Stub Structure Research Articles

DESIGN OF DUAL BAND PATCH ANTENNA AT KU-BAND FOR WIRELESS APPLICATIONS

In this paper, U-shaped patch antenna with triangular stub antenna is proposed for satellite and radar applications. The U-shaped with triangular stub structure is considered on the patch antenna with symmetric feed is presented on the substrate. The antenna design is impressed on FR4_Epoxy substrate material whose dielectric constant is 4.4. The adopted antenna resonates dual band frequencies at 14.1049GHz and 15.1610GHz which are used for satellite communications and 16.9363GHz and 17.7903 GHz which are used for radar communications. The parameters of antenna like gain, reflection coefficient, radiation pattern and bandwidth are analyzed and presented in the results. The adopted design achieves gain of 5.18dB and reflection coefficient of -28.75dB at 14.1049GHz, gain of 3.79dB and reflection coefficient of -16.31dB at 15.1610GHz, gain of 3.40dB and reflection coefficient of -16.45dB at 16.9363GHz and gain of 4.17dB and reflection coefficient of -15.93dB at 17.7903GHz.

Coupled‐line band‐pass filter with T‐shaped structure for high frequency selectivity and stopband rejection

A coupled-line band-pass filter (BPF) with T-shaped stub structure is presented. Five transmission poles within the passband and eight deep transmission zeros (TZs) from 0 to 2f0 (f0 denotes filter's center frequency) are realized through input impedance calculations. With the simple T-shaped structure, the positions of six TZs can be appropriately adjusted to achieve high frequency selectivity and stopband rejection. For demonstration, a BPF prototype centered at 2.05 GHz is designed and fabricated, whose measured rejection levels are of over 45.5 dB at lower stopband and better than 19.5 dB at upper stopband. The simulation and measurement results are in good agreement, which validates the design idea.

A Multipurpose and Highly-Compact Plasmonic Filter Based on Metal-Insulator-Metal Waveguides

A multipurpose and ultra-compact nanoplasmonic wavelength filter based on stub structure in a metal-insulator-metal (MIM) waveguide is suggested and numerically investigated. A novel approach of connecting two stepped-like apertures to both input and output ports is applied to form Fabry-Perot (FP) cavities, which enabled the structure to act as a dual band-pass filter at wavelengths 1310 nm and 1550 nm. It is shown that the variation in cavities’ length allows to realize a long-wavelength cutoff filter, and cutoff wavelength can be easily tuned by adjusting the length of the cavities. Furthermore, it is revealed that increasing the gap between the stepped-like apertures and the cavities provides a triple band-pass at telecom wavelengths, e.g., 1267.5 nm, 1414.19 nm, and 1644.7 nm. The tunable broadband high-pass wavelength filter is then achieved while the lengths of stepped-like apertures and stub resonators are set to be identical. Finally, a tunable nearly perfect absorber can be obtained by varying the width of stub resonators. Therefore, because of functionality, size, as well as efficiency the proposed plasmonic filter may greatly contribute to miniaturization of next generation of photonic integrated circuits (PICs), and find applications in on-chip integration and wavelength-division multiplexing (WDM) in optical communication systems.

An Investigation of Finite Width Slotline Open Circuits Comprised of Multiarm Short-Circuit Stubs

Multiarm slotline stubs have been used to increase the bandwidth of slotline open circuits in transitions between microstrip and slotline and between coplanar waveguide and slotline. The model used in prior papers is a series connection of the short-circuit terminated stubs, resulting in an increase in the input impedance by a factor of $N$ , where $N$ is the number of stubs. In this paper, it is shown that this model cannot be applied for slotline with finite width metal planes or coplanar stripline (CPS), because it does not account for higher order modes that are necessarily excited on the multiarm structure. This paper presents a physical explanation and model that accounts for the higher order modes on the structure and explains how the multiarm finite width slotline/CPS stub structure increases the bandwidth of the transitions between slotline and other transmission lines. With the correct model presented in this paper, it is expected that improved slotline or CPS circuits can be developed.

Microwave Bandpass Filter Integrated with Notch Response for Wide-band Applications

This paper presents the design of wide-band bandpass filter using microstrip structure at 3-6GHz with fractional bandwidth of 66.67% based upon short-circuited stubs structure of 5th degree. In order to avoid the interference from existing system that operates in the frequency band, the folded stepped impedance resonator (SIR) was introduced to generate a narrow notch band at 5.2GHz. Pin diode is employ as switching mechanism for the notch response. This design is simulated by Advance Design System (ADS) software and using Roger Duroid 4350B with a dielectric constant of 3.48, substrate thickness 0.508mm and loss tangent 0.0019.The achieved return loss is better than 15dB and insertion loss is less than 1dB.The designed filter can be used in microwave communication systems such as wireless communication devices and military applications (radar system).

Design and Simulation of Microstrip Hairpin Bandpass Filter with Open Stub and Defected Ground Structure (DGS) at X-Band Frequency

In this paper we have designed and simulated a Band Pass Filter (BPF) at X-band frequency. This filter is designed for X-band weather radar application with 9500 MHz center frequency and bandwidth -3 dB is 120 MHz. The filter design was performed using a hairpin microstrip combined with an open stub and defected ground structure (DGS). The substrate used is Rogers RT5880 with a dielectric constant of 2.2 and a thickness of 1.575 mm. Based on the simulation results, it is found that the filter works on frequency 9,44 - 9,56 GHz with insertion loss value at pass band is -1,57 dB.

Design of a moderate-wideband superconducting filter with modified stub structure

This paper presents a design method for moderate-wideband filters with modified λ/2 stub resonators mid-tapped by λ/4 connecting lines which act as admittance inverters. The modified tapped-stubs avoid low characteristic impedances of the stubs which results in a very wide strip-width and a large circuit size. An example filter at 2250 MHz with a fractional bandwidth (FBW) of 45% is successfully designed with this method and fabricated. It has a compact size of 26.5 mm × 10.5 mm on a YBCO/LaAlO3 superconducting wafer. The measurements show good response and match well with the simulations.

Miniaturised Wilkinson power divider with wide‐stopband using synthetic transmission line

A wide-stopband Wilkinson power divider (WPD) is proposed, which can be realised by using open dual-transmission line (TL) stub and L-type artificial lowpass TL structures. To further achieve miniaturisation, synthetic TLs are also employed. The simulated and measured results are consistent, and the measured |S 21| and |S 31| (insertion losses) have shown stop-bandwidth of larger than 18.33 GHz (1.67–20 GHz) and 18.28 GHz (1.72–20 GHz), respectively, under the condition of 30 dB harmonic suppression level. The wide-stopband of the WPD can cover 2fo –22.2fo (fo = 0.9 GHz), and the occupied area of the WPD (not include the feeding network) is only 0.11λ g × 0.06λ g (λ g: guided wavelength at fo ).

Multi notch-band CPW-fed circular-disk UWB antenna using underground filter

ABSTRACTThis article presents empirical results of multi notch-band coplanar waveguide (CPW) fed circular-disk monopole antennas for ultra-wideband (UWB) applications where the notch-bands are embodied into the antenna using undergrounded filter implemented on U-shape or L-shape stub structures etched on the antenna’s backside. With these stub, the notch characteristics are controllable and so with L-shape, here narrowband antenna designed for 2–6 GHz. The antennas’ performance was validated practically. Both antennas have VSWR < 2. The antenna with undergrounded filter implemented on U-shape stub structure exhibits notch-bands across 2.8–9 GHz necessary to reject interference from WiMAX signals. The antenna with just the L-shape stub structure results in multiple notch-bands necessary to reject 3G, 4G and WiMAX systems. Both antennas radiate omni-directionally in the E-plane and bi-directionally in the H-plane, and have a gain that varies between 0.9–6.7 dBi between 2–11 GHz, with an average gain of 4.2 dBi. The both antennas are fabricated on low cost substrate (FR-4) and simulation results are compared with experimental and the experimental confirmed the simulation.

A compact planar UWB MIMO antenna using modified ground stub structure

A compact planar UWB MIMO antenna using modified ground stub structure

Dispersive delay lines using microstrip technology

A dispersive delay line is a structure that causes signals of different frequencies to suffer different time delays. It is found that excessive group delay occurs in an induced pass-band of filter using asymmetric, parallel stubs in transmission lines. The maximum group delay of the dispersive delay line is determined by characteristic impedances, physical lengths of parallel stubs and the bandwidth of the induced pass-band. The induced, band-limited pass-band is transformed into an all-pass band by introducing non-coplanar slot-lines, while the negative group delay time of original, asymmetric, parallel stubs structure at transmission zeros are compensated to further increase the group-delay-time bandwidth. The theoretical results are validated by experiment using compact microstrip lines.

Miniaturization of Microwave Bandpass Filter for Wideband Applications

This paper presents the miniaturize structure of the wideband bandpass filter using quarter-wavelength short circuited stub structure of the 7th order. The filter design was validated using Roger Duroid RO4350 with a dielectric constant of 3.48, tan δ of 0.019 and thickness of 0.508 mm. The conventional bandpass filter is then reorganized using curve bending to miniaturize the overall size while maintaining the performance of the bandpass response. The proposed structure with 65.3% (3.03 to 5.97 GHz) fractional bandwidth is designed, fabricated, and measured. Both simulations and measured results are found to be in good agreement. The measured passband reflection and transmission coefficient is better than 16 dB and 0.5 dB respectively. This type of wideband bandpass filter is very useful to many microwave wideband communication applications, mostly in civilian and military radar applications.

Optical filter effect of the metal–dielectric–metal waveguide with stub structure

Abstract The optical filter effect of the metal–dielectric–metal (MDM) waveguide with stub structure is investigated with surface plasmons (SPs) interference theory and simulated using finite difference time domain (FDTD) method. The transmission process of the surface plasmons propagating through the stub structure is discussed in detail, and testified by different time step field intensity images of FDTD simulation. It is verified by the FDTD simulation that the oscillation periods of the transmission curves are proportional to the wavelengths, and the number of the wavelength of the standing wave in the stub is linear to the stub length d. When the monochromatic continuous waves are incident, the transmissions are also periodically changed with the length of the stub. The shorter wavelengths present better filter sensitivity than longer wavelengths. The above optical filter effect implies that the MDM waveguide with stub structure can be applied in the fields of photonic integration devices and sensors.

Enhancement of thermospin effect in germanene based normal/ferromagnetic stub/normal junction

Spin thermoelectric effects in ferromagnetic (FM) germanene are theoretically investigated by using the nonequilibrium Green's function method. It is found that the spin Seebeck effect can be generated by temperature bias ΔT when a FM germanene is considered in the central region. However, the obtained spin resolved Seebeck coefficients is quite low with maximum value of Sσ≃700μV/K. The spin Seebeck effect is shown to increase enormously in different energy states with the assistance of electric field or stub structure. By modulating the geometric parameters of stub, the spin thermopower Ss has distinct peak values in the bulk states. Moreover, varying the Fermi energy within the bulk gap by the gate, Ss can be significantly enhanced by increasing the strength of electric field. The spin thermopower obtained by each method is predicted to be 2500μV/K, which is more than 300% larger relative to the case without electric field or stub. In addition, the magnitude and sign of spin thermopower can be manipulated by adjusting the Fermi energy. The results show that such FM germanene stub device exhibits much better thermoelectric performance and may be used as a wide energy range tunable spin thermoelectric generator.

Analysis and design of miniaturized multisection crossover with open stubs

ABSTRACTA compact branch‐line crossover using open stubs structure is proposed. Even and odd mode analysis is adopted to derive the analytical formulas for a crossover with wide bandwidth and a compact size. The proposed crossover operating at 2.5 GHz has a fractional bandwidth of 23% (from 2.2 to 2.78 GHz) with high isolation, a high return loss, and low insertion loss. It also has a low group delay deviation of about 0.38 ns. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2673–2677, 2015

π-Network Transmission Line Model for Plasmonic Waveguides with Cavity Structures

We propose a π-network transmission line model to investigate plasmonic metal-dielectric-metal (MDM) waveguides side-coupled with cavity structures. This model can effectively describe the transmission characteristics as a function of coupling distance in our proposed structures. And the π-network transmission line model is promoted to describe transmission spectra and scattering parameters in infinite element structures and periodic structures, which are confirmed by the finite-difference time-domain (FDTD) simulation results. In addition, the slow-light effects in waveguide side-coupled with periodic cavity structures are researched in our paper. And we first compare the slow-light effects in the plasmonic waveguide side-coupled with cavity structures and stub structures. These observations could be helpful to fundamental research and applications for integrated plasmonic devices.

Enlargement of the locally resonant Lamb wave band gap of the phononic crystal plate at the deep sub-wavelength scale

In this paper, the numerical investigation of Lamb wave propagation in two-dimensional phononic crystals composed by depositing the heavy cylinder stubs squarely onto both sides of a composite thin plate is presented. A significant enlargement of the relative bandwidth by two orders of magnitude compared with two-dimensional binary locally resonant phononic crystal plates and one order of magnitude compared with both the ternary composite plate and the simple plate with stub structures at deep sub-wavelength scale is obtained and discussed. Based on an efficient finite element method, we show that this band gap enlargement is due to the coupling between the plate mode and ‘double mass-spring’ mode, which leads to the enhancement of the locally resonance mechanism. The calculated elastic wave displacement fields illustrate the physics mechanism of opening the low frequency band gap and the existing of the flat bands. We also found that both the band gap and the flat bands depend on the geometry parameters of the heavy stubs and composite plate significantly.

A novel design of dual-band Wilkinson power divider with simple structure and wide band-ratios characteristics

The design and analysis of a dual-band equal-split Wilkinson power divider are presented in this paper. It is proved that a coupled line with a pair of stubs structure is capable of the dual-band operation in the Wilkinson power divider. Moreover, the overall structure of power divider can be simplified with small number of transmission line sections using the proposed method, and the proposed divider can achieve dual-band operation over a wide range of band-ratios. For verification, a microwave power divider operating at 1 and 2.5 GHz is fabricated, and the experimental results show that the designed power divider fulfills all the features of a conventional Wilkinson power divider, such as an equal power split and impedance matching at ports.

Wideband slow light achievement in MIM plasmonic waveguide by controlling Fano resonance

In this paper, we have investigated the characteristics of an asymmetric shaped Fano line in a metal–insulator–metal (MIM) plasmonic waveguide side coupled to two resonating stub structures. The spectral properties of Fano resonance are quite distinct due to the destructive interference between a two propagating plasmon modes. Two structural parameters are carefully adjusted: physical separation between both the resonating stubs and length of resonating stubs. By tailoring the separation between both the resonating structures, coupling between both the plasmon modes is controlled, and hence asymmetric nature of Fano line can be shaped accordingly. Resonance condition of Fano line can be tuned by scaling the length of stubs. A strong red shift in resonating wavelength with varying degree of asymmetry is observed, when length of resonating structures is increased. The sharp resonant peak, due to an asymmetric shaped Fano resonance is generally accompanied by large dispersion that results in reduction of group velocity of light near Fano resonance. By controlling the coupling between resonating stub, or by scaling the length of lower resonating stub, large value of group index (ng=75) and delay bandwidth product (DBP=0.2533) is obtained. The structure can be modified to suit different applications in optical buffers, optical switches and nonlinear optics devices.

Compact Planar Monopole Antenna with Dual Band Notched Characteristics Using T-Shaped Stub and Rectangular Mushroom Type Electromagnetic Band Gap Structure for UWB and Bluetooth Applications

In this paper, an ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed. The proposed antenna also covers ISM (Industrial, Scientific, and Medical)/Bluetooth band. The antenna consists of a microstrip fed truncated U-shaped patch, T-shaped stub, rectangular mushroom type electromagnetic band gap structures (EBG), and partial ground plane. To mitigate the problem of interference due to standard narrow bands (like wireless interoperability microwave access (WiMAX) and wireless local area network (WLAN)) lie in the range of UWB, dual band notched characteristics is introduced. The WiMAX and WLAN band notched characteristics are realized by introducing a T-shaped stub and rectangular mushroom type EBG structures, respectively. The proposed antenna is printed on a 1.6 mm thick FR4 substrate with relative permittivity $$(\upvarepsilon _{\mathrm{r}})$$ ( ? r ) 4.4 and the size of actual antenna is $$36 \times 40\hbox { mm}^{2}$$ 36 × 40 mm 2 . The measured results shows that the proposed antenna attains a wide impedance bandwidth $$(\hbox {VSWR} \le 2)$$ ( VSWR ≤ 2 ) from 2.35 to 11.6 GHz with dual band notched characteristics from 3.29 to 3.9 GHz and 5.1 to 5.85 GHz with stable radiation patterns. The time domain behaviors of the proposed antenna is also analyzed for pulse handling capability.