1. The document discusses several power-related issues with a transceiver module. It analyzes why Band 27 can achieve minimum power levels but Band 28 cannot, finding the likely cause to be something wrong with the power amplifier (PA). 2. Another issue examined is why the transceiver passes error tests in WCDMA mode but fails in HSUPA mode. It determines the cause is probably carrier leakage from an incorrect transceiver power mode setting when transmitting at maximum power. 3. A final issue covered is lower maximum output power in online mode versus factory test mode. The document finds the feedback receiver function is not used in factory mode, and incomplete calibration of the power detection circuit likely causes abnormal

1. 1

2. Min power issue
 While doing min power measurement, B27 can reach
the power level less than -30 dBm, but B28 can NOT[1].
Transceiver
PA
ASM
B27/B28
 As shown below, in terms of hardware, B27/B28 share
the same RF path. In other words, this should NOT be
hardware issue because B27 is normal.
2

3. Min power issue
 While doing calibration, under the same RGI(RF Gain
Index), there is 10 dB gap for the output power between
B27 and B28[1].
 Nevertheless, under the same RGI, there is no gap for
the output power between B27 and B28 in transceiver
output port. Thus, there should be
something wrong with PA[1].
3

4. Min power issue
 As shown below, B27 and B28 should be configured LB
and VLB respectively[1]. Thus, if B27/B28 are both
configured LB or VLB, the issue occurs.
4

5. HSUPA EVM Phase Error Peak fail
 As shown below, HSUPA mode EVM and phase error fail.
But pass in WCDMA mode. This is due to incorrect
transceiver power mode setting
5

6. HSUPA EVM Phase Error Peak fail
 As shown below, while transmitting max output power,
high PA gain mode should correspond to high
transceiver power mode.
Transceiver
PA
Power@Transceiver + PA Gain = Power@Connector
Transceiver PA
Low Power Mode Low Gain Mode
High Power Mode High Gain Mode
6

7. HSUPA EVM Phase Error Peak fail
 Nevertheless, in this case, both high and low PA gain
correspond to low transceiver power mode.
Transceiver PA
Low Power Mode Low Gain Mode
Low Power Mode High Gain Mode
 Thus, chances are that this issue is due to carrier
leakage.
7

8. HSUPA EVM Phase Error Peak fail
 DC component on I/Q arms results in LO leakage, which
distorts constellation diagram and aggravates EVM
performance. Especially in extremely low power level.
Q
I
DC Offset
8

9. Transceiver PA
Low Power Mode High Gain Mode
HSUPA EVM Phase Error Peak fail
 With LO leakage, the lower the power is, the higher the
EVM will be. Consequently, while transmitting max
power in this case :
 Transceiver is low power mode, so the EVM will be a bit high
 PA is high gain mode, and the nonlinear effect is apparent. In
other words, EVM is a bit high in PA input, but it will be very
high in PA output.
Transceiver
PAEVM EVM
Carrier
Leakage
9

10. HSUPA EVM Phase Error Peak fail
 According to [3], HSUPA has more strict EVM
specification than WCDMA, that is why WCDMA passes,
but HSUPA fails in this case. WCDMA 17.5%
HSUPA 14%
 The only solution is to modify transceiver power mode
setting while transmitting max power.
10

11. Max power issue under online mode
 While transmitting max power, B7 can merely reach 22
dBm in online mode, but it can reach 27 dBm in
FTM(Factory Test Mode).
 Take the MMPA, SKY77645-11, for example, PA
output is larger than 27.5 dBm[2]. To Subtract
post-loss from PA output is about 27 dBm.
Online 22 dBm
FTM 27 dBm
PA
ASM
Duplexer
Post-loss
≧ 27.5 dBm
11

12. Max power issue under online mode
 Thus, as analyzed above, in terms of hardware, the B7
transmitter path is okay.
 In online mode, the output power is closed loop ; in
FTM, the output power is open loop. In other words, the
FBRX(Feedback Receiver) function is NOT used in FTM.
Chances are that this is a key factor.
PA
ASM
Transceiver
FBRX
12

13. Max power issue under online mode
 While transmitting max power in online mode, the PDET
ADC value is always zero in this case. That is to say, the
PDET ADC value is abnormal in online mode.
 From calibration log, it shows that the minimum PDET
sweep RGI(RF Gain Index) is 42. In other words, the
PDET sweep RGI is NOT complete.
13

14. Max power issue under online mode
 As mentioned earlier, the FBRX function is NOT used in
FTM. Thus, even though PDET sweep RGI is NOT
complete, the output power in FTM is still normal.
 Nevertheless, because FBRX function is used in online
mode, incomplete PDET RGI sweep leads to abnormal
output power in online mode.
 The only solution is to make minimum PDET sweep
RGI(RF Gain Index) be 32, and the corresponding power
is less than 6.8 dBm. By doing this, the PDET sweep
RGI is complete, and the output power is normal in
online mode.
14

15. Reference
[1] Min power issue based on RF54** design, Qualcomm
[2] SKY77645-11 SkyLiTE™ Multimode Multiband Power Amplifier Module, SKYWORKS
[3] 3GPP TS 25.101
15