Ministry of Higher Education &Scientific Research
Al-Nahrain University
College of Engineering
Biomedical Engineering Department
GSM SIGNAL BOOSTER
A Graduation Project is submitted to the Biomedical Engineering Department
in Partial Fulfillment of the Requirements for the Degree of Bachelor of
Science in Biomedical Engineering
By
Ahmed Zeyad Qasim
Ramadan 1442
May 2021
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ACKNOWLEDGMENTS
Nowadays the Internet has become an insignificant part of human daily life. Most
businesses need the Internet in various fields of science, education, health and so
on. With the advent of time, the quality of the Internet has become faster and better
and the capacity of the Internet has increased with reaching fifth generation of
mobile communications (5G) that provide 10Gbps. However, some areas are not
covered well these areas has suffered from low data rate, latency, slow messages
sending and receiving and slow internet browsing for multiple of reasons such as
distance from the cellular tower, building materials, tower load and etc. so for
these kind of areas Signal booster become one of suitable solutions to improve the
quality of service.
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ABSTRACT
A GSM mobile phone signal booster basically consists of a bidirectional amplifier
created to boost weak cell phone signals in remote or hard-to-reach areas. The
purpose of boosting signals is to promote clearer reception for cellular phone users
in difficult locations. It is meant to solve the problem of bad network in offices,
camps, recreational centers, homes and in vehicles. The device brings improved
network signal to a relatively poor network area. This work intends to develop a
device which can provide users with relatively high signal strength in a poor
network area and at a lower cost. This is done in order to provide them with
seamless, uninterrupted and reliable communication and in the final analysis, make
GSM network available everywhere irrespective of height, terrain and location. To
effect this, three major components are utilized, they include: an external antenna
to capture the weak signal, a signal amplifier to boost the captured signal and an
internal antenna to redistribute the signal for users around the area where enhanced
signal is required.
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TABLE OF CONTENTS
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CHAPTER ONE
INTRODUCTION
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Introduction
1.1 Statement of problems:
In the modern world the evolution of Wireless and Mobile communications gets a
lot of improvement with reaching 5G and WIFI 6 this evolution of techniques and
technology and improve infrastructure and spreading of cellular towers(Base
Station) helps to improve the quality of services and gets higher data rate with
upload and download speed, but even that there are areas suffering from weak
connection with base station, so for these kind of areas, we using Signal Booster to
solve the weak connection with base station and poor transfer data, noisy calls,
low download and upload speed. In this project we will discover how the signal
booster work and why it’s important to use this device in some spot. The figure
(1-1) shown how a Mobile repeater work.
Figure 1-1 How Mobile Repeater work.
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2 Motivation and Objectives:
After searching and see what the circuits are available to work on, we have focused
on circuit that has good amplifying to solve issues of weak signals for a reasonable
price, Therefore, the objectives of the research presented in this is can be
summarized as follows:
1- Build a circuit to boost weak signals.
2- Test the circuit then take notes and discuss the performance.
1.3 Evolution of Mobile Communications
Mobile communications systems revolutionized the way people communicate,
joining together communications and mobility. A long way in a remarkably short
time has been achieved in the history of wireless. Evolution of wireless access
technologies is about to reach its fifth generation internationally. Looking past,
wireless access technologies have followed different evolutionary paths aimed at
unified target: performance and efficiency in high mobile environment. The first
generation (1G) has fulfilled the basic mobile voice, while the second generation
(2G) has introduced capacity and coverage. This is followed by the third
generation (3G), which has quest for data at higher speeds to open the gates for
truly “mobile broadband” experience, that was realized by the fourth generation
(4G). The Fourth generation (4G) that provide access to wide range of
telecommunication services, including advanced mobile services, supported by
mobile and fixed networks, which are increasingly packet based, along with a
support for low to high mobility applications and wide range of data rates, in
accordance with service demands in multiuser environment.
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we are about reaching 5G that provide data rate up to 10 Gbps and offer low
latency about 1 millisecond of latency, and allow connect 100x of connected
devices per unit area (compared with 4G LTE). The figure below show the
evolution of mobile communications
Figure 2-1: The evolution of Mobile Communications
1.4 Global system for mobile communication (GSM)
Is a globally accepted standard for digital cellular communication. GSM is the
name of a standardization group established in 1982 to create a common European
mobile telephone standard that would formulate specifications for a pan-European
mobile cellular radio system operating at 900 MHz. It is estimated that many
countries outside of Europe will join the GSM partnership.
1.5 Signal Booster
A cell phone reception booster is generally a repeater system that involves the
mplifier adding gain or power to the reception in various directions. Even for a
cheap cell phone signal booster, maximum gain differs by application. The work of
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an outside antenna is to both receive and transmit signal to a cellular tower with
enhanced power and sensitivity. Usually the dB gain is never below 7 dB and can
be over 10 dB gain. The system's elements conduit is the coaxial cable. It is also a
factor in transmission loss.
1.6 Weak Signal
Poor cell phone signal is a very common problem: the majority of our customers
come to Waveform looking for a solution to their own, very specialized, cell signal
problems. A common situation is a home or office with few or no signal bars and
frequently dropped calls.
Repeater can help in this situation depends on the cause of the problem - which
you the customer can usually determine quite easily.
1.6.1 - Causes of Weak Signal
1. Distance from the cellular tower – weak downlink signal (tower to
phone) and weak uplink signal (phone to tower).
2. Building materials/vehicle construction – drywall, wood, concrete,
metal, and low-e glass can attenuate the signal.
3. Inter-cell interference or competing signals – if your phone is
located between two or more towers, the other signal towers will
interfere with the tower you are attempting to connect to,
causing a lower signal quality. This is usually measured by SINR
and RSRQ (Reference Signal Received Quality, measured in dB)
and is the most common type of weak signal seen in urban and
suburban areas.
4. Tower load.
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5. Geography and nearby buildings.
6. Weather - during weather conditions like rain, snow, and even dust storms. The
water or dust particles in the air deflect and break apart the radio signal, resulting
in a spotty or weak signal.
1.7 How does a signal booster work?
The Signal booster consists of:
1. Outdoor Antenna.
2. Indoor Antenna.
3. Amplifier.
The Signal Booster works by captured the weak signal that doesn’t reach well for
the client from the base station (Cellular Tower) this signal captured by outdoor
Antenna, then the amplifier boost this weak signal and broadcast the boosted
signal by Indoor Antenna, usually the performance of a signal booster is measured
by gain.
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CHAPTER TWO
THEORY
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2-1 Introduction
In this chapter we will look on Radio frequency (RF), and why GSM is used in
UHF range and frequency bands that used in GSM systems then take a deep look
on GSM Technology, Types and the architecture of a GSM system.
2-2 Radio frequency (RF)
is the oscillation rate of an alternating electric current or voltage or of a magnetic,
electric or electromagnetic field or mechanical system in the frequency range from
around 30 kHz to around 300GHz. This is roughly between the upper limit of
audio frequencies and the lower limit of infrared frequencies; these are the
frequencies at which energy from an oscillating current can radiate off a conductor
into space as radio waves. Different sources specify different upper and lower
bounds for the frequency range. The Radio Frequency bands are shown in
table (1-2).
Name Frequency Range Applications
Low Frequency (LF) 30KHz – 300KHz Time standards, Navigstion
Medium Frequency (MF) 300KHz – 3MHz AM radio
High Frequency (HF) 3MHz - 30MHz Amateur radio
Very High Frequency 30MHz - 300MHz FM/TV broadcasting
(VHF)
Ultra-High Frequency 300MHz - 3GHz Cell phones, WLAN, GRP
Frequency
Super-High Frequency (SHF) 3GHz – 30GHz Satellite, 5G mobile
Extremely High Frequency (EHF) 30GHz – 300GHz Imaging / detection
applications, 5G Mobile
Tremendously High Frequency 300GHz – 3THz High resolution microwave
(THF) imaging
Table 1-2: Radio Frequency bands:
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GSM Technology use UHF frequency range for downlink and uplink.
2-2-1 GSM Frequency Bands
GSM Frequency Bands of Frequency Range is the frequency for the operation of
GSM mobile phones. GSM frequency bands are shown in Table (2-2).
Uplink (MHz) Downlink (MHz)
GSM band ƒ (MHz) Channel numbers
(mobile to base) (base to mobile)
T-GSM-380[a] 380 380.2 – 389.8 390.2 – 399.8 dynamic
T-GSM-410[a] 410 410.2 – 419.8 420.2 – 429.8 dynamic
GSM-710 710 698.2 – 716.2 728.2 – 746.2 dynamic
T-GSM-810[a] 810 806.2 – 821.2 851.2 – 866.2 dynamic
T-GSM-900[a] 900 870.4 – 876.0 915.4 – 921.0 dynamic
R-GSM-900[h] 900 876.0 – 915.0 921.0 – 960.0 0–124, 955–1023
E-GSM-900[e] 900 880.0 – 915.0 925.0 – 960.0 0–124, 975–1023
P-GSM-900[d] 900 890.0 – 915.0 935.0 – 960.0 1–124
GSM-850 850 824.2 – 848.8 869.2 – 893.8 128–251
GSM-480 480 479.0 – 486.0 489.0 – 496.0 306–340
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Uplink (MHz) Downlink (MHz)
GSM band ƒ (MHz) Channel numbers
(mobile to base) (base to mobile)
GSM-750 750 777.2 – 792.2 747.2 – 762.2 438–511
PCS-1900[j] 1900 1850.2 – 1909.8 1930.2 – 1989.8 512–810
DCS-1800[i] 1800 1710.2 – 1784.8 1805.2 – 1879.8 512–885
Table (2-2) GSM frequency bands
2-3 GSM Technology
Technology used for transmitting mobile voice and data services. GSM differs
from first generation wireless systems in that it uses digital technology and Time
Division Multiple Access (TDMA) transmission methods. GSM is a circuit-
switched system that divides each 200kHz channel into eight 25kHz time-slots.
GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and
850MHz bands in the US. The 850MHz band is also used for GSM and 3GSM in
Australia, Canada and many South American countries. GSM supports data
transfer speeds of up to 9.6 kbit/s, allowing the transmission of basic data services
such as SMS (Short Message Service). Another major benefit is its international
roaming capability, allowing users to access the same services when travelling
abroad as at home. This gives consumers seamless and same number connectivity
in more than 210 countries. GSM satellite roaming has also extended service
access to areas where terrestrial coverage is not available.
Global System for Mobile Communications. The first European digital standard,
developed to establish cellular compatibility throughout Europe. It's success has
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spread to all parts of the world and over 80 GSM networks are now operational. It
operates at 900 MHz.
2-3-1 GSM-900 and GSM-1800
GSM-900 and GSM-1800 are used in most parts of the world.
• GSM-900 uses 890 - 915 MHz to send information from the Mobile Station to
the Base Transceiver Station (uplink) and 935 - 960 MHz for the other direction
(downlink), providing 124 RF channels (channel numbers 1 to 124) spaced at 200
kHz. Duplex spacing of 45 MHz is used. In some countries the GSM-900 band has
been extended to cover a larger frequency range. This 'extended GSM', E-GSM,
uses frequency range 880 - 915 MHz (uplink) and 925 - 960 MHz (downlink),
adding 50 channels (channel numbers 975 to 1023 and 0) to the original GSM-900
band. The GSM specifications also describe 'railways GSM', GSM-R, which uses
frequency range 876 - 915 MHz (uplink) and 921 - 960 MHz (downlink). Channel
numbers 955 to 1023. GSM-R provides additional channels and specialized
services for use by railway personnel. All these variants are included in the GSM-
900 specification.
• GSM-1800 uses 1710 - 1785 MHz to send information from the Mobile Station
to the Base Transceiver Station (uplink) and 1805 - 1880 MHz for the other
direction (downlink), providing 374 channels (channel numbers 512 to 885).
Duplex spacing is 95 MHz.
GSM-1800 is also called PCS in Hong Kong and the United Kingdom. Most of the
GSM operators in India use the 900 MHz band. Operators like Hutch, Airtel, Idea,
and some others, use 900MHz in rural areas and 1800MHz in urban areas.
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• GSM-850
GSM-850 and GSM-1900 are used in the United States, Canada, and many other
countries in the Americas. GSM-850 is also sometimes erroneously called GSM-
800. In Australia, GSM 850 is the frequency allocated to Telstra's NextG Network
which was switched on in October 2006. The NextG Network is a step up from the
3G Network and is available at faster speeds Australia wide compared to the 3G
Network which is limited to only major population centres.
• GSM-850 uses 824 - 849 MHz to send information from the Mobile Station to
the Base Transceiver Station (uplink) and 869 - 894 MHz for the other direction
(downlink). Channel numbers 128 to 251.
Cellular is the term used to describe the 850 MHz band, as the original analog
cellular mobile communication system was allocated in this spectrum. Providers
commonly operate in one or both frequency ranges. The method chosen by GSM is
a combination of Time- and Frequency-Division Multiple Access
(TDMA/FDMA). The FDMA part involves the division by frequency of the
(maximum) 25 MHz bandwidth into 124 carrier frequencies spaced 200 kHz apart.
One or more carrier frequencies are assigned to each base station. Each of these
carrier frequencies is then divided in time, using a TDMA scheme. The
fundamental unit of time in this TDMA scheme is called a burst period and it lasts
15/26 ms (or approx. 0.577 ms). Eight burst periods are grouped into a TDMA
frame (120/26 ms, or approx. 4.615 ms), which forms the basic unit for the
definition of logical channels. One physical channel is one burst period per TDMA
frame.
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2-3-2 The System Architecture of GSM: A Network of Cells
Like all modern mobile networks, GSM utilizes a cellular structure as illustrated in
Figure 2.1.
The basic idea of a cellular network is to partition the available frequency
range, to assign only parts of that frequency spectrum to any base transceiver
station, and to reduce the range of a base station in order to reuse the scarce
frequencies as often as possible. One of the major goals of network planning is to
reduce interference between different base stations.
Anyone who starts thinking about possible alternatives should be
reminded that current mobile networks operate in frequency ranges where
attenuation is substantial. In particular, for mobile stations with low power
emission, only small distances (less than 5 km) to a base station are feasible.
Besides the advantage of reusing frequencies, a cellular network also
comes with the following disadvantages:
• An increasing number of base stations increases the cost of infrastructure
and access lines.
• All cellular networks require that, as the mobile station moves, an active
call is handed over from one cell to another, a process known as handover.
Figure1-2: The radio coverage of an area by signal cells.
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• The network has to be kept informed of the approximate location of the
mobile station, even without a call in progress, to be able to deliver an
incoming call to that mobile station.
• The second and third items require extensive communication between the
mobile station and the network, as well as between the various net-work
elements. That communication is referred to as signaling and goes far
beyond the extent of signaling that fixed networks use. The extension of
communications requires a cellular network to be of modular or hierarchical
structure. A single central computer could not process the amount of
information involved.
2-3-3 An Overview on the GSM Subsystems
A GSM network comprises several elements: the mobile station (MS), the
subscriber identity module (SIM), the base transceiver station (BTS), the base
station controller (BSC), the transcoding rate and adaptation unit (TRAU), the
mobile services switching center (MSC), the home location register (HLR), the
visitor location register (VLR), and the equipment identity register (EIR).
Together, they form a public land mobile network (PLMN). Figure 1.2 pro-vides
an overview of the GSM subsystems.
Figure2- 2: The architecture of a PLMN.
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1 Mobile Station
GSM-PLMN contains as many MSs as possible, available in various styles
and power classes. In particular, the handheld and portable sta-tions need to
be distinguished.
2 Subscriber Identity Module
GSM distinguishes between the identity of the subscriber and that of the
mobile equipment. The SIM determines the directory number and the calls
billed to a subscriber. The SIM is a database on the user side. Physically, it
consists of a chip, which the user must insert into the GSM telephone before
it can be used. To make its handling easier, the SIM has the format of a credit
card or is inserted as a plug-in SIM. The SIM communicates directly with the
VLR and indirectly with the HLR.
3 Base Transceiver Station
A large number of BTSs take care of the radio-related tasks and provide the
connectivity between the network and the mobile station via the Air-interface.
4 Base Station Controller
The BTSs of an area (e.g., the size of a medium-size town) are con-nected to
the BSC via an interface called the Abis-interface. The BSC takes care of all
the central functions and the control of the subsystem, referred to as the base
station subsystem (BSS). The BSS comprises the BSC itself and the
connected BTSs.
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5 Transcoding Rate and Adaptation Unit
One of the most important aspects of a mobile network is the effec-tiveness
with which it uses the available frequency resources. Effective-ness addresses
how many calls can be made by using a certain bandwidth, which in turn
translates into the necessity to compress data, at least over the Air-interface.
In a GSM system, data compression is performed in both the MS and the
TRAU. From the architecture perspective, the TRAU is part of the BSS. An
appropriate graphical representation of the TRAU is a black box or, more
symbolically, a clamp.
6 Mobile Services Switching Center
A large number of BSCs are connected to the MSC via the A-interface. The
MSC is very similar to a regular digital telephone exchange and is accessed
by external networks exactly the same way. The major tasks of an MSC are
the routing of incoming and outgoing calls and the assignment of user
channels on the A-interface.
7 Home Location Register
The MSC is only one subcenter of a GSM network. Another subcenter is the
HLR, a repository that stores the data of a large number of subscribers. An
HLR can be regarded as a large database that adminis-ters the data of literally
hundreds of thousands of subscribers. Every PLMN requires at least one
HLR.
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8 Visitor Location Register
The VLR was devised so that the HLR would not be overloaded with
inquiries on data about its subscribers. Like the HLR, a VLR contains
subscriber data, but only part of the data in the HLR and only while the
particular subscriber roams in the area for which the VLR is responsible.
When the subscriber moves out of the VLR area, the HLR requests removal
of the data related to a subscriber from the VLR. The geographic area of the
VLR consists of the total area covered by those BTSs that are related to the
MSCs for which the VLR provides its services.
9 Equipment Identity Register
The theft of GSM mobile telephones seems attractive, since the identities of
subscribers and their mobile equipment are separate. Stolen equipment can be
reused simply by using any valid SIM. Barring of a subscriber by the operator
does not bar the mobile equipment. To prevent that kind of misuse, every
GSM terminal equipment contains a unique identifier, the international
mobile equipment identity (IMEI). It lies within the realm of responsibilities
of a network opera-tor to equip the PLNM with an additional database, the
EIR, in which stolen equipment is registered and so can be used to bar
fraudulent calls and even, theoretically, to track down a thief (by analyzing
the related SIM data).
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CHAPTER THREE
DESIGN WITH
SIMULATION CELL
PHONE GSM MOBILE
SIGNAL BOOSTER
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3.1 Introduction
In this chapter we will look on the circuit design that used to boost the weak signal
by an amplifier, we will on the circuit design, tools and components that used in
this project. We used in this project:
• OP Amplifier (LM386).
• Resistors (25Ω, 50Ω, 4.7kΩ, 100kΩ).
• Capacitors (10μF ,100μF, 4700μF).
• Function Generator.
• Oscilloscope.
• DC Power Supply.
3.2 Primary System Model:
It has been started with simple amplifier to boost the weak signal, we investigate a
primary system model in order to improve such system later. The primary system
model is shown in figure (3-1).
Figure 1-3: The primary system mode
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3-2-1 OP AMP (LM386)
The LM386 is a power amplifier designed for use in low voltage consumer
applications. The gain is internally set to 20 to keep external part count low, but the
addition of an external resistor and capacitor between pins 1 and 8 will increase the
gain to any value from 20 to 200. The inputs are ground referenced while the
output automatically biases to one-half the supply voltage. The quiescent power
drain is only 24 milliwatts when operating from a 6V supply, making the LM386
ideal for battery operation. The LM386 is a Class AB Audio Amplifier IC that can
be used in a variety of applications. AM-FM radio amplifiers n, TV sound systems
Power converters, Portable stereos and computer speakers.
The features of this Amplifier is that has wide supply voltage 4V-12V or 5V-18V,
minimum external parts and Battery operation. The pinout diagram of LM386 is
shown in figure (1-3).
Figure 2-3: LM386 Pinout Diagram
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3-2-2 RF Antenna
The GSM booster design comprises of an indoor and outdoor antennas. The
outdoor antenna receives the weak GSM signal, while the indoor antenna
rebroadcast the boosted signal. For the outdoor antenna, a wide band directional
antenna operating at a frequency range of 700 to 2700 MHz was used. It has high
gain, wide bandwidth and it is weather resistant.
3.3 Implementation of improvement System Model
In this section, it has been implemented the improvement system model, the signal
booster now has an improvement, the circuit design gets improve, we have added
feedback to increase the gain and control on the gain, the circuit design of LM386
is shown in figure (3-3).
Figure 4-1: circuit design of LM386
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The signal booster now better boost and coverage more area.
The model now is specified for GSM frequency bands, Block diagram of the dual
bands (900 and 1800 MHz) GSM signal booster is shown in figure (4-3).
Figure 5- 3: Block diagram of the dual bands (900 and 1800 MHz) GSM signal booster
3-3-1 Function generator
A function generator is a signal source that has the capability of producing
different types of waveforms as its output signal. The most common output
waveforms are sine-waves, triangular waves, square waves, and sawtooth waves.
The frequencies of such waveforms may be adjusted from a fraction of a hertz to
several hundred kHz.
in this project we used function generator to test the LM386 IC to check the
amplifying of the IC by using Oscilloscope on the output.
3-3-2 Oscilloscope
The oscilloscope is an instrument that will display
alternating waveforms, appears on the oscilloscope with the indicated vertical and
horizontal sensitivities. The vertical sensitivity defines the voltage associated with
each vertical division of the display. Virtually all oscilloscope
screens are cut into a crosshatch pattern of lines separated by 1 cm in the
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vertical and horizontal directions. The horizontal sensitivity defines the
time period associated with each horizontal division of the display. as we written in
pervious section we used oscilloscope to see the boosted signal and check the
amplified signal if the signal get boosted, or has a distortion or not .
3-3-3 RF CIRCUIT DESIGN
This stage involves the use of an RF receiver and transmitter. The receiver receives
the weak signal, while the transmitter retransmits the boosted signal. Both circuits
were designed around a wideband Colpitts oscillator. The circuit design of this unit
is shown in figure (6-3)
Figure 6-3: Circuit diagram of the Colpitts oscillator
3-3-4 BAND PASS CIRCUIT DESIGN
The proposed GSM signal booster has the capability to boost both the 900 and
1800 MHz bands. This is because all the mobile networks in Nigeria operate
within these two bands. To achieve this, a band pass filter whose frequency
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response lies within these bands was used to pass signals in these bands and reject
other signals. The downlink frequency range (from base station to mobiles) of
network providers in Nigeria lie in the range 935 to 960 MHz for the 900 MHz
band and the range 1805 to 1880 MHz for the 1800 MHz band. Therefore, the first
bandpass filter design has a low frequency cutoff fl of 935 MHz and a high
frequency cutoff fh of 960MHz. Similarly, the 1800 MHz bandpass filter has
fl =1805MHz, and fh = 1880MHz. The circuit diagram of the bandpass filter is
as shown in Figure (7-3).
Figure 3-7: The circuit diagram of the bandpass filter
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