AMCP - WG/F WP/38
GNSSP SPECTRUM SUBGROUP ACTION ITEM RESPONSES
SG1/7
Document the SARPS GBAS unwanted emission requirements, compare to
ITU regulations.
Prepared by T. Jacob
Introduction:
Within the GNSSP Spectrum Sub-group the question was raised whether the unwanted
emission limits defined in the current Draft ICAO GNSS SARPs for GBAS ground stations
comply with ITU regulations.
From the definitions given in the Radio Regulations (RR), it can be seen that unwanted
emissions consist of spurious and out-of-band emissions.
Appendix S3 to the Radio Regulations indicate the maximum permitted levels of spurious
emissions of any spurious component supplied by a transmitter to the antenna transmission
line.
It has to be considered that there are no general guidelines available in ITU Recommendations
covering unwanted emissions in the out-of-band domain from a transmission at the edge of
one allocation into the adjacent allocation.
Note: The ITU-R is currently developing material to consider issues related to unwanted
emissions. WRC-2003 will have to review under its Agenda Item 1.8.1 the results of studies
regarding the boundary between spurious and out-of-band emissions, with a view to modify
Appendix S3 of ITU Radio Regulations.
ITU provisions relevant to unwanted emission limits:
When reviewing unwanted emission limits the following ITU RR provisions have to be
recognised:
Unwanted emissions (RR Article S1.146)
Consist of spurious emissions and out-of-band emissions.
Spurious emission (RR Article S1.145)
Emission on a frequency or frequencies which are outside the necessary bandwidth and the
level of which may be reduced without affecting the corresponding transmission of
information. Spurious emissions include harmonic emissions, parasitic emissions,
intermodulation products and frequency conversion products, but exclude out-of-band
emissions.
Spurious domain emissions:
All emissions, including intermodulation products, conversion products and parasitic
emissions, which fall at frequencies separated from the centre frequency of the emission by
250% or more of the necessary bandwidth of the emission will generally be considered as
emissions in the spurious domain. However, this frequency separation may be dependent on
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the type of modulation, the maximum symbol rate in the case of digital modulation, the type
of transmitter, and frequency coordination factors. For example, in the case of some digital,
broadband, or pulse-modulated systems, the frequency separation may need to differ from the
250% factor.
Out-of-band emission (RR Article S1.144)
Emission on a frequency or frequencies immediately outside the necessary bandwidth which
results from the modulation process, but excluding spurious emissions.
Out-of-band domain emissions
Any emission outside the necessary bandwidth which occurs in the frequency range separated
from the assigned frequency of the emission by less than 250% of the necessary bandwidth of
the emission will generally be considered an emission in the out-of-band domain. However,
this frequency separation may be dependent on the type of modulation, the maximum symbol
rate in the case of digital modulation, the type of transmitter, and frequency coordination
factors. For example, in the case of some digital, broadband, or pulse modulated systems, the
frequency separation may need to differ from the 250% factor.
Occupied bandwidth (RR Article S1.153)
The width of the frequency band which is just sufficient such that, below the lower and above
the upper frequency limits, the mean powers emitted are each equal to a specified percentage
/2 of the total mean power of a given emission.
Unless otherwise specified in an ITU-R Recommendation for the appropriate class of
emission, the value of /2 should be taken as 0.5%.
Necessary bandwidth (RR Article S1.152)
For a given class of emission, the width of the frequency band which is just sufficient to
ensure the transmission of information at the rate and with the quality required under
specified conditions.
Assigned frequency band (RR Article S1.147)
The frequency band within which the emission of a station is authorized; the width of the
band equals the necessary bandwidth plus twice the absolute value of the frequency tolerance.
Where space stations are concerned, the assigned frequency band includes twice the
maximum Doppler shift that may occur in relation to any point of the Earth's surface.
Assigned frequency (RR Article S1.148)
The centre of the frequency band assigned to a station.
Figure 1 gives a generic example of evaluation of the unwanted emissions in the out-of-band
domain falling into the adjacent allocated band, where the boundary between the out-of-band
and spurious domains is 250% of the necessary bandwidth Bn.
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(1)
(2)
(3)
Actual out-of-band mask for the system under consideration
Spurious limit defined by Appendix S3 or Recommendation ITU-R SM.329
Unwanted emissions in the out-of-band domain falling in the adjacent allocated frequency
band
FIGURE 1
Maximum permitted spurious emission power levels:
The Appendix S3 to the RR indicate the maximum permitted levels of spurious emissions, in
terms of power as indicated in the tables below, of any spurious component supplied by a
transmitter to the antenna transmission line.
For the purpose of setting limits, all emissions, including harmonic emissions,
intermodulation products, frequency conversion products and parasitic emissions, which fall
at frequencies separated from the centre frequency of the emission by ± 250%, or more, of the
necessary bandwidth of the emission will generally be considered as spurious emissions.
Section I of Appendix S3 is applicable until 1 January 2012 to transmitters installed on or
before 1 January 2003; Section II is applicable to transmitters installed after 1 January 2003
and to all transmitters after 1 January 2012. This Appendix does not cover out-of-band
emissions (see Section below).
Section I – Spurious emission limits for transmitters installed on or before 1 January 2003
(valid until 1 January 2012)
Frequency band containing the assignment
(lower limit exclusive,
upper limit inclusive)
For any spurious component, the attenuation
(mean power within the necessary bandwidth
relative to the mean power of the spurious
component concerned) shall be at least that
specified below and the absolute mean power
levels given shall not be exceeded 1
30 MHz to 235 MHz
– mean power above 25 W
– mean power 25 W or less
60 dB
1 mW
40 dB
25 mW
Note: Only the GBAS related material has been quoted.
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Section II – Spurious emission limits for transmitters installed after 1 January 2003 and for all
transmitters after 1 January 2012
Attenuation values used to calculate maximum permitted spurious emission power levels for
use with radio equipment
Service category in
accordance with Article S1
Attenuation (dB) below the power
supplied to the antenna transmission line
All services except those services
quoted below
43 10 log (P), or 70 dBc, whichever is less stringent
Note: Only the GBAS related material has been quoted.
The spurious emission levels given in Appendix S3 are specified in the following reference
bandwidths:
– 1 kHz between 9 kHz and 150 kHz
– 10 kHz between 150 kHz and 30 MHz
– 100 kHz between 30 MHz and 1 GHz
– 1 MHz above 1 GHz.
Maximum permitted out-of-band emission power levels:
It was stated in the introduction that there are no general guidelines available in ITU
Recommendations covering unwanted emissions in the out-of-band domain from a
transmission at the edge of one allocation into the adjacent allocation. Therefore, ITU-R
Study Group 1 established Task Group 1/5 to study all unwanted emissions. The final Task
Group 1/5 meeting (Geneva, 23 – 30 October 2000) completed a number of draft new ITU-R
Recommendations. WRC-2003 will have to review under its Agenda Item 1.8.1 the results of
studies regarding the boundary between spurious and out-of-band emissions, with a view to
modify Appendix S3 of ITU Radio Regulations (RR).
In order to conduct the comparison between the GBAS SARPs and the ITU unwanted
emission levels the material of Draft New Recommendation ITU-R SM.[OOB] developed by
TG 1/5 [2] has been used. This Draft New Recommendation provides no limits for
aeronautical radio navigation services however, in its Annex 11 out-of-band limits for the
aeronautical mobile service are given.
For aeronautical-mobile and maritime-mobile transmitters other than aeronautical telemetry
and exempted systems, the required attenuation of the mean power of any emission in the outof-band domain, relative to the mean power of the transmitter, is:
50-150%
150-250%
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25 dBc
35 dBc
Page 4
Attenuation (dBc)
Aeronautical and Maritime Mobile
0
5
10
15
20
25
30
35
40
0
50
100
150
200
250
300
Frequency Separation (per cent of necessary
bandwidth)
FIGURE 2
Out-of-band mask for aeronautical and maritime mobile
GBAS SARPs unwanted emission requirements:
The current Draft ICAO GBAS SARPs define in Section A.3.5.4.6 the following maximal
allowable power limits for unwanted emissions produced by GBAS ground stations (see
Table below).
In order to be able to compare the maximum unwanted emission limits given in Appendix S3
to the RR and the limits defined in GBAS SARPs the power levels are provided in addition
with a 100 kHz reference bandwidth.
Frequency
Relative Unwanted
Emission Level [2]
Maximum Unwanted Emission
Level [1]
9kHz to 150 kHz
150 kHz to 30 MHz
30 MHz to 106.125
MHz
106.425 MHz
107.225 MHz
107.625 MHz
107.825 MHz
107.925 MHz
107.975 MHz
118.000 MHz
118.050 MHz
118.150 MHz
118.350 MHz
118.750 MHz
119.550 MHz
119.850 MHz to 1 GHz
1 GHz to 1.7 GHz
-93 dBc [3]
-103 dBc [3]
-115 dBc
-55 dBm/1 kHz [3]
-55 dBm/10 kHz [3]
-57 dBm/100 kHz
Maximum Unwanted
Emission Level with
100 kHz reference
bandwidth
-35 dBm
-45 dBm
-57 dBm
-113 dBc
-105 dBc
-101.5 dBc
-88.5 dBc
-74 dBc
-65 dBc
-65 dBc
-74 dBc
-88.5 dBc
-101.5 dBc
-105 dBc
-113 dBc
-115 dBc
-115 dBc
-55 dBm/100 kHz
-47 dBm/100 kHz
-53.5 dBm/10 kHz
-40.5 dBm/10 kHz
-36 dBm/1 kHz
-27 dBm/1 kHz
-27 dBm/ 1 kHz
-36 dBm/1 kHz
-40.5 dBm/10 kHz
-53.5 dBm/10 kHz
-47 dBm/100 kHz
-55 dBm/100 kHz
-57 dBm/100 kHz
-47 dBm/1 MHz
-55 dBm
-47 dBm
-43.5 dBm
-30.5 dBm
-16 dBm
-7 dBm
-7 dBm
-16 dBm
-30.5 dBm
-43.5 dBm
-47 dBm
-55 dBm
-57 dBm
-57 dBm
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Note 1.- The maximum unwanted emission level (absolute power) applies if the authorized transmitter power
exceeds 150 W.
Note 2. – The relative unwanted emission level is to be computed using the same bandwidth for desired and
unwanted signals. This may require conversion of the measurement for unwanted signals done using the
bandwidth indicated in the maximum unwanted emission level column of Table 2.
Note 3.- This value is driven by measurement limitations. Actual performance is expected to be better.
Note 4.- The relationship is linear between single adjacent points designated by the adjacent channels identified
above.
Comparison of the maximum permitted unwanted emission power limits:
According to Appendix S3 the spurious domain generally consists of frequencies separated
from the centre frequency of the emission by 250% of the necessary bandwidth of the
emission. In this analysis it has been assumed that 25 kHz is the appropriate value for the
necessary bandwidth of GBAS transmissions. The boundary between spurious and out-ofband emissions is set to 2.5 * 25 kHz = 62.5 kHz. The lowest assignable GBAS channel is
25 kHz from the band edge, the boundary is set at 107.9625 MHz.
Spurious Emissions Limits:
For any spurious component of a GBAS transmitter installed before 1 January 2003 (valid
until 1 January 2012) the attenuation (mean power within the necessary bandwidth relative to
the mean power of the spurious component concerned) shall be at least 60 dB below and the
absolute mean power levels given shall not exceed 1 mW. Assuming a mean power of a
GBAS transmitter of 150 W equals 21.76 dBW within 25 kHz reference bandwidth minus an
attenuation of 60 dB gives a maximum spurious emission power level of –38.24 dBW or
-8.24 dBm. In order to make the different power levels comparable a conversion of the
reference bandwidth from 25 kHz to 100 kHz is necessary. This leads to a bandwidth
conversion factor of 6 dB. And so, the maximum spurious emission power level is –2.24 dBm
within a 100 kHz reference bandwidth.
A GBAS transmitter installed after 1 January 2003 must meet a spurious domain emission
attenuation of 43 + 10 log (P), or 70 dBc, whichever is less stringent. To measure spurious
domain emissions in the frequency range between 30 MHz and 1000 MHz, Appendix S3
indicates use of a reference bandwidth of 100 kHz.
With a maximum total mean power of 150 W for GBAS ground stations the attenuation
relative to the total mean power equals 43 + 10 log (150) = 64.76 dB. The 64.76 dB is less
stringent than 70 dBc, so the 64.76 dB value is used. Therefore, spurious domain emissions of
GBAS transmitters must not exceed 64.76 dBc in a 100 kHz reference bandwidth, or
converting to an absolute power level, the spurious emission must not exceed 21.76 dBW –
64.76 dBc = -43 dBW or –13 dBm in a 100 kHz reference bandwidth.
Out-of-band Emission Limits:
For aeronautical-mobile transmitters the required attenuation of the mean power of any
emission in the out-of-band domain, relative to the mean power of the transmitter, is:
50-150%
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25 dBc
Page 6
150-250%
35 dBc
With a maximum total mean power of 150 W in a 25 kHz (and also 100 kHz) reference
bandwidth of a GBAS transmitter the out-of-band emissions must not exceed 21.76 dBW –
25 dBc = -3.24 dBW (26.76 dBm) in the frequency range separated from the assigned
frequency between 50 and 150% of the necessary bandwidth and -13.24 dBW (16.76 dBm)
for frequencies between 150 and 250% of the necessary bandwidth.
The table below provides the different emission limits with a 100 kHz reference bandwidth.
Frequency
(MHz)
107.8250
107.9250
107.9625
107.9750
107.9875
108.0000
GBAS SARPs
ITU RR Appendix S3
Unwanted Spurious emission levels
emission levels
for Tx installed before
(dBm/100 kHz)
1.1.2003
(dBm/100 kHz)
-30,5
-2,24
-16
-2,24
-2,24
-7
-7
ITU RR Appendix S3 ITU-R Doc 1/33 Rev.1
Spurious emission Out-of-band emission
levels for Tx installed
levels
after 1.1.2003
(dBm/100 kHz)
(dBm/100 kHz)
-13
-13
-13
16,76
16,76
26,76
Emission Levels
(dBm/100kHz)
35
25
107,9
625
15
107,9
875
5
-5
-15
-25
107,9
25
107,8
25
-35
107,800
107,850
107,900
107,950
107,9
75
108,0
00
108,000
108,050
Frequency (MHz)
GBAS SARPs Unwanted emission levels
ITU RR Appendix S3 Spurious emission levels for Tx installed before 1.1.2003
ITU RR Appendix S3 Spurious emission levels for Tx installed after 1.1.2003
ITU-R Doc 1/33 Rev.1 Out-of-band emission levels
FIGURE 3
It is important to note that the spurious and out-of-band emission limits have to be derived
from a mean power values of the transmitters. The GBAS SARPs defining a maximum
transmit power of 150 W. For this analysis it was assumed that the 150 W is a mean power
value. The results of the analysis may differ if the GBAS transmit power is given as peak
envelop power (PEP) value.
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Conclusion:
1. GBAS SARPs requirements for maximum permitted unwanted emission power levels
comply with the ITU requirements for transmitters installed before 1 January 2003.
2. In small portion of the frequency range between 107.925 MHz and 107.9625 MHz GBAS
SARPs allow a slightly higher unwanted emission power level as required by ITU RR for
transmitters installed after 1 January 2003. However, it has to be noted that for this
analysis the worst case GBAS transmit power of 150 W as a mean power value was used.
Further clarification needed whether the GBAS maximum transmit power given in the
SARPs material has to be interpreted as a peak envelop power or a mean power value.
Bibliography:
[1]
[2]
[3]
[4]
[5]
ITU-R SG1 Document 1/27(Rev.1)-E - DNR ITU-R SM.[OAB] Unwanted emissions
in the out-of-band domain falling into adjacent bands
ITU-R SG1 Document 1/33(Rev.1)-E - DNR ITU-R SM.[OOB] Unwanted emissions
in the out-of-band domain
ITU RR Appendix S3
ITU-R Recommendation SM.329-8 – Spurious Emissions
ICAO Draft GNSS SARPs and Guidance Material
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