Microstrip-line Bandpass Filters Research Articles

Design of millimeter‐wave bandpass filters based on improved asymmetric parallel‐coupled microstrip line structure for direct detection system of CubeSat radiometer

AbstractIn this paper, two improved asymmetric parallel‐coupled microstrip bandpass filters with center frequencies of 89 GHz and 150 GHz were designed and implemented. The improvement of the circuit structure is based on the rotation of several asymmetric parallel‐coupled microstrip line segments, which achieves a great area reduction compared to the conventional structure. The improved bandpass filters were designed and optimized based on the conventional structure. The measured results show that the return loss of the W‐band bandpass filter is better than 16 dB and that of the D‐band bandpass filter is better than 15 dB within the passband. The insertion loss is less than 2.3 dB and 2.5 dB within the passband for W‐band and D‐band bandpass filters, respectively. These results verify the feasibility of the improved asymmetric parallel‐coupled microstrip line bandpass filter as a broadband pre‐filter for the direct detection system of a CubeSat radiometer.

Artificial intelligence–based design optimization of nonuniform microstrip line band pass filter

AbstractDesign optimization of many electromagnetic and multiphysics problems have multiscale issues that require a fast, efficient, and accurate surrogate‐based model to be used. Recently, in microwave engineering field, artificial intelligence–based models are being used for modeling of complex microwave stages. In all the studies, the main aim is to form models inner structure parameters, by using the given data to predict the linear/nonlinear relationships between given inputs and outputs. Herein, a surrogate‐based model of a nonuniform microstrip transmission line (NTL) with a typical application of design optimization of a band‐pass filter for ISM band application using deep learning (DL) and meta‐heuristic optimization has been presented. In order to have a computationally efficient and accurate optimization process, firstly a 3D EM unit element model of NTL has been designed. The training and test data sets are created based on different sampling methods. A DL regression model modified multilayer perceptron M2LP have been used for prediction of scattering parameters (S) of the NTL, with respect to the variation of geometrical design parameters. The proposed S‐parameters will then be used to calculate the equivalent S‐parameters of the cascading NTL to be used to calculate the NTL‐based microstrip band‐pass filter S‐parameter response. The optimal design parameters of each line used in the filter design have been determined using a fast and powerful optimization algorithm differential evolutionary algorithm.

Circularly polarized co-designed filtering annular slot antenna

In this paper, a compact circularly polarized co-designed filtering annular slot antenna (ASA) is proposed. The antenna comprises a distributed capacitor-loaded annular slot radiator to produce circular polarization (CP) radiation, which is seamlessly integrated with a microstripline bandpass filter (BPF) to enhance out-of-CP-band suppression. Two tightly coupled arc branches protruding into the annular slot are used to provide the required perturbation capacitance. The filter is designed by employing three concentric arc-shaped coupled microstripline resonators. The ground plane is shared by the annular slot radiator and the filter to reduce size occupation. It is found that the proposed antenna can not only yield high frequency selectivity, but also obtain widened CP bandwidth under the assistance of the filtering circuit. An antenna prototype has been fabricated and measured, showing that the antenna achieves a 10 dB return loss impedance bandwidth of around 13.7%, enclosing a 3 dB axial ratio (AR) bandwidth of more than 10.6%. Details of design considerations and experimental results are presented and discussed.

Design and Analysis of Dual-Mode Double-Square Loop Resonator for Bandpass Filter Applications

The paper presents a double-square loop (DSL) resonator for a dual-mode bandpass filter; the resonator has two sides of unequal length. We use the IE3D electromagnetic simulation software for evaluating the effects of the DSL-type bandpass filter and an FR4 substrate for comparing the differences between the simulated and the measured results. The center frequency of the filter is set to be around 2.4 GHz in both the simulation and the implementation. The simulated and the measured results reveal that the filter frequency and bandwidth are very similar in both cases and prove that the microstrip-line bandpass filter can be used as a passive component in a variety of applications in the field of communications.

Magnetic field tunable 18–36 GHz dielectric bandpass filter

Microstripline bandpass filters based on dielectric resonance in polycrystalline nickel ferrite have been designed and characterised for operation at discrete frequencies over 18–36 GHz. The filters have insertion loss of 2–5 dB and could be tuned by 0.5–1.3 GHz with a nominal magnetic field.

Rotationally symmetric microstrip-line millimetre-wave bandpass filter with two transmission zeros

A rotationally symmetric short-circuited stub-loaded structure is proposed. This structure is used to design a dual-mode microstrip-line bandpass filter. Moreover, two transmission zeros are generated near the lower and upper cutoff frequency edges of operating millimetre-wave bands. As design examples, the in-band and out-of-band performances of one filter prototype using single layer microstrip-lines have been designed and experimentally examined. The measured results show that the filter achieves a passband insertion loss of 0.97 dB at 40 GHz and lower- and upper-stopband rejection of larger than 24 dB.

Dual‐band microstrip‐line BPFs using tap‐coupling resonators

AbstractWe focused on various dual‐band microstrip‐line bandpass filters (BPFs) based on tap‐coupled resonators. Three types of BPFs, the basic type, multiple‐pole type, and wideband type, were proposed and designed by classical filter theory based on the narrowband approximation method. These filters were analyzed by original computation programs and commercial circuit and electromagnetic simulators. The proposed BPFs were then fabricated and measured in the laboratory. The results confirm that the proposed BPFs produce dual passband response, multiple attenuation poles, and wide‐passband characteristics. Very good agreement is found between the results of simulations and experiments. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(6): 25–33, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10212

A Modified Particle Swarm Optimizer and its Application to the Design of Microwave Filters

In this paper, a modified particle swarm optimization (PSO) algorithm is presented and its applicability is shown for the design of specific microwave filter as a case study of microwave components. In the proposed modified PSO algorithm, particles in the swarm are divided to form multiple sub-swarms. The social component of PSO’s velocity update equation is modified to include the effects of multiple sub-swarms. Five benchmark functions have been considered for testing the proposed algorithm. The approach has been tested for two basic modifications of PSO namely PSO with inertia weight (IW) and PSO with constriction factor method (CFM). The simulated results illustrate that the modified PSO algorithm has the potential to converge faster, thus reducing the computational expenses, while maintaining/improving the quality of solution. Finally, the proposed algorithm is used for the design of coupled microstrip line band pass filter which is a computationally expensive process when the design is conducted using evolutionary algorithms and electromagnetic (EM) simulation tools.

Ultra-wideband bandpass filters with improved out-of-band behaviour via embedded electromagnetic-bandgap multimode resonators

A class of ultra-wideband microstrip-line bandpass filters with improved out-of-band behaviours is presented by using an electromagnetic (EM) bandgap embedded multimode resonator. At first, the two EM bandgap structures are constructed by periodically loading uniform or non-uniform open-circuited stubs. Their performances are numerically characterised, aiming at exhibiting the existence of a bandstop in a frequency range of 15.0–30.0 GHz. These bandgap structures are then internally embedded in the middle part of an open-ended microstrip line resonator, constituting a modified type of multimode resonator. In the design, the dimensions of this resonator need to be properly adjusted towards allocating the first three resonant modes in the 3.1–10.6 GHz ultra-wide passband. To achieve a preferably wide upper stopband, the transmission zero of parallel-coupled lines is used to cancel the spurious fourth-order resonant mode. Also, higher-order modes in the upper band are inhibited by the employed bandgap structures. Two bandpass filters using the non-uniform stub-loaded resonator are finally designed, fabricated and tested. Predicted insertion/return losses and group delays are experimentally confirmed in a wide frequency range of 1.0–30.0 GHz.

60-GHz System-on-Packaging Transmitter for Radio-Over-Fiber Applications

Using ultra-high-speed electroabsorption modulator (EAM) devices for RF/optic conversion, we fabricated system-on-packaging (SOP) transmitter (Tx) modules and characterized their performance in 60-GHz RF/radio-over-fiber (ROF) applications. Both an EAM and low-noise amplifiers (LNAs) were co-packaged with internal bias circuits into a butterfly-type metal housing. At the EAM temperature,T~ 25degC and the EAM reverse bias, VR~1.6 V was the largest RF gain obtained that was very susceptible to the change of T . The impedance matching in the 60-GHz band was accomplished with both a microstrip-line bandpass filter and a 500- Omega shunt resistor, which defined the 2-GHz passband of the SOP transmitter. In 60-GHz two-tone experiments, we observed that the spurious free dynamic range of an SOP module with two LNAs was 78 dB middot Hz2/3 while that of the narrowband EAM module showed 82 dB middot Hz2/3. In contrast, the noise figure exhibited a large reduction of up to 30 dB for the SOP module compared with the narrowband EAM module. Using the SOP Tx module, we achieved successful transmission of commercial high-definition digital CATV signals in 64-quadrature amplitude modulation (QAM) format through the 60-GHz RF/ROF link. The total throughput of the link was estimated to be 6.5 Gb/s.

タップ結合型共振器を用いたマイクロストリップ線路デュアルバンドＢＰＦ

We focus on various dual-band microstrip-line bandpass filters(BPFs) based on tap-coupled resonators. In this study, three types of the BPFs such as basic type, multiple poles based type and wide-band type are proposed and designed by classical filter theory based on narrow-band approximation method. These filters are analyzed by original computation programs and commercial circuit and electromagnetic simulators. And then, the proposed BPFs are fabricated and measured in our laboratory. From the results, we have confirmed that the proposed BPFs produce dual pass-band response, multiple attenuation poles and wide-passband characteristics. We also have observed very good agreements between the simulations and experiments.

Out-of-Band Improvement by Microstrip Line BPFs with Multiple Attenuation Poles in Stopband Using Various Conditions of Coupling Length of Partially Coupled-Line Section

In a partially coupled-line bandpass filter (BPF), a combination of two microstrip line resonators which are partially coupled, are considered, where one resonator is half-wavelength (λ/2)-long, and another whose one end is grounded, is only quarter-wavelength (λ/4)-long. Therefore, the length of a coupled-line section can be varied based on the position of the grounding end, and five conditions of the movable coupling length have been simulated which will greatly influence the spurious responses of a BPF. This property is numerically investigated in this paper. The analysis shows that, based on the grounding position, this method is capable of realizing the improved out-of-band characteristics by locating the multiple attenuation poles in the stopband and improved spurious responses up to five times of the center frequency (5 f0). A few empirical models of BPF are fabricated, and the numerical results are ensured by comparing with the experimental results.

Electrically Tunable Superconducting Microstrip Line Band-Pass Filter for Mobile Applications

2 GHz band electrically tunable superconducting microstrip line band-pass filter was developed. The tunable filter used a thin interdigital electrode. The dielectric distribution of SrTiO 3 substrate included a calculated nonlinear effect of the electrode and ferroelectric material. As a result, the tunable microstrip line filter design with interdigital electrode enabled calculation by the finite element method and the moment method. The tunable filter with a measured unloaded Q factor of 9700 and a frequency shift of 1.25 MHz was obtained.

New coupled-line bandpass filter with stepped impedance hairpin (SIH) resonator

In this paper, a new coupled-line bandpass filter with a stepped impedance hairpin (SIH) resonator is proposed. The design formulas are derived based on coupled-line filter theory and the equivalent-circuit network. This filter not only achieves better selectivity, but also suppresses the 2nd-harmonic response, as compared with the three-stage parallel-coupled microstrip-line bandpass filter, which we use as the conventional case. The measured results show that the proposed coupled-line bandpass filter with an SIH resonator increases the lower- and upper-band selectivity by 13.8% and 41.9%, respectively. In addition, the level of the 2nd-harmonic response is improved 35 dB, and the fractional 3-dB bandwidth is reduced 10.5%. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 80–83, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20553

Progress of a tunable active bandpass filter

A review of a tunable active bandpass filter developed in our research group is given here. Presented first is the basic structure of an end-coupled microstrip-line bandpass filter. Next discussed is the concept of using coupled negative resistance to compensate the loss of tank circuit. Then, the method of using varactor diode or mesfet varactor to tune the center frequency of the passband is discussed. The capability of optical-control of mesfet varactor and the concept of using mesfets as three-terminal varactors are also discussed.

More accurate model of the coupled microstripline section

A parallel coupled microstripline bandpass filter was designed to operate at a frequency of 10 GHz with a 10% bandwidth. The theoretical transmission-loss response was predicted for a coupled microstripline section using a more accurate model. A discrepancy of about 2% remained between the predicted and the measured centre frequencies of the filter. This was partly attributed to the possible influence of nonadjacent resonators which were not included in the model. Further evidence of the presence of such a couplig phenomenon between nonadjacent resonators was demonstrated experimentally.