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54 N9069C Noise Figure Measurement Guide

Measurement Related Tasks and Concepts
Setting the Measurement System

Double Sideband Measurements

Double Sideband (DSB) measurements can only be made when the DUT is a

downconverter, or when the system downconverter is On. DSB techniques can

be useful when making noise figure measurements under the following

conditions:

— When adequate filters for image-free SSB measurements are not available
— When frequency ranges have to be covered that make SSB filters

impractical or impossible

DSB measurements do not eliminate the need for filtering. However, they can

greatly simplify the filtering needed. This benefit is achieved by effectively

averaging the LSB and USB results and averaging the ENR values. This results

in a loss of frequency resolution and accuracy.

Figure 3-3

Double Sideband Measurements

Figure 3-3

shows a double sideband, downconversion, mixing. Noise from two

separated RF bands are mixed into the IF band, where the power addition

takes place.
DSB measurements are made with the noise from a pair of separate bands,

symmetrically arranged about the LO frequency. The IF value should be low,

ideally no larger than 1% of the LO frequency. As the two sidebands, the USB

and the LSB, are generated at frequencies equal to F

±F

, this technique

maintains the two bands close together. This is necessary because the

assumption is made that the variations in the noise source ENR, gain and noise

figure are constant between the two bands. ENR values are applied to the

mid-point between the upper and lower sidebands, and this equates to the

frequency of the LO.

X-Series Input

Band

LSB Input

USB Input

Amplitude

Frequency

-F

LSB

mixing

USB

-F

mixing

Содержание CXA N9000B

Страница 1: ...ure Measurement Guide Keysight X Series Signal Analyzers This manual provides documentation for the following models N9040B UXA N9030B PXA N9020B MXA N9010B EXA N9000B CXA N8973B NFA N8974B NFA N8975B...

Страница 2: ...U S government customers under its standard commercial license which is embodied in its End User License Agreement EULA a copy of which can be found at http www keysight com find sweula The license se...

Страница 3: ...com find N9010B http www keysight com find N9000B http www keysight com find N8973B To receive the latest updates by email subscribe to Keysight Email Updates at the following URL http www keysight c...

Страница 4: ...4...

Страница 5: ...cedure 23 Calibration of the Measurement Setup 25 Making the Corrected Noise Figure and Gain Measurement 27 Making Multi stage Converter Measurements 28 Measurements with a System Downconverter 28 Mea...

Страница 6: ...l Oscillator 57 Calibrating the Analyzer 58 Corrected Measurements 58 When to Perform Calibration 59 Interpolated Results 59 Calibration Indicator 59 Interpolated Calibration 59 User Cal vs Internal C...

Страница 7: ...LO to List 77 Setting up DUT LO or System Downconverter LO 77 Using Loss Compensation 78 Examples where Loss Compensation is applied 78 Configuring Fixed Loss Compensation 79 Creating a Loss Compensat...

Страница 8: ...8 Contents...

Страница 9: ...y control the noise figure of the overall system Once the noise figure is known system sensitivity can be estimated from the system bandwidth Noise figure is often the key parameter that differentiate...

Страница 10: ...lated using the following equation Equation 1 1 This equation is the basis for the noise figure measurement The noise figure and gain of the DUT are measured in the process Figure 1 1 Noise Figure Mea...

Страница 11: ...followed by the instrument stage 2 The analyzer makes another two measurements with the noise source ON and OFF respectively In the measurement if the DUT has gain the measurement with the noise sourc...

Страница 12: ...displayed The measurement includes the following functionality Layout data views Graph Meter and Table Result types including Noise Figure Noise Factor Gain Y Factor Effective Temp Phot and Pcold DUT...

Страница 13: ...n basic measurements and frequency converter measurements respectively and then talks about the procedure to calculate measurement uncertainty for noise figure measurements The following topics are co...

Страница 14: ...re listed in the following table This example sets a frequency range of interest of 200 MHz to 400 MHz The purpose of the measurement is to verify the specified table results are as stated over the fr...

Страница 15: ...for the calibration you need to apply Loss Compensation to compensate for any loss caused by the connector s removal if you need improved accuracy Using Loss Compensation on page 78 has an explanation...

Страница 16: ...frequency parameters of the measurement Press FREQ Freq Mode and select Swept Press Start Freq and enter 200 MHz Press Stop Freq and enter 400 MHz Press Points and enter 11 6 Select the ENR Mode Pres...

Страница 17: ...ibration Press CALIBRATE You will be asked to confirm the calibration See the following figure for results after calibration With the calibration completed and no device under test inserted both gain...

Страница 18: ...ve either a High Band Preamp or an external preamp and you are calibrating above 3 6 GHz the calibration data will vary significantly Measurements made with this calibration data might be valid but on...

Страница 19: ...ng figure is displayed Refer to Displaying the Measurement Results on page 82 for more details about viewing measurement results The results show the DUT has an average noise figure of 2 72 dB an aver...

Страница 20: ...a noise figure measurement on a downconverter which is upper sideband The specifications for the DUT are listed in Table 2 2 on page 22 The LO is set to sweep in a frequency range and the IF is fixed...

Страница 21: ...ack of the X Series analyzer In this section a Keysight SNS series noise source is used as an example External LO control is used to control a signal generator to supply an LO at a frequency range of...

Страница 22: ...SETUP DUT Setup Calibration Table 2 2 DUT Setup Table Freq Mode Swept Frequency Context RF This determines whether you specify the measurement frequencies at the DUT input RF or at the analyzer s inpu...

Страница 23: ...ress the power key To obtain optimum measurement accuracy it is recommended the analyzer warm up for 30 minutes 2 Select the mode and measurement Press MODE MEAS Noise Figure OK 3 Preset the mode Pres...

Страница 24: ...on page 77 7 Configure DUT LO Setup On the Select dialog press Ext LO Setup Press DUT LO Setup In the LO Settings area of the dialog enter the following values LO Power 7 0 dBm Min Freq 250 kHz Max Fr...

Страница 25: ...libration you will have to recalibrate the measurement Connect the noise source and analyzer for calibration See Figure 2 3 Note that you need to connect any After DUT filtering prior to calibration 9...

Страница 26: ...ation range for calibration and set the internal attenuation for the measurement if needed 2 Configure the amplitude parameters Press AMPTD select the Attenuation tab and set the value used in the mea...

Страница 27: ...made Insert the DUT into the system as shown in Figure 2 3 on page 21 A graphic display of noise figure and gain is shown in Figure 2 4 Press View Display Table to display the table view see Figure 2...

Страница 28: ...ements with a System Downconverter A system downconverter can be thought of as a frequency extender for the analyzer to allow measurements to be made on DUTs at frequencies that the analyzer does not...

Страница 29: ...lyzer and make your measurements Step Notes 1 Turn the analyzer on 2 Press MODE MEAS Noise Figure OK Mode Preset to return the analyzer to a known state 3 Enter the ENR values into the analyzer if req...

Страница 30: ...ion between the sidebands and thus get the optimum resolution possible When making Double Sideband DSB measurements it is important that the IF is much lower in frequency than the LO frequency This is...

Страница 31: ...ensation should be set by pressing Meas Setup Loss Comp tab Loss After DUT Loss Comp Mode Fixed Fixed Loss 3 dB For microwave measurements above 3 6 GHz the analyzer s input filter will reject LO leak...

Страница 32: ...quirements The filter needed to make SSB measurement could be part of the DUT or a measurement specific filter must be obtained and applied at the input to the system downconverter Analyzer Input LSB...

Страница 33: ...ements The bandwidth of the SSB filter limits the maximum frequency range over which a measurement can be swept Therefore SSB measurements are not suited to very wideband DUTs Filtering is needed to s...

Страница 34: ...de the analyzer itself the noise source and the DUT The Noise Figure Measurement Application provides a measurement uncertainty calculator to calculate the RSS root sum square measurement uncertainty...

Страница 35: ...om the instrument automatically You can also change these types to Manual and enter the corresponding parameters manually 3 If you are using a Keysight SNS noise type go to step 4 directly If you are...

Страница 36: ...ncalibrated For more information about user cal and internal cal you can refer to User Cal vs Internal Cal on page 59 The Noise Figure Uncertainty 2 area shows uncertainty results for the current sett...

Страница 37: ...figure measurement depends on the DUT gain and instrument noise figure The data is derived using the Uncertainty Calculator in the N9069C noise figure measurement application It can be seen that the...

Страница 38: ...USB ports the analyzer will consider it to be in the RF input signal path and will apply the gain settings and other calibration data of the USB preamplifier to the measurements Therefore adding pream...

Страница 39: ...onfiguration Updating Message 2 The USB preamplifier s calibration data such as gain noise figure and S parameters will be automatically downloaded into the analyzer 3 The Ready LED is lit on the USB...

Страница 40: ...4 Signal Analyzer Display after USB Preamplifier is Ready For Use 5 The USB preamplifier is ready for use When the instrument is in the Noise Figure mode and the external U7227 Series USB preamplifier...

Страница 41: ...the USB preamplifier before the internal preamplifier before the input mixer To make an accurate noise figure measurement the noise power should be below the maximum allowable power at all these thre...

Страница 42: ...t noise power calculation in different stages of the test system refer to Calculating the Noise Power into Different Stages of the Noise Figure Measurement System on page 85 Before using Figure 2 16 a...

Страница 43: ...to top and find an approximate place for them 4 Find the corresponding system configuration If the system configuration includes the internal attenuation do the following to find the proper attenuatio...

Страница 44: ...ent Guide Making Noise Figure Measurements Using the U7227 Series USB Preamplifiers in Noise Figure Measurements Figure 2 16 Supported DUT Characteristics and Recommended Test System Configuration for...

Страница 45: ...Series can support up to 50 GHz The calculation method for frequency ranges above 26 5 GHz is similar to the 3 6 GHz to 26 5 GHz frequency range The supported DUT gain will decrease because of the in...

Страница 46: ...tested and measured on an operating temperature of 23 C Specification U7227A U7227C U7227F Frequency 10 MHz to 4 GHz 100 MHz to 26 5 GHz 2 to 50 GHz Gain dB b b F signifies frequency in GHz 16 10 to 1...

Страница 47: ...Internal Preamp Internal Attenuator DUT with Frequency Ranges above 3 6 GHz The DUT characteristic is as below DUT NF 4 dB DUT gain 25 dB Frequency range 3 to 10 GHz The DUT bandwidth is Hz The bandwi...

Страница 48: ...48 N9069C Noise Figure Measurement Guide Making Noise Figure Measurements Using the U7227 Series USB Preamplifiers in Noise Figure Measurements...

Страница 49: ...etting Up the Local Oscillator on page 56 Calibrating the Analyzer on page 58 Setting the Signal Analyzer to Make a Measurement on page 61 DUT Setup Form on page 61 Entering Excess Noise Ratio ENR Dat...

Страница 50: ...d LO frequencies Hence for a fixed output frequency and a fixed LO frequency there are two different input frequencies that are converted to the output frequency This is shown in Figure 3 1 The noise...

Страница 51: ...l compared to the signal levels involved in the noise figure measurement Hence LO leakage needs to be considered when measuring noise figure of a frequency converting DUT When working in low band 3 6...

Страница 52: ...ms to be considered are Decide the frequency ranges that must be covered Input LO and Output Calculate the frequency range that the unwanted image will cover Calculate the frequency range that the LO...

Страница 53: ...erforms frequency calculations and controls the frequency for a variety of mixer modes However you have to determine the filter requirements and provide those filters in the measurement setup Downconv...

Страница 54: ...lts in a loss of frequency resolution and accuracy Figure 3 3 Double Sideband Measurements Figure 3 3 shows a double sideband downconversion mixing Noise from two separated RF bands are mixed into the...

Страница 55: ...omparable to those that would have been given by an SSB measurement DSB measurements are not appropriate for making measurements where DUT performance or noise source ENR have significant variation ov...

Страница 56: ...lters for each 4 Consider the LO frequency and harmonics Is a filter needed to protect the analyzer input being desensitized by LO leakage in the 0 to 4 6 GHz range 5 Choose a filter if necessary to g...

Страница 57: ...ave sufficient power to drive mixers typically 7 dBm It should have excellent frequency accuracy and repeatability typically the same as the analyzer you are using The last point frequency accuracy de...

Страница 58: ...either perform a calibration over the desired measurement frequency range change the measurement frequency to one covered by the existing calibration perform uncalibrated measurements Uncorrected meas...

Страница 59: ...ts that is the frequencies at which measurements are made change whenever the start frequency the stop frequency or the number of sweep points is changed Calibration Indicator Whenever anything within...

Страница 60: ...mp The information contained there allows the instrument to calculate the Pcold and Phot values When to perform calibration For cases described in When to Perform Calibration on page 59 you need to ch...

Страница 61: ...m Item Description Name Available Selections 1 Setup Calibration Selects the calibration diagram to be displayed The diagram represents the connections you need to make to perform the calibration usin...

Страница 62: ...ers to the frequency or frequency range after the DUT If a system downconverter is not used the IF frequency will be the input frequency of the signal analyzer In the case of a system downconverter IF...

Страница 63: ...y be applied to one frequency which is the LO frequency The ENR values cannot be applied simultaneously to both the upper sideband and to the lower sideband The ENR values are therefore applied to the...

Страница 64: ...alyzer SNS connector on the rear panel and their ENR data is downloaded automatically into the analyzer The tasks related to entering ENR data in this section are listed below Selecting a Common ENR T...

Страница 65: ...ion and measurement Press MEAS SETUP ENR Use Meas Table Data for Cal to On When the Use Meas Table Data for Cal is turned on the ENR data for both the measurement and calibration is sourced from a com...

Страница 66: ...have the ENR values printed on a label that is affixed to the body of the device These ENR values are also provided in the form of a calibration report and on a diskette which is supplied with all Ke...

Страница 67: ...calibration ENR data make sure that Use Meas Table Data for Cal is set to Off and then select your table by pressing either Meas Table or Cal Table Figure 3 5 ENR Table 5 Optional Press Serial enter...

Страница 68: ...ve the ENR table using the Save key For details on saving files see Saving an ENR Table on page 68 ENR table data survives a power cycle and preset You need to save ENR data if you wish to recall it e...

Страница 69: ...K 23 25 C or 73 85 F The T cold key is set to Default to confirm this default temperature To change the User Tcold value manually press MEAS SETUP ENR TCold Mode to User User T Cold and then enter th...

Страница 70: ...ncy stop frequency center frequency span and sweep points parameters are unavailable in List mode Using Swept Frequency Mode In swept frequency mode you set the start and stop frequencies or equivalen...

Страница 71: ...e frequency list table press FREQ Freq Mode List You can create a frequency list in the following ways Manually by specifying each individual point From the sweep points by specifying the measurement...

Страница 72: ...v format It is sometimes more convenient to use a text editor to edit or enter this data rather than to enter the data manually using the analyzer Start by saving at least one value to memory and then...

Страница 73: ...chosen the more accurate the measurement as this reduces jitter on the measurement However this must be considered against how long it takes to complete the measurement There is therefore a trade off...

Страница 74: ...e press Sweep Control Avg Time Pt and set the average time for each point The Avg Hold Num value under the Meas Setup menu is to set the number of traces that will be averaged Press MEAS SETUP Averagi...

Страница 75: ...hat is compression occurring at the preamp stage set the attenuation AMPTD Attenuation tab to 0 dB and note the noise figure of your DUT Now increase the attenuation by one step 4 dB by pressing the u...

Страница 76: ...the input noise outside the preselector bandwidth nominally 40 to 80 MHz gets reflected without causing nonlinearities in the analyzer input stages a The figures given in this table assume a 5 dB ENR...

Страница 77: ...LO is connected through LAN Setting up DUT LO or System Downconverter LO The setting up process for a DUT LO and a system downconverter LO is similar Below is an example for setting up the DUT LO Step...

Страница 78: ...he absolute temperature of the device causing the loss You can compensate for this extra noise by specifying the temperature of the device causing the loss This temperature dependent compensation is a...

Страница 79: ...After DUT Loss Comp Mode Fixed 3 Press Fixed Loss and enter the loss compensation value and press the dB termination key The lower limit is 100 000 dB the upper limit is 100 000 dB and the default is...

Страница 80: ...s of the DUT s input frequencies and the After DUT Table are specified in terms of the DUT s output frequencies This is important when making frequency converting DUT measurements or using a system do...

Страница 81: ...e numeric keypad and press Enter The lower limit is 0 0 K the upper limit is 29 650 000 0 K The default is 290 0 K 5 Repeat steps 3 to 4 until all the Loss Frequency and Loss Values you need are enter...

Страница 82: ...or displaying point data more accurately than can be done with a trace alone Save the current active trace data to internal memory Switch the graticule on or off Switch the annotation on the measureme...

Страница 83: ...ange the active graph tap the desired window Selecting Result Types to Display You can choose to display any pair of measurement results in all of the display format modes The measurement result types...

Страница 84: ...d Setting the Scaling You can set the result s scale parameters in the active graph Press the AMPTD to display the Y Scale tab and press Auto Scaling to On Setting Auto Scaling to On selects the optim...

Страница 85: ...of the DUT for most cases The unit is Hz If you are going to calculate the noise power of the input mixer for frequency ranges higher than 3 6 GHz BW is the bandwidth of the preselector which is usual...

Страница 86: ...Equation 3 3 and are the noise figure and Gain of the DUT and are the noise figure and Gain of the USB Preamp You can get a rough values from the Keysight USB Preamplifers Technical Overview 5991 4246...

Страница 87: ...These are Application Note 57 1 Fundamentals of RF and Microwave Noise Figure Measurements http cp literature keysight com litweb pdf 5952 8255E pdf Application Note 57 2 Noise Figure Measurement Acc...

Страница 88: ...This information is subject to change without notice Keysight Technologies 2016 Edition 1 March 2016 N9069 90001 www keysight com...

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