Abstract A probe type high voltage attenuator for a pulse measuring system to provide an overall rise time of less than 50 picoseconds with a peak voltage capability of 20 kV. Attenuator perturbations at the 50 ohm impedance level are minimized by providing a high resistance in series with a lossy distributed transmission line. The reflection waves from the attenuator are absorbed by this lossy distributed transmission line minimizing perturbation of the source being measured. The attenuator is of a shielded type to minimize interference from extraneous fields. This invention is directed to an attenuator for use in the measurement of point voltage sources in electric circuits and in particular to an attenuator which produces minimum loading on high voltage sources in the measurement of fast rise time pulses. Numerous applications of subnanosecond high voltage generators, such as drivers for electro-optical streak camera and Pockels' Cell optical modulators require a reliable, polarity independent voltage measurement system. Subnanosecond high voltage attenuators which are used in conjunction with oscilloscopes have been developed and are suitable for measuring pulse amplitudes up to 5 kV. However, these attenuators are not suitable for fast laser light modulators and switching systems operating at voltages of the order of 15 kV, since they load the circuits if used in a measuring system for developmental diagnostics, or for the monitoring of the shape of ultrafast voltage pulses having subnanosecond rise and fall times. In addition, these attenuators or probes, if they are of the shield type, can cause circuit perturbation for point source voltage probing in 50 ohm systems. It is therefore an object of this invention to provide an attenuator for the measurement of high voltages at point sources. It is a further object of this invention to provide an attenuator for the measurement of high voltage pulses having fast rise and fall times. It is another object of this invention to provide an effective attenuator in the form of a probe. There and other objects are achieved in an attenuator which includes a resistor connected in series with a frequency dependent distributed resistance. The resistor is located within a coaxial connector used to connect the output of the attenuator to a coaxial line. The distributed resistance is mounted on a center wire which connects the afore mentioned resistor to the input terminal of the attenuator to maintain frequency independent attenuation and to absorb reflected energy from the attenuator thus preventing perturbation in the measured circuit.
An attenuator for measuring high voltage pulses from point voltage sources comprising: coaxial connector means having a first central conductor, for connecting the attenuator to a coaxial line; resistance means having one end connected to the central conductor, said resistance means being enclosed within a conducting shield to form a transmission line section; terminal means for connecting the attenuator to the point voltage source to be measured, said terminal means being connected to the resistance means by a second central conductor; frequency dependent distributed resistance means mounted on the second central conductor, said frequency independant resistance being substantially resistive at frequencies greater than 10 MHz, to maintain frequency independent attenuation of the attenuator and to absorb reflected energy from the attenuator; and ground conductor means fixed to the conducting shield for connecting the shield to the point voltage source ground.
Claim 2
Dependent Claim
140 words
An attenuator for measuring high voltage pulses from point voltage sources comprising: coaxial connector means having a first central conductor, for connecting the attenuator to a coaxial line; resistance means having one end connected to the central conductor, said resistance means being enclosed within a conducting shield to form a transmission line section; terminal means for connecting the attenuator to the point voltage source to be measured, said terminal means being connected to the resistance means by a second central conductor; frequency dependent distributed resistance means mounted on the second central conductor, said frequency independant resistance being substantially resistive at frequencies greater than 10 MHz, to maintain frequency independent attenuation of the attenuator and to absorb reflected energy from the attenuator; and ground conductor means fixed to the conducting shield for connecting the shield to the point voltage source ground.
Claim 3
Dependent Claim
32 words
An attenuator as claimed in claim 1 which further includes an insulating material means surrounding the second central conductor and the distributed resistance means between the conducting shield and the terminal means.
Claim 4
Dependent Claim
23 words
An attenuator as claimed in claim 2 wherein the insulating material means includes an insulating cylinder concentrically spaced about the second central conductor.
Claim 5
Dependent Claim
27 words
An attenuator as claimed in claim 3 wherein the conducter shield consists of a metal cylinder concentrically spaced about the first central conductor and the resistance means.
Claim 6
Dependent Claim
22 words
An attenuator as claimed in claim 4 which further includes a dielectric fluid located within the insulating cylinder and the metal cylinder.
Claim 7
Dependent Claim
25 words
An attenuator as claimed in claim 1 wherein the distributed resistance means consists of a series of ferrite beads mounted on the second central conductor.
Claim 8
Dependent Claim
17 words
An attenuator as claimed in claim 6 wherein the resistance means consists of a carbon composition resistor.