GC1115_06 Datasheet, PDF (9/82 Pages) Texas Instruments – Crest Factor Reduction Processor

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10²
GC1115
SLWS144C – FEBRUARY 2005 – REVISED JUNE 2006
Complementary Cumulative DistrFibunction
1
10
0
10
% of
samples
−1
10
CCDF Curve
After Peak
Reduction
−2
10
CCDF Curve
−3
Before Peak
10
Reduction
−4
10
0
2
4
6
8
10
12
14
Sample Power (mean sample power = 0
Figure 6. Example Complementary Cumulative Distribution Function (CCDF)
Because the GC1115 modifies samples of the input waveform during peak reduction, the peak reduction
process introduces certain distortions. The nature of these distortions is well understood and is under the user’s
control. GC1115 users have great flexibility in determining the overall distortion level. Distortion can be
quantified in several ways:
• By analyzing the spectrum of the distortion (input–output) signal
• By analyzing the out-of-band output noise level in neighboring channels (also called the adjacent channel
leakage ratio, or ACLR)
• By measuring a composite error vector magnitude (cEVM) level
• By determining the interference level (caused peak reduction) in the CDMA code noise floor; this metric is
called the peak code domain error, or PCDE
• By monitoring bit error rate (BER) at the receiver
The two dominant 3G standards, W-CDMA (3GPP) and cdma2000 (3GPP2), have developed a set of
standardized requirements for ACLR, cEVM, and PCDE. Because a wide variety of valid CDMA waveforms
exist, the 3G standards bodies have also specified a set of test waveforms called test models to verify all
elements in the downlink signal processing chain. Test models also allow BTS developers to compare the
performance of competing signal processing devices, including crest factor reduction processors, on identical
input signals.
Texas Instruments quantified GC1115 behavior with extensive 3G Test Model 1, Test Model 3, and Test Model
5 signals, and in both single-carrier and multi-carrier configurations. For all tests, TI measured the following
parameters:
• CCDF
• ACLR
• PCDE
• CEVM
The following paragraphs review the relevant 3G requirements for these parameters. Subsequent sections
present test results that demonstrate the GC1115’s ability to meet all relevant 3G requirements at output PAR
levels to 6 dB.
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