Application Note 5499
November 2013
Unlike many other cellular standards, NCDMA is required by the 3GPP2 standard to perform spectrum inversion in the physical layer before transmission and after reception. With today’s vast selection of radio frequency (RF) transceivers and baseband processors, it is easy to imagine how one could come across a set of RF transceiver and baseband processor that have mismatched spectrum in the transmit and receive paths. This simple oversight will result in noncompliance to the 3GPP2 standard and failure to demodulate. However, there are a few simple techniques that can help determine if spectrum inversion has been performed on a signal.
This tutorial will help design engineers manage spectrum inversion to comply with the 3GPP2 standard. It is important for system integrators to remember that the 3GPP2 standard requires NCDMA, unlike many other cellular standards, to perform spectrum inversion in the physical layer (generally within the radio frequency (RF) IC) prior to transmission and after reception. With today’s vast selection of RF transceivers and baseband processors, it is easy to imagine how one could find a set of a RF transceiver and baseband processor that has mismatched spectrum in the transmit and receive paths. This simple oversight will result in noncompliance with the 3GPP2 standard and failure to demodulate. However, there are a few simple techniques that can help determine if spectrum inversion has been performed on a signal. This tutorial presents three techniques that perform spectrum inversion on RF transceivers that do not have built-in spectrum inversion.
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Related datasheets:
WCDMA I/Q modulation and demodulation format. Note that the Q channel is multiplied by a negative phase LO, i.e., -sin(ωLOt), as shown in red.
