Gain Imb (GSM/EDGE/EDGE Evolution)
Gain Imb(IQ Gain Imbalance) compares the gain of the I signal with the gain of the Q signal, as follows:
The effects of IQ gain imbalance are best viewed in constellation diagrams, where the width of the constellation diagram is different than its height.
To view the effects of IQ gain imbalance most clearly, set the IQ Constellation Style parameter to instead of , since derotating the constellation tends to obscure the effects of IQ gain imbalance by making the constellation look more symmetrical.
Due to complicated filtering, pulse shaping, and symbol rotation used in GSM Global System for Mobile Communications: Originally developed as a pan-European standard for digital mobile telephony, GSM has become the world’s most widely used mobile system. It is used on the 900 MHz and 1800 MHz frequencies in Europe, Asia and Australia, and the 1900 MHz frequency in North America and Latin America./EDGE Enhanced Data for Global Evolution: A technology that gives GSMA and TDMA similar capacity to handle services for the third generation of mobile telephony. EDGE was developed to enable the transmission of large amounts of data at a high speed, 384 kilobits per second. (It increases available time slots and data rates over existing wireless networks.) standard and because the total length of a timeslot is a non-integral number of symbols, the absolute phase of the IQ Meas Time constellation is hard to determine exactly. This uncertainty means that for non-rectangular formats (all GSM/EDGE/EDGE Evo formats), IQ gain imbalance may look like IQ quadrature skew, and similarly IQ quadature skew can look like IQ gain imbalance when measured by the VSA. This occurs when the VSA is phase locked to an orientation that is different than that of the modulator.
See Also
