The second harmonic generation (SHG) coefficients dij of several corona-poled guest-host and side-chain polymers have been measured and studied over time using a new Maker Fringe analysis. The electro-optic coefficient r33 and scattering losses have also been measured in thin-film waveguides, on silicon and glass substrates, made from some of the polymers. Kleinman symmetry (d15=d31) was not valid for near-resonant SHG in these materials and d15/d31 was determined. Stable values of d33, for a fundamental of 1.064 μm, were as high as 40 pm/V for one of the side-chain polymers. Optical waveguide losses determined from scattering measurements were as low as 0.4 dB/cm at 1.06 μm.

No abstract

No abstract

This paper describes a vertically-polarized, unidirectional, frequency-independent antenna that utilizes its image to reduce its maximum height to 1/4 wavelength at its lowest operating frequency rather than the l/Z-wavelength dimension that has been necessary in other types of log periodic antennas. This relatively small dimension makes this antenna particularly desirable for use in the lower portion of the h-f spectrum as well as in other h-equency ranges where frequencyindependent operation must be coupled with small size. The kequency-independent properties of the antenna are produced by a unique arrangement of reactive elements which introduce additional degress of freedom in the design. Radiation pattern and phase center data are given as a function of the usual log periodic parameters. In addition, design data is given that allows the designer to control the antenna characteristic impedance and vswr by adjusting the additional parameters. Techniques that are necessary to ensure proper operation are discussed. Finally, the measured vswr of an antenna designed to operate from 4 to 20 mc is presented.

A computer-aided technique has been developed f o r t h e d e s i g n o f m a t c h i n g n e t w o r k s t h a t are a d a p t i v e , i n t h e s e n s e t h a t t h e n e t w o r k c a n b e c o n t r o l l e d by a change i n o n e o r more v o l t a g e s . T h e s e c o n t r o l v o l t a g e s are a u t o m a t i c a l l y v a r i e d w i t h a change i n t h e f r e q u e n c y o f o p e r a t i o n , o v e r w i d e b a n d w i d t h s , i n s u c h a manner t h a t t h e m a t c h between a complex impedance load and source can b e i m p r o v e d o v e r t h a t o b t a i n a b l e w i t h a f i x e d passive network. I n t r o d u c t i o n A computer-aided design technique has been developed at t h e U n i v e r s i t y o f I l l i n o i s f o r matchi n g n e t w o r k s i n t e n d e d f o r use between a load, whose complex impedance v a r i e s w i t h f r e q u e n c y , and a 50 ohm s o u r c e ( l ) ( 2 ) . T h i s t e c h n i q u e c a n b e a p p l i e d t o a c t i v e o r p a s s i v e n e t w o r k s , composed of e i t h e r lumped o r d i s t r i b u t e d e l e m e n t c o m p o n e n t s . The technique i s based upon c h a r a c t e r i z i n g t h e l o a d , t h e e l e m e n t s o f t h e m a t c h i n g n e t w o r k , a n d t h e s o u r c e i n terms o f t h e i r r e s p e c t i v e c a sc a d e d t r a n s f o r m a t i o n m a t r i c e s . A computer program p e r f o m t h e r e q u i r e d m a t r i x m u l t i p l i c a t i o n o n t h e s e c a s c a d e d s e c t i o n s t o o b t a i n a r e s u l t a n t o v e r a l l t r a n s f o r m a t i o n matrix. This transformat i o n m a t r i x i s c o n v e r t e d t o a s c a t t e r i n g m a t r i x t o o b t a i n t h e c o n v e n t i o n a l r e f l e c t i o n c o e f f i c i e n t s a n d t h e t r a n s m i s s i o n c o e f f i c i e n t t h a t c h a r a c t e ri z e s t h e t r a n s f e r of t h e s i g n a l f r o m t h e s o u r c e t o t h e l o a d . The design does not depend,upon developing a c i r c u i t o r m a t h e m a t i c a l model of t h e l o a d . It p r e s u m e s t h a t t h e c o m p l e x r e f l e c t i o n c o e f f i c i e n t of the load would be measured a t an adequate numb e r o f d i s c r e t e f r e q u e n c i e s o v e r t h e d e s i r e d b a n d . The s c a t t e r i n g p a r a m e t e r s o f all v a r i a b l e n e t w o r k elements will a l s o b e a v a i l a b l e , o r w i l l b e measured, a t these frequencies. These measured v a l u e s a r e t h e n u s e d i n t h e d e s i g n , a n d t h e o,vera l l t r a n s f e r c o e f f i c i e n t r e f e r r e d t o a b o v e is obt a i n e d a t e a c h o f t h e s e l e c t e d f r e q u e n c i e s o v e r t h e b a n d w i d t h o f i n t e r e s t . The computer program includes a modified version of Rosenbrock's minimization procedure(3) t o s e l e c t an "optimized" s e t o f e l e m e n t s f o r t h e matching network. The o p t i m i z a t i o n p r o c e d u r e c a n be set up i n t e r m s o f any one o...