I/Q Modulator Amplitude Balance And Phase Shift Tuning - Nokia NSB-1 Series Tuning Instructions

NSB–1/3
Tuning Instructions

2. I/Q Modulator Amplitude Balance and Phase Shift Tuning

The purpose of this tuning operation is to adjust the I/Q modulator d.c. off-
sets and the I/Q modulator amplitude balance and phase shift.
I/Q modulator d.c. offsets, amplitude balance and phase shift tuning:
– Connect spectrum analyzer (with an attenuator if needed) to the exter-
nal antenna connector of the phone.
– Select Tuning –> TX I/Q...
– Select I/Q tuning values from the PC's memory, the phone's EEPROM
or factory default values.
– Check that the channel is 661 and the TX Data Type is Cont1.
If it doesn't, change it in RF Controls window.
– Adjust spectrum analyzer centre frequency to 1880 MHz, Span 200
kHz, Res BW 10 kHz, Video BW 1 kHz and Sweep time 0.5 s – 1s.
– Select the "TX I d.c. offset" option.
– Adjust the level of centre frequency (CHF signal) to minimum by vary-
ing D/A converter value with <– and –> buttons.
– The amplitude difference between CHF–67.7 kHz and CHF should be
>30 dB.
– Select option "TX Q d.c. offset".
– Adjust the level of signal CHF to minimum by varying D/A converter
value with <– and –> keys.
Page 12
CHF
–67.71 kHz
D.C. offset
tunings:
Set this value
to minimum
> 30 dB
Technical Documentation
+67.71 kHz
Amplitude &
> 35 dB
phase difference:
Set this value
to minimum
Original 06/98
PAMS