The distance between this site and the CDMA and GSM antennas is very close, about 1.6m. The CDMA antenna is on the left, and the GSM antenna is on the right. The CDMA antenna faces the GSM antenna, and is about 0.4m lower than the GSM antenna.
The GSM antenna radiation sector on the right receives interference, and its interference band reaches to level 5 or more. The case is shown in the picture below:
After arriving at the site, the test was carried out according to the following steps:
1. Installed an anti-blocking filter on the GSM main diversity, observed the mobile interference band, and found that the GSM interference band was reduced to level 1 or 2.
2. Without disassembling the filter on the GSM, installed a spurious suppression filter on the CDMA transmitting port. The interference band was maintained at level 1 to 2, which was the same as the interference band when only the GSM filter was installed.
3. Removed the filter on the GSM, and still installed the anti-spurious filter on the CDMA transmitting port, observed the interference band, whichwas level 5.
Processing result: This site has a mobile idle pole on the next platform where the antenna was located. The CDMA antenna was moved to this pole, so that both the horizontal isolation and the vertical isolationreached 6 meters. In addition, there was a wall barrier, which increased the isolation and finally solved the interference problem.
Conclusion: Installing a spurious suppression filter on CDMA cannot solve the interference problem of GSM. Installing a blocking filter on the GSM can reduce the interference level from level 5 to level 1 to level 2. Therefore, the interference is the blocking interference of the GSS itself.
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