Test & Calibration Benefits from a New Precision RF/Microwave Calibrator

Transcription

1 Test & Calibration Benefits from a New Precision RF/Microwave Calibrator Topics: RF & Microwave calibration signal requirements Design philosophy and architecture of the new RF Calibrator. Spectrum analyzer calibration example Spectrum analyzer calibration and signal requirements overview Benefits of using new calibrator features Conclusions 2014 Fluke Calibration 1

2 Decreasing Level RF Cal Signal Requirements RF & Microwave Calibration Signal Frequency & Level Requirements Increasing Frequency Frequency Response testing of spectrum analyzers, power sensors, HF Oscilloscope bandwidth testing, etc HF Oscilloscope BW testing also includes lower levels Typical region for frequency response testing over wide frequency and shallow level range. Slightly lower level region for frequency response tests. Typical region for linearity testing over narrow frequency and deep level range. Linearity (scale fidelity) and attenuator accuracy calibration of spectrum analyzers, power sensor linearity testing, etc In general, the signals required can be split into two areas: A relatively narrow range of lower frequencies over a wide (deep) level range At relatively high levels from low to very high frequencies Fluke Corporation A key factor for the RF Calibrator design strategy. 3

3 Purpose designed calibration solution Specifically designed to meet requirements for calibrating RF/Microwave equipment (Spectrum analyzers, power sensors, high frequency oscilloscopes, receivers, etc..) Fluke 96270A 27GHz Low Phase Noise RF Reference Source Configured with two power sensors for dual power meter readout Features & capabilities: Calibration oriented user interface and functionality Precision signal level and attenuation, high signal purity and low distortion modulation Low phase noise and jitter Integral dual power meter readout and 300MHz frequency counter What you set is what you get accurate signal delivery direct to the UUT input up to 27 GHz Self-characterisation at microwave front panel or sensor/splitter (HF Levelling kit) outputs Multiple profiles can be saved and loaded via USB or GPIB GPIB emulation modes for many common legacy and modern generators, 2011 Fluke plus the Corporation 9640A Series 4 Frequency Counter screen and rear panel frequency counter input BNC

4 Purpose designed calibration solution Specifically designed to meet requirements for calibrating RF/Microwave equipment (Spectrum analyzers, power sensors, high frequency oscilloscopes, receivers, etc..) Precision level and attenuation output from 1mHz to 4GHz. Provides wide dynamic range high and low level signals from +24dBm down to -130dBm. Fluke 96270A 27GHz Low Phase Noise RF Reference Source Unique low output VSWR leveling head with built-in precision attenuators delivers signals directly to the UUT input, avoiding cable losses, minimizing mismatch errors and uncertainties. What you set is what you get accurate delivery of signal level set on front panel directly at the reference plane established at the UUT input. Features & capabilities: Calibration oriented user interface and functionality Precision signal level and attenuation, high signal purity and low distortion modulation Low phase noise and jitter Integral dual power meter readout and 300MHz frequency counter What you set is what you get accurate signal delivery direct to the UUT input up to 27 GHz Self-characterisation at microwave front panel or sensor/splitter (HF Levelling kit) outputs Multiple profiles can be saved and loaded via USB or GPIB GPIB emulation modes for many common legacy and modern generators, 2011 Fluke plus the Corporation 9640A Series 5

5 Purpose designed calibration solution Specifically designed to meet requirements for calibrating spectrum analyzers and other RF/Microwave equipment (Power sensor, high frequency oscilloscopes, receivers, etc..) Fluke 96270A 27GHz Low Phase Noise RF Reference Source Configured with two power sensors for dual power meter readout Precision leveled high frequency (1kHz to 27GHz) output using HF leveling kit power splitter & power sensor. Provides high level signals from +24dBm to -10dBm. Features & capabilities: Calibration oriented user interface and functionality (Levels down to -35dBm with Low Level Microwave O/P Precision signal level and attenuation, high signal purity and low option and supplied NRP-Z55.03 sensor. Lower levels with compatible low-level power sensors). distortion modulation Low phase noise and jitter Self-Characterization at the HF Fully automatic what you set is what you get level Integral dual power meter readout and 300MHz frequency counter Levelling Kit splitter output control feedback from the splitter/sensor ensures signal What you set is what you get accurate signal delivery direct to amplitude setting on the front panel accurately delivered the UUT input up to 27 GHz at the reference plane established at the UUT input. Self-characterisation at microwave front panel or sensor/splitter (HF Levelling kit) outputs For greater precision, self-characterization at the Multiple profiles can be saved and loaded via USB or GPIB sensor/splitter output easily compensates for the GPIB emulation modes for many common legacy and modern ( 0.25dB) splitter output port tracking error. generators, 2011 Fluke plus the Corporation 9640A Series 6 Reference Plane established here

6 Instrument Architecture Levelling Head O/P Output: 1mHz to 4GHz, -130dBm to +24dBm Output signals delivered direct to the load or Unit Under Test (UUT) input minimize performance degradation due to cabling and interconnections. Signals generated in the mainframe are fed to the leveling head containing the level detector and attenuator circuits. Control PCA, includes head cal store memory Fluke 96270A RF Reference Source 1mHz - 20kHz: Wavetable & DAC 20kHz - 9MHz: Hi-Res DDS 9MHz - 4GHz: PLL, Frequency Translation & Division Multiple output amplifiers cover frequency range Filters provide very low harmonic content RF PCA and screen containing level sensing and attenuators 10MHz OCXO 60dB of attenuation in 10dB steps Frequency Synthesis & Division Floating PSU Level Control Amplifiers Filters O/P Atten Mainframe (Base Unit) Level Sensing Attenuators Levelling Head Additional attenuation for lower level outputs Frequency Modulation generated in FM DDS Level Control circuits also generate Amplitude Modulation

7 Instrument Architecture Microwave O/P Front panel O/P: 1mHz to 27GHz, -100dBm to +24dBm Sensor/splitter O/P 1kHz to 27GHz, -35dBm to +24dBm Signal output at the front panel Microwave Output connector, or direct to the Unit Under Test (UUT) via the HF Leveling Kit Sensor/Splitter output. With sensor/splitter leveling, automatic digital feedback ensures signal level set on the front panel is accurately delivered at the reference plane established at the UUT input. Reference plane here Fluke 96270A RF Reference Source 1mHz - 20kHz: Wavetable & DAC 20kHz - 9MHz: Hi-Res DDS 9MHz - 4GHz: PLL, Frequency Translation & Division 4GHz - 27GHz: PLL, Frequency Multiplication Multiple output amplifiers cover frequency range Filters provide very low harmonic content 10MHz OCXO Optional Low Level Microwave Output step attenuator (100dB) Frequency Synthesis, Division & Multiplication Level Control Amplifiers Filters Step Atten Level Sensing Power Splitter O/P to UUT Floating PSU Digital Control Mainframe (Base Unit) Power Sensor Frequency Modulation generated in FM DDS Internal Level Control circuits also generate Amplitude Modulation Digital level feedback

8 Self-Characterization overview A truly unique capability, self-characterization is not available from any other signal source: Specially designed for calibration, this feature automatically measures the losses in the signal delivery path up to the RF reference plane and uses this information to allow the user to set a required power level directly on the 96270A and deliver that exact power to the RF reference plane! All controlled from and by the RF Calibrator What you set is what you get the front panel output level setting is automatically established at the reference plane Eliminates tedious calculations of correction factors Simplifies equipment requirements, interconnections and operation Eliminates operator errors Using the characterized HF Levelling kit output for spectrum analyzer cal (above) and power sensor cal (below). Levelling Sensor Reference Sensor Self-Characterization of the HF Levelling kit (Splitter/Sensor) output. Compensates for splitter output port tracking error.

9 Example application: Spectrum Analyzer cal How the calibrator design concepts are applied to spectrum analyzer calibration. Reducing complexity by >80%... Illustrated by considering the calibration requirements and test points for a popular 26.5GHz spectrum analyzer model The E4407B E4407B 26.5 GHz 2014 Fluke Corporation. 11

10 Why calibrate? A spectrum analyzer is.a measuring instrument for representation and assessment of the frequency spectrum of a signal in terms of frequency and level.allowing users to determine whether signals are free from harmonics, or to separate and weight the components of a modulated signal at different frequencies, etc Spectrum analyzers are sophisticated measuring instruments High performance, tight specifications A multitude of measurement features Applications require numeric data No longer indication only So, calibrate the underlying analyzer performance, on which these measurement features/personalities depend Need confidence that measurements are true indication of signal characteristics, not artefacts or impairments introduced by the analyzer itself 3GPP WCDMA adjacent channel leakage ratio measurement Spurious close to carrier measurement WCDMA code domain power measurement

11 Calibrated parameters Our analysis of spectrum analyzer cal procedures for 15 models from 5 manufacturers found 80 different tests described tests performed on majority of models in study In general, common tests are: Frequency Accuracy Level Accuracy Frequency Response Attenuator Response Display Linearity Displayed Average Noise Level Resolution Bandwidth Accuracy Resolution Bandwidth Selectivity Resolution Bandwidth Switching Accuracy Sweep Time Accuracy IF Image Response Noise Sidebands Residual FM Residual & Spurious Responses Harmonic Distortion 3rd order Intercept (TOI) Tracking generator tests Also including other spectrum analyzer calibration standards documents: German VDE VDI/VDE/DGQ/DKD 2622 Part 11 Chinese JJG (Manufacturers often use specific test names and groupings, but most are similarly titled) 2014 Fluke Corporation 14

12 Typical signal frequency/level requirements Analysis of published calibration procedure for a 26GHz analyzer: Example: The manufacturer s published calibration guide published for the ESA series spectrum analyzer product range is 640 pages long! E4407B 26 GHz This tables summarizes tests, test point frequencies and amplitudes for the E4407B model, totalling over 400 individual test points. Majority of testing is at lower frequencies: 80% of testpoints <3GHz For this example, and generally for other models/manufacturers. Calibration Test Test Signal Frequency/Range Tested at LF Only Tests include HF Test Signal Amplitude/Range Frequency Span Accuracy 300MHz to 1.5GHz 0dBm Frequency Readout Accuracy 1.5GHz to 21GHz -10dBm Level Accuracy 50MHz -80dBm to 0dBm Frequency Response 9kHz to 26.5GHz -10dBm Attenuator Switching Accuracy 50MHz -65dBm to 0dBm Display Linearity 50MHz -98dBm to 0dBm Displayed Average Noise level 10MHz to 26.5GHz No input required Resolution Bandwidth Accuracy 50MHz -8dBm to -5dBm Resolution Bandwidth Selectivity 50MHz -68dBm to -5dBm Resolution Bandwidth Switching Accuracy 50MHz -20dBm Sweep Time Accuracy 500MHz -10dBm Spurious Responses 2GHz to 21.6GHz -10dBm Noise Sidebands 1GHz 0dBm Residual FM 1GHz -10dBm Harmonic Distortion 300MHz to 3.1GHz -10dBm 3 rd Order Intercept (TOI) & Gain Compression* 2 signals f 1MHz, 50MHz to 14GHz -40dBm, -10 dbm & -5dBm to 0dBm * = TOI (3rd Order Intercept) and Gain Compression tests typically require two simultaneous signals 1MHz apart. These tests often not specified, not performed, or considered optional.

13 Decreasing Level Signal Requirements Spectrum Analyzer Calibration Signal Frequency & Level Requirements Increasing Frequency Frequency Response Image/Spurious Responses TOI* Gain Compression* * = Two simultaneous signals required for TOI (3 rd Order Intercept) and Gain Compression tests, typically 1MHz apart. Wide frequency and shallow level range. Slightly lower level region for a few specific tests. Narrow frequency and deep level range. Frequency Accuracy Level Accuracy RBW Accuracy Frequency Response (LF) Filter Shape RBW Switching Display Linearity Attenuator Accuracy Harmonics Image/Spurious Responses (LF) Noise Sidebands Phase Noise Sweep Time Accuracy In general, the signals required in spectrum analyzer calibration can be split into two areas: at a relatively narrow range of lower frequencies over a wide (deep) level range at relatively high levels from low to very high frequencies Fluke Corporation 18

14 Test setup complexity For example, a typical 26GHz analyzer procedure: Manufacturer s published calibration procedure for the E4407B model: Typically items of test equipment do not address full performance or dynamic range Signal Sources Procedure requires up to 6 individual signal sources Accuracy, noise & dynamic range Modulation waveform needs Power Sensors Step & fixed attenuators, filters, directional couplers/bridges Many popular items are now obsolete or difficult to maintain Older, simpler instruments preferred by metrologists for their performance suited to calibration applications Individual tests often require device/setup characterizations prior to UUT measurement Procedure has 27 different equipment setups Even if automated, user intervention to make setup changes is time consuming and inefficient 2014 Fluke Corporation. 20

15 Decreasing Level Applying the RF Calibrator Meeting spectrum analyzer calibration signal requirements with a purpose designed calibrator Increasing Frequency Frequency Response Image/Spurious Responses TOI* Gain Compression* Wide frequency and shallow level range Slightly lower level wide frequency range region Narrow frequency and deep level range Requirements for the two signal ranges met by the Levelling Head and Sensor splitter outputs: Levelling Head for tests requiring a relatively narrow range of lower frequencies over a deep level range Sensor/Splitter output for tests requiring relatively high levels from low to very high frequencies. Frequency Accuracy Level Accuracy RBW Accuracy Frequency Response (LF) Filter Shape RBW Switching Display Linearity Attenuator Accuracy Harmonics Image/Spurious Responses (LF) Noise Sidebands Phase Noise Sweep Time Accuracy * Adding a traditional signal generator conveniently addresses requirements for two simultaneous signals if TOI and Gain Compression tests are to be performed Fluke Corporation 21

16 Reduced complexity, optimized sequence Key requirements met by a single instrument. Majority of test points (>80%) and test time through a single connection Other quicker tests requiring connection changes performed at start or end of procedure, maximising walkaway time if automated. Displayed Noise Level Residual Responses Alternative to simple 50Ω termination with no input: 96270A set to O/P off Frequency Accuracy Level Accuracy RBW Accuracy Frequency Response Filter Shape RBW Switching Display Linearity Attenuator Accuracy Harmonics Image/Spurious Responses Noise Sidebands Phase Noise Sweep Time Accuracy 3 rd Order Intercept Gain Compression Many labs choose to omit these brief tests Use additional generator if testing required 96270A output choice based on test frequency HF Frequency Response HF Frequency/Span Accy 96270A Sensor/Splitter output for tests > 4GHz 96270A Leveling Head 2014 Fluke Corporation output for tests 4GHz 22

17 Purpose designed equipment impact Typical 26GHz analyzer calibration procedure requires 27 equipment setups Employs 6 individual signal sources Many other items and accessories Cost effective alternative: deployment of a purpose designed RF calibrator 27 setups reduced to 4 for a typical 26GHz analyzer 85% complexity reduction Majority of testing addressed by a single source Automated system operator intervention significantly reduced, 90mins walkaway time in a 2 hour run Automated system capacity increased up to 25% Operator efficiency greatly improved, by up to 60% 2014 Fluke Corporation 23 Fluke 96270A 27GHz Low Phase Noise RF Reference Source

18 Conclusions Key design & architecture concepts Frequency synthesis/generation and signal delivery with high frequency accuracy & resolution, low harmonics & spurious, and ultra-low phase noise & jitter from 1mHz to 27GHz Application oriented/optimised outputs: Levelling Head output addresses precision signal absolute and relative (attenuation) amplitude requirements Wide (>150dB) dynamic range at required lower frequency (1mHz to 4GHz) range Low VSWR output, short transmission line lengths Direct connection to UUT avoids mismatch and loss errors Microwave output addresses high frequency signal requirements Direct output (-4dBm to +24dBm, 1mHz to 27GHz) Architecture includes optional setup attenuator for extended low level microwave output levels (to -100dB) Sensor/Splitter mode addresses precision amplitude requirements (-35dBm to +24dBm, 1kHz to 27GHz) Fully automatic What you set is what you get digital levelling control at the UUT input reference plane Unique Profile and Self Characterisation capability, automatically measures and compensate for device and interconnection loss/gain Simplifies measurement procedures and avoids need for users to calculate and apply corrections for signal path and device attenuation and losses Fully floating RF common avoids ground loop problems and common mode errors, particularly at low levels Calibration-oriented user interface design Key design requirement achieved: To simplify RF Calibration processes and procedures The implementation described results in significant impact on UUT calibration process complexity For example, as illustrated with >80% complexity reduction for spectrum analyzer calibration 2014 Fluke Corporation 24