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HEWLETT-PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S
UBLISHED BY THE HEWLETT-PACKARD COMPANY, 1501 PAGE MILL ROAD, PALO ALTO, CALIFORNIA MAR. -APR., 1963
A New Microwave Modulator
ANEW modulator has been designed which since internally-generated noise is small. Mod
substantially simplifies the task of ampli ulation can be obtained from internal or exter
tude-modulating microwaves in the range nal pulses or square waves or from external
from 800 to 2400 megacycles. Basically, the sine waves. The internal circuits include delay
new modulator is an electrically-variable at and width circuits which are adjustable down
tenuator whose attenuation can be changed to 0.1 microsecond and which are jitter- free.
The new modulator operates by absorbing
Sff ALSO:
the microwave energy applied to it, as opposed
S e n s i n g m a g n e t i c f i e l d s , p . 7
The Smith Chart with negative Z, p. S to other solid-state modulators which reflect
N e w P r e f i x e s , p . 8 it. The instrument thus minimizes the difficul
ties associated with reflection. Reflections can,
very rapidly. Its properties include fast rise and for example, pull the frequency of tightly-
decay times of less than 20 nanoseconds, an on- coupled microwave oscillators and therefore
off ratio of 80 db, and the fact that it is solid- cause frequency modulation. Large reflections
state. It will handle up to one watt of micro can also permanently damage some sources
wave power and can also be used at low level, such as traveling-wave-tube amplifiers.
Fig. 1. New -hp- Model 8714A Modulator gives wide Fig. 2. Spectrogram taken of 2 usec RF
versatility in modulating waves in the 0.8