I/Q Tuning Measurement Description; How Is An I/Q Tuning Measurement Made - Agilent Technologies 8960 10 Series Reference Manual

I/Q Tuning Measurement Description

I/Q Tuning Measurement Description

How is an I/Q Tuning Measurement Made?

The I/Q Tuning measurement is used in the production process (normally at mobile pre-test) where the I/Q
modulator of the mobile is being calibrated. The measurement is normally performed with the mobile station
in test mode and transmitting a GMSK modulated sequence of all 0s or all 1s. The mobile can be transmitting
either a bursted signal or a continuous wave signal. I/Q Tuning is not an ETSI specified measurement.
The carrier frequency is shifted up or down 67.7083 kHz by transmitting a sequence of all 0s (+67.7083 kHz)
or all 1s (-67.7083 kHz). The accuracy of the mobile's I/Q modulator is determined by measuring the level of
spurious signals relative to the desired signal (the desired signal being the carrier frequency ±67.7083 kHz).
The signals the test set measures are: the carrier frequency (Fc); Fc±67.7083 kHz; Fc±135.417 kHz;
Fc±203.125 kHz and Fc±270.833 kHz. These signals are measured at the RF IN/OUT port.
The figure below shows a typical spectrum generated by a mobile transmitting a sequence of all 0s. The peak
at the +67.7083 kHz offset is the one used as the reference.
The I/Q Tuning measurement also allows you to make an additional relative power measurement at any
frequency you want between -13.0 MHz to -1.0 MHz and +1.0 MHz to +13.0 MHz relative to the carrier
frequency.
Figure 2. Spectrum of a mobile transmitting a sequence of all 0s
-270.84 -203.13 -135.42 -67.71 0 67.71 135.42 203.13 270.84
Offset Frequency (kHz)
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