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ADRV9008-1 - How to eliminate unwanted signal near main Carrier ?

Category: Hardware
Product Number: ADRV9008-1

We use ADRV9008-1 in our board. Our fundamental modulated waveform frequency is in C-Band frequency and is 5700MHz. Our sample rate is 122.88 MHz, and the maximum bandwith is our design is about 30 MHz. The problem is that if there is an another signal near our main carrier, it reduces the SNR and creates Bit Errors on our waveform design at spesific frequencies. To test this situation we created a setup and gave an another carrier near our main carrier by changing it's frequency and we saw that SNR decreases and creates bit errors at some frequencies. For example there is no error if the unwanted signal frequency between 5.42 GHz - 5.56 GHz or 6.04 GHz - 6.1 GHz. However if the unwanted signal frequency is between 5.56 GHz - 5.7 Ghz or 5.36 GHz - 5.28 Ghz, we saw that SNR decreases and creates bit errors at our waveform design. How can we eliminate this affect to our main carrier if there is an another carrier or unwanted signal in our inband C-band frequencies ? 

  • Have you turned on AGC ? We need to make sure  that the interfering signals are falling outside the pass band of the Digital filters and further filtering can be planned on the baseband side .

  • We use AGC on MGC mode because there are 2 external attenuautors on our design. We implemented our own AGC design and control 3 of them together according to RSSI level. 

    in_voltage0_harwaregain <-- Attenuator1 <-- Attenuator2

    And this is the rx profile ;

    * RX */

    adi,rx-profile-rx-fir-gain_db = <(-6)>;
    adi,rx-profile-rx-fir-num-fir-coefs = <72>;
    adi,rx-profile-rx-fir-coefs = /bits/ 16 <(-30) (46) (42) (51) (1) (-63) (-120) (-99) (1)(152) (241) (191) (-27) (-295) (-445) (-317) (75) (540) (758) (508) (-177) (-933) (-1258) (-794) (359)(1609) (2114) (1293) (-734) (-3002) (-4057) (-2647) (1549) (7585) (13508) (17169) (17169) (13508) (7585) (1549) (-2647) (-4057) (-3002) (-734) (1293) (2114) (1609) (359) (-794) (-1258) (-933) (-177) (508) (758) (540) (75) (-317) (-445) (-295) (-27) (191) (241) (152) (1) (-99) (-120) (-63) (1) (51) (42) (46) (-30)>;

    adi,rx-profile-rx-fir-decimation = <2>;
    adi,rx-profile-rx-dec5-decimation = <4>;
    adi,rx-profile-rhb1-decimation = <2>;
    adi,rx-profile-rx-output-rate_khz = <122880>;
    adi,rx-profile-rf-bandwidth_hz = <50000000>;
    adi,rx-profile-rx-bbf3d-bcorner_khz = <50000>;
    adi,rx-profile-rx-adc-profile = /bits/ 16 <265 146 181 90 1280 366 1257 27 1258 17 718 39 48 46 27 161 0 0 0 0 40 0 7 6 42 0 7 6 42 0 25 27 0 0 25 27 0 0 165 44 31 905>;
    adi,rx-profile-rx-ddc-mode = <0>;

    adi,rx-nco-shifter-band-a-input-band-width_khz = <0>;
    adi,rx-nco-shifter-band-a-input-center-freq_khz = <0>;
    adi,rx-nco-shifter-band-a-nco1-freq_khz = <0>;
    adi,rx-nco-shifter-band-a-nco2-freq_khz = <0>;
    adi,rx-nco-shifter-band-binput-band-width_khz = <0>;
    adi,rx-nco-shifter-band-binput-center-freq_khz = <0>;
    adi,rx-nco-shifter-band-bnco1-freq_khz = <0>;
    adi,rx-nco-shifter-band-bnco2-freq_khz = <0>;

    adi,rx-gain-control-gain-mode = <0>;
    adi,rx-gain-control-rx1-gain-index = <255>;
    adi,rx-gain-control-rx2-gain-index = <255>;
    adi,rx-gain-control-rx1-max-gain-index = <255>;
    adi,rx-gain-control-rx1-min-gain-index = <195>;
    adi,rx-gain-control-rx2-max-gain-index = <255>;
    adi,rx-gain-control-rx2-min-gain-index = <195>;

    adi,rx-settings-framer-sel = <0>;
    adi,rx-settings-rx-channels = <0>;

  • What are the interferer and the wanted signal power levels? How much attenuation is there from the external attenuators? As the interferer signal levels are very close to the wanted signal level, the demodulation depends on the SFDR.