LC Equivalent Circuit Research Articles

Photo-excited separated tuning for the frequency and magnitude of dual-band absorption in the terahertz regime

Introducing tuning materials into metasurfaces is a crucial development trend for dynamic nanodevices. In this paper, we achieve the separate tuning for the frequency and magnitude of dual-band absorption in a photo-excited metasurface in the terahertz regime. By tuning the conductivity of the embedded photo-excited silicon, the two absorption peaks shift by 0.33 THz and switch to zero from near unity, respectively. In contrast, the absorption spectrum of x-polarized waves shows insensitivity to the variation of silicon conductivity. The LC equivalent circuit model is used to demonstrate the resonance frequencies of absorption peaks, which agree well with simulation results. This photo-excited Si based metasurface has wide potential applications in dynamic terahertz devices, such as modulators and frequency selectors.

Millimeter-Wave On-Chip Bandpass Filter Using Complementary-Broadside-Coupled Structure

A new millimeter-wave on-chip bandpass filter (BPF) using complementary-broadside-coupled (CBC) structure is presented. The transmission zeros (TZs) of the proposed BPF are calculated and analyzed through using an LC equivalent circuit. An overall guidance is given for tuning the locations of TZs through changing the physical parameters of the layout or the electrical parameters of the equivalent circuit. To prove the feasibility of the proposed BPF, a prototype with very compact size is designed and fabricated in a commercial 0.13-lm SiGe (Bi)-CMOS technology, whose center frequency and bandwidth are 67 GHz and 44.8%, respectively. Good agreement between simulated and measured results validates the proposed idea.

Millimeter-Wave Bandpass Filters Using On-Chip Dual-Mode Resonators in 0.13-μm SiGe BiCMOS Technology

A novel on-chip dual-mode resonator (OCDMR) is proposed for the design of millimeter-wave (mm-wave) bandpass filters (BPFs). The proposed OCDMR consists of a stub-loaded metallic line and two identical open-end lines, which are extended and bent in opposite directions for coupling to the input and output ports. The two resonant frequencies of OCDMR can be independently adjusted by changing geometric parameters. To clarify the working mechanism of OCDMR, an LC equivalent circuit is constructed to imitate the resonant characteristics of OCDMR, which is calculated and analyzed in detail. Then, using the proposed OCDMRs, three different on-chip mm-wave BPFs with multiple transmission zeros (TZs) are designed and fabricated using 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m SiGe BiCMOS technology. Good agreement between simulations and measurements validates the feasibility of OCDMR for applications in the on-chip mm-wave BPFs.

Optimal Design Proposal for Capacitance in Operating Area Expandable SR Motor Drive Circuit

A novel drive circuit for switched reluctance (SR) motor expanding the operating area under limited source voltage has been proposed by adding external capacitor in series to extend supply voltage. However, the capacitance of the external capacitor has not been optimized to be sufficient to extend the driving range of the SR motor. Subsequently, the authors have previously proposed a conservative design method for capacitance by linearizing the winding current. However, there is a problem in that the difference between the conservative design and the simulated fluctuation of the capacitor voltage is large. In this paper, an optimal design method is proposed for the capacitance by using an LC equivalent circuit at the beginning of excitation and demagnetization.

Millimeter-Wave Bandpass Filter Based on Spiral Resonators and DGS Using SiGe BiCMOS Technology

A new ultra-compact millimeter-wave on-chip bandpass filter (BPF) is presented based on two spiral resonators and a defected ground structure (DGS). For investigating the working mechanism of the proposed BPF, an LC equivalent circuit is constructed, and then the corresponding transmission zeros (TZs) are calculated in order to make the filter be quickly optimized with the guidance of LC equivalent circuit. Finally, the BPF is fabricated using 0.13-lm SiGe BiCMOS technology for demonstration. The measured results show that the fabricated BPF has a center frequency at 70.65 GHz with a bandwidth of 29.3%. The chip area of the BPF, excluding testing pads, is only 0.0288 mm2.

A miniaturized filter design approach using GMDH neural networks

AbstractA miniaturized microstrip low‐pass filter (LPF) has been designed and fabricated using semicircular‐shaped resonators. The designing procedures as well as the LC equivalent circuit of each step have been reported. Due to the small size of the presented filter, flat group delay in the pass‐band, low insertion loss (IL), and high return loss (RL) in operational frequency. By producing adjusted transmission zeros (TZs), the second to fourth unwanted harmonics were attenuated using the proposed LPF. The machine learning approach has been utilized to adjustment of the filter parameters. The 3 dB cut‐off frequency (Fc), TZs, IL, and RL were predicted using the group method of data handling neural network (GMDHNN). Ninety simulations were performed with different inductor and capacitor values. The collected data were used for neural network training. The GMDHNN can diagnose the efficient inputs, so this feature was applied to determine the efficient L and C elements on TZs, Fc, IL, and RL. Finally, the fabricated filter results are well‐matched with the simulation ones. IL and RL of the suggested filter in operational frequency are −0.09 and −17.26 dB, respectively. The total filter size is only 14.65 mm × 3.5 mm.

A TM polarization absorber based on a graphene-silver asymmetrical grating structure for near-infrared frequencies.

In this paper, a TM polarization multi-band absorber is achieved in a graphene-Ag asymmetrical grating structure. The proposed absorber can achieve perfect absorption at 1108 nm, 1254 nm, and 1712 nm (the absorption exceeds 98.4% at the three peaks). Results show that the perfect absorption effect originates from the excitation of magnetic polaritons (MPs) in the silver ridge grating; a LC equivalent circuit model is utilized to confirm the finite-difference-time-domain (FDTD) simulation. The influences of the incident angle, polarization angle, and geometrical size on the absorption spectrum are investigated. Moreover, a quadruple band absorber and a quintuple band absorber are also designed by introducing more silver grating ridges in one period. The proposed graphene-Ag asymmetrical structure has some advantages compared with other absorbers such as the ability to be independently tuned and a simple structure. Thus, the proposed structure can be applied in the areas of multiple absorption switches, near-infrared modulators, and sensors.

Dual-band filter design based on hourglass-shaped spoof surface plasmon polaritons and interdigital capacitor structure

In this paper, a dual passband filter with spoof surface plasmon polaritons (SSPPs) and interdigital capacitance structure loaded on a coplanar waveguide (CPW) is proposed. First, the hourglass-shaped SSPP unit-cell structure and the interdigital capacitor structure are introduced on the coplanar waveguide transmission line to obtain high fractional bandwidth and low insertion loss passband characteristics. Then, a dual passband filter is formed by loading the interdigital capacitor loop resonator to excite the trapped waves. The simulation results show that the proposed dual passband filter has excellent upper sideband rejection and dual passband filtering performance. The fractional bandwidths of the two passbands of the design are 46.8% (1.49–2.40 GHz) and 15.1% (2.98–3.63 GHz), respectively, which can achieve more than –40 dB rejection in a range of 4.77–7.48 GHz. The upper cutoff frequency and lower cutoff frequency of the two passbands can be independently regulated by changing the structural parameters of the proposed filter. In order to gain a more in-depth understanding of the operating principle of the dual passband filter, the corresponding dispersion curves and electric field distribution, LC equivalent circuit analysis are given. Finally, the prototype of the designed filter is fabricated according to the optimized parameter values. The experimental results are in good agreement with the simulation ones, indicating that the proposed dual-passband filter is of great importance in implementing microwave integrated circuits .

Narrow-band power dividers with wide range tunable power-dividing ratio

This paper presents two narrow-band power dividers with a wide range power-dividing ratio based on the two new controlling insertion loss methods, which are low-impedance line and coupling capacitor. Initially, a narrow-band BPF is designed based on the equivalent circuit model and LC equivalent circuit. Then, using the surface current density, it is determined by which part of BPF structure the insertion loss (IL) can be controlled at center frequency. The tunable Wilkinson power dividers (TWPDs) are designed based on IL control components to create a wide range of power-dividing ratios, using only two DC voltages. The center frequency of first designed TWPD is 2.5 GHz, and the power-dividing ratio can be controlled up to 1:45 by variation of two DC voltages from 0 to 8 V. Since the structure of TWPDs are symmetric, the inverse voltages results in the inverted divided power between the output ports. The center frequency of second designed TWPD is 2.52 GHz, and power-dividing ratio can be controlled up to 1:134 by variation of two DC voltages from 1.7 to 4 V. Two proposed TWPDs are fabricated and measured. Comparisons of the measured and simulated results are presented to verify the theoretical predictions.

Designing a Compact Microstrip Dual-Band Filter with Two T-Shaped Resonators and Suitable Frequency Selectivity

A miniaturized microstrip dual-band bandpass filter (DBPF) with two T-shaped resonators is proposed. The two T-shaped resonators lead to multiple transmission zeros in the stopband and higher filter selectivity. The filter is analyzed using LC and even/odd mode analyses to determine the transmission zeros. The LC equivalent circuit and transfer function are presented. The proposed filter is symmetrical, so the electrical length and impedance values are used for odd/even mode analysis. The designed DBPF is centered at 1.9/5.54[Formula: see text]GHz and is suitable for WLAN applications. The insertion loss of the filter is less than 0.5[Formula: see text]dB and its return loss is more than [Formula: see text][Formula: see text]dB in each band. Five transmission zeros are created with an attenuation greater than [Formula: see text][Formula: see text]dB. The total area of the proposed filter is [Formula: see text][Formula: see text]mm2. To validate the proper performance of the proposed filter, it is fabricated and measured.

Design and fabrication of a miniaturized Gysel power divider using improved T‐shaped resonator

AbstractA high‐performance Gysel power divider showcasing high suppression factor and low insertion loss at 540 MHz has been designed, investigated, and fabricated in this paper. The proposed Gysel power divider is made up of replacing six identical resonators with conventional transmission lines. The proposed resonators, which have been analyzed using LC equivalent circuit analysis, are designed to have a small size, low insertion loss, wide stopband, and narrow transition band. The final tested results have indicated that the suggested power divider is able to suppress nine harmonics; moreover, it has only an insertion loss of 0.4 dB. Another positive feature of the power divider is its small size in comparison with a conventional power divider at this operating frequency, where it occupies 34.5 × 63.8 mm2 equaling to 0.188 × 0.102 , where is the wavelength guide at 540 MHz. This figure is 25% of a conventional Gysel, considered as a remarkable point.

Predictable infrared dual-band narrow-band absorber for infrared detection

Dual-band infrared absorbers have received a great deal of attention for their potential applications in the field of sensing and detection. In this paper, we proposed a composite model consisting of Platinum nano-cylinder and micro-ring column stacked on top of Si3N4 and Platinum films. The effect of geometrical parameters on spectral absorption was explored by finite difference in time domain methods, and the results revealed that there were narrow perfect absorption peaks in each of the two atmospheric window bands due to the magnetic polaritons. Meanwhile, the quantitative relationship of resonance wavelength and geometrical parameters were predicted by LC equivalent circuits. In addition, graphene was added to the structure to dynamically adjust the resonance wavelength by varying the Fermi level. The combination of graphene and microstructure achieved full coverage detection of wavelengths in the atmospheric window range. This dual-band absorber has potential applications in infrared detection because of its good absorption properties and its tunability.

A quad‐band defected microstrip structure loaded bandpass filter for standard GPS , WiFi , WLAN , and WiMAX applications

A quad-band bandpass filter is proposed using a defected microstrip structure (DMS) for GPS, WiFi, WLAN, and WiMAX applications. This filter uses a stub-loaded stepped-impedance resonator (SL-SIR). The proposed filter is fabricated on an RT/Duroid5880 substrate (εr = 2.2, h = 0.787 mm, tanδ = 0.0009). Then, the LC equivalent circuit of the proposed filter is presented. A 28th-order transfer function is obtained and approximated by 8th-order transfer functions. The results of simulation, measurements and the LC equivalent circuit are in good agreement. The proposed filter operates at 1.6, 2.48, 3.76, and 5.44 GHz. The measured insertion losses are 0.32, 027, 0.51, and 0.41 dB in the four bands, while the return losses are better than 10 dB in all frequency bands. Finally, the proposed filter is compared with other bandpass filters.

Compact Millimeter-Wave On-Chip Dual-Band Bandpass Filter in 0.15-μm GaAs Technology

A compact on-chip dual-band bandpass filter (BPF) at millimeter-wave frequencies is proposed in 0.15- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> GaAs technology. To understand the working mechanism of the BPF, an LC equivalent circuit model is presented and analyzed for position estimation of the transmission zeros and poles. For demonstration, an on-chip BPF example is fabricated and tested, whose simulation and measurement are in good agreement. There are two frequency bands at 60.2 and 79.7 GHz with bandwidths of 9% and 6.8%, respectively. The chip, excluding the feedings, is only 0.304 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times0.464$ </tex-math></inline-formula> mm.

Trapezoid-shaped resonators to design compact branch line coupler with harmonic suppression

This article proposes a new branch-line coupler design using two trapezoid-shaped resonators, applied in side and center. The standard 35 and 50 Ohms λ/4 transmission lines (TLs) are attained through the variations of the resonator’s TLs width. Since there are not explicit formulas for the suggested trapezoidal shape resonator, the design procedure will include the derivation of new formulas to configure the LC equivalent circuit. The proposed branch-line coupler, operating at 0.95 GHz, has achieved 79% of size reduction if compared to the conventional designs. Furthermore, the suggested design has successfully diminished the first six harmonics with a suppression level of (41, 29, 29, 28, 20, and 20) dB, respectively. The bandwidth is from 800 MHz to 1 GHz and The fractional bandwidth is 22.2%.

A miniaturizing method for designing a Gysel power divider

ABSTRACT In the present study, a new miniaturizing method has been applied to design a very compact Gysel power divider with nth harmonics elimination. The designed power divider has perfect harmonics suppression with excellent isolation, high return loss, and low insertion loss. Moreover, a lowpass filter has high proficiency. It has been located in place of the original transmission lines a λ/4. The observed outcomes of the lowpass filter show that the use of this filter suppressed the extra harmonics and has decreased the size of the circuit power divider. Moreover, LC equivalent circuits of all steps are illustrated. The circuit of the power divider can be studied via the odd and even mode method. This proposed Gysel power divider worked at the center frequency of 1 GHz. The proposed Gysel power divider is manufactured and measured for verification. The measured outcomes display excellent settlement by the simulated results. The maximum insertion loss, |S11|, |S22|, and |S23|, are 3.11, 24.6, 17, and 14.5 dB, respectively.

Terahertz bandstop-to-bandpass converter based on VO2 hybrid metasurface

We experimentally demonstrated a terahertz (THz) bandstop-to-bandpass converter based on vanadium dioxide (VO2) hybrid metasurface. The unit cell consists of gold and VO2 hybrid structures standing on a high resistance silicon substrate. Simulation and experimental results show that for y-polarized waves, the device’s function converts from bandstop filtering to bandpass filtering when VO2 transits from insulating state to metallic state induced by the Joule heat produced by the heating wire on the surface. The operation principle is explained by combining the surface current distribution and the LC equivalent circuit model. For x-polarized waves, when VO2 changes from insulating state to metallic state, the response of the device to THz wave changes from single resonant state to double resonant state. This phenomenon originates from the conductance coupling effect in plasma optics. The proposed device realizes active control of THz waves and is expected to be used in the fields of THz communication, imaging and electromagnetic switching.

60-GHz Compact Dual-Mode On-Chip Bandpass Filter Using GaAs Technology

A 60-GHz compact dual-mode on-chip bandpass filter (BPF) is presented using gallium arsenide (GaAs) technology. To demonstrate the working mechanism of the proposed BPF, an LC equivalent circuit model is conceived and analyzed for further investigation of the transmission poles and zeros. Finally, a prototype of the BPF is fabricated and tested to validate the proposed idea, whose simulated and measured results are in good agreement. The measurements show that it has a center frequency of 58.7 GHz with a bandwidth of 18.4%, and the minimum insertion loss within the passband is 2.42 dB. The chip size, excluding the feedings, is about 0.158 mm ×0.344 mm.

Tunable dual-band metamaterial absorber at deep-subwavelength scale

A tunable dual-band metamaterial absorber composed of a gold square ring and a metal film separated by a strontium titanate dielectric is investigated. Two resonance peaks at frequencies 0.162 THz and 0.329 THz with over 99% absorbance are realized at room temperature. The maximum ratio between the lattice constant and the resonance wavelength is approximately 8.2%, which is much smaller than that of the formerly reported absorber. When the temperature changes from 150 K to 350 K, the two resonance absorption peaks at approximately 66.2% and 67.8% of the modulation depths are obtained. The effective impedance method and the LC equivalent circuit modelling are used to analyze the absorption mechanism of the proposed absorber. The proposed absorber is not affected by the change in polarization angles at normal incidence. The proposed structure adopts a single patterned square ring, which can be manufactured easily, and extended to other frequencies in applications such as biosensors, monitoring and imaging.

Miniaturized bandpass filter using coupled lines for wireless applications

Abstract In this paper, a bandpass filter (BPF) has been designed using bent and coupled-line structure. The design process of the filter to achieve a BPF with good characteristics is completely explained. Therefore the LC equivalent circuit of The BPF is presented as the analytical description. The proposed filter can pass frequencies between 2.2 and 3.6 GHz with an insertion loss &lt;0.4 dB, which is suitable for wireless applications. The fractional bandwidths (FBW) of the filter is about 48%. Some characteristics such as small size, low insertion loss, high return loss wide upper stopband bandwidth, and good suppression level in stopband are among the advantages of this study to be mentioned. Finally, the presented filter was fabricated, and the measured results have a proper agreement with the simulation results.