diff options
| -rw-r--r-- | host/docs/usrp_e3x0.dox | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/host/docs/usrp_e3x0.dox b/host/docs/usrp_e3x0.dox index cd241b08d..d1f2448bd 100644 --- a/host/docs/usrp_e3x0.dox +++ b/host/docs/usrp_e3x0.dox @@ -436,7 +436,8 @@ For more advanced IMU based applications please refer to the <a href="https://gi Please see the \ref page_gpio_api for information on configuring and using the GPIO bus. -\subsection e3x0_hw_audio Audio connectors +\subsection e3x0_hw_audio Audio connectors (if populated) + The E3x0 2.5 mm Audio Jack TRRS pins are assigned as follows: Tip=Mic, Ring1=Right, Ring2=Left, Sleeve=GND. \image html TRRS.png "Audio Jack" @@ -544,6 +545,22 @@ Both transmit and receive can be used in a MIMO configuration. For the MIMO case, both receive frontends share the RX LO, and both transmit frontends share the TX LO. Each LO is tunable between 50 MHz and 6 GHz. +As there is a single LO for each direction (RX and TX), this means that both +channels need to use the same LO frequency (i.e., both RX channels share an LO +frequency, and both TX channels share an LO frequency). If the two channels +are supposed to receive on different frequencies, the digital tune stages need +to be used for that. The two frequencies will need to be within the currently +selected master clock rate, and the final bandwidths need to be chosen +carefully. Example: Assume the master clock rate is set to 50 MHz, and we want +to receive at 400 MHz and 440 MHz. We can set the LO to 420 MHz, which will +sample the spectrum from 395 MHz to 445 MHz. The LO offsets for both channels +need to be 20 MHz and -20 MHz respectively. However, the final bandwidth should +be less than 10 MHz (preferably lower), or the signals would exhibit aliasing. + +Because both channels share an LO, tuning one channel can possibly affect the +other channel. It is advisable to read back the actual, current frequency from +software before assuming the device is tuned to a specific frequency. + \subsubsection e3x0_dboard_e310_gain Frontend gain All frontends have individual analog gain controls. The receive |