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  1. [SOLVED]Closed: Re: Why are all reference sensitivity requirement of all bands different in WCDMA (UM

    Thanks for your reply.:-o
  2. [SOLVED]Closed: Why are all reference sensitivity requirement of all bands different in WCDMA (UMTS)

    155607

    155608

    As shown above, the reference sensitivity requirement:

    B1: -106.7
    B2: -104.7
    B3: -103.7
    B4: -106.7
  3. [SOLVED]Closed: Re: Why is there always a shunt inductor for SMD (Surface Mount Device) antenna?

    vfone, volker@muehlhaus

    Thanks for your reply.

    I think perhaps this design is due to the impedance of the antenna itself.
  4. [SOLVED]Closed: Re: Why is there always a shunt inductor for SMD (Surface Mount Device) antenna?

    Sorry for the late reply.


    https://gofile.io/?c=IqWDQx

    Antenova, plz see page 15

    Pulse, plz see page 7
  5. [SOLVED]Closed: Re: Why is there always a shunt inductor for SMD (Surface Mount Device) antenna?

    Sorry, perhaps my previous photo didn't expound my question well.


    155431
    155432


    The two photos are from datasheet.

    As shown above, C1 is just the shunt component, and which is always...
  6. [SOLVED]Closed: Why is there always a shunt inductor for SMD (Surface Mount Device) antenna?

    155430

    Hi,

    As shown above,

    there is always a shunt inductor in SMD (Surface Mount Device) antenna design.

    I know it's for tuning.
  7. Closed: What makes the difference in data rates between FDD and TDD ??

    Hi,

    For the description:

    Due to the differences between
    FDD and TDD, the same amount of aggregated bandwidth results in different downlink and uplink data rates.
    Therefore, 40-MHz aggregated...
  8. Replies
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    905

    [SOLVED]Closed: Which Photo is carrier Leakage ?

    HI,


    142205
    142206
    142207


    As shown above, there is carrier leakage caused by a DC offset in I/Q signal.
    And, in terms of spectrum, the carrier leakage component is at the center of...
  9. Closed: Why do we have to consider GSM Power Amplifier Linearity?

    Hi,

    Of course, the better the linearity of PA is, the better the TX performance will be.

    Nevertheless, GSM adopts GMSK modulation, which is constant envelope.

    In other words, it doesn't...
  10. [SOLVED]Closed: Re: Why does series inductor at GPS LNA input improve sensitivity?

    Thanks your detailed reply.
    I know what the blind spot is.
    :-o
  11. [SOLVED]Closed: Re: Why does series inductor at GPS LNA input improve sensitivity?

    Hi,

    Thanks for your reply. My thought is as below:


    1. According to Friis formula :

    138427
  12. [SOLVED]Closed: Why does series inductor at GPS LNA input improve sensitivity?

    BGA231L7 of Infineon

    138396
    138397





    ALM-2412 of AVAGO
  13. Closed: Why does more complex modulation lead to higher data rate and PAPR ?

    Hi,

    We all know that more complex modulation leads to higher data rate and PAPR.

    For example,

    256 QAM has higher data rate and PAPR than 64 QAM.

    But, why ?
  14. Closed: Re: Why does IM2 contribute to the noise floor at LNA input ???

    But I wonder why IM2 appears at LNA input.

    IM2 made up of Tx and RX is due to LNA's and mixer's nonlinearity.
    (I leave blocker/jammer considerations aside)
    In that case, why does IM2 appear at...
  15. Closed: Why does IM2 contribute to the noise floor at LNA input ???

    Of course, for FDD(Frequency division duplex) direct-onversion receivers,
    The IM2(2 order intermodulation) contaminates the desired Rx signal due to Tx leakage, as shown below :

    130824


    ...
  16. Closed: Why do some transmitter chain designs adopt a stand-alone GSM PA ????

    Hi, from the following link :
    http://datasheet.octopart.com/SKY77629-13-Skyworks-Solutions-datasheet-16052582.pdf

    A MMPA (MultiMode MultiBand Power Amplifier) can cover GSM / WCDMA / LTE
    ...
  17. [SOLVED]Closed: How to know the PCB layout trace length by VNA Polar diagram ???

    Hi, from the following link :
    ...
  18. Closed: How to calculate the necessary isolation of duplexer ??

    For FDD communication system, there is Tx leakage

    If we don't want desense issue, we need enough isolation of duplexer.

    In general, e.g. CDMA or WCDMA, the isolation should be at least 50 dB.
    ...
  19. Closed: Re: Two PLL/VCO used for WCDMA RF circuit?

    Generally speaking, Qualcomm adopts Zero-IF architecture.............
  20. Replies
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    1,127

    Closed: Re: 25MHz LPF help with design

    If your passband is from 1MHz to 25 MHz.

    And you hope for less inductors used at the expense of harmonics rejection.

    Perhaps you can try the simple 5 order LPF firstly.


    122044

    Insertion...
  21. Replies
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    Closed: Re: 25MHz LPF help with design

    I misunderstood that your center frequency is only 25 MHz.

    If so, you can try this BPF firstly.

    122038

    Insertion loss of 14 MHz : 0.237 dB
    Insertion loss of 25 MHz : 0.475 dB
    Insertion...
  22. Closed: Higher order modulation scheme with more strict EVM requirement ??

    Hi,

    In terms of PAR, higher order modulation scheme, more susceptible to nonlinearity distortion.

    Besides, in terms of modulator, higher order modulation scheme, more susceptible to I/Q...
  23. Closed: Re: How to prove the bandwidth of intermodulation is related to its order ?

    Okay~! Thanks you.
  24. Replies
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    Closed: Re: 25MHz LPF help with design

    122035

    you can try this toplogy first.

    Because 25 MHz is too close to 28 MHz,

    It is difficult to achieve low insertion loss for 25 MHz and high attenuation for 28 MHz simultaneously.
    ...
  25. Replies
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    [SOLVED]Closed: Re: Radiation issue on one frequency

    In addition to L-C filter, you can also make use of pi-type filter, i.e. C-L-C, to reject the noise.

    Because pi-type filter has better noise rejection than L-type.

    However, for pi-type filter,...
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