Maximilian C. Scardelletti

Miniaturized Wilkinson power dividers utilizing capacitive loading

The authors report the miniaturization of a planar Wilkinson power divider by capacitive loading of the quarter wave transmission lines employed in conventional Wilkinson power dividers. Reduction of the transmission line segments from /spl lambda//4 to between /spl lambda//5 and /spl lambda//12 are reported here. The input and output lines at the three ports and the lines comprising the divider itself are coplanar waveguide (CPW) and asymmetric coplanar stripline (ACPS), respectively. The 10 GHz power dividers are fabricated on high resistivity silicon (HRS) and alumina wafers. These miniaturized dividers are 74% smaller than conventional Wilkinson power dividers, and have a return loss better than +30 dB and an insertion loss less than 0.55 dB. Design equations and a discussion about the effect of parasitic reactance on the isolation are presented for the first time.

Analysis of cylindrical transmission lines with the finite-difference time-domain method

In this paper, the finite-difference time-domain (FDTD) method is used to calculate the propagation characteristics of cylindrical transmission lines. An efficient two-dimensional FDTD algorithm is developed by projecting the three-dimensional FDTD cell in the cylindrical coordinates onto the r-/spl phi/ plane. An effective absorbing boundary condition is employed to truncate the mesh at its outer radial boundary. Numerical results are derived for different cylindrical transmission lines and compared to data available in the literature. Specifically, the newly proposed cylindrical coplanar waveguide is studied both theoretically and experimentally.

Design and Measurement of Self-Matched Dual-Frequency Coplanar Waveguide-Fed-Slot Antennas

Two new designs of dual frequency coplanar waveguide (CPW)-fed double folded slot antennas are presented. An important advantage of these antennas is that they are self-matched to the feeding CPW without the need for external matching circuit. This reduces the antenna size and simplifies its design. To verify the designs, the return loss and radiation patterns are measured and compared to those obtained using available commercial software with good agreement

RF MEMS phase shifters and their application in phase array antennas

Electronically scanned arrays are required for space based radars that are capable of tracking multiple robots, rovers, or other assets simultaneously and for beam-hopping communication systems between the various assets. ^Traditionally, these phased array antennas used GaAs Monolithic Microwave Integrated Circuit (MMIC) phase shifters, power amplifiers, and low noise amplifiers to amplify and steer the beam, but the development of RF MEMS switches over the past ten years has enabled system designers to consider replacing the GaAs MMIC phase shifters with RF Micro-Electro Mechanical System (MEMS) phase shifters. In this paper, the implication of replacing the relatively high loss GaAs MMICs with low loss MEMS phase shifters is investigated.

Electrically small folded slot antenna utilizing capacitive loaded slot lines

This paper presents an electrically small, coplanar waveguide fed, folded slot antenna that uses capacitive loading. Several antennas are fabricated with and without capacitive loading to demonstrate the ability of this design approach to reduce the resonant frequency of the antenna, which is analogous to reducing the antenna size. The antennas are fabricated on Cu-clad Rogers DuriodTM 6006 with multilayer chip capacitors to load the antennas. Simulated and measured results show close agreement, thus, validating the approach. The electrically small antennas have a measured return loss greater than 15 dB and a gain of 5.4, 5.6, and 2.7 dBi at 4.3, 3.95, and 3.65 GHz, respectively.

Ka-Band, MEMS Switched Line Phase Shifters Implemented in Finite Ground Coplanar Waveguide

Ka-band MEMS switched line one and two-bit phase shifters implemented in finite ground coplanar waveguide on High Resistivity Silicon (HRS) substrates are presented. The phase shifters are constructed of two single-pole double-throw (SPDT) switches with additional reference and phase offset transmission line lengths. The MEMS devices are doubly anchored cantilever beam capacitive switches with inductive sections (MEMS LC phase shifters have a minimum insertion loss (IL) and a maximum return loss (RL) of 0.85 dB and 30 dB and 1.8 dB and 25 dB respectively. The one-bit phase shifters designed phase shift is 22.5° and actual measured phase shift is 21.8° at 26.5 GHz. The two-bit phase shifters designed phase shift is 22.5°, 45°, and 67.5° and the actual measured phase shifts are 21.4°, 44.2°, and 65.8°, respectively, at 26.5 GHz.

High Temperature Characteristics of Coplanar Waveguide on R -Plane Sapphire and Alumina

This paper presents the characteristics of coplanar waveguide transmission lines on R-plane sapphire and alumina over the temperature range of 25degC-400degC and the frequency range of 45 MHz-50 GHz. A thru-reflect-line calibration technique and open circuited terminated stubs are used to extract the attenuation and effective permittivity. It is shown that the effective permittivity of the transmission lines and, therefore, the relative dielectric constant of the two substrates increase linearly with temperature. The attenuation of the coplanar waveguide varies linearly with temperature through 200degC, and increases at a greater rate above 200degC.

EM FULL-WAVE ANALYSIS AND TESTING OF NOVEL QUASI-ELLIPTIC MICROSTRIP FILTERS FOR ULTRA NARROWBAND FILTER DESIGN

A new class of microstrip filter structures are designed, optimized, simulated and measured for ultra-narrowband performance essential to the wireless industry applications. More accurate model of the coupling coefficient is outlined and tested for narrowband filter design. Two sample filters are fabricated and measured to verify the simulations and prove the concept. The idea behind the new designs is based on minimizing the parasitic couplings within the resonators and the inter-resonator coupling of adjacent resonators. A reduction of the overall coupling coefficient is achieved even with less resonator separation which is a major issue for compactness of such filters. The best new designs showed a simulated fractional bandwidth (FBW ) of 0.05% and 0.02% with separations of S = 0.63 mm and S = 0.45 mm, respectively. The measured filters tend to have even narrower FBW than the simulated, though its insertion loss deteriorates, possibly due to mismatch at the interface with external circuitry and poor shielding effect of the test platform. The investigated 2-pole filters are accommodated on a compact area of a nearly 0.6 cm2. An improvement of tens of times of order in narrowband performance is achieved compared to reported similar configuration filters and materials. A sharp selectivity and quasi-elliptic response are also demonstrated with good agreement in both simulations and measurements. In all filters, however, the study shows that the narrower the FBW , the larger the insertion loss (IL) and the worse the return loss (RL). This is confirmed by measurements.

Temperature Dependency (25 C - 400 C) of a Planar Folded Slot Antenna on Alumina Substrate

The dependency of planar folded slot antenna characteristics fabricated on alumina substrates over the temperature range of 25 to 400C are presented. The 3.575 GHz antenna is fed by a 20 mm long, 50 CPW line (S = 130 and W = 60 μm), and there is no ground plane on the back side of the substrate. An on-wafer TRL calibration was used to deembed the CPW feed line for return loss measurements and to measure the increase in the effective dielectric constant and attenuation of the CPW lines as a function of temperature. The measured antenna characteristics show that the resonant frequency varies by less than 1%, the minimum return loss increases from 11 to 16 dB, the quality factor increases from 25.5 to 44.75, and the gain decreases by 1 dBi as temperature is increased from 25C to 400C. Finally, the effect of the measurement test setup on the measured radiation patterns is discussed.

Hardware Architecture Study for NASA's Space Software Defined Radios

This study defines a hardware architecture approach for software defined radios to enable commonality among NASA space missions. The architecture accommodates a range of reconfigurable processing technologies including general purpose processors, digital signal processors, field programmable date arrays (FPGAs), and application specific integrated circuits (ASICs) in addition to flexible and tunable radio frequency (RF) front ends to satisfy varying mission requirements. The hardware architecture consists of modules, radio functions, and interfaces. The modules are a logical division of common radio functions that comprise a typical communication radio. This paper describes the architecture details, module definitions, the typical functions on each module and the module interfaces. Trade-offs between component-based, custom architecture and a functional-based, open architecture are described. The architecture does not specify a physical implementation internally on each module, nor does the architecture mandate the standards or ratings of the hardware used to construct the radios