Agilent Technologies E8267C PSG Manual de usuario descargar pdf (Pagina 12)

Analog Test Stimulus Versus Vector Test Stimulus

The following points summarize the main benefits, as well as the drawbacks, associated

with employing the conventional analog approach versus the new vector approach to

generate a multitone test stimulus. Both methods can be used to generate a multitone

signal, however there are many advantages to using a vector approach as discussed below.

While there are many advantages, there are also some new measurement challenges

introduced when using a vector approach to generate a multitone test stimulus. They are

highlighted below and should be kept in mind when performing distortion measurements

using the vector approach.

Why use conventional analog stimulus technique?

Well-established test procedure – Summing signals from multiple CW signal generators

has traditionally been required to achieve a multitone test stimulus. This is a common

test procedure that can be performed using standard off-the-shelf test equipment and

accessories.

Issues with analog technique

Complicated test setup – Although the test stimulus is achieved using standard test

equipment, the hardware setup is somewhat complicated considering the number of

instruments required to generate the test stimulus. Because of the complex instrument

configuration, setting up the equipment to perform the nonlinear distortion measurements

consumes the majority of the test time.

Signal parameters not easily modified – Because independent signal generators produce

each tone, adding or removing tones requires hardware modifications to the test setup.

Once setup, manual tuning of frequency and tone power is also required for each signal

generator.

Difficult to generate random phase sets – Most CW signal generators do not provide the

ability to systematically set the phase of the signal. As a result, it is difficult to generate

random phase sets using the traditional analog approach.

High cost of test – Because of the multi-instrument test setup and the time required to

perform the measurement, the analog approach has a high overall cost of test. As more

tones are added to the test stimulus, the capital equipment cost and time of test increases.

Why use vector stimulus technique?

Simplify test procedure – Now, setting a few basic waveform parameters in the PSG

vector signal generator user interface is all that is required to create custom two-tone

and multitone IMD test signals.

Control signal parameters – Enable and disable tones at will and easily modify common

signal parameters like relative tone spacing and power. Also set fixed or random initial

phase distribution with digital accuracy.

Repeatable test setup – The first step to achieving repeatable test results is finding a

repeatable test stimulus. With vector techniques, test waveforms can be easily stored

and quickly recalled for playback ensuring that the DUT is subjected to an equivalent test

signal every time.

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Agilent Technologies E8267C PSG Manual de usuario Pagina 12