Model 8340A - service
Table 80-3.
Instrument Frequency vs. YO Frequency
Band
Instrument Frequency
YO Frequency
Heterodyne 0
0.01 to 2.5 GHz
3.71 to 6.2 GHz
Multiply
1
2.3 to 7.0 GHz*
2.3 to 7.0 GHz
Multiply
2
7.0 to 13.5 GHz
3.5 to 6.75 GHz
Multiply
3
13.5 to 20.0 GHz
4.5 to 6.67 GHz
Multiply
4
20.0 to 26.5 GHz
5.0 to 6.625 GHz
*
Refer to Section I, Figure 1 in Table 1-1, Specifications, for
specific bandcross information versus swept mode used.
It is because of this harmonic operation of the 8340A that
bandcrossings are necessary. At each crossing, VSWP resets to
zero and the YO is phase-locked to the appropriate frequency for
the start of the next band. The result is that in a multi-band
sweep the Marker Ramp is a monotonic ramp which pauses for
bandcrossings, and VSWP is a series of ramps each starting at
zero volts. The slope of any particular ramp depends upon the YO
harmonic being used in that band. Figure 8D-17 shows the basic
characteristics of the Marker Ramp and VSWP for a full-band, 10
MHz to 26.5 GHz sweep.
The MKR RMP is a
O
to +10 volt ramp that is used as the reference
for all sweep events. It is related to the Sweep Out, but since
there is other circuitry between the Ramp Generator (Block
K)
and
Sweep Out, the Ramp Generator output is called Marker Ramp. On
the A58 Sweep Generator board, the Marker Ramp is fed through the
summing Amplifier (Block
L)
and sweep Width DAC (Block
M)
to give
the .20-30 SWP ramp that sweeps the 20-30 Loop for narrow
instrument sweeps (YO sweep width less than 5 MHz). This voltage
is then run through the sweep Width Range Attenuator (Block
N)
to
give VSWP. In addition, the Marker Ramp goes to the A57
Marker/Bandcross board where it is buffered and sent to the SWEEP
OUT (X-axis) ports on the front and rear panels. Finally, the A57
Marker/Bandcross board uses the Marker Ramp to determine when all
sweep events (markers, bandcrossings and ends of sweeps) are to
occur.
As mentioned before, the Marker Ramp is always a
O
to +10 volt
ramp. In a single band sweep, the voltage goes linearly from 0 to
+10 volts in the selected sweep time. In a multi-band sweep, the
voltage is a segmented ramp where the linear ramp portions
correspond to the particular bands being swept and the flat
portions correspond to the time necessary to re-phase-lock the
instrument for the next band to be swept. In the multi-band case
the sum of the times for the various linear ramp portions will
8�358
Scans by HB9HCA and HB9FSX
Содержание 8340A
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