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$//Antenna Flexibility, NPRM, ET Docket No. 96-35, FCC 96-80//$
$/74.536  Directional Antennas Required/$
$/74.641  Antenna Systems/$
$/78.105  Antenna Systems/$
$/101.115  Directional Antenna Standards Table/$

FOR RECORD ONLY
                                Before the
                         FEDERAL COMMUNICATIONS COMMISSION            FCC 96-80
                         Washington, D. C.  20554

                                     
In the Matter of                          )          
                                          )          
Amendment of Parts 74, 78, and 101 )
of the Commission's Rules to Adopt More   )  ET Docket No. 96-35 
Flexible Standards for Directional        )
Microwave Antennas                        )


                      NOTICE OF PROPOSED RULE MAKING

Adopted:  February 29, 1996               ; Released:  March 14, 1996 

Comment Date:  April 26, 1996
Reply Comment Date:  May 13, 1996


By the Commission:

INTRODUCTION
                 
     1.  By this action, we propose to modify our fixed service microwave rules to make
them compatible with new, emerging technologies for directional antennas.  We believe that
the proposed changes will preserve the intent of the rules to maximize spectrum efficiency
and minimize interference.  Specifically, rather than requiring a showing of minimum antenna
gain, we propose to permit an alternative showing that such antennas comply with a
maximum beamwidth requirement.  This alternative will remove a regulatory impediment to
the use by Commission licensees of directional antennas employing new emerging
technologies for which, in contrast to conventional antennas, maximum antenna beamwidth is
not correlated directly to minimum antenna gain.  


BACKGROUND
                                    
     2.  In order to maximize spectrum efficiency and minimize interference, our rules for
fixed microwave antennas specify various technical requirements designed to control the
radiation pattern of directional antenna emissions.  The intent of these rules was to limit the
beamwidth of point-to-point links, thus allowing more point-to-point use in the same spectrum
in a given area.  For many frequency bands, our rules limit beamwidth by specifying
mandatory minimum acceptable antenna gain requirements. 
   
   3.  A directional antenna focuses radio power into a narrower beam than does an
omnidirectional antenna.  This focusing limits the radiation of power in unintended directions
and thus facilitates frequency reuse.  Such directionalization results in a higher effective
isotropic radiated power ("EIRP") in the direction of focus of the antenna than is provided in
any direction by an omnidirectional antenna operating with similar input power.  The EIRP in
other directions is smaller for directional antennas than for omnidirectional antennas of similar
input power.  One way to measure the directionality of an antenna is to measure the
beamwidth of the radiated power directly.  However, this direct measurement is technically
difficult to perform.  An easier measurement is the antenna gain, i.e., the strength of the
radiated power in the center of the beam.  In conventional antennas, these two parameters are
correlated:  high antenna gain is always paired with low beamwidth antenna designs, so that
the gain can be mathematically derived from the beamwidth and vice versa.  

   4.  Recent technological developments have made alternative directional antenna
designs available.  One of these technologies, planar arrays, spreads the power over a large
number of radiating elements in a flat plane in order to achieve a narrow beamwidth.  Such
antennas must split the input power several times in order to feed it to the multiple radiating
elements.  This multiple power splitting results in inevitable power losses which, in turn, limit
the achievable antenna gain.  Thus, while such directional antennas can achieve sufficiently
narrow beamwidths to comply with the intent of our rules, they cannot comply with the
present rule, which literally requires a specific minimum antenna gain.  These technical
developments have prompted this notice.


DISCUSSION
                                    
   5.  The frequency bands listed in Sections 74.536, 74.641, 78.105, and 101.115 can be
divided into three groups:  those bands with maximum beamwidth and minimum antenna gain
requirements, those bands with only a maximum beamwidth requirement, and those bands
with only a minimum antenna gain requirement.  We are not proposing any changes for the
first two groups because we believe the existing rules are adequate.  Specifically, the existing
beamwidth requirements have been in place for many years without any complaints of
harmful interference.  Additionally, while in the past we have regulated antenna gain as a
proxy for beamwidth, in this proceeding we focus on the key factor in minimizing harmful
interference -- maximum beamwidth.  Accordingly, we limit our proposal to those bands that
currently have only a minimum antenna gain requirement.  In Sections 74.536 and 74.641,
this band is 17,700 - 19,700 MHz.  In Section 78.105, these bands are 17,700 - 19,700 MHz
and 38,600 - 40,000 MHz.  In Section 101.115, these bands are 3,700 - 4,200 MHz, 
5,925 - 6,425 MHz, 6,525 - 6,875 MHz (for point-to-point stations authorized after June 1,
1997), 10,550 - 10,680 MHz (for point-to-point stations authorized after June 1, 1997), 
10,700 - 11,700 MHz, 17,700 - 18,820 MHz, 18,920 - 19,700 MHz, 21,200 - 23,600 MHz,
and frequencies above 31,300 MHz.  

   6.  Specifically, we propose to amend Sections 74.536, 74.641, 78.105, and 101.115 of
the Commission's Rules to allow directional antennas to comply with requirements for either
minimum antenna gain or maximum beamwidth.  We do not propose to change any of the
existing requirements with respect to sidelobe suppression because we believe that these
requirements, which are designed to reduce potential interference, can readily be met by both
conventional and new antenna technologies.  We propose to convert the present antenna gain
requirements to the comparable requirements for antenna beamwidths based on two
assumptions:  (1) a parabolic ("dish") antenna with an efficiency of 55% is used as a
reference; and (2) the illumination function taper value is 70.  Table I depicts the existing
gain requirements and the new corresponding beamwidth requirements for bands that do not
have an existing maximum beamwidth option: 




Table I.  Antenna Gain and Equivalent Beamwidths


 Gain (dBi)
Equivalent Beamwidth (degrees)


34
3.5


36
2.7


38
2.2


This technical equivalency is independent of the frequency bands.  

   7.  Appendix B shows the proposed changes to Section 101.115.  We propose to make
the same changes to the corresponding rows in the tables in Sections 74.536, 74.641 and
78.105, which are subsets of the table given in Section 101.115.

   8.  We note that these new types of antennas may differ somewhat from conventional
antennas in the exact shape of the mainlobe.  Thus, even with sidelobe suppression required
by the present rules, the beam shape for a planar array antenna may be different than for a
dish antenna.  While we do not believe that these differences would have a significant impact
on spectrum efficiency, we seek comment on whether such differences might have an impact
on coordination. We propose to address this problem by requiring the coordination process to
treat all antennas as if they had the mainlobe shape and total gain of a conventional parabolic
dish antenna.  However, we invite comments on this approach, and encourage alternative
proposals.


CONCLUSION

   9.  By this action, we propose to modify our fixed service microwave rules to make
them more compatible with certain new, emerging technologies for directional antennas. 
Specifically, we propose to permit alternative showings that such antennas comply with
maximum beamwidth requirements rather than requirements for minimum antenna gains.  We
believe that these proposed changes will preserve the intent of the rules to maximize spectrum
efficiency and minimize interference.  At the same time, such changes will provide
Commission licensees with additional flexibility to use directional antennas employing new
emerging technologies for which, in contrast to conventional antennas, maximum antenna
beamwidth is not correlated directly with minimum antenna gain.


                            PROCEDURAL MATTERS

   10.  Ex parte Presentation.  This is a non-restricted notice and comment rule making
proceeding.  Ex parte presentations are permitted, except during the Sunshine Agenda
period,provided they are disclosed as provided in the Commission's Rules.  See generally
47 C.F.R. Sections 1.1202, 1.1203, and 1.1206(a).

   11.  Initial Regulatory Flexibility Analysis.  As required by Section 603 of the
Regulatory Flexibility Act, the Commission has prepared an Initial Regulatory Flexibility
Analysis (IRFA) of the expected impact on small entities of the proposals suggested in this
document.  The IRFA is set forth in Appendix A.  Written public comments are requested on
the IRFA.  These comments must be filed in accordance with the same filing deadlines as
comments on the rest of the Notice, but they must have a separate and distinct heading
designating them as responses to the Initial Regulatory Flexibility Analysis.  The Secretary
shall send a copy of this Notice of Proposed Rule Making, including the Initial Regulatory
Flexibility Analysis, to the Chief Counsel for Advocacy of the Small Business Administration
in accordance with paragraph 603(a) of the Regulatory Flexibility Act.  Pub. L. No. 96-354,
94 Stat. 1164, 5 U.S.C. Section 601 et seq. (1981).

   12.  Comment Dates.  Pursuant to applicable procedures set forth in Sections 1.415
and 1.419 of the Commission's Rules, 47 C.F.R. Sections 1.415 and 1.419, interested parties
may file comments on or before April 26, 1996 and reply comments on or before 
May 13, 1996.  To file formally in this proceeding, you must file an original and four copies
of all comments, reply comments, and supporting comments.  If you want each Commissioner
to receive a personal copy of your comments, you must file an original plus nine copies.  You
should send comments and reply comments to Office of the Secretary, Federal
Communications Commission, Washington, D.C.  20554.  Comments and reply comments
will be available for public inspection during regular business hours in the FCC Reference
Center, Room 239, 1919 M Street, N.W., Washington, D.C. 20554.  

   13.  Authority.  The proposed action is authorized under Sections 4(i), 302, 303(e),
303(f), and 303(r) of the Communications Act of 1934, as amended 47 U.S.C. Sections
154(i), 302, 303(e), 303(f), and 303(r).
   14.  For further information regarding this Notice of Proposed Rule Making, please
either send an electronic mail message via the Internet to mmarcus@fcc.gov or telephone
Dr. Michael J. Marcus, Office of Engineering and Technology, (202) 418-2418.

   FEDERAL COMMUNICATIONS COMMISSION


   
   William F. Caton
   Acting Secretary           APPENDIX A - INITIAL REGULATORY FLEXIBILITY ANALYSIS


I.   Reason for Action:  The proposals in this Notice of Proposed Rule Making are put forth
on our own initiative with the intention of permitting microwaves users more flexibility in
selecting antennas for their systems.

II.  Objective:  The objective of this proposal is to minimize unnecessary regulatory burdens
on microwave users and manufacturers.

III. Legal Basis:  The proposed action is authorized under Sections 4(i), 302, 303(e), 303(f),
and 303(r) of the Communications Act of 1934, as amended 47 U.S.C. Sections 154(i), 302,
303(e), 303(f), and 303(r).

IV.  Reporting, Record Keeping and Other Compliance Requirements:  No new requirements
are involved.  Applicants will be afforded the option of complying with a standard for
maximum antenna beamwidth as an alternative to complying with the existing requirement for
minimum antenna gain.

V.  Federal Rules Which Overlap, Duplicate or Conflict With These Rules:  None.

VI.  Description, Potential Impact and Number of Small Entities Involved:  It is unknown
how many small entities may be affected.  It is thought that all entities affected by the
proposed change will benefit from this action which allows more flexibility.
   
VII.  Any Significant Alternatives Minimizing the Impact on Small Entities Consistent with
Stated Objectives:  None.                    APPENDIX B - PROPOSED RULE CHANGES


Part 101 of title 47 of the Code of Federal Regulations is proposed to be amended as follows:

                  PART 101 -- FIXED MICROWAVE SERVICES

  1.  The authority citation for Part 101 continues to read as follows:

  AUTHORITY:  47 U.S.C.  154(i), 303, unless otherwise noted.  

  2.  The Antenna Standards Table in paragraph 101.115(c) is amended as follows:
 
  a.  Remove existing entries from Column 3.

  b.  Add new entries to Column 3.

  c.  The Note following the Table is revised. 

 101.115  Directional Antenna Standards Table

* * * * *



                          Antenna Standards


Frequency
(MHz)
Category
Maximum
beamwidth
to 3 dB
points
(included
angle in
degrees)
Minimum
antenna
gain
(dbi)
Minimum radiation suppression to angle in degrees from centerline of main
beam in decibels






5ø
to
10ø
10ø
to
15ø
15ø
to
20ø
20ø
to
30ø
30ø
to
100ø
100ø
to
140ø
140ø
to
180ø


932.5 to 935
A
B
14.0
20.0
n/a
n/a
. . .
. . .
6
. . .
11
6
14
10
17
13
20
15
24
20


941.5 to 944
A
B
14.0
20.0
n/a
n/a
. . .
. . .
6
. . .
11
6
14
10
17
13
20
15
24
20


952 to 960  (8)(9)
A
B
14.0
20.0
n/a
n/a
. . .
. . .
6
. . .
11
6
14
10
17
13
20
15
24
20


1,850 to 2,500  (11)
A
B
5.0
8.0
n/a
n/a
12
5
18
18
22
20
25
20
29
25
33
28
39
36


3,700 to 4,200
A
B
2.7
2.7
36
36
23
20
29
24
33
28
36
32
42
32
55
32
55
32


5,925 to 6,425  (5)
A
B
2.2
2.2
38
38
25
21
29
25
33
29
36
32
42
35
55
39
55
45


5,925 to 6,425  (6)
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
36
55
36


6,525 to 6,875  (5)
A
B
2.2
2.2
38
38
25
21
29
25
33
29
36
32
42
35
55
39
55
45


6,525 to 6,875  (6)
A
B
1.5
2.0
n/a
n/a
26
21
29
25
32
29
34
32
38
35
41
39
49
45


10,550 to 10,680 
(4)(5)
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
35
55
39


10,550 to 10,680 
(6)
A
B
3.4
3.4
34
34
20
20
24
24
28
28
32
32
35
35
55
35
55
39


10,565 to 10,615 
(7)
n/a
360   
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a


10,630 to 10,680 
(7)
n/a
3.5
34
20
24
28
32
35
36
36


10,700 to 11,700 
(5)
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
36
55
36


12,200 to 13,250 
(12)
A
B
1.0
2.0
n/a
n/a
23
20
28
25
35
28
39
30
41
32
42
37
50
47


17,700 to 18,820
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
36
55
36


18,920 to 19,700 
(1)
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
36
55
36


21,200 to 23,600 
(10)
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
36
55
36


31,000 to 31,300 
(2)(3)
n/a
4.0
38
n/a
n/a
n/a
n/a
n/a
n/a
n/a


Above 31,300
A
B
2.2
2.2
38
38
25
20
29
24
33
28
36
32
42
35
55
36
55
36


* * * * *

     NOTE:  Stations must employ an antenna that meets the performance standards for
Category A, except that in areas not subject to frequency congestion, antennas meeting
standards for Category B may be employed.  Note, however, that the Commission may
require the use of high performance antennas where interference problems can be resolved by
the use of such antennas.  For rows in the table in which both minimum gain and maximum
beamwidth are indicated, licensees only have to show compliance with one of the two
parameters.