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Source: Document 1-9/TEMP/32 **JRG-28**

Task Group 1/9

liaison statement to working party 8b and\
for information to JRG 1a-1c-8b

Compatibility analysis between the Earth exploration‑satellite (passive)
service systems\
\[operating\] in the 1 400-1 427 MHz band and radiolocation service
systems operating in the 1 350‑1 400 MHz band

At its meeting in February 2005, Task Group 1/9 received a contribution
on a method to revise Annex 3 of Recommendation ITU-R SM.1633, which
discusses the compatibility between the EESS (passive) systems operating
in the 1 400-1 427 MHz band and radiolocation systems operating in the 1
350-1 400 MHz band. Annex 3 of Recommendation ITU-R SM.1633 made use of
Recommendation ITU-R SM.1541, thereby only utilizing an envelope (peak
emission) mask that when integrated over the EESS (passive) bandwidth
could result in a large overestimation of the unwanted emission power
falling into the passive band.

The contribution proposes the use of spectral representations based on
Fourier analysis in order to give a more accurate estimation of the
unwanted emission power falling into the passive band. Comparisons
between the two methods (based on Recommendation ITU-R SM.1541 and one
based on Fourier analysis) are given.

The developed method compares well to results given in
Document JRG‑1A‑1C-8B/12 ("Comparison of methods used to predict the
bandwidth of radar emissions") by using the same parameters. A pulse
rise time of 50 ns has been used in most analyses (as contained in Annex
3 of Recommendation ITU-R SM.1633 -- resulting from a liaison statement
from WP 8B directed to TG 1/7). Linear FM chirp is being used to
characterize the signal modulation. Radar characteristics have been
extracted from Recommendation ITU-R M.1463. The study resulted in a more
favourable compatibility situation for the method relying on Fourier
analysis ("spectrum method"), but still discrepancies existed between
the power received by the EESS (passive) sensor and the interference
threshold whilst assuming a radar antenna gain of 0 dBi.

Also, the amount of frequency separation between the passive band and
the radar channel's centre frequency was investigated for two radar
systems with respect to a specific EESS (passive) sensor to show the
potential for this method for unwanted emission power calculation for
radar systems.

Although the resulting radar spectra are for theoretical pulses, this
method does resemble the real radar emission characteristics more than a
mask would do. No allowance has been made for distortions that may occur
in a practical situation, but also no filtering characteristics (or
inherit spectral attenuation of the radar hardware such as use of wave
guides) of the radars have been investigated that would result in a more
favourable situation.

Where this contribution discusses the static analyses, it is envisaged
that a future revision of this document for the next meeting of Task
Group 1/9 would also include statistical/dynamic analyses. This
preliminary study only takes into account the interference threshold
from Recommendation ITU-R SA.1029, but also the availability criterion
(defined in Recommendation ITU-R SA.1029 as the percentage of area the
permissible interference level may be exceeded) needs to be taken into
account. By also taking this availability criterion into account (for
the statistical/dynamical analyses), depending on the density of radars
and probability of channel occupation near the passive band, within the
measurement area, the apparent incompatibility may be alleviated to a
great extent.

In order to refine these calculations, Task Group 1/9 would like to
request information on a realistic density model for these radar systems
(for Systems 1-4) as well as on any additional information to be used
for the refinement such as probability of channel occupation near the
passive band and filtering characteristics.

**Attachment:** Document 1-9/TEMP/39

**Contact:** Björn ROMMEN (ESA)\
E-mail: <Bjorn.Rommen@esa.int>

Attachment

Source: Document 1-9/TEMP/39

working document on the methodology to revise ANNEX 3 to Recommendation
itu-r SM.1633:

Compatibility analysis between the Earth exploration‑satellite (passive)
service systems operating in the 1 400-1 427 MHz band and radiolocation
service systems operating in the 1 350‑1 400 MHz band

# 1 Introduction

Annex 3 of Recommendation ITU-R SM.1633 discusses the compatibility
between the EESS (passive) systems operating in the 1 400--1 427 MHz
band and radiolocation systems operating in the 1 350--1 400 MHz band.
Available information at that time only permitted the use of
Recommendation ITU-R SM.1541, thereby only utilising an envelope mask
that when integrated over the EESS (passive) bandwidth could result in a
large overestimation of the unwanted emission power falling into the
passive band.

This contribution proposes the use of spectral representations based on
Fourier analysis in order to give a more accurate estimation of the
unwanted emission power falling into the passive band. Comparisons
between the 2 methods (based on Rec. ITU-R SM.1541 and one based on
Fourier analysis) will be given.

# 2 Simulated radar spectra

In order to arrive to accurate spectral representations of modulated and
unmodulated radar signals, first the shape of the pulse needs to be
taken into account. Here, trapezoidal pulses will be used where pulse
rise- and fall-times are similar thus resulting in a symmetrical pulse
shape for unmodulated pulses. The developed method compares well to
results given in\
Document JRG-1A-1C-8B/12 ("Comparison of methods used to predict the
bandwidth of radar emissions") by using the same parameters. A pulse
rise time of 50 ns has been used in most analyses (as contained in Annex
3 of Rec. ITU-R SM.1633 - resulting from a liaison statement from WP 8B
directed to TG 1/7). Linear FM chirp is being used to characterize the
signal modulation.

Radar characteristics have been extracted from Recommendation ITU-R
M.1463 and are here repeated in Table 1.

TABLE 1

1 215-1 400 MHz radiodetermination system characteristics

+----------------+------------+------------+------------+------------+
| **Parameter**  | **System   | **System   | **System   | **System   |
|                | 1**        | 2**        | 3**        | 4**        |
+----------------+------------+------------+------------+------------+
| Peak power     | 97         | 80         | 76.5       | 80         |
| into\          |            |            |            |            |
| antenna (dBm)  |            |            |            |            |
+----------------+------------+------------+------------+------------+
| Pulse duration | 2          | 88.8;\     | 0.4;       | 39 single  |
| (μs)           |            | 58.8\      | 102.4;\    | frequency\ |
|                |            | (Note 1)   | 409.6\     | 26 and 13  |
|                |            |            | (Note 2)   | dual       |
|                |            |            |            | fre­quency  |
|                |            |            |            | (Note 3)   |
+----------------+------------+------------+------------+------------+
| Pulse          | 310-380\   | 291.5 or   | 200-272    | 774        |
| repetition     | staggered  | 312.5\     | long range | average    |
| rate (pps)     |            | average    |            |            |
|                |            |            | 400-554    |            |
|                |            |            | short      |            |
|                |            |            | range      |            |
+----------------+------------+------------+------------+------------+
| Chirp          | Not        | 770 kHz    | 2.5 MHz    | Not        |
| Bandwidth for  | applicable | for both   | for\       | applicable |
| frequency      |            | pulse      | 102.4 μs   |            |
| modulated      |            | widths     |            |            |
| (chirped)      |            |            | 625 kHz    |            |
| pulses         |            |            | pour 409.6 |            |
|                |            |            | μs         |            |
+----------------+------------+------------+------------+------------+
| Phase-coded    | Not        |            |            | 1          |
| sub-pulse\     | applicable |            |            |            |
| width (μs)     |            |            |            |            |
+----------------+------------+------------+------------+------------+
| Compression    | Not        | 68.3:1 and | 256:1 for  |            |
| ratio          | applicable | 45.2:1     | both       |            |
|                |            |            | pulses     |            |
+----------------+------------+------------+------------+------------+
| RF emission    | 0.5        | 1.09       | 2.2;\      | 1          |
| bandwidth      |            |            | 2.3;\      |            |
| (3 dB) (MHz)   |            |            | 0.58;      |            |
+----------------+------------+------------+------------+------------+
| Output device  | Klystron   | Transistor |            | Cross      |
|                |            |            |            | field      |
|                |            |            |            | amplifier  |
+----------------+------------+------------+------------+------------+
| Antenna type   | Horn-fed   | Stack beam | Rotating   | Parabolic  |
|                | reflector  | reflector  | phased     | cylinder   |
|                |            |            | array      |            |
+----------------+------------+------------+------------+------------+
| Antenna        | H          | Vertical,  | Horizontal | Vertical   |
| polarization   | orizontal, | circular   |            |            |
|                | vertical,\ |            |            |            |
|                | LHCP, RHCP |            |            |            |
+----------------+------------+------------+------------+------------+
| Antenna        | 34.5,      | 32.4-34.2, | 38.9,      | 32.5       |
| maximum\       | transmit   | transmit   | transmit   |            |
| gain (dBi)     |            |            |            |            |
|                | 33.5,      | 31.7-38.9, | 38.2,      |            |
|                | receive    | receive    | receive    |            |
+----------------+------------+------------+------------+------------+
| Antenna        | 3.6 shaped | 3.63-5.61, | 1.3        | 4.5 shaped |
| elevation      | to 44      | transmit   |            | to 40      |
| beamwidth      |            |            |            |            |
| (degrees)      |            | 2.02-8.79, |            |            |
|                |            | receive    |            |            |
+----------------+------------+------------+------------+------------+
| Antenna        | 1.2        | 1.4        | 3.2        | 3.0        |
| azimuthal      |            |            |            |            |
| beamwidth      |            |            |            |            |
| (degrees)      |            |            |            |            |
+----------------+------------+------------+------------+------------+
| Antenna        | 360°       |            | 360°       | 360°       |
| horizontal     | mechanical |            | mechanical | mechanical |
| scan           | at 5 rpm   |            | at\        | at\        |
| c              |            |            | 6 rpm for  | 6, 12 or   |
| haracteristics |            |            | long range | 15 rpm     |
| (rpm)          |            |            | and 12 rpm |            |
|                |            |            | for short  |            |
|                |            |            | range      |            |
+----------------+------------+------------+------------+------------+
| Antenna        | Not        | --7° to    | --1° to    | Not        |
| vertical scan  | applicable | +30°\      | +19°^\     | applicable |
| c              |            | in 12.8 or | ^in 73,5   |            |
| haracteristics |            | 13.7 ms    | ms         |            |
+----------------+------------+------------+------------+------------+
| Receiver IF    | 780 kHz    | 0.69 MHz   | 4.4 to 6.4 | 1.2 MHz    |
| bandwidth      |            |            | MHz        |            |
+----------------+------------+------------+------------+------------+
| Receiver noise | 2          |            | 4.7        | 3.5        |
| figure (dB)    |            |            |            |            |
+----------------+------------+------------+------------+------------+
| Platform type  | Fixed      |            | Tra        |            |
|                |            |            | nsportable |            |
+----------------+------------+------------+------------+------------+
| Percentage of  | 100        |            |            |            |
| time\          |            |            |            |            |
| system         |            |            |            |            |
| operates (%)   |            |            |            |            |
+----------------+------------+------------+------------+------------+
| NOTE 1 -- The  |            |            |            |            |
| radar has 44   |            |            |            |            |
| RF channel     |            |            |            |            |
| pairs with one |            |            |            |            |
| of 44 RF       |            |            |            |            |
| channel pairs  |            |            |            |            |
| selected in    |            |            |            |            |
| normal mode.   |            |            |            |            |
| The            |            |            |            |            |
| transmitted    |            |            |            |            |
| waveform       |            |            |            |            |
| consists of a  |            |            |            |            |
| 88.8 μs pulse  |            |            |            |            |
| at frequency   |            |            |            |            |
| *f*1 followed  |            |            |            |            |
| by a 58.8 μs   |            |            |            |            |
| pulse at       |            |            |            |            |
| frequency      |            |            |            |            |
| *f*2.          |            |            |            |            |
| Separation of  |            |            |            |            |
| *f*1 and *f*2  |            |            |            |            |
| is 82.854 MHz. |            |            |            |            |
|                |            |            |            |            |
| NOTE 2 -- The  |            |            |            |            |
| radar has 20   |            |            |            |            |
| RF channels in |            |            |            |            |
| 8.96 MHz       |            |            |            |            |
| increments.    |            |            |            |            |
| The            |            |            |            |            |
| transmitted    |            |            |            |            |
| waveform group |            |            |            |            |
| consists of    |            |            |            |            |
| one 0.4 μs P0  |            |            |            |            |
| pulse          |            |            |            |            |
| (optional)     |            |            |            |            |
| which is       |            |            |            |            |
| followed by    |            |            |            |            |
| one 102.4 μs   |            |            |            |            |
| linear         |            |            |            |            |
| frequency      |            |            |            |            |
| modulated      |            |            |            |            |
| pulse (if 0.4  |            |            |            |            |
| μs P0 is not   |            |            |            |            |
| transmitted)   |            |            |            |            |
| of 2.5 MHz     |            |            |            |            |
| chirp which    |            |            |            |            |
| may be         |            |            |            |            |
| followed by    |            |            |            |            |
| one to four    |            |            |            |            |
| long range     |            |            |            |            |
| 409.6 μs       |            |            |            |            |
| linear         |            |            |            |            |
| frequency      |            |            |            |            |
| modulated      |            |            |            |            |
| pulses each    |            |            |            |            |
| chirped 625    |            |            |            |            |
| kHz and        |            |            |            |            |
| transmitted on |            |            |            |            |
| different      |            |            |            |            |
| carriers       |            |            |            |            |
| separated by   |            |            |            |            |
| 3.75 MHz.      |            |            |            |            |
| Normal mode of |            |            |            |            |
| operation      |            |            |            |            |
| employs        |            |            |            |            |
| frequency      |            |            |            |            |
| agility        |            |            |            |            |
| whereby the    |            |            |            |            |
| individual     |            |            |            |            |
| frequencies of |            |            |            |            |
| each waveform  |            |            |            |            |
| group are      |            |            |            |            |
| selected in a  |            |            |            |            |
| pseudo-random  |            |            |            |            |
| manner from    |            |            |            |            |
| one of the     |            |            |            |            |
| possible 20 RF |            |            |            |            |
| channels       |            |            |            |            |
| within the     |            |            |            |            |
| 1 215-1 400    |            |            |            |            |
| MHz band.      |            |            |            |            |
|                |            |            |            |            |
| NOTE 3 -- The  |            |            |            |            |
| radar has the  |            |            |            |            |
| capability of  |            |            |            |            |
| operating      |            |            |            |            |
| single         |            |            |            |            |
| frequency or   |            |            |            |            |
| dual           |            |            |            |            |
| frequency.     |            |            |            |            |
| Dual RF        |            |            |            |            |
| channels are   |            |            |            |            |
| separated by   |            |            |            |            |
| 60 MHz. The    |            |            |            |            |
| single channel |            |            |            |            |
| mode uses the  |            |            |            |            |
| 39 μs pulse    |            |            |            |            |
| width. In the  |            |            |            |            |
| dual channel   |            |            |            |            |
| mode, the 26   |            |            |            |            |
| μs pulse is    |            |            |            |            |
| transmitted at |            |            |            |            |
| frequency *f*, |            |            |            |            |
| followed by    |            |            |            |            |
| the 13 μs      |            |            |            |            |
| pulse          |            |            |            |            |
| transmitted at |            |            |            |            |
| *f* + 60 MHz.  |            |            |            |            |
+----------------+------------+------------+------------+------------+

The radar spectra can then be compared to the OoB mask for primary
radars as contained in Figure 25 of Annex 8 to Recommendation ITU-R
SM.1541 (page 48). Since the mask is expressed in a frequency separation
as a percentage of the --40 dB bandwidth (B~-40~), B~-40~ is obviously
dependent on the radar parameters and needs to be calculated according
to formulas in Annex 8 (Rec. ITU-R SM.1541).

Calculations have been performed for System 1 and System 2, where one is
a representative system with no pulse modulation and the other is a
representative system with pulse modulation (i.e. linear FM chirp).

For System 1 a reference is shown in Figure 1, where between 50 -- 500 %
of B~-40~ (the other 50 % of B~-40~ is located on the negative frequency
axis which is not shown here) the mask and the maximum values of the
radar spectrum agree when no pulse rise- and fall-times are assumed
(i.e. perfectly rectangular pulse).

FIGURE 1

**Reference figure for a perfectly rectangular radar pulse with 2 μs
pulse length** ![](media/image2.jpeg){width="6.275in"
height="4.70625in"}

Figure 1 clearly shows the roll-off of 20 dB per decade and maximum
values of the radar spectrum match the mask between 50 to 500 % of
B~-40~ .

Since a perfectly rectangular pulse does not exist in practice, pulse
rise- and fall-times for radar systems need to be used in order to
characterize the radar spectrum. The shorter the pulse rise- and
fall-times, the wider spectra will occur in the radar spectrum and thus
resulting in a slower roll-off of the radar spectrum.

FIGURE 2

System 1 (2 μs pulse length) including pulse rise- and fall-time of 50
ns

![](media/image3.jpeg){width="6.275in" height="4.70625in"}

Figures 2 and 3 show this for System 1 with pulse rise times of 50 ns
and 100 ns, respectively. The masks at 50 % of the --40 dB bandwidth
(B~-40~) agree well with the radar spectra, but both spectra roll off
with 40 dB per decade from 50 % of B~-40~. At 500 % of B~-40~, the
difference between the mask and the simulated spectra is around 20 dB.

Table 2 reflects the necessary and --40 dB bandwidths for System 1
(according to Rec. ITU-R SM.1541) for the investigated pulse rise times.

TABLE 2

Necessary and --40 dB bandwidths for System 1 for different pulse rise
times

  ----------------- ----------------- ----------------- -----------------
  **SYSTEM 1**      **t~r~=t~f~=0     **t~r~=t~f~ =50ns **t~r~=t~f~
                    (Fig. 1)**        (Fig. 2)**        =100ns (Fig. 3)**

  **B~n~**          3.18 MHz          3.18 MHz          3.18 MHz

  **B~-40~**        32.0 MHz          19.6 MHz          13.9 MHz
  ----------------- ----------------- ----------------- -----------------

FIGURE 3

System 1 (2 μs pulse length) including pulse rise- and fall-time of 100
ns

![](media/image4.jpeg){width="6.275in" height="4.70625in"}

Also for System 2 emission spectra have been generated. These are shown
in Figures 4 and 5. As System 2 is a linear frequency modulated
(chirped) radar system, the simulation takes this into account. Figure 4
shows the radar spectrum for a 58.8 μs pulse length, whereas Figure 5
shows the radar spectrum for a 88.8 μs pulse length. The chirp bandwidth
is 770 kHz for both pulse lengths.

For both figures the mask largely overestimates the simulated spectra
and at 50 % of the --40 dB bandwidth, maximum values of the radar
spectra do not correspond to the same point as the mask (as was the case
with the unmodulated radar signal spectra).

Table 3 reflects the necessary and --40 dB bandwidths for System 2
(according to Rec. ITU-R SM.1541) for the investigated pulse lengths.

TABLE 3

Necessary and --40 dB bandwidths for System 2

  ----------------------- ----------------------- -----------------------
  **SYSTEM 2**            **B~n~**                **B~-40~**

  **58.8 μs / 50 ns**     2.58 MHz                9.36 MHz

  **88.8 μs / 50 ns**     2.39 MHz                8.68 MHz
  ----------------------- ----------------------- -----------------------

FIGURE 4

System 2 (58.8 μs pulse length) / pulse rise- and fall-time of 50 ns

![](media/image5.jpeg){width="5.65in" height="4.2375in"}

FIGURE 5

System 2 (88.8 μs pulse length) / pulse rise- and fall-time of 50 ns

![](media/image6.jpeg){width="5.65in" height="4.2375in"}

# 3 Radar unwanted emission power into passive band

From the developed masks and spectra, the radar signal attenuation is
known compared to the in-band situation. Since also the peak power into
the antenna is given, estimations can be made on the amount of power
falling into the passive band 1400 -- 1427 MHz in order to arrive to the
unwanted emission power at the radar antenna port. This should form the
basis for the compatibility analysis.

As in Annex 3 of Rec. ITU-R SM.1633, the initial assumption that the
start of the passive band (i.e. 1 400 MHz) is located at the offset
frequency corresponding to the mask's --40 dB attenuation point, which
is 50 percent of B~-40~, is used here as well.

For the 2 different methods, i.e. the envelope mask from Rec. ITU-R
SM.1541 and the 'spectrum' method, averaged attenuation levels relative
to the maximum value of the peak power and the total unwanted emission
power in the passive band 1 400--1 427 MHz from radar system 1 and 2
have been calculated. Results are shown in Table 4 and Table 5 for
System 1 and System 2, respectively. System 1 has been differentiated
for different pulse rise times (0, 50 and 100 ns), whereas System 2 has
been simulated for the 2 different pulse lengths (58.8 and 88.8 μs).

TABLE 4

Unwanted emission power levels into passive band for the 2 different
methods

+----------+---------+------------------+----------+------------------+
| **SYSTEM | *       | **Power in       | **Atten  | **Power in       |
| 1**      | *Attenu | passive band**   | uation** | passive band**   |
|          | ation** |                  |          |                  |
|          |         | ***SM.1541***    | ***Spe   | ***Spectrum***   |
|          | ***SM.  |                  | ctrum*** |                  |
|          | 1541*** |                  |          |                  |
+----------+---------+------------------+----------+------------------+
| **t~r~=  | -44.4   | 39.9 dBW         | -46.9    | 37.1 dBW         |
| t~f~=0** | dBpp    |                  | dBpp     |                  |
+----------+---------+------------------+----------+------------------+
| **t~r~   | -45.8   | 38.5 dBW         | -52.8    | 31.3 dBW         |
| =t~f~=50 | dBpp    |                  | dBpp     |                  |
| ns**     |         |                  |          |                  |
+----------+---------+------------------+----------+------------------+
| **t~r~=  | -47.0   | 37.3 dBW         | -57.0    | 27.1 dBW         |
| t~f~=100 | dBpp    |                  | dBpp     |                  |
| ns**     |         |                  |          |                  |
+----------+---------+------------------+----------+------------------+

TABLE 5

Unwanted emission power levels into passive band for the 2 different
methods

+----------+---------+------------------+----------+------------------+
| **SYSTEM | *       | **Power in       | **Atten  | **Power in       |
| 2**      | *Attenu | passive band**   | uation** | passive band**   |
|          | ation** |                  |          |                  |
|          |         | ***SM.1541***    | ***Spe   | ***Spectrum***   |
|          | ***SM.  |                  | ctrum*** |                  |
|          | 1541*** |                  |          |                  |
+----------+---------+------------------+----------+------------------+
| **58.8   | -48.4   | 15.6 dBW (36.0   | -58.0    | 8.8 dBW (7.6 W)  |
| μs**     | dBpp    | W)               | dBpp     |                  |
+----------+---------+------------------+----------+------------------+
| **88.8   | -48.7   | 15.3 dBW (33.7   | -59.1    | 7.7 dBW (5.9 W)  |
| μs**     | dBpp    | W)               | dBpp     |                  |
+----------+---------+------------------+----------+------------------+

For System 1, the 2 methods differ in a range from around 3 dB (t~r~=0)
to over 10 dB (t~r~=100 ns) for a situation where the passive band
starts at 50 percent of B~-40~. For System 2, differences in power level
are around 7 dB. For a larger offset from the radar centre frequency the
differences in power levels will drastically grow (as has been shown in
the figures). This will be further detailed in the next section.

# 4 Compatibility analyses

In this section, the calculated power levels in the passive band will be
used in compatibility analyses in order to demonstrate the method. Here,
only the static case will be investigated. The characteristics for the
EESS (passive) for the band 1 400--1 427 MHz are detailed in Annex 3 of
Recommendation ITU-R SM.1633 on page 31. The analyses will involve two
different instruments, i.e. SMOS and HYDROS, where the main differences
(related to this study) are the antenna gain (9 dBi for SMOS; 35 dBi for
HYDROS), altitude and pointing direction, where the latter 2 combined
result in a different free space loss. Sample calculations will be made
with a radar antenna gain of 0 dBi.

TABLE 6

Compatibility analysis with radar (radar antenna gain=0 dBi)

  ------------------------------------ ---------- ------- ---------- ------- ---------- -------
                                       **System 1         **System 2         **System 2 
                                       / 50 ns**          / 58.8             / 88.8     
                                                          μs**               μs**       

  Power in passive band (dBW)          31.3               8.8                7.7        

  Duty cycle allowance (dB)            -31.2              -17.7              -15.9      

  Free space loss SMOS/HYDROS (dB)     152.9      154.4   152.9      154.4   152.9      154.4

  Sensor ant gain SMOS/HYDROS (dBi)    9          35      9          35      9          35

  Interference threshold (dBW)         -174               -174               -174       

  Discrepancy (dB)                     30.2       54.7    21.2       45.7    21.9       46.4
  ------------------------------------ ---------- ------- ---------- ------- ---------- -------

As can be seen in Table 6, power levels in the passive band reach levels
that are largely above the interference criterion of --174 dBW with
discrepancy values ranging from 21.2 to 54.7 dB. Obviously, the main
reason for this apparent incompatibility is the very high peak power of
the radar systems as well as the very close proximity of the radar
channel's centre frequency to the passive band. Using the same peak
power levels, the separation between the highest radar channel's centre
frequency and the passive band can be investigated using the developed
method.

FIGURE 6

Radar offset frequency w.r.t. unwanted emission power falling into
passive band for System 1

![](media/image7.jpeg){width="5.766666666666667in" height="4.3125in"}

FIGURE 7

Radar offset frequency w.r.t. unwanted emission power falling into
passive band for System 2

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For System 1 the analysis (see Figure 6) resulted in a compatible
situation when a 72.5 MHz separation would exist between the radar
centre frequency and the (start of the) passive band. For System 2 (the
analysis for a 58.8 μs pulse length resulted in a nearly similar
result), as shown in Figure 7, the analysis resulted in a compatible
situation when a 17.5 MHz separation would exist between the radar
centre frequency and the (start of the) passive band. Both results only
reflect the compatibility between a radar system and SMOS (for HYDROS
the 'analysis' curves are displaced by +24.5 dB).

# 5 Conclusion and recommendation

In this document the use of spectral representations based on Fourier
analysis is proposed in order to give a more accurate estimation of the
unwanted emission power falling into the passive band. Comparisons
between the 2 methods (based on SM.1541 and one based on Fourier
analysis) were given and compatibility analyses were done for the
situation when the --40 dB bandwidth of the radar system is equal to the
start of the passive band. Clearly, this resulted in a more favourable
compatibility situation for the method relying on Fourier analysis
('spectrum method'), but still discrepancies between the power received
by the EESS (passive) sensor and the interference threshold were in all
cases above 20 dB. In all cases a radar antenna gain of 0 dBi has been
assumed.

Also, the amount of frequency separation between the passive band and
the radar channel's centre frequency was investigated for the two radar
systems with respect to SMOS to show the potential for this method for
unwanted emission power calculation for radar systems.

Although the shown radar spectra are for theoretical pulses, this method
does resemble the real radar emission characteristics more than a mask
would do. No allowance has been made for distortions that may occur in a
practical situation, but also no filtering characteristics of the radars
have been investigated that would result in a more favourable situation.
The main result from the static analyses is that mainly due to the very
high peak powers (of the radar systems under investigation), without any
large frequency offset from the passive band or filtering, the
incompatibility remains.

Where this contribution discusses the static analyses, it is envisaged
that a future revision of this document for the next meeting of Task
Group 1/9 would also include statistical/dynamical analyses. This
preliminary study only takes into account the interference threshold
from Recommendation ITU-R SA.1029 and also the availability criterion
(defined in SA.1029 as the percentage of area the permissible
interference level may be exceeded) needs to be taken into account. By
also taking this availability criterion into account (for the
statistical/dynamical analyses), depending on the density of radars and
probability of channel occupation near the passive band, within the
measurement area, the apparent incompatibility may be alleviated to a
great extent.

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