5 Key Antenna Decisions When Designing IoT Devices
1. Define the required frequency range
There are many telecommunications protocols. The most popular protocols are: 2G, 3G, 4G, 5G, LTE, GSM, CDMA, WCDMA, BLE, Bluetooth, WiFi, ISM 169 MHz, ISM 315MHz, ISM 433MHz, ISM 868MHz, ISM 915MHz, ISM 2.4GHz, Zigbee, Wimax, UWB, GPS, Beidu, Compass, Galileo, L-band.
2. Determine how many feeds are required based on the selected chipset or front-end filtering/switching
Based on the RF front-end design (numbers of RF switches, chipset capabilities, RF performances required), antennas can be tuned for multiband or single band applications with single or multiple feeds. Each feed is going to be connected to a radio output pad. Example: Dual-band GPS/Bluetooth antenna (1 feed or 2 feeds), multiband 4G antenna using 1 feed or 2 feeds (1 for low band, 1 for high band).
3. Select the type of antenna needed based on overall PCB footprint available or finished product dimensions
Common categories for antennas are embedded, internal, external, and outdoor. Various technologies are also available. 2D solutions with printed traces or surface-mount antennas and keep out area. 2.5D/3D solutions with or without cable and with or without plastic carriers. Stamping, FPC, PCB, or Laser Direct Structuring are also options. It is important to consider your antenna housing because any material surrounding the antenna will cause it to perform differently.
4. Decide how the antenna will be connected to the radio
- Cable with connector (various cable types and various connectors available).
- Stripped cable without connector: One end soldered directly on the PCB.
- Vertical PCB or soldered by reflow.
- Stamping (press fit technology) and/or hand soldering or reflow soldering.
- Spring contacts on PCB (the antenna will connect to the pogopin by natural compression during the device assembly).
- Pogopin contacts on PCB (the antenna will connect to the pogopin by natural compression during the device assembly).
- Capacitive coupling (no physical contact between antenna and the PCB of the radio).
- Surface-mount (antenna soldered by reflow during PCB assembly).
5. Pay close attention to critical specifications
- Specific RF parameters required (passive testing or active testing, FCC, PTCRB, etc.).
- VSWR, Isolation, Gain, Directivity, ECC, Throughput, Impedance, Balanced vs. Unbalanced feed, Efficiency, Radiation Pattern, Peak gain, EIRP, Loadpull matching, TRP/TIS/SAR/HAC requirements, Power handling, PIM, Telecom Carrier specifications.
- What radio modules/IC will the antenna be connected to?
- Specific Mechanical and Environmental parameters required, such as torque, temperature cycles, humidity, vibrations, wind load, weight, cosmetic (VDI), water ingress, reflow, pull force, bending, plenum rating, UL rating, UV resistant, salt resistant, dust resistant, shock resistant, vandalism resistance, chemical resistance, drop test, package drop.