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One issue about SAW filter

One issue about SAW filter<br><br>One issue about SAW filter

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One issue about SAW filter

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  1. Primary ANT Diversity ANT Transceiver SIMO is also known as receiving diversity, which is often used to enable a receiver system that receives signals from many independent sources to combat the effects of fading and enhance the sensitivity. For example, if the sensitivity is -97 dBm with a single antenna, the sensitivity would be -100 dBm approximately with two antennas [1]. 1

  2. According to sensitivity formula: The lower overall noise figure can improve sensitivity. Nevertheless, we’ve changed a SAW filter with a smaller loss on the diversity path and found that the sensitivity degraded. 2

  3. It’s well known that there’re probably intermodulation and harmonic distortion issue in the CA application [1]. For example: B17 X 3 -> B4 B17 X 3 -> B4 B8 X 2 -> B3 B8 X 2 -> B3 B8 X 3 -> B7 B8 X 3 -> B7 2B1 – B3 = B1 2B1 – B3 = B1 Primary ANT Diversity ANT Transceiver B17 transmitting signal may radiate into B4 diversity antenna, and generate third- order harmonic distortion through the nonlinearity of DSM, thereby interfering with the received B4 signal. Consequently, in addition to antenna-to-antenna isolation and the linearity of the DSM, the out-band rejection of the SAW filter is vital as well, which can determine how much the sensitivity degrades. 3

  4. Primary ANT Diversity ANT Transceiver Additionally, the 2nd order harmonic distortion of B1 transmitting signal and the B3 transmitting signal may radiate into B1 diversity antenna, and generate third- order intermodulation distortion through the nonlinearity of DSM, thereby interfering with the received B1 signal. Likewise, the out-band rejection of the SAW filter is vital as well, which can determine how much the sensitivity degrades. Therefore, in the CA application, both loss and out-band rejection of a SAW filter are vital for sensitivity. 4

  5. Reference [1] Carrier Aggregation Discussion 5

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