Short-ended Stubs Research Articles

Design and Implementation of C-Band Large-Power Planar Butler Matrix in SRS.

In satellite remote sensing (SRS), there is a demand for large-power microwave components. A Butler matrix is essential to a transmitting antenna array in SRS. This article illustrates the electrical and mechanical design, simulation, and test results of a large-power planar beamforming network for SRS at C-band. It is a 4 × 4 Butler matrix based on square coaxial lines. Short-ended stubs are used in the Butler matrix to broaden its bandwidth by 10%, support inner conductors, and enhance heat transfer in vacuum environments. The simulation results are consistent with the measured results. The reflection coefficient is less than -18 dB, and the isolation is more than 23 dB from 3.8 GHz to 4.2 GHz. The insertion losses are less than 0.6 dB, and the phase errors are better than ±6°. The measured peak microwave power of the proposed Butler matrix is 9 kW. Its size is 440 × 400 × 40 mm3. The proposed Butler matrix beamforming network can be applied to SRS systems.

A Shorted Stub Loaded UWB Flexible Antenna for Small IoT Devices.

In this manuscript, a compact in size yet geometrically simple Ultra-Wideband (UWB) antenna is demonstrated. The flexible-by-nature substrate ROGERS 5880, having a thickness of 0.254 mm, is utilized to design the proposed work. The antenna configuration is an excerpt of a traditional rectangular monopole antenna resonating at 5 GHz. Initially, a pair of triangular slots are employed to extend the impedance bandwidth of the antenna. In addition, a semi-circular-shaped, short-ended stub is connected at the upper edges of the patch to further increase the operational bandwidth. After optimization, the proposed antenna offers UWB ranging from 2.73-9.68 GHz, covering almost the entire spectrum allocated globally for UWB applications. Further, the antenna offers a compact size of 15 × 20 mm2 that can easily be integrated into small, flexible electronics. The flexibility analysis is done by bending the antenna on both the x and y axes. The antenna offers performance stability in terms of return loss, radiation pattern, and gain for both conformal and non-conformal conditions. Furthermore, the strong comparison between simulated and measured results for both rigid and bent cases of the antenna, along with the performance comparison with the state-of-the-art, makes it a potential candidate for present and future compact-sized flexible devices.

Ultra-Wideband 3-D Microwave Absorbers With Composite Slotlines and Microstrip Lines: Synthetic Design and Implementation

This article proposes a class of ultra-wideband 3-D microwave absorbers with composite slotlines and microstrip lines from synthetic design to practical implementation. Firstly, the general equivalent transmission line (TL) model of the proposed 3-D absorber element is formed based on two sets of shunt short-ended stubs and an i-section nonuniform connecting line. Then, the synthetic procedure is theoretically investigated using the equivalent TL model, aiming to construct an ultra-wide absorption band with the Chebyshev equal-ripple response. According to the prescribed absorptive performance, such as maximum reflection coefficient (C) and fractional bandwidth (FBW), the relevant parameters of the TL model can be directly calculated by the established synthesis approach. To validate the proposed concept, two prototypes, namely, absorber-I (i=1) and absorber-II (i=2), are designed, fabricated, and measured. Each prototype element applies a simple 3-D structure composed of slotlines, microstrip lines, and only one absorptive load, which are all etched on a single-layered substrate. Measured results agree well with synthetizations and simulations. For absorber-I, the measured bandwidth of 95.5% in a frequency range from 5.08 to 14.44GHz is successfully realized. Absorber-II obtains a measured FBW of 111.1% in a range from 4.48 to 15.68GHz. Average absorption ratios within the operating band are higher than 95.5% and 93.8% for absorber-I and absorber-II, respectively. Besides, the proposed 3-D absorbers are angularly stable within 600 oblique incidence. Therefore, such ultra-wideband 3-D microwave absorbers with simple structures possess the attractive potential for effectively absorbing electromagnetic waves.

Design of a Filtering Power Divider with Simple Symmetric Structure Using Stubs

A power divider (PD) with a wide stopband and simple symmetric structure using open- and short-ended stubs is analyzed and implemented in this paper. In the proposed power divider, for the first time, the output resistor is divided into two sections and open- and short-ended stubs are used between the resistors. The incorporated open- and short-ended stubs have resulted in a controllable bandwidth for the proposed PD, which resulted in 40% of the fractional bandwidth considering 3 dB attenuation of insertion loss. The proposed PD operates at 2 GHz, which shows more than 20 dB attenuation for the return and isolation losses. In addition, the obtained insertion loss at the operating frequency is approximately 0.3 dB, which shows a minor loss, and also, high isolation is achieved in the device. Moreover, 20 dB and 30 dB attenuation levels have been achieved for second and third harmonics. The results show high performance for the proposed power divider.

Ultra wideband bandpass filters with specified relative bandwidth

Abstract Algorithm for the realization of the broad range of values of wide relative bandwidth (RBW) bandpass filter is introduced. Algorithm is based on periodic ideal cells each with short-ended stub. Theory is developed for a symmetrical cell with proportional transmission lines, nonuniform or uniform, in term of characteristic impedance. The theory is applied for the uniform transmission lines. Simple equation of the ratio between characteristic impendence of the short-ended stub and the characteristic impendences of the main lines is given for the broad range of RBW. Realizable filters are for the very wide RBW up to over 1.5 (150%). Technology is chosen in microstrip with vias for the short ends. It is without coupling, without defected ground structure (DGS) and only with a single layer. The procedure is tested on the fabricated filters for very wide RBW of 1.5 (150%). Agreement between measurements and simulations is excellent.

Design of a full V‐band fundamental mixer with an ultra‐wide IF from 0.01 to 22 GHz

Design of a low cost Schottky diode based single-balanced mixer (SBM) in full V-band with an ultra-wide intermediate frequency (IF) bandwidth is presented here. By loading multiple quarter-wavelength short-ended stubs at both radio frequency (RF) and local oscillator (LO) frequency on the multistage stepped impedance matching networks, a broadband grounding circuit is provided for IF signal and thus output power nulls are eliminated over an ultra-wide IF band. The hybrid network is constructed by a 3 dB branch coupler and a 90-degree delay line, which enables the required balanced outputs with equal amplitude and 180-degree phase difference. A prototype of the SBM is designed, fabricated and tested. Measured results demonstrate that, for RF and LO frequency over entire V-band, the mixer has a conversion loss from 6.8 to 11.4 dB with an ultra-wide IF range of 0.01–22 GHz.

A planner Doherty power amplifier with harmonic suppression with open and short ended stubs

Abstract This paper presents a new Doherty power amplifier (DPA) with harmonics suppression. A Wilkinson power divider (WPD) with open-ended and short-ended stubs is designed to suppress unwanted signals. To design the power divider in the circuit of the DPA, even and odd mode analyses are utilized. The proposed design operates at range of 1.2–1.6 GHz. The linearity of the suggested DPA is increased about 6 dBm, in comparison with the main amplifier. The designed Doherty amplifier has a power added efficiency (PAE), drain efficiency (DE) and Gain about 60, 61% and 19 dB, respectively. The designed WPD suppresses 2nd up to 14th harmonics with more than 20 dB suppression level, which is useful for suppressing unwanted harmonics in DPA design. ATF-34143 transistors (pHEMT technology) are used for this DPA amplifier design. The main amplifier has class-F topology and class-F inverse topology is used for auxiliary amplifier.

A Generalized Synthesis Technique for High-Order and Wideband 3-D Frequency-Selective Structures With Chebyshev Functions

A generalized synthesis technique for a new class of high-order and wideband 3-D frequency-selective structures (FSSs) is presented in this article. First, a general circuit model with shunt short-ended stubs and an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$i$ </tex-math></inline-formula> -section nonuniform transmission line is discussed, whose frequency response can be synthesized with Chebyshev functions over a wide frequency range. Following the synthesis procedure, all the circuit parameters can be derived from the specifications of the filtering response, such as filtering order <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> (≥4), fractional bandwidth (FBW), and equal-ripple return loss (RL). Then, the general circuit model is applied to design high-order and wideband 3-D bandpass FSS, which is physically realized by using stacked printed circuit board pieces etched with slotlines and microstrip lines. As an example, a fourth-order 3-D FSS with FBW = 80% and equal-ripple RL = 10 dB is designed to show the establishment of good relationship between the circuit model and the physical model. To further improve the frequency selectivity, another two coupling paths independent of the main transmission path are created by simultaneously adjusting the FSS thickness and the separation of slotline sections, thus introducing two transmission zeros at both skirts of the passband. Both design examples are fabricated and measured. Good agreement between measured results and simulated ones indicates that the proposed synthesis method can provide an efficient and accurate solution to design such a class of wideband and high-order 3-D FSSs.

Design of Phase Shifters with Ladder Stubs Via Real Frequency Technique

Generally at high frequencies, lumped-elements are not preferred because of their limited range of values. Therefore, in this work, a kind of phase shifter formed with ladder stubs is studied and a new approach to design phase shifter’s low pass and high pass sections which are composed of series or shunt connected open-ended or short-ended stubs is proposed. In the approach, since the main focus is to form low pass and high pass two-port sections, switching process is not considered. First, the designer selects the section type and the total number of stubs in the sections; it is not necessary to fix the two-port section topologies and not necessary to derive the characteristic impedance and delay expressions for the stubs. In the example, 5-stub two-port sections of a [Formula: see text] phase shifter are designed by means of the proposed approach.

Mixed Element Networks with Series Capacitors Separated by Unit Elements

In this work, high-pass mixed-element networks with series capacitors separated by unit elements are analyzed. First, the description of the networks via two frequency variables is given. Then, explicit coefficient relations for the descriptive polynomials are derived in terms of the single-variable boundary polynomial coefficients. Finally, the derived relations are used to design a high-pass mixed-element matching network. The series capacitors can be converted to short-ended stubs by means of Richard’s transformation. Thus, the obtained network is suitable for microstrip production.

Design of a Suspended Stripline Dual-Band Band-Stop Filter Loaded With Short-Ended Waveguide Stubs Embedded in the Metal Housing

This letter presents a novel dual-band band-stop filter (DBBSF) based on suspended stripline (SSL) with short-ended waveguide stubs on its metal housing. A short-ended waveguide stub embedded transversally in the metal housing of the SSL has been shown to introduce independent transmission zeros. It is mostly suitable for high harmonic depression. This letter describes a band-stop filter with four short-ended waveguide stubs around a center frequency of 12.5 GHz. A U-shaped slot in the SSL forms a resonator and provides an additional independent stopband. We designed and fabricated a DBBSF with short-ended stubs formed on the metal housing and U-shaped slots in the stripline. Our design produced stop bands at 6.6 and 12.5 GHz, corresponding to attenuation levels of 27 and 26 dB, respectively. The short-ended waveguide stubs on the metal housing do not require additional space. Excellent agreement was achieved between the measured and simulated results.

Wideband filtering balun power dividers using modified Schiffman phase shifter

Two novel wideband bandpass filtering balun power dividers using modified Schiffman phase shifter are proposed in this article. Two types of wideband Wilkinson power dividers are adopted, respectively, in the two structures for wide passband. The Schiffman phase shifters are used in the structures for realizing 180° phase shift between output ports modified by connecting each of them with a short-ended stub for weak coupling coefficient. In addition, two transmission zeros are realized by an open-ended stub connected in parallel at the input port to realize the filtering characteristic. To verify the proposed structures, two wideband bandpass filtering balun power dividers (εr = 3.66，h = 0.762 mm, tanδ = 0.004) centering at 2GHz are designed and fabricated. The simulated and measured results are discussed.

Demonstration of Reconfigurable BPFs with Wide Tuning Bandwidth Range Using 3λ/4 Open- and λ/2 Short- Ended Stubs

In this paper, two implementations of reconfigurable bandwidth bandpass filters (BPFs) are demonstrated both operating at a fixed center frequency of 2.4 GHz. The proposed reconfigurable bandwidth filters are based on a square ring resonator loaded with λg/4 open-ended stubs that are permanently connected to the ring and converted to either 3λg/4 open-ended stubs or λg/2 short-ended stubs by means of positive-intrinsic-negative(PIN) diodes to implement two reconfigurable bandwidth states for each case. Due to the symmetrical nature of the design, even- and odd-mode analysis is used to derive the closed-form to describe the reconfigurable filters’ behavior. The switching between narrowband and wideband is achieved using PIN diodes. In the first implementation (λg/4 open-ended stubs to 3λg/4 open-ended stubs), a reconfigurable bandwidth bandpass filter is proposed where additional out-of-band transmission zeros are generated by integrating a λg/2 open-ended stub at the input port. In the second implementation (λg/4 open-ended stubs to λg/2 short-ended stubs), further improvement in the upper stopband is achieved by utilizing a pair of parallel coupled lines (PCLs) as feeding lines and a pair of λg/4 high impedance short-ended stubs implemented at the input and output ports. To verify the validity of the simulated results, the prototypes of the proposed reconfigurable filters were fabricated. For the first case, measured insertion loss is less than 1.8 dB with a switchable 3-dB fractional bandwidth (FBW) range from 28% to 54%. The measured results for the second case exhibit a low insertion loss of less than 1 dB and a 3-dB fractional bandwidth that can be switched from 34% to 75%, while the center frequency is kept constant at 2.4 GHz in both cases.

An Ultra-Compact On-Chip Reconfigurable Bandpass Filter With Semi-Lumped Topology by Using GaAs pHEMT Technology

A semi-lumped reconfigurable on-chip bandpass filter with GaAs pHEMT technology is presented in this paper. Three order tunable bandpass filter is designed with serial lumped capacitors, parallel resonators, and reconfigurable components. The operating bands are adjusted by field effect transistors and its corresponding gate bias circuits with GaAs technology. The semi-lumped topology, intending to reduce the size of the circuit, is employed to construct the parallel resonators, which are implemented with short-ended stubs and metal-insulator-metal capacitors. The equivalent circuit model is built to interpret the mechanism of the on-chip reconfigurable bandpass filter. Compared with the traditional tunable filters, an ultra-compactness feature and low insertion loss are obtained with the proposed design. The size of the on-chip filter is only 0.8×1.07 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is equivalent to 0.08×0.11 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 10 GHz. The presented filter is reconfigurable in two frequency bands, one is centered at 10 GHz with a fraction bandwidth (FBW) of 24.94% and the other is operated at 8.8 GHz with a FBW of 13.35%. The tuning range of the FBW is 30.6%. Good agreements are observed between the simulated and measured S-parameters.

Synthesis Design of Equal-Ripple and Quasi-Elliptic Wideband BPFs With Independently Reconfigurable Lower Passband Edge

This paper presents a new synthesis design of equal-ripple and quasi-elliptic wideband band-pass filters (WB BPFs) with independently reconfigurable lower passband edge. The synthesis design starts from a 5th-order LC circuit. By using optimum multipole concept, a T-shaped resonator for the design of Chebyshev BPF without redundant elements can be directly derived, which is formed by a pair of parallel-coupled lines and short-ended stub. To sharpen the selectivity and maintain equal-ripple response, a pair of transmission zeros are introduced through replacing the short-ended stub by its multi-section counterparts. Thus, two prototypes, whose equivalent LC circuits can be directly derived, are presented for the synthesis of equal-ripple and quasi-elliptic BPFs. To realize the desired reconfigurable response, a capacitor is used. By controlling the capacitance value, the lower passband edge can be independently tunable in continue manners while the upper one is fixed. For validation, two prototypes with fixed and reconfigurable band-width are fabricated and measured. As the measured and simulated results agree well with each other, a high-efficiency design of reconfigurable-bandwidth WB BPFs is validated.

Design of Low Loss Filter for UWB Wireless Signal of Ship's Multi-user under Wind and Waves

ABSTRACT Zhu, Y.; Bi, Y., and Zhang, Y., 2018. Design of low loss filter for uwb wireless signal of ship's multi-user under wind and waves. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 985–990. Coconut Creek (Florida), ISSN 0749-0208. The design of the low loss filter for the UWB wireless signal of ship's multiuser under the wind and waves is of great significance to the development of the ship communication in China. At present, the design of the filter in this aspect is completed according to the design principle of EML, and there is a problem of big difference between the test value and the actual value. The traditional UWB filter which has optimizes the structure of high pass short-ended stubs is as the design basis, in the half wavelength transmission line connecting short-ended stubs line, the resonator structure units of dual-mode and tri-mode stubs are loaded to achieve the performance of dual-trapping o...

Design of Ultraflat Phase Shifters Using Multiple Quarter-Wavelength Short-Ended Stubs

This letter presents a kind of ultraflat phase shifters using multiple quarter-wavelength ( $\lambda /4$ ) short-ended stubs. The proposed topology consists of a uniform line with multi- $\lambda /4$ short-ended stubs and a reference line. Inspired by the high-pass filter design, the phase difference can be analytically determined by the impedance and the number of the short-ended stubs. In order to obtain a wider phase bandwidth with ultraflat phase difference around the center operating frequency, a generalized design equation is newly derived over a wide achievable range from 15° to 360°. As a validation, the third-order proposed phase shifter with 135° phase difference is designed and implemented at 3 GHz. The measured results show a good agreement with those obtained from simulation. The measured 10-dB impedance bandwidth achieves 102%, and the bandwidth of 135° ±5° phase difference is about 78%.

Wideband Filtering Phase Shifter Using Transversal Signal-Interference Techniques

A wideband filtering phase shifter is presented in this letter using transversal signal-interference techniques. The proposed structure creates two signal-propagation paths by introducing extra coupling between two short-ended stubs. Cascaded coupled-line sections and parallel short-ended stubs can generate a constant passband and multiple transmission zeros (TZs) in the stopband and meanwhile provide the arbitrary value of phase shift within the filtering band range. The positions of TZs and phase shift range can be easily controlled. Explicit relations between the objective filtering band and the related parameters are given, and cases with different in-band phase shift values are studied. To validate the design, a prototype is built, simulated, and tested using microstrip lines. The experimental results agree with the predicted ones, demonstrating that the device can realize any given in-band phase shift with a wideband filtering response.

Balanced Symmetrical Quasi-Reflectionless Single-and Dual-Band Bandpass Planar Filters

Microwave planar balanced single-/dual-band bandpass filters (BPFs) with symmetrical quasi-reflectionless differential-mode behavior are presented in this letter. They are made up of a direct single-/dual-band BPF branch with virtually short-ended stubs in differential-mode operation, whose input and output accesses are loaded with stub-loaded-type single-/dual-band bandstop filter (BSF) branches that are terminated with a resistor. These BSF branches exhibit a quasi-complementary transfer function with regard to the one of the BPF branch and absorb the differential-mode input-signal energy not transmitted by the filter to achieve quasi-reflectionless capabilities. The theoretical foundations of the proposed balanced quasi-absorptive single-/dual-band BPFs and synthesis examples are given. Furthermore, for experimental-demonstration purposes, microstrip prototypes of 3-GHz second-order single-band and 2.85/3.15-GHz first-order dual-band BPFs are manufactured and characterized.

Filtering Antenna With High Selectivity Using Multiple Coupling Paths From Source/Load to Resonators

This communication presents a filtering antenna with high selectivity using multiple coupling path from source/load to resonators. The high selectivity of the filtering antenna’s boresight gain response is achieved by a novel coupling scheme, which induces additional coupling between source/load and nonadjacent resonators to construct cross coupling paths. Thanks to the extra cross-coupling paths, the filtering antenna can generate a maximum of N radiation nulls with N resonators. Besides, a resonator using a combination of open-ended stub and short-ended stub is adopted to construct this novel coupling scheme more easily. For demonstration, a three-order filtering stacked patch antenna with a center frequency of 2.3 GHz and a fractional bandwidth of 15.2% is fabricated. Two independently controllable radiation nulls are located at 1.97 and 2.61 GHz. Unidirectional radiation patterns have been achieved with cross polarization lower than −20 dB and back lobes lower than −18 dB.