Power sensor module for microwave test systems

Details Power sensor module for microwave test systems Power sensor module for microwave test systems

1999-06-04

2002-05-28

Grimley, Arthur T. (Department: 2852)

Data processing: measuring, calibrating, or testing

Testing system

Of circuit

C324S142000, C324S1540PB, C324S601000, C324S614000

Reexamination Certificate

active

06397160

ABSTRACT:

This invention relates generally to automatic test equipment, and more specifically to automatic test equipment for testing and characterizing RF/microwave devices.
Automatic test equipment, commonly known as a “tester,” has traditionally been used in processes for manufacturing semiconductor devices to determine whether the manufactured devices contain defects. In this way, large volumes of devices can be tested quickly, thereby reducing both time-to-market and production costs.
More recently, testers have been used for both testing and characterizing high frequency semiconductor devices, which are designed to operate in the radio frequency (RF) and microwave ranges. Such “wireless” devices include those used in the cellular telephone industry, where high volume, low cost production is especially important.
One characteristic that is frequently measured is the power produced by RF/microwave devices. Because voltage and current levels of high frequency signals are generally difficult to measure, power measurements are often used to characterize the performance of RF/microwave devices.
FIG. 1
shows a partial block diagram of a conventional tester
100
used to measure power generated by a device under test (DUT)
118
, which is designed to operate in the RF or microwave band. The tester
100
has a tester body
102
, which includes a computerized controller
106
that can be programmed by a tester operator to perform various test and analysis operations. For example, the controller
106
may be programmed to control RF signal sources (e.g., an RF source
110
) and receivers (e.g., an RF receiver
112
). The RF source
110
and the RF receiver
112
generate and detect, respectively, test signals for the DUT
118
.
The tester
100
also includes a test head
104
, which generally routes the test signals between the tester body
102
and the DUT
118
. Accordingly, the test head
104
includes switching modules (e.g., a switching module
114
) for directing the test signals between the RF source
110
, the RF receiver
112
, and the DUT
118
.
In a typical test configuration, an external power sensor
116
, such as the model HP ECP-E18A power sensor sold by Hewlett-Packard Company, Palo Alto, Calif., USA, is coupled to the switching module
114
and used for measuring power generated by the DUT
118
. Thus, the switching module
114
also routes signals between the power sensor
116
and the DUT
118
. The power sensor
116
is also typically coupled to a power meter (not shown), such as the model HP EPM-441A power meter sold by Hewlett-Packard Company.
We have recognized that performing power measurements using the test configuration described above may result in measurement uncertainties, which can adversely affect the accuracy of the power measurements.
For example, a major cause of measurement uncertainty is impedance mismatch between the power sensor and the device under test. This impedance mismatch can cause signal reflections that affect the amount of power provided to the power sensor, thereby resulting in inaccurate power measurements. Further, impedance mismatches tend to be more prevalent in test systems operating in high frequency ranges.
In addition, different test systems can yield different levels of impedance mismatch. This means that power measurements made on the same device might vary from tester-to-tester. Further, testers such as the tester
100
are meant to test and characterize devices in volume quantities. However, different levels of impedance mismatch might result with each device tested. This means that power measurements made by the same tester might vary from device-to-device. These tester-to-tester and device-to-device variations can lead to inconsistent power measurements, which are undesirable in mass production environments.
We have also recognized that it can be both cumbersome and costly to incorporate an external power sensor into a test system.
It would therefore be desirable to have a tester that can perform power measurements with less measurement uncertainty. Such a tester would therefore be able to measure power with greater accuracy and give a clearer indication of the performance of RF/microwave devices. It would also be desirable to have a tester for RF/microwave devices that is easier and less costly to manufacture.
SUMMARY OF THE INVENTION
With the foregoing background in mind, it is an object of the invention to provide a tester for testing and characterizing RF/microwave devices.
Another object of the invention is to provide a tester that performs power measurements with increased accuracy.
Still another object of the invention is to provide an easy way to account for tester-to-tester and device-to-device variations while performing power measurements.
Yet another object of the invention is to provide a tester for testing and characterizing RF/microwave devices that is easier and less costly to manufacture.
The foregoing and other objects are achieved in a tester having an integrated power sensor module including a power sensor and a plurality of programmable storage devices. The storage devices are programmed with mismatch data relating to the power sensor.
In a preferred embodiment, the power sensor module is plugged into a tester, thereby switchably connecting the module to one of a plurality of measurement channels.
According to one feature, the storage devices are programmed with reflection coefficients for the power sensor.
According to another feature, the plurality of programmable storage devices is implemented using a plurality of EEPROM's.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.


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Giga-tronics,Series 8540B Universal Power Meters, pp. 4-1 through 4-13.

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