A. Khanifar | 2012 |
Download original file. PROBLEM STATEMENT
A SIMPLIFIED TRANSISTOR MODEL
- In LTE the maximum BW of a single modulated carrier is <=20MHz 3GPP in Release 8/9
- LTE-Advanced Rel-10 has provisions for aggregation of up to 5 DL carriers.
- Two or more carriers can be aggregated to support wider transmission of up to100MHz
- Spectrum deployment can be contiguous or non-contiguous
- Higher instantaneous BW may be required due to CA or infrastructure sharing and multi-band operations.
- So wide instantaneous signal BW is the new challenge in infrastructure design.
A SIMPLIFIED TRANSISTOR MODEL
IMD GENERTION MECHANISM
THE ANALYSIS
Assuming a 3rd order non-linearity:
Assuming a 3rd order non-linearity:
If we have a two non-contiguous carriers of 1 and 2 where 2> 1
PA 3rd order nonlinearity given in generates the 6-terms in-band inter modulations components and these are grouped together to ease the analysis:
The 2nd batch of IMD terms are generated at 2 1- 2 and 2 2- 1
However in addition, the same IMD terms are replicated at carrier frequencies and given as:
POSSIBLE LINEARIZATION SCHEMES
Open-loop linearization scheme:
Open-loop linearization scheme:
PRACTICAL RESULTS
CONCLUSIONS
- DPD Feedback processing bandwidth reduction is desirable as:
- Amplitude variations can hinder broadband linearization Eliminates the need for equalizer and calibration requirements
- A closer examination of IMD generation mechanism can lead to schemes where feedback BW can be significantly reduced
- The technique would be particularly attractive in non-contiguous carrier