Stepped Impedance Low-pass Filter Research Articles

Stepped Impedance Optimum Short-Circuited Stub 1–6 GHz and 6–10 GHz Bandpass Filters for Multi-standard Radio

This article presents two ultra-broadband bandpass filter (BPF) designs for multi-standard applications, operating from 1–6 GHz and 6–10 GHz, with wide stopband characteristics. 1–6 GHz BPF (Filter 1) is based on the circuit model for an optimum distributed bandpass filter consisting of 3 shunt short-circuited stubs separated by non-redundant unit elements. By varying the length ratio between the unit elements and stubs and introducing stepped impedance in the unit elements, a 143% fractional bandwidth (FBW) is achieved, which is 20% higher than that obtained through the conventional optimum shunt short-circuited stub method. In addition, a stepped impedance elliptic lowpass filter was cascaded to achieve wide stopband characteristics from 7 GHz to 20 GHz. Filter 2 (6–10 GHz) is constructed by cascading a shunt short-circuited stub optimum high pass filter having a stepped impedance unit element with a stepped impedance low pass filter. The analytical model, transmission line equivalent circuit model, and full wave electromagnetic simulated model are presented along with the measured results. The measured in-band return loss of Filter 1 and Filter 2 is >12 dB, and the measured insertion loss is < 2 dB. The measured group delay of Filter 1 and Filter 2 is <0.8 ns.

Design of Modified Jacobi Microstrip Lowpass Filter for L-Band Application

In this brief, a design of microstrip lowpass filter with the 1 GHz cutoff frequency is revisited, where a class of modified Jacobi polynomials is used for the filter design. The optimization procedure for these filters includes the passband return loss minimization and the roll-off factor enhancement using the magnitude correction of the transmission coefficient. Mentioned correction is performed by introducing the multiple transmission zeros such that LC ladder prototype filter can be realized symmetrically. Three seventh degree filters for L-band applications are realized and simulated: allpole, with a single and double transmission zeros. It is shown that, among these three stepped impedance lowpass filters realizations, the filter with simple transmission zeros offers the best performance.

Monolithically Integrated THz Photodiodes With CPW-to-WR3 E-Plane Transitions for Photodiodes Packages With WR3-Outputs

An indium phosphide (InP)-based E-plane transition for monolithically integrating terahertz photodiodes with standard rectangular waveguide (WR)-outputs is presented for all standard WR-frequency bands from 0.22 THz to 2.2 THz, i.e., from WR3 to WR0.51. The integration concept comprises a modified uni-travelling carrier photodiode (MUTC-PD) chip, an E-plane transition and a stepped impedance low-pass filter (LPF), which are all monolithically integrated on InP substrate. The E-plane transition converts the quasi-TEM coplanar waveguide (CPW) mode of the MUTC-PD output to the dominant TE10 mode of the WR. To our knowledge, this is the first frequency-scalable monolithic integration concept that enables packaging of photodiodes with standard WR-outputs up to 2.2 THz. The recommended thickness of the InP substrate and the proposed E-plane transitions design parameters are investigated by numerical analysis to achieve minimum insertion loss (IL) and a wide operational bandwidth (BW). The presented optimized transitions exhibit a maximum IL of 1.4 dB, a return loss (RL) better than 10 dB and a minimum 1 dB IL BW of 92.23% for all WR-bands up to 2.2 THz. To prove the proposed monolithic integration concept, a MUTC-PD is integrated with a CPW-to-WR3 E-plane transition (220-320 GHz) on a 95 m-thick InP substrate. At 300 GHz, the maximum achieved RF output power of the fabricated MUTC-PD chip is -12.4 dBm at a photocurrent of 18.5 mA. For experimental characterization, the MUTC-PD chip with the integrated E-plane transition has been mounted on a 1 mm-thick soda-lime glass substrate as carrier and it has been manually aligned within a WR-3 together with an adjustable back-short. Due to non-perfect alignment of the chip and the back-short as well as the additional losses and substrate modes due to the thick glass carrier, the calculated average IL is increased to 5.3 dB. Experimentally, an average IL of 8.6 dB is measured within the WR3-band from 220 GHz to 320 GHz. Integration of the chip in a real package without misalignment and without the glass carrier is expected to improve the IL by ~4.8 dB.

Design of Microstrip Low-pass and Band-pass Filters using Artificial Neural Networks

Usually the design of microstrip filters is done using simulators and classical approximation methods as Butterworth and Chebyshev, these techniques takes a lot of time to run for designing filters. In this paper we develop a faster artificial neural network model for designing a microstrip low-pass and band-pass filters for all rang of operating frequency , when the input are the dimensions of filter, operating frequency, the features of substrate, and the output are the transmission and reflection coefficients. The database uses for training this model is generated by a linear simulator based on circuits model. Two filters designed by the developed model are a stepped impedance low-pass filter with a cut-off frequency of 1 GHz and a parallel coupled-line band-pass filter with fractional bandwidth of 25 % and a central frequency of 2.45 GHz. The results of simulation are compared with desired results and the effectiveness of this method has been proven.

Design and Implementation of Ultrafast Broadband Sweep Source based on AD9914

To address a technical difficulty of long scanning cycle of broadband (100 MHz~900 MHz) frequency sweep source, an ultrafast broadband sweep source was designed based on the basic principle of direct digital-frequency synthesis (DDS) theory by using the high-performance DDS chip AD9914. During the design, the DSP28335 chip was used as the control device. The designed source can output 100MHz~900 MHz swept-frequency signals and it can realize sawtooth wave frequency-modulated signals in the shortest cycle (8us) by configuring the digital ramp generator in the chip. Moreover, a microstrip stepped impedance low-pass filter was designed using ADS to eliminate spurious signals in the direct synthesizer and decrease the in-band attenuation, thus making the curve flatter. According to final test and experimental data analysis, the designed sweep source has a large output broadband, short sweeping cycle and strong inhibition of spurious signals. It possesses great application values.

A new design of high output voltage rectifier for rectenna system at 2.45 GHz

&lt;p&gt;This paper deals with the design and achievement of a novel microstrip rectifier with high conversion efficiency and output voltage. Firstly, we have designed a rectifier based on HSMS2820 Schottky diodes by using a series topology to convert the electromagnetic energy into DC power. Then, a stepped-impedance low pass filter was implemented to filter the unwanted harmonics generated by the non-linear Schottky diode. Both of the structures have been simulated and fabricated on an FR4 substrate with dielectric permittivity constant 4.4, thickness of 1.6 mm and loss tangent of 0.025. Good performances were confirmed throughout the measurement results and an interesting output voltage was observed.&lt;/p&gt;

A 219–266 GHz LO-tunable direct-conversion IQ receiver module in a SiGe HBT technology

AbstractThis paper presents a fully-integrated direct-conversion fundamentally-operated mixer-first quadrature receiver module with a tunable LO in the 219–266 GHz band. It has been implemented in a 0.13-μm SiGe heterojunction bipolar transistor technology. It includes an on-chip LO path driven externally from the printed circuit board (PCB) connector level at 13.6–16.7 GHz. A hybrid coupler generates the quadrature LO signal, which drives a pair of double-balanced fundamentally-operated down-conversion mixers, whose RF ports are connected to a wideband lens-integrated on-chip ring antenna. The chip-on-lens assembly is placed in the recess of a high-speed PCB and wire-bonded. To compensate the inductive behavior of the wire-bond interconnection between the chip and the PCB at the high-speed IF outputs, an on-board 8-section step-impedance low-pass filter has been implemented. The module shows a 47 GHz 3-dB radio frequency/local oscillator operation bandwidth (BW), a peak conversion gain of 7.8 dB, a single-side-band noise figure of 11.3 dB, and a 3-dB IF BW of 13 GHz. The in-phase and quadrature amplitude imbalance stays below 1.58 dB for the 210–280 GHz band. The down-conversion and the baseband stages consume together 75.5 mW, while the LO path 378 mW. The maximum data-rate achieved with this receiver in combination with the transmitter presented in [1–3] is 60 Gbps for quadrature phase shift keying modulation.

Microwave Heating Visualization for Carbon Fibers Composite Material: Development of Tunable Microstrip Structures

The visualization of carbon fibers polyether ether ketone (PEEK) composite material heating for a grounded coplanar waveguide and a stepped impedance low-pass filter by the thermal camera is performed. The purpose of such visualization is to characterize electromagnetic field influence on the diagonally anisotropic composite material and find out its application opportunity. COMSOL Multiphysics simulation has been done in order to understand heating principles and origin. Experimental results were in a good agreement with simulations and they showed that the characteristics of the microstrip structures can be modulated/tuned by simple rotation of the composite material. Finally, a tunable application by the carbon/PEEK composite material for the microstrip low-pass filter was developed due to the microwave absorption selectivity dependence on the composite material orientation.

Spurious free independently controllable compact quad‐band filter using folded T‐shaped stub loaded modified ring resonator

A compact spurious free, quad-band, band-pass filter (BPF) having independently controllable and widely spaced frequency bands is proposed. The design consists of a basic BPF to which the authors introduce transmission zeros (TZs) in the frequency response using T-shaped stubs loaded with a modified ring resonator (MRR) thereby creating the four passbands. This design results in very high band-to-band isolation. The TZs are obtained by transversal signal path cancellation and also due to the loaded T-shaped stubs. The BPF consists of a stepped impedance low-pass filter which provides spurious free out of band characteristics up to 20 GHz. By changing the tapping position of the MRR, the frequencies of the TZs can be adjusted to get the desired pass band characteristics. The proposed quad-band filter provides low-insertion loss (<1 dB) at the four passbands centred at 2.4, 5.1, 7.7 and 10.1 GHz. The simulation results of the filter are verified experimentally.

Multi Mode Resonators Based Triple Band Notch UWB Filter

A compact and highly selective triple band notch UWB (3.3 GHz -10.7 GHz) filter is presented. Low insertion loss UWB pass band characteristics is achieved by two coupled multi mode resonators (MMR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and MMR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). Desired triple band notch characteristics and sharp UWB filter characteristics are achieved by introducing transmission zeroes (TZs). Three band notches are implemented to mitigate the potential interferer signals at 4.42 GHz (Radio altimeter ITU band), 5.54 GHz (WLAN) and 7.64 GHz (Satellite communications). Wide upper stop band is realized by incorporating a stepped impedance low pass filter structure. The filter is realized on a RT/Duroid 5880 substrate (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.2 and thickness = 0.8 mm) and measured to validate the predicted results. The group delay of the filter is relatively constant and less than 0.45 ns over the desired pass band.

High-Efficiency Nanoplasmonic Wavelength Filters Based on MIM Waveguides

Two ultra-compact nanoplasmonic wavelength filters based on stepped impedance low-pass prototype filter in metal-insulator-metal waveguides are suggested. The transmission and reflection efficiency of both high-pass wavelength and long-wavelength cutoff filter is more than 93%, respectively. Simulation results reveal that similar to the tunability of the structure's transmission spectrum by changing the thickness of the insulator medium, the variations of the width of steps' discontinuities in the high-pass device not only provide an effective method to adjust the transmission peak/cutoff wavelength position, but also give rise to the structure to realize a long-wavelength cutoff filter. On the contrary, modifying the value of aperture length in the proposed long-wavelength cutoff filter gives the capability to control the cutoff wavelength. Moreover, changing the insulator medium to silica converts the device as a dual band bandpass filter at the wavelengths of 1300 and 1550 nm with efficiency of more than 85.2% and 78.1%, respectively. Hence, because of their excellent performance, features, and optimized size, they may have applications in high density photonic integrated circuits.

A Compact Printed Filtering Antenna With Good Suppression of Upper Harmonic Band

In this letter, a printed planar filtering antenna composed of the stepped-impedance dipole (SID), stepped-impedance resonator (SIR), and low-pass filter (LPF) is presented. The SIR is used as a parasitic element in proximity to the SID radiator to improve its upper band-edge selectivity and to widen its operation bandwidth. Our extensive study is at first conducted to exhibit that the upper harmonic band of radiation can be tremendously pushed upward by appropriately replacing the main dipole radiator and the parasitic resonant element with the SID and SIR. Next, a stepped-impedance LPF is employed to further effectively suppress the high-order harmonic band of radiation as quantitatively demonstrated. The measured reflection coefficient has achieved a wide fractional bandwidth up to 27.5%, covering a frequency range of 2.5–3.3 GHz, with $\vert{ S}_{11}\vert . In particular, its first harmonic band for radiation has been significantly extended from 7.2 GHz beyond 14.0 GHz as confirmed in simulation and experiment.

A Multi-Stub Lowpass Filter

The stepped-impedance lowpass filter is modified by replacing the low-impedance lines with lowpass transmission lines. The modified stepped-impedance lowpass filter is called a multi-stub lowpass filter because it is largely composed of open-circuited stubs. For experimental verification of the multi-stub filters, we design a 1 GHz seventh-order Butterworth LPF. The proof-of-concept prototype is a compact design that fits into a circuit size of $0.09\lambda_{g}\times 0.136\lambda_{g}$ on an RO4003 substrate. The measurement results show that the multi-stub lowpass filter retains the characteristics of a Butterworth filter in the passband, while substantially improves the performance in the transition and stopband regions. It achieves state-of-the-art performance compared to lowpass filters in the literature.

Millimeter-Wave Energy Harvesting Using &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$4\times4$&lt;/tex&gt;&lt;/formula&gt; Microstrip Patch Antenna Array

In this letter, an energy harvester at 35 GHz has been developed, which known as a rectenna. An array of a rectangular microstrip patch antenna with 16 elements was used to efficiently convert RF to dc signal. A step-impedance low-pass filter is used between the antenna and rectifier circuit to suppress second-order harmonic generated by the diode. A GaAs Schottky diode MA4E1317 was used in parallel with load as a half-wave rectifier circuit. The fabrication process is based on conventional optical photolithography to obtain an integrated circuit. The maximum RF-to-dc conversion efficiency of 67% was successfully achieved with input RF power of 7 mW at 35.7 GHz.

Graphene-Based Plasmonic Tunable Low-Pass Filters in the Terahertz Band

We propose the concept, synthesis, analysis, and design of graphene-based plasmonic tunable low-pass filters operating in the THz band. The proposed structure is composed of a graphene strip transferred onto a dielectric and a set of polysilicon DC gating pads located beneath it. This structure implements a stepped impedance low-pass filter for the propagating surface plasmons by adequately controlling the guiding properties of each strip section through graphene's field effect. A synthesis procedure is presented to design filters with desired specifications in terms of cut-off frequency, in-band performance, and rejection characteristics. The electromagnetic modeling of the structure is efficiently performed by combining an electrostatic scaling law to compute the guiding features of each strip section with a transmission line and transfer-matrix framework, approach further validated via full wave simulations. The performance of the proposed filters is evaluated in practical scenarios, taking into account the presence of the gating bias and the influence of graphene's losses. These results, together with the high miniaturization associated with plasmonic propagation, are very promising for the future use and integration of the proposed filters with other graphene and silicon-based elements in innovative THz communication systems.

A varactor-tuned bandpass filter based on lowpass filter and shorted stubs

This article presents a tunable bandpass filter (BPF) which is comprised of a chebyshev stepped-impedance lowpass filter (LPF), three shorted stubs, three varactors, and some blocking capacitors. Detailed design of the LPF, the effects of the shorted stubs, the schematic of the tunable BPF, and the tuning strategies are investigated. By tuning the reversed-bias voltages of the varactors, which are shunted with the low impedance of the stepped-impedance LPF, the operating frequency of the filter is changed. After the tunable BPF is designed and simulated, one experiment filter has been fabricated and tested. The measurement results of the experiment filter show that the center frequency of the tunable filter can be reconfigured from 1.09 to 2.44 GHz if the reversed-bias voltages are altered within 0–30 V. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:879–883, 2014

Wide‐stopband Wilkinson power divider with bandpass response

A wide-stopband Wilkinson power divider with bandpass response and good isolation is presented. A 3-terminal, 2-pole bandpass filter and two 3-pole lowpass filters are used to replace the two quarter-wavelength transformer in a conventional Wilkinson power. The divider consists of two shorted-circuited half-wavelength stepped-impedance resonators and two 3-pole microstrip stepped-impedance lowpass filters. Thus, the divider achieves not only a bandpass response but also a very wide stopband. For the upper stopband performance, the rejection level is >10 dB up to 22.2 times the centre frequency.

Improved performance step impedance lowpass filter

Performances of the conventional Butterworth step impedance lowpass filters (LPF) are significantly improved by placing transmission zero either closer to the cut-off frequency (fc) or away from it. It is achieved by using transverse resonance width of the capacitive line sections. We report method of designing transverse resonance type LPF (TR-LPF) for 5 to 11-pole filters. At fc=2.5GHz, we obtained selectivity in the range 113.3–56.66dB/GHz and 20–60dB rejection BW in the range 9.61–7.29GHz. The TR-LPF can suppress the stopband signal by 60dB up to 5fc. Insertion loss in passband is within 0.72dB. Improved performance of TR-LPF can be designed for fc up to 7.5GHz.

Simplified Prediction of Peak Power-Handling Capability for Stepped-Impedance Low-Pass Filters

Novel explicit formulas are introduced in this paper for the prediction of peak voltages and amplification factors in stepped-impedance coaxial and waveguide low-pass filters. Based on a coupling-matrix model and a simplified electromagnetic (EM) formulation, voltages in the filter critical areas are calculated analytically, without need of any 3-D EM simulations. Only filter prototype parameters are required in this method, which is therefore fast and considerably simplifies the power-handling analysis of corrugated filtering structures. The accuracy of the formulas is verified via commercial finite-difference time-domain software and multipactor breakdown test.

Design and integration of HTS filters with a Josephson device

A high-temperature superconducting (HTS) Josephson frequency down-converting module is demonstrated. An HTS monolithic frequency down-converting circuit and a biasing circuit board for the Josephson device are packaged into the module. The monolithic circuit consists of HTS filters and a Josephson oscillator-mixer device, integrated on a single 10 mm × 20 mm chip of Y Ba2Cu3O7−x (YBCO) film on MgO substrate. A compact, low-loss HTS step-impedance low-pass filter was designed for the intermediate frequency (IF) output port. The modeling, simulation and measurement results of the HTS low-pass filter are presented in this paper. The frequency response and dynamic range of the on-chip integrated HTS down-converting module are also described.