t the same level as that specified for the spurious emissions, we need the decoupling between antenna connectors. Blocking: UMTS 3GPP TS 25.104 recommendation specifies that out of band, the maximum level of interfering signals (CW carrier) for blocking is equal to -15 dBm. The GSM power is assumed to be 43 dBm at the antenna connector. This power is over 200 kHz, rather than a CW interfering source as defined in TS 25.104. Comparing this value with the UMTS blocking point, we can calculate the necessary isolation between the two antennas. Then, assuming that the jamming system is Tx GSM/DCS and the Deploying 3G Networks victim the Rx UMTS, with a GMS/DCS transmit output power of 43 dBm the blocking point out of the receiving band is -15 dBm. Thus, the necessary isolation between an- tenna connectors is 58 dB. In conclusion, from the preceding analysis, we see that we need an isolation of 37 dB and 45 dB to protect GSM900 and 1800 from UMTS interference, respectively. We can obtain these decoupling values by physical separation between the GSM900 and/or 1800 antenna and the UMTS antenna. Table 7.35 summarizes the required isolation, in case of co-location: From the preceding analysis, we see that we need an isolation of 37 dB and 45 dB to protect GSM900 and 1800 from UMTS interference, respectively. We can obtain these decoupling values by physical separation between the GSM900 and/or 1800 antenna and the UMTS antenna. Table 7.35 UMTS GMS Isolation Requirements System specification re- UMTS Tx to UMTS Tx to GSM900/1800 Tx quirements GSM900 Rx (dB) GSM1800 Rx (dB) to UMTS Rx (dB) Spurious emissions and 90 (39 for BTS intermodulation products R99 or later) Blocking To obtain the isolation of 90 dB to protect UMTS from GMS900 or/and 1800 interfer- ence gets more difficult through only space separation. We would need specific filters at the GSM side to reduce the spurious emissions levels, and on the UMTS side to protect the UMTS BTS from GMS emissions. The latter will be imperative when using: dual band antenna or t