To improve antenna efficiency, Nordic Thingy:91™ has dynamic antenna tuning.
Different tuning components are used for different frequencies. This is achieved by using tuning components between two SP8T RF switches. The switches are automatically controlled by the nRF9160 LTE modem and set to the correct state based on the frequency of operation. Six paths are used for LTE frequency, and one path is used for Global Positioning System (GPS) frequency.
| RF_SW3 | RF_SW2 | RF_SW1 | State | Band | Frequency |
|---|---|---|---|---|---|
| 0 | 0 | 0 | RF2 - RFC | Not used | Not used |
| 0 | 0 | 1 | RF7 - RFC | 13U/D, 28D | 746 MHz - 803 MHz |
| 0 | 1 | 0 | RF5 - RFC |
12U/D, 17U/D, 28U 1U/D, 2U/D, 3U/D, 4U/D, 25U/D |
698 MHz - 748 MHz 1710 MHz - 2200 MHz |
| 0 | 1 | 1 | RF3 - RFC | 5D, 20U, 26D | 824 MHz - 894 MHz |
| 1 | 0 | 0 | RF1 - RFC | 8U/D | 880 MHz - 960 MHz |
| 1 | 0 | 1 | RF8 - RFC | 5U, 20D, 26U | 791 MHz - 849 MHz |
| 1 | 1 | 0 | RF6 - RFC | Not used | Not used |
| 1 | 1 | 1 | RF4 - RFC | GPS | 1574 MHz - 1577 MHz |
Figure 1. Antenna tuning circuitry schematic
