Automating Test of Advanced Radio Systems Using NI Software and PXI Hardware

"The power and flexibility of the NI hardware and software platform helped us efficiently develop a highly robust test system that meets all of our customers’ needs and meets our time-to-market requirements." - Stephen Patterson, CPE Systems Challenge: Design and develop a cost-effective test system that includes component and unplugged testing, device programming, radio signal analysis, and calibration capabilities, and enables hands-free production line testing of high-performance, point-to-multipoint advanced radio products for remote supervisory control and data acquisition (SCADA) network applications.

Solution:

Create a test system based on the NI PXI platform, NI LabVIEW, NI TestStand, and NI Switch Executive software, with pneumatic test equipment connected to the unit under test (UUT) - Includes custom shielding of the RF area for a high-performance RF test solution. In

2008, 4RF Communications began developing new radio products to expand its existing point-to-point long-range wireless products. Aprisa SR is a point-to-multipoint Smart SCADA radio product that can reach 12.5 kHz channel bandwidth and 9.6 kbps narrowband radio functions to popularize monitoring applications in oil, gas, and public utilities through the licensed 400 to 470 MHz spectrum bandwidth. Aprisa SR is designed for industries that require advanced security functions, can effectively handle increasingly complex SCADA networks, and evaluate public infrastructure such as IP architecture and smart grids. The full functionality of Aprisa SR, coupled with its high stability and well-designed advanced radio platform, enables it to be used in a variety of monitoring applications and meet current and future needs. The radio can also be set as a base station, remote workstation, or repeater, seamlessly integrating into any network topology (Figure 1). A single chassis can support a large number of serial and Ethernet interfaces and has built-in security functions.

Figure 1. Test equipment shielding for RF areas Design

Project Challenges 4RF Communications needed a different test approach to reduce unit test costs, high transmission rates, and adapt to future new product features. Therefore, 4RF approached CPE Systems, a leading manufacturer in the measurement field, to design and develop a cost-effective radio test system. The product test requirements included component testing, unplugged testing, device programming, radio signal analysis and calibration, and an unmanned automated environment.

Because 4RF Communications had limited knowledge of medium/large test equipment and insufficient internal engineering resources, it outsourced the development of the test system. After this development task was handed over to CPE Systems, we randomly selected the NI PXI platform, combined with LabVIEW and NI TestStand software, to provide the most cost-effective and flexible test solution.

Test Development Process We recorded the planned test goals and needed to achieve the following characteristics:? Board test must be completed within 5 minutes? 3,000 sets of products must be tested per month? No human intervention during testing? Even non-technical personnel can operate? Test pins can access all test points on the other side of the board? Debug equipment included? It can be expanded at any time for future products, such as more RF bands and bandwidths. We divide the test into 3 major areas: ? DC Testing: Test component values, power supply voltage, power consumption, and functional testing of low voltage shutdown, switch panel, and LED indicators. ? Built-In Self Test (BIST): Used for boot loader and software installation, testing RAM and flash memory, and confirming Ethernet address allocation. We embed these tests into the device and can access them through the command line interface. ? RF functional testing and calibration: Test and calibrate the system functions of the transmitter, receiver, and Aprisa SR board.

Figure 2. Final test system development challenges To keep up with the product development schedule, we had to develop the test system in conjunction with the product, so we made changes to five of the board designs. However, because the test system was designed with the necessary specifications and flexibility in mind, redesigning the PCB only required one change to the fixture. After maintaining good communication between 4RF Communication and CPE systems and establishing project and configuration management procedures, NI hardware and software allowed us to ensure synchronized development. One

of the main limitations of the test system is that each set of boards requires 5 minutes to test. Therefore, the RF calibration algorithm needs to be optimized to ensure efficient operation. The NI PXIe-5663 vector signal analyzer (VSA) and NI PXIe-5673 vector signal generator (VSG) can both support algorithm optimization procedures. The

PCB assembly of the Aprisa SR contains the RF transmission and reception circuits and must be tested together with its housing. Therefore, we also need to consider and include RF interference and shielding before selecting the fixture design. We use the product's CAD model to accommodate the RF shielding housing to form the top plate of the fixture (Figure 3). Simply placing the board in the housing achieves the shielding function developed by the test equipment.

Figure 3. Aprisa SR example radio settings The Aprisa SR radio has built-in data encryption capabilities that can generate simulated data streams to test receiver sensitivity. Using the NI PXIe-5663 VNA, the NI PXIe-5673 VSG can achieve different levels of radio signal recording and retransmission, and then test the sensitivity of the receiver with real data. This approach also means that the encryption program can be changed in the future without changing the test system software.

NI hardware and software play a key role in developing RF test systems. In addition to coordinating projects across multiple locations, complex RF products must be tested at high speeds and shielded. The

power and flexibility of the NI hardware and software platform helped us effectively develop a highly stable test system that met all of 4RF's requirements and ensured that the product was available on time. The result is a low-cost custom test system that can test and support the manufacturing process of new high-performance SCADA radio products.

Figure 4. Test system diagram showing hardware components and connectivity functions