Experimental and theoretical characterization of miniature coplanar waveguide shunt stubs patterned on the centre conductor

Several new designs are presented for coplanar waveguide (CPW) open- and short-ended shunt stubs patterned on the centre conductor. Unlike conventional stubs which are patterned on the ground plane, the new designs are more compact and less radiative. They also provide more flexibility to the design of CPW circuits. The performance of the new stubs is verified by experiment and simulation and is found to be very satisfactory over the large frequency band 0–50GHz. Experimental results obtained for a conventional and new stub show that the new stub is less radiative.     

Double-Sided Parallel-Strip Line With an Inserted Conductor Plane and Its Applications

In this paper, a novel multilayer structure using the double-sided parallel-strip line with an inserted conductor plane is investigated. A conductor plane is inserted into the middle of the substrate of the double-sided parallel-strip line in the proposed structure, which can function as virtual ground to isolate the nonidentical circuits on the top and bottom layers effectively. On the other hand, the conductor plane can be negligible for the identical circuits. Based on the new structure, a dual-band stub can be realized using the isolation characteristic of the conductor plane, where the stub can be treated as a combination of two back-to-back microstrip stubs operating at different frequencies. The common ground of the two microstrip stubs is provided by the inserted conductor plane. For demonstrating this idea, a bandpass filter with two transmission zeros is optimized, fabricated, and tested. The simulated and measured results are presented and show good agreement. The size of this filter is reduced approximately by half, as compared with that of the similar type of microstrip filters.     

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.     

A Coplanar Stripline Ultra-Wideband Bandpass Filter With Notch Band

In this letter, a design of a compact coplanar stripline ultra-wideband bandpass filter with a narrow rejection band is reported. The filter characteristic is obtained by using stepped impedance open-circuited series stubs. It is shown that the rejection band can be placed at a desired frequency by tuning the width of the high impedance section of the series stub. Full-wave simulated and experimental results of a filter prototype are presented.      

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     

A novel periodic electromagnetic bandgap structure for finite-widthconductor-backed coplanar waveguides

The one-dimensional (1-D) periodic electromagnetic bandgap (EBG) structure for the finite-width conductor-backed coplanar waveguide (FW-CBCPW) is proposed. Unlike the conventional EBG structures for the microstrip line and the coplanar waveguide (CPW), which are typically placed on one of the signal strips and the ground plane, this EBG cell is etched on both the signal strip and the upper ground plane of FW-CBCPW resulting in a novel circuit element. The equivalent circuit is also used to model the EBG cell. Measured and full-wave simulated results show that the cell exhibits remarkable stopband effect. The low-pass filter with lower cutoff frequency and wider rejection bandwidth is constructed from a serial connection of the EBG cells. The effect of back metallization on the guiding characteristic is also discussed. Compared to the published EBG cells, the proposed structure has the advantages of relative flexibility, higher compactness, lower radiation loss, and easier integration with the uniplanar circuits     

应用模拟退火算法建立共面波导结构的等效电路

对中心导带和地渐变的共面波导结构提出了一种简单通用的方法,建立了其等效电路,通过模拟退火算法优化提取了电路参数.将这种方法应用于分析两种周期性共面波导结构,比较了由等效电路模型与实验得出的散射参数,得到了很好的一致性.     

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     

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     

Bandstop Filter in Nonradiative Dielectric Waveguide Using Rectangular Resonators

A bandstop filter realized by means of rectangular resonators coupled to the center dielectric strip of a nonradiative dielectric (NRD) waveguide is described.This filter has the advantage that it is simple to manufacture, making use of a center dielectric of standard cross section. The design procedure is similar to the conventional strip line design procedure, with the stubs replaced by "stubs" of dielectric, or resonators. The design equations for the stub coupling are derived the properties of the stubs are obtained through measurement.     

Broadband Dielectric Resonator Antenna With Metal Coating

A broadband dielectric resonator (DR) antenna is proposed, which consists of a rectangular DR coated with metal on three sides and placed on a ground plane. The structure is analyzed by modelling the dielectric-air interface as perfect magnetic conductor (PMC). A coplanar waveguide (CPW) with terminating slots is used to feed the antenna. Measurement results exhibit a wide bandwidth of about 47% over which the E_thetas pattern on the horizontal plane is nearly omnidirectional. The 10-dB bandwidth of this broadband DR monopole covers 4.2-6.8 GHz. Hence, it can be used for WLAN 802.11a applications     

Compact-size coplanar waveguide bandpass filter

A compact-size coplanar waveguide (CPW) bandpass filter (BPF) is proposed. In this study, we use the bended stub with novel folded skill to improve the three parallel coupled-lines structure of BPF for N = 1. It gets the sharp transition band (TB) and reduces the dimension of the circuit by 66.67% at 2.45 GHz. Its center frequency can be shifted easily by adjusting the interfaces of SS and S'S' simultaneously. It is very useful for applications in the wireless communication systems.     

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 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.     

Microstrip antennas fed by conductor backed coplanar waveguides

A microstrip antenna fed by a conductor backed coplanar waveguide is demonstrated. The addition of a back-side metallic ground plane involves a possible power leakage owing to the excitation of parallel plate modes (PPMs). A theoretical model, based on the solution of coupled integral equations, is validated by experimental results. It is shown that the power leakage can be avoided by a proper choice of substrate characteristics     

A wideband balun and vertical transition between conductor-backed CPW and parallel-strip transmission line

A wideband vertical transition between conductor-backed coplanar waveguide (CBCPW) and parallel-strip (PS) transmission line is presented. By choosing the same widths for the two conductor strips comprising the PS transmission line, the transition performs unbalanced-to-balanced transformation as well. Back-to-back configurations of the transition have been realized and their transmission, reflection, and direct-coupling characteristics have been measured. It is shown that the placement of vias connecting the top and the bottom grounds of the CBCPW along the entire gap between the truncated center conductor and the ground is crucial in preventing spurious resonances of the CBCPW structure. The fabricated back-to-back transition features low insertion loss over the 28:1 frequency range that has been tested.     

共面紧凑型微波光子晶体在共面波导中的应用

提出一种地平面刻蚀共面紧凑型微波光子晶体(PBG)的共面波导结构,介绍了微波光子晶体的基本单元结构,并设计出具有90°弯折的共面波导样品.使用矢量网络分析仪测试该结构的散射参数,测量结果显示,其传输特性比普通的共面波导在高频部分具有较大的提高.同时,相比于传统的三维微波光子晶体,该结构具有导体损耗小,加工工艺简单,便于应用于光电封装和单片微波集成电路的特点.

Abstract：

A novel coplanar waveguide using coplanar compact microwave photonic-handgap (PBG) structure is proposed. The basic unit of microwave PBG structure is introduced and a waveguide sample with a 90 degree break is designed. Testing results obtained through vector network analyzer display an obvious promotion in transmission parameter, especially in the high frequency part. Meanwhile, compared with the common 3-dimension microwave PBG structure, this structure with a low conductor loss can be processed with standard planar fabrication technology, which makes it applicable in opto-electronic package and monolithic microwave integrated circuit (MMIC).     

超导共面波导谐振腔稳频振荡器的实验研究

对共面波导谐振腔稳频振荡器进行了实验研究。在对不加谐振腔的简单振荡器研究的基础上，设计并制作了反馈型和传输型谐振腔稳频振荡器。首先，稳频谐振腔分别用常规导体介质基片和在ＺｒＯ衬底上的金膜来实现。然后，用ＬａＡｌＯ３介质衬底上的ＹＢＣＯ超导薄膜制作的共面波导稳频谐振腔嵌入振荡器电路，利用其高品质因数取得较好的稳频效果。所有电路的有源器件均采用ＮＥ７２０８４ＧａＡｓＭＥＳＦＥＴ。     

A circularly polarized slot antenna for high gain applications

A coplanar waveguide fed slot antenna for wideband circular polarization is designed and experimentally validated. The rectangular slot is excited using a stepped feed line terminated on a circular disc shaped tuning stub. To obtain circular polarization, inverted L-shaped strips are attached to the ground plane at the opposite corners while a rectangular slit is cut in the circular disc. The combined bandwidth (3-dB axial ratio and 10 dB impedance matching) achieved is 48% (4.35–7.1 GHz) under simulation and 40% (4.75–7.1 GHz) in measurement. The gain of the antenna is next enhanced by the application of a double layered square loop frequency selective surface. The frequency selective surface is used as a reflector placed beneath the antenna at an optimum distance. An improvement of about 4 dB is seen in the measured peak gain over most of the operating band. Experimental results are presented to characterize the antenna and the frequency selective surface and they are found to be in good agreement with the simulated results.     

Size-reduction techniques for CPW and ACPS structures

In coplanar-waveguide technology, there is a possibility of locating shunt and series matching stubs inside the center conductor of the transmission line. This principle can be used to reduce of the dimensions of microwave components such as monolithic microwave integrated circuits. This paper discusses the concept and presents the design of a reduced-size Wilkinson divider based on the realization of short-circuit series stubs in the signal conductor of an asymmetric coplanar stripline