Thin-film Microstrip Transmission Lines Research Articles

InP DHBT Amplifier Modules Operating Between 150–300 GHz Using Membrane Technology

In this paper, we present WR05 (140–220 GHz) and WR03 (220–325 GHz) five-stage amplifier modules with novel membrane microstrip-to-waveguide transitions. The modules use a 250-nm InP double heterojunction bipolar transistor (DHBT) technology and multilayer thin-film microstrip transmission lines. The waveguide transitions use $E$ -plane probes on 3- $\mu$ m-thin GaAs membrane substrate. Beam lead connectors integrated on the transition eliminate the need of highly reactive bond wires. In addition, process steps such as backside metallization, backside vias, and nonrectangular dicing of the integrated circuits (ICs) are not required. The WR05 amplifier module demonstrates a peak gain of 24 dB at 245 GHz and more than 10-dB gain from 155 to 270 GHz. The WR-03 module has 19-dB gain from 230 to 254 GHz with input and output return loss better than 10 dB from 225 to 330 GHz. The two modules were also characterized in terms of noise. The minimum noise figures were measured to 9.7 dB at 195 GHz and 10.8 dB at 240 GHz for the WR05 and WR03 modules, respectively. To the authors' best knowledge, these are the first published results on an InP DHBT amplifier modules operating at these high frequencies. It is also the first time that membrane technology is used for IC packaging, regardless of IC technology.

Metal Layer Losses in Thin-Film Microstrip on LTCC

Thin-film microstrip transmission lines fabricated using a Ti adhesion layer followed by layered Cu, Pt, and Au films are measured to determine tradeoffs between manufacturability issues and microwave performance. Since Ti metal has approximately 25 times the resistance of Cu, and currents in a microstrip line flow mainly at the interface with the substrate where the Ti is located, there is the possibility of increased RF signal losses with this structure. It is found that Ti adhesion layers of ≤200-nm thickness cause minimal loss through 40 GHz on DuPont 9K7 low-temperature cofired ceramic substrates, so there is no significant electrical penalty for employing a metal stackup optimized for mechanical durability. These measurements, together with analysis and simulations suggest this will hold in general as long as the thinner, higher resistance adhesion metal is well below one skin depth in thickness at the operating frequency.

The integration of thin-film microstrip and coplanar technologies for reduced-size MMICs

This paper proposes the integration of coplanar waveguide (CPW) and thin-film microstrip transmission lines to achieve size reduction of monolithic microwave integrated circuits (MMICs). The proposed structures take advantage of the multilevel metallization processes offered in MMIC technology. A very compact 90/spl deg/ CPW branchline coupler, operating at 44 GHz, is used to illustrate the technique. In comparison with conventional hybrid couplers, this coupler offers lower insertion loss and significantly smaller dimensions. The area of the coupler is approximately 65% of a conventional coupler. This paper also presents a family of novel series/shunt matching stub structures based on the CPW/thin-film microstrip combination. The technique allows a reduction in the length of matching stubs of approximately 50% by collocating multiple stubs together. Simulated and experimental results are presented in support of the novel structures.

High‐performance bulk and thin‐film microstrip transmission lines on VLSI‐standard Si substrates

AbstractMicrostrip transmission lines with very low power loss of 0.4 dB/mm at 50 GHz have been fabricated on Si substrates using an optimized ion‐implantation process. These devices have the inherent advantages of smaller chip size and better power performance than CPW lines. Using the same approach, high‐performance thin‐film microstrip lines are also developed, showing a loss of 0.9 dB/mm at 20 GHz. This approach is compatible with existing VLSI backend layout technology. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 148–151, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20404

Nanosecond pulsed field magnetization reversal in thin-filmNiFe studied by Kerr effect magnetometry

Magnetization reversal has been studied in a 5 nm thickNi80Fe20 film under the action of a pulsed magnetic field,for pulse durations between 2-102 ns. Fast pulses were applied tothe sample from a thin-film microstrip transmission line andmagnetization changes were measured using a continuous wave lasermagneto-optic Kerr effect magnetometer. The switching field was foundto increase as the pulse duration decreased, in qualitative agreementwith simple models. More unusually, the switching field was alsofound to increase as a function of a quasi-static bias field inexcess of the value of that bias. This effect is stronger for theshorter pulses. Evidence is presented which suggests that this is dueto rapid relaxation of the magnetization after the termination of thepulsed field.