Telecommunication certification organizations around the world provide approvals for licensed and unlicensed wireless products. The equipment requiring approval may include ISM devices, smart phones, broadcasting equipment, digital transmission systems, marine and aviation communication systems, land-mobile, point-to-point devices, EPIRB, PLB, BPL, PDA, and radar. Nearly all devices that use radio frequencies, from cordless phones to microwave broadcast towers, require certification. The communication standards that these devices implement can vary. For example, just to name a few: 802.11a/b/g, Bluetooth, WiFi, LTE, WiMAX, GSM, CDMA, WCDMA, HSPA (HSDPA, HSUPA), and frequency hopping spread spectrum.
Test setups for compliance testing
Specific absorption rate (SAR) and maximum permissible exposure (MPE) evaluations are required for most certifications. The tests must prove compliance with SAR and/or RF field strength limits. But it doesn’t stop there. The technical reports must also show compliance with applicable technical requirements for the device being certified. The reports must describe to the FCC, Industry Canada, or other regulatory authority the test procedures used and include comparisons between the actual measurements and the technical requirements. Along with the test data, the reports typically include a description of the test equipment and pictures of the setup.
Depending on the test procedures and the required data, it is common to use test and measurement equipment with advanced capabilities with regard to the standard being tested. Test equipment with modulation and demodulation capabilities for the waveform of interest can be used to measure metrics. Such test equipment can help validate the conformity to the protocol being implemented. It can even be used earlier, during the system design phase, for testing and validation in preparation for certification.
Testing for compliance with new standards
This approach works well for testing devices that implement well-known standards and for which dedicated test and measurement equipment is available. But how about new standards? How will the first devices be tested in preparation for certification? What test equipment should be used to characterize and validate their compliance? Should the device under test be tested by another same “golden device”?
People who work with advanced waveforms and standards recommend using test equipment that incorporates a software-defined radio (SDR) when characterizing the first few devices that implement a new standard. SDR is a generic term used to describe programmable radio hardware not limited in its design to a specific communication standard.
The benefits of SDRs
SDRs offer flexibility, especially in their capability to be programmed to implement any given standard. Not only can they implement the baseband processing section of the required communication protocol, they can detect impairments, keep performance metrics, and collect data related to the compliancy of a waveform transmitted by the device under test. In a simple example, where the compliancy of a transmitter device is being tested, an SDR platform equipped with the proper RF front-end can be used to act as the receiver. The FPGA of the SDR platform would be programmed to demodulate the received waveform and to monitor in real-time the different aspects and parameters of the waveform that defines whether or not the transmitter is compliant. There are theoretically no limits in terms of how many different waveforms an SDR-based wireless test and measurement system can be reprogrammed with.
Nutaq, as an SDR platforms provider, ensures that a smooth workflow for programming the platforms is maintained even in the case of the most computationally demanding and complex waveforms. The ability to record or visualize signals in real-time at any given stage in a receiver chain is just an example of supported functionality. With such features, Nutaq SDRs and digitizers are ideal for integration with the baseband digital component of SDR-based wireless test systems.