Surface Plasmon Polariton-Based Reconfigurable Band-Pass Filter Using Planar Ring Resonator

In this paper, we report the design, analysis, and development of spoof surface plasmon polariton (SSPP)-based reconfigurable band-pass filter using a planar ring resonator. A transition from quasi-transverse electromagnetic (QTEM) mode of microstrip to SSPP mode was implemented which has been subsequently used to develop a reconfigurable band-pass filter. Trapezoidal shape periodically corrugated metallic grooves etched on the planar metallic surface have been used in the implementation of this transition. In the designed transition, impedance and mode matching between QTEM mode and SSPP mode have been achieved using gradient grooves. The developed transition has been used in the characterization of a ring resonator corrugated with the periodical array of the trapezoidal shape grooves. This SSPP ring resonator shows multiple passbands at different frequencies within the specified frequency range. Varactor diodes have been incorporated in the SSPP ring resonator to obtain tunable passband. Three types of varactor-tuned circuits have been experimentally implemented and characterized using SMV2019-079LF diode package. These circuits will pave the path for development of other front-end circuit elements using the concept of spoof SPP.