Agilent Technologies 8935 Series, Руководство пользователя

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170 Chapter 7
Periodic Adjustments
IQ Calibration Program Description
IQ Calibration Program Description
The goal of IQ Calibration is to minimize the carrier feedthrough while
maximizing the Rho of the IQ signal. There are four DACs involved in
this adjustment:
• buffModN_I_DC_offset_DAC,
• buffModN_Q_DC_offset DAC,
• buffModN_signal_delta_DAC,
• genRef_IQ_quad_DAC
The I and Q dc offset DACs and the signal delta DAC are on the A2A34
Data Buffer assembly and the Quad DAC is on the A2A100 CDMA
Generator Reference. These DACs can be accessed in the list of Latches
on the SERVICE screen. All the DACs are initially set to 127 before
starting the calibration adjustment, and the calibration is carried out at
several equally spaced frequencies between 800 and 1000 MHz.
The instrument is set into a CDMA loopback mode and the calibration
is carried out by first adjusting the I and Q dc offset DACs while
monitoring the carrier feedthrough (CFT). Both CFT and rho are
measured by the A2A36 Receive DSP. Once the CFT is minimized
(through an iterative process), the signal delta and the quad DACs are
adjusted while monitoring rho. When rho is maximized (again through
an iterative process), the calibration adjustment is complete. At power
down, each DAC setting at each frequency is downloaded to the
calibration ROM on the A2A31 Controller assembly.
Figure 7-5 IQ Calibration
servsrn1.eps
SOFTWARE MENU Screen
SOFTWARE MENU
Description:
Launches disgnostic and calibration programs.
Continue
1
2
4
Run Test
Help
SOFTWARE MENU
Library:
[NO LIB] Program:
ROM
CUSTOMIZE TEST PROCEDURE:
Channel Information
Test Parameters
Order of Tests
Pass/Fail Limits
Save/Delete Procedure
SET UP TEST SET:
Execution Cond
External Devices
Printer Setup
IBASIC Cntrl
LOAD TEST PROCEDURE:
Select Procedure Location:
ROM
Select Procedure Filename:
SERVICE4
Exec
Cnfg
Print
IBASIC Freq
Parm
Seqn
Spec
Proc
iqcal1.eps
SERVICE MENU
1
2
3
4
5
Help
Exit
Functional Diagnostics
AF Diagnostics
RF Diagnostics
CDMA Diagnostics
Edit RF Diagnostic Limits
Periodic Calibration
IQ Calibration
Eb/No Calibration
=>
Move pointer to the desired program using the
knob then press the knob. Press HELP for
information on the tests. Press EXIT to abort.
SERVICE MENU Screen