Michael Dydyk

Coplanar waveguides and microwave inductors on silicon substrates

Silicon has many advantages as a microwave substrate material including low cost and a mature technology. The aim of this paper is to evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study. Coplanar waveguides fabricated on Si, GaAs, and quartz substrates are tested and their characteristics are compared. Microwave spiral inductors and meander lines are also fabricated on various substrates, and their performance is also analyzed. The results demonstrate that the losses of a coplanar transmission line (CPW) realized on high-resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate covered with insulators. Furthermore, measured unloaded Qs of microwave inductive structures on high-resistivity silicon substrates are comparable to the measured unloaded Qs of the same structures on GaAs and on quartz. This paper demonstrates that high-resistivity Si can be used as a microwave substrate. >

Microstrip directional couplers with ideal performance via single-element compensation

Microstrip directional couplers suffer from poor directivity because of inhomogeneous dielectric, i.e., partly dielectric substrate, partly air. It is possible to compensate for this poor performance by introducing a single lumped capacitor or inductor at the edges or center of the coupled region. No attempt at a theoretical design of these couplers has been made in the literature. This paper fills the void by presenting an accurate approach to the design of microstrip directional couplers with ideal match or high directivity of both, using a single capacitive of inductive compensation. The method is valid for tight and loosely coupled structures. The method is validated via design and experimental results.

Accurate design of microstrip directional couplers with capacitive compensation

An accurate design is presented for microstrip directional couplers with high directivity using capacitive compensation. The method utilizes symmetry analysis and equivalency principals to develop closed-form solutions of the compensating capacitance and a new odd mode characteristics impedance necessary to realize an ideal microstrip directional coupler. The design approach is valid for any degree of coupling, thereby overcoming limitations of previous approaches to this design concept.<<ETX>>

Silicon as a microwave substrate

Silicon has many advantages as a microwave substrate material including low cost and a mature technology. The lower resistivity of Si (/spl ap/10 k /spl Omega/-cm) compared to GaAs (/spl ap/10 M /spl Omega/-cm) is perceived as a major disadvantage. In this paper, we present measured and simulated results demonstrating that the losses of a coplanar transmission line (CPW) realized on silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate with insulators. The loss mechanisms of Si and GaAs substrates used for microwave applications are analyzed using both microwave and semiconductor physics theory. A high resistivity Si substrate can be used both as a microwave substrate and an active element carrier permitting further integration at low cost.<<ETX>>

High resistivity Si as a microwave substrate

Silicon has many advantages as a system substrate material including low cost and a mature technology. However, Si has not been demonstrated as a good microwave substrate compared to semi-insulating GaAs or quartz. The aim of this paper is to evaluate the potential of using high-resistivity silicon as a low-cost low-loss microwave substrate through an experimental comparative study. Coplanar waveguides fabricated on Si, GaAs and quartz substrates are tested and their characteristics are compared. Microwave spiral inductors and meander lines are also fabricated on various substrates, and their performance is also analyzed. The results demonstrate that the losses of a coplanar transmission line (CPW) realized on high-resistivity (3 k to 7 k /spl Omega/-cm) silicon substrates are comparable to the losses of a CPW realized on a GaAs substrate covered with insulator. Furthermore, measured unloaded Qs of microwave inductive structures on high-resistivity silicon substrates are comparable to the measured unloaded Qs of the same structures on GaAs and on quartz. The measured results are explained using both microwave and semiconductor physics theory. This paper demonstrates that high-resistivity Si can be used as a microwave substrate.

Efficient, Higher Order Mode Resonance Combiner

This paper will discuss a power combining approach that uses a higher order mode cavity resonance without mode suppressors to achieve a highly stable and efficient combiner. This is made possible by proper handling of the undesirable resonances. The application of this approach to a Ku-band 12 GaAs IMPATT diode combiner will be discussed.

Theoretical and experimental investigation of bias and temperature effects on high resistivity silicon substrates for RF applications

Theoretical and experimental comparisons show that the RF characteristics of a CPW in Schottky contact with a HR Si substrate are bias independent for all practical temperatures, up to 100/spl deg/C. Bias dependence on the RF characteristics of the transmission line are noticed above 100/spl deg/C when the ohmic dielectric loss of the HR Si becomes the dominant loss mechanism on the coplanar structures under study. This is a direct result of the increase of intrinsic carrier density.

MMIC Reflection Coefficient Synthesizer For On-Wafer Noise Parameter Extraction

This paper will summarize Noise Parameter Extraction Methods, discuss their limitations and present a novel approach to improving accuracy by incorporating an MMIC reflection coefficient synthesizer into Coplanar Waveguide probe. Products offered by ATN and Cascade Microtech, Inc. that permit automated noise parameter measurements on wafer are limited in accuracy because the variable source impedance necessary for proper operation of the system is connected through a probe which exhibits loss. This loss limits the maximum reflection coefficient presented to the device under test (DUT) and consequently impacts the accuracy of measurements as frequency increases. The reason for this stems from the manner the parameters are extracted. If all the reflection coefficients (or source admittances) presented (by the reflection coefficient synthesizer) are far removed from the optimum, the accuracy of predicting Fmin by extrapolation will suffer. If the accuracy of Fmin becomes questionable, so will the other parameters. To obtain a higher degree of accuracy and increase the diagnostic frequency, it is necessary to imbed the reflection coefficient synthesizer in the RF probe which is the subject of this paper. This is done primarily to reduce losses and take full advantage of the variable source generator capability. In addition, provisions have to be made to introduce a Noise Source into the system. This paper will address the implementation of such a reflection coefficient synthesizer using MMIC technology, compare simulated vs experimental results and discuss future plans.

Temperature and bias effects in high resistivity silicon substrates

The purpose of this paper is to report the results of studies dealing with the impact of temperature and DC bias on low-cost low loss high resistivity (HR) Si substrate. Measured results show that microwave performance of a coplanar transmission lines and a meander inductive structure realized on HR Si are not affected by applied DC bias from -10 V to 10 V in the temperature range from -50/spl deg/C to 50/spl deg/C. Furthermore, measured results demonstrate that the losses of the structures under study on HR Si are comparable to the losses of similar structures on semi-insulating (SI) GaAs up to 100/spl deg/C.

Microwave Inductors on Silicon Substrates

Microwave inductive structures are fabricated on high resistivity (3 k to 7 k ¿-cm, measured) Si, GaAs, and quartz substrates under two conditions: metal-substrate and metal-insulator-substrate. The insulators are sandwiches of: SiO2(field)/Si3N4 and SiO2(field)/Si3N4 with SiO2(gate). The measured unloaded Q of single layer spirals and meander inductors on Si substrates are comparable to the measured unloaded Q of the same structures realized on GaAs and quartz substrates. These results are in agreement with the ones obtained using coplanar transmission lines (CPWs), which further confirm that high resistivity Si can be used as a microwave substrate.