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MIMO Signal Testing Essentials

MIMO signal testing first focuses on evaluating the transmitter and receiver system to ensure high PAR signals do not cause unpredictable amplifier compression and distortion. Channel emulators are also important for testing devices under different conditions like at the cell edge or at speed. Channel sounding involves sending a known signal from the transmitter to enable the mobile device to estimate the channel characteristics, which are then sent back to the transmitter to allow it to apply the correct phase and amplitude adjustments to form beams directed at the mobile device for closed-loop MIMO systems requiring adjustment of each transmitter's phase and amplitude for beamforming.

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40 views1 page

MIMO Signal Testing Essentials

MIMO signal testing first focuses on evaluating the transmitter and receiver system to ensure high PAR signals do not cause unpredictable amplifier compression and distortion. Channel emulators are also important for testing devices under different conditions like at the cell edge or at speed. Channel sounding involves sending a known signal from the transmitter to enable the mobile device to estimate the channel characteristics, which are then sent back to the transmitter to allow it to apply the correct phase and amplitude adjustments to form beams directed at the mobile device for closed-loop MIMO systems requiring adjustment of each transmitter's phase and amplitude for beamforming.

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Anonymous BQlWtZX3I
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Testing

MIMO signal testing focuses first on the transmitter/receiver system. The random phases of the sub-
carrier signals can produce instantaneous power levels that cause the amplifier to compress,
momentarily causing distortion and ultimately symbol errors. Signals with a high PAR (peak-to-
average ratio) can cause amplifiers to compress unpredictably during transmission. OFDM signals
are very dynamic and compression problems can be hard to detect because of their noise-like
nature.[49]
Knowing the quality of the signal channel is also critical. A channel emulator can simulate how a
device performs at the cell edge, can add noise or can simulate what the channel looks like at
speed. To fully qualify the performance of a receiver, a calibrated transmitter, such as a vector signal
generator (VSG), and channel emulator can be used to test the receiver under a variety of different
conditions. Conversely, the transmitter's performance under a number of different conditions can be
verified using a channel emulator and a calibrated receiver, such as a vector signal analyzer (VSA).
Understanding the channel allows for manipulation of the phase and amplitude of each transmitter in
order to form a beam. To correctly form a beam, the transmitter needs to understand the
characteristics of the channel. This process is called channel sounding or channel estimation. A
known signal is sent to the mobile device that enables it to build a picture of the channel
environment. The mobile device sends back the channel characteristics to the transmitter. The
transmitter can then apply the correct phase and amplitude adjustments to form a beam directed at
the mobile device. This is called a closed-loop MIMO system. For beamforming, it is required to
adjust the phases and amplitude of each transmitter. In a beamformer optimized for spatial diversity
or spatial multiplexing, each antenna element simultaneously transmits a weighted combination of
two data symbols.

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