pulsed 500‐mhz arbitrary waveform generator
TRANSCRIPT
Pulsed 500MHz arbitrary waveform generatorR. J. Adler and K. O. Busby Citation: Rev. Sci. Instrum. 59, 646 (1988); doi: 10.1063/1.1139850 View online: http://dx.doi.org/10.1063/1.1139850 View Table of Contents: http://rsi.aip.org/resource/1/RSINAK/v59/i4 Published by the American Institute of Physics. Related ArticlesInfluence of thermal fluctuations on the emission linewidth in MgO-based spin transfer oscillators Appl. Phys. Lett. 101, 062407 (2012) A compact, low jitter, nanosecond rise time, high voltage pulse generator with variable amplitude Rev. Sci. Instrum. 83, 075112 (2012) High power microwave generation from the low-impedance transit-time oscillator without foils Phys. Plasmas 19, 072106 (2012) Frequency multiplying oscillator with an electron beam accelerated in a drift space Appl. Phys. Lett. 101, 013507 (2012) Generation of pure phase and amplitude-modulated signals at microwave frequencies Rev. Sci. Instrum. 83, 064705 (2012) Additional information on Rev. Sci. Instrum.Journal Homepage: http://rsi.aip.org Journal Information: http://rsi.aip.org/about/about_the_journal Top downloads: http://rsi.aip.org/features/most_downloaded Information for Authors: http://rsi.aip.org/authors
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Pulsed SOO-MHz arbitrary waveform generator R. J. Adiera ) and K. O. Busby
Mission Research Corporation, 1720 Randolph Road SE, Albuquerque, New Mexico 87106
(Received 2 September 1987; accepted for publication 9 November 1987)
Unipolar and bipolar arbitrary waveform generators (A WGs) are described. Starting from a single 2-ns-wide pulse, a train of2-ns-wide, variable amplitude pulses are foroled by splitting the initial pulse into multiple, equal amplitude pulses and then delaying and attenuating each of these pulses separately. By choosing the proper attenuation (pulse amplitudes) and adding the train of pulses together, an arbitrary unipolar waveform can be constructed. With the addition of a second pulse generator of opposite polarity, an arbitrary bipolar waveform can be generated.
INTRODUCTION
A variety of scientific projects require the generation of specific, tailored waveforms for applications such as the centering or aiming of charged particle beams in accelerators, [ and compensating for instabilities in fusion devices.2 An A WG system would consist of: (1) sensors to detect the beam or plasma location or the magnitude and phase of instabilities, (2) a computer algorithm to predict the corrective waveforms (or perturbation) to center the beam or to counter the instability, (3) a computer-controlled A WG to produce the corrective waveform, (4) an amplifier to increase the waveform amplitude to the desired level, and (5) an antenna structure to induce the corrective perturbations into the beam or plasma.
In this paper, we present a simple, reliable, 2 ns per point (5OC-MHz) A WG design based on techniques which can be scaled to 0.25 ns per point using currently available components. Current technology is limited to 200 MHz.3
I
I ANZAC DS-:lG9
1 ~ AVTECH 1 ns_ 8 WAY
PULSE GEN. -t POWER
AVH P =J=. SPLiTTER
I
FIG. 1. Arbitrary waveform generator.
L AN UNIPOLAR ARBITRARY WAVEfORM GENERATOR
Our approach is shown in Fig. 1. The initial pulse generated by an Avantech A VH-P pulse generator is split in eight, 2-ns-wide, equal amplitude parallel pulses by an Anzac DS-309 power splitter. The generator pulse is approximately triangular. Each split line is delayed by 2 ill ns. The pulses are then fed through Mini-Circuits P AS-I electronic attenuators, and are attenuated by amounts determined by external potentiometer controls. When summed together through an Anzac DS-309 power adder, the resultant pulse is a train of 2-ns duration pulses.
With all attenuators set to zero attenuation, the waveform at the combiner output is shown in Fig. 2. To zero order, this waveform is a square wave, as expected. \VavefOlms with attenuator number six set to maximum attenuation, and then with attenuator numbers four and five set to maximum attenuation are shown in Figs. 3 and 4. Although
2 'l5 ATTENUATOR #1
~ L L 0-15 V ij ns ATTENUATOR #2
~ I l ~ C-15 V
6 ns ATTENUATOR k3
,,\: I l 0-15 V 8 ns ATTENUATOR #4
* 1 l 0--15 V I I ANZAC D5-309~1
POWER COMBINER
1 n !IS
~ 12 ns
~ 14 ns
~ 16 ns,
DELAY
~
ATTENUATOR #'i
I I ~
ATTENUATOR #6
I l ATTENUATOR #7
.---,
I l ATTENUATOR #8
I L
ELECTRON [CALLY
CONTROLLED
ATTENUATORS
I I 0-15 V
o 15 V
i o 15 V
015V'i,15V
~\ \.. CONTROLS
646 Rev. Scl.lnstrum. 59 (4), April 1988 0034-6748/88/040646·03$01.30 © 1988 American Institute of Physics 646
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FIG. 2. Generator output with all attenuators set to [) dB. The waveform is inverted.
FIG. 3. Attenuator number six set to maximum attenuation, all other attenuators set to [) dB.
FIG. 4. Attenuators numbers four and five set to maximum attenuation with all others set to 0 dB.
641 Rev. Sci. (nstrum., Vol. 59, No.4, April 1988
FIG. 5. Arbitrary waveform triangular pulse.
the rise times of the waveforms are somewhat distorted by the lOO-MHz bandwidth of the recording oscilloscope, the oscillations are due to the shape and spacing of the generator pulses. Note that the pre- and postpulse amplitudes (i.e., lack of a flat base line) are due to the low amplitude pre- and postpulse output of the pulse generator. Since these outputs are of long (tens of ns) duration, they add to a measurable value, The waveforms do demonstrate the rapid voltage variations which can be achieved, Another example of the versatility of the A WG-an asymmetric triangular waveform-is shown in Fig. 5.
II. A BiPOLAR ARBITRARY WAVEFORM GENERATOR
A simple technique for adapting this device to bipolar operation is to add an opposite polarity square pulse to the output of the unipolar A WG. An example of the output is shown in Fig. 6. The jitter of the A WG is less than 0,5 ns.
FIG. 6. A bipolar arbitrary waveform generator output.
Waveform generator 647
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III. SUMMARY
Unipolar and bipolar A WGs have been demonstrated. The technique of dividing a single pulse into multiple, equal amplitude pulses which are separately attenuated and delayed and then added together has been used to construct various waveforms. An advantage of the technique is that jitter is reduced because only one (unipolar A WG) to two (bipolar A WG) pulse generators are required. The frequency of A WGs is limited by the bandwidth of available addersisplitters and attenuators and the pulse width of available pulse generators. Ideally, the output of the pulse generators would be square waveforms. The A WGs can be computer controlled by command triggering the pulse generators and installing programmable attenuators.
643 Rev. ScLlnstrum., Vol. 59, No.4, April 1938
ACKNOWLEDGMENTS
The authors gratefully acknowledge the technical services of Daniel J. Andazola. The work was supported by the Naval Surface Weapons Center under Contract No. N60921-85-C-0211.
a) Present address: Pulse Sciences Incorporated, 5330 Derry Avenue, Suite J, Agoura Hills, California 91301.
'See, for example, J. Golden, J. Pasour, D. E. Pershing, K. Smith, F. Mako, S. Slinkt:r. F. Mora, N. Orrick, R. Altes, A. Flifid, P. Champney. and C. A. Kapctanakos, IEEE Trans. N uc!. Sci. NS-30, 2114 (1983) or Y. Cha, E. Crosbie. T. Khoe, R. Kustom, R. Martin, J. Norem, W. Praeg, K. Thompson, and G. Whitficld, IEEE Trans. Nue!. Sci. NS-30, 2117 (1983).
lD. A. Baker et al., Bull. Am. Phys. Soc. 31,1546 (1986). 'See, fiJI example, Hewlett-Packard 1986 catalog, p. 457.
Waveform generator 648
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