Agilent Technologies E7401A, E7402A, E7403A, E7404A, E7405A Measuring Low Level Signals Example 4:

Chapter 1 39

Making Basic Measurements

Measuring Low Level Signals

NOTE The video bandwidth must be set wider than the resolution bandwidth

when measuring im pulse noise levels.

Figure 1-31 Decreasing Video Bandwidth

Measuring Low Level Signals Example 4:

If a signal level is very close to the noise floor, video averaging is

another way to make the signal more visible.

NOTE The time required to construct a full trace that is averaged to the

desired degree is approximately the same when using either the video

bandwidth or the video averaging technique. The video bandwidth

technique completes the averaging as a slow sweep is taken, whereas

the video averaging technique takes many sweeps to complete the

average. Characteristics of the signal being measured, such a s drift and

duty cycle, determine which technique is appropriate.

Video averaging is a digital proce s s in w hich each trace point is

averaged with the previous trace-point average. Selecting Average Type,

Video Avg and Average (On) changes the detection mode from peak to

sample. The result is a sudden drop in the displayed noise level. The

sample mode displays the instantaneous value of the signal at the end

of the time or frequency interval represented by each display point,

rather than the value of the peak during the interval. Sample mode is

not used to measure signal amplitudes accurately because it may not

find the true peak of the signal.

Video averaging clarifies low- l evel signals in wide bandwid t h s b y

averaging the signal and the noise. As the analyzer takes sweeps, you

can watch video averaging smooth the trace.

Contents

Main Signal Analysis Measurement Guide Agilent Technologies EMC Series Analyzers Notice Safety Information Warrant y LIMITATION OF WARRANTY EXCLUSIVE REMEDIES Where to Find the Latest Informa tion Page Contents Page What is in This Chapter Test Equ ipm ent Comparing Signals Signal Comparison Example 1: Page Signal Comparison Example 2: Page Resolving Signals of Equal Amplitude Resolving Signals Example: Page Page Resolving Small Signals Hidden by Large Signals Resolving Signals Example: Page Page Making Better Frequency Measurements Better Frequency Measurement Example: Page Decreasing the Frequency Span Around the Signal Decreasing the Frequency Span Example: Page Page Tracking Drifting Signals Tracking Signal Drift Example 1: Page Page Tracking Signal Drift Example 2: Page Page Page Measuring Low Level Signals Measuring Low Level Signals Example 1: Page Measuring Low Level Signals Example 2: Measuring Low Level Signals Example 3: Page Measuring Low Level Signals Example 4: Page Page Identifying Distortion Products Distortion from the Analyzer Identifying Analyzer Generated Distortion Example: Page Page Third-Order Intermodulation Distortion Identifying TOI Distortion Example: Page Page Page Measuring Signal-to-Noise Signal-to-Noise Measurement Example: S/N 70 dB/Hz10 30 kHz()log+ 25.23 dB30 kHz()== Making Noise Measurements Noise Measurement Example 1: Page Page Page Page Noise Measurement Example 2: Noise Measurement Example 3: Page Page Demodulating AM Signals (Using the Analyzer As a Fixed Tuned Receiver) Demodulating an AM Signal Example 1: Page Page Page Page Page Demodulating FM Signals Demodulating a FM Signal Example: Page Page Page Page Whats in This Chapter Required Test Equipment Making Stimulus Response Measu rements What Are Stimulus Response Measurements? Using An Analyzer With A Tracking Generator Stepping Through a Transmission Measurement Page Page Page Page Tracking Generator Unleveled Condition Measuring Device Bandwidth Page Page Measuring Stop Band Attenuation Using Log Sweep Page Page Page Page Making a Reflection Calibration Measurement Example: Reflection Calibration Measuring the Return Loss Chapter 2 87 VSWR 110 Making Complex Measurements Making a Reflection Calibration Measurement -----------------------= Table 2-1 Power to VSWR Conversion + 110 Demodulating and Listening to an AM Signal Demodulating and Listening to an AM Signal Example 1: Demodulating and Listening to an AM Signal Example 2: