High-impedance coplanar waveguides with low attenuation

High density interconnect printed circuit board technology enables significant board size and layer count reduction. Thinner inner layer dielectric materials, reduced line widths, and closer spaced components inherent in high density board technology require a change in electrical design methodology. Most notably, the thinner dielectric thickness significantly impacts the electrical performance of the circuit board with respect to crosstalk, board capacitance, via inductance, and controlled impedance. Via inductance is significantly reduced as mechanically drilled through hole vias are replaced with microvias. Distributed capacitance will tend to increase because of the thinner dielectric layer and crosstalk between signal traces run on adjacent layers may also increase. Using either FR-4 type epoxy (diel, cnst.=4.0) or higher performance materials (diel, cnst.=2.8) conventional controlled impedance structures such as a stripline, microstrip, and coplanar waveguide are possible to design using current manufacturing capabilities. A 50 /spl Omega/ impedance can be achieved by a microstrip or a coplanar waveguide using either dielectric material. The stripline can only achieve approximately 35 /spl Omega/ with the higher performance material and 25 /spl Omega/ with the FR-4 type epoxy material. A 500 mW radio frequency receiver and transmitter module operating at 467 MHz was successfully fabricated using a three layer build-up high density circuit board. The circuit board construction had one build-up layer fabricated with a liquid epoxy material. The circuit board electrical design incorporated microstrip, stripline, and coplanar waveguide controlled impedance structures. The results of the electrical performance measurements indicated that transmitted power, receiver sensitivity, and frequency specification performance were similar to a six layer board manufactured with conventional technology.

A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology.

We investigated the propagation losses and the characteristic impedances Z/sub L/ of coplanar waveguides (CPWs) and microstrip lines (MSLs) on a planar lightwave circuit (PLC)-platform formed on a silica/silicon substrate. The loss of the CPWs was 2.7 dB/cm at 10 GHz on the PLC-platform with 30 /spl mu/m thick silica layer. Thus, a cm-order circuit of this CPW is difficult to fabricate in the 10 Gb/s module. This is because the silicon substrate has a large loss tangent (tan /spl delta/). On the other hand, the loss of the MSLs, where a ground plane shielded the high loss silicon substrate, could be improved to 0.9 dB/cm at 10 GHz with 30 /spl mu/m thick polyimide. These lower loss MSLs on a PLC-platform can be applied to module operation at 10 Gb/s. Furthermore they have the advantage that they are suitable for application to array device circuits or circuits in a module where several devices are integrated because unlike CPWs the ground planes are not divided by signal lines or DC bias lines. The structure of CPWs and MSLs on a PLC-platform with a Z/sub L/ of 50 /spl Omega/ was also studied in detail.

High performance coplanar waveguides (CPWs) on GaN membrane technology for AlGaN/GaN high electron mobility transistors (HEMTs) grown on low-resistivity (LR) Si substrates have been demonstrated in this work. The developed CPW technology shows a remarkable improvement in RF losses when the lossy Si beneath CPW structures is removed, resulting in comparable RF performance to that of CPW realized on high-resistivity (HR) Si and semi-insulating (SI) SiC substrates, with similar AlGaN/GaN top epitaxial layers. Experimental results, first to be reported, demonstrate transmission losses ( $S_{21}$ ) of 0.47 dB and $Q$ -factor of 20.77 for the CPW on GaN membrane technology, compared to $S_{21}$ of 2.95 dB and $Q$ -factor of 4.51 for the CPW on GaN-on-LR Si, at 40 GHz. Furthermore, the influence of substrate parasitics on RF performance of CPW on GaN-based HEMTs grown on various substrates was studied and analyzed by the extraction of transmission line parameters for frequencies up to 40 GHz. These findings offer viable integrated GaN-based HEMTs on LR Si technology suitable for high-power and high-temperature system applications at RF and millimeter-wave frequencies, when used in conjunction with high thermal coefficient materials such as diamond and AIN.

This letter presents a high isolation dual-frequency orthogonally polarized rectangular patch antenna utilizing microstrip feed line integrated with a defected ground structure (DGS). The demonstrated approach results in a significant improvement in port isolation in comparison to a conventional dual-polarized antenna fed by simple microstrip lines. Measurements show an improvement of 20 dB in port isolation relative to the conventional antenna, operating at 2 and 2.5 GHz. Image impedance of a microstrip line with DGS is controlled by the DGS geometry without modifying the dimension of the line. A 150 /spl Omega/ high impedance line is effectively implemented using a microstrip line with 75 /spl Omega/ line width by incorporating the DGS.

We present the design and development of an ultra-violet (UV) LIGA (a German acronym for electroplating, lithography and molding) micromachining process on silicon substrates at microwave/millimeter wave frequencies. The process employs an ultra-thick negative photoresist SU-8 that can be spin-coated and processed using conventional lithography techniques. Using this process, we have developed micromachined coplanar waveguide (CPW) interconnects on Si substrates. The conductor-backed micromachined CPW on Si (7.2 /spl Omega/-cm) achieves a measured attenuation of 0.18 dB/cm at 20 GHz.

Several new nonperiodic spatial codes for phase-reversal coplanar waveguides (CPWs) used in the framework of the quasi-phase match technique (QPM) for broadening the optical response of z-cut LiNbO/sub 3/ electrooptic modulators (EOMs) are presented. The peculiarity of the codes is that they open the possibility for time-domain applications of EOMs based on nonperiodic QPM structures. They were obtained by using a specialized version of the genetic algorithm that generates an optimal length and number of the phase-reversal sections. The codes provide both flat amplitude and nearly linear phase frequency responses of the EOM within several frequency ranges important for fiber-optical/radio systems: from dc to 25, 40, and 90 GHz. The phase-reversal structures described here were optimized taking into account the CPW electrode losses and under the matching condition with 50 /spl Omega/-sources. They possess as low value of the drive voltage (V/sub /spl pi//, required for realization of 100% EO modulation efficiency) as possible for EOMs based on QPM, under the above conditions.

This paper proposes and studies a novel design of a coplanar waveguide (CPW) fed circular disc monopole antenna for ultra wideband (UWB) applications. A circular disc monopole printed on a dielectric substrate and fed by a 50 /spl Omega/ CPW on the same layer is demonstrated numerically and experimentally to yield an ultra wide -10 dB bandwidth with omnidirectional radiation patterns over the entire bandwidth. The effect of the disc dimension on the antenna performance is also investigated.

A planar circularly-polarized (CP) small antenna is proposed. To obtain a low profile configuration, a co-planar waveguide (CPW) structure is employed. Circular polarization is achieved using a curved stub that generates current distribution in a direction orthogonal to the current distribution from the patch. Using meander lines and a series gap capacitance, a 70% size reduction is achieved compared to a half-wavelength resonant antenna. To the best of the authors' knowledge, the proposed antenna is the smallest CP antenna using CPW technology. The measured 3dB axial ratio bandwidth is 8.3% from 3.83GHz to 4.16GHz, and a 1.6dBic gain and 89% efficiency are achieved.

A novel ultra-wideband (UWB) bandpass filter (BPF) with dual notched bands using the hybrid microstrip and coplanar waveguide (CPW) structure is proposed, to prevent interference problems between the UWB radio system and existing radio systems. A multiple-mode resonator on a CPW is formed to allocate its first three resonant modes around the lower-end, centre and upper-end of the 3.1 to 10.6 GHz UWB passband. Its two sides are fed by two microstrip-to-CPW transitions with enhanced frequency-dispersive coupling degree. The dual narrow notched bands are introduced by embedding a open stub in the CPW line and etching two U-shaped slots on the ground plane to form defected ground structures (DGSs) in each side of the microstrip structure. Then, dual-band rejected filtering properties in the C-band (3.7–4.2 GHz) and WLAN (5.15–5.825 GHz) are achieved. The UWB bandpass filter with notched bands has been carried out by designs and related simulations to demonstrate the notch-band-included and upper-stopband-improved performances.

A new wideband magneto-electric dipole antenna using coplanar waveguide (CPW) structure is proposed in this paper. The proposed antenna consists of a pair of horizontal triangular patches and two vertically oriented L-shaped strips. By introducing triangular patches working as an electric dipole, the antenna can operate in a wide band. With the use of L-shaped strips equivalent to a magnetic dipole, the antenna is low in proflle. A microstrip feed line is located between the two L-shaped strips to form a coplanar waveguide structure and excite the antenna. By carefully adjusting the gap between the feed line and the strips, the impedance bandwidth can be improved largely. A parametric study is performed to provide information for designing and optimizing such an antenna. A prototype is fabricated and measured. The simulated and measured results show that the impedance bandwidth for SWR less than 2 of the proposed antenna is 58.7% (1.95{3.57GHz). Due to the complementary nature of the antenna, the proposed antenna has a unidirectional radiation pattern with low-polarization and low back-lobe radiation over the whole operating band. Furthermore, the gain of the antenna is stable across the entire bandwidth.

A smiley-shaped monopole dual band antenna fed with a coplanar waveguide is present in this paper. Teflon substrate with a δ value of 2.1 and a thickness of 1.6mm was been used to create the antenna. The dimension of the designed smiley face structure is about 0.012λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> mm×0.012 λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> mm ×0.009λ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> mm and a metamaterial of ring structure is loaded. A coplanar waveguide (CPW) structure feds a smiley shape radiator to form the radiation at an edge of patch. The antenna has a dual band of frequency in the range of 1GHz to 10GHz that resonates. The highest bandwidth is 1500MHz, and return loss is 34dB. This simple structure smiley antenna is highly suitable for health tracking applications.

In this paper the Single Layer Reduction (SLR) technique is presented to compute dispersion characteristics of multilayer coplanar waveguide (CPW) with finite conductor thickness. The effective relative permittivity for the multilayer structure is derived from conformal mapping. Then SLR technique is used to convert multilayer CPW structure to an equivalent single layer structure. The dispersion characteristic of equivalent CPW structure is calculated from the closed form expressions.

Fabricating transparent waveguide for wireless communication

A single layer, low profile, compact metamaterial zeroth-order resonator (ZOR) antenna has been proposed in this paper. A composite right/left-handed (CRLH) transmission line structure that is comprised of a single unit cell makes up the complete antenna. The design complexity of the proposed antenna is very low, since it does not involve any vias. A symmetric coplanar waveguide (CPW) structure is chosen to have design flexibility and to satisfy the design constraints. The main aim of incorporating the left handed behaviour into the design is to achieve compactness. The resonant frequency of zeroth-order mode is around 5.8GHz. A prototype of the proposed antenna has been fabricated and it has the dimensions of 0.348λo × 0.309λo × 0.033λo. The simulated peak gain of the antenna is found to be 0.65dBi. A significant amount of size reduction is observed in the patch area of proposed structure when compared to a regular patch antenna operating at the same frequency. The metamaterial behaviour has been verified with the help of dispersion diagram and vector electric field plot. Simulation is done so as to plot the reflection coefficient of the presented CPW ZOR antenna and it is also observed on the vector network analyzer (VNA). Simulation results show that the proposed ZOR antenna achieves −10dB impedance bandwidth of 7.76% and has a radiation efficiency of about 81.27% at the ZOR mode.