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RF cable assembly power

Author: Date:1/6/2020 7:21:47 PM
    The transmitter dynamic range of the RF cable assembly characterizes the maximum transmit power and minimum transmit power of the transmitter "without compromising other transmit metrics."Does not damage other emission indicators” appears to be very broad. If you look at the main effects, you can understand that the transmitter linearity is not impaired at the maximum transmit power, and the signal-to-noise ratio of the output signal is maintained at the minimum transmit power.

    At maximum transmit power, the transmitter output tends to approach the nonlinear regions of active devices at all levels (especially the final amplifiers), and the often occurring nonlinearities are spectral leakage and regeneration (ACLR/ACPR/SEM), modulation errors ( PhaseError/EVM). At this point, the most embarrassing is basically the transmitter linearity, this part should be better understood.

    At the minimum transmit power, the useful signal from the transmitter is close to the noise floor of the transmitter, and there is even the danger of being "submerged" in the noise of the transmitter. What needs to be guaranteed at this time is the signal-to-noise ratio (SNR) of the output signal. In other words, the lower the noise floor of the transmitter at the minimum transmission power, the better.

    One thing happened in the lab: When engineers tested ACLR, they found that the power reduction ACLR was even worse (the normal understanding is that ACLR should improve with the output power reduction). At the time, the first reaction was that the instrument had a problem. But the result of testing another instrument is still the same. The guidance given is to test the EVM at low output power and find that the EVM performance is very poor; the judgment may be that the noise floor at the entrance of the RF link is very high, and the corresponding SNR is obviously poor. The main component of the ACLR is not the amplifier. The spectrum is reproduced, but the baseband noise amplified by the amplifier link.