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TEST AND MEASUREMENT
17. Repeat steps 6 to 15 for GSM 1800 on the channels listed below.
Channel Bch Lch Mch Hch Tch GSM 1800 520 630 700 810 870
6.6 I and Q Values
NOTE: By observing the image leakage and adjusting the relative gain between I and Q channels, phase error and modulation spectrum can be improved. With the I, Qch adjustment procedures the transmitter must be set to Power Level 5 (this presents the worst case of non-linearity) so care must be taken that the spectrum analyser used can accept a signal input of 33 dBm. If not, an appropriate attenuator must be used.
I, Qch Gain
IMPORTANT: I, Qch offset calibration should be done before this calibration. Spectrum Analyser Setup. centre frequency = 902.4 MHz RBW = 10 kHz VBW = 10 kHz Span = 1 MHz Sweep time = 2 sec 1. On the Channel box, highlight CHANGE CH GSM. a. Press the left-right arrow keys until channel number �62� is visible in the window. Press ENTER to select. b. Press the down-arrow key until the POWER LEVEL field is highlighted. Press the left-right arrow keys until PL5 is visible in the window. Press ENTER to select. c. Press the down arrow until the TX DATA field is highlighted. Press the left-right arrow keys until NRL 1 is visible in the window. Press ENTER to select.
Figure 6.24: Image leak ratio 2. Using the spectrum analyser measure the image leak ratio. Image leak ratio is the measured ratio of peak power and the power at 135 kHz below peak frequency.
Example: peak power (902.468 Mhz) = 33 dBm power at 135 kHz below peak power = -9 dBm image leak ratio = 33 dBm - (-9 dBm) = 42 dBm MCUK990801C8 Service Manual Section 6 � 45 � Issue 1 Revision 0
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