Gain Imb (Digital Demod)

Gain Imb (IQ Gain Imbalance) compares the gain of the I signal with the gain of the Q signal, as follows:

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The effects of IQ gain imbalance are best viewed in constellation diagrams where the width of the constellation diagram is different than its height.

Gain imbalance may be a positive or negative value because it is expressed as a logarithmic value. The gain imbalance is always positive if averaging is ON and Sync Search is OFF.

For non-rectangular formats (such as 8-PSK Phase Shift Keying: A broad classification of modulation techniques where the information to be transmitted is contained in the phase of the carrier wave. or pi/4 DQPSK Differential Quadrature Phase Shift Keying: QPSK modulation using differential encoding of the digital information stream.), IQ Gain Imbalance may look like Quadrature Skew, and vice-versa. This occurs when the VSA is phase locked to an orientation that is different than that of the modulator. To ensure the same phase orientation, use Constellation Sync Search. The digital demod Rotation compensate parameter can also be used to swap the IQ Gain Imbalance and Quadrature Skew data results.

Gain Imb is unavailable when demodulating FSK Frequency Shift Keying: A form of modulation using multiple carrier frequencies to carry the digital information. The most common is the two frequency FSK system using the two frequencies to carry the binary ones and zeros. or VSB signals.