Protection levels (pycraf.protection)#
Introduction#
The protection sub-package is a small convenience module, which
contains protection levels (the bare numbers) for various scenarios.
At the moment, the radio-astronomy service (RAS) protection thresholds
as given in ITU-R Rec. RA.769 (Table 1 and 2),
as well as industry-level device emission limits according to
CISPR-11 (EN 55011) and
CISPR-22 (EN 55022)
are provided.
Using pycraf.protection#
RA.769#
The function ra769_limits returns a
QTable object that resembles (Table 1 to 3) from
ITU-R Rec. RA.769:
>>> from pycraf import protection
>>> import astropy.units as u
>>> protection.ra769_limits(mode='continuum')
<QTable length=21>
frequency bandwidth T_A ... Slim_nu Efield Efield_norm
MHz MHz K ... dB(W / (Hz m2)) dB(uV2 / m2) dB(uV2 / m2)
float64 float64 float64 ... float64 float64 float64
--------- --------- ------- ... --------------- ------------ ------------
13 0 50000 ... -247.6 -54.9 -41.9
26 0 15000 ... -249.1 -52.5 -43.3
74 2 750 ... -258.2 -50.4 -52.5
152 3 150 ... -259.2 -48.7 -53.4
325 7 40 ... -257.5 -43.5 -51.7
408 4 25 ... -255.1 -43.4 -49.3
... ... ... ... ... ... ...
31550 500 18 ... -228.0 4.8 -22.2
43000 1000 25 ... -226.4 9.3 -20.7
89000 8000 12 ... -227.9 16.8 -22.2
150000 8000 14 ... -223.2 21.6 -17.4
224000 8000 20 ... -218.2 26.6 -12.4
270000 8000 25 ... -215.8 29.0 -10.0
For VLBI the returned table object looks a bit different:
>>> protection.ra769_limits(mode='vlbi')
<QTable length=21>
frequency T_A T_rx Slim_nu
MHz K K dB(W / (Hz m2))
float64 float64 float64 float64
--------- ------- ------- ---------------
13 50000 60 -217.6
26 15000 60 -217.2
74 750 60 -220.7
152 150 60 -220.3
325 40 60 -216.9
408 25 60 -215.6
... ... ... ...
31550 18 65 -178.0
43000 25 65 -174.9
89000 12 30 -171.9
150000 14 30 -167.2
224000 20 43 -162.1
270000 25 50 -159.8
This is because the VLBI thresholds are not based on the RMS (after a certain integration time and with a certain bandwidth), but on the system temperature (typical receiver noise values and antenna temperatures). The thresholds are defined as 1% of Tsys.
For continuum and spectral modes, it is possible to use a different integration time:
>>> plim_2000s = protection.ra769_limits(mode='continuum')[7]['Plim']
>>> for itime in [15 * u.min, 1 * u.h, 2 * u.h, 5 * u.h, 10 * u.h]:
... tab = protection.ra769_limits(mode='continuum', integ_time=itime)
... # print values of footnote (1) of tables 1 and 2 in RA.769
... print('{:.1f}'.format(tab[7]['Plim'] - plim_2000s))
1.7 dB
-1.3 dB
-2.8 dB
-4.8 dB
-6.3 dB
CISPR limits#
The two functions cispr11_limits and
cispr22_limits have a different call signature (see
API reference), but are similarly easy to use:
>>> protection.cispr11_limits(
... 500 * u.MHz, detector_type='QP', detector_dist=100 * u.m
... )
(<Decibel [ 26.54242509] dB(uV2 / m2)>, <Quantity 120.0 kHz>)
These return a tuple with the electrical field limit and the detector bandwidth (currently always 120 kHz) for a frequency and distance. Two detector types are available: Quasi-Peak (QP) and RMS.
See Also#
Astropy Units and Quantities package, which is used extensively in pycraf.
Reference/API#
pycraf.protection Package#
This sub-package contains various protection criteria and interference limits, e.g. for the radio-astronomy service (RAS).
Functions#
|
Industrial-device limits for given frequency and distance from device according to CISPR-11 (EN 55011). |
|
Industrial-device limits for given frequency and distance from device according to CISPR-22 (EN 55022). |
|
Limits (single entry) for spectral line, continuum, and VLBI observations according to ITU-R Rec RA.769. |
|
Limits for spectral line, continuum, and VLBI observations according to ITU-R Rec RA.769. |