AD9361 Filter Wizard 1Rx and 1Tx setup

Hello! I am working on a testbed using a 2x8 antenna array base station and as UE I use the AD9361.

Both Bs and UE are using the same LTE_20 FIR configuration for the sample rate of 30.72 MHz.

My problem is that when I use the UE (2x2 transceiver called AD9361) as a single antenna (using one RF chain), the signal at the base station arrives half of the size that I am actually sending. 

My question is, how do I have to re-design these filters in order to operate only one RF chain?

Thank you very much!

Kind regards,

George

Parents
  • Hello and thank you for your reply,

    So, the AD9361 is set up through a .exe file generated with Visual Studio and I am using the LTE20 filter wizard.

    I am operating in TDD mode so I did the following settings :

    1, /* adi,1rx-1tx-mode-use-rx-num */
    1, /* adi,1rx-1tx-mode-use-tx-num */       (so I have one RF channel for both Tx and Rx)

    The initialization goes alright but I get an error which from what I read comes from the calibration of the digital comm between FPGA and the Radio640 (which is the ad9361 with some other stuff) but I don`t know exactly from which sampling rate or from what parameters this error appears:

    Radio640 Configuration: Calibration step

    Calibration on FMC 1 ...
    Error with InitRadio640
    Error code 0xC0850022: AD9361 module - No solution could be found for the digital calibration
    The program will terminate. Push any key to continue

    So at this step, I am still using the LTE20 filter at both sides ( 30.72 MHz sampling rate):

    TX 3 GAIN -6 INT 2
    RX 3 GAIN -6 DEC 2
    RTX 983040000 245760000 245760000 122880000 61440000 30720000
    RRX 983040000 491520000 245760000 122880000 61440000 30720000
    BWTX 19365438
    BWRX 19365514           (**I have also tried LTE10 for the 1TX1Rx board so it has half the sampling rate than the board that is set up as 2TX2Rx but I get the same error)

    with 

    two_rx_two_tx_mode_enable=0
    one_rx_one_tx_mode_use_rx_num=1
    one_rx_one_tx_mode_use_tx_num=1     ( setup as default parameters and also values taken from initialisation file to make sure this are input correctly every time)   

    What is your suggestion, how should debug this and fix the sampling rates (if this is the problem..), or the problem comes from somewhere else? Please let me know, I`ve been stuck on this for a while now. Thank you very much!

    Thank you!

Reply
  • Hello and thank you for your reply,

    So, the AD9361 is set up through a .exe file generated with Visual Studio and I am using the LTE20 filter wizard.

    I am operating in TDD mode so I did the following settings :

    1, /* adi,1rx-1tx-mode-use-rx-num */
    1, /* adi,1rx-1tx-mode-use-tx-num */       (so I have one RF channel for both Tx and Rx)

    The initialization goes alright but I get an error which from what I read comes from the calibration of the digital comm between FPGA and the Radio640 (which is the ad9361 with some other stuff) but I don`t know exactly from which sampling rate or from what parameters this error appears:

    Radio640 Configuration: Calibration step

    Calibration on FMC 1 ...
    Error with InitRadio640
    Error code 0xC0850022: AD9361 module - No solution could be found for the digital calibration
    The program will terminate. Push any key to continue

    So at this step, I am still using the LTE20 filter at both sides ( 30.72 MHz sampling rate):

    TX 3 GAIN -6 INT 2
    RX 3 GAIN -6 DEC 2
    RTX 983040000 245760000 245760000 122880000 61440000 30720000
    RRX 983040000 491520000 245760000 122880000 61440000 30720000
    BWTX 19365438
    BWRX 19365514           (**I have also tried LTE10 for the 1TX1Rx board so it has half the sampling rate than the board that is set up as 2TX2Rx but I get the same error)

    with 

    two_rx_two_tx_mode_enable=0
    one_rx_one_tx_mode_use_rx_num=1
    one_rx_one_tx_mode_use_tx_num=1     ( setup as default parameters and also values taken from initialisation file to make sure this are input correctly every time)   

    What is your suggestion, how should debug this and fix the sampling rates (if this is the problem..), or the problem comes from somewhere else? Please let me know, I`ve been stuck on this for a while now. Thank you very much!

    Thank you!

Children
  • it only works with the following:

    1, //adi,2rx-2tx-mode-enable
    0, /* adi,1rx-1tx-mode-use-rx-num */
    0, /* adi,1rx-1tx-mode-use-tx-num */

    But I cannot use this when trying to transmit only one signal from one antenna because the signal at the Rx is halved. 

  • 0
    •  Analog Employees 
    on May 18, 2021 10:49 AM in reply to George9955

    Have you cleared the below parameter along with the other two for enabling 1T1R mode?

    adi,2t2r-timing-enable two_t_two_r_timing_enable When set, the data port uses 2R2T timing, regardless of the number of enabled transmitters and receivers. When clear, the timing reflects the number of enabled signal paths. 

    But I cannot use this when trying to transmit only one signal from one antenna because the signal at the Rx is halved. 

    What do you mean by the signal at the RX is halved?

  • Thank you for your reply! It completely makes sense but it doesn`t work for me.

    So, what I meant by "halved" is that when sending only one signal from the UE (~13000 samples), at the BS I receive half of the waveform I sent (6500 samples). When I send two signals from the UE (13000 samples each) I receive the whole waveform at the BS (13000 samples)

    I tried the following setting:

    • two_rx_two_tx_mode_enable=1
    • two_t_two_r_timing_enable=0
    • one_rx_one_tx_mode_use_rx_num=0                                                  
    • one_rx_one_tx_mode_use_tx_num=0  

    With this setting, the same thing happens I get half of the waveform I send. The filter I am using is the LTE_20 at both BS and UE with the following characteristics:

    # Data Sample Frequency = 30720000.000000 Hz
    TX 3 GAIN -6 INT 2
    RX 3 GAIN -6 DEC 2
    RTX 983040000 245760000 245760000 122880000 61440000 30720000
    RRX 983040000 491520000 245760000 122880000 61440000 30720000
    BWTX 19365438
    BWRX 19365514

    Using LTE_20 at both BS and UE results in receiving half o the samples I sent. However, when I check the amplitude of the subcarriers I received ( using plot(abs(received_signals))) the amplitudes are even over the 1200 subcarriers I sent.

    Using LTE_10 at the UE (from which I try to send only one signal) and LTE_20 at the BS (thinking that because I receive half of the samples I could double the sampling rate speed at the BS) results in receiving the whole waveform (13000 samples). For this setting, I can also get a constellation but with a high EVM. The high EVM comes from the fact that even I receive all the samples, when I check the amplitude of the received subcarriers I can always see like a pulse waveform where the middle is like a square shape ( having an even amplitude) but at the sides like subcarrier 0:200 and subcarrier 800:1200 are filtered out ...are attenuated close to 0 and I don`t understand why. 

    So, using the same LTE_20 filter on both sides of the wireless link results in receiving half of the samples, but with all the subcarriers with even amplitude. When I use a filter at the UE that has half of the rate of the one at the BS (ex: LTE10 with LTE20) I receive all the samples, but with some of the subcarriers filtered out. 

    Please let me know how I should proceed from here because I`ve been stuck with this problem for a long time! Thank you!

    Also, let me know if you want me to provide you with the plots via email!

    Kind regards,

    George