Improving Cross-Band Isolation in Multi-Band Antennas

The evolution of mobile communication technologies from GSM to 5G has demanded Base Station Antennas (BSA) to support multiple frequency bands. Some very common bands include 617 MHz-960 MHz (Low Band), 1695 MHz-2180 MHz (High Band 1), 2490 MHz-2690 MHz (High Band 2) and 3300 MHz - 3800 MHz (High Band 3). The current BSA designs cater for multiple bands in a single antenna system as it provides greater cost saving in terms of utilized real estate. However, this requires multiband antenna arrays sharing a single aperture. Designing such antennas can present many challenges such as poor cross band isolation, degradation to patterns in terms of increased squint, variation in beamwidth, high side lobes etc..