Alfred R. Koelle

Short-range radio-telemetry for electronic identification, using modulated RF backscatter

An electronic identification system which uses modulated backscatter from an RF beam-powered tag is described. A subcarrier is used in the return signal format to allow separation from the background clutter and to allow use of a novel method to avoid RF phase problems.

Doppler radar with cooperative target measures to zero velocity and senses the direction of motion

A Doppler radar system is described which uses a modulated scatterer as a cooperative target. The amplitude modulation sidebands in the return signal allow effective discrimination against background reflections and enable measurement to zero velocity and sensing of the direction of motion.

Crossing High-Voltage Inerfaces with Large Bandwidth Signals

In connection with a 50-kV modulator development, three methods of crossing the high-voltage interfaces at a 1-MHz bandwidth are being developed. The first system uses a pulse transformer driven from ground by solid-state electronics. The transformer requires special design to obtain a very short (? 500 ns) risetime combined with the ability to maintain a 1000-?s, 200-V pulse with negligible droop. The second system is an amplitude-modulated rf carrier operating at 5 MHz. The interface is crossed with an untuned toroidal rf transformer. Increased bandwidth is obtained by placing the carrier at the lower edge of the passband and operating in the single sideband full carrier mode. The signal is demodulated with a balanced diode detector having a peak output of +200 V and good linearity. The third method uses a Hewlett-Packard HPA-4309 electro-optical isolator with solid-state amplifier on the high-voltage side. The intrinsic bandwidth of the isolator unit is ~10 MHz. With suitable amplifiers to bring the pulse up to +200-V peak, the bandwidth is ~2 MHz. Because the interface is crossed at a very low level reaching an adequate signal-to-noise ratio has presented special problems. All three systems should be useful on a wide variety of high-voltage laboratory machines; each has special advantages depending on the particular application.

The los Alamos Proton Storage Ring (PSR) Injection Deflector System

We describe a pulsed magnetic deflector system planned for the injection system of the PSR. Two sets of magnets, appropriately placed in the optical systems of both the ring and the injection transport line, provide control of the rate at which particles are injected into a given portion of transverse phase space and limit the interaction of stored beam with the injection stripping foil. High-current modulators that produce relatively complex waveforms are required for this purpose. Solid-state drivers using direct feedback to produce the necessary waveforms are discussed as replacements for the more conventional high-voltage tube technology.

Pulsed Air-Core Deflector-Magnet Design Parameters

The response of air-core magnets to pulsed excitation is dependent on the pulse frequency spectrum because of fields produced by induced currents in the magnet structure. We discuss this phenomenon quantitatively in terms of magnet performance optimization.