Why is Over the Air Antenna Testing Important?
During research and product development of any Internet of Things (IoT) device or Machine to Machine (M2M) product, it is important to make sure the antennas designed or selected will perform the way they are intended. For example, when designing an antenna for a large stationary device like a vending machine, it is likely installed or placed against a wall. Designing or selecting an antenna that concentrates its energy and radiates toward the front of the device would be ideal for this environment. In the case of a mobile device, like a smart phone, it is important for the antenna to radiate in all directions and not lose communication link when the user moves around or faces a particular direction away from the cell tower. Over-the-Air antenna testing and measurements are the only way to qualify the entire signal path and antenna pattern of a wireless device.
Most cellular technologies, such as GSM, GPRS, EGPRS, CDMA, 1xRTT, 1xEVDO, WCDMA, LTE, LTE Advance and wireless technologies such as 802.11 a/b/g/n/ac, Bluetooth, and ZigBee will utilize an error correction algorithm to compensate for the poor receive signal either by increasing the output power or reducing the data rate before the connection is lost. This in turn will reduce battery life, heat up the device, and/or lower the data transfer rate. OTA testing of antennas can help product development teams identify the problematic areas and increase product reliability and end user experience.
As many IoT and M2M devices become increasingly more compact, antennas are sometimes forced to be placed near other antennas, displays, computer processors, high-speed memory, etc, all of which can interfere and degrade the devices over-the-air (OTA) performance. In addition to power measurements, OTA testing can perform sensitivity measurements to illustrate how the internal components are effecting the RF radio’s performance. This allows product developers to see where the issues are during normal operation and how they are impacting the product’s performance.
When integrating an antenna into a product, the environment can influence the characteristics of an antenna.
- Antenna pattern change
– The shape of the radiation pattern can changes as energy is absorbed or reflected
- Impedance mismatch loss
– Energy going to the antenna is reflected back
- Antenna detuning
– The frequency where energy radiates at maximum power shifts to another frequency
– Emission from internal components and co-existing antennas degrade the antenna performance
- Product Certification
– Wireless Carriers such Verizon, AT&T, T-Mobile, and Sprint require cellular products be CTIA (Cellular Telecommunication and Internet Association) certified and meet minimum performance requirements before they are allow on their network
-PTCRB (PCS Type Certification Review Board) Certification
OTA Measurement Services
- Antenna Testing – Antenna Characterization / Antenna Pattern Measurement
– Where is the antenna radiating, antenna radiation pattern
– How much is the antenna radiating at its peak direction
– How much of the input energy is the antenna radiating
- PTCRB and CTIA Approved Testing
- TRP (Total Radiated Power)
– What is the overall antenna power radiated by the antenna
- Measures at every 15 degree increments
- Phi Axis from 0 – 165 degrees
- Theta Axis from -165 to 165 degrees
- Takes 264 measurements per polarization
- Total 528 measurements
- TIS (Total Isotropic Sensitivity)
-What is the overall lowest signal the antenna can receive and maintain a reliable communication link
- Measures at every 30 degree increments
- Phi Axis from 0 – 150 degrees
- Theta Axis from -150 to 150 degrees
- Takes 50 measurements per polarization
- Total 120 measurements
- Intermediate Channel Degradation Sweep
– How are the channels across the operating frequency band affected by the interference from the antenna’s internal circuitry, like computer processors, clocks, high speed memory, display, etc.
- Co-Existence Interference
– How much desense occurs when multiple wireless transceivers are operating at the same time.
What products/technologies commonly require OTA Testing?
Many of these products are also known as machine to machine (M2M) or Internet of Things (IoT) devices. Intel analyzed that there are about 2 billion IoT devices in 2006, 15 billion devices today and projected 200 billion by 2020.
- Telemedicine / Telehealth products
- Warehouse management products
- Traffic control systems
- Fleet management products
- Robotics systems
- Vending Machines
- Computing equipment
- Mobile payment systems
- Home monitoring/Automation
- Mobile Phones
- Laptops or tablets
- Utilities management products
- Other wireless products