Sampling Phase Detectors
SPD Series
Features
3
Low Cost Design
Rugged, Modular, Hybrid Construction
Phase Locks VCO and DROs up to 20 GHz
Wide Frequency Range
Available for Oscillator Signal Levels from
–3 dBm to +13 dBm
Hermetic Package Available
Description
Alpha’s series of Sampling Phase Detectors (SPD’s)
consist of a hybrid assembly of an SRD comb
generator, coupling capacitors and microwave mixer
diodes. This module makes an inexpensive way of
phase locking a commercial VCO source to a low
frequency stable reference. Each part in the series is
optimized to operate in standard narrow band
commercial systems. All units handle reference
frequencies in the 50 to 500 MHz band. Component
selectionwithinAlphaallowsustominimizebeatnote
output.
circuit with shunt capacitors will result in larger
amplitude beat note signals.
The subharmonic mixer portion is the Schottky series
pair. Various drive levels can be used to tailor
intermodulation and beat note performance.
The basic operation of a SPD is when the reference
signal is fed into the SRD. This sets up a strong pulse,
rich in harmonics that is used to strobe the mixer
diodes on. The balanced mixer design converts the
sampled oscillator signal and matching harmonics into
an IF beat note. This signal can then be used in
feedback loop to correct tuning voltage on the VCO.
It is easiest to think of the SPD in its two constituent
forms; a comb generator and subharmonic mixer.
Typical applications include phase locking of
The comb generator portion consists of the external
reference, amplifier and impedance transformer. The
external circuit matches into the low impedance of the
SRD portion of the SPD. Careful attention to matching
by setting the right transformer ratio, detuning the
oscillators
in
TVRO,
VSAT,
DBS
and
telecommunications markets.
Leadless chip carriers and surface mount versions
are also available
Alpha Industries • [617] 935Ć5150 • Fax [617] 824Ć4579 • E-mail sales@alphaind.com • Visit our web site: www.alphaind.com
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