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CC1200 + SmartRF, attenuation issue at specific frequency

Maxime GUYON
Expert 1035 points


Hello,

I'm testing radio configuration to test receive sensitivity and tune RF parameters.
When I fall into a strange issue. 

First let's describe the test:

I have two SmartRF TRXeb v1.7 board, each with an evaluation module for CC120X EM at 420-470MHz band Rev 1.1.
The two RF module are linked with an RF cable and a 30dB attenuator (plugged on the SMA antenna connector).
SmartRF version is the last one 2.1.0

My RF configuration can be found attached but for resume it is

Modulation:            2-FSK
Symbol Rate:         125ksps,
Deviation:               55.999756kHz
RX filter BW:           277.777778kHz
Xtal frequency:       40.000000MHz
TX power:              -40dBm
Whitening:              ENABLED
PA ramping:           ENABLED
Sync Word count:  2 bytes
Preamble count:    3 bytes
Length config:        FIXED
Size of packet:       218

The issue is that at carrier frequency of 440.05MHz the receive sensitivity is very poor compared to the receive sensitivity of 441MHz or 445MHz.
The sensitivity at carrier frequency of 445MHz is about 7dB better than sensitivity at 440.05MHz. (I added 7dB attenuator for get same packet error rate)

Can someone explain why a small change of carrier frequency change the sensitivty drastically?
I tested with different cable and different board the issue seem to be the same.
Also the sensitivity seem to change between each RF eval module board.

Regards,

Max.

Here is the XML conf of SmartRF.
When I load this config, some parameters are not displayed well in smartRF like the FIXED mode which not display the Length of packet (need to pass to variable mode and come back to fixed mode and set back the length field to 218).

Fullscreen CONF 100K 2FSK BUG.xml Download 
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE configuration SYSTEM "C:/Program Files (x86)/Texas Instruments/SmartRF Tools/SmartRF Studio 7/config/xml/configdata.dtd"[]>
<dcpanelconfiguration>
    <Devicename>CC1200</Devicename>
    <Description>Saved configuration data</Description>
    <registersettings>
        <Register>
            <Name>AGC_CFG0</Name>
            <Value>0x80</Value>
        </Register>
        <Register>
            <Name>AGC_CFG1</Name>
            <Value>0x12</Value>
        </Register>
        <Register>
            <Name>AGC_CS_THR</Name>
            <Value>0xf6</Value>
        </Register>
        <Register>
            <Name>AGC_REF</Name>
            <Value>0x2b</Value>
        </Register>
        <Register>
            <Name>CHAN_BW</Name>
            <Value>0x43</Value>
        </Register>
        <Register>
            <Name>DCFILT_CFG</Name>
            <Value>0x4b</Value>
        </Register>
        <Register>
            <Name>DEVIATION_M</Name>
            <Value>0x6f</Value>
        </Register>
        <Register>
            <Name>FIFO_CFG</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>FREQ0</Name>
            <Value>0x8f</Value>
        </Register>
        <Register>
            <Name>FREQ1</Name>
            <Value>0x02</Value>
        </Register>
        <Register>
            <Name>FREQ2</Name>
            <Value>0x58</Value>
        </Register>
        <Register>
            <Name>FS_CAL0</Name>
            <Value>0x0e</Value>
        </Register>
        <Register>
            <Name>FS_CAL1</Name>
            <Value>0x40</Value>
        </Register>
        <Register>
            <Name>FS_CFG</Name>
            <Value>0x14</Value>
        </Register>
        <Register>
            <Name>FS_DIG0</Name>
            <Value>0x50</Value>
        </Register>
        <Register>
            <Name>FS_DIG1</Name>
            <Value>0x04</Value>
        </Register>
        <Register>
            <Name>FS_DIVTWO</Name>
            <Value>0x03</Value>
        </Register>
        <Register>
            <Name>FS_DSM0</Name>
            <Value>0x33</Value>
        </Register>
        <Register>
            <Name>FS_DVC0</Name>
            <Value>0x0f</Value>
        </Register>
        <Register>
            <Name>FS_DVC1</Name>
            <Value>0xf7</Value>
        </Register>
        <Register>
            <Name>FS_PFD</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>FS_PRE</Name>
            <Value>0x6e</Value>
        </Register>
        <Register>
            <Name>FS_REG_DIV_CML</Name>
            <Value>0x1c</Value>
        </Register>
        <Register>
            <Name>FS_SPARE</Name>
            <Value>0xac</Value>
        </Register>
        <Register>
            <Name>FS_VCO0</Name>
            <Value>0xb5</Value>
        </Register>
        <Register>
            <Name>IFAMP</Name>
            <Value>0x09</Value>
        </Register>
        <Register>
            <Name>IF_ADC0</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>IF_ADC1</Name>
            <Value>0xee</Value>
        </Register>
        <Register>
            <Name>IF_MIX_CFG</Name>
            <Value>0x1c</Value>
        </Register>
        <Register>
            <Name>IOCFG2</Name>
            <Value>0x06</Value>
        </Register>
        <Register>
            <Name>IQIC</Name>
            <Value>0x58</Value>
        </Register>
        <Register>
            <Name>MDMCFG0</Name>
            <Value>0x05</Value>
        </Register>
        <Register>
            <Name>MDMCFG1</Name>
            <Value>0x42</Value>
        </Register>
        <Register>
            <Name>MDMCFG2</Name>
            <Value>0x02</Value>
        </Register>
        <Register>
            <Name>MODCFG_DEV_E</Name>
            <Value>0x04</Value>
        </Register>
        <Register>
            <Name>MODEM_STATUS1</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>PARTNUMBER</Name>
            <Value>0x20</Value>
        </Register>
        <Register>
            <Name>PARTVERSION</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>PA_CFG1</Name>
            <Value>0x41</Value>
        </Register>
        <Register>
            <Name>PKT_CFG1</Name>
            <Value>0x43</Value>
        </Register>
        <Register>
            <Name>PKT_CFG2</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>PKT_LEN</Name>
            <Value>0xda</Value>
        </Register>
        <Register>
            <Name>PREAMBLE_CFG0</Name>
            <Value>0x8a</Value>
        </Register>
        <Register>
            <Name>PREAMBLE_CFG1</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>SYMBOL_RATE0</Name>
            <Value>0x9a</Value>
        </Register>
        <Register>
            <Name>SYMBOL_RATE1</Name>
            <Value>0x99</Value>
        </Register>
        <Register>
            <Name>SYMBOL_RATE2</Name>
            <Value>0xa9</Value>
        </Register>
        <Register>
            <Name>SYNC0</Name>
            <Value>0xd9</Value>
        </Register>
        <Register>
            <Name>SYNC1</Name>
            <Value>0xcc</Value>
        </Register>
        <Register>
            <Name>SYNC2</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>SYNC3</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>SYNC_CFG0</Name>
            <Value>0x23</Value>
        </Register>
        <Register>
            <Name>SYNC_CFG1</Name>
            <Value>0x28</Value>
        </Register>
        <Register>
            <Name>TOC_CFG</Name>
            <Value>0x03</Value>
        </Register>
        <Register>
            <Name>XOSC1</Name>
            <Value>0x03</Value>
        </Register>
        <Register>
            <Name>XOSC5</Name>
            <Value>0x0e</Value>
        </Register>
    </registersettings>
    <dcpanel>
        <Property name="m_chkRegView" role="44">2</Property>
        <Property name="m_chkCmdView" role="44">0</Property>
        <Property name="m_chkRfParameters" role="44">2</Property>
        <Property name="m_tabUserMode" role="37">1</Property>
        <Property name="m_easyModeSettings" role="33">-1</Property>
        <Property name="m_typicalSettings" role="33">-1</Property>
        <Property name="m_testFuncPanel" role="37">2</Property>
    </dcpanel>
    <rfparameters>
        <Property name="m_cmbFrontends" role="46">0</Property>
        <Property name="m_chkHGMorBYP" role="44">2</Property>
        <Property name="m_cmbEmRevs" role="46">-1</Property>
        <Property name="Xtal frequency" role="46">40.000000</Property>
    </rfparameters>
    <conttx>
        <Property name="m_rbtModulated" role="45">1</Property>
        <Property name="m_rbtUnmodulated" role="45">0</Property>
        <Property name="m_cmbDataFormat" role="46">-1</Property>
        <Property name="m_chkFreqSweep" role="44">0</Property>
        <Property name="m_chkChanSweep" role="44">0</Property>
    </conttx>
    <contrx>
        <Property name="m_cmbDataFormat" role="46">-1</Property>
        <Property name="m_chkAutoScroll" role="44">2</Property>
    </contrx>
    <packettx>
        <Property name="m_edtPacketCount" role="42">1000</Property>
        <Property name="m_edtPacketCountEsy" role="42">100</Property>
        <Property name="m_edtFixedPktLength" role="42">218</Property>
        <Property name="m_edtPacketData" role="42">37 bb e5 bc e6 47 b7 1b 88 6b 72 b8 81 47 c0 69 e6 f4 68 a1 ea 23 6a 36 9a 00 4a 68 cb 5d ac 20 50 0c 21 75 70 8c 41 74 97 e9 fa 21 4b dd 27 b9 62 3b 64 3a 72 8d 21 25 8a fc f6 83 1f 71 36 26 49 fa c7 31 30 6f 31 db c0 55 f4 6f a5 02 1f 97 73 02 1e db 24 ba d4 65 c8 4b ea 07 78 ba 66 7f 8c 4d 7f f9 0e 38 af d5 6e 78 0b ab 76 00 d0 8c 81 13 3e 8b e8 f1 a9 7c be b5 cd fc bd 7e 62 b2 7f cd f0 d4 f2 2e e5 ec 06 1b e5 dc a8 1d 61 1f f4 34 6b 53 a6 79 c8 f4 d2 02 47 6b d6 06 52 47 8c 41 c3 ca c4 9a f9 a7 f1 04 2a 0a 22 a2 fa d9 34 2e 4d 39 46 9b 5a 55 6e f9 02 5b aa 9a 5f c6 1a 73 9f e3 6c c4 13 8e 97 fc 83 3d cc d7 c5 41 a9 c9 8d 48 b1 9f 87 25 f9 64 </Property>
        <Property name="m_edtAccessAddress" role="42"></Property>
        <Property name="m_chkAddSeqNbr" role="44">0</Property>
        <Property name="m_chkInfinite" role="44">0</Property>
        <Property name="m_chkInfiniteEsy" role="44">0</Property>
        <Property name="m_rbtRandom" role="45">1</Property>
        <Property name="m_rbtText" role="45">0</Property>
        <Property name="m_rbtHex" role="45">0</Property>
        <Property name="m_chkAdvanced" role="44">0</Property>
        <Property name="m_cmbLengthConfig" role="46">0</Property>
        <Property name="m_edtFixedPktLength" role="42">218</Property>
        <Property name="m_edtBitLength" role="42">0</Property>
        <Property name="m_grp802154g" role="20">0</Property>
        <Property name="m_edt802154gPktLength" role="42">30</Property>
        <Property name="m_rbt802154g2BCrc" role="45">1</Property>
        <Property name="m_rbt802154g4BCrc" role="45">0</Property>
        <Property name="m_chk802154gWhitening" role="44">2</Property>
        <Property name="m_chkFEC" role="44">0</Property>
        <Property name="m_cmbPreambleCount" role="46">4</Property>
        <Property name="m_chkAddress" role="44">0</Property>
        <Property name="m_cmbSyncMode" role="46">1</Property>
    </packettx>
    <packetview>
        <Property name="m_edtPktLength" role="42">218</Property>
        <Property name="m_lblFrmPayload" role="41">37 bb e5 bc e6 47 b7 1b 88 6b 72 b8 81 47 c0 69 e6 f4 68 a1 ea 23 6a 36 9a 00 4a 68 cb 5d ac 20 50 0c 21 75 70 8c 41 74 97 e9 fa 21 4b dd 27 b9 62 3b 64 3a 72 8d 21 25 8a fc f6 83 1f 71 36 26 49 fa c7 31 30 6f 31 db c0 55 f4 6f a5 02 1f 97 73 02 1e db 24 ba d4 65 c8 4b ea 07 78 ba 66 7f 8c 4d 7f f9 0e 38 af d5 6e 78 0b ab 76 00 d0 8c 81 13 3e 8b e8 f1 a9 7c be b5 cd fc bd 7e 62 b2 7f cd f0 d4 f2 2e e5 ec 06 1b e5 dc a8 1d 61 1f f4 34 6b 53 a6 79 c8 f4 d2 02 47 6b d6 06 52 47 8c 41 c3 ca c4 9a f9 a7 f1 04 2a 0a 22 a2 fa d9 34 2e 4d 39 46 9b 5a 55 6e f9 02 5b aa 9a 5f c6 1a 73 9f e3 6c c4 13 8e 97 fc 83 3d cc d7 c5 41 a9 c9 8d 48 b1 9f 87 25 f9 64 </Property>
    </packetview>
    <packetrx>
        <Property name="m_edtPacketCount" role="42">100</Property>
        <Property name="m_edtPacketCountEsy" role="42">100</Property>
        <Property name="m_edtAccessAddress" role="42"></Property>
        <Property name="m_chkInfinite" role="44">0</Property>
        <Property name="m_chkInfiniteEsy" role="44">0</Property>
        <Property name="m_cmbViewFormat" role="46">0</Property>
        <Property name="m_chkSeqNbrIncluded" role="44">2</Property>
        <Property name="m_edtDumpFile" role="42"></Property>
        <Property name="m_chkAdvanced" role="44">0</Property>
        <Property name="m_chk802154gMode" role="44">0</Property>
    </packetrx>
    <commandpanel>
        <Property name="m_chkInsertLength" role="44">0</Property>
        <Property name="m_edtTxFifo" role="42"></Property>
        <Property name="m_edtRxFifo" role="42"></Property>
        <Property name="m_cmbInstrInput" role="46">-1</Property>
    </commandpanel>
    <packetRxSniffMode>
        <Property name="m_edtPreambleLength" role="42">24</Property>
        <Property name="m_edtCarrierSenseThreshold" role="42">-90</Property>
        <Property name="m_rbtRssi" role="45">1</Property>
        <Property name="m_rbtPreamble" role="45">0</Property>
    </packetRxSniffMode>
</dcpanelconfiguration>