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university:tools:pluto:users:transmit [25 May 2019 16:04]
Robin Getz add note about 61 vs 63
university:tools:pluto:users:transmit [08 Jun 2019 15:25]
Robin Getz [Transmit Power]
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 ===== Transmit Architecture ===== ===== Transmit Architecture =====
  
-The AD9363 transmit chain is based on [[wp>​Direct-conversion_receiver|Direct Conversion]] techniques. Although this block diagram is for the [[adi>​AD9361]],​ it is also appropirate for the [[adi>​AD9363]] found inside the ADALM-PLUTO. The difference ​between the two units is the tuning range, a minor missing features (DCXO, external LO are missing and the RF channel bandwidth is reduced).+The AD9363 transmit chain is based on [[wp>​Direct-conversion_receiver|Direct Conversion]] techniques. Although this block diagram is for the [[adi>​AD9361]],​ it is also appropirate for the [[adi>​AD9363]] found inside the ADALM-PLUTO. The differences ​between the two units are the tuning range and minor missing features (DCXO, external LO are missingand the RF channel bandwidth is reduced).
  
 {{:​resources:​eval:​user-guides:​ad-fmcomms2-ebz:​ad9361.svg?​950x650|}} {{:​resources:​eval:​user-guides:​ad-fmcomms2-ebz:​ad9361.svg?​950x650|}}
  
 Some things to think about: Some things to think about:
-  * The Tx LO is always the same amplitude, to get the best Signal to LO ratio, run the DACs as close to full scale as you can, and then turn up/down the output attenuation to vary the output signal strength. (Don't just decrease the input to the DAC). Full scale into the DAC is 12 bits and to supply a full scale signal using HDL provided by ADI will actually require a 16 bit signal to be provided, where the lower 4 LSBs are removed. See the [[resources:​fpga:​docs:​axi_ad9361|AXI_AD9361]] documentation for more details on these interfaces.+  * The Tx LO is always the same amplitude, therefore, to get the best Signal to LO ratio, run the DACs as close to full scale as you can, and then turn up/down the output attenuation to vary the output signal strength. (Don't just decrease the input to the DAC). Full scale into the DAC is 12 bits, but to supply a full scale signal using HDL provided by ADI will actually require a 16 bit signal to be provided, where the lower 4 LSBs are removed. See the [[resources:​fpga:​docs:​axi_ad9361|AXI_AD9361]] documentation for more details on these interfaces.
 ===== Transmit Performance ===== ===== Transmit Performance =====
  
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 While there are many aspects of transmit performance,​ the two most common are: While there are many aspects of transmit performance,​ the two most common are:
-  * Output Power (how far can transmit)+  * Output Power (how far can it transmit)
   * Output fidelity (how accurate is the transmission)   * Output fidelity (how accurate is the transmission)
  
-For the ADALM-PLUTO, ​the both the output power and output accuracy are both frequency dependent.+For the ADALM-PLUTO,​ both the output power and output accuracy are frequency dependent.
  
 ==== Transmit Power ==== ==== Transmit Power ====
  
-Most modern spectrum analyzers allow the measurement of the power within a frequency rangecalled the channel +Most modern spectrum analyzers allow measurement of power within a frequency range called the channel 
-bandwidth. Such analyzers make many small power measurements <​m>​p_i</​m>​ across a frequency range and average ​them as so to calculate a desired channel power over a desired frequency range using the following equation:+bandwidth. Such analyzers make many small power measurements <​m>​p_i</​m>​ across a frequency range. They average ​these power measurements ​to calculate a desired channel power over a desired frequency range using the following equation:
  
 <m 16>P_CH = {(B_S/​B_N)(1/​N)sum{i=n_1}{n_2} 10^(p_i/​10)}</​m>​ <m 16>P_CH = {(B_S/​B_N)(1/​N)sum{i=n_1}{n_2} 10^(p_i/​10)}</​m>​
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 {{  :​university:​tools:​pluto:​users:​pluto_tx_pow.svg?​600 ​ |LTE10 Power in channel}} {{  :​university:​tools:​pluto:​users:​pluto_tx_pow.svg?​600 ​ |LTE10 Power in channel}}
  
-This differs from the a continuous sine wave (CW) at various LOs, were the LO was swept from 70 MHz to 6 GHz. This is not measuring power in the channel, just peak transmit power (the spectrum analyzer was set up to do a peak hold). The two graphs show the difference between the Tx attenuation settings. The default setting of -10dB ensures that the analog output stages are running completely in the linear range, and will not saturate or come close to the 1PdB point. It is also safe at this setting to loop the Tx directly into the Rx with SMA cable. <wrap alert>Do not set the TX attenuation to anything less than -10dB and loop the Tx (output) signal into the Rx (input) connector.</​wrap>​ However, using the AD9361 or any SDR should be calibrated before attempting any measurement in absolute units. This is necessary since data that is provided from the AD9361 is in reference to the full scale range of the ADC which is dependent on the gain stages of the transceiver. The values ​produce ​are therefore best described in unit dBFS or ADC codes not dBm or volts.+This differs from the a continuous sine wave (CW) at various LOs, were the LO was swept from 70 MHz to 6 GHz. This is not measuring power in the channel, just peak transmit power (the spectrum analyzer was set up to do a peak hold). The two graphs show the difference between the Tx attenuation settings. The default setting of -10dB ensures that the analog output stages are running completely in the linear range, and will not saturate or come close to the 1PdB point. It is also safe at this setting to loop the Tx directly into the Rx with an SMA cable. <wrap alert>Do not set the TX attenuation to anything less than -10dB and loop the Tx (output) signal into the Rx (input) connector.</​wrap>​ However, using the AD9361 or any SDR should be calibrated before attempting any measurement in absolute units. This is necessary since data that is provided from the AD9361 is in reference to the full scale range of the ADC which is dependent on the gain stages of the transceiver. The values ​produced ​are therefore best described in dBFS or ADC codes, and not dBm or volts.
  
-{{:​university:​tools:​pluto:​users:​txat0.png?​415  ​|CW at 0dB attenuation}}{{ ​ :​university:​tools:​pluto:​users:​txat-10.png?​415|WC at -10dB attenuation}}+ 
 +{{:​university:​tools:​pluto:​users:​txat0.png?​420 |CW at 0dB attenuation}} 
 + 
 +{{ :​university:​tools:​pluto:​users:​txat-10.png?​420|WC at -10dB attenuation}}
  
 The random peaks in the -10 dB attenuation settings are (I think) random noise caused by the Tx calibrations when the LO changes by more than 100 MHz. The random peaks in the -10 dB attenuation settings are (I think) random noise caused by the Tx calibrations when the LO changes by more than 100 MHz.
  
-As expected the wider LTE10 channel ​measurements have more //power// in it than a narrow CW signal. ​+As expectedthe wider LTE10 channel ​measurement has more //power// in it than a narrow CW signal. ​
  
 ==== Transmit Fidelity ​ ==== ==== Transmit Fidelity ​ ====
university/tools/pluto/users/transmit.txt · Last modified: 08 Jun 2019 15:25 by Robin Getz