8
Subject to change without notice
1 . B a s i c s
from the CPU Board. The output signal is then fed directly via
2 SMB connectors to the TG attenuator.
CPU Board
The CPU Board contains most of the digital control circuitry,
the TCXO reference
30
, the complete digital signal processing
circuits, the digital sweep generator
34
and the DDS refe-
rence generator for the 1st LO
33
as well as control circuitry
for analog control signals to TG Board
42
, XYZ Board
36
+
37
and the CRT
41
. The CPU Board also communicates with the
KEY Board to obtain input from the user. In addition, the serial
communication for the RS-232 interface is provided for fl exible
data transfer from and control of the HM5014-2. Also located
on the CPU Board is the ASIC for the readout of the spectrum
analyzer, also providing the display data given to the D/A con-
verters
37
for X and Y signals to CRT.
The video signal from the IF Unit enters the CPU Board where
ist is digitized and stored in the signal RAM
39
. Now the raw
data is shifted to the correct position of the reference level
setting and also the B-A representation is calculated using
the data stored in the signal RAM. The main CPU
35
then pro-
cesses the data, and provides it to the readout ASIC so it can
be displayed on the CRT after D/A conversion
37
and the dot
join circuit – an integrator for best interpolation of adjacent
sample representations.
The CPU Board also contains the highly stable reference oscil-
lator for the entire unit, a 96 MHz TCXO
30
used for several pur-
poses throughout the unit. Its main use is the clocking of the
DDS generator
33
on the CPU Board, which is the reference
for the 1st LO
4
on RFA Board. Derived from these 96 MHz are
also the 2 reference signals for the RFB and TG Boards as well
as the 48 MHz test signal provided on the front panel (after a
levelling stage)
31
+
32
.
The digital sweep generator controls the sweep time accor-
ding to the setting by the user for maintaining best signal and
amplitude representation.
The main CPU
35
on the CPU Board is quite straightforward,
using an EPROM for storing the fi rmware and a RAM for storing
the necessary data, as well as providing control and commu-
nication for the entire spectrum analyzer and external devices
via serial interface.
XYZ Board
The XYZ Board is fi xed to the back end of the CRT via the CRT
socket. It contains circuits for the X
50
and Y
52
signal defl ection
amplifi ers. Also present is the unblanking circuit
51
controlling
the intensity of the CRT and its focus
53
.
STOP
CAUTION:
A part of the XYZ Board is operated at a voltage of
2000 Volts.
KEY Board
The KEY Board consists of a microcontroller (keyboard con-
troller
23
) to control the reading of keys
24
and illumination of
the LEDs on the KEY Board. Also present are the audio signal
amplifi er
25
which converts the video signal to an audio signal
of the desired amplitude, and the probe power supply
26
for
externally connected probes. The control outputs to both atte-
nuators are also generated by the keyboard controller
23
. The
input from the rotary encoder is processed by the keyboard
controller.
The microcontroller is in constant communication with the
main CPU
35
of the CPU Board.
PS Board
The PS Board comprises a switchmode power supply capable
of accepting input voltages from 105 to 253 Volts AC providing
all the voltages needed inside the instrument, some with a
highly stable linear regulating circuit.
CRT Module
The CRT Module consists of the CRT enveloped in mu-metal
for immunity to external magnetic fi elds. The mu-metal loses
its capabilities when bent after treatment and should not be
removed from the CRT.
STOP
CAUTION:
The CRT contains a high vacuum inside and may
implode if handled or treated improperly.
Interface module
The interface module is a RS-232 converter module between
the internal logic level and the logic levels demanded by the
RS-232 standard. It is located on the upper rear side of the
instrument.
