Design of Composite Right/Left-Handed Coplanar-Waveguide Bandpass and Dual-Passband Filters

The design and implementation of novel coplanar-waveguide (CPW) bandpass and dual-passband filters that consist of the composite right/left-handed short-circuited stubs are proposed. In contrast to the conventional short-circuited stub, whose input impedance repeats every half-wavelength, the composite right/left-handed CPW stub combines the phase-lead composite right/left-handed CPW and the phase-lag uniform CPW to achieve the arbitrary resonant frequencies with compact size. The equivalent bandpass and dual-passband LC resonators are established by investigating the frequency responses of the composite right/left-handed CPW stubs. The composite right/left-handed CPW bandpass filter is 62.5% more compact than the conventional quarter-wavelength shunt-stub CPW bandpass filter. The composite right/left-handed CPW dual-passband filter, which possesses the sharp rejection between the two asymmetric passbands, is also developed. The synthesis procedures of the composite right/left-handed CPW bandpass and dual-passband filters are successfully validated by measurement and full-wave simulation.     

Compact dual-passband filter using lumped-element coplanar waveguide resonators

A novel dual-passband filter using the unit-cell (UC) composite right/left-handed (CRLH) coplanar waveguide (CPW) open-circuited stub and the UC electromagnetic bandgap (EBG) CPW short- circuited stub is proposed. The CRLH open-circuited and EBG short-circuited stubs in parallel connection are equivalent to the dual-passband lumped-element CPW resonators within the specific frequency range. The performance of a third-order dual-passband filter with Chebyshev responses is measured and validated by full-wave simulation.     

Open- and short-circuit terminated series stubs in finite-widthcoplanar waveguide on silicon

Open- and short-circuit terminated series stubs in finite-width coplanar waveguide (FCPW) fabricated on high-resistivity Si are experimentally characterized over the frequency range of 2-40 GHz. In coplanar waveguide (CPW), these stubs are typically placed in the center conductor, but in FCPW, the stubs may also be placed in the ground planes resulting in novel circuit elements with characteristics that make the stubs useful for matching circuits and filters. Equivalent circuit models for the stubs are presented, and it is shown that when the stub is in the ground plane the resonant frequency is equal, the inductance and resistance is halved, and the capacitance is double the values of the same stub in the center conductor. Furthermore, it is shown that by varying the stub position in the ground plane, higher Q stubs can be obtained     

Theoretical and experimental characterization of coplanar waveguidediscontinuities for filter applications

A full-wave analysis of shielded coplanar waveguide (CPW) two-port discontinuities based on the solution of an appropriate surface integral equation in the space domain is presented. Frequency-dependent scattering parameters for open-end and short-end CPW stubs are computed using this method. The numerically derived results are compared with measurements performed in the frequency range 5-25 GHz and show very good agreement. From the scattering parameters, lumped-element equivalent circuits have been derived to model the discontinuities. The inductors and capacitors of these models have been represented by closed-form equations, as functions of the stub length, to compute the circuit element values for these discontinuities     

Asymmetric Dual-Passband Coplanar Waveguide Filters Using Periodic Composite Right/Left-Handed and Quarter-Wavelength Stubs

A novel dual-passband coplanar waveguide (CPW) filter periodically loaded with the composite right/left-handed (CRLH) short-circuited stubs and the quarter-wavelength open-circuited stubs in asymmetric configuration is presented. The unit-cell equivalent circuit of the periodic structure in conjunction with Floquet's theorem is employed to find the propagation characteristics of passband and stopband regions. Unlike the conventional quarter-wavelength transmission-line inverter suitable only for a narrow frequency range, the dual-band inverter is adopted in the dual-passband filter to achieve a better frequency response within two operating bands. The performance of the 2.4/5.8-GHz third-order CRLH CPW dual-passband filter with 52% and 23% bandwidths is measured and validated by full-wave simulation. Two arbitrary passband regions are presented and the stopband within the passbands can be controlled by varying the length of open-circuited stub, supporting the flexibility and compactness of the proposed dual-passband filter     

Study of various shapes of the coupling slot in CPW-fed microstripantennas

A numerical modeling based on the solution of coupled integral equations is used for the characterization of CPW-fed aperture-coupled microstrip antennas. Various shapes of excitation slots, such as open stubs, slot loops, and capacitively and inductively coupled slots, are investigated in terms of return loss and front-to-back radiated power ratio. It is shown that a centered CPW open stub gives a minimum of back radiation while allowing for easy matching. The slot-loop excitation seems to be a convenient feeding mechanism that also allows the insertion of active devices     

Low conversion-loss fourth subharmonic mixers incorporating CMRC for millimeter-wave applications

Low conversion-loss millimeter-wave fourth subharmonic (SH) mixer designs are proposed in this paper. A millimeter-wave (35 GHz) fourth SH mixer with four open/shorted stubs is designed and measured. The conversion loss is less than 15 dB within a 2.4-GHz bandwidth. The minimum loss is 11.5 dB at the center frequency. By replacing two of the shunt stubs with a dual-frequency in-line stub consisting of newly developed compact microstrip resonating cells (CMRCs), the performance of the SH mixer is improved significantly. At 35 GHz, the conversion loss of this new fourth SH mixer is as low as 6.1 dB with a 3-dB bandwidth of 6 GHz. The conversion loss in the whole Ka-band (26.5-40 GHz) is less than 16 dB. The proposed fourth SH mixer incorporating with CMRCs provides a low-cost high-performance solution for RF subsystem design.     

Highrise Building Reradiation and Detuning at MF

An evaluation of the reradiation from highrise buildings in the MF broadcast band is presented. Scattered field measurements were made at MF on buildings of the order of one quarter wavelength in electrical height and at UHF on scale models. A computational model incorporating the effects of lossy ground and building materials was developed using moment-method techniques. Reduction of scattering is demonstrated, both for models and a full-scale building, using simple wire detuning stubs to modify the induced RF currents. The current distributions resulting in the decrease of scattering are described for a vertical stub like those used in power line detuning, and for two related new designs, a rooftop stub and the "umbrella" stub. The latter is shown to be the most effective, yielding scattered field reductions of the order of 6dB in fullscale tests.     

Compact CPW-Fed ultrawideband MIMO antenna using hexagonal ring monopole antenna elements

In this paper, a compact coplanar waveguide (CPW) fed ultra-wide band (UWB) multi input multi output (MIMO) antenna is proposed. The antenna consists of two antiparallel hexagonal ring monopole elements. Circular arcs shaped grounded stubs are used to enhance the isolation, both the arcs are connected through stub to make common ground. Tapering of the slots of CPW feed line at feed point, and grounded slots are introduced for impedance matching over UWB. The proposed antenna is fabricated and impedance bandwidth, isolation, radiation pattern, and gain are measured. Moreover, envelop correlation coefficient (ECC) results are given. Proposed antenna structure operates in the frequency range 3–12 GHz with a fractional bandwidth of 120% keeping isolation better than 15 dB. The antenna has a compact size of 45 × 25 mm².     

Compact Ultra-Wideband Bandpass Filters Using Composite Microstrip–Coplanar-Waveguide Structure

Compact ultra-wideband bandpass filters are proposed based on the composite microstrip–coplanar-waveguide (CPW) structure. In this study, the microstrip–CPW transitions and the CPW shorted stubs are adopted as quasi-lumped-circuit elements for realizing a three-pole high-pass filter prototype. By introducing a cross-coupled capacitance between input and output ports of this high-pass filter and suitably designing the transition stretch stubs, a compact three-pole ultra-wideband bandpass filter is implemented with two transmission zeros located close to the passband edges. To further improve the selectivity, two microstrip shorted stubs are added to implement a five-pole ultra-wideband bandpass filter with good out-of-band response. Being developed from the quasi-lumped elements, and not from the transmission lines, the proposed ultra-wideband filters have sizes more compact than those of the published wideband filters. The proposed ultra-wideband filters have the merits of compact size, flat group delay, good insertion/return loss, and good selectivity. Agreement between simulated and measured responses of these filters is demonstrated.     

Compact MMIC CPW and asymmetric CPS branch-line couplers and Wilkinson dividers using shunt and series stub loading

Circuit size may be reduced by up to 60% by embedding series and shunt uniplanar stubs inside the main uniplanar line since this reuses physical space in the longitudinal direction. This size-efficient stub loading of the main uniplanar line results in robust options for designing compact K-band 90/spl deg/ hybrid couplers and Wilkinson dividers. The approach is confirmed by experimental results that agree well with theory up to at least 30 GHz using both coplanar waveguide (CPW) and asymmetric coplanar stripline (ACPS). Furthermore, these couplers and dividers do not use lumped inductors or capacitors and, consequently, have excellent design accuracy even at millimeter-wave frequencies. Additionally, it is shown that it is possible to design an ACPS 90/spl deg/ branch-line coupler without the conventional CPW quarter wavelength transformers used to match the input and output port characteristic impedances.     

New miniature broadband CPW-to-slotline transitions

This paper proposes a novel class of uniplanar coplanar waveguide (CPW)-to-slotline transitions, which is particularly suitable for monolithic millimeter-wave integrated circuits. Instead of using CPW series stub printed in the ground plane, as is the case in classical CPW-to-slotline transition, this paper shows the capability to use a CPW series stub printed in the center conductor of the CPW. Compared to classical CPW-to-slotline transitions, the proposed transitions have the following advantages: additional degrees of freedom, lower radiation loss, larger bandwidth, higher compactness, and a major reduction of the number of air bridges that are potentially expensive to build. One alternative configuration that appears to have some merit involves the use of the slotline ring resonator, which does not suffer from open-end or short-end effects and, therefore, gives more accurate resonance frequency, provides an accurate localized zero or infinite impedance point, and maintains low- or high-input impedance values over a wide frequency range, depending on the feed type. A principle of achieving such high-quality transitions is detailed and also confirmed by experimental and theoretical results, which are in good agreement up to 50 GHz. A maximum fractional bandwidth of 160% is achieved for a 10-dB return loss, and the corresponding insertion loss is less than or equal to 2 dB     

A theoretical and experimental study of coplanar waveguide shuntstubs

A comprehensive theoretical and experimental study of straight and bend coplanar waveguide (CPW) shunt stubs is presented. In the theoretical analysis, the CPW is assumed to be inside a cavity, while, the experiments are performed on open structures. For the analysis of CPW discontinuities with air-bridges, a hybrid technique has been developed which has been validated through extensive theoretical and experimental comparisons. Throughout this study, the effect of the cavity resonances on the behavior of the stubs with and without air-bridges is investigated. In addition, the encountered radiation loss due to the discontinuities is evaluated experimentally     

Quasi-static design technique for MM-wave micromachined filterswith lumped elements and series stubs

This paper describes micromachined, membrane-supported low-pass and bandpass filters which are suitable for microwave and millimeter-wave (MM-wave) application. The designs are realized in coplanar-waveguide (CPW) form using short- and open-end series stubs with integrated metal-insulator-metal (MIM) capacitors, and are compact in lateral and longitudinal dimensions. A computationally efficient analysis has been developed for the design and characterization of the filters. The technique is based on a quasi-static coupled-line (CL) treatment of the series stubs, and uses normal mode impedance parameters, which are calculated with the spectral-domain approach (SDA). Due to the broad TEM-bandwidth of the membrane-supported transmission lines, the method can accurately predict filter responses well into the rejection band. To demonstrate the above claims, the measured and simulated S-parameters of a 0.3 mm ×2.2 mm low-pass filter with a cutoff frequency at 17 GHz, and a second passband at 115 GHz, are presented. The new approach is also used in the design of bandpass filters which exhibit 1.5-2-dB insertion loss and bandwidths around 10%     

Modeling of symmetric composite right/left-handed coplanar waveguides with applications to compact bandpass filters

This study proposes an equivalent-circuit model for the composite right/left-handed (CRLH) coplanar waveguide (CPW) comprising the series interdigital capacitor and shunt meandering short-circuited stub inductor in symmetric configuration. The new technique for extracting the equivalent-circuit elements of the CRLH CPW, which include inductances, capacitances, and resistances to represent the left-handed, right-handed, and lossy characteristics, is developed based on the effective medium concept. The applications to the compact resonators and filters are presented to emphasize the unique features of the CRLH CPW. A novel CRLH CPW resonator with a 0/spl deg/ effective electrical length at resonance is proposed, which gives a 49.1% size reduction when compared with the conventional half-wavelength resonator at 5 GHz. Based on the zeroth-order CRLH CPW resonators, an inductively coupled two-pole bandpass filter with 5.4% 3-dB bandwidth and 2.7-dB insertion loss at 5 GHz is implemented, and it is 51.4% more compact than the conventional structure. A good agreement among the results of the full-wave simulation, equivalent-circuit model, published data, and measurement demonstrates the effectiveness of the proposed modeling technique. To suppress the higher order harmonic spurious passbands, the electromagnetic-bandgap CPW structures are incorporated into the proposed CRLH CPW filter.     

Planar Circuit Analysis of Microstrip Radial Stub (Short Paper)

Radial-line stubs have been found to work better than low-impedance rectangular stubs when an accurate localization of a zero-point impedance is needed. In this paper, microstrip radial-line stubs are analyzed using a planar circuit technique and characterized for design purposes. Experiments performed on various structures are in excellent agreement with the theory and confirm the suitability of such a structure as an altenative to a conventional straight stub.     

X-band monolithic transmit-receive switch based on a stub directional coupler

A new circuit realization of X-band transmit-receive switch is proposed that is based on a PHEMT-controlled stub directional coupler. The operation of the switch is analyzed. The impedances of the stubs are optimized to yield a considerably larger bandwidth of the switch. It is shown that the circuit can serve as a building block for multithrow switches.     

Full-wave, finite element analysis of irregular microstripdiscontinuities

Finite-element expansion currents are used to formulate a full-wave analysis of microstrip discontinuities. With this approach, a rigorous analysis of fairly irregular structures is possible, including radiation and surface wave effects as well as coupling between closely spaced junctions. The step, stub, and bent-stub discontinuities are analyzed using this technique. Measurements are made of three stub structures. Measured resonant frequencies agree with full-wave calculations to within 2% when the nominal measured dielectric constant and structure dimensions are used as input. Using the absolute worst case dielectric constants and dimensions as input gives an error of 3% for the low-frequency stub and less than that for the other stubs     

Stubbed Branch Line Balun

A new impedance transforming balun scheme is presented based on the branch line structure with stubs on the vertical branches. The stubbed vertical branch eliminates the unwanted even mode output and provides only the required balun output with opposite phase. Also, the use of stubs reduces the branch lengths by two times the stub length and therefore, helps to reduce the total size of the proposed balun     

微带径向短截线基于知识的人工神经网络模型

微带径向短截线具有比直微带短截线在更宽的频率范围内实现低阻抗值的优点。本文采用基于知识的人工神经网络模型模拟微带径向短截线的特性,利用已经具有的先验知识减小神经网络输入输出映射关系的复杂程度有效减少了训练样本的数量,本文建立的人工神经网络模型不仅保贸了全波有限元法的准确性,而且具有快速简便的优点。