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university:tools:pluto:users:transmit [01 Feb 2019 02:47] – [Transmit Power] Robin Getz | university:tools:pluto:users:transmit [08 Jun 2019 15:25] (current) – [Transmit Power] Robin Getz | ||
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===== Transmit Architecture ===== | ===== Transmit Architecture ===== | ||
- | The AD9363 transmit chain is based on [[wp> | + | The AD9363 transmit chain is based on [[wp> |
{{: | {{: | ||
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). | + | * 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: |
- | + | ||
===== Transmit Performance ===== | ===== Transmit Performance ===== | ||
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While there are many aspects of transmit performance, | While there are many aspects of transmit performance, | ||
- | * Output Power (how far can I 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, | + | For the ADALM-PLUTO, |
==== Transmit Power ==== | ==== Transmit Power ==== | ||
- | Most modern spectrum analyzers allow the measurement of the power within a frequency range, called the channel | + | Most modern spectrum analyzers allow measurement of power within a frequency range called the channel |
- | bandwidth. | + | bandwidth. |
<m 16>P_CH = {(B_S/ | <m 16>P_CH = {(B_S/ | ||
- | Where < | + | Where < |
For this test an LTE10 signal was transmitted at various LO frequencies, | For this test an LTE10 signal was transmitted at various LO frequencies, | ||
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{{ : | {{ : | ||
- | 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 a 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.</ | + | 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.</ |
+ | |||
+ | |||
+ | {{: | ||
- | {{: | + | {{ : |
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 | + | As expected, the wider LTE10 channel |
==== Transmit Fidelity | ==== Transmit Fidelity | ||
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<WRAP important> | <WRAP important> | ||
- | We need to re-do the tests in an RF chamber, to make sure there is no external noise. | + | This test was done in an open lab setting and as a result we can observe degradation at certain common commercial frequencies like LTE and WiFi. To remove these outliers |