R.L. Carter

Exploiting a patch antenna for strain measurements

The feasibility of applying patch antennas for strain measurement is investigated. The resonance frequency of a patch antenna is determined by the size of its metallic patch. An applied strain changes the dimensions of the metallic patch, resulting in a shift in the antenna resonant frequency. Therefore, the applied strains can be measured from the changes in antenna resonant frequency. A dual-frequency patch antenna was designed and fabricated using conventional photolithography techniques. The application of the patch antenna for strain measurement was evaluated by bonding the patch antenna to an aluminum cantilever beam and applying loads at the free end of the cantilever beam. The shifts of the return loss S11 curves under loads were correlated to the strains experienced by the patch antenna. The strain sensitivity of the antenna obtained from experimental measurements agreed well with the analytical prediction.

Ion‐implanted magnetostatic wave reflective array filters

Ion‐implanted bars have been used in fabricating magnetostatic surface wave normal incidence reflective array filters at 3.0 GHz. A theory is presented, based on a dispersion relation derived from a four layer model, and data taken agrees well with the theory. The ion‐implanted bars provide a solution to problems previously associated with etched grooves and metal bars.

Design of Sinusoidal, Triangular, and Square wave Generator Using Current Feedback Operational Amplifier (CFOA)

-This paper presents the design of a sinusoidal, triangular, and square wave generator using a high speed current feedback operational amplifier (CFOA). A macro model for the CFOA is developed as well. The frequency of oscillation in all cases are derived and compared with the simulated values. The achieved frequency of oscillation for sinusoidal wave is 9.4 MHz to 15 MHz and the achieved frequency of oscillation for the triangular/rectangular wave is 6.75 MHz to 59.5 MHz. The advantage of using the current feedback operational amplifier is to get higher frequency of sinusoidal, triangular, and square wave.

Electronically variable time delays using cascaded magnetostatic delay lines

A magnetostatic wave (MSW) variable time delay device with a phase deviation from linearity of less than 20 deg over a bandwidth of 300 MHz centered at 3 GHz has been demonstrated. The device consists of two cascaded delay lines. One delay line is biased to operate in the surface wave (MSSW) mode to provide a positive slope delay versus frequency characteristics, while the other operates in the backward volume wave (MSBVW) mode to provide a dispersive characteristic with negative slope. Both dispersions have been linearized by modifying the spacing between the propagation medium (YIG film) and the ground plane. The net device dispersion is the sum of the dispersive characteristics of the individual delay lines, and delay variability is achieved by varying the bias field of one of these components. A bias field change of 100 G will change the total delay by more than 40 ns.

Magnetostatic forward volume wave - spin wave conversion by etched gratings in LPE-YIG

Experiments in the 3 GHz region are reported normal incidence of magnetostatic forward volume waves (MSFVW) on etched groove arrays. Significant mode conversion to standing spin wave resonances (SSWR) along the axis normal to the films has been observed and correlated to the SSWR spectrum. A criterion is derived which allows design of etched groove arrays with optimum bandwidth including the effects of the SSWR mode conversion. Suitable pass-band characteristics can be achieved by choice of etch groove depth.

RAPS-a rapid thermal processor simulation program

Rapid thermal processors using incoherent light illumination have become an important semiconductor processing tool for implantation anneal, oxidation, and alloying. The application in ohmic contact alloying, however, has to be made very cautiously, for the thin metal layer drastically changes the optical characteristics and thus the thermal response of the contact region. A rapid thermal processor simulation (RAPS) program has been developed to study the difference in temperature response during rapid thermal annealing for various substrate materials and the effect of thin metal coating the substrates with films. The results are correlated with experimental observations. The results suggest that users of commercial rapid thermal processors should be cautious about the temperature-sensor setup, the application area, and the interpretation of the measured temperature. >

’’Two‐port’’ magnetostatic wave resonators utilizing periodic metal reflective arrays

Single‐port and two‐port magnetostatic surface wave (MSSW) resonators have been demonstrated. These devices, based on etched groove array reflectors have shown high loaded Q’s (≳800) and clean resonance characteristics. A primary drawback lies in the fact that the reflective arrays must be accurately etched in the epitaxial YIG film, a complex and expensive process. This work reports the first use of etched metal reflector arrays to form resonant structures. A theoretical model is derived and applied to a two‐port model of the device. Simpler to fabricate, the structure shows Q’s of ∼600.

Magnetostatic Waves, Microwave SAW?

The continual demand for increased performance in modern communication and rader systems in terms of increased bandwidths and higher operating frequencies has led to investigation of novel techniques and technologies for analog signal processing. In particular, surface acoustic waves (SAW) have been extensively e xploited with great success to this end, but systems requiring bandwidths greater than 500 MHz and center frequencies greater than 1 GHz have pushed SAW devices near the practical physical limit of the technology. A novel technology promising increased bandwidths at higher frequencies is based on magnetostatic waves (MSW) propagating in epitaxial ferrite films such as Yttrium Iron Garnet (YIG). ploited in devices offering instantaneous bandwidths up to 2.2 GHz at microwave center frequencies from 0.5 to 20 GHz. This MSW signal processing technology, based on transversal filtering concepts used in SAW, has been under extensive investigation for the p ast 8 years. This paper will first discuss physical properties and limits o f magnetostatic waves, and consider similarities and differences with SAW. Next, the state of development of MSW technology in the United States and abroad will be summarized. Finally, some significant remaining problems for device application of MSW will be discussed followed by some projections for MSW technology limits.

Modeling and analysis of GaAs MESFETs considering the wave propagation effect

The effect of wave propagation along the electrodes of a GaAs MESFET is studied using a distributed circuit analysis technique. Each unit equivalent circuit consists of two subequivalent circuits, one modeling the transmission-line properties of the coupled gate and drain electrodes, and the other representing the traditional GaAs MESFET small-signal model. The distributed equivalent circuit is then analyzed using SUPER-COMPACT. The maximum available power gain or the maximum stable power gain of the device is calculated as a function of device width. It is shown that, for single-gate MESFETs over 100 mu m wide, the transmission-line properties of the electrodes have a significant effect on the transistor performance. The power gain also depends on where the input signal is fed and where the output signal is extracted.<<ETX>>

Current status of magnetostatic reflective array filters

The continual demand for increased performance in modern communication and radar systems in terms of increased bandwidths and higher operating frequencies has led to investigation of novel techniques and technologies for analog signal processing. In particular, surface acoustic waves (SAW) have been extensively exploited with great success to this end, but systems requiring bandwidths greater than 500 MHz and center frequencies greater than 1 GHz have pushed SAW devices near the practical physical limit of the technology. A novel technology promising increased bandwidths at higher frequencies is based on magnetostatic waves (MSW) propagating in epitaxial films such as Yttrium Iron Garnet (YIG). These waves can be exploited in devices offering instantaneous bandwidths up to 2.2 GHz at microwave center frequencies from 0.5 to 20 GHz.MSW signal processing technology, based on transversal filtering concepts has been under extensive investigation for the past 10 years. This paper reviews the work that has been done utilizing the MSW technology in conjunction with reflective arrays to achieve practical spectral amplitude and delay modification.