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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

Vol. 15, No. 12

lUBLISHED BY THE HEWLETT-PACKARD COMPANY, 1501 PAGE MILL ROAD, PALO ALTO, CALIFORNIA AUGUST, 1964




A New Microwave Spectrum Analyzer
A new spectrum analyzer displays up to 2,000 Mega
cycles of the spectrum at a time for RFI checking, spec
trum surveillance, and other wide-band investigations.


IVliCROWAVE spectrum analyzers are swept-fre-
quency receivers with visual display. The basic
function of a spectrum analyzer is to plot input
signal amplitude as a function of frequency while
the analyzer automatically tunes through a
selected range of frequencies.
Spectrum analyzers are potentially useful in
the laboratory as well as in the field because they
provide quantitative information about several
signals simultaneously. For instance, they facili
tate adjustment of devices that operate with
several different frequencies at the same time,
such as parametric amplifiers. A spectrum ana
lyzer connected to an antenna can display a plot
of all detectable electromagnetic radiations over
a selected frequency band, indicate the relative
strength of each signal, and show individual fre
Fig. 1. Hewlett-Packard Model 8551A/851A Microwave quency components of any one of the signals to
Spectrum Analyzer enables evaluation of signals widely
separated both in amplitude and frequency. Analyzer provide useful information on sideband structure.
here displays harmonic and spurious outputs of fre It has not always been possible, however, to
quency doubter throughout range from 10 Me to above 10
Gc. Doubler generates 3800 Me output in response to make measurements with spectrum analyzers in
1900 Me input and Analyzer clearly shows how mis- a simple, straightforward manner. Broad-band
tuning can cause certain diodes to produce non-har-
monically related parametric oscillations. analyzers often include image responses and a
Fig. 2. Wide measurement range of
new