HP 8924E, Сборка

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59
Chapter 1, Introduction
Theory of Operation
N:\mkt\MANUALS\HP8924C\ALR\intro.fb
Instrument
Frequency
References
Most of the Test Set’s internal oscillators and counters are phase-locked to the
signal input from the rear-panel REF INPUT port. This signal is usually the output
of the 10 MHz Oven Oscillator (A38) assembly, also available on the rear-panel.
The Reference Assembly (A27) is internally connected to the CDMA Reference
(A29), which is connected to the external reference. The CDMA Reference
provides the clocks for the CDMA assemblies, the AWGN (Additive White
Gaussian Noise) source, and the reference for the Reference Assembly. The
Reference Assembly provides the references for the analog assemblies.
If the message“
Reference unlocked, check reference connection
and frequency
” is displayed on the top of the Test Set’s screen, verify that a
good BNC cable (or factory jumper) is connected between the REF INPUT and 10
MHz OVEN OUT ports. If the message is still displayed, make sure the
External Reference
control on the CONFIGURE screen is set to
10.0000 MHz
, and use a frequency counter to verify the presence and frequency
of the 10 MHz Oven’s Output signal. If an external reference is used, verify that
the reference frequency matches the
External Reference
setting (±10 ppm),
and that the level is at 0 dbm (±3 dB).
Figure 1 Reference Signal Generation
RF Analysis
RF signals connected to the front panel RF IN/OUT port or ANTENNA IN port
go to the Input Assembly (A5) . The signal level and RF frequency are measured,
and the level is adjusted using fixed step and variable attenuators.
OVER-POWER
DAMAGE!
The ANTENNA IN connector is only used for very low level signals (200 mW or
less), and cannot be used for Transmitter (TX) Power measurements. Exceeding
this limit may destroy this assembly! The RF IN/OUT connector is used to
measure direct mobile transmitter power up to 6.0 Watts
.
10MHz Oven
Oscillator
CDMA Reference (A29)
CDMA Clocks to the Receive and Optional DSP Assemblies, Protoco
Cell Site Digital assemblies, Cell Site Analog Assembly,
and
Rear-Panel
EVEN SEC
Input
External CDMA Timing
Reference Input
REF INPUT
Rear-Panel
10 MHz REF
OUTPUT
(A38)
rear panel.
1 MHz to Receiver Synthesizer
1 MHz to Signal Generator Synthesize
1 GHz to Output Assembly
20 MHz to Frequency Counter
20 MHz to Spectrum Analyzer
500 MHz to Receiver
10 MHz to Receiver (SSB and FM Dem
Reference Assembly
10 MHz
10 MHz
LO/IF/DEMOD Assembly (A31)
Ex
te
rn
al
J
u
mp
er
10 MHz
(A27)
Processor,