er Feeder GSM 1800 Node B Figure 7.17 Air decoupling in single-band antennas. The single band antennas get separated either by a vertical distance or by a horizontal distance. Side by side antennas, e.g. GSM1800 and UMTS may decouple already at 40 dB. Thus, to apply to the most relevant frequencies (with better than 42 dB) recom- mended coupling distance (including security/error margin) will lie between 0.9 and 1.0 m horizontal separation. Likewise in the vertical case, to reach a decoupling of more than 42 dB in the UMTS frequency range, a coupling distance of 1.8-2.0 m (including security/error margin) of vertical separation is recommended. Deploying 3G Networks 7.12.1.2 Wideband Antenna Figure 7.18 [7] illustrates a wideband solution2 20 for GSM1800 and UMTS using a di- plexer, one feeder cable. This solution appears advantageous because it needs only one feeder cable and one antenna panel. However, it has limitations because it imposes the same antenna characteristics on the GSM1800 and the UMTS bands. Such limitation, for example, prevents different electrical down tilt for the two systems. Wideband antenna Dualband antenna Feeder Diplexer Feeder Diplexer Diplexer GSM 1800 GSM 1800 Node B Node B Figure 7.18 Wideband antenna configuration with Figure 7.19 Dual band antenna configuration one diplexer. with two diplexers. 7.12.1.3 GSM 1800/UMTS Dual Band Antenna with Double Diplexers Double diplexer dual band antennas as illustrated in Figure 7.19 [7] include one BTS- side diplexer, one feeder cable, one antenna side and a GSM 1800/UMTS dual band antenna²¹ consisting of two antennas within one panel. The BTS-side diplexer will gen- erally afford 45-48 dB of decoupling from GSM 1800 transmit port to UMTS receive port. While the antenna side diplexer provides a decoupling value of 30-32 dB, which generally sufficient. This dual band antenna solution with two diplexers does allow different gain and elec- trical tilt selection for GSM 1800 and UMTS. On the other hand, it demands the imple- mentation of two diplexe