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Rohde & Schwarz FSMR, User Manual

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Rohde & Schwarz FSMR User Manual Download Page 15

FSMR Measurement 

Examples 

1166.3311.12-01 1.13 

E-1 

Example 3: AM Modulation and Modulation Distortion Measurements 

Measurement  

The FSMR includes a modulation analyzer. Measurements like AM, FM or PM modulation will be 
performed in the modulation analyzer mode. The instrument offers standard measurements like 
modulation depth, deviation and modulation frequency, but also more sophisticated function like 
modulation distortion or audio frequency response are available. 
 

Main Receiver Functions 

The modulation analyzer functions are available in the Measuring Receiver 

DEMOD

-mode. All required 

settings and evaluations can be reached from the DEMOD main menu. 
 

Measurement Setup 

Fig.1-9 

AM modulation measurement setup 

 
The following settings are used on the generator: 

1. 

PRESET 

the generator. 

2.  Set RF Frequency to 100 MHz. 
3.  Set the output level to - 30 dBm. 
4.  Select the AM Modulation, 30% modulation depth. 
5.  Set the Modulation frequency to 1 kHz. 

 

Measurement Sequence – AM Modulation Measurements 

Connect the Signal Generator output with the Measuring Receiver RF Input. 
 
The following measurement steps are performed: 
 

1.  Measure the AM modulation depht. 
2.  Relative Audio measurements 
3.  Measure the Total harmonic distortion in %. 

 

Summary of Contents for FSMR

Page 1: ...th the Measuring Receiver R S FSMR Product Note This product note provides information about the basic measurement setups Measurement examples show the practical realisation of measurements like RF Power Tuned RF Level and Demodulation Some hints for low power measurement are given ...

Page 2: ...urements 1 4 Example 2 Low RF Level Measurements with Tuned RF Level Mode 1 7 Measurement 1 7 Main Receiver Functions 1 7 Measurement Setup 1 7 Measurement Sequence Tuned RF Level Measurements 1 7 Example 3 AM Modulation and Modulation Distortion Measurements 1 13 Measurement 1 13 Main Receiver Functions 1 13 Measurement Setup 1 13 Measurement Sequence AM Modulation Measurements 1 13 Example 4 Aud...

Page 3: ...ance spectral analysis capabilities The R S FSMR still offers an easy to use operation which does not require expert knowledge to perform the basic measurements This product note is designed to explain the functions and operation of the Measuring Receiver R S FSMR In the following descriptions each step is explained in detail so that the instrument can be immediately used without the need for lear...

Page 4: ...setup menu is opened Press the menu change key NEXT The submenu is opened Press the PRESET RECEIVER softkey The following presets will force the instrument into the Measuring Receiver mode FILE STARTUP RECALL 2 Define the Startup Recall Press the FILE key The file menu is displayed In the FILE menu press the STARTUP RECALL softkey A table with available instrument recall states is displayed In the...

Page 5: ...amplifier Preamp Off Demodulation Demod FM Detector Det peak 2 Measurement time Meas Time 100 ms Trigger Trigger Free run Measurement Examples All of the following examples assume the standard settings for the measuring receiver These are set with the PRESET key The described measurement applications are Measurement of the RF power of a signal using the Power Meter mode Measurement of low level si...

Page 6: ... 100 mW o R S NRP Z55 DC to 40 GHz 1 uW to 100 mW Main Receiver Functions The power meter functions are available in the Measuring Receiver POWER METER mode All required settings and evaluations can be reached from the POWER METER main menu Measurement Setup Fig 1 2 RF Power measurement setup The following settings are used on the generator 1 PRESET the generator 2 Set RF Frequency to 1 GHz 3 Set ...

Page 7: ...requency menu press the RECEIVER FREQUENCY softkey The frequency entry is displayed Enter the measuring frequency with the number keys and the appropiate unit key The frequency will be used by the instrument to calculate the calibration factors for the power sensor head In the RECEIVER FREQUENCY entry window key in 1000 MHZ PWR METER ZERO Zero the power sensor Press the PWR METER hotkey The power ...

Page 8: ...nnect the power sensor to the signal generator RF output PWR METER DISPLAY LOG LIN Linear display Change the Unit to Watt Press the PWR METER hotkey The POWER METER menu is displayed In the POWER METER menu press the DISPLAY LOG LIN softkey The RF power unit is changed from dB to Watt Fig 1 4 RF power measurement in UNIT Watt ...

Page 9: ... calibration procedures in the Tuned RF Level mode The following example will guide through the calibration steps All functions for Tuned RF level measurements can be reached from the RF LEVEL main menu Measurement Setup Fig 1 5 Tuned RF Level measurement setup The following settings are used on the generator 1 PRESET the generator 2 Set RF Frequency to 300 MHz 3 Set the output level to 0 dBm Meas...

Page 10: ...h the number keys and the appropiate unit key In the RECEIVER FREQUENCY entry window key in 300 MHZ Connect the power sensor to the signal generator RF output RF LEVEL CAL ABS POWER Calibrate the Tuned RF Level Absolute Power calibration Press the RF LEVEL hotkey The RF LEVEL menu is displayed In the RF LEVEL menu press the CAL ABS POWER softkey The calibration of the receiver will be performed A ...

Page 11: ...appear at levels about 10 dBm This is the point where the automated Range to Range calibration can be performed RF LEVEL RECAL The FSMR is now ready for a RF level range change The calibration of the level difference due to the range change will be performed Press the RF LEVEL hotkey The RF LEVEL menu is displayed In the RF LEVEL menu press the RECAL softkey The RECAL procedure is performed Do not...

Page 12: ...nu is displayed In the RF LEVEL menu press the RECAL softkey The RECAL procedure is performed A message box appears The instrument will perform a measurement in the calibrated range then change the RF settings RF attenuator IF gain and then measure again After the recalibration measurements with high accuracy are available in the RF level range 3 covers levels from 50 dBm to noise level The FSMR i...

Page 13: ...nly depending on the measurement time A longer acquisition of the signal does allow for a more accurate measurement The averaging of several single acquisitions will lead to an effective longer measurement time Press the RF LEVEL hotkey The RF LEVEL menu is displayed In the RF LEVEL menu press the AVERAGE softkey The AVERAGE will be switched on The number off measurements can be entered in the AVE...

Page 14: ...frequency entry is displayed Enter the measuring frequency with the number keys and the appropriate unit key In the RECEIVER FREQUENCY entry window key in 100 MHZ DETECTOR WIDE The measurement of an unstable signal requires the measuring receiver to use a wide bandwidth The FSMR offers a wideband detector mode to acquire wideband signals with high accuracy In the RF LEVEL menu press the DETECTOR W...

Page 15: ...n analyzer functions are available in the Measuring Receiver DEMOD mode All required settings and evaluations can be reached from the DEMOD main menu Measurement Setup Fig 1 9 AM modulation measurement setup The following settings are used on the generator 1 PRESET the generator 2 Set RF Frequency to 100 MHz 3 Set the output level to 30 dBm 4 Select the AM Modulation 30 modulation depth 5 Set the ...

Page 16: ... of the screen The upper window shows the RF Frequency and the RF input level FILTER LOW PASS 15 KHZ Limiting the bandwidth Audio Filters Press the DEMOD hotkey The analog demodulation menu is displayed In the DEMOD menu press the FILTER softkey The audio filter menu is displayed To suppress unwanted broadband noise or harmonics of the demodulated signal the bandwidth of the measurement can be lim...

Page 17: ...nt value of the detector will be saved as a reference value and the result display will change to a relative reading indicated with K 0 00 Change the modulation frequency to 50 kHz The following settings are used on the generator 1 Select the AM Modulation 50 kHz modulation frequency RELATIVE RELATIVE DB Relative display Change the Unit to dB Press the DEMOD hotkey The analog demodulation menu is ...

Page 18: ...MS and Average detectors are the best choice for measuring noise and residual modulation The THD SINAD detector measure the distortion of the demodulated audio signal All detectors can be used in parallel In the DETECTOR SELECTION menu press the THD SINAD softkey AMPT UNIT THD UNIT DB Total Harmonic Distortion Change the Unit to Press the AMPLITUDE hardkey on the frontpanel The amplitude settings ...

Page 19: ...Receiver AUDIO mode All required settings and evaluations can be reached from the AUDIO main menu Measurement Setup Fig 1 13 Audio measurement setup Connect the signal generator LF low frequency output with the FSMR Audio input The following settings are used on the generator 1 PRESET the generator 2 Set LF output to ON 3 Set the LF output level to 1 volt 4 Set the LF output frequency to 1 kHz Mea...

Page 20: ...ngs like frequency is required Fig 1 14 Audio measurement after Preset Mode Audio AUDIO RESULT ABS REL 4 Relative Audio measurements Press the AUDIO hotkey The audio menu is displayed In the AUDIO menu press the RESULT ABS REL softkey The relative measurement function is enabled The actual measurement value of the detector will be saved as a reference value and the result display will change to a ...

Page 21: ... the signal the bandwidth of the measurement can be limited with higpass and lowpass filters In the FILTER menu press the LOW PASS 15 KHZ softkey Change the LF output frequency to 15 kHz The following settings are used on the generator Set the LF output frequency to 15 kHz The audio frequency is now changed to the bandwidth of the active 15 kHz low pass filter In the following measurement the freq...

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