Theory of Operation
3-2 2715 Spectrum Analyzer Service Manual
A25Ωresisto rw ithin the RF INPUT connector assembly is placed i n series
with the signal path. This transforms the connector to a 75 Ωimpedance for
external signal connections. All RF signal connectionswithin the 2715 (SMA
and SMB connectors) have a 50 Ωimpedance. RF type signal connections
between modules are made using double shielded coaxialcables, while DC type
signal connections are made using either multipin jacks on the Power Supply
board (Power Supply,Log Amplifier, Display Storage, Microprocessor, and
Center Frequency Control boards) or small ribbon cables.
The Main InterconnectDiagram at the front of the Diagrams section provides a
chart of the interconnectsystem in addition to what is shown in Figure 3--1.
Block diagrams showing more detail of these main sections appearbefore the
appropriate schematicstogether with another description. Circuit schematic
diagrams follow the Main InterconnectDiagram.
6/
RF IN
9kHz-1.8GHz
1
+70 dBmV MAX,
75 Ω100VDC
Max
2110MHz
1st
Converter
Attenuator
2.11−3.91 GHz2
+11dBm MIN
+14.5 dBm MAX
From1st LO Buffer
2nd
Converter
3rd
Converter
110 MHz
Variable
Resolution
Module
10 MHz
RF
Options
Reference
Oscillator
3/
RF Mother
Board
10/
10 MHz
--10dBm
Log
Amplifier
Display
Storage
Micro-
processor
Digital
Port
1stLO
Center
Frequency
Control
PowerSupply
with Deflection
System
FrontPanel
RearPanel
Controls&
Connector
2ndLO 2GHz100 GHz
COUNT10/
SWPSLOPE
Log
Amplifier
50/
Calibrator
(100 MHz/
--22dBm)
19KHz – 2.15 GHz for Option 50 and Option 75
22.11– 4.26 GHz for Option 50 and Option 75
Figure 3- 1: MainBlock Diagram