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RF Calibration

RF Calibration. For MSM6025 Platform By Wu Chunming. RF calibration, what is it and why do I care?. Subscriber units have differing RF characteristics. – Some characteristics vary from one unit to the next – Other characteristics vary from one design to the next.

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RF Calibration

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  1. RF Calibration For MSM6025 Platform By Wu Chunming

  2. RF calibration, what is it and why do I care? • Subscriber units have differing RF characteristics. • –Some characteristics vary from one unit to the next • –Other characteristics vary from one design to the next

  3. RF calibration, what is it and why do I care?--RX • The subscriber unit must estimate the Rx power properly to maximize signal to noise ratios and to provide a basis for Tx power output.

  4. RF calibration, what is it and why do I care?--TX • The subscriber unit must transmit at correct Tx power level over its large dynamic range..

  5. RF calibration, what is it and why do I care? • The MSM device and system software combination must “know” the RF characteristics of the particular unit. This information is known as RF calibration data. • Failure to compensate for differing RF characteristics may cause the unit to fail minimum performance specifications.

  6. Factory Floor RF Calibration Setup

  7. radioOne RF Evaluation Software • •Included with the SURF6xxx platforms is the radioOne RF Evaluation Software (also called the FTM GUI). This GUI can be used with the SURF6xxx as well as custom designed handsets. • The radioOne RF Evaluation Software runs on the PC, and interfaces to the device under test (DUT) using the diagnostic port. • The radioOne RF Evaluation Software uses the Factory Test Mode (FTM) commands useful for calibration (see Factory Test Mode RF CommandsCL93-V4168-1 for more information on FTM RF Commands).

  8. Signal Generator Configuration • The signal generator produces an Rx signal for the unit. Always program the Signal generator to produce a simple carrier with a frequency which is 300* kHz offset from the desired Rx center frequency. This keeps the signal from becoming DC after downconversion.

  9. Spectrum Analyzer Configuration • •On the spectrum analyzer settings, –Turn averaging off (if the spectrum analyzer supports averaging)–Set span to 0–Ensure units of measurement are “dBm”–Set the sweep time to 20 ms–Set video bandwidth (VBW) to 10 Hz–Set resolution bandwidth to 1 MHz. –Attenuation settings may need to be dynamically adjusted depending on power level. • Note that the above settings only apply for measuring power of a CDMA waveform. Different settings should be used for measuring an AMPS signal.

  10. Calibrate the station itself: Rx path • The power level produced at the signal generator’s connector maydiffer from the subscriber unit’s RSSI (even in a calibrated subscriber unit) for two reasons:–Cable loss (including the directional coupler’s loss)–RSSI estimation error due to a using a narrowband sine wave rather than a 1.2288 MHz signal. • This error is constant in dB, at all relevant power levels. • It is necessary to measure this error and compensate for it whenproducing all Rx power levels using the signal generator.

  11. Calibrate the station itself: Rx path (2) • Connect the handset directly to a calibrated CDMA tester, such as the HP8924C, CMD80, or equivalent; or to a calibrated CDMA RF waveform generator. • Program the forward link power to be a nominal value. For this example, the forward link power is -63 dBm. We will call this value PowerNom. • Using the GUI application, force the LNA Range state to be in the correct range that corresponds to a power level of PowerNom. • Record the value from Get Rx AGC displayed on the GUI application. We will call this value RxAGCNom.

  12. Calibrate the station itself: Rx path (3) • •Without modifying any settings whatsoever with the GUI application, connect the device under test back to the standard setup, complete with signal generator, directional coupler, cables, etc. • Configure the signal generator to produce a simple unmodulated carrier tone having a frequency of the Rx reference frequency, plus 300 kHz. • Adjust the power level of the signal generator until RX AGC is equal to RxPdmNom. Record the power level displayed on the signal generator. We will call this PowerSigGen. • In this example, the power level of the signal generator, PowerSigGen, is -42.8 dBm.

  13. Calibrate the station itself: Rx path (4) • Calculate RxCalPowerOffset such that –RxCalPowerOffset = PowerSigGen -PowerNom. • In this example, we have–RxCalPowerOffset = 42.8 dBm -63 dBm = 20.2 dB • RxCalPowerOffset represents the additional power we will program the signal generator to produce, in order to create a specific desired power at the mobile station’s antenna. This is done for all signals produced by the signal generator. • Calibration accuracy can be further enhanced by making RxCalPowerOffset a function of the frequency index (there are 16 frequency indexes).

  14. Calibrate the station itself, Tx path • The power read by the spectrum analyzer differs from the actual Tx power at the antenna connector for two reasons:–Cable loss–Measurement error due to a using a 1 MHz resolution bandwidth to measure a 1.2288 MHz signal • This error is constant in dB, at all relevant power levels. • It is necessary to compensate for this error when taking all Tx power level measurements.

  15. Calibrate the station itself, Tx path(2) • Connect the device under test to a calibrated power meter using a short (lossless) cable. • Ensure the Tx Waveform CDMA radio button is selected on the GUI application. • Select the ON position for Tx On/Off radio buttons on the GUI. • Adjust the TX AGC until the power level read by the power meter is a nominal value, say around 0 dBm. • Record the power level displayed on power meter. As an example, assume the power was recorded to be -0.09 dBm.

  16. Calibrate the station itself, Tx path(3) • Without changing any of the settings in the GUI application, reconnect the device under test back to the standard lab setup. • Record the power displayed on the spectrum analyzer. In this example, the power displayed on the spectrum analyzer was -3.17 dBm. • TxCalPowerOffset = (power displayed by calibrated power meter) –(power displayed by spectrum analyzer) • In this example,TxCalPowerOffset = -0.09 -(-3.17) = 3.08 dB

  17. Calibrate the station itself, Tx path(4) • Use this TxCalPowerOffset to compensate every Tx power reading made when using the spectrum analyzer. • Calibration accuracy can be further enhanced by making TxCalPowerOffset a function of the frequency index (there are 16 frequency indexes).

  18. Automated Factory Floor Calibration Program • An automated factory floor calibration program must be created for high volume production. QCT provides the following documents useful for the creation of this program:–CDMA Dual-Mode Subscriber Station Serial Data Interface Control Document80-V1294-1–Factory Test Mode RF CommandsCL93-V4168-1–Select radioOne RF NV Items80-V3722-1

  19. Automated Factory Floor Calibration Program(2) • CDMA Dual-Mode Subscriber Station Serial Data Interface Control Document80-V1294-1 describes the low-level language used by the diagnostic task for communication between the PC and the DUT. • Use this as a reference for creating the interface protocol of the the PC side program. • The corresponding components in the DUT side are already a part of DMSS6xxx.

  20. Automated Factory Floor Calibration Program(3) • Factory Test Mode RF CommandsCL93-V4168-1 describes the specific RF subcommands useful for RF calibration. • Use this as a reference for creating the command protocol of the the PC side program. • The corresponding FTM components in the DUT side are already a part of DMSS6xxx.

  21. Automated Factory Floor Calibration Program(4) • Select radioOne RF NV Items80-V3722-1 provides understanding of each calibration item, including suggested calibration routines. • Use this as a reference for creating the high-level calibration algorithms of the the PC side program.

  22. Rx AGC loop enhancements in MSM60x0 devices • Blue indicates significant functional change compared to previous generation MSM devices implementing superheterodyne AGC control

  23. Rx AGC loop enhancements in MSM60x0 devices(2) • No Rx linearizer • RxAGC amplifier replaced by perfectly linear Digital Variable Gain Amplifier (DVGA).

  24. Rx AGC loop enhancements in MSM60x0 devices(3) • 4 LNA Range gain states (MSM6050/MSM6000 hardware support 5 gain states, but the total chipset solution supports 4). • It is essential that DynamicRange equal 85.3 dB (CDMA) and DynamicRangeFM equal 102.4 dB (AMPS). • It is essential that MinRSSIofInterest equal -106 dBm (CDMA) and MinRSSIofInterestFM equal -117 dB (AMPS). • It is essential that QCT’s recommended LNA Rise and Fall thresholds are used (see Select radioOne RF NV Items80-V3722-1 for specific recommended values).

  25. IM2 Calibration • –Using a signal generator, place an AM modulated carrier with thefollowing characteristics at the input to the antenna: • »The frequency of the carrier must be offset from the Rx reference frequency by 5.0 MHz. »Program the modulation tone be sinusoidal and to have a frequency of 20 kHz. • »Program the signal generator such that the AM modulation depth is 56 %. • »Program the signal strength to be –25 dBm at the antenna’s input. • »Check the RSSI using the FTM function Get RX AGC. If the RSSI is saturated (at the extreme limit), adjust the signal’s strength accordingly until the RSSI is no longer saturated. • –Call the FTM function Get CDMA IM2. It may take approximately 5 seconds before the function returns a value. • –Store the two values in NV_CDMA_IM2_I_VALUE and NV_CDMA_IM2_Q_VALUE.

  26. IM2 Calibration(2) • IM2 calibration, verification check • –Using a CDMA tester, place a CDMA signal at the antenna input with a signal strength of -104 dBm (at a frequency near the middle of the band) , and bring up a call. • –Using a signal generator, place an AM modulated carrier with thefollowing characteristics at the input to the antenna: • »The frequency of the carrier must be offset from the Rx reference frequency by 5.0 MHz. • »Program the modulation tone be sinusoidal and to have a frequency of 20 kHz.»Program the signal generator such that the AM modulation depth is 56%. • –If the mobile station can maintain FER of less than 1%, with theJammer’s power level at -20 dBm or greater, IM2 has been properly calibrated.

  27. IM2 Calibration(3) IM2 calibration, signal generator phase noise check –If the mobile station fails the IM2 calibration, verification check, it could be because the phase noise of the signal generator is too high. –Using a signal generator, place unmodulated carrier with the following characteristics at the input to the antenna: »The frequency of the carrier must be offset from the Rx reference frequency by 5.0 MHz. »Program the signal strength to be –25 dBm at the antenna’s input. –If the mobile station can maintain FER of less than 1 %, with the Jammer’s power level at -20 dBm or greater, this signal generator’s phase noise properties are acceptable. –If the mobile station’s FER varies significantly with the Jammer’s power level at -20 dBm or less, this signal generator’s phase noise properties are unacceptable for this test.

  28. Questions???

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