Spectrum Analyzer

This section covers the functions of Spectrum Analysis and Spectrum Analyzer measurements.

 

Power Input

This function is used to determine the total power input into a spectrum analyzer, radio or noise figure meter. It is used to make sure that the receiver is not overloaded with noise power and operating outside it’s dynamic range. Input the Temperature in Kelvin, Bandwidth in Hertz, ENR Excess Noise Ratio of Hot/Cold noise source, PreAmp Gain, DUT Device Under Test Noise Figure in dBF and Gain in dB. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

 

Figure 57 – Spectrum Analyzer Input Power

 

Threshold/MDS

This function is used to determine the Threshold or Minimum Detectable Signal MDS. It is used to make sure that the signal is detectable. Input the Temperature in Kelvin, Bandwidth in Hertz, Noise Figure of Receiver in dBF, Singal Level in dBm and Noise Level in dBm. The output is the Minimum Detectable Signal in dBm. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

 

Figure 58 – Spectrum Analyzer Threshold/ Minimum Detectable Signal

 

EbNo-S/N

This function is used to determine the Eb/No to Signal to Noise Levels. Input the Eb/No ratio or the Signal to Noise S/N ratio, the Data Rate in Bits/Sec and the Channel Bandwidth. The Eb/No or the S/n ratio that is not input will be calculated. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

 

Figure 59 – Spectrum Analyzer Eb/No to S/N

 

Swp Time

This function is used to get a rough estimate of the Spectrum Analyzer sweep time for a trace to complete.  Enter the RBW- Resolution Bandwidth, the VBW – Video Bandwidth, the Span all in Hertz and the constant of choice. The output is an approximate sweep time for the spectrum analyzer. The constant can be determined for a spectrum analyzer by estimating backward to refine the value. I defaulted to the one most used for Agilent Analyzers.  Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

Figure 60 – Spectrum Analyzer Sweep Time

 

Pwr Avg SN/N

This function set is to calculate the Power Average of Signal and Noise to Signal/Noise. There are two functions, one absolute and the other relative. For the left one add the Signal + noise level and the Noise Level all in dBm/Hz. In the other function, enter the signal Delta (i.e. Signal and Noise to Noise Level delta). In either case it will figure the signal error due to the added noise contribution. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

 

Figure 61 - Spectrum Analyzer Power Average SN/N Error

 

Log Avg SN/N

This function set is to calculate the Logarithmic Average of Signal and Noise to Signal/Noise. The function requires the Signal and Noise Level in dBm, the Delta Signal + Noise to Noise Level. It will figure the CW Corrected signal level and  CW signal error due to the added noise contribution. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

Figure 62 - Spectrum Analyzer Log Average SN/N Error

 

Intermod

Intermod Order

This section is used to calculate the appropriate Inter-Modulation Level. Select the desired Inter-modulation order that you wish to calculate and enter the Fundamental and IM Product levels in dBm. The Intermod level of that order is calculated for the device. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

 

Normalize Unequal Power

This section calculates the Normalized power of two unequal level signals used in the adjoining Intermod Level calculations. Enter signal levels 1 and 2 and press “Calculate” to perform and “Clear” to clear values and start over. Press “Close” to quit the screen.

 

Figure 63 – Spectrum Analysis Intermod Order and Normalize Unequal Power

 

DANL/NF + BW

This function set calculates the Noise Figure in dBF, the DANL/ANL Displayed Average Noise level or Average Noise Level and the Tangential Sensitivity. Enter the Temperature in Kelvin, the bandwidth in Hertz and one of the three values of  DANL, Noise Figure or Tangential Sensitivity. It will compute the missing factor.

 

Displayed Average Noise Level

If the DANL/ANL check box is checked it computes to/from DANL and unchecked it computes to/from ANL. In the case below I entered the temperature, bandwidth and checked the DANL box and entered the DANL of –88dBm/Hz. It calculated the Noise figure and Tangential Sensitivity of the receiver. Press “Calculate” to run and “Clear” to clear and start over and “Close” to quit screen.

Figure 64 - Spectrum Analyzer DANL/NF and TSS

 

Average Noise Level Calculation

Here I entered an ANL of –120dBm/Hz, 290K, 1KHz Bandwidth and unchecked the box. It calculated the Noise Figure and TSS. Also could have entered in either the TSS or the Noise Figure instead of the ANL and it would have figured the other two.

 

Figure 65 – Spectrum Analyzer ANL/NF and TSS

Crest Factor

Crest factor is a measure of the signal cresting due to random modulation variations and the probabilities of them adding Fourier series manner to product above average peaks of instantaneous peaks in the signal range. Enter any two of the three values and press “Calculate” to compute the remaining value. Press “Close” to quit the screen or “Clear” the empty the cells to try new values.

Figure 66 – Spectrum Analyzer Crest Factor

 

PDF

Line Spectrum

Pulse Desensitation Factor or PDF is the determining of or using the pulsed duty cycle power average offset that can be applied to help determine signal measured levels from pulsed signals. For the line spectrum enter any two of the three values Time On, Time Period and/or PDF to calculate the missing component. The PDF is the decibel offset that can be added to a CW signal level to correct to what it would measure in a power-integrating sensor as the pulsed average power.

Envelope Spectrum

This one uses any three of the four inputs to calculate the missing value. It will take the Time On, “K” constant factor, the Bandwidth and/or finally the PDF.

 

Enter any two of the three values on the right function and/or any three of the four inputs on the right side function and press “Calculate” to compute the remaining value. Press “Close” to quit the screen or “Clear” the empty the cells to try new values.

 

Figure 67 – Spectrum Analyzer PDF

 

Two Tone

This screen helps the operator to compute all the second and third order Intermodulation components of mixed signals and the mixing products. Enter Fund1 and Fund2 values in Hz, KHz, MHz, GHz etc. The units on the calculator being Hz, will scale units to whatever you wish. Press “Close” to quit the screen or “Clear” the empty the cells to try new values.

 

Figure 68 – Spectrum Analyzer Two Tone

 

Bandwidth Correction

Channel Power RBW

This calculator screen has several functions. The first is to calculate Span, Points and/or RBW Resolution Bandwidth. Using the Spectrum Analyzer constant of computation (bandwidth integration factor) it will take two of the three variables Span, Points and/or RBW Resolution Bandwidth and compute the missing variable. Press the “Calculate” button on the left to compute this function.

 

Bandwidth Correction

This function can be used to compute either the bandwidth offset or the converted signal integrated power based on the signal and the bandwidth of integration of that signal. Note assumes flat bandwidth frequency response of the range of integration. Press the “Calculate “button on the right to compute this function. Press “Close” to quit the screen or “Clear” the empty the cells to try new values.

Figure 69 – Spectrum Analyzer Bandwidth Correction