Simple sinewave strangeness

ewaldo · 10 July 2017 01:24

I have noticed that I get some strange tones when I do a simple sinewave generator flowgraph using the TX/RX chain with a cable connected directly between TX1_1 and RX1_H on my LimeSDR. At the receiver end I get almost a double tone with some strange garble. I have done the same flowgraph with a USRP1 with the Basic RX/TX and get a much cleaner tone. I get similar results when I use 220Mhz on the LimeSDR, but I have used 2.245Ghz in the graph because the sound artifacts are more pronounced.

I would like to know what is causing this as I believe it is related to some other problems I have been attempting to troubleshoot.

LimeSDR Graph

LimeSDR Tone

USRP Graph

USRP Tone

Kc7noa · 10 July 2017 01:57

Is it produced in the tx chain or rx?

ewaldo · 10 July 2017 04:27

The tones I linked were when I added a wave file sink in parallel to the Audio Sink.

Cornie · 10 July 2017 07:37

@ewaldo
You make an extreme violation of the sample theorem here. Since the LimeSDR has no brickwall filters I would increase the LimeSDR sample rate to 3-4 times the BW and use interpolation - decimation blocks to adapt the 48k to the LimeSDR sample rate. You may have to reduce the BW to avoid CPU overload.
Cornie

ewaldo · 10 July 2017 12:31

I have found 5M on the TX and 1.5M on the RX is the lowest I can go without getting some sort of error like

RuntimeError: RxLPF frequency out of range, available range from 1.4e+06 to 1.3e+08 MHz

Any clue on how I can significantly reduce the BW?

mzs · 10 July 2017 13:26

From the “LMS7002M DataSheet” -
“RX analog filters are tunable from 0.7 MHz to 80 MHz.”
“The TX filtering chain pass band is tunable from 2 MHz to 80 MHz”

So 48kHz samplerates in your flowgraphs is not good.

Those error messages are coming from here at a guess, and the limits look to be slightly different than those defined in the LMS7002M datasheet:

github.com

myriadrf/LimeSuite/blob/master/src/lms7002m/LMS7002M_filtersCalibration.cpp#L24


#include "MCU_BD.h"
#include "mcu_programs.h"
#include "Logger.h"

#ifdef _MSC_VER
#include <ciso646>
#endif
using namespace lime;

//rx lpf range limits
static const float_type RxLPF_RF_LimitLow = 1.4e6;
static const float_type RxLPF_RF_LimitHigh = 130e6;

//tx lpf range limits
const float_type TxLPF_RF_LimitLow = 5e6;
const float_type TxLPF_RF_LimitLowMid = 40e6;
const float_type TxLPF_RF_LimitMidHigh = 50e6;
const float_type TxLPF_RF_LimitHigh = 130e6;

LMS7002M_RegistersMap *LMS7002M::BackupRegisterMap(void)
{

github.com

myriadrf/LimeSuite/blob/master/src/lms7002m/LMS7002M_filtersCalibration.cpp#L109


    lime::debug("MCU Ref. clock: %g MHz", refClk / 1e6);
    //set bandwidth for MCU to read from register, value is integer stored in MHz
    mcuControl->SetParameter(MCU_BD::MCU_BW, rx_lpf_freq_RF);
    mcuControl->RunProcedure(5);

    status = mcuControl->WaitForMCU(1000);
    if(status != MCU_BD::MCU_NO_ERROR)
    {
        lime::error("Tune Rx Filter: MCU error %i (%s)", status, MCU_BD::MCUStatusMessage(status));
        return -1;
    }
    //sync registers to cache
    std::vector<uint16_t> regsToSync = {0x0112, 0x0117, 0x011A, 0x0116, 0x0118, 0x0114, 0x0019, 0x0115};
    for(const auto addr : regsToSync)
        this->SPI_read(addr, true);

    return status;
}

int LMS7002M::TuneTxFilter(const float_type tx_lpf_freq_RF)
{

github.com

myriadrf/LimeSuite/blob/master/src/lms7002m/LMS7002M_filtersCalibration.cpp#L526


/**
@file	LMS7002M_filtersCalibration.cpp
@author Lime Microsystems (www.limemicro.com)
@brief	Implementation of LMS7002M transceiver filters calibration algorithms
*/

#include "LMS7002M.h"
#include "IConnection.h"
#include "Logger.h"
#include "LMS7002M_RegistersMap.h"
#include <cmath>
#include <iostream>
#include <assert.h>
#include "MCU_BD.h"
#include "mcu_programs.h"
#include "Logger.h"

#ifdef _MSC_VER
#include <ciso646>
#endif
using namespace lime;

//rx lpf range limits
static const float_type RxLPF_RF_LimitLow = 1.4e6;
static const float_type RxLPF_RF_LimitHigh = 130e6;

//tx lpf range limits
const float_type TxLPF_RF_LimitLow = 5e6;
const float_type TxLPF_RF_LimitLowMid = 40e6;
const float_type TxLPF_RF_LimitMidHigh = 50e6;
const float_type TxLPF_RF_LimitHigh = 130e6;

LMS7002M_RegistersMap *LMS7002M::BackupRegisterMap(void)
{
    //BackupAllRegisters(); return NULL;
    auto backup = new LMS7002M_RegistersMap();
    Channel chBck = this->GetActiveChannel();
    this->SetActiveChannel(ChA);
    *backup = *mRegistersMap;
    this->SetActiveChannel(chBck);
    return backup;
}

void LMS7002M::RestoreRegisterMap(LMS7002M_RegistersMap *backup)
{
    //RestoreAllRegisters(); return;
    Channel chBck = this->GetActiveChannel();

    for (int ch = 0; ch < 2; ch++)
    {
        //determine addresses that have been changed
        //and restore backup to the main register map
        std::vector<uint16_t> restoreAddrs, restoreData;
        for (const uint16_t addr : mRegistersMap->GetUsedAddresses(ch))
        {
            uint16_t original = backup->GetValue(ch, addr);
            uint16_t current = mRegistersMap->GetValue(ch, addr);
            mRegistersMap->SetValue(ch, addr, original);

            if (ch == 1 and addr < 0x0100) continue;
            if (original == current) continue;
            restoreAddrs.push_back(addr);
            restoreData.push_back(original);
        }

        //bulk write the original register values from backup
        this->SetActiveChannel((ch==0)?ChA:ChB);
        SPI_write_batch(restoreAddrs.data(), restoreData.data(), restoreData.size(), true);
    }

    //cleanup
    delete backup;
    backup = nullptr;
    this->SetActiveChannel(chBck);
}

int LMS7002M::TuneRxFilter(float_type rx_lpf_freq_RF)
{
    int status;
    if(RxLPF_RF_LimitLow > rx_lpf_freq_RF || rx_lpf_freq_RF > RxLPF_RF_LimitHigh)
        return ReportError(ERANGE, "RxLPF frequency out of range, available range from %g to %g MHz", RxLPF_RF_LimitLow/1e6, RxLPF_RF_LimitHigh/1e6);

    uint8_t g_tia = Get_SPI_Reg_bits(LMS7param(G_TIA_RFE));
    if(g_tia == 1 && rx_lpf_freq_RF < 4e6)
    {
        rx_lpf_freq_RF = 4e6;
        Log(LOG_WARNING, "Rx LPF min bandwidth is 4MHz when TIA gain is set to -12 dB");
    }

    if(mcuControl->ReadMCUProgramID() != MCU_ID_CALIBRATIONS_SINGLE_IMAGE)
    {
        if((status = mcuControl->Program_MCU(mcu_program_lms7_dc_iq_calibration_bin, IConnection::MCU_PROG_MODE::SRAM)))
            return ReportError(status, "Tune Rx Filter: failed to program MCU");
    }

    //set reference clock parameter inside MCU
    long refClk = GetReferenceClk_SX(false);
    mcuControl->SetParameter(MCU_BD::MCU_REF_CLK, refClk);
    lime::debug("MCU Ref. clock: %g MHz", refClk / 1e6);
    //set bandwidth for MCU to read from register, value is integer stored in MHz
    mcuControl->SetParameter(MCU_BD::MCU_BW, rx_lpf_freq_RF);
    mcuControl->RunProcedure(5);

    status = mcuControl->WaitForMCU(1000);
    if(status != MCU_BD::MCU_NO_ERROR)
    {
        lime::error("Tune Rx Filter: MCU error %i (%s)", status, MCU_BD::MCUStatusMessage(status));
        return -1;
    }
    //sync registers to cache
    std::vector<uint16_t> regsToSync = {0x0112, 0x0117, 0x011A, 0x0116, 0x0118, 0x0114, 0x0019, 0x0115};
    for(const auto addr : regsToSync)
        this->SPI_read(addr, true);

    return status;
}

int LMS7002M::TuneTxFilter(const float_type tx_lpf_freq_RF)
{
    int status;

    if(tx_lpf_freq_RF < TxLPF_RF_LimitLow || tx_lpf_freq_RF > TxLPF_RF_LimitHigh)
        return ReportError(ERANGE, "Tx lpf(%g MHz) out of range %g-%g MHz and %g-%g MHz", tx_lpf_freq_RF/1e6,
                        TxLPF_RF_LimitLow/1e6, TxLPF_RF_LimitLowMid/1e6,
                        TxLPF_RF_LimitMidHigh/1e6, TxLPF_RF_LimitHigh/1e6);
    //calculate intermediate frequency
    float_type tx_lpf_IF = tx_lpf_freq_RF/2;
    if(tx_lpf_freq_RF > TxLPF_RF_LimitLowMid && tx_lpf_freq_RF < TxLPF_RF_LimitMidHigh)
    {
        Log(LOG_WARNING, "Tx lpf(%g MHz) out of range %g-%g MHz and %g-%g MHz. Setting to %g MHz", tx_lpf_freq_RF/1e6,
                        TxLPF_RF_LimitLow/1e6, TxLPF_RF_LimitLowMid/1e6,
                        TxLPF_RF_LimitMidHigh/1e6, TxLPF_RF_LimitHigh/1e6,
                        TxLPF_RF_LimitMidHigh/1e6);
        tx_lpf_IF = TxLPF_RF_LimitMidHigh/2;
    }

    if (!controlPort){
        lime::error("Tune Tx Filter: No device connected");
        return -1;
    }

    if(mcuControl->ReadMCUProgramID() != MCU_ID_CALIBRATIONS_SINGLE_IMAGE)
    {
        if((status = mcuControl->Program_MCU(mcu_program_lms7_dc_iq_calibration_bin, IConnection::MCU_PROG_MODE::SRAM)))
            return ReportError(status, "Tune Tx Filter: failed to program MCU");
    }

    int ind = this->GetActiveChannelIndex()%2;
    opt_gain_tbb[ind] = -1;

    //set reference clock parameter inside MCU
    long refClk = GetReferenceClk_SX(false);
    mcuControl->SetParameter(MCU_BD::MCU_REF_CLK, refClk);
    lime::debug("MCU Ref. clock: %g MHz", refClk / 1e6);
    //set bandwidth for MCU to read from register, value is integer stored in MHz
    mcuControl->SetParameter(MCU_BD::MCU_BW, tx_lpf_freq_RF);
    mcuControl->RunProcedure(6);

    status = mcuControl->WaitForMCU(1000);
    if(status != MCU_BD::MCU_NO_ERROR)
    {
        lime::error("Tune Tx Filter: MCU error %i (%s)", status, MCU_BD::MCUStatusMessage(status));
        return -1;
    }
    //sync registers to cache
    std::vector<uint16_t> regsToSync = {0x0105, 0x0106, 0x0109, 0x010A, 0x010B};
    for(const auto addr : regsToSync)
        this->SPI_read(addr, true);

    if(tx_lpf_IF <= TxLPF_RF_LimitLowMid/2)
        Log(LOG_INFO, "Filter calibrated. Filter order-4th, filter bandwidth set to %g MHz."
            "Real pole 1st order filter set to 2.5 MHz. Preemphasis filter not active", tx_lpf_IF/1e6 * 2);
    else
        Log(LOG_INFO, "Filter calibrated. Filter order-2nd, set to %g MHz", tx_lpf_IF/1e6 * 2);
    return 0;
}

This file has been truncated. show original

github.com

myriadrf/LimeSuite/blob/master/src/lms7002m/LMS7002M_filtersCalibration.cpp#L873


/**
@file	LMS7002M_filtersCalibration.cpp
@author Lime Microsystems (www.limemicro.com)
@brief	Implementation of LMS7002M transceiver filters calibration algorithms
*/

#include "LMS7002M.h"
#include "IConnection.h"
#include "Logger.h"
#include "LMS7002M_RegistersMap.h"
#include <cmath>
#include <iostream>
#include <assert.h>
#include "MCU_BD.h"
#include "mcu_programs.h"
#include "Logger.h"

#ifdef _MSC_VER
#include <ciso646>
#endif
using namespace lime;

//rx lpf range limits
static const float_type RxLPF_RF_LimitLow = 1.4e6;
static const float_type RxLPF_RF_LimitHigh = 130e6;

//tx lpf range limits
const float_type TxLPF_RF_LimitLow = 5e6;
const float_type TxLPF_RF_LimitLowMid = 40e6;
const float_type TxLPF_RF_LimitMidHigh = 50e6;
const float_type TxLPF_RF_LimitHigh = 130e6;

LMS7002M_RegistersMap *LMS7002M::BackupRegisterMap(void)
{
    //BackupAllRegisters(); return NULL;
    auto backup = new LMS7002M_RegistersMap();
    Channel chBck = this->GetActiveChannel();
    this->SetActiveChannel(ChA);
    *backup = *mRegistersMap;
    this->SetActiveChannel(chBck);
    return backup;
}

void LMS7002M::RestoreRegisterMap(LMS7002M_RegistersMap *backup)
{
    //RestoreAllRegisters(); return;
    Channel chBck = this->GetActiveChannel();

    for (int ch = 0; ch < 2; ch++)
    {
        //determine addresses that have been changed
        //and restore backup to the main register map
        std::vector<uint16_t> restoreAddrs, restoreData;
        for (const uint16_t addr : mRegistersMap->GetUsedAddresses(ch))
        {
            uint16_t original = backup->GetValue(ch, addr);
            uint16_t current = mRegistersMap->GetValue(ch, addr);
            mRegistersMap->SetValue(ch, addr, original);

            if (ch == 1 and addr < 0x0100) continue;
            if (original == current) continue;
            restoreAddrs.push_back(addr);
            restoreData.push_back(original);
        }

        //bulk write the original register values from backup
        this->SetActiveChannel((ch==0)?ChA:ChB);
        SPI_write_batch(restoreAddrs.data(), restoreData.data(), restoreData.size(), true);
    }

    //cleanup
    delete backup;
    backup = nullptr;
    this->SetActiveChannel(chBck);
}

int LMS7002M::TuneRxFilter(float_type rx_lpf_freq_RF)
{
    int status;
    if(RxLPF_RF_LimitLow > rx_lpf_freq_RF || rx_lpf_freq_RF > RxLPF_RF_LimitHigh)
        return ReportError(ERANGE, "RxLPF frequency out of range, available range from %g to %g MHz", RxLPF_RF_LimitLow/1e6, RxLPF_RF_LimitHigh/1e6);

    uint8_t g_tia = Get_SPI_Reg_bits(LMS7param(G_TIA_RFE));
    if(g_tia == 1 && rx_lpf_freq_RF < 4e6)
    {
        rx_lpf_freq_RF = 4e6;
        Log(LOG_WARNING, "Rx LPF min bandwidth is 4MHz when TIA gain is set to -12 dB");
    }

    if(mcuControl->ReadMCUProgramID() != MCU_ID_CALIBRATIONS_SINGLE_IMAGE)
    {
        if((status = mcuControl->Program_MCU(mcu_program_lms7_dc_iq_calibration_bin, IConnection::MCU_PROG_MODE::SRAM)))
            return ReportError(status, "Tune Rx Filter: failed to program MCU");
    }

    //set reference clock parameter inside MCU
    long refClk = GetReferenceClk_SX(false);
    mcuControl->SetParameter(MCU_BD::MCU_REF_CLK, refClk);
    lime::debug("MCU Ref. clock: %g MHz", refClk / 1e6);
    //set bandwidth for MCU to read from register, value is integer stored in MHz
    mcuControl->SetParameter(MCU_BD::MCU_BW, rx_lpf_freq_RF);
    mcuControl->RunProcedure(5);

    status = mcuControl->WaitForMCU(1000);
    if(status != MCU_BD::MCU_NO_ERROR)
    {
        lime::error("Tune Rx Filter: MCU error %i (%s)", status, MCU_BD::MCUStatusMessage(status));
        return -1;
    }
    //sync registers to cache
    std::vector<uint16_t> regsToSync = {0x0112, 0x0117, 0x011A, 0x0116, 0x0118, 0x0114, 0x0019, 0x0115};
    for(const auto addr : regsToSync)
        this->SPI_read(addr, true);

    return status;
}

int LMS7002M::TuneTxFilter(const float_type tx_lpf_freq_RF)
{
    int status;

    if(tx_lpf_freq_RF < TxLPF_RF_LimitLow || tx_lpf_freq_RF > TxLPF_RF_LimitHigh)
        return ReportError(ERANGE, "Tx lpf(%g MHz) out of range %g-%g MHz and %g-%g MHz", tx_lpf_freq_RF/1e6,
                        TxLPF_RF_LimitLow/1e6, TxLPF_RF_LimitLowMid/1e6,
                        TxLPF_RF_LimitMidHigh/1e6, TxLPF_RF_LimitHigh/1e6);
    //calculate intermediate frequency
    float_type tx_lpf_IF = tx_lpf_freq_RF/2;
    if(tx_lpf_freq_RF > TxLPF_RF_LimitLowMid && tx_lpf_freq_RF < TxLPF_RF_LimitMidHigh)
    {
        Log(LOG_WARNING, "Tx lpf(%g MHz) out of range %g-%g MHz and %g-%g MHz. Setting to %g MHz", tx_lpf_freq_RF/1e6,
                        TxLPF_RF_LimitLow/1e6, TxLPF_RF_LimitLowMid/1e6,
                        TxLPF_RF_LimitMidHigh/1e6, TxLPF_RF_LimitHigh/1e6,
                        TxLPF_RF_LimitMidHigh/1e6);
        tx_lpf_IF = TxLPF_RF_LimitMidHigh/2;
    }

    if (!controlPort){
        lime::error("Tune Tx Filter: No device connected");
        return -1;
    }

    if(mcuControl->ReadMCUProgramID() != MCU_ID_CALIBRATIONS_SINGLE_IMAGE)
    {
        if((status = mcuControl->Program_MCU(mcu_program_lms7_dc_iq_calibration_bin, IConnection::MCU_PROG_MODE::SRAM)))
            return ReportError(status, "Tune Tx Filter: failed to program MCU");
    }

    int ind = this->GetActiveChannelIndex()%2;
    opt_gain_tbb[ind] = -1;

    //set reference clock parameter inside MCU
    long refClk = GetReferenceClk_SX(false);
    mcuControl->SetParameter(MCU_BD::MCU_REF_CLK, refClk);
    lime::debug("MCU Ref. clock: %g MHz", refClk / 1e6);
    //set bandwidth for MCU to read from register, value is integer stored in MHz
    mcuControl->SetParameter(MCU_BD::MCU_BW, tx_lpf_freq_RF);
    mcuControl->RunProcedure(6);

    status = mcuControl->WaitForMCU(1000);
    if(status != MCU_BD::MCU_NO_ERROR)
    {
        lime::error("Tune Tx Filter: MCU error %i (%s)", status, MCU_BD::MCUStatusMessage(status));
        return -1;
    }
    //sync registers to cache
    std::vector<uint16_t> regsToSync = {0x0105, 0x0106, 0x0109, 0x010A, 0x010B};
    for(const auto addr : regsToSync)
        this->SPI_read(addr, true);

    if(tx_lpf_IF <= TxLPF_RF_LimitLowMid/2)
        Log(LOG_INFO, "Filter calibrated. Filter order-4th, filter bandwidth set to %g MHz."
            "Real pole 1st order filter set to 2.5 MHz. Preemphasis filter not active", tx_lpf_IF/1e6 * 2);
    else
        Log(LOG_INFO, "Filter calibrated. Filter order-2nd, set to %g MHz", tx_lpf_IF/1e6 * 2);
    return 0;
}

This file has been truncated. show original

Another thing you may want to look into if the noise is still present using sensible sample rates is to try a USB cable with better shielding, noise could be coming from USB 3.0. Or from the PC, try moving the LimeSDR further away.

Cornie · 10 July 2017 19:24

@ewaldo
The LMS7002M has internal interpolation - decimation filters up to a factor of 32. Don’t know if you can use them with the osmocom source - sink blocks. Fact is that it would be very usefull to have additional interpolation filtering in the FPGA. For low HF frequencies we are forced to use filter TX filter BW of 30 MHz. For those BW there are only second order lowpass filters available. So for avoiding aliasing sample rates of at least 100 -200 msps would be needed. Even with the internal interpolation filters the USB and the PC must provide sample rates that are significantly higher than the normal 48 or 192 ksps TX sample rates of hamradio SDR programs. That is probably the reason that it takes so long the get some TX SDR programs adapted for the LimeSDR.
Cornie