Cal-Bay Systems Delivers Advanced Software Architecture for Testing RF Amplifiers

Author(s):
Abdulla Ghouse - Cal-Bay Systems, Inc.

Industry:
RF/Communications, Manufacturing

Products:
LabVIEW, TestStand

The Challenge:
Developing a cost-effective, rugged, and highly flexible test architecture to decrease test development time and increase test instrument interchangeability on the production floor for manufacturing and functional RF amplifier testing.

The Solution:
Building a rugged, reliable, and inexpensive test architecture based on National Instruments LabVIEW, NI TestStand, NI Switch Executive, and interchangeable virtual instruments (IVI).

Architecture Requirements

Performing tests is critical in RF amplifier production. At Cal-Bay Systems, our customers are leading RF amplifier manufacturers. They identify the tests to be performed on the amplifiers they produce, and they also design and develop test stations for various stages of amplifier production. For the present application, the customer’s test bench is equipped with RF instruments controlled by a PC through GPIB. RF signal source provides the input signal to a device under test (DUT). Our task was to:

• Develop a modular software architecture to reduce test development time and increase test code reuse
• Take advantage of existing instrument drivers to eliminate instrument driver development cost
• Use NI Switch Executive for sophisticated RF signal routing
• Support the instrument interchangeability at the customer’s factory with less support from the test development team and no code change
• Provide driver capability for the DUT

LabVIEW Driver Capability

Using NI LabVIEW, we developed an amplifier driver class based on each driver’s amplifier. The drivers are called instrument-specific drivers (ISDs), and these drivers communicate with the amplifier based on two aspects – the protocol and the hardware interface specified by the customer. We developed polymorphic LabVIEW APIs to access the ISDs. The APIs use an instrumentation gateway interface (IGI), a virtual instrument that calls the ISD using LabVIEW, which then calls any test module ISD using the same APIs. Because we developed LabVIEW APIs based on the amplifier driver class, we used the same modules to test DUTs that fall under the defined amplifier class. We used LabVIEW to develop the ISDs and APIs in less time compared to Microsoft Visual Basic, the development platform we previously preferred.

Interchangeable Virtual Instruments (IVIs)

We designed the architecture based on the latest industry-standard instrument driver technology. The architecture takes advantage of IVI foundation-defined classes for switches, DC power supplies, power meters, RF signal generators, digital multimeters, and spectrum analyzers. It uses the instrument manufacturers’ IVI drivers, avoiding the cost of in-house development. Because there are two types of IVI drivers available – namely IVI-C and IVI-COM – we developed common instrument APIs for each instrument class. These APIs can determine the driver type from the IVI configuration store and then automatically call both types of IVI drivers. We use NI IVI APIs to call the IVI-C driver. With the powerful capability of the LabVIEW automation server, we could call the IVI-COM drivers using wrapper APIs developed in-house. With NI Measurement & Automation Explorer (MAX), we gave the customer great flexibility in changing the instruments on the production floor, reducing test bench downtime significantly.

Signal Routing

We developed IVI-C drivers in-house for the RF switch drawer in the test bench. With the powerful features of NI Switch Executive, we configured the signal routes for each project and formed the route groups to configure the RF signal path from source to sink quickly. We used the NI TestStand switching step to trigger the route group and reduce test code development time by configuring the switch in an NI TestStand step property. We configured the group names in the parameter file, giving the customer the flexibility to reuse the same test module for different platforms by changing the route configuration XML file.

Test Catalogue

We developed test modules using LabVIEW and NI TestStand. The modularity provided by NI TestStand helped us achieve 90 percent reusability of the test modules. We stored the test modules as test sequences and named the collection of test sequences “test catalogue.” Using the validated, ready-to-use test modules in a new project reduced test development time dramatically by decreasing the effort of setting up the test sequence calls, the parameter file, and the test limits.

System Benefits

With National Instruments software, we realized the following benefits:

Comparison Parameter	Earlier Process	Architecture based on LabVIEW and NI TestStand
Test development time	Nearly six months to complete a project	One month, due to greater reusability provided by the LabVIEW and NI TestStand architecture
RF signal route configuration	Time-consuming and unscalable	Complete configuration independent of the test code, due to the power of NI Switch Executive and IVI-C switch driver; 90 percent reduction in switch development time
Driver development	SCPI-based NI-VISA drivers that tightly couple with the test code, reducing modularity and requiring rebuilding of the project for any driver change	Significant cost reduction due to off-the-shelf NI IVI drivers and other vendors’ instrument driver databases; standardization of code development in the test group (Uncoupling the driver from the test code avoided the rebuilding of the entire test code in the event of a driver change.)

With the seamless integration of LabVIEW, NI TestStand, NI Switch Executive, and IVIs, we developed a powerful yet flexible architecture that satisfied our customer’s requirements in a significantly shorter time.

 

For more information, contact:

Abdulla Ghouse

Cal-Bay Systems, Inc.

16 Technology Drive, Suite 160

Irvine, CA. 92618

Tel: (949) 727-2010

Fax: (949) 727-2022

E-mail: abdulla@calbay.com

 

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