鈥?/div>
鹵
1.5 dB Output Flatness
鈥?Hermetic Thin-film
Construction
Description
HP VTO-8000 Series oscillators
use a silicon transistor chip as a
negative resistance oscillator. The
oscillation frequency is deter-
mined by a silicon abrupt varactor
diode acting as a voltage-variable
capacitor in a thin-film micro-
stripline resonator. This provides
extremely fast tuning speed,
limited primarily by the internal
impedance of the user-supplied
voltage driver. Fast settling is
another feature of the HP
VTO-8000 Series oscillators.
Typical settling times for the
VTO-8090 are <200 kHz within one
microsecond while the VTO-8950
settles to <2 MHz within two
microseconds referenced to ten
milliseconds. The VTO-8850
combines a bipolar transistor
oscillator with a GaAs FET buffer
stage. This GaAs FET buffer
isolates the oscillator from
variations in load impedance for
low frequency pulling, allows the
oscillator to run lighty-loaded for
low phase noise content and
provides +10 dBm of minimum
output power over the full tuning
range. The VTO-8000 Series
varactor-tuned oscillators are
packaged in TO-8 transistor cans
for simple installation in a
conventional 50-ohm micro-
stripline PC board. They are ideal
for most compact, lightweight
commercial and military equip-
ment designs. Test fixturing is
also available for lab bench test
applications. See the 鈥淭est
Fixtures for TO-8 Packages鈥?/div>
section for additional information
and outlines.
Pin Configuration
TO-8V
GROUND
+V
TUNE
2
1
3
4
RFOUT
+DC
VOLTAGE
CASE GROUND
Applications
Frequency agile systems, such as
digitally controlled receivers and
active jamming transmitters often
use externally linearized
varactor-tuned oscillators. HP
oscillators are monotonic making
external linearization easy using
analog (opamp) or digital
(EPROM) linearizing techniques.
The HP VTO Series has been
designed with a tuning input
bypass capacitance which is
sufficient to provide the neces-
sary RF filtering action yet as low
as possible to maximize
鈭哣/鈭員
characteristics for excellent
tuning speeds. Used in a phase
locked loop PLL circuit, a VTO
provides a receiver LO with
stability equivalent to the refer-
ence oscillator (usually crystal
controlled), yet variable in
discrete steps or continuously
depending on the PLL
configuration.
Another important aspect of VTOs
used in an LO application is their
power vs. frequency flatness
(鹵 1.5 dB). This assures that once a
receiver mixer is biased for best
dynamic range the local oscillator
drive will remain constant
throughout the tuning range
without complex leveling
circuitry.
9-23
5964-9815E
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