RF fixture electronics for testing RF devices

Details RF fixture electronics for testing RF devices RF fixture electronics for testing RF devices

2001-10-31

2004-06-15

Hoff, Marc S. (Department: 2184)

Data processing: measuring, calibrating, or testing

Testing system

Including multiple test instruments

C324S750010

Reexamination Certificate

active

06751570

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to the field of radio frequency (RF) test and measurement systems, and more specifically to the electrical and software components useful for test and measurement within RF enclosures.
BACKGROUND OF THE INVENTION
RF enclosures may be used in a variety of test and measurement applications when the amount of RF radiation that impacts a device under test (DUT) must be carefully controlled. Specific examples include prototype testing and production testing of cellular telephones, portable computers, pagers, and other small electronic devices. Often RF enclosures are used in automated or semi-automated environments in which machines are used to place the DUT inside the RF enclosure. In these types of test environments, it is desirable to be able to evaluate the functionality and correct operation of the DUT while the DUT is within the RF enclosure. The use of electronics circuitry and software may be used to apply specific test resources to the DUT and measure the responses. In most applications, the electronics circuitry and software is located both internal and external to the RF enclosure. However, placing high speed electronics within the RF enclosure reduces the RF isolation and therefore degrades the testing accuracy. The proximity of the RF electronics to the DUT also influences the measurement accuracy. Thus, in test and measurement situations involving RF devices there are often two competing design considerations: Including more sophisticated electronic components within an RF enclosure allows more accurate and more comprehensive test procedures to be executed. However from the point of view of RF isolation and noise reduction, fewer electronics components creates smaller amounts of spurious RF energy which leads to improved RF measurements. These competing considerations must both be addressed when designing RF test and measurement systems that incorporate RF enclosures.
Referring now to
FIG. 1
, a block diagram of RF electronics and software suitable for testing RF devices within an RF enclosure is shown, according to the prior art. A system controller
110
is coupled to a fixture controller
130
in order to send to RF device
150
and receive information from RF device
150
. It should be noted that in general, fixture controller
130
is operable to have functionality internal and external to RF enclosure
120
. Fixture controller
130
interacts with custom electronics and software
140
to generate test inputs and receive test outputs from the RF device
150
. RF device
150
may be coupled directly to the custom electronics
140
or may also be coupled to a nest
160
that is then coupled to custom electronics
140
. Nest
160
is often used as the point of attachment for RF device
150
, and is operable to provide sensors that measure the state of RF device
150
.
It should be noted that the structure of
FIG. 1
is representative of the type of fixture system functionality that is currently implemented, although other approaches can be used. The use of custom electronics within the RF enclosure limits the applicability of the RF test system to types of RF devices with different test requirements. Often a particular RF test system is designed to test a particular RF device. So, when a new RF device product line is introduced, a new RF test system must be created. Also, the use of fixture control functionality internal and external to the RF enclosure may be unnecessary, provided that the control functionality external to the RF enclosure can perform the equivalent tasks. An additional issue with the RF test systems currently used is the location of the electronics within the RF enclosure. Ideally, the electronics should be located as close to the RF device under test as possible, since this improves the measurement accuracy. It is also desirable for this circuitry to keep the number of data lines leaving the RF enclosure to a minimum. In many of the current RF test systems, emphasis is placed upon providing the desired measurement functionality. This goal is attained at the expense of providing optimal location of test electronics.
A very important aspect of RF fixture design is the association of information that is unique to the RF device as it relates to the RF fixturing system and the overall test process. This association is particularly important as RF fixturing systems are shared across multiple RF device test plans, as well as, individual fixtures for a particular RF device. This information often consists of test equipment identification, test path calibration constants, and configuration management data required for the test process. Existing solutions for integrating product specific test information into the test process range from very simple hard-coded schemes that are embedded right into the test plan to highly sophisticated database oriented solutions. Each scheme has its unique advantages and disadvantages. The most simplistic solutions lack the flexibility to support multiple unique RF devices, while the more advanced solutions require centralized network connections to be available and are often very expensive.
Thus, there is an unmet need in the art for a RF fixturing system that minimizes the amount of electronics circuitry required within the RF enclosure, that is applicable to a number of RF devices, that places the RF electronics as close to the measurement location as possible, that reduces the number of data lines entering the RF enclosure, and that allows product-specific test information to be stored and retrieved within the RF fixturing system in a convenient, configurable and cost-effective manner.
SUMMARY OF THE INVENTION
The RF fixturing system of the present invention allows a plethora of RF devices to be tested using a standard configuration of electronics components of an RF test fixture in combination with device-specific resources resident on one or more electronic customizations or nests. Testing different RF devices can be accomplished by changing the type of customization or nest that is inserted within the RF enclosure. The system thus contains at least an RF test fixture having a standard set of electronics, a nest operable to receive an RF device to be tested in the RF test fixture, and an interface element operable as an interface between the standard set of electronics of the RF test fixture and the RF device. The functionality of the nest that is specific to the RF device within the nest and the functionality of the standard set of electronics work in combination to facilitate testing of the RF device. Different RF devices may be easily tested by substituting different nest having functionality directed more to one or more RF devices to be tested within the RF test fixture.
Depending upon the test and measurement requirements, multiple nests may be present within the RF fixturing system. A RF device is coupled to the nest within the RF enclosure. The nest contains specific features that allow the particular RF device within the nest to be properly tested or evaluated. One of the features located on the nest is a non-volatile memory device. This memory device may be used to store and retrieve product-specific test information, such as nest information, calibration information, test algorithms, operational programs, and other information relevant to the test process. This collection of information may be nest-specific and can be changed depending upon the type of RF device under test. Placing this information in non-volatile memory within the nest allows RF device-specific information to be stored close to the RF device, modified easily, and retrieved easily during a test process.
The nest or “customization” is coupled to a nest interface component that serves as the interface between a standard set of resources located within the RF enclosure and the RF device. The standard set of electronics within the RF test fixture provides the electronic resources, preferably at the correct physical location within the fixture, to test a wide array of test devices without requiri

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