Silicon micromachined EBG resonator and two-pole filter with improved performance characteristics

A novel micromachined resonator at 45 GHz based on a defect in a periodic electromagnetic bandgap structure (EBG) and a two-pole Tchebyshev filter with 1.4% 0.15 dB equiripple bandwidth and 2.3 dB loss employing this resonator are presented in this letter. The periodic bandgap structure is realized on a 400 /spl mu/m thick high-resistivity silicon wafer using deep reactive ion etching techniques. The resonator and filter can be accessed via coplanar waveguide feeds.     

Characterization of micromachined silicon rectangular waveguide at 400 GHz

We present the first characterization of a micromachined silicon rectangular waveguide at 400GHz. The silicon waveguide has an average loss of 0.086dB/mm for a range of 350-460GHz. The waveguides are formed using well known microfabrication techniques and demonstrate a successful first step towards the use of silicon waveguides as a viable option for THz systems.     

Multilayer Dual-Band Filter Using a Reflector Cavity and Dual-Mode Resonators

A dual-band filter has been designed using a multilayer approach. The structure includes a reflector cavity and dual-mode resonators. The walls of the reflector cavity have been designed using metalized vias enabling the integration characteristics of standard planar microwave circuits. The principle includes the passband division of a fourth-order fully canonical form into two narrowband second-order passbands. The designed topology exhibits a dual-band response with center frequencies of 5.2 and 5.7GHz and in-between isolation of 30 dB created by two in-band transmission zeros. The enclosing cavity reduces radiation loss and increases the unloaded of the resonant modes. The hybrid design provides insertion losses better than 1.7 dB and narrow fractional bandwidths of 2.5%.     

Low-loss LTCC cavity filters using system-on-package technology at 60 GHz

In this paper, three-dimensional (3-D) integrated cavity resonators and filters consisting of via walls are demonstrated as a system-on-package compact solution for RF front-end modules at 60 GHz using low-temperature cofired ceramic (LTCC) technology. Slot excitation with a /spl lambda/g/4 open stub has been applied and evaluated in terms of experimental performance and fabrication accuracy and simplicity. The strongly coupled cavity resonator provides an insertion loss <0.84 dB, a return loss >20.6 dB over the passband (/spl sim/0.89 GHz), and a 3-dB bandwidth of approximately 1.5% (/spl sim/0.89 GHz), as well as a simple fabrication of the feeding structure (since it does not require to drill vias to implement the feeding structure). The design has been utilized to develop a 3-D low-loss three-pole bandpass filter for 60-GHz wireless local area network narrow-band (/spl sim/1 GHz) applications. This is the first demonstration entirely authenticated by measurement data for 60-GHz 3-D LTCC cavity filters. This filter exhibits an insertion loss of 2.14 dB at the center frequency of 58.7 GHz, a rejection >16.4 dB over the passband, and a 3-dB bandwidth approximately 1.38% (/spl sim/0.9 GHz).     

Development of a wide-band short backfire antenna excited by an unbalance-fed H-shaped slot

The short backfire antenna (SBA) has been widely used for mobile satellite communications, tracking, telemetry, and wireless local-area network applications due to its compact structure and excellent radiation characteristics. The most common excitation topology for the SBA is a balance-fed wire dipole, which has the disadvantage of a narrow frequency bandwidth for the input impedance. In this paper, an H-shaped slot is employed to excite the SBA for the first time. The H-shaped slot is unbalance-fed from a coaxial line. It is demonstrated that the H-shaped slot-excited SBA can achieve a bandwidth for input impedance of more than 20% (VSWR<2) while maintaining good radiation performance. The antenna structure is described and the simulation and experimental results are presented. The operating principle is investigated to explain why the slot-excited SBA can result in good impedance and radiation characteristics. A parametric study is conducted for the use of practical engineering design.     

Decolorization and degradation of reactive azo dyes via heterogeneous photocatalytic processes

Reactive dyes are extensively used in textile industry in the last years due to their superior performance, but they are environmentally hazardous and difficult to treat effectively by classical methods. In the present work, the decolorization and degradation of four commercial reactive azo dyes, namely Remazol Red RR, Remazol Yellow RR, Procion Crimson H-exl and Procion Yellow H-exl, were studied using photocatalytic processes (TiO₂/UV and TiO₂/UV/H₂O₂). Decolorization and degradation were found to strongly depend on the system parameters (TiO₂ loading, dye and H₂O₂ initial concentrations, and pH). Decolorization efficiency (%) sharply increases with increasing the TiO₂ loading, especially up to 1 g/L, as well as with decreasing the initial dye concentration from 250 down to 50 mg/L. At pH = 3, a > 90% decolorization of all dyes can be achieved in only 15 min. Addition of H₂O₂ increases the decolorization rates up to an optimum value (97.9% Remazol Red RR decolorization at 12 min irradiation, with a 0.5%w/w initial H₂O₂ concentration and pH = 3). Among the four dyes examined, significant differences in decolorization and degradation rates were revealed, but decolorization and degradation efficiencies up to 100% (in 25 min and 4 h respectively) are possible with proper combinations of the system parameters.     

5 bit, silicon-based, X-band phase shifter using a hybrid pi/t high-pass/low-pass topology

A hybrid pi/t bit passive topology is presented to enable a significant reduction in the die area for a high-pass/low-pass phase shifter is presented. A hybrid-topology 5 bit digital X-band phase shifter was designed, fabricated and tested using a 200 GHz, 0.13 mum SiGe bipolar complementary metal oxide semiconductor (BiCMOS) technology. Size and performance characteristics are presented as a contrast to an all-pi phase shifter recently presented by Comeau et al. using the same SiGe BiCMOS technology and design goals. With similar bit passive performance to the all-pi design, the hybrid shifter allows for a total shifter die-area reduction of 50.5%. The absolute phase error of the shifter was less than plusmn13 from 8 to 12 GHz, with an average insertion loss of -20 dB.     

Modified Wilkinson Power Dividers for Millimeter-Wave Integrated Circuits

A modification of the Wilkinson power divider is presented that eases planar implementation while maintaining performance. By adding transmission lines between the resistor and the quarter-wave transformers of the traditional design, a range of valid solutions exists that meet the conditions of being reciprocal, isolated between the output ports, and matched at all ports. The proposed design is particularly useful at millimeter-wave frequencies where reduced physical dimensions make a circuit configuration suitable for low-cost package-level implementation difficult using traditional methods. Two frequency bands are demonstrated. At V-band, the circuit gives 0.3-dB excess insertion loss, 19-dB isolation, and 50% bandwidth. At the W-band, the circuit gives 0.75-dB excess insertion loss, 24-dB isolation, and 39% bandwidth.     

Wideband coplanar waveguide RF probe pad to microstrip transitions without via holes

A novel via-less coplanar waveguide (CPW) to microstrip transition is discussed and design rules based on simulations and experimental results are presented. This transition demonstrates a maximum insertion loss of 1 dB over the frequency range from 10 GHz to 40 GHz with a value of 0.4 dB at 20 GHz. This transition could find a variety of applications due to its compatibility with RF systems-on-a chip, low loss performance, low cost and its ease of fabrication.     

Crosstalk between finite ground coplanar waveguides over polyimide layers for 3-D MMICs on Si substrates

Finite-ground coplanar (FGC) waveguide lines on top of polyimide layers are frequently used to construct three-dimensional Si-SiGe monolithic microwave/millimeter-wave integrated circuits on silicon substrates. Requirements for high-density, low-cost, and compact RF front ends on silicon can lead, however, to high crosstalk between FGC lines and overall circuit performance degradation. This paper presents theoretical and experimental results and associated design guidelines for FGC line coupling on both highand low-resistivity silicon wafers with a polyimide overlay. It is shown that a gap as small as 6 /spl mu/m between two adjacent FGC lines can reduce crosstalk by at least 10 dB, that the nature of the coupling mechanism is not the same as with microstrip lines on polyimide layers, and that the coupling is not dependent on the Si resistivity. With careful layout design, isolation values of better than -30 dB can be achieved up to very high frequencies (50 GHz).