Filter
Top Products
Low-Pass
Filter
Refer to function block AB of A4 Log Amplifier Schematic Diagram (sheet 4 of 4) in the
HP 8560 E-Series Spectrum Analyzer Component Level Information.
1. Connect a DVM positive probe to A4J9 pin 4.
2. On the HP 85623 spectrum analyzer, press (CAL).
3.
Press FULL IF ADJUST. Observe the DVM reading between the displayed messages
IF ADJUSTSTATUS:
300
kHz
RBW
and
IF ADJUST STATUS: 3
kHz
RBW.
Duringthistime
period, the voltage should be within a 2 to 10 Vdc range.
4. Observe the DVM reading while
IF ADJUST STATUS: AMPLITUDE
is displayed. The reading
should be within the 2 to 10 Vdc range.
5. If the DVM reading is outside the range in step 3 but inside the range in step 4, suspect
one of the reactive components of the filter.
Sweep
Generator
Refer to function block Z of A4 Log Amplifier Schematic Diagram (sheet 4 of 4) in the
HP 8560 E-Series Spectrum Analyzer Component Level Information.
A properly operating sweep generator generates a series of negative-going parabolas. Before
the sweep, switches A4U802C and A4U802D turn on, shorting A4C802 and A4C801 (the
output is at 0 volts). These switches open to start the sweep. The output of A4U804A, pin 1,
is 0.35 V to 10 V, depending on the sweep width selected by A4U802A and A4U803A. This
voltage appears across A4R801. Capacitor A4C801 integrates the current through A4R801.
The output of A4U804B is a straight, negative-going ramp. Capacitor A4C802 and resistor
A4R802 integrate the output of A4U804A which starts a negative ramp (A4U804C) at the
beginning of the sweep. The ramp from A4U804B is added to the current in A4R802 via
A4U803B. Integrating this ramp results in the parabolic output waveform.
AM/FM
Demodulation,
Audio
Amplifier,
and
Speaker
Refer to function blocks R,
S,
and T of A4 Log Amplifier Schematic (sheet 4 of 4) Diagram in
the HP 8560 E-Series Spectrum Analyzer Component Level Information.
If the audio circuits are not functioning use the following procedure to isolate the problem:
1. Set an AM signal generator controls as follows:
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..lOOMHz
Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -6
dBm
Modulation type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80% AM
Modulationfrequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 Hz
2. Set the HP 85623 spectrum analyzer controls as follows:
Center frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..lOO MHz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz
Sweep time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50ms
Reference level
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
dBm
Resolution bandwidth
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 kHz
Amplitude scale
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LINEAR
9-38 IF Section