Test of optical rotation sensor and servo system - radio frequency electronic

Harrington, J. V.

English

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1 i 
CENTER FOR SPACE RESEARCH <-
MASSACHUSETTS INSTITUTE OF TECHNOLOGY 
https://ntrs.nasa.gov/search.jsp?R=19660002463 2020-03-16T22:20:32+00:00Z
NASA SUNBLAZER GRANT NASr-249 
F i f t h  Progress Report 
July 1 to September 3 0 ,  1965 
PR- 5 2 55-5 
MASSACHUSETTS INSTITUTE OF TECHNOLOGY 
-El? FOR SPACE JRESEAZCH 
F I F T H  QUARTERLY PROGRESS =PORT 
For t h e  Period 
July 1 to  September 3 0 ,  1965) 
on 
To The 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
O f f i c e  of G r a n t s  _?nd Research ConCracts 
Submitted by: J .  V .  Harrington 
Principal  Invest igator 
In t roduct ion  
During t h e  c u r r e n t  r e p o r t  period an optical  r o t a t i o n  sensor  
and se rvo  system has been tested and t h e  RF e l e c t r o n i c s  development 
has been p r imar i ly  concernec? wi th :  1. the  redesign of the  basic 
t r a n s m i t t e r  ou tput  power amplif ier :  2. i n v e s t i g a t i o n  of power 
d iv id ing  and combining c i r c u i t s  other  than L s e c t i o n  filters; 3. 
high power varactGr tests; 4. packaging of the above c i r c u i t s .  
I n v e s t i g a t i o n s  a l s o  continue i n  antenna development. 
1. Mechanical Desiqn and T e s t i n q  
The o p t i c a l  r o t a t i o n  sensor and se rvc  system has been tested 
during t h i s  per iod.  Major d i s tu rb ing  forces i n h e r e n t  i n  the  system 
have been i d e n t i f i e d .  A variable torque c c n t r o l  modif icat ion was 
i n s t a l l e d  which enable2 cbservat icn modes and opera t ing  techniques 
t o  be developed which produced? dynamic r e s u l t s  c o n s i s t e n t  w i t h  
theory.  
t h e  system t o  provide a means of s tudying the  e f f e c t s  of var ious  
l i b r a t i o n  damping devices  . 
There i s  a cont inuing e f f o r t  t o  improve t h e  s t a b i l i t y  of 
Active prepara t ions  for  v ib ra t ion ,  shock, acce le ra t ion  and 
thermal tests of t h e  pre-prototype assembly a r e  i n  progress ,  inc lu-  
ding the s e l e c t i o n  of test f a c i l i t i e s ,  monitoring devices ,  t h e  design 
and cons t ruc t ion  of s p e c i a l  f i x t u r e s  and machining of previous ly  
designed dummy e l e c t r o n i c s  p a r t s .  
A t e n t a t i v e  mechanical &sign of a series-stacked, phased 
d i p o l e  a r r a y  has been achieved, znd a search for a f a b r i c a t i n g  
vendor i s  being made. 
- 2 -  
Acquis i t ion  of infcrmation and communications w i t h  a u t h o r i t i e s  
on space-stable thermal f i n i s h e s  is being organized t o  enhance t h e  
s e l e c t i o n  of t h e  best a v a i l a b l e  su r face  f i n i s h e s  fo r  Sunblazer. 
2. R.F. Elec t ron ic s  
The cont inuing program cf high power t r a n s i s t o r  c i r c u i t  
eva lua t ion  has i nd ica t ed  a lower vol tage  t r m s i s t o r  should be used 
i n  t h e  next  model of t h e  Sunblazer t r a n s m i t t e r .  T h i s  u n i t  (a  type 
PT3611) is comparable ir, s t a b i l i t y ,  perfcrnance and package config- 
u r a t i o n  tc  the  older higher voltage u n i t s .  
performance (at 25v c o l l e c t o r  supply vol tage)  i s  60 w a t t s  RF power 
output  anti 75% collector ef f ic iency  c ? t  5& gzin.  S ince  the output  
impedance of t h e  power asapl i f ier  v a r i e s  as the square cf t h e  
c o l l e c t o r  vo l tage ,  a comp1eteX.y new amplif ier  design w a s  developed 
along w i t h  the system of power combiners and dividers. 
d i v i d e r  t h a t  w a s  r e a l i z e d  i s  t h e  lumped component equiva len t  of the  
microwave 3db hybrid. 
t o r i l y  Over a 30% bandwidth w i t h  20c?b i so la t im.  
Typical  100 M c  device 
The power 
Typically t h i s  circuit  performed satisfac- 
Another app l i ca t ion  of the  hybrid c i r c u i t  i s  i n  t he  area of 
h igh  power VHF pulse compression. 
used as a d i r e c t i o n a l  coupler  i n  t h e  VHF analog of the t r a v e l l i n g  
w a v e  resonator .  An experimental r e sona to r  was ccns t ruc t ed ,  b u t  
high circuit losses l i m i t  i t s  opera t ion .  
I n  t h i s  a p p l i c a t i o n ,  a hybrid is 
Bociluse of t h e  l o w  impedances a s soc ia t ed  w i t h  t h e  l o w  vcltnge 
power a m p l i f i e r ,  t r a n s m i t t e r  packaging has become more c r i t i c a l .  
T h i s  problem of r e a l i z i n g  microminiature RF c i r c u i t s  depends on 
. - 3 -  
I .  t h e  a v a i l a b i l i t y  of p r e c i s e  pr in ted  c i r c u i t  inductors .  As a pa r t i a l  
s o l u t i o n  t o  this problem a q u a n t i t a t i v e  design procedure is being 
developed for  t h e  cha rac t e r i zz t ion  of prj nted  c i r c u i t  R F  components. 
T h i s  procedure w i l l  be of value n o t  only f o r  the  power a m p l i f i e r  
design bu t  also i n  t h e  c r y s t a l  o s c i l l a t o r  and frequency m u l t i p l i e r  
c i r c u i t s  used i n  the  t r ansmi t t e r .  
A ten-dioee,  frequency t r ipler  c i r c u i t  is being packaged using 
p r i n t e d  c i r c u i t  techniques and niininture components. A breadboard 
vers ion  of t h i s  c i r c u i t  using f i v e  frequency tr iplers,  each w i t h  
t w o  diodes i n  pa ra j l e l ,  wes tested a t  t he  800 w a t t  level. Observed 
e f f i c i e n c y  was 50% and h igher  power parfcmnance w a s  l i m i t e d  5y t h e  
a v a i l a b l e  drive power. I t  i s  expecteC t h a t  t h i s  c i r c u i t  w i l l  handle 
a k i l o w a t t  s i n c e  each c i r c u i t  wzs tested! inCXviiuaily a t  the  200 
wat t  level. 
The basic t r a n s m i t t e r  crystal  oscil latGr i s  Leiny designed for 
maximum s t a b i l i t y .  The FET o s c i l l a t o r  d r i v e  power is  c c n t r o l l e d  by 
a feedback c i r c u i t .  The temperature environment w i l l  be maintained 
by a thermal sensor  and heater ilrrzngeinent, which i s  incomplete 
a t  t h i s  t i m e .  A frequency measurement system, inc luding  a VLF 
s t anda rd  has been put  i n t o  operntion i n  order  t o  c h a r a c t e r i z e  t h e  
d e v e l o p m n t a l  o s c i l l a t o r s .  
- 4 -  
3 .  Ant@,npa Development 
Severa l  prototype spacec ra f t  antennas a r e  being i n v e s t i g a t e d  
w i t h  respect t o  p a t t e r n  and impedance matching. 
and magnetic d ipo le  conf igura t icns  t h a t  are expectei! t o  y i e l d  
s e v e r a l  db af forward ga in  have been matched i n t o  50 ohm cable. 
A foreshortened he l ix  which usss the  solar ce l l  panel 38 a reflector 
is  under study. Experimental models of these antennas have been 
cons t ruc ted  and p a t t e r n  measurements will be taken during the  
next  report i n t e r v a l .  
Modified electric 


Study of a radio probe of the extended solar corona Fifth quarterly progress report, 1 Jul. - 30 Sep. 1965

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