Advertisement
Page 4
86908
OSCILLOSCOPE
SWEEP
·~c
~
®HO~IZ
V~T
(,)
l
I
SWEEP
J
I
L
DETECTORS
r-v
'-1i
--~
1.::::
=
TEST DEVICE
DUAL
'
0
DIRECTIONAL
'
SHORT
COUPLER
Figure 4. Coaxial reflectometer.
Internal leveling is available as Option 001 on most RF
units operating below 12.4 GHz. The directional coupler
and detector of Figure 3 are located within the RF unit and
the output of the coupler becomes the output of the sweep
oscillator. Internally leveled units are useful in less critical
applications in which transmission variations between os-
cillator and test point are not significant or a package free
of external elements is desired.
Modulation
All modulation functions are selected by pushbutton and
can be used simultaneously. Included is internal square-
wave modulation, with a range of 950 to 1050 Hz, plus
external AM and FM. The external AM input is de-coupled
to permit de control of amplitude and can be utilized even
during leveled operation. The external FM input is also de-
coupled to permit external frequency programming, and
the response to a full-band step change is typically less than
2 milliseconds. The frequency response to sinusoidal FM
is 150 Hz for full-band swing. Maximum swing decreases
to about 1% of the band at 20 kHz. Greater-than-specified
deviations at modulating signals above 150 Hz can be ob-
tained at a sacrifice in linearity.
Swept Systems Applications
The range of application for swept-frequency techniques
covers all microwave measurement areas: impedance, attenu-
-hp- 1416A
-hp-
141 A
Swept Frequency
Oscilloscope
Indicator
0
-hp-86908
Sweep
Oscillator
Device
under
test
~~~t~~~~~.~
-hp-
817A
-hp- 907A
Sliding Load
Figure 5. The 817 A Swept Slotted Line system provides
inexpensive and precise SWR measurement from 1.8 to 18
GHz.
Model8690B
ation, power, frequency, etc. The most widely used swept-
frequency system has been the reflectometer, which, in
measuring return loss and SWR, provides impedance infor-
mation. Figure 4 illustrates the basic reflectometer setup in
coax; the waveguide setup is similar. Above 4 GHz, the low
directivity of coaxial directional couplers has been a serious
limitation in the coaxial reflectometer. Hewlett-Packard,
therefore, recently developed the Model 817 A Swept Slot-
ted Line system capable of measuring very low standing-
wave ratios with a high degree of accuracy from 1.8 to 18
GHz. The design simplicity of the 817 A Swept Slotted
Line system shown in Figure 5 provides broadband, pre-
cision, coaxial SWR measurements at roughly a third of the
cost of previously available hardware.
Frequency response, whether in the form of attenuation
in a passive device or gain in an active device, is another
parameter readily measured on a swept-frequency basis. A
typical measurement setup in waveguide is shown in Fig-
ure 6.
The new Hewlett-Packard Model 8410A Network Ana-
lyzer provides one simple system capable of measuring both
amplitude and phase of all network parameters from 110
MHz to 12.4 GHz. The 8410A Network Analyzer is shown
in Figure 7, with the HP 8690B Sweep Oscillator measuring
both the amplitude and phase transmission characteristics of
a YIG filter. The 8410A is capable of measuring phase,
gain, loss, impedance, admittance, reflection coefficient, and
angle. Phase and amplitude output data may be obtained
either from a linear meter readout or in polar form with the
HP 8414A Polar Display.
The HP sweeper has been designed to be especially com-
patible with the advanced 8410A Network Analyzer system.
The 8690B supplies a sweep reference voltage output
which is used to synchronize the 8410A sampling phase-
lock oscillator permitting phase-lock operation at the fastest
sweep speeds, providing a flicker-free oscilloscope readout.
The 8690B Oscillator has been designed to provide a de-
layed sweep start-up, enabling the 8410A Network Analyzer
system to phase-lock before the initiation of the sweep. This
delayed sweep start-up capability is also especially useful
86908
OSCILLOSCOPE
»m "'
[;J
I
\:ili:L, ~"'
t---~1
SWEEP
r
t-l
:J]_DETECTOR
i ·~~1::'·-x}""u~,"
i
COUPLER
I
I
TEST
I
!.
T
DEVICE
I
r-x--
~
' - 1
10/20D8
1------p.--.--~
DIRECTIONAL
DETECTOR
COUPLER
Figure 6. Frequency response setup.
Advertisement
