FPGA Controlled High Performance Amplifier
May06--14
Circuit Noise Density Test
Overview:
The Circuit Noise Density Test, performed on the FPGA Controlled Amplifier Board, is
a LabVIEW automated test that uses an HP 33120A Function Generator, an HP 8662A
Function Generator, an HP 3585A Spectrum Analyzer (for 0-40MHz range), and a HP
8563E Spectrum Analyzer (for 40MHz – 100MHz range).
Prior to the test, the team should have extra caution about input dc voltage signal
because the spectrum analyzer is very sensitive about it. In addition, since HP3585A
Spectrum Analyzer has limited range of 40MHz, the HP 8563E Spectrum Analyzer
will be used for the 40MHz to 100MHz range.
To use LabVIEW in Durham 344, the team should download the appropriate equipment
drivers. Then, a LabVIEW program will be developed to vary the input frequencies and
gather data from the spectrum analyzer. The LabVIEW project will be submitted upon
completion. The computer will control the spectrum analyzer over the GPIB bus to
output a signal to the PCB.
After the spectrum analyzer delivers the certain resolution bandwidth, the data should
be analyzed to ensure the noise density, which is dividing the noise voltage by the root
of the bandwidth measured by the spectrum analyzer. Major caution in the test is to
measure RMS noise voltage instead of peak or average noise voltage.
Equipments:
HP 3585A Spectrum Analyzer (for 0-40MHz range)
Specs: http://cp.literature.agilent.com/litweb/pdf/03585-90006V1.pdf
(page 1-5)
HP 8563E Spectrum Analyzer (For 40MHz-100MHz, but this
one will burn up with more than 200mV DC. Must be very careful.)
Specs: http://www.valuetronics.com/vt/assets/pdfs/hp_8560eseries.PDF
HP 33120A Function Generator (for 10mHz - 10MHz)
Specs: http://cp.literature.agilent.com/litweb/pdf/5968-0125EN.pdf
HP 8662A Function Generator (for 10MHz - 100MHz)
Specs: http://www.valuetronics.com/vt/assets/pdfs/HP_8662A.PDF
Terms & Definitions:
FPGA -- Field programmable gate arrays, a gate array where the logic network can be
programmed into the device after its manufacture. An FPGA consists of an array of
FPGA Controlled High Performance Amplifier
May06--14
logic elements, either gates or lookup table RAMs, flip-flops and programmable
interconnect wiring.
Noise -- Undesired interference in signals.
Spectrum analyzer -- A tool that analyzes signals in the frequency domain.
GPIB -- General Purpose Interface Board. Same as IEEE 488
IEEE 488 -- A communication bus, standard in the test industry.
TEK -- Tektronix
Explanation of tests:
The input signal will be generated by the function generators, which are connected to
the input of the FPGA Controlled Amplifier Board. There are 8 different frequency
ranges, and the team will use middle points of the frequency ranges (table ). Then, the
team will get noise figure and the bandwidth data from the spectrum analyzers. Overall,
noise density will be calculated by below equation.
VRMS
BandWidth
 noise _ density
The test result should fulfill the specifications in below table.
With a Spectrum Analyzer, the team can measure one-sided spectral density of phase
fluctuation per unit bandwidth.
a. Spectrum Analyzer has capability to measure RMS voltage in a known
bandwidth.
b. Get relative power in dBc between the carrier and the sideband noise at 1- kHz
offset
c. The spectrum analyzer will display the power for a certain resolution bandwidth
(RBW).
d. Then, the output spectral noise density will be obtained by dividing the measured
output noise by the root of the measurement bandwidth.
e. Use the marker noise functions to check the accurate display.
f. Ensure that true RMS noise is being measured, not peak or average.
FPGA Controlled High Performance Amplifier
May06--14
Test Specifications:
Table 1 noise density specifications
Input
Frequency
Range
DC – 1kHz
> 1kHz - 20 kHz
> 20kHz –
100kHz
> 100kHz - 1MHz
> 1MHz - 10MHz
> 10MHz –
20MHz
> 20MHz –
50MHz
> 50MHz –
100MHz
Noise
(nV/rtHz)
1.5 nV/rtHz
1.5 nV/rtHz
2.5 nV/rtHz
3.5 nV/rtHz
3.5 nV/rtHz
3.5 nV/rtHz
5.0 nV/rtHz
5.0 nV/rtHz