W. Strauss

A new family of resonant rectifier circuits for high frequency DC-DC converter applications

A family of rectifiers suitable for operation at high frequencies is presented. These rectifiers use naturally occurring component parasitics to control diode switching thereby minimizing parasitic ringing and improving rectification efficiency by reducing the flow of harmonic currents. The input impedance of the resonant rectifier is linear, which makes possible an accurate adjustment of the rectifier to present the proper load impedance to an inverter. When a resonant rectifier is coupled to a resonant inverter in this manner, a fully resonant DC-to-DC converter is produced. With these circuits it is possible to achieve a very low input/output ripple and EMI since voltages and currents seen by the filters are confined to a very narrow frequency range compared to conventional squarewave converters.<<ETX>>

A resonant DC-to-DC converter operating at 22 megahertz

An experimental DC-to-DC converter prototype based on a zero-voltage switching, resonant circuit topology is described. The converter is suitable for mounting directly on a circuit card. The unit provides a regulated 5 V output at power levels up to 50 W with an input between 40 and 60 V. The switching frequency is between 20 and 24 MHz, depending on the input voltage and load. Differential input and output ripple and EMI are extremely low and somewhat difficult to measure. The converter prototype has been designed to demonstrate compatibility with a fully automated assembly process based on surface-mount technology. Solutions are presented to a number of problems, including MOSFET gate-drive and rectifier diode capacitance, that have seriously limited the performance of high-frequency converters operating with useful input and output voltages.<<ETX>>

Magnetoelastic Waves in Yttrium Iron Garnet

Magnetoeleastic pulses with variable echo time were observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc/sec with input power in the milliwatt range. At a fixed carrier frequency, pulses were observed for external magnetic fields ranging over several hundred oersted; characteristically the echo time increased with decreasing field. The carrier frequency‐magnetic field‐echo time behavior can be explained in terms of a θ=0 magnetoelastic disturbance traveling along the rod axis. It is launched at the position where ωc=γHi. The disturbance propagates along the rod axis to the nearer end‐face where it is reflected. On arrival back at the launch site, a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence. The experimental results can be understood in terms of a magnetoelastic wave packet with calculated travel time T=∫um−1dz≈∫us−1dz+∫ue−1dz, ...

Elastic and magnetoelastic waves in yttrium iron garnet

A discussion of plane elastic and magnetoelastic waves follows a statement of the linearized equations of motion of coupled spin and elastic waves. The dispersion equations of θ = 0 and θ = π/2 waves are examined in detail. A description of the generation and propagation of magnetoelastic waves in a nonuniform magnetic field prepares the way for a review of selected experiments which illustrate the transmission and attenuation characteristics of elastic and magnetoelastic waves in yttrium iron garnet. Experimental resuits are presented on (1) time-field behavior of θ = π/2 magnetoelastic waves, (2) time-field-frequency characteristics of θ = 0 magnetoelastic waves, (3) polarization reversal of θ = 0 magnetoelastic waves, (4) acoustic Faraday rotation, (5) Mc frequency standing magnetoelastic waves, and (6) loss measurements for elastic and magnetoelastic waves. Finally, some delay line applications of these waves are considered.

Internal Magnetic Field Analysis and Synthesis for Prescribed Magnetoelastic Delay Characteristics

A systematic procedure is given for synthesizing the internal magnetic field required to realize prescribed magnetoelastic delay characteristics. The method is based on the expression Tr = (2/c) {y+ω[γHi′(y, He)]−1} for the transit time of magnetoelastic waves in ferromagnetic insulators. Here Hi′(y, He) is the gradient of the internal magnetic field at the turning point, and He is the external magnetic field. Some necessary conditions for physical realizability are discussed and a delay‐bandwidth invariant is demonstrated. Field distributions are obtained having the characteristics: (a) ∂Tr/∂ω = 0, independent of ω at specified Hi(0, He), and (b) ∂Tr/∂ω = 0, independent of Hi(0, He) at specified ω. The last case is used as a basis for evaluating the bandwidth capabilities of magnetoelastic variable delay lines. Limitations on the bandwidth, delay variation, and delay distortion are discussed.Realization of a desired internal magnetic field is greatly simplified by a method for determining the field from ...

A uhf Delay Line Using Single‐Crystal Yttrium Iron Garnet

An investigation has been made to determine the properties of yttrium iron garnet at room temperature as a delay‐line transducer material. Preliminary results show a specific delay of 2.5 μ sec/cm and an attenuation of 0.4 dB/cm in the frequency range 0.5 to 1.0 Gc/sec. At low input power the insertion loss is constant whereas at high input power the output power is approximately constant; the high‐power behavior appears suitable for sonic limiting devices. A method has been found for suppression of unwanted echoes. Evidence from low power level insertion loss measurements indicates that it may be possible to construct a YIG delay line with a 3‐dB bandwidth greater than 100 Mc/sec and at the same time an insertion loss less than 60 dB.

Hall‐Effect Domain Detector

Electrical readout of digital information transported by closed domains in magnetically uniaxial platelets requires sensing flux changes of 1–10 pWb emanating from an area 2–25 μm in diameter. Using an n‐type epitaxial layer on a p‐type silicon substrate we have developed a beam‐leaded Hall‐effect device suitable for sensing domains in orthoferrites. In these materials the minimal domain diameter is approximately 25 μm and the flux density is typically 0.01 T. Some properties of the Hall‐effect detector are: active area ≈400 μm2, active thickness ≈1 μm, input and output resistance ≈1.5 kΩ, rated current Ir=8 mA, and risetime <50 nsec. Over the experimental range |B| ≤0.01 T and I≤Ir, the measured Hall voltage satisfied VH = (S0 ‐ S2I2)IB, where S0≈16 V/A·T and S2≈ 3×104 V/A3·T. In detecting orthoferrite domains were have obtained 0.5 mV signals. We discuss the design and fabrication, the electrical and mechanical characteristics, and the limitations of the device. Improved detector performance is possible...

Loss Associated with Magnetoelastic Waves in Yttrium Iron Garnet

Room‐temperature magnetoelastic waves have been observed in yttrium iron garnet from 1.6 to 8.5 Gc/sec. The minimum observed insertion loss, which includes conversion, transmission, and reconversion loss, was 15 dB at 1.6 Gc/sec; at 8.5 Gc/sec the smallest insertion loss was 46 dB. The transmission attenuation increases approximately linearly with frequency from about 6 to 20 dB/μsec over this frequency range. The experimentally observed conversion loss from electromagnetic to magnetoelastic energy ranges from 3 to 13 dB and is compared with theoretical values.

Characteristics of a Detection‐Propagation Structure for Bubble‐Domain Devices

A new chevron‐like structure which served both for detection and propagation of magnetic domains yielded 0.7‐mV sense signals from a 20‐μm period bubble device operated at 5‐mA detector current and 42‐Oe drive field rotating at 100 kHz. The sense signal — the voltage difference between the “one” and “zero” states — was superimposed on a 2.4‐mV peak‐to‐peak background. The detector‐propagation structure, made from the same 0.3‐μm thick permalloy as the propagation channel, consisted of a 51‐chevron column, the vertices of the chevrons being connected with a permalloy stripe. Typical resistance values were 60 Ω. The experimental results were obtained using an ion‐implanted film of Y0.9Eu1.9Yb0.2Al1.1Fe3.9O12. In comparison to thin‐film permalloy detectors operated at the same frequency the new structure provides not only more rugged devices but also superior signal voltage. Processing is simpler and faster. In addition, this design appears promising for high packing‐density applications because it permits s...

A permalloy detector for orthoferrite domains

A Permalloy detector using the pseudo or planar Hall effect has been developed for electrical readout of cylindrical domains in the orthoferrites. It consists of four gold leads attached to a Permalloy dot nominally 0.03 µm thick and 50 µm in diameter. Source resistance including gold leads was from 10 to 15 ohms. For 20-mA input current and domains approximately 60 µm in diameter, the detector yielded 0.8-mV signals in quasi-static operation. The speed capability of the Permalloy detector should be well above that of propagating domain devices.