**JRG-44 Rev.1**

**July 18, 2005**

**ITU-R JRG 1A-1C-8B**

**Report of the Second Meeting**

**May 24-26, 2004**

The second meeting of the Joint Rapporteurs Group (JRG) 1A-1C-8B was
held on 24-26 May 2005 in Southampton, U.K. The meeting was hosted by
the Maritime and Coastguard Agency (MCA). There were 31 participants
representing eight administrations at the meeting.

The meetings of the JRG 1A-1C-8B have the aim of presenting proposals to
the ITU-R for the development of unwanted emission limits in the
out-of-band (OOB) domain of primary radar systems at future ITU-R
Administrative Conferences. Specifically, the task before the JRG
concerns the feasibility of adopting more stringent requirements for
radars with regards to the "roll-off" of out-of-band emissions from the
--40 dB bandwidth. This is a significant and important issue for the
world-wide radar community.

**1. Summary of Meeting**

**1. 1 Opening Remarks (Agenda item 1)**

The JRG Co-Chairmen, Mr. Hinkle and Mr. Hasenpusch, welcomed the
attendees to the second meeting of the JRG, and provided an overview of
the tasks before the JRG as stated in the Terms-of-Reference. It was
mentioned that the Co-chairman representing Working Party 1A, Mr. Wang,
was not able to attend the meeting.

The Director of the MCA, Mr. Wright, welcomed the JRG members, and
provided information on the facilities and other arrangements.
Introductions were given by the attendees of the meeting.

The Chair thanked the JRG members for the many contributions and noted
that each contribution was posted to the JRG web site,
<http://www.its.bldrdoc.gov/meetings/itu-r/>,

hosted by the NTIA Institute of Telecommunication Sciences (ITS).

Mr. Hinkle mentioned that several of the contributions to the JRG
addressed measurement techniques related to primary radar systems. He
noted that Working Party 8B had assigned the review of Recommendation
ITU-R M.1177, *Techniques for measurement of unwanted emissions of radar
systems,* to the Radar Correspondence Group (RCG). Mr. Hinkle then
mentioned that he had received several requests to provide time for an
RCG meeting on May 26^th^. Germany questioned the rationale for
convening an RCG meeting as an \"add-on\" to the JRG on the basis that
the entire RCG membership had not been notified of the meeting. Germany
and others also noted that an ITU "correspondence" group conducted its
business entirely via correspondence. The RCG and JRG Chairs responded
that Thursday's RCG meeting was informal and no decisions were to be
made. Germany removed its objections after the RCG Chairman, Mr.
Sanders, promised he would take detailed notes during the meeting and
post it to the RCG web site.

**1.2 Approval of Agenda (Agenda Item 2)**

The agenda for the meeting was approved as provided, JRG-26.

**1.3 Review of Revised Work Program (Agenda item 3)**

The co-chairman, Mr. Hinkle, expressed the view that there was a need to
improve the effectiveness of the JRG Work Program to complete the task
before the JRG in a timely manner. Concern was expressed that several
contributions have expanded the scope of the task before the JRG to
address the necessary bandwidth (-20 dB) and -40 dB bandwidth formulas
of several types of modulations (FM-pulse, phase-coded pulse and FMCW).
The original task before the JRG was to address only the "design
objective" of Recommendation ITU-R SM.1541 which was limited to the
roll-off from the -40 dB bandwidth. It was the consensus of the group
that it was necessary to establish the necessary bandwidth (-20 dB) and
-40 dB bandwidth formulas prior to addressing the feasibility of a more
stringent roll-off from the -40 dB bandwidth.

Based on this conclusion, it was decided to assign a Priority 1 to tasks
associated with the establishment of the necessary bandwidth (-20 dB)
and -40 dB bandwidth formulas. A Priority 2 would be assigned to
addressing the roll-off. It was also proposed that radar output devices
be separated into two groups: cross-field devices (e.g., magnetrons),
and other devices (linear-beam (TWT, klystrons, twystrons) and
solid-state devices). Milestones would also be identified for each task
or study area.

It was also suggested that drafting groups be formed for specific tasks
to effectively create a means of correspondence between meetings, and
that a table of action items be maintained to identify study areas,
leading administrations, and milestones. The table of action items would
be posted on the JRG web site to track the status of work on the tasks.
Also, contributions pertaining to each task would be identified in the
JRG Work Program.

A DRAFT Revision of the Work Program was distributed at the end of the
JRG meeting. See Attachment 1 for the JRG Revised Work Program.

**1.4 Introduction of Contributions (Agenda item 4)**

There were fifteen contributions to the second meeting of the JRG
(Document JRG-28 through JRG-42). A summary of discussions on each
contribution is provided in Attachment 2.

Documents JRG-40 and JRG-42 were referred to the RCG for consideration
since they were associated with Recommendation ITU-R M.1177, *Techniques
for measurement of unwanted emissions of radar systems,* which is under
the purview of the RCG. It was also decided that Document JRG-28
(Document 8B/111-E, 18 February 2005) was not within the JRG
Terms-of-Reference. However, since it was sent to the JRG for
information, it was introduced and discussed by the JRG. These documents
will remain on the JRG web site.

It was decided to attribute the contributions to specific areas of
study, and introduce them in order. The attribution was as follows:

EESS Compatibility: JRG-28

Non-FM Pulse: JRG-34, JRG-35(Rev.1)

FM Pulse : JRG 32, JRG-33, JRG-37, JRG-38

FM-CW : JRG-39

Measurements of OOB Emissions: JRG-36

Airborne Radar Systems: JRG-41

**1/5 Discussion/Demonstration of ITU-R Radar Emission Mask Model
(Agenda item 5)**

There were three contributions related to the ITU Emissions Mask Model:
JRG-29, JRG-30, and JRG-31. The Excel model is contained in JRG-31. The
Co-chairman, Mr. Hinkle, mentioned that at the first JRG meeting that
some administrations experienced problems with applying the model.
Attempts were made between the U.S. and Germany prior to the second
meeting of the JRG to identify the problems; however, the software
problems were not resolved.

The current version the MS-Excel software developed by the U.S. was
demonstrated. Changes made to the version presented at the first meeting
included:

-   The frequency display can now be normalized to 0 Hz.

-   There is a help button that works if Doc. JRG-31 is in the same
    folder as the xls file.

-   The model can now take comma separated ASCII data as input.

The model was used successfully by the U.K. and U.S. However, Japanese
and German delegates experience errors that make it impossible to use
the software. Several JRG members stated that it may be necessary to
have Visual Basic or Service Pack 2 or higher on the PC. It was stated
that the PC system requirements need to be clearly identified in the
User's Manual (JRG-29). Germany stated that it had the latest version of
Excel, and Service Pack 2 on XP, and still could not get it to work. It
was mentioned that the model can not be accepted as an ITU-R model until
the difficulties experienced by some of the administrations are
resolved.

The use of Doc. JRG-32 (error report form) was encouraged to forward
errors to Robert Sole (<rsole@ntia.doc.gov>) of the U.S. to help resolve
the operational problems with the model.

**1.5 Working Document Towards a Preliminary Draft Revision of
Recommendation ITU-R SM.1541 (Agenda Item 6)**

It was the view of the group that further progress needed to be
completed on the task before the JRG before a mark-up of SM.1541 could
be started. The U.K. volunteered to provide a draft outline for the JRG
report (See Attachment 3).

**1.7 Date/Location of the Next Meeting (Agenda item 7)**

3^rd^ meeting: January 17-19, 2006. Hosted by the U.S. at the Institute
of Telecommunication Sciences, Boulder, Colorado,

4th meeting: Hosted by Germany

It was decided not to fix dates for further meetings at this time. Below
is a table of the schedule of meetings of the cognizant working parties
of the JRG.

MEETINGS OF ITU-R STUDY GROUPS AND

**WORKING PARTIES 2005 -- 2006**

**and their relationship to the**

**Work Programme of the JRG 1A-1C-8B**

  ----------------------------------- -----------------------------------
  **STUDY GROUP/WORKING PARTY**       **DATES OF MEETING\***

  WP 8B                               September 20 -- 27/2005

  WP1A                                September 26 -- 30/2005

  WP1C                                September 26 -- 30/2005

  SG1                                 October 24 -- 25/2005

  SG8                                 November 21 -- 22/2005

  WP8B                                February 22 -- March 3/2006

  WP8B                                September 6 -- 14/2006

  WP1A                                October 9 -- 13/2006

  WP1C                                October 9 -- 13/2006

  SG1                                 October 16 -- 17/2006

  SG8                                 December 7 -- 8/2006
  ----------------------------------- -----------------------------------

**\* As listed by the ITU -- 1 June 2005**

Based on the above meeting schedule the forth meeting of the JRG would
have to be held not later than July 2007. Concern was raised that the
work of the JRG has expanded beyond the "design objective" of
Recommendation ITU-R SM.1541 to include review of the -20 an -40 dB
bandwidth formulas. This expansion in work before the JRG may make it
difficult for the JRG to complete its work in the 2003-2007 study
period.

**Contacts:** Jian Wang

Co-chairman, Working Party 1A

Thomas Hasenpusch

Acting Co-chairman, Working Party 1C

Robert Hinkle

Co-Chairman, Working Party 8B

> **ATTACHMENT 1**

##  JRG-43

June 17, 2005

## Revised Work Program

#### JRG 1A-1C-8B

1\. Background

Unwanted emission masks in the out-of-band domain for primary radar
systems are contained in Recommendation ITU-R SM.1541, Annex 8. The
ITU-R out-of-band emission masks for primary radar systems are intended
to recommend an acceptable degree of electromagnetic compatibility among
radar systems, and between such systems and those of other radio
services sharing the frequency spectrum.

In the development of the out-of-band emission masks for primary radar
systems, it was the view of several administrations that there was a
need to further investigate the state-of-the-art radar systems and their
ability to suppress unwanted emissions. This review of radar unwanted
emissions in the out-of-band domain is to be completed by 2006. See
Recommendation ITU-R SM.1541, Annex 8, Note 3. The outstanding issue
concerns the "design objectives" highlighted in this document. This
"design objective" concerns the possibility of making more stringent the
requirement for radars with regard to the "roll-off\" of out‑of-band
(OOB) emissions.

The outcome of this study may result in revisions to Recommendation
ITU-R SM.1539, which addresses the boundary between the out-of-band and
spurious domains, and Recommendation ITU‑R SM.1541, which addresses
out-of-band emissions domain.

Pursuant to initiating this study, Working Party 8B revised Question
202/8 to provide guidance to administrations in conducting their
investigation.

2\. Objective

The objective of this work program is to review the current ITU-R limits
for unwanted emissions in the out-of-band domain contained in Annex 8 of
Recommendation ITU-R SM.1541, and assess the feasibility of establishing
guidance to promote more effective and efficient use of the spectrum.

3\. Approach

In order to accomplish the above objective, the following tasks will be
undertaken:

a\) Develop a software tool that will provide current ITU-R emission
masks and alternative emission masks for comparison with measured radar
emission data (Priority 1).

b\) Review the current necessary bandwidth (-20 dB) formulas and --40 dB
bandwidth formulas for the various types of modulations used by radar
systems, and develop new formulas as appropriate (Priority 1).

c\) Identify, through measurements, characteristic radar emission
spectra considering such parameters as: waveforms (e.g. pulse shape and
modulation); types of output devices; RF filter technologies; and
antenna types (Priority 1).

d\) Analyze the measured emission characteristics to assess the
feasibility of establishing more spectrum efficient emission masks
(Priority 2).

e\) Discuss draft revised emission masks, and identify state-of-the-art
capabilities which may allow radars to operate more efficiently while
recognizing economic impacts and mission requirements to achieve
efficient and effective operation.

f\) Draft a report, including a DRAFT Revision of Recommendation ITU-R
SM.1541, Annex 8, and provide the results of these studies to Working
Party 1A, 1C and 8B.

4\. Specific areas requiring studies

1)  Develop a software tool that will provide current ITU-R emission
    masks and alternative emission masks for comparison with measured
    radar emission data (Priority1). See documents: JRG-2, 3, 4, 5, 29,
    30, 31.

2)  Review the necessary bandwidth (-20 dB) and --40 dB bandwidth
    formulas given in ITU-R SM.1541 and develop new formulas as
    appropriate, particularly for the following types of modulations
    (Priority 1):

    a.  Non-FM pulses (unmodulated pulses), including radars using
        magnetrons with low pulse width to rise time ratio (Doc. JRG-7,
        9, 10, 34, and 35 rev.1).

    b.  FM-pulsed modulated waveforms, including non-linear FM. Analysis
        and measurements have shown that the current formulas especially
        for FM-pulsed modulated waveforms are too generous for large
        time-bandwidth products (compression ratios). (Doc. JRG-7, 10,
        12, 13, 17, 19, 21, 32, 33, 37, and 38)

    c.  FMCW, including radars operating at long wavelengths. Analysis
        indicates that the current necessary bandwidth (-20 dB) and -40
        dB bandwidth formulas for FMCW modulated waveforms may not be
        representative for all cases. (Doc. JRG-7, 39)

    d.  stepped chirp, phase-coded pulses (PSK/QPSK, MSK/GMSK, and
        Taylor quadriphase), phase-coded CW, step FM, multi-carrier
        radars (Doc. JRG-7).

3)  Identify, through analysis and measurements, the achievable roll-off
    from the --40 dB bandwidth for the following output devices as a
    function of the class of amplification (Priority 2):

    a.  cross-field (Doc. JRG-14, 16, 20, 22, 34, 40, 42)

    b.  linear beam (Doc. JRG-7)

    c.  solid state (Doc. JRG-36 and 39).

4)  Investigate the feasibility of implementing pulse shaping and
    filters between solid state Transmit-Receive (T/R) Modules and the
    antenna elements. These studies should consider the type of platform
    (e.g. ground based, ship borne, airborne, space borne) (Doc. JRG-7
    and 33) (Priority 1).

5)  Review the definition and description of rise and fall time (Note 1
    of Annex 8 of Rec. ITU-R SM.1541). Measurements have shown that the
    pulse forms are sometimes not nearly trapezoidal, especially for
    radars using magnetrons that tend to overshoot the maximum level for
    a very short time at the beginning of the pulse (Priority 2).

    a.  Determine the characteristics of airborne radar systems (Doc.
        JRG-41), obtain emission spectrum measurements on representative
        airborne systems with different output devices, and identify
        factors that could affect the emission spectrum (Doc. JRG-41).

7\) Impact of ITU-R out-of-band emission limits on radars operating at
long wavelengths (Doc. JRG-39) (Priority 1).

5\. Drafting groups

Three drafting groups were formed at the second meeting of the JRG.
Correspondence for the drafting groups will be conducted via e-mail.
Drafting Group leads will establish e-mail groups.

##### JRG-DG1: FMCW Modulated Waveforms

##### JRG-DG2: FM-Pulse Modulated Waveforms

**JRG-DG3: Magnetron Emission Mask:**

The Terms-of-Reference and lead contacts for the above JRG Drafting
Groups are provided on the JRG web site:
<http://www.its.bldrdoc.gov/meetings/itu-r/>. See Document JRG-46.

6.  Action items

Four action items were identified at the second meeting of the JRG. A
description of the action items, and administration responsible for the
task are provided on the JRG web site:
[**http://www.its.bldrdoc.gov/meetings/itu-r/**](http://www.its.bldrdoc.gov/meetings/itu-r/).
See Document JRG-46.

7\. Next meeting date / location and aims

3^rd^ meeting: January 17-19, 2006. Hosted by the U.S. at the Institute
of Telecommunication Sciences, Boulder, Colorado.

a.  Further structuring of final report

b.  First proposed revision of Rec. ITU-R SM.1541

4th meeting: Hosted by Germany

#### ATTACHMENT 2

> **Overview of Contributions to**
>
> **Second JRG Meeting**

**[JRG 28:]{.underline}** 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 (Document 8B/111-E, 18 February 2005).

This contribution was introduced by ESA. The paper is a liaison
statement from ITU Task Group (TG) 1/9, and requests information from
the JRG on a realistic density model for radar systems that operate near
1400 MHz. It was the view of the JRG that the paper was not within the
Terms-of-Reference of the JRG. The JRG suggested the liaison statement
be addressed by the Radar Correspondence Group (RCG).

In the liaison statement, TG 1/9 seeks advice on the realism of the
approach of using FFT emission rather than the emission masks in
SM.1541. The group expressed the view that SM.1541 is an emission mask
for primary radar systems, and could result in an over estimation of the
unwanted emissions falling into the passive band. However, it was also
the view of the group that the FFT methods would provide relatively
accurate emission spectra in the region from the center frequency to the
-40 dB point. However, FFTs are a much less accurate method to estimate
emission spectrum levels in the frequency region beyond the -40 dB
point. In reality, beyond the -40 dB point, the output device strongly
influences the width and shape of the radiated emission spectrum. For
example, linear-beam devices (TWTs, klystrons, and twystrons) and
solid-state devices yield relatively clean spectra, while magnetrons and
CFAs generate more noisy output spectra. Therefore, it was suggested
that measured data should be used to perform the compatibility analysis.
The group noted that there was little radar expertise in TG 1/9.

It was mentioned that TG 1/9 meets prior to the Working Party 8B meeting
in September. The representative from TG 1/9 expressed the view that it
would be helpful if a liaison statement from Working Party 8B could be
sent to TG 1/9 for their meeting in September. The consensus was that
the document should be referred to the RCG for timely inputs. It was
suggested that the chairman of the RCG, Mr. Sanders, contact the
Chairman of Working Party 8B to see if the RCG should address the paper,
and provide a liaison statement back to TG 1/9.

**[JRG-34:]{.underline}** Maritime Radar Spectra

This contribution was introduced by the U.K. The document presents
measurements of emission spectra of different existing maritime radars
using magnetrons. The results show that some of the radars measured
cannot meet even the existing 20 dB roll-off, some do meet this
requirement, and some even meet the future design objective. The author
pointed out that the measurements were made on new equipment and that
performance may get worse as the equipment ages. It was mentioned that a
large majority of the radars (90% or more) operating today use
magnetrons.

It was mentioned that at the 1^st^ meeting of the JRG, maritime radar
spectrum data was presented from current versions of shipborne radar
equipment. Using the input documents to the meeting a preliminary
document was produced (see JRG-22) that started to make the case for
exclusion of maritime mobile radars from a more stringent roll-off
(i.e., the current discussion of a "design objective" of SM.1541).

There was a discussion on how much the emission mask can be shifted in
frequency. It was mentioned that SM.1541 states that the B (-40 dB)
bandwidth can be offset from the frequency of maximum emission level,
but the necessary bandwidth (RR No. 1.152) and preferably, the overall
occupied bandwidth (RR No. 1.153), should be contained completely within
the allocated band. Mr. Hinkle volunteered to clarify the requirement of
the necessary bandwidth having to be within the allocated band, and
submit an input document to the JRG.

It was suggested that magnetron radars be treated separately from
linear-beam and solid-stated output device radar systems. The group
seemed to accept that suggestion based on the fact that magnetrons have
unique characteristics.

**[JRG-35 (Rev 1):]{.underline}** Derivation of the necessary bandwidth
(-20 dB) and -40 dB bandwidth formulas for un-modulated pulse waveforms
(non-FM pulses).

This contribution was introduced by the U.S. The paper provided the
mathematical background and development of the equations that calculate
the necessary bandwidth (-20 dB) and -40 dB points of un-modulated pulse
waveforms. The document supersedes document JRG-09, and provides a more
detailed derivation of the formulas in ITU-R Recommendations SM.853-1
and SM.1541.

The derivations were based on trapezoidal pulses. It was the view of the
group that at this time there appeared to be no reason for further
review of the -20 dB and -40 dB formulas of un-modulated pulse (non-FM
pulse) waveforms. There was some discussion of the definition of
necessary bandwidth for radar systems. It was pointed out that
Recommendation ITU-R SM.853 defines the necessary bandwidth for radar
system as the -20 dB bandwidth.

**[JRG 32:]{.underline}** Earth exploration-satellite service (active)
and the space research service (active) (SAR) out-of-band -40 dB
bandwidth as a function of time-bandwidth product and unequal rise/fall
times

NASA researched the influence on emission bandwidths and mission for
active Earth Exploration Satellite Systems (EESS) radar modulations with
unequal rise and fall times. NASA stated that the quality of the final
image obtained from the radar is affected by the rate of the emission
roll-off. In general, the quality of the image is enhanced with
waveforms that have sharp roll-offs that reduce the noise level in the
frequency away from the carrier. NASA engineers want waveforms with
large time-bandwidth products (compression ratios) with long rise/fall
times in the 0.1 -- 0.4 usec range. If short rise/fall times on the
pulses are used, the 40 dB/decade roll-off may not be met. The author
agreed to revise the document so that all reference to dB/octave would
be converted to dB/decade.

NASA noted that the methodologies of SM.1541 generate bandwidths greater
than those generated using an analytical FFT approach. NASA agreed to
provide detailed technical parameters of EES and SAR radars.

The group noted that as the compression ratio of LFM increases, the
spectrum falls off more rapidly.

**[JRG 33:]{.underline}** Further considerations of radar spurious
emission masks

This contribution was introduced by the U.K. The paper summarized other
U.K. contributions to the RCG and JRG (RCG-17, JRG-12, 13, and 21), and
also echoed other JRG input papers that conclude that the formulas in
SM. 1541 for FM modulated pulse waveforms overestimate the ‑20 and -40
dB bandwidth.

The contribution states that the work of "Newhouse" (See JRG-10) gives a
good approximation to the B~w~(-20) envelope, and that the theoretical
analysis takes no account of practical implementation issues associated
with these types of pulses. Radar pulses are never truly Trapezoidal or
Rectangular. Thus, allowance for practical implementation will be
required for the -40 dB bandwidth formula.

The paper concludes that for frequency agile radars or active phased
array radars it is not possible to use a channel filter to improve the
roll-off of the transmitted spectrum. However, it may be possible to
improve the roll-off at the edge of the agile band by using a
band-limiting filter. However, these filters are generally used to
suppress harmonics, and not to reduce OOB emissions. It was stated that
in space-borne solid-state radar, the manufacturers have been reluctant
to put in filters partly due to insertion losses (increases in system
noise). A question was raised on the feasibility of inserting filters
between T/R modules and antenna elements. The answer was that these
filters will not have enough (Q) to improve the OoB emissions, and that
dynamically tuned RF filters are not available. Mr. Holloway offered to
provide a paper on radar architecture related to the ability to provide
filtering to improve unwanted emission spectra.

It is also concluded that for the waveforms under consideration, pulse
shaping is the only option to control the spectrum. There was a question
on how difficult pulse shaping is to implement. Discussions indicated
that it depends on the type of radar. In some types of radar it is very
easy to implement pulse shaping with almost no cost impact if it is
considered in early design stages, while in some others it might not be
possible at all. For active phased array solid-state radars, it may be
difficult because the output stage is driven into saturation. Pulse
shaping, however, is very effective. An example of an air traffic
control radar using a bottled solid state radar is described in Document
JRG- 36. It was suggested that a paper on radar architecture related to
pulse shaping would be beneficial. There was no volunteer to provide a
paper on pulse shaping radar architecture.

It was mentioned that SM.1541 does not have any limits on the
"sharpness" of the leading/falling edges of FM modulated pulse
waveforms. However, the U.S. RSEC requires that radar pulses with rise
times of less than 0.1 usec be justified. It was suggested that the
group investigate the possibility to meet a -40 dB/decade roll-off for
FM-pulsed radars by setting up a dependency between the chirp (B~c~) and
rise/fall times that ensures the spectrum drops off beyond the point
where theoretical -20 dB/decade and - 40 dB/decade curves meet (see
figure in Secton 7.3 of the document).

The presenter stated that there is a need for more measured data from
administrations. It was also mentioned that to date there had not been
any contributions addressing stepped chirp modulated radar systems.

**[JRG-37:]{.underline}** Study of formulas for representing the
necessary bandwidth and -40 dB bandwidth of FM modulated pulse radar
waveforms.

This contribution was introduced by the U.S. The paper introduces
proposed new formulas to calculate the --20 and --40 dB bandwidths of
FM-pulse waveform radars. It is stated the proposed necessary bandwidth
(-20 dB bandwidth) and -40 dB bandwidth formulas presented in this
document are still under review, and are not finalized domestically. The
preliminary study indicated that the current -40 dB bandwidth equation
for FM-pulsed waveforms may be too stringent for low compression ratios
(less than 500), but may be too generous for very large compression
ratios (greater than 5000).

The paper states that since the -40 dB bandwidth is used to define the
emission mask for radar systems, any changes to the current -40 dB
bandwidth formula must take into consideration factors that are not
included in theoretical computations such as FFTs and Newhouse
approximations. These factors include, but are not limited to,
implementation factors such as distortion in amplification chains,
inherent output device characteristics, and measurement factors. Any
follow-on study must include measured data in establishing the -40 dB
bandwidth formula.

The JRG agreed to establish a Drafting Group with members of the UK and
US that will evaluate the developed formulas presented in this and other
documents related to FM-pulse waveform modulation. The presenter agreed
that he would incorporate figures used in the presentation that were not
in the paper as Rev 1 to the contribution.

**[JRG-38:]{.underline}** Comments on proposed changes to FM mask in
document JRG-7

This contribution was introduced by the U.K. The paper provides comments
on the formula proposed in a contribution to the first meeting of the
JRG (JRG-7) for the -40 dB bandwidth of FM-pulse waveforms given by
formulas in Recommendation ITU-R SM.1541-1, Annex 8). The paper states
that the FM-pulse formula for the -40dB bandwidth is under review, and
that the current thinking is to redefine the formula to be:

  -----------------------------------------------------------------------
  ![](media/image1.wmf){width="1.9166666666666667in"
  height="0.5416666666666666in"}

  -----------------------------------------------------------------------

where : *X* = 1.2 whereas in reference \[8\] it is 2.0

*A*= typically 0.105, as in reference \[8\]

*k* = typically 6.2 as in reference \[8\]

The paper presents several theoretical emission characteristics using
FFTs for a 10 MHz frequency sweep and a range of rise times. The paper
concludes that the value of 1.2 for the factor X in the above ‑40 dB
bandwidth formula for short rise times can be less than the theoretical
spectrum. The group agreed with the findings of the study.

**[JRG-39:]{.underline}** The impact of ITU Out-of-band emission limits
on radars operating at long wavelengths.

This contribution was introduced by Australia. The paper states that it
is a common opinion within the radar community that the current
definition of necessary bandwidth for FMCW waveforms within
Recommendation ITU-R SM.1541 results in an unrealistic and narrow value.
To date, submissions to the JRG have focused on pulse radars operating
in the microwave bands. There has been little consideration of the
issues surrounding unwanted emissions from radars operating at long
wavelengths (less than 50 MHz) using frequency modulated continuous wave
(FMCW) waveforms and phased transmit arrays. The paper examines the
effects of current and proposed ITU limits for out-of-band emissions on
radars utilizing long wavelengths and FMCW waveforms.

A question was raised whether the frequency deviation term, B~d~, in
Equation 2 is the frequency deviation from the center frequency or the
whole range of the frequency shift. It was agreed that the definition of
for the term B~d~ needed to be clearly defined. It was mentioned that
more spectrum efficient FMCW emissions could be achieved if the fly back
was controlled.

It was agreed to form a JRG Drafting Group 1 with Australia to lead the
drafting group, and participation from members from the U.S, U.K. and
Thales Netherlands. A suggestion was made to extend the work of the
drafting group to all radars using FMCW, regardless of the frequency.
The drafting group will identify more realistic necessary bandwidth (-20
dB) and --40 dB bandwidth formulas for FMCW waveforms, and review the
feasibility of the application of a 40 dB/decade roll-off with these new
formulas for practical combinations of waveform parameters. Also, the
drafting group will clarify the definition of the frequency deviation
term, B~d~, for FMCW waveforms.

**[JRG-36:]{.underline}** Working document towards the determination of
the feasibility to achieve more stringent out-of-band emission limits
for primary radar systems

The U.S. presented JRG-36. The paper provided measured data on two
solid-state radar systems. Both systems were large ground-based radar
systems. One system used pulse shaping and a bottled solid-state output
device. The second radar system used a mechanically steered phased
array, individual solid-state transmit/receive (T/R) modules feeding
each antenna element, and RF filtering.

The measurements on the radar system using a bottled solid-state output
device indicated that with pulse shaping, it may be possible to achieve
a 40 dB per decade roll-off for FM-pulse systems with long pulses
(greater than 50 μs). It was noted that there are FM-pulse radar systems
that have pulse lengths in the order of only 1 μs. It was not known at
this time if pulse shaping of FM modulated pulses with pulse lengths in
the order of only a few microseconds would result in as clean emission
spectra.

The measurements on the radar system with solid-state phased array
antenna radar systems using filters between the T/R modules and each
antenna element may be able to achieve a 40 dB per decade roll-off at
the allocated band edges. It should be noted that only limited
measurements have been conducted on this type of solid-state system at
this time. Also, at this time, factors such as cost, platform size, and
mission have not been addressed in assessing the feasibility of
implementing filters between the T/R modules and each antenna element. A
question was asked if the radar had RF filters between each T/R module
and the antenna element, or only in a row feeding the T/R modules and
the antenna elements. The presenter did not know the answer to the
question.

The paper concludes that additional measurements and studies are
required taking into consideration radar mission, cost, type of
platform, and additional range of pulse parameters and pulse modulation
types to assess the feasibility of the design objective in
Recommendation ITU-R SM.1541, Annex 8.

**[JRG 41:]{.underline}** Airborne radar systems

The U.K. presented JRG 41 which provides a brief description of the uses
and technical parameters of airborne meteorological 9 GHz radars. The
paper indicates that 9 GHz airborne radars use both magnetrons and
solid-state output devices.

A question was asked if airborne radars would move more toward
solid-state output devices in the future. It was mentioned that some
radar manufacturers are selling solid-state airborne radar systems
particularly in weather radars. It was mentioned that solid-state radar
systems provide Doppler signal processing which enhances detection of
wind shear during approach. A radar representative emphasized that
magnetrons have a superior size-to-power ratio with respect to the
size-to-power ratio of solid-state airborne radar. Therefore, magnetrons
are preferred for radar to be installed in small aircraft, while
solid-state transmitters are preferred for large commercial aircraft.
Solid-state transmitters are not capable of producing the same level of
power as a magnetron. Also, the high EIRP of magnetrons is required to
trigger Search and rescue transponders in, e.g., life rafts.

A question was asked if airborne radar systems incorporate interference
suppression techniques. It appears that not all airborne radar systems
use interference suppression techniques, and are susceptible to CW
interference. It was mentioned that RTCA MOPs contain a requirement for
interference suppression circuitry.

There was a question whether airborne radars have to be type approved or
certified like marine radars that may include sideband emissions. The
question could not be clarified during the meeting.

ATTACHMENT 3

ITU-R JRG 1A-1C-8B

DRAFT OUTLINE OF THE REPORT

# 1 BACKGROUND

To include a short history of the development of unwanted emission
Recommendations in the ITU-R.

To include the terms of reference and how the "design objectives" were
included in the ITU-R work programme.

Etc

# 2 INTRODUCTION

To include the method of working -- the number of meetings
(location/date etc in an Annex) the participants and their affiliation
(in an Annex).

The work programme, the identification of studies and the breakdown of
the work items (working groups/drafting groups).

An assessment by the Co--Chairman of the complexity of the task and the
feasibility of achieving it in the suggested time scale.

A list of documents (in an Annex) and their association with specific
parts of the work programme.

# 3 THE JUSTIFICATION FOR THE PROPOSALS

The revision of Annex 8 of Recommendation ITU-R SM.1541 Annex 8 include
the exceptions to a more stringent roll-off as stated in the current
version of Annex 8.

A description of the justification for each proposed revision of Annex
8, to include reference to input documents as appropriate.

**4 THE PROPOSALS FOR REVISION OF ANNEX 8 OF SM.1541**

The provision of a revised version of Annex 8 in the appropriate format.

**5 COMMENT ON THE FUTURE OF ANNEX 8**

Possible exceptions and their future development.

The continuing impact of new technology.

The application of the proposals to advanced systems with sophisticated
operational requirements.

# 6 The means by which the JRG proposals might be implemented

The relationship between the ITU Recommendation (as amended) and the
Radio Regulations and the time scales in which any proposals should be
implemented.

# 7 Additional issues during the course of the JRG work programme

To be developed.

# 8 Other aspects

To be developed.