Customer Solutions
PXI Test System for Pager Transceiver Board
Author(s):
George Negrete, Glenayre; Wayne Larson, Glenayre
Industry:
Telecommunications
Product:
Data Acquisition, GPIB & Instrument Control, LabWindows/CVI, PXI/CompactPCI
The Challenge:
Performing functional testing of a 1 GHz two-way radio board in less than a minute in a high-volume manufacturing environment where a nonskilled operator or robot must perform the testing.
The Solution:
Developing a compact, portable test platform using PXI, data acquisition (DAQ), LabWindows/CVI, and GPIB instruments.
Introduction
Wireless Access needed a test platform to provide a functional test located onsite at its contract manufacturer. Wireless Access hired National Instruments Alliance Program member, Larson Automation, to develop the functional test system. The system needed to be portable, compact, and low-maintenance. Furthermore, the system had to provide for a nonskilled operator or robot performing the testing.
System Description
These requirements led to a Plug and Play installation approach, which meant the system could be used anywhere on the production floor. The entire test system is contained within a 36-in. tall and 19-in. wide test rack that contains the PXI system controller; DAQ-based instruments - PXI-6071E 64 analog input multifunction I/O, PXI-6508 96-bit digital I/O, and PXI-6533 32-bit high-speed digital I/O; and GPIB instruments. We mounted the test fixture interface on top of the fixture.
We used only commercially available cabling for the system; the system’s only external component is the monitor. The PXI system is rack-mounted, and fits in a space 60 percent smaller than that required for a more traditional system. Thus, the system is very portable. Its small size enables one operator to manage twosystems, increasing the throughput as well as providing a labor cost savings. We selected the PXI platform for its expandability compared to a standard PC-tower-based platform. 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. We reused virtually all the previous LabWindows/CVI software written for the PC-tower-based test stations in the new system, requiring only reassignment of the analog and digital resources.
Application Description
The RF printed circuit board assembly (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 digital-to-analog converters (DACs), a reference oscillator, and IF signal conditioning. The RF PCBA also contains two voltage-controlled oscillators (VCOs), driver and power amplifiers, and a synthesizer. An incoming signal 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 frequency shift keying (FSK) signal is generated by modulation of the reference oscillator and the VCO, and then amplified by the driver and the power amplifiers. A common 50 ½ RF test point is switched from the received to the transmit path. The RX path also includes an automatic gain control (AGC) circuit 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 are ideal because of the tightly integrated capabilities of dealing with GPIB instruments, high-speed digital signal processing (600 KHz data streams), and high-density analog inputs to monitor IF signals.
We also used analog and digital resources 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 VI through a series of LabWindows/CVI user panels that provide control of the device-under-test (DUT) and fixture. We can perform every test manually through these panels. We developed test procedures using the panels, but once we optimized the tests, we automated them for production, debug, and engineering test suites.
LabWindows/CVI panels inform the operator of the test status. The user 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 indicates a particular parameter is headed out of control before the parameter is even flagged as out of specification.
For more information, contact:
Wayne Larson
Larson Automation
48521 Warm Springs Blvd., Ste. 307B
Fremont, CA 94539
Tel: (510) 656-4112
Fax: (510) 656-4140
E-mail: wayne@larsonautomation.com
