Showing papers on "Band-stop filter published in 2014"

A Novel Grid Synchronization PLL Method Based on Adaptive Low-Pass Notch Filter for Grid-Connected PCS

Abstract: The amount of distributed energy resources (DERs) has increased constantly worldwide. The power ratings of DERs have become considerably high, as required by the new grid code requirement. To follow the grid code and optimize the function of grid-connected inverters based on DERs, a phase-locked loop (PLL) is essential for detecting the grid phase angle accurately when the grid voltage is polluted by harmonics and imbalance. This paper proposes a novel low-pass notch filter PLL (LPN-PLL) control strategy to synchronize with the true phase angle of the grid instead of using a conventional synchronous reference frame PLL (SRF-PLL), which requires a d-q-axis transformation of three-phase voltage and a proportional-integral controller. The proposed LPN-PLL is an upgraded version of the PLL method using the fast Fourier transform concept (FFT-PLL) which is robust to the harmonics and imbalance of the grid voltage. The proposed PLL algorithm was compared with conventional SRF-PLL and FFT-PLL and was implemented digitally using a digital signal processor TMS320F28335. A 10-kW three-phase grid-connected inverter was set, and a verification experiment was performed, showing the high performance and robustness of the proposal under low-voltage ride-through operation.

Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection

Abstract: A compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4_epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36–6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context.

Design of Ultra-Wideband Bandpass Filters With Fixed and Reconfigurable Notch Bands Using Terminated Cross-Shaped Resonators

Abstract: In this paper, a novel terminated cross-shaped resonator (TCSR) is analyzed and used to design ultra-wideband (UWB) bandpass filters (BPFs) with fixed and reconfigurable notch bands. It is found that the TCSR can exhibit a maximum three poles and two zeros when open and short terminations are applied. The intrinsic zero is simply used for the implementation of notch bands offering systematic design and flexible tuning capabilities. Bandwidth can also be kept unchanged when tuning a notch within the UWB passband. In contrast to common band-notched UWB BPFs using additional notch resonators, only a single TCSR is required to realize band-notched UWB filters. Three UWB BPF prototypes, including a four-pole filter with 94.7% fractional bandwidth (FBW) and a notch band at 5.8 GHz, a five-pole filter with 111% FBW and dual notch bands at 4.3/9.1 GHz, and a four-pole filter with 82.4% FBW and reconfigurable notch band from 4.6 to 6.5 GHz are designed and experimentally characterized. Their experimental characterizations are in good agreement with theoretical analysis validating a simple approach of band-notched UWB BPF design.

Analysis and Design of a High-Order Discrete-Time Passive IIR Low-Pass Filter

Abstract: In this paper, we propose a discrete-time IIR low-pass filter that achieves a high-order of filtering through a charge-sharing rotation. Its sampling rate is then multiplied through pipelining. The first stage of the filter can operate in either a voltage-sampling or charge-sampling mode. It uses switches, capacitors and a simple gm-cell, rather than opamps, thus being compatible with digital nanoscale technology. In the voltage-sampling mode, the gm-cell is bypassed so the filter is fully passive. A 7th-order filter prototype operating at 800 MS/s sampling rate is implemented in TSMC 65 nm CMOS. Bandwidth of this filter is programmable between 400 kHz to 30 MHz with 100 dB maximum stop-band rejection. Its IIP3 is +21 dBm and the averaged spot noise is 4.57 nV/$surd$ Hz. It consumes 2 mW at 1.2 V and occupies 0.42 mm 2.

Microstrip Line Negative Group Delay Filters for Microwave Circuits

Abstract: This paper presents a novel approach to the design and implementation of a distributed transmission line negative group delay filter (NGDF) with a predefined negative group delay (NGD) time. The newly proposed filter is based on a simple frequency transformation from a low-pass filter to a bandstop filter. The NGD time can be purely controlled by the resistors inserted into the resonators. The performance degradation of the NGD time and signal attenuation (SA) of the proposed NGDF according to the temperature dependent resistance variation is also analyzed. From this analysis, it is shown that the NGD time and SA variations are less sensitive to the resistance variation compared to those of the conventional NGD circuit. For an experimental validation of the proposed NGDF, a two-stage distributed microstrip line NGDF is designed, simulated, and measured at an operating center frequency of 1.962 GHz. These results show a group delay time of -7.3 ns with an SA of 22.65 dB at the center frequency and have good agreement with the simulations. The cascaded response of two NGDFs operating at different center frequencies is also presented in order to obtain broader NGD bandwidth. NGDFs with good reflection characteristics at the operating frequencies are also designed and experimentally verified.

Synthesis Model and Design of a Common-Mode Bandstop Filter (CM-BSF) With an All-Pass Characteristic for High-Speed Differential Signals

Abstract: A new common-mode bandstop filter (CM-BSF) with an all-pass performance (from dc to 9 GHz) for differential signals is proposed by using a C-shaped patterned ground structure (PGS) with meandered signal lines on a two-layer printed circuit board (PCB). This technique can successfully generate two close transmission zeros in common-mode within the frequencies of concern. A corresponding equivalent circuit model is established to predict the filter behaviors, and a formula for common-mode transmission zeros is derived based on the circuit model. Next, a design method is developed and a synthesis procedure is proposed. According to the procedure, a wideband CM-BSF is synthesized and fabricated on a two-layer PCB. In addition, the simulation and experiment results are demonstrated to verify the technique and show excellent performance of the proposed CM-BSF. It is shown that common-mode noise can be suppressed over 10 dB from 1.9 to 8.9 GHz with 130% fractional bandwidth (FBW) while the insertion loss of differential-mode can be kept less than 3 dB from dc to 9 GHz. The electrical size is only 0.21 λ g ×0.21 λ g , where λ g is the wavelength of the stopband central frequency. To sum up, the proposed CM-BSF has merits of low cost (two layer), a simple geometric structure, a compact size, and a large common-mode FBW. Most importantly, the filter can keep good signal integrity of the digital differential signals due to its all-pass characteristic.

Wideband co-site interference cancellation based on hybrid electrical and optical techniques

Abstract: A wideband co-site co-channel interference cancellation system (ICS), based on hybrid electrical and optical techniques, is proposed and is experimentally demonstrated. The demonstrated cancellation system subtracts the in-band wideband interfering signal from the received signal, such that the weak signal of interest (SOI) can be recovered. Our system utilizes a broadband radio frequency (RF) Balun transformer to invert the phase of the interfering signal, while electro-absorption modulated lasers are used for converting the RF signals into the optical domain to enable fine adjustment with the hybrid ICS. We experimentally achieve 45 dB of cancellation over a 220 MHz bandwidth, and over 57 dB of cancellation for a 10 MHz bandwidth, at a center frequency of 900 MHz. The proposed system also experimentally shows good cancellation (30 dB) over an enormously wide bandwidth of 5.5 GHz. To the best of our knowledge, this is the first demonstration of such a wide bandwidth cancellation with good cancellation depth. This property is extremely useful when there are multiple interference signals at various frequency bands. The proposed hybrid ICS has a spurious-free dynamic range of 93.2 dBm/Hz(2/3). Moreover, a 10 Gb/s SOI is recovered from a strong interfering signal, sweeping over 3 GHz bandwidth. A widely open eye diagram, as well as error-free bit-error rate measurements, is experimentally achieved, with the use of the hybrid ICS. The approach also works well for various frequency bands that are within the bandwidth of the Balun transformer and electro-absorption modulated lasers.

Direct-Coupled Cavity Filter in Ridge Gap Waveguide

Abstract: This paper describes a novel design for a direct-coupled cavity filter realization using a ridge gap waveguide technology. A ridge gap waveguide transmission line with two coaxial feed connectors is designed and operated within the frequency band of 10-13 GHz. A cavity is coupled to the transmission line to achieve bandstop filter characteristic. Then, the structure of the filter is modified in a way to generate a bandpass feature. The final manufactured prototype is a fourth-order bandpass filter, operating at the center frequency of 11.59 GHz with a bandwidth of 72 MHz. The proposed design has potential applications in channeling filters for telecommunication satellites.

0.7–1.0-GHz Reconfigurable Bandpass-to-Bandstop Filter With Selectable 2- and 4-Pole Responses

Abstract: A 0.7-1.0-GHz reconfigurable bandpass-to-bandstop filter with selectable 2- and 4-pole responses is presented. The proposed filter can act as a 2- or 4-pole bandpass or bandstop filter by changing the coupling paths using zero-value coupling coefficients. The 4-pole bandpass filter mode also includes bandwidth control. The filter is built on a Duroid substrate with e r=10.2 and h=25 mil. The center frequency tuning, as well as the bandpass-to-bandstop transformation and the selection of the number of poles are achieved using silicon varactor diodes and RF microelectromechanical systems switches. In the 2- and 4-pole bandpass modes, an insertion loss of 4.9-2.9 and 6.1-4.8 dB is measured at 0.71-0.99 and 0.72-1.01 GHz, respectively. The 4-pole bandpass mode also shows a bandwidth tuning of 28-85 MHz at 0.9 GHz. In the 2- and 4-pole bandstop modes, rejection levels of 24-28 and 32-41 dB are measured at 0.64-0.96 and 0.71-0.96 GHz, respectively. The application areas are in reconfigurable filters for wideband radios under high interference environments.

Improving High-Frequency Performance of an Input Common Mode EMI Filter Using an Impedance-Mismatching Filter

Abstract: This letter investigates into the impedance interaction between the electromagnetic interference (EMI) filter and the noise propagation path, and its influences on the filter design. It proves that the impedance resonance in the propagation path decreases the filter's high-frequency in-circuit attenuation. This letter proposes a method to improve the filter's high-frequency performance using an impedance-mismatching filter. The impedance-mismatching filter damps the resonance in the common mode (CM) noise propagation path and eliminates the high-frequency noise spike. By applying this method in the filter design, the CM inductor of the EMI filter can be significantly reduced since the EMI filter avoids the overdesign caused by its high-frequency performance degradation, and the filter can potentially achieve high power density. This letter also proposed a design procedure for this impedance-mismatching filter. An improved EMI filter design method considering this impedance mismatching is also proposed in this letter.

A Fast, robust algorithm for power line interference cancellation in neural recording

Abstract: Power line interference may severely corrupt neural recordings at 50/60 Hz and harmonic frequencies. In this paper, we present a robust and computationally efficient algorithm for removing power line interference from neural recordings. The algorithm includes four steps. First, an adaptive notch filter is used to estimate the fundamental frequency of the interference. Subsequently, based on the estimated frequency, harmonics are generated by using discrete-time oscillators, and then the amplitude and phase of each harmonic are estimated through using a modified recursive least squares algorithm. Finally, the estimated interference is subtracted from the recorded data. The algorithm does not require any reference signal, and can track the frequency, phase, and amplitude of each harmonic. When benchmarked with other popular approaches, our algorithm performs better in terms of noise immunity, convergence speed, and output signal-to-noise ratio (SNR). While minimally affecting the signal bands of interest, the algorithm consistently yields fast convergence and substantial interference rejection in different conditions of interference strengths (input SNR from -30 dB to 30 dB), power line frequencies (45-65 Hz), and phase and amplitude drifts. In addition, the algorithm features a straightforward parameter adjustment since the parameters are independent of the input SNR, input signal power, and the sampling rate. The proposed algorithm features a highly robust operation, fast adaptation to interference variations, significant SNR improvement, low computational complexity and memory requirement, and straightforward parameter adjustment. These features render the algorithm suitable for wearable and implantable sensor applications, where reliable and real-time cancellation of the interference is desired.

Ultracompact plasmonic loop–stub notch filter and sensor

Abstract: A new nanoplasmonic notch filter and a biosensor, based on the loop–stub configuration, are proposed and studied. Our finite-difference time-domain simulations reveal that the resonant mode of the proposed structure can be easily controlled by varying the width of the horizontal branch of the loop–stub structure. The proposed plasmonic biosensor has a high sensitivity and a remarkably large figure-of-merit. Besides the advantages of easy fabrication, the device has a compact size of only a few hundred nanometers in width and length. The special features of the proposed structure and the device concept introduced in this work are applicable in the realization of various integrated components for the development of plasmonic biosensors.

Six Order Cascaded Power Line Notch Filter for ECG Detection Systems with Noise Shaping

Abstract: This paper presents the design of an operational transconductance amplifier-C (OTA-C) notch filter for a portable Electrocardiogram (ECG) detection system. A six order cascaded filter is utilized to reduce the effect of the power line interference at (50/60 Hz). The proposed filter is based on a programmable balanced OTA circuit. Based on this, PSPICE post layout simulation results for the extracted filter using 0.25 $$\upmu $$ μ m technology and operating under $$\pm $$ ± 0.8 V voltage supply are also given. The six order notch filter provides a notch depth of 65 dB (43 dB for 4th order), input referred noise spectral density with noise shaping of 9 $$\upmu $$ μ Vrms/ $$\surd $$ ? Hz at the pass band frequencies and 9 mVrms/ $$\surd $$ ? Hz at the notch (zero) frequency which provide noise shaping for the ECG signal. These results demonstrate the ability of the filter to be used for ECG signal filtering which is located within 150 Hz.

Compact UWB bandpass filter with triple notched bands using parallel U-shaped defected microstrip structure

Abstract: A novel compact ultra-wideband (UWB) bandpass filter (BPF) with triple sharply notched bands and good selectivity is proposed using a parallel U-shaped defected microstrip structure (UDMS). The initial UWB BPF comprises interdigital coupled lines and an E-shaped multiple-mode resonator to achieve two transmission zeros on both sides of the passband, thus improving skirt selectivity. Then, three parallel UDMSs are introduced, which have the properties of achieving the triple band-notched characteristics and providing a high degree of adjusting freedom. To validate the design theory, a microstrip UWB BPF with three notched bands centred at 5.2, 5.8 and 8.0 GHz, respectively, is designed and fabricated. Both the simulation and the experimental results are provided which have good agreement.

A fast, robust algorithm for power line interference cancellation in neural recording

Abstract: Objective. Power line interference may severely corrupt neural recordings at 50/60 Hz and harmonic frequencies. The interference is usually non-stationary and can vary in frequency, amplitude and phase. To retrieve the gamma-band oscillations at the contaminated frequencies, it is desired to remove the interference without compromising the actual neural signals at the interference frequency bands. In this paper, we present a robust and computationally efficient algorithm for removing power line interference from neural recordings. Approach. The algorithm includes four steps. First, an adaptive notch filter is used to estimate the fundamental frequency of the interference. Subsequently, based on the estimated frequency, harmonics are generated by using discrete-time oscillators, and then the amplitude and phase of each harmonic are estimated by using a modified recursive least squares algorithm. Finally, the estimated interference is subtracted from the recorded data. Main results. The algorithm does not require any reference signal, and can track the frequency, phase and amplitude of each harmonic. When benchmarked with other popular approaches, our algorithm performs better in terms of noise immunity, convergence speed and output signal-to-noise ratio (SNR). While minimally affecting the signal bands of interest, the algorithm consistently yields fast convergence ( 30 dB) in different conditions of interference strengths (input SNR from −30 to 30 dB), power line frequencies (45–65 Hz) and phase and amplitude drifts. In addition, the algorithm features a straightforward parameter adjustment since the parameters are independent of the input SNR, input signal power and the sampling rate. A hardware prototype was fabricated in a 65 nm CMOS process and tested. Software implementation of the algorithm has been made available for open access at https://github.com/mrezak/removePLI. Significance. The proposed algorithm features a highly robust operation, fast adaptation to interference variations, significant SNR improvement, low computational complexity and memory requirement and straightforward parameter adjustment. These features render the algorithm suitable for wearable and implantable sensor applications, where reliable and real-time cancellation of the interference is desired.

0.73–1.03-GHz Tunable Bandpass Filter With a Reconfigurable 2/3/4-Pole Response

Abstract: This paper presents a tunable bandpass filter with a reconfigurable-pole response. 2-, 3-, and 4-pole states can be obtained based on employing series resonators with RF switches. The synthesis for the proposed filter is established, and the bandwidth for each pole state can be selected based on theory. The filter is built on a Duroid substrate with er=10.2 and h=25 mil. The tuning for the center frequency is done using Schottky diodes, and the selection of the filter poles is achieved using RF microelectromechanical systems switches. A tuning of 0.73-1.03 GHz is achieved with a 1-dB fractional bandwidth of 3.9%-5.2%. The rejection levels at 200-MHz offset frequency of 2-, 3-, and 4-pole states are 28, 36, and 45 dB, respectively. This filter topology can find applications in reconfigurable radios with dynamic rejection levels.

Switchable and Tunable Notch in Ultra-Wideband Filter Using Electromagnetic Bandgap Structure

Abstract: A simple technique to reconfigure a notch filter employing a 1-D electromagnetic bandgap (EBG) structure, which is capacitively coupled to a microstrip line, is presented in this letter. The resonant nature of the EBG creates a notch in the transmission band. The notch filter is made reconfigurable/tunable by introducing an additional capacitive structure to change the size (geometry) of the EBG unit cell. The structure is connected or disconnected to the main structure (unit cell) by means of a PIN diode or varactor diode. Its application in notched-band ultra wideband (UWB) filter is demonstrated. A 450 MHz change in notch frequency is observed using PIN diode, and 340 MHz tuning range is observed using varactor diode.

CMOS Compatible Reconfigurable Silicon Photonic Lattice Filters Using Cascaded Unit Cells for RF-Photonic Processing

Abstract: This paper presents an overview of a complementary metal-oxide-semiconductor-compatible, programmable, analog optical lattice filter based on silicon unit cells arrayed in large-scale photonic integrated circuits. The unit cell employs a combination of a ring resonator and a Mach-Zehnder interferometer with tunable phase elements in both of the paths. Each proposed unit cell contributes a separately controllable pole and zero pair. Under various configurations, we experimentally achieved >60-dB two-tone spurious-free dynamic range. For more sophisticated signal processing, we experimentally demonstrated an optical lattice filter with four cascaded unit cells capable of dynamically reconfiguring between a bandpass filter and a notch filter. The reconfiguration of the unit-cell and four-cell silicon lattice filter is based on a recursive algorithm, which brings new possibilities to RF photonic processing and a wide range of applications with design scalability to a large number of poles and zeros. The experimental results and the recursive algorithms show potentials for scaling to higher order filter designs.

All-optical tunable notch filter by use of Kerr nonlinearity in the graphene microribbon array

Abstract: We report a numerical study on the optical tuning of a notch filter comprised of an array of engineered graphene microribbons. The notch on the normal incidence transmission spectra is created due to light–plasmon coupling in graphene. Besides investigating the effect of structural parameters and electrostatic gating on the graphene plasmon excitation, we particularly examine the modulation of transmission with incident light intensity based on the significant optical Kerr effect in graphene. Our numerical simulation with the finite difference time domain numerical method reveals that considerable variation in the transmission up to 12.15 dB can be effectively achieved by increasing the irradiance intensity up to 0.68 MW/cm2, which is adequately below the graphene threshold damage. The presence of well-known techniques to fabricate and characterize graphene sheets such as chemical vapor deposition and Raman spectroscopy makes such a one-atom-thick terahertz filter feasible.

Small-size high-selectivity bandstop filter with coupled-line stubs for dual-band applications

Abstract: A novel coupled-line stub is proposed for the design of a novel dual-band small-size bandstop filter (BSF). This kind of coupled-line dual-band BSF features a compact and simple structure, flexible frequency-ratio adjustment and high selectivity. To verify the proposed circuit structure and design approach, a microstrip example has been fabricated and measured. The measured results show a good agreement with the simulated responses.

An active damper to suppress multiple resonances with unknown frequencies

Abstract: The increasing use of power electronics devices tends to aggravate high-frequency harmonics and trigger resonances across a wide frequency range into power systems. This paper presents an active damper to suppress multiple resonances with unknown frequencies. The active damper is realized by a high-bandwidth power converter that can selectively dampen out the wideband resonances. A cascaded adaptive notch filter structure is proposed to detect the frequencies of resonances, which makes the active damper different from the resistive-active power filter for harmonic resonance suppression. The performance of the active damper is validated by implementing it to suppress the resonances in a grid-connected inverter with a long power cable. The results show that the active damper can become a promising approach to stabilizing the future power electronics based power systems.

Multi-band bandstop filter using inner T-shaped defected microstrip structure (DMS)

Abstract: In this paper, inner T-shaped defected microstrip structure (DMS) is studied, and new bandstop filters with a single band, dual-band and tri-band are developed. The new designs have adjustable multi-band operation and simple circuit topologies, and the symmetrical periodic T-shaped DMS introduces transmission zeros which improve the filter frequency selectivity greatly. The circuit sizes are also reduced because of the inner T-shaped DMS introduces more resonances in a frequency range of 10 GHz but without the requirement of certain coupled lines or resonators. The dual-band and tri-band designs are demonstrated by measurement.

Systems and methods for bandlimiting anti-noise in personal audio devices having adaptive noise cancellation

Abstract: A method may include adaptively generating an anti-noise signal from filtering a reference microphone signal with an adaptive filter in conformity with an error microphone signal and the reference microphone signal The method may also include adjusting the response of the adaptive filter by combining injected noise with the reference microphone signal and receiving the injected noise by a copy of the adaptive filter so that the response of the copy is controlled by the adaptive filter adapting to cancel a combination of the ambient audio sounds and the injected noise and controlling the response of the adaptive filter with the coefficients adapted in the copy, whereby the injected noise is not present in the anti-noise signal and wherein each of a sample rate of the copy and a rate of adapting of the adaptive filter is significantly less than a sample rate of the adaptive filter

The Detection of Resonance Frequency in Motion Control Systems

Abstract: Because of the flexibility of mechanical linkages and high control gains, mechanical resonance may occur, causing torsional vibrations between the motor and load in servo control systems. These vibrations generate velocity and positioning errors for the control system and may damage the system components. This study presents a resonance frequency tracking scheme for servo control systems. The scheme uses velocity error and bandpass filters to track resonance frequencies. After detection, a notch filter in series to the current command is enabled to suppress the vibration. This scheme can be employed during the initial setup and for online resonance frequency tracking. In addition, the proposed scheme can be used to identify all vibrational frequencies in systems with multiple resonant frequencies.

Differential Wideband Bandpass Filters With Enhanced Common-Mode Suppression Using Internal Coupling Technique

Abstract: A differential wideband bandpass filter (WBPF) with enhanced common-mode (CM) suppression is presented. The study about this modified branch-line structure with internal coupling sections shows that the proposed filter demonstrates a good wideband bandpass filtering response under the differential mode (DM) operation, meanwhile it also functions as a CM bandstop filter with wide and high rejection owing to the multiple transmission zeros brought by the internal coupling mechanism. To verify the design concept, one filter example has been designed, fabricated and measured. The fabricated differential WBPF has a DM 3 dB fractional bandwidth (FBW) of 59.5%. Moreover, it demonstrates an ultra-wide CM stopband from 0.82 to 2.8 GHz over 40 dB, representing a 40 dB FBW of 109.4%.

Controllable multiband terahertz notch filter based on a parallel plate waveguide with a single deep groove

Abstract: The influence of the air gap on the response of transmission for a transverse-electric mode parallel plate waveguide with a single deep groove has been experimentally studied. As the air gap is larger than the resonant wavelength of a high-order cavity mode in a single deep grooved waveguide, only the fundamental cavity mode can be excited and the single resonance (band) can be observed in a transmission spectrum. The decrease of the air gap can not only efficiently push the radiation of the fundamental cavity mode into the deep groove but also excite the high-order cavity modes, resulting in multiple resonances (multiband) in the corresponding spectrum. Based on the above observations, a tunable multiband terahertz notch filter has been proposed and the variation of the air gap has turned out to be an effective method to select band number. Experimental data and simulated results verify this band number tunability.

A Dual-Band Bandpass Filter With Widely Separated Passbands

Abstract: A novel and compact design of a dual-band filter with widely separated passbands is proposed. Applications of such a device can be found in systems where a single device is responsible for both transmission and reception. The proposed filter is composed of resonators working on two distinct modes. The proposed dual-mode structure offers a good rejection of unwanted resonances, producing a widely separated dual-band response. The idea is demonstrated with the design of a four-pole filter comprising two dual-mode structures and the concept is verified experimentally by the measurement of a fabricated prototype. Finally, a six-pole filter is proposed, showing the possibility of designing higher order filters.

New Compact Triple-Passband Bandpass Filter Using Multipath-Embedded Stepped Impedance Resonators

Abstract: This letter presents a new resonator configuration to design a triple-passband filter with high passband selectivity and compact circuit size. The filter includes two multipath-embedded stepped impedance resonators (SIRs), connected with magnetically coupling by via hole technique at the symmetric plane of the filter. The multipath-embedded SIR is designed at 1.575, 2.45, and 3.5 GHz. The resonant frequencies can be easily controlled by tuning impedance ratio K i and length ratio αi (where i = 1, 2, and 3) of the multipath-embedded SIR. This study provides an effective method to easily design the triple-passband filter with compact circuit size, high passband selectivity and low insertion loss.

Octave tunable lumped-element notch filter with resonator-Q-independent zero reflection coefficient

Abstract: A bandstop filter architecture with small form factor and very large attenuation over an octave frequency tuning range is demonstrated The architecture provides a benefit of resonator-Q-independent zero reflection coefficient at the center frequency, and is demonstrated with a tuning range of 5504 to 13334 MHz varactor-tuned two-resonator notch filter with minimum notch attenuation of 64 dB, 3-dB fractional bandwidth (FBW) of 1086% to 322% over the tunable frequency range and passband up to 3565 MHz, resulting in a 648-to-1 upper passband, in a footprint of 227×165 cm 2 The unloaded quality factor (Q-factor) was extracted to be 62 at 13334 MHz