An Introduction to Signal Boosters

1
An Introduction to Signal Boosters
800 MHz Signal Booster
UHF Signal Booster
2
Outline

• History and examples
• Types of Signal Boosters
• Class A amplifier characteristics
• Building a Signal Booster
• Sample applications
• System design using spreadsheet analysis
• Limitations
• Summary

3
An Introduction to Signal Boosters

• Problem Lack of coverage or poor coverage due to
  a shielded environment
• Solution Amplified distribution system

4
Applications

• Best application for an amplified distribution
  system an adequate signal would be received if
  it werent for severe shielding. (very high
  abrupt path loss)

5
Components of Amplified Distribution System

• Antennas
• Leaky cable
• Signal Booster
• Power dividers
• Directional couplers
• Transmission line

6
Signal Booster Aliases

• Repeater Amplifier
• Bi-Directional Amplifier (BDA)
• Repeater
• On Channel Repeater (OCR)
• On Frequency Repeater (OFR)

7
History

• First Signal Booster designed, manufactured, and
  deployed in 1979
• Joint venture, Motorola and TX RX Systems
• UHF system for a coal mine in Illinois
• Leaky cable system using cascaded amplifiers

8
Examples of Major Projects

• King Fahd Airport
• Chunnel
• South Texas Nuclear Plant
• Brunei Palace
• Los Angeles Transit
• Cook County Correctional

9
Example Applications

• Hospitals
• Nuclear power plants
• Tunnels
• Shopping malls
• Correctional facilities
• Airports
• Mines

10
Standard Models Available

• 132-940 MHz range
• Both one-way and two-way
• From 30 dB to 80 dB gain
• Various bandwidths, from less than 1.0 MHz to 18
  MHz (including NPSPAC only)
• Mechanical options include stainless steel and
  painted steel enclosures as well as 19 rack
  mount versions

11
Types of Signal Boosters

• Broadband
• amplify frequency band segments
• no frequency conversion
• minimal group delay (nanoseconds)
• class A amplifiers

12
Types of Signal Boosters
Sean Johnson Ernie, please confirm accuracy

• Channelized
• amplify discrete frequency
• frequency is down converted to 10.7 MHz and
  sharply filtered
• adjacent channel rejection (gt60 dB)
• can be combined for multiple channel use
• power amps can be class C
• greater output power
• linearity not an issue due to single frequency
  amplification

13
Quick Class A Lesson
Sean Johnson Ernie, please confirm accuracy

• Transistor power spec is one dB compression point
• this level is never reached due to IM concerns
• Useable output power is a function of 3rd order
  intercept point
• two carrier test determines maximum output
• Useable output power decreases (per carrier) as
  number of carriers in the passband (at similar
  power levels) increases
• Carriers gt15dBc from strongest do not affect
  output level

14
Output Level Control (OLC)

• Controls IM output levels
• Control range is 35-40 dB
• Reduces risk of power amp damage

Sean Johnson Ernie, please confirm accuracy
15
Two Carrier IM Test

• Two carriers at 27 dBm each
• Third order products are down at least 41.84 dBc

Signal Booster output response
27.00 dBm
43 10 log (power) -13 dBm
-14.84dBm
Sean Johnson Ernie, please confirm accuracy
16
Six Carrier IM Test with OLC
Sean Johnson Ernie, please confirm accuracy

• Number of carriers increased to six
• same input levels as previous test
• Output level decreases to 22 dBm per carrier
• OLC maintains exactly the same IM level as the
  two carrier test

Signal Booster output response
22.00 dBm
43 10 log (power) -13 dBm
-14.84 dBm
17
Six Carrier IM Test without OLC
Sean Johnson Ernie, please confirm accuracy
26.00 dBm

• OLC turned off
• IM is 22.67 dBc (down from carrier) or 3
  dBm
• IM products increasing at 31 (vs. carrier)

Signal Booster output response
43 10 log (power) -13 dBm
3.33 dBm
18
Gain Block
.4 watt low level preamps
19
Gain Block with High Level Amps
6w
3w
Power amps increase Signal Booster output level
capability by approximately 200
20
Gain Block with High Level Ampsand Output Level
Control
OLC controls IM output level and minimizes risk
of power amp damage
21
One-Way Signal Booster
Preselector reduces number of frequencies to be
amplified, thus maximizing output level of
desired channels
22
Two-Way Signal Booster
23
In-building Application
Two-Way
8
0
0

M
H
z
Repeater
A
n
t
e
n
n
a
Amplifier
E
l
e
v
a
t
o
r

S
h
a
f
t
Yagi
Antenna
RF
Top Floor Signal Distribution System
Decoupler
Omnidirectional
Antenna
4-Way
Divider
Low-Loss Coaxial Cable
50
Ohm
T
o

L
o
w
e
r
F
l
o
o
r
s
Radiating Coaxial Cable
24
Tunnel Application
UHF
Antenna
A
1


H
i
g
h
-
G
a
i
n

U
H
F

H
e
a
d
-
E
n
d

A
m
p
l
i
f
i
e
r
A
2
,

A
3


L
o
w
-
G
a
i
n


U
H
F

L
i
n
e

A
m
p
l
i
f
i
e
r
s
Two-Way
Low-Loss
Repeater
Coaxial
Amplifier
Cable
50
Ohm
Radiating Coaxial Cable
A3
A2
533m
533m
533m
A1
25
Shadowed Area Application
N
e
a
r
A
n
t
e
n
n
a
Two-Way
Repeater
Amplifier
F
a
r
A
n
t
e
n
n
a
High Terrain
or Man-Made
Structure
S
h
a
d
o
w
e
d
(
O
b
s
t
r
u
c
t
e
d
)
A
r
e
a
26
Spreadsheet Analysis
External path loss
Two-Way
Repeater
8
0
0

M
H
z
Amplifier
Base to downlink amplifier analysis TX output
to signal booster output
A
n
t
e
n
n
a
Distribution system
Internal path loss
D
Base Tx
U
P
Base Rx
portable
27
Spreadsheet Analysis
28
Spreadsheet Analysis
External path loss
Two-Way
Repeater
8
0
0

M
H
z
Amplifier
A
n
t
e
n
n
a
Downlink amplifier to portable analysis signal
booster output to portable input
Distribution system
Internal path loss
D
Base Tx
U
P
Base Rx
portable
29
Spreadsheet Analysis
30
Spreadsheet Analysis
External path loss
Two-Way
Repeater
8
0
0

M
H
z
Amplifier
A
n
t
e
n
n
a
Portable to uplink amplifier analysis portable
output signal booster output
Distribution system
Internal path loss
D
Base Tx
U
P
Base Rx
portable
31
Spreadsheet Analysis
32
Spreadsheet Analysis
External path loss
Two-Way
Repeater
8
0
0

M
H
z
Amplifier
A
n
t
e
n
n
a
Uplink amplifier to base analysis signal
booster output to RX input
Distribution system
Internal path loss
D
Base Tx
U
P
Base Rx
portable
33
Spreadsheet Analysis
34
Limitations
Sean Johnson Ernie, please confirm accuracy

• Antenna isolation must be 20 dB greater than
  Signal Booster gain
• Signal Boosters are low power and are not meant
  to replace repeaters or base stations
• Signal Booster input levels should be -70 dBm or
  greater
• Guard band should be greater than the band width

35
OLC Demo - System Balance
36
OLC Voltage Matrix
37
OLC Demo - System Balance

• Weak signal received from portable B
• OLC not active

Portable B
OLC voltage
38
OLC Demo - System Balance

• Strong signal received from portable A
• OLC activates and reduces gain
• Weak signal from portable B disappears

Portable A
Portable B
OLC voltage
39
OLC Demo - IM Control
40
OLC Demo - IM Control

• Both portables keyed
• OLC not active
• 3rd order IM within spec

Portable A
Portable B
2B-A
2A-B
OLC voltage
41
OLC Demo - IM Control

• Increased input signal level activates OLC
• Carriers and IM levels controlled

Portable A
Portable B
2B-A
2A-B
OLC voltage
42
OLC Demo - IM Control

• OLC bypassed
• IM increasing at 31 vs. carrier

Portable A
Portable B
2A-B
2B-A
3B-2A
OLC bypassed
OLC voltage
OLC bypassed
43
OLC Demo - IM Control

• OLC re-activated
• IM levels drop dramatically

Portable A
Portable B
2B-A
2A-B
OLC voltage
44
Summary

• Amplified distribution systems are a cost
  effective solution for coverage problems
• Each application must be analyzed which includes
  spreadsheet analysis and a site survey

45
Questions?