ETTC'2003 - SEE

3.7 NOISE POWER RATIO (NPR) BENCH
In addition to the BST, a NPR bench has been developed to characterise the
behaviour of TWTAs and SSPAs from X to Ka band. This bench provides
accurate measurement (reproducibility ≈ 0.3dB), on a large dynamic range (up
to 35 dB), of wideband NPR (up to 250 MHz) from 1 GHz up to 30 GHz.
The main objective of this bench is to optimise the operating point of power
amplifiers in order to minimise power consumption for a given quality of the
link. This bench also allows the determination of the non-linear distortion due to
the Device Under Test (DUT) when NPR is not well suited and provides
accurate analysis of the DUT behaviour by using its capabilities to generate
excitation signals that are similar to real ones.
The NPR bench is digital based (signal calculation and acquisition) which
ensures a high level of reproducibility, thermal noise reduction through signal
averaging and high degree of flexibility (generation of a very large type of
signals).
4 PERFORMANCES
4.1 SYSTEM PERFORMANCES
In order to improve BST measurements, the Bit Error Rate (BER) measurements are compared to a
reference configuration which takes into account potential degradation coming from the testbed itself.
Moreover, to improve measurements accuracy, the thermal noise is generated and controlled by a
proprietary process allowing to adjust carefully the C/No ratio.
The first validation step consists to measure the reference configuration in order to calibrate the proper
elements of the testbed. Then we are able to give relative BER degradation for specific BST set-up.
1,00E-02
1,00E-03
1,00E-04
1,00E-05
1,00E-06
1,00E-07
1,00E-08
1,00E-09
1,00E-10
Modulator/demodulator
IF frequency
Ka frequency
Ka frequency and TOP
3,2 3,3 3,4 3,5 3,6 3,7 3,8 3,9 4 4,1
Performances analysis
1,00E-02
1,00E-03
1,00E-04
1,00E-05
1,00E-06
1,00E-07
1,00E-08
1,00E-09
Reference
Mask 1
Mask 3
Mask 4
Mask 5
Mask 6
Mask 7
3,2 3,4 3,6 3,8 4 4,2 4,4
Phase Noise Analysis
As example, the figure above shows the results performed by the BST for multiple configurations and
phase noise analysis using Component On The Shelf (COTS) modulator and demodulator based on DVB-
DSNG standard.
5