IQGainImb (802.11n/ac/ax/be)
(IQ Gain Imbalance) compares the gain of the I signal with the gain of the Q signal, as follows:
IQ gain imbalance is the ratio of the gain of the in-phase (I) portion of the signal to the gain of the quadrature phase (Q) portion of the signal at a point in the time signal. Because Gain Imbalance is expressed as a logarithmic value, it may have a positive or negative value.
The metric is computed by the VSA in the frequency domain and averaged over the symbols in the Measurement Interval. This is done for computational efficiency. An effect of performing the calculation in the frequency domain is that the IQ gain imbalance metric only includes the part of the symbol in TFFT time period.
Gain imbalance for OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. demodulation differs from gain imbalance for single carrier modulation in that gain imbalance does not show up in the constellation diagram as a width different than height. This is because OFDM constellations are in the frequency domain instead of in the time domain. In an OFDM signal, gain imbalance causes each subcarrier to interfere with the corresponding subcarrier on the other side of the center frequency, causing each constellation point to spread into a miniature picture of the entire constellation.
In MIMO Multiple Input, Multiple Output: A physical layer (PHY) configuration in which both transmitter and receiver use multiple antennas. systems, Gain Imbalance can also cause interference between the data streams in signals that have more than one data stream.
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