Laboratory

1

Spectrum Analyzer

Fall 2017

TLEN 5380 Wireless Systems

This Lab introduces spectrum analyzer operations and miscellaneous additional laboratory equipment and procedures.

Lab-01 Spectrum Analyzer Introduction:

Spectrum Analyzer: Measures the magnitude of an input signal versus frequency.

The primary use is to measure the power of the spectrum of known and unknown signals

The input signal is electrical (volts)

The display of a spectrum analyzer has frequency on the horizontal axis and amplitude displayed on the vertical axis.

By analyzing the spectra of electronic signals, the dominant frequency, power, distortion, harmonics, bandwidth, and other spectral components of a signal can be observed that are not easily detectable in time domain waveforms.

In contrast, an oscilloscope allows observation/measurement of constantly changing signal voltages usually as a two-dimensional plot of one or more signals as a function of time.

Equipment

Function Generator: A function generator is used to generate repetitive waveforms based on electrical concepts. Most function generators are capable of producing sine waves, square waves, and triangle waves. In this lab, the function generator will be used to generate AC output in a sine wave, the same as a carrier signal for a traditional telecommunications connection.

Agilent 33120A 15 MHz Function/Waveform Generator

Spectrum Analyzer: A spectrum analyzer is used to display a graphic representation of the

spectral components of a frequency. The range of frequencies it represents can be adjusted, allowing inspection of a wide range of frequencies. It can also be used to find peaks in the spectrum, or strong frequencies and sidebands

Agilent (Keysight Technologies) N9344C Handheld Spectrum Analyzer (HSA)

Cables and Connectors: Used to connect the voltage source (input) to the analysis equipment (the spectrum analyzer). For this lab, one particular type of unique connecter is used: a Bayonet

Neill-Concelman (BNC) (also known, most sources agree erroneously, as a British Naval Connector).

Lab-01 Exercises

Procedure

1. Generate a baseband signal of 15 MHz, with 5 Vpp amplitude, by following these steps:

Turn on the power on the Agilent function generator. Ensure you are on

frequency view by pressing FREQ button. The frequency will now show in the

display window.

Change the frequency by either rotating the dial or entering the following sequence-ENTER NUMBER, the appropriate number keys (which share their button with other functions), and the unit KHz, MHz, etc.). Frequency is now set.

Switch to the amplitude view, by pressing AMPL. The amplitude of the baseband signal is now shown in the same window as frequency was. Adjust the amplitude by either rotating the dial, or entering the desired number (ENTER NUMBER, appropriate number keys-in this case 5, and MHz/Vpp).

Your baseband signal function generator should now be generating a signal whose form is that of sine wave of 15 MHz frequency with 10V peak-to-peak amplitude. Ensure you are satisfied this is the case by using the FREQ and AMPL keys to double-check the frequency and amplitude.

Vrms and Vpp.

2. Attach a 2500 MHz antenna to the handheld spectrum analyzer.

Review the Demo-Guide to understand how to (a) record a spectrum sweep/trace; and (b) how to copy the saved sweep/trace file to a USB device.

Set the spectrum analyzer to perform a sweep of the unlicensed 2.4 GHz band. Specify your location in the room where the sweep information was acquired on some sort of topological (floorplan) graphic. Save the sweep information, transfer to USB, and include the information as Sweep-1 in your report. Different groups have wish to sweep the room at different baseline locations.

Inspect DLC-1B20 to determine what other wireless access points (A.P.s) are physically located in the room. For each A.P., power down the A.P. and re-sweep the 2.4 GHz band at the same location in DLC-1B20. Save the successive sweeps as Sweep-2, Sweep-3, etc. Repeat until all access points in DLC-1B20 are turned off.

Turn in a lab report that summarizes the 2.4 GHz emissions in DLC-1B20 including graphs. For each graph, identify the band swept, room location, and any high-level observations.

2017 TLEN 5830 Wireless SystemsLab-01 Spectrum Analyzer Page 4 of 4