RF9678 Datasheet, PDF (9/16 Pages) RF Micro Devices – W-CDMA TRANSMIT MODULATOR AND IF AGC

Preliminary
RF9678
Carrier Suppression Optimization
7) While maintaining a constant DC level (1.3V) on the "ISIG-" pin, adjust the DC level of the "ISIG+" input in as small an
increment (~1.0mV) as the test equipment will allow. Observe the output on the spectrum analyzer. Adjust the DC level
until the carrier signal is at a minimum. Typically, the minimum will occur within a ±20mV window of the reference voltage
(1.3 ± 0.02V).
8) While maintaining a constant DC level (1.3V) on the "QSIG-" pin, adjust the DC level of the "QSIG+" input in as small
an increment as the test equipment will allow (1.0mV). Observe the output on the spectrum analyzer. Adjust the DC level
until the carrier signal is at a minimum. Typically, the minimum will occur within a ±20mV window of the reference voltage
(1.3 ± 0.02 V).
9) Repeating Steps 7 and 8 may yield slightly better suppression. The output spectrum should look similar to Figure 7.
(Note the suppressed carrier signal.)
Ref Lvl
15 dBm
10
1
0
Marker 1 [T1]
RBW
5 kHz RF Att 40 dB
0.22 dBm VBW 50 kHz
379.84987475 MHz SWT 33 ms
Unit
dBm
A
5
-10
-20
1RM
-30
EXT
-40
-50
-60
-70
-80
Center 380 MHz
Date:
6.FEB.2001 00:55:31
32.5 kHz/
Span 325 kHz
Figure 7. Optimized Carrier Suppression
Sideband Suppression Optimization
10) Adjust the AC amplitude of the "ISIG+" signal in as small an increment as the test equipment will allow (~1mV).
Observe the output of the spectrum analyzer. Adjust the AC amplitude of the signal until the sideband signal is at a mini-
mum. The minimum sideband signal level should occur within ±20mV adjustment. (0.500±0.02V)
11) Adjust the AC amplitude of the "QSIG+" signal in as small an increment as the test equipment will allow (~1mV).
Observe the output of the spectrum analyzer. Adjust the AC amplitude of the signal until the sideband signal is at a mini-
mum. The minimum sideband signal level should occur within ±20mV adjustment (0.500±0.02V).
12) Adjust the phase of the "QSIG+" signal in as small an increment as the test equipment will allow (`0.1°). Observe the
output of the spectrum analyzer. Adjust the phase of the "QSIG+" signal until the sideband suppression is at a minimum.
The sideband signal should reach a minimum within ±1° of adjustment (90±1°).
13) The device is now optimized for maximum carrier and sideband suppression. The output spectrum should look simi-
lar to Figure 8. (Note the suppressed carrier and sideband signals.)
Rev A4 010622
5-99