Novel Wideband MIMO Antennas that can cover the whole LTE spectrum in Handsets and Portable Computers

weightwelloffMobile - Wireless

Dec 12, 2013 (4 years and 20 days ago)

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Novel Wideband MIMO A
ntenna
s

that
can

cover

the whole
LTE

spectrum
in

Handsets and Portable
Computers

Customers’ increasing expectations for speed,
bandwidth, and global access is driving the evolution
of wireless broadband technology.
Customers want
more information, such as business and
consumer applications, and entertainment available
through their mobile devices, but with greater
speeds[1]. LTE represents the next big step toward
the 4th generation (4G) of radio techno
logies which
expected to increase the capacity and speed of
mobile telephone networks. These expectations put a
significant burden on device performance.

The antenna is becoming an increasingly critical
component for LTE device vendors, In order to meet
th
e requirements of expanded, high cell capacity
data rates, multiple antenna configurations (MIMO)
specified for LTE mobile devices

as smart phones,
tablets and no
t
e
books. It is possible that a future
terminal device will have more than 20 antennas to
cover

all the important wireless applications [2], in
addition the industry is painfully aware of the issues
that surround implementing LTE in small mobile
devices with already limited space and extremely
high performance expectations. Due to this trend,
wideba
nd coverage is a hot issue that has to be
addressed

[3].

The latest GSMA’s wireless intelligence report,
predicts that there will be 38 different spectrum
frequency combinations used in LTE deployments
by 2015. The lack of spectrum harmonization
represents

a key challenge for the emerging LTE
ecosystem, potentially preventing vendors from
delivering globally compatible LTE products such as
devices and chipsets
.
Spectrum fragmentation has
the potential to hinder global LTE roaming if device
manufacturers are

required to include support for
many disparate frequencies in their devices

[4]
.

To satisfy the end user expectation of a global
LTE experience, the FDD/TDD dual mode device
is highly preferred and a universal RF chipset that
supports all
global LTE bands should be required
[5]
.
Thus, a compatible wide band LTE antenna is
absolutely needed
.

Device makers are finding it difficult to decide
which bands to prioritize as chipsets and handsets
are developed. The priority is the 800 megahertz
band
. Most of the investment has been directed
towards that because it is the band that two
-
thirds of
current LTE users occupy, largely driven by the US
network roll outs of Verizon Wireless and AT&T

[
6
]
. This low frequency band means larger antennas
in terms
of size, which is a challenging issue
keeping

in mind limited size of LTE devices.

However, in
Europe and even more so in the Asia
-
Pacific region
there are a greater number of LTE bands and
combinations to be addressed.

The roaming point is a critical one
because operators
are targeting LTE towards their high value
customers, in the initial stages of the market. Those,
by definition, are business users with the propensity
to roam. Yet, in fragmented regional markets such as
Europe, LTE roaming is some way o
ff as operators
will be providing LTE in different bands and devices
will need to be able to seamlessly switch between
the frequency bands used for LTE in addition to the
2G and 3G networks
[
6
]
.

What is clear is that in order to service the high
spending, f
irst wave of LTE users some form of
roaming between LTE spectrum bands and the 2G
and 3G networks will be required. It seems illogical
that operators will sell the benefits of LTE in their
home markets but, as soon as the high spending LTE
customer changes

country, they will only be offered
2G or 3G service. For operators, a world LTE device
at a keen price point is needed


but it remains
some time away from appearing in the market

[
6
]
.

The bigger issue is that operators are running out of
3G capacity. The
y need handsets so they can migrate
users to 4G because it’s more efficient

[
6
]
.

The urg
ent demand for wideband LTE coverage

represents a serious challenge
facing

antenna
vendors

who found themselves in trouble, stuck with
the current passive antenna techn
ology trying to
adapt
it
to serve the wideband demand
.
Unfortunately, the current technologies were not
resilient enough to achieve that purpose.
So
antenna
vendors ga
ve up on
it
,
having

a definitive

belief that
passive antenn
as have reached its limits

[7]
.

Therefore,
they adopted the active
tunable
antenna
approach to fulfill the market need for world LTE
devices, trading the passive antenna simplicity with
active antenna
complexity
.

But we can say with
confidence that the passive antenna technology have
n
ot come to an end yet.

Passive antennas have
various advantages over the active tunable antennas.

First of all, the passive antenna doesn’t have to be
supported with RF co
ntrolling circuit to do the job
as
the active one, so it will save large space requir
ed
inside the handset to fit both the antenna and the RF
circuit.

The problems of the RF circuit will not end here, as
the additional circuit components
connected to the
antenna surely will suffer from impedance
mismatch

that will be translated into a severe decrease in the
efficiency of the antenna.

In
addition,

Active antenna is power consuming, as
the battery life is significantly decreased.

Finally,
active antenna seems to have band limitations too, as
the
maximum num
ber of bands that commercial LTE
antennas
can support is 13 bands out of 35 potential
LTE bands.

On the other hand,
Current handset antenna
technology still tide with
extended

ground plane’s
dilemma, as the antenna is not just the module that
fit under the

ear phone but also includes the large
PCB groun
d plane
that must have a minimum size

for the antenna to have an acceptable performance
,
adding an extra volume counted on the

total size of
the antenna.

Wide band passive antenna

AMANT

Antennas

is providing the market
with
a
novel

antenna technology to solve the problem of
urgent need for universal LTE devices
. The new
technology
can cover all the possible LTE

spectru
m
bands using only two antennas

with bandwidths of
73%

and 75.8% respectively
w
ithout using any
matching or tuning circuits
. The first antenna is
covering
the low band LTE spectrum

starting from
698 MHz up to 1.51 GHz which include
s

LTE band

number
s

5,

8,

11,

12,

13,

14,

17,

18,

19,

20,

21.
The
second
one

is covering the high band portion of the
LTE spectrum

starting from
1.71 GHz to 3.8 GHz
corresponding to
LTE
band numbers 1, 2, 3, 4,

7,

9,

10,

22,

23,

25,

33,

34,

35,

36,

37,

38,

39,

40,

41,

42,

43.

This

means a total number of 32 LTE bands can
be covered
beside the 2G and 3G
frequency
bands as

700MHz WiMax, CDMA/TDMA/GSM800 (824

894MHz)
,
low L band GPS (1.2GHz), L
-
band DVB
-
H (1452

1492MHz), GPS (1575MHz), GSM1800
(1710

1880MHz), PCS1900 (1859

199
0MHz),
U
MTS (1900

2170MHz),
Bluetooth/WiFi
(2.4GHz), WiMax (2.3

2.5GHz), and IMT
-
2000
WiMax (2.5

2.69GHz)
.

The new antenna technology can be implemented in
smart phone handsets
, tablets
, laptops and
notebooks. The geometry of the antenna is shown in
Fig.1, which
can be scaled and optimized for any
application or any frequency band. M
ultiple

antenna
configurations

is provided

according to the available
space
inside the device with different size
choices

of

0.
1x
0.
1x15
.
6

c
m
,
0.
2x
0.
2x15
.6 c
m
or

0.
4x
0.
4x15
.6
c
m for

the

low band antenna and
0.
1x
0.
1x5
.
5
5 c
m
,
0.
2x
0.
2x5
.55 c
m
or

0.
4x
0.
4x5
.55 c
m for the high
band antenna.




Fig. 1
Geometry of the new wideband antenna

The low band
antenna design is flexible enou
gh

to
be bended and wrapped

in the void

around the
mobile

chassis

to overcome the antenna length
problem an
d make it fit inside the device so it
is
completely self
-
contained and does not need an
additional ground plane or any other components.
Thus, the new antenna can be mounted anywhere
inside or outside any handset because the antenna
does not use a part of the handset as an extended
ground plan
e as usually happens with internal
antennas.

Results:

Different

prototypes of the new LTE

antenna
s

have
been designed, manufactured and tested
.

The results
of a selected sample antenna configuration will be
presented
.

The low band antenna
performance
having total volume

of:
0.4x0.4x15.6 cm
=2.496 cm
3

is numerically calculated by a software packages that
uses the moment method. It is also measured at
IMST antenna labs in Germany
.
It should be noted
that

the

proposed volume

is the
total

volume of the
ante
nna because it does not require an additional
ground plane or matching
circuits.

The

agreement
between numerical and experimental results was
acceptable
.
Fig. 2 shows the calculated and
measured return loss of the low band antenna.
The
return loss is less
than
-
5 dB

almost
all over
the
frequency

band
from 698 MHz to 1.51 GHz

which is
73 % band width
.


Fig. 2

Calculated & measured return loss of the low
band antenna

T
he

total

antenna efficiency

is

shown in

Fig.3
.
The
average efficiency is better than 70%

over most of
the low band
.

Fig.4

demonstrates the peak gain o
f
the low band antenna

which is higher than 1 dB
almost over the whole band
.
Fig.5

shows the total
radiation pattern

at
a sample frequency
748
MHz.


Fig.3

Efficiency of the low band antenna

Long Arm

T

Shorting Strip

Short Arm

Slots

W
2

L
1

D
1

D
2

D
3

D
4

D
5

D
6

D
7

D
8

W
1

L
2


Fig.4

Gain

of the low band antenna


Fig.5

Radiation pattern of the low band antenna

at
748 MHz

To cover the high band
portion of the LTE
spectrum,
a second antenna has been
designed

and

manufactured

by scaling and optimizing the
geometry shown in Fig. 1,

having total volume

of

0.4x0.4x5.55 cm
=0.888 cm
3

without any additional
ground

planes
or tuning circuits
. The antenna is
tested all over the high frequency band 1.71
-
3.8
GHz
.
As shown in Fig.6, most of the

calculated and
measured return loss of the
high

ba
nd antenna lay
under
-
5 dB
resulting in
75.8%

antenna bandwidth
.


Fig.6

Calculated & measured return loss of the high
band antenna

Fig.7

shows that the efficiency of this novel antenna
is
above 80% over most of the high band

and
exceeds 95% at some frequency points
.

The
biggest

portion of the band
meets

a
peak gain above 1 dB
as

demonstrated in Fig.8
. The
total radiation pattern at

sample frequency

2.755 GHz is shown in Fig.9
.


Fig.7

Efficiency of the high band antenna

M
ultiples of
low and high band antennas

can be
used
for MIMO diversity in laptop
s, tablets and smart
phones.
E
ach of
these

different situations has been
studied
and will be demonstrated next.


Fig.8

Gain of the high band antenna


Fig.9

Radiation pattern of the high band antenna

at
2.755 GHz

Laptops and tablets:

The space available inside laptops and tablets is
quite

large, so
for
2x2

MIMO
diversity,
one
primary

antenna

&
one
diversity antennas can be placed

10
cm apart perpendicular to each other
. As a result

of
this
position of
primary & diversity

antennas

relative
to each other
,

even though they are
broadcasting
over the same frequency band in the same time,

the
correlation coefficient

and isolation

betwee
n the two
antennas
will be

as good
as

expected
.
Shown

in
Fig.10,
the
maximum correlation coefficient value is
less than 0.025
.
Also the calculated isolation is less
than
-
20 dB and the measured isolation shows better
isolation values much less than
-
25 dB as
demonstrated

in Fig 11
.

Also the isolation between
the
primary & diversity
antennas is measured with
laptop and in free sp
ace with holding the same
position and space between
them
. T
he

measured

isolation

on laptop

gets

improved
over most of the
band

as demonstrated in Fig. 12
.


Fig. 10

Correlation coefficient between
primary and
diversity

low band
MIMO

antennas

perpendicular

to
each other

for laptop and tablets

Fig. 11

Measured & calculated isolation

(S21)

between
primary and diversity

low band MIMO

antennas

perpendicular for laptop and tablets


Fig.12

Measured isolation

(S21)

between
primary
and diversity

low band MIMO

antennas

perpendicular
on

laptop and
without laptop

The
primary & diversity

antennas are totally
uncorrelated
as previously
shown

and this can be
further
noticed

in Fig.13 & Fig.14

as the total
radiation patterns

of

the primary and diversity
antennas

are
uncorrelated both at phi=0 & phi=90
as
shown at
a
sample frequency 901
MHz .


Fig.13

uncorrelated patterns
of
primary and diversity
antenna
s

at phi=0 at 901 MHz



Fig.14

uncorrelated patterns
of
primary and diversity
antenna
s

at phi=
9
0 at 901 MHz

The previous experiments
are repeated

for 2x2
MIMO high band antennas perpendicular

to each
other

and 10 cm apart for laptops and tablets.

In terms of wavelength
,

the distance between the
primary and diversity antennas is large
r

in the high
band which is reflected in a positive way on
correlation coefficient

values
which are
much less
than 0.001
as shown in Fig. 15.
Also
lower
Isolation
than
-
30 dB in free space and on laptop
is shown in

Fig. 16

& Fig. 1
7
.



Fig. 15

Correlation coefficient between
primary and
diversity high band

MIMO

antennas

perpendicular

to each other

for laptop and tablets


Fig. 16

Measured & calculated isolation

(S21)

between
primary and diversity high

band MIMO

antennas

perpendicular for laptop and tablets


Fig.17

Measured isolation

(S21)

between
primary
and diversity
low band MIMO

antennas

perpendicular
on

laptop and
without laptop

Also, the uncorrelated total radiation patterns
demonstrated in Fig. 18 & Fig. 19 is a f
urther
evidence of the minimal correlation between primary
and secondary high band MIMO antennas on laptops
and tablets.

Low band & high band antennas isolation

The ultra wide spectrum of LTE requires the
presence of both of the low band & high band in the

device in the same time to cover the whole spectrum.
This condition will raise concerns about isolation
between high & low bands.


We’ve investigated the worst case scenarios for the
presence of low & high band antennas together in
laptops and tablets and

found that the isolation in
different relative positions is acceptable.


Fig.18

uncorrelated patterns of primary and diversity
antennas at phi=0 at 2.755 GHz



Fig.19

uncorrelated patterns of primary and diversity
antennas at phi=0 at 2.755 GHz

The firs
t case

scenario

investigated
was
the low band
antenna parallel to the high band antenna at 10 cm
distance between them
.

As
shown in Fig. 20

& Fig.
21
, the isolation all

over both low and high
bands
is

lower than
-
30 dB
.


Fig. 20

Measured &

calculated isolation (S21)

in
low frequency band between low band and high
band antennas while parallel to each other


Fig. 21

Measured & calculated isolation (S21) in
high frequency band between low band and high
band antennas while parallel to each ot
her

When the isolation
between

low & high band
antennas has been
investigated

experimentally

for

laptop

case study
, it also demonstrated very good
isolation values lower than
-
30 dB

for free space &
-
40 dB

for laptop over most of the low and high
bands

as shown in Fig. 22 & Fig. 23

respectively
.


Fig. 22

Measured isolation (S21) in low frequency
band
between
low band and high band
while parallel
to each other on laptop


Fig. 23

Measured isolation (S21) in low frequency
band
between
low band and high b
and while parallel
to each other on laptop.

The second case

scenario

that has been studied was

the low band and high band antennas perpendicular
to each other and 10 cm
apart. T
he results
demonstrated in
Fig. 24 & Fig. 25

shows
lower than
-
40 dB isolation
over almost the whole frequency
band
.

The experimental
comparisons between
isolation
in free space & on

laptop are

also shown in
Fig. 26 & Fig. 27
.



Fig. 24

Measured & calculated isolation (S21) in
low frequency band between low band and high
band antenn
as while
perpendicular

to each other



Fig. 25

Measured & calculated isolation (S21) in
high frequency band between low band and high
band antennas while perpendicular

to each other
.

Smart phones:

The low band antenna
can be

customized
for smart
phones. It can be bent as an

L


shape to fit in the
void around the chassis of the handset
.
This
customization has been
studied theoretically and
experimentally

for 2x2 MIMO

and the results will be
discussed

below
.




Fig. 26

Measured isolation (S21) in low frequency
band
between
low band and high band while
perpendicular to each other on laptop



Fig. 27

Measured isolation (S21) in high frequency
band
between
low band and high band while
perpendicular to each other on laptop
.

As shown in Fig. 28
,
low band antenna
lapelled
no.
1 is the primary antenna and the other low band
antenna

lapelled

no.2 is the diversity antenna. The
primary and diversity antennas are wrapped in “L”
shape configuration to
overcome

the
extra

length
problem of the low band

antenna.
The measured &
calculated return loss
of both antennas

is lower than
-
5
dB over most of the low band fro
m 698 MHz to
1.51 GHz

for
both primary and diversity antennas

as

demonstrated in
Fig.29 & Fig.30

respectively
.









Fig.
28

The schematic diagram of MIMO low band
antennas on mobile


Fig.29

Calculated & measured return loss of the
primary low band antenna

Fig.30

Calculated & measured return loss of the
diversity low band antenna

T
he primary

& diversity

antenna
’s efficiencies are
higher than 60% & 50% respectively over most of
the low band as
demonstrate
in Fig. 31.

Also a peak
gain higher than 1 dB over most of the band for both
the primary & diversity antennas
shown
in

Fig.
32.

Fig. 31

Eff
i
ciency of primary & diversity
low band
antennas


Fig. 32

Gain

of primary & diversity
low band
antennas

The isolation between
the primary and diversity
antennas has been investigated and
a
lower than
-
10
dB measured isolation

in free space

can be

accepted

as shown in Fig. 33.
Demonstrated in Fig. 34, the

measured isolation on mobil
e was much promising
over most o
f the
band,

as
it has average of
-
15 dB
.

2

1

Fig. 33

Measured & calculated isolation (S21)
between primary and diversity low band antennas


Fig. 34

Measured isolation (S21) between primary
and diversity low band antennas with & without
presence of mobile

The correlation coefficient between primary and
diversity antennas
was lower than 0.55
as shown in
Fig. 35
.


Fig.

35

Correlation coefficient betwee
n primary and
diversity low band antennas

As proven in Fig.

36 & 37, the

low correlation
values over the low
frequency
band is an indication
of
uncorrelated radiation patterns of primary and
diversity antennas relative to each other

at both
phi=0 and phi=90 at sample frequency 901 MHz.

Fig. 36
uncorrelated patterns of primary and
diversity antennas at phi=0 at 901 MHz


Fig. 37 uncorrelated patterns of primary and
diversity antennas at phi=90 at 901 MHz

2x2 MIMO
high band antennas hav
e been also tested
theoretically and experimentally and their relative
position to e
ach other has been optimized
for the
implementation in smart phones. The
best results
were

due to the position shown in Fig.
38
, where
antenna lapelled no.1 is the primary

and antenna
lapelled no.2 is the
diversity.











Fig. 38 The schematic diagram of 2x2 MIMO high
band antennas on mobile

Measured i
solation

(S21)

of
as low as

-
30 dB

between
primary & diversity

MIMO
antennas
shown
in Fig. 39

& Fig.
40, is

a
n expected

result

of the

perpendicular position
of primary

antenna

relative to
diversity
antenna

which
is

considered

the best
isolation technique in such a small available space
inside handsets.


Fig. 39 Measured &

calculated isolation (S21)
between primary and diversity
high

band antennas


Fig. 40 Measured isolation (S21) between primary
and diversity high band antennas
in free space & on
mobile

The perpendicular relative position
also has
its
positive effect on the
correlation coefficient

which is

generally

lower than 0.1

and most of the high
frequency band is lower than 0.01

as shown in Fig.
41
.


Fig. 41
Correlation coefficient between
primary and
diversity high band

MIMO

antennas

perpendicul
ar

to each other for smart phones

The
resulted
uncorrelated pattern
s

of the primary &
diversity antenna
are

demonstrated at phi=0 &
phi=90
at sample frequency 2.755 GHz
in Fig. 42 &
43 respectively.

1

2


Fig. 42 uncorrelated patterns of primary and
diversity
antennas at phi=0 at 2.755 GHz


Fig. 43 uncorrelated patterns of primary and
diversity antennas at phi=90 at 2.755 GHz

The urgent demand for universal LTE smart
phones

requires an antenna solution that is able to cover
most of LTE bands for global roaming
. By
combining our two wide band antennas
together in
one
device, it
will
fulfill

that

need
.
A schematic
diagram
for our

MIMO wide band antenna solution
is demonstrated in Fig. 44

As shown in Fig. 44 the high band antennas no. 3 &
4 are located in a higher

plane above the low band
antennas by 1 mm
.













Fig. 44
The schematic diagram
of MIMO wide band

antenna

solution for
LTE smart phones

The biggest concern
in this case is the isolation
values between

the low and high band antennas. The
isolation is tested for this case and
results were

mostly

lower
-
20 dB for
low band and high band
frequency spectrum

as

shown in Fig. 45 & Fig 46

respectively
.


Fig. 45
isolation between each low band and high
band
antenna in the low band frequency spectrum

1

2

3

4


Fig. 46 isolation between each low band and high
band antenna in the high band frequency spectrum

Dual feed antenna

In some cases the available space inside handsets is
very limited
and the number of MIMO antenn
as will
represent a problem. We have developed another
wide band LTE antenna solution for handsets that
will save large volume inside the device by dual feed
technique in one antenna, so the multiband LTE can
be covered only by two antennas as shown in Fig
.
47
.










Fig. 47

The schematic diagram for MIMO
dual feed
LTE antennas

The
first antenna in this solution is the low band
antenna; it is a dual feed for
2x2
MIMO diversity
purpose
. The dual feeds are lapelled 1 & 2
in

Fig.
48
.










Fig. 48

The schematic diagram of MIMO low band
antenna solution for LTE smart phones

The low band dual feed antenna has been t
ested for
obtaining return loss
due to the first feed S11 , return
loss due to second feed S22
and the isolation

between

them

S21

as shown in Fig. 49
.


Fig. 49

s parameters for
dual feed low band antenna

The resulted correlation coefficient between the two
feeds is lower than 0.5 for the low band antenna as
shown in
Fig.
50
.

1

2


Fig. 50

Correlation coefficient betwee
n feed 1 &
feed 2
for low band antenna

The second antenna in the wide band LTE antenna
solution for the
handsets

is the high band antenna
which is also
having dual feeds
for 2x2 MIMO
diversity
. The 2 feeds lapelled 1 & 2 are shown in
Fig.
51
.










Fig. 51

The schematic diagram of MIMO
high

band
antenna solution for LTE smart phones

The high band dual feed antenna has been tested for
obtaining return loss due to the first feed S11 , return
loss due to second feed S22 and the isolation
bet
ween them S21 as shown in Fig.
52
.

The resulted correlation coefficient between the two
feeds is lower than 0.6 for the low
band antenna as
shown in Fig. 53
.




Fig. 52

s parameters for dual feed high band antenna


Fig. 53

Correlation coefficient between feed 1 &
feed 2 for
high

band antenna

Improving LTE antenna
performance

As
sh
own above, our wide band

antenna

can cover
most of the LTE frequency spectrum
. However, the
small space available
for the antenna inside the
devic
e
s makes it a compromise process:

To fit
the
antenna
inside such
small space makes
us

accept
lower

but acceptable

efficien
cies.
A
s the available
space

is larger it would be
desirable &
easy to
increase the efficiency
by increasing the width and
thickness of the antenna as much as possible. A new
antenna has been developed for this purpose
having
a total volume of 1.3x0.4 x14.5=7.54 cm
3
.
Fig. 54

shows the return los
s of the increased size antenna,
which is lower than
-
8

dB over most of the band
1

2

having minimum value of
-
5dB.

The total efficiency
shown in
Fig. 54
demonstrates minimum efficiency
of 70% and reaches its maximum at
96%.

The
average

gain of the newly developed antenna is
higher than 1dB

as shown in Fig. 56
. The
radiation
patterns at phi=0 & phi=90

at 901 MHz

are also
demonstrated
in Fig. 57
.


Fig. 54

Improved
Return loss (S11) of
the increased
size antenna


Fig. 55

Improved efficiency of the increased size
antenna


Fig. 56

Improved gain of the increased size antenna


Fig.
57 Radiation

pattern

of the increased size
antenna

at 901 M
Hz

References:

[1]

“LTE
:

The Future of Mobile Broadband
Technology”
,
Verizon wireless
.

[2]

P. Vainikainen, J. Holopainen, C. Icheln, O.
Kivekas
, M. Kyro, M. Mustonen, S. Ranvier, R.
Valkonen, and J. Villanen, “More than 20 antenna
elements in future mobile phones, threat or
opportunity?”,

Antennas and Propagation, 2009,
EuCAP 2009.
3
rd


European Conference on 23
-
27
March 2009, pp. 2940
-
2943.

[3]

Byoung
-
Nam Kim, Seong
-
Ook Park, Jung
-
Keun
Oh, and Gwan
-
Young Koo
, “
Wideband Built
-
In
Antenna
with

New

Crossed C
-
Shaped Coupling
Feed for

Future Mobile Phone Application

,

IEEE

antennas and wireless propagation letters, vol. 9,
pp.
572
-
575 ,
2010
.

[4]
http://www.wirelessintelligence.com/analysis/201
1/12/global
-
lte
-
network
-
forecasts
-
and
-
assumptions
-
one
-
year
-
on/

[5]
“Next Generation

Mobile Networks

Initial
Terminal Device De
f
inition”, NGMN Alliance,
November
,

2010
.

[6]
http://www.gl
obaltelecomsbusiness.com/Article
/2948514/Sectors/25196/38
-
fragmented
-
frequencies
-
confuse
-
scale
-
benefits
-
of
-
LTE
-
terminals.html

[7]

http://mobiledevd
esign.com/tutorials/4g
-
devices
-
demand
-
active
-
antenna
-
solutions
-
0216/?cid=ed