Agilent Technologies E7401A, E7402A, E7403A, E7404A, E7405A Measuring Signal-to-Noise

Chapter 1 49

Making Basic Measurements

Measuring Signal-to-Noise

Measuring Signal-to-Noise

The signal-to-noise measurement procedure below may be adapted to

measure any signal in a system if the signal (carrier) is a discrete tone.

If the signal in your system is mod ulated, it will be necessary to modify

the procedure to correctly measure the modulated signal level

In this example the 50MHz amplitude reference signal is used as the

fundamental source. The amplitude reference signal is assumed to be

the signal of interest and the internal noise of the analyzer is m easured

as the system noise. To do this, you will need to set the input attenuator

such that both the signal and the noise are well within the calibrated

region of the display.

Signal-to-Noise Measurement Example:

Perform the steps below to measure the signal-to-noise.

1. Perform a factory preset by pressing Preset, FactoryPrese t (if

present).

2. Turn on the internal 50 MHz amplitude re fe re n c e signal of the

analyzer as follows:

•For the E7401A, use the internal 50MHz amplitude reference

signal of the analyzer as the signal being measured. Press

Input/Output, Amptd Ref (On).

•For all other models connect a cable between the front-panel

AMPTD REF OUT to the analyzer INPUT, then press

Input/Output, Amptd Ref Out (On).

3. Set the center frequency to 50MHz by pressing FREQUENCY,

Center Freq, 50, MHz.

4. Set the span to 1MHz by pressing SPAN, Span, 1, MHz.

5. Set the Y-Axis Units to dBm by pressing AMPLITUDE, More,

Y-AxisUnits, dBm.

6. Set the resolution bandwidth to spectrum analyzer coupling by

pressing BW/Avg, Res BW (SA).

7. Set the reference level to –10dBm by pressing AMPLITUDE, RefLevel,

–10, dBm.

8. Set the attenuation to 40dB by pressing AMPLITUDE, Attenuation, 40,

dB.

9. Press Peak Search to place a marker on the peak of the signal.

10.Press Marker, Delta, 200, kHz to put the delta marker in the noise at

the specified offset, in this ca se 200 kHz.

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: