Reconfigurable Bandpass Filter Research Articles

Reconfigurable bandpass filter with electric coupling and constant absolute bandwidth

This paper presents a reconfigurable bandpass filter (BPF) with constant absolute bandwidth (ABW). The structure is composed of a pair of novel half wavelength (λ/2) resonators with two center-tapped var actors. Frequency tuning is made possible by modifying the electrical length of the resonators with four varactors. Following the traditional synthesis approach, the internal coupling is analyzed and designed properly to meet the requirement of constant ABW. At last, the proposed filter exhibits a 49% fractional tuning range from 500 to 825 MHz, and a near constant 3-dB bandwidth of 56 ± 5 MHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1401–1404, 2016

A new approach to design compact tunable BPF starting from simple LPF topology using a single T‐DGS‐resonator and ceramic capacitors

ABSTRACTIn this article, a novel very compact DGS lowpass filter (LPF) and reconfigurable bandpass filter are proposed. The designed filter consists of one T‐DGS resonator, which is excited by 50 ohm microstrip line, placed on top layer between the input and output of the proposed structure. The selected filter topology has several advantageous compared with the other previous works such as the compactness and its simple design. The addition of compensated patch capacitor improves the low insertion loss and ultra‐wide stopband with 15 dB attenuation from 2.2 to 3.6 GHz. The size of the proposed single T‐DGS LPF‐BPF is less as (0.023 λg × 0.044 λg) with λg = 0.263 m. The tunable bandpass filter (BPF) is extracted from LPF topology using variable Chip Monolithic Ceramic Capacitors and J‐inverter technique. Finally, the measured, EM‐ and field simulation results are presented and discussed. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1142–1148, 2016

Dual-Band Reconfigurable Bandpass Filter With Independently Controlled Passbands and Constant Absolute Bandwidths

This letter presents a novel reconfigurable dual- band bandpass filter (DBBPF) with independently controlled passbands and constant absolute bandwidths (ABW). The design procedures follow the traditional synthesis approach of filters. Moreover, in order to meet the requirement of constant ABW, theoretical analysis and calculation are carried out to determine proper parameters of coupling regions. Finally, the proposed DBBPF exhibits 21.8% fractional tuning range of the first passband from 0.98 to 1.22 GHz and 17.9% of the second passband from 1.63 to 1.95 GHz, and 3-dB ABWs are 76 $\pm$ 4 MHz and 100 $\pm$ 4 MHz, respectively.

Fully-Reconfigurable Bandpass/Bandstop Filters and Their Coupling-Matrix Representation

A new type of a tunable microwave filtering device with reconfigurable bandpass-filter (BPF) and bandstop-filter (BSF) operational modes is reported. It consists of series-cascaded BPF/BSF stages which are formed by two resonating nodes, one non-resonating node (NRN), and two impedance inverters. Each BPF/BSF stage results in two transmission zeros (TZs) that are generated at the natural frequencies of the constituent resonators, whose spectral locations can be reconfigured by tuning the resonating elements. Thus, multi-TZ BPF/BSF responses can be synthesized in the overall circuit which features fully-controllable performances by means of TZ reallocation. The coupling-matrix representation of the proposed frequency-agile BPF/BSF scheme is demonstrated. Moreover, an S-band two-stage prototype based on frequency-reconfigurable evanescent-mode cavity resonators is fabricated to experimentally validate the predicted behavior.

Design of 5 GHz‐compact reconfigurable DGS‐bandpass filter using varactor‐diode device and coupling matrix technique

ABSTRACTIn this work, a novel electrical reconfigurable second order microstrip bandpass filter is presented. The investigated filter structure consists of two neighbor coupled octagonal‐DGS resonators. The capacitor and varactor are placed on the DGS‐shape. According to the tunable characteristic of discrete lumped capacitors and varactor diode, the resonant frequencies can be tunable. The proposed filter occupies an area of 2.5 × 1.5 cm2. The coupling method has been applied and leads to an extended coupling matrix that assumes multiple couplings between both filter resonators. The measured relative tuning range of the bandpass filter is 23.5% with a fractional bandwidth of 12%. Varactors loaded on the octagonal DGS resonator allow us to control the center frequency with quasi constant bandwidth as well as to have a large tuning bandwidth. Based on the detailed analysis, the varactor‐tuned DGS bandpass filter is designed, in which the tuning bandwidth reaches 12% of the center frequency at 5 GHz. The proposed reconfigurable bandpass filter was fabricated and tested. The measured results show a variation of the center frequency from 4.3 GHz (0V) to 5.4 GHz (15V) tunable range, while the insertion loss varies from 5 to 3 dB. The measured performance of the tunable bandpass filter agrees well with the simulation results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:304–309, 2016

Integrated Wideband Self-Interference Cancellation in the RF Domain for FDD and Full-Duplex Wireless

A fully integrated technique for wideband cancellation of transmitter (TX) self-interference (SI) in the RF domain is proposed for multiband frequency-division duplexing (FDD) and full-duplex (FD) wireless applications. Integrated wideband SI cancellation (SIC) in the RF domain is accomplished through: 1) a bank of tunable, reconfigurable second-order high-Q RF bandpass filters in the canceller that emulate the antenna interface’s isolation (essentially frequency-domain equalization in the RF domain) and 2) a linear $N$ -path $G_m$ - $C$ filter implementation with embedded variable attenuation and phase shifting. A 0.8–1.4 GHz receiver (RX) with the proposed wideband SIC circuits is implemented in a 65 nm CMOS process. In measurement, $>20\;\text{MHz}\;20\;\text{dB}$ cancellation bandwidth (BW) is achieved across frequency-selective antenna interfaces: 1) a custom-designed LTE-like 0.780/0.895 GHz duplexer with TX/RX isolation peak magnitude of 30 dB, peak group delay of 11 ns, and 7 dB magnitude variation across the TX band for FDD and 2) a 1.4 GHz antenna pair for FD wireless with TX/RX isolation peak magnitude of 32 dB, peak group delay of 9 ns, and 3 dB magnitude variation over 1.36–1.38 GHz. For FDD, SIC enhances the effective out-of-band (OOB) IIP3 and IIP2 to $+\text{25}\text{-}27\;\text{dBm}$ and $+90\;\text{dBm}$ , respectively (enhancements of 8–10 and 29 dB, respectively). For FD, SIC eliminates RX gain compression for as high as $-8\;\text{dBm}$ of peak in-band (IB) SI, and enhances effective IB IIP3 and IIP2 by 22 and 58 dB.

Reconfigurable Multi-Band Microwave Filters

An original and simple approach to the design of fully reconfigurable multi-band microwave bandpass filters (BPFs) with an arbitrary number of passbands is reported in this paper. It exploits the use of an innovative quasi-BPF configuration made up of different sets of controllable mono-frequency resonators to separately shape each tunable passband. Thus, high-selectivity multi-band bandpass filtering transfer functions exhibiting independent control in terms of center frequency, bandwidth, and transmission zeros can be synthesized. Furthermore, as an unprecedented frequency-agility feature of the proposed reconfigurable multi-band BPF structure when compared to the state-of-the-art, its passbands can be merged together to form broader, and for certain realizations, higher order transmission bands. This allows even more degrees of reconfiguration to be achieved in the devised circuit, which can also operate as ultra-wideband BPF with flexible in-band notches or self-equalized flat-group-delay quasi-elliptic-type BPF. The theoretical foundations of the described reconfigurable multi-band BPF scheme, along with guidelines for its design and a triple-passband filter synthesis example based on the coupled-node formalism, are expounded. In addition, as an experimental proof-of-concept, two microstrip prototypes with high- Q tuning implemented through mechanically variable capacitors are manufactured and tested. They are a wideband dual-band BPF and a quadruple-band BPF with narrow-bandwidth passbands.

FPGA-based reconfigurable system for tool condition monitoring in high-speed machining process

We present a reconfigurable system to detect and indicate online and in real time, the cutting tool conditions in high-speed face milling. It consists of a data acquisition system (DAS) and a hardware signal processing (HSP) unit. The DAS acquires and digitalizes the cutting vibration signals generated from machining tests performed under different tool conditions and cutting parameters. The HSP unit processes the digitalized vibration signals using reconfigurable IIR band-pass digital filter and statistical techniques, designed and implemented into a single field-programmable gate array (FPGA) and coefficients read-only memories. The system operation is divided into learning and monitoring modes. The tool condition is indicated by an alarm signal, one LED indicator, and a message shown on four-digit seven-segment displays. In all experiments, the system correctly detected the tool condition. The proposed system is fast, compact, reliable, and economical, and no modification of the machine-tool structure is required.

Analysis of Coupled Cross-Shaped Resonator and Its Application to Differential Bandpass Filters Design

Analysis and applications of coupled cross-shaped resonator (CCSR) for fixed and fully reconfigurable differential bandpass filters (BPFs) design are focused in this paper. CCSRs with open and capacitive terminations are presented and discussed. One differential BPF named Filter I centered at 4.5 GHz with fixed differential-mode (DM) and common-mode (CM) responses using CCSR with open termination; and another one named Filter II using capacitive termination and loaded lumped capacitors offers fully reconfigurable DM center frequency, bandwidth and intuitive CM suppression control are proposed with very compact size (0.01λ0 2 ). Such that ultra-wide DM center frequency tuning range of 82% fractional tuning range with both constant absolute bandwidth (ABW) and constant fractional bandwidth (FBW), easy control of CM suppression level and rejected range are achieved, respectively. Their experimental characterizations are in good agreement with theoretical analysis validating a simple approach of fixed and fully reconfigurable differential BPFs design.

High-efficiency microwave photonic harmonic down-conversion with tunable and reconfigurable filtering.

A new optical-frequency comb-based microwave photonic harmonic down-convertor with tunable and reconfigurable filtering is proposed and experimentally demonstrated. The coherent evenly spaced optical carriers offer harmonic down-conversion for ultrahigh radio frequency signals with low-frequency local oscillator, and construct a tunable and reconfigurable bandpass filter for the intermediate-frequency (IF) signal combined with dispersion. This implementation features high conversion efficiency. Experimental results show the filtered output IF signal has a clean spectrum with high quality. Measured conversion loss is 8.3 dB without extra electrical amplification.

Millimeter-wave reconfigurable bandpass filters

Millimeter-wave reconfigurable bandpass filters with the ability to operate between 60 GHz and the E-band, capable of providing good channel isolation, are presented. A fully integrated filter with all reconfigurable elements embedded for compactness and a switchable filter that uses radio frequency micro-electro-mechanical system (RF MEMS) single-pole double-throw switches are designed. A new method that increases fractional bandwidths is introduced. It uses inductively coupled inverters without requiring their tuning. New circuit models are offered for inverters, reconfigurable resonators, and reconfigurable bandstop stubs. Our compact bandpass filter achieved a footprint of only 4.75 mm × 3.75 mm. Measurements for our filters show good agreement with the results of simulations.

60 GHz to E-Band Switchable Bandpass Filter

A novel reconfigurable millimeter-wave bandpass filter (BPF) capable of operating between 60 GHz and the E-band, with a good channel isolation, is presented. This fully integrated filter is designed with all reconfigurable elements embedded for compactness. A new method that increases fractional bandwidths is introduced. It uses inductively coupled inverters but does not require tuning. New circuit models are provided for these inverters, reconfigurable resonators, and the reconfigurable bandstop stubs. The compact BPF achieved a footprint of only 4.75 mm × 3.75 mm. Measurements for the filters show good agreement with the simulation results.

Reconfigurable dual-mode band-pass filter with switchable bandwidth using PIN diodes

A reconfigurable band-pass filter with switchable bandwidth, for wireless applications is demonstrated using a dual-mode microstrip square-loop resonator. The proposed filter has been designed on Rogers RO4003C and achieves switchable bandwidth by changing the length of two tuning stubs with the implementation of two strategically placed p-i-n diodes as switching elements. The filter was designed with a center frequency of 2.4 GHz and the two distinct operation states have bandwidths, 113 MHz (4.8%) with an insertion loss of 1.2 dB and 35 MHz (1.5%) with an insertion loss of 1.5 dB. The physical size of the fabricated reconfigurable filter including the implementation of the DC bias lines is comparable to the size of a conventional filter.

A Reconfigurable Bandpass Filter Based on a Varactor-Perturbed, T-Shaped Dual-Mode Resonator

A microstrip bandpass filter (BPF) with high center-frequency tunability, bandwidth reconfigurability, and a one-side band edge transmission zero (TZ) is presented. The reconfigurable BPF is developed with a simple T-shaped dual-mode resonator, which is externally coupled and perturbed with varactor diodes. Also, the design of adjustable admittance inverters for tunable resonators external coupling is proposed to mitigate the in-band performance degradation that hurdles the ones with a fixed coupling. It is demonstrated that the 1 dB bandwidth is able to be varied from 55 to 175 MHz for center frequency ranging from 750 to 1240 MHz with a low insertion loss (2.9 dB).

Two Memristor SPICE Models and Their Applications in Microwave Devices

This paper presents two simple SPICE circuit models of the memristor using two different kinds of integrators. These models expand and simplify the previous methods of solving the memristor's modeling equations presented by Hewlett–Packard Lab. The behaviors of the two memristor models are investigated when they are excited by a sinusoidal voltage source. Both models satisfy the general features of memristive systems such as having a zero-crossing property in the form of an i–v Lissajous figure. In order to explore the unique characteristics and applications of the memristor in microwave devices, first we incorporate the memristor in a microstrip transmission line as a load. We do the analysis using a finite-difference time-domain simulator integrated with a nonlinear SPICE circuit solver. Furthermore, we design a reconfigurable microstrip bandpass filter based on a memristor-loaded resonator, and utilize a memristor as a carrier-wave modulator connecting the microstrip patch antenna to the ground.

Highly Selective Reconfigurable Filter for UWB Systems

A novel highly selective compact reconfigurable filter with a switchable notched band for ultrawideband (UWB) systems is presented. The proposed filter exhibits two distinct features by altering switching device such as PIN diode (BAP65-02) in this case. First, a switchable notched band is generated which facilitates a rejection at 3.5 GHz to avoid interferences from the WiMAX systems. Later, a reconfigurable filter is developed which changes from bandpass to bandstop at the same UWB (3.1-5.2 GHz) spectrum. The filter shows very low pass-band insertion loss and five transmission zeros are created between passband edges to enhance the signal selectivity and broad rejection at the stopband. A filter sample is fabricated to provide an experimental verification on the proposed filter. The proposed filter is able to achieve significant size reduction as compared to an conventional reconfigurable filters and bandpass filters with notched band.

Reconfigurable bandpass filter with center frequency and bandwidth control

ABSTRACTThis article presents a bandpass filter with independent center frequency and bandwidth control. It is based on four frequency‐reconfigurable resonators arranged in a series cascade of a second‐order bandpass filter and a dual‐behavior resonator. A measured bandpass filter response with variable bandwidth between 440 and 0 MHz is demonstrated at 3.6 GHz. The center frequency of the filter can be continuously varied between 2.76 and 3.79 GHz (1.4:1) with continuous bandwidth variation between 300 and 100 MHz (3:1) for a minimum out‐of‐band isolation of −15 dB and insertion loss between 0.76 and 2.5 dB. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2745–2750, 2013

Highly linear microstrip wideband bandpass filter with switchable notched band for wireless applications

AbstractThis article presents a highly linear reconfigurable bandpass filter embedded with a switchable notch structure to get a band‐notched characteristic at a specified frequency.A single PIN diode (BAP65‐02) is used for the purpose of switching the notch. An optical switch, comprised of a silicon dice activated using near infrared light is also investigated as an alternative to the PIN diode. While the PIN diode or the optical switch is in the ON state this reconfigurable filter behaves as a bandpass filter with a notch at 2.4 GHz in order to reject WLAN interference while a full band response is obtained in the OFF state. The proposed filter is able to achieve good linearity using PIN diode with IIP3 of 47 dBm and there is no significant loss. A prototype is fabricated, and measured results are compared to simulations. A good agreement has been achieved between simulated and measured results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1331–1335, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27585

A Reconfigurable Compact Coupled Line Multiple-Band Bandpass Filter

This study proposes a circuit structure with reconfigurable multiple bands bandpass filter. This circuit can provide a triple-band or dual-band bandpass facility by adjusting two open stubs (L6 and L7) location. The circuit design used three sections of transmission line in series, the two sets of the coupled lines connected to the gap in each transmission line, and two open stubs in the appropriate locations. The design and manufacturing of the circuit structure is innovative and simple. The center frequencies of the triple-band bandpass filter are set at 2.4, 4.2, and 6.5 GHz, respectively, while the center frequencies of the dual-band bandpass filter are the two lower pass band of the triple-band bandpass filter at 2.4 and 4.2GHz. The filters were simulated using the full-wave electromagnetic simulator, IE3D, and measured by Anritsu-37269D. The simulated and measured results show good agreement in the frequency of interest.

High linearity microstrip bandpass filter with electronically tunable notch

A high linearity reconfigurable bandpass filter embedded with a tunable notch structure has been presented for future wideband wireless communication applications. A single varactor diode (BB135-NXP) is used for the purpose of tuning the notch. The linearity of the varactor-tuned bandpass filter is also evaluated. The proposed filter is able to achieve a good linearity with IIP3 of 37, 46, and 45 dB at 2.3, 2.4, and 2.5 GHz, respectively, and with no significant loss. Simulations have been verified by the measurements of a fabricated prototype. A good agreement has been achieved simulated and measured results.