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PXI Test System for Pager Transceiver Board		[ back ]
By George Negrete, Senior Director of Manufacturing, Glenayre, Inc. Wireless Access Group and Wayne Larson, President, Larson Automation The Challenge Performing functional testing of 100 MHz two-way radio board in less than a minute in a high-volume manufacturing environment where a non-skilled operator or robot must perform testing. The Solution Develop a compact, portable test platform using PXI, LabWindows/CVI, data acquisition, and GPIB instruments. Introduction Wireless Access needed a test platform that would provide a functional test located on-site at its contract manufacturer. The test system needed to be portable, compact and low maintenance. Furthermore, the system had to be designed such that a non-skilled operator or robot could perform the testing.
System Description These requirements led to a plug-and-play installation approach, which allowed the system to be used anywhere on the production floor. The entire test system was contained within a 36" tall and 19" wide test rack that contained the PXI system controller; DAQ-based instruments -- PXI-6071E 64 AI Multifunction I/O, PXI-6508 96 bit Digital I/O, and PXI-6533 32 bit High Speed Digital I/O; and GPIB instruments. The test fixture interface was mounted on top of the fixture. Only commercially available cabling was used for the system, and its only external component was the monitor. Because the PXI system was rack mounted, it fit in a space 60% smaller than that required for a more traditional system. Thus, the system was very portable. Its small size enabled one operator to manage two systems, thereby increasing the throughput as well as providing a labor cost saving.		Providing the use with an overview of the test system allows them to monitor or control all aspects of the test fixture with the click of a mouse
The PXI platform was selected for its expandability compared to a standard PC-tower-based platform. In order to grow our previous tester from a single board to four-board capability, we needed to add additional analog and digital resources. The PXI platform addressed our concerns about the testability of future products and about adding boards on the panel. Virtually all the previous LabWindows/CVI software written for the PC-tower-based test stations was reused in the new system, requiring only reassignment of the analog and digital resources.
Individual panels can be displayed or closed to provide a simple interface, or detailed information about the test process	Application Description The RF PCBA is a full two-way radio used for advance messaging. It contains two custom integrated circuits; a 900 MHz receiver chip; and a mixed signal, multipurpose demodulator chip that contains DACs, a reference oscillator, and IF signal conditioning. The RF PCBA also contains two VCOs, driver and power amplifiers, and a synthesizer. An incoming signal (RX) at 900 MHz is double down converted to a pair of I/Q signals, which are then demodulated to a 600 kHz serial data stream processed by the baseband PCBA. The outgoing 4-level FSK signal (TX) is generated by modulation of the reference oscillator and the VCO, and then amplified by the driver and the power amplifiers. A common 50 ohms RF test point is switched from the received to the transmit path. The RX path also includes an AGC for input power protection. The test station performs full functional tests to verify functional and parametric performance of the RF PCBA.
Test Procedures The PXI system tests four boards at one time on a panel, which reduces handling and improves test speeds. Each part is tested with a full suite of transmit and receive tests. The RF boards are internally DAC tuned and require a great deal of digital control. The PXI platform and the LabWindows/CVI environment were ideal due to the tightly integrated capabilities of dealing with GPIB instruments, high speed digital signal processing (600KHz data streams), and high density analog inputs to monitor IF signals. Analog and digital resources were also used for a variety of static DC voltages, current shunts, and AC waveforms on the custom test interface board and control pneumatic solenoids, RF switches, and onboard relays. High-speed digital control signals download 80 bit control codes to the onboard synthesizer and command the serial port to adjust DACs that calibrate and modulate the VCOs and reference oscillator. The test station operates as a virtual instrument through a series of LabWindows/CVI user panels that provide control of the DUT and fixture. Every test can be performed manually through these panels. Test procedures were developed using the panels, but, once the tests were optimized, they were automated for production, debug, and engineering test suites. LabWindows/CVI panels inform the operator of the test status. The operator receives summarized test results (pass/fail). The results are automatically logged to disk and downloaded to the factory network and ftp site. We use a program written in LabWindows/CVI with the SPC Toolkit to review daily results and Pareto analysis for each test station. This information is used to indicate a particular parameter is headed "out of control" before the parameter is even flagged as out of specification.
Larson Automation, Inc. Address: 960 Rincon Circle, San Jose, CA 95131 Tel: (408) 432-4800 Fax: (408) 432-4848 Email: info@larsonautomation.com