77393103 Microwave Link Design Sample

2

Introduction

Microwaves are generally describes as electromagnetic waves with frequencies

that range from approximately 500 MHz to 300 GHz or more. Therefore, microwaves

signals, because of their inherently high frequencies, have relatively short wavelengths,

hence the name” micro” waves. For example, a 100 GHz microwave signal has a

wavelength of 0.3 cm, whereas a 100 MHz commercial broadcast-band FM signal has a

wavelength of 3 m. the wavelengths for microwave frequencies fall between 1 cm and 60

cm, slightly longer than infrared energy. For full duplex (two-way) operation as is

generally required of microwave communications systems, each frequency band is

divided in half with the lower half identified as the low band and the upper half as the

high band. At any given radio station, transmitters are normally operating on either the

low or the high band, while receivers are operating on the other hand.

There are many different types of microwaves systems operating over distances that vary

from 15 miles to 4000 miles in length. Intrastate or feeder service microwave systems are

generally categorized as short haul because they are used to carry information for

relatively short distances, such as between cities within the same state. Long haul

microwaves systems are those used to carry information for relatively long distances,

such as interstate and backbone route applications. Microwave radio systems capacities

range from less than 12 voice-band channels to more than 22 000 channels. Early

microwaves systems carried frequency-division-multiplexed voice-band circuits and used

conventional, no coherent frequency modulation techniques. More recently developed

microwave systems carry pulse-code-modulated time-division-multiplexed voice-band

2

circuits and used more modern digital modulation techniques, such as Phase Shift Keying

(PSK) or Quadrature Amplitude Modulation (QAM).

Capabilities of Microwave

Microwave transmission is generally defined as the transmission of

electromagnetic waves whose frequency falls approximately in the range between 1

Gigahertz and 50 Gigahertz (wavelengths of 30 cm to 6 mm). The propagation through

the atmosphere of signals in this frequency range exhibits many of the properties of light,

such as line-of-sight transmission, reflection from smooth surfaces, etc. Microwave

systems have many applications in the telephone industry because high quality circuits

can be derived for intertoll trunks, toll connecting trunks, extended area service trunks,

subscriber service and special services. Microwave is also suitable for transmission of

black and white or color television, data, and data under voice, with negligible

impairment from impulse noise, delay distortion, frequency error, frequency response, or

steady state noise.

Another attractive aspect of microwave is the ease with which channels can be

added or removed after the basic radio frequency (RF) and carrier multiplex equipment is

installed. Certain types of RF equipment will carry up to 2000 or more voice channels

without any change in the basic RF equipment. The problems associated with cable

facilities such as physical damage, induction noise, right-of way problems, circuit

expansion limitations and similar problems are reduced with the use of microwave.

The initial cost of a microwave system depends on the type of radio frequency

and multiplex equipment used the number of channels, the number of hops in a system,

2

the terrain, the type of antennas, the cost of the necessary towers and other factors. In

some cases microwave will require a lower initial investment, provide greater reliability,

and have lower operating costs and maintenance than cable facilities.

It is highly desirable to use digital microwave equipment for all new installations

in order to eventually achieve a complete integrated digital network. The only exception

to this would be in the event that a borrower wants to use the microwave equipment to

carry television signals. Analog equipment is the best choice for the current standard

television channel.

The input and output baseband signal for a digital microwave radio is a single bit

stream. This may range from approximately 1.544 Mb/s to approximately 144 Mb/s. The

baseband signal is used to modulate a radio frequency carrier. The RF carriers used range

from 2 GHz to 24 GHz.

COMPONENTS OF A MICROWAVE SYSTEM

Transmitters and Receivers. The basic building blocks of a microwave system

are the radio frequency (RF) transmitters and receivers. These units make it possible to

send and receive information at microwave frequencies. Most microwave transmitters are

capable of an output power of one watt or more. A transmitter used in a terminal location

has provisions for modulating the RF carrier with baseband signals from the carrier

multiplex equipment. Receivers are capable of providing a useable baseband output with

received microwave signal levels as low as -80 dBm. A terminal receiver includes a

demodulator to provide the baseband output to the carrier multiplex.

2

Carrier Multiplex. The microwave RF equipment has a wide bandwidth which is

capable of carrying many channels of information. These channels are derived using

multiplex equipment which can combine several hundred channels for transmission over

one RF channel in a single bit stream.

Antennas. A parabolic or a horn antenna is used in microwave systems to

concentrate radiated energy into a narrow beam for transmission through the air. This

results in the most efficient transmission of radiated power with a minimum of

interference. An effective gain of 25 to 48 dB over an ommi-directional antenna is

possible depending upon the size of the antenna and the microwave frequency used.

Radomes. A radome is a protective covering used to prevent snow, ice, water, or

debris from accumulating on a microwave antenna. Heated radomes are available for use

in areas where severe ice and snow conditions exist. The use of a radome results in lower

antenna gain.

Transmission Lines. Transmission lines provide the means of coupling the

transmitter and receiver to the antenna. There are two types currently available:

waveguide and coaxial cable. The radiated output power of the transmitter will be

substantially reduced if the transmission line is incorrectly used or if its length is too

long, so precautions should be taken to use the correct type of line for the radio

equipment used, and to keep all transmission line lengths short.

Waveguide. A waveguide is a hollow metal duct which conducts electromagnetic

energy. This type of transmission line can be used for distances of a few feet up to several

hundred feet. A typical type of waveguide has a loss from about 1.7 dB per hundred feet

at 6 Gigahertz (GHz) to about 3.0 dB per hundred feet at 11 GHz. It is used at microwave

2

frequencies above 2 GHz and can have either a rectangular, elliptical, or circular cross-

section, depending upon the system operation requirements. The length of a waveguide

run is more critical at higher frequencies since attenuation increases with frequency. All

waveguide runs are pressurized.

Coaxial Cable. At low microwave frequencies, 2 Ghz or less, coaxial cable can

be used as the connecting facility between the transmitter, receiver and antenna instead of

waveguide. The loss of coaxial cable depends on the type of conductor, the cable

diameter, the type of dielectric, and the operating frequency. Coaxial cable with a

diameter of one inch or more should be used for long cable runs; 7/8" diameter coax can

be used satisfactorily for short runs. The coaxial cable can have either a pressurized air or

expanded polyethelyne (foam) dielectric between conductors, however, the air dielectric

coaxial cable has less attenuation for a given diameter. In general, pressurized air

dielectric coaxial cable is used with higher capacity systems because the return loss

characteristics of foam dielectric lines may be a significant distortion contributor in such

systems. This is not usually a consideration in systems of low channel capacity. The cost

of coaxial cable is less than waveguide and should be used when possible. Extreme

attenuation of radio signals above 2 GHz in the coaxial cable generally prohibits its use at

the higher microwave frequency bands.

Reflectors. A passive reflector can sometimes be used in systems operating near a

power substation to avoid the electromagnetic interference (EMI) potential in place of

using long runs of waveguide connected to a parabolic antenna at the top of the tower. A

reflector may be mounted at a 45 degree angle at the top of the tower, while the antenna

is mounted horizontally at the base of the tower, aimed at the reflector. The microwave

2

signal is radiated from the antenna, reflected off the reflector, and sent in a direction of

propagation to the other end of the radio path, just as though the antenna was radiating

directly from the top of the tower. However, this type "periscope" or "fly swatter"

antenna system will not be authorized by the FCC under ordinary circumstances because

of its interference potential with communications satellites. A waiver from the FCC is

required.

Towers. The towers used in microwave systems must be rigid to prevent antenna

deflection during wind or ice loading conditions. Guyed or self-supporting towers are

available for use on microwave systems. A guyed tower is about one-third the cost (per

foot, installed) of a self-supporting tower, but in some cases the difficulty of acquiring

enough land for guying prohibits the use of guyed towers.

The height of the tower is determined by the terrain, the microwave frequency band used,

the propagation characteristics, the distance between the transmitting and receiving ends

of a path, and the required reliability. The tower must be high enough to provide a line-

of-sight path above any obstructions. If reflection interference is a problem, the antenna

mounting heights are critical and the optimum height may be less than the maximum

height available on the tower.

Buildings. Microwave equipment should be located in the central office

equipment building when possible. There are some situations, however, when RF

equipment must be located remotely from a central office building, as in the case of an

active RF repeater. In these situations some type of building must usually be provided for

equipment protection. Usually a simple prefabricated building is sufficient. Where

temperature and humidity variations exceed the operating limits of the microwave

2

equipment, a heater or air conditioner is required to keep the equipment within its

operating temperature range.

Primary and Standby Power Equipment. Primary power sources for RF

equipment may be DC or AC as specified by the purchaser. Central office batteries or

117 volts AC commercial power may be used. In some cases, thermoelectric generators

or fuel cells can be used when the power requirements of the microwave equipment are

low. Standby power equipment should be provided at microwave terminals or active

repeater locations to maintain system operation in the event of a commercial power

failure. Communication circuits are very important during times of emergency such as

storms, floods and other disasters which may cause commercial power outages.

Therefore, it is imperative that some type of standby power source be available for

circuits derived by microwave. When microwave equipment is located in a central office

building, stand-by power is usually available from central office equipment batteries or

an engine-generator. However, at remote sites standby power must be provided

specifically for the microwave equipment. The stand-by power source may be batteries,

an engine-generator or in some cases a thermoelectric generator, fuel cell or solar energy.

Alarm Systems. When a microwave system has remote unattended stations, itis

desirable to have an alarm system which will report faults from the remote location to an

attended office via the microwave signal. These alarms will expedite the maintenance of

microwave systems and reduce the circuit outage time. Where alarms from a large

number of unattended stations are reported to a central maintenance control center,

2

consideration is often given to a computer-based alarm reporting system which prints out

all changes in status at each station with time and date information.

Definition of Terms

Absorption - the reduction in power density due to non-free space propagation.

Antenna - a metallic conductor system capable of radiating and capturing

electromagnetic energy.

Attenuation - the reciprocal of gain .The ratio of the input quantity to the output

quantity.

Azimuth- is the horizontal angular distance from a reference direction, either the

southern or northern most point of the horizontal.

Azimuth angle - the horizontal pointing angle of an earth station antenna.

Bandwidth- the maximum range of frequency, including guard bands, assigned to a

channel

Baseband- describes the modulating signal (intelligence) in a communication system. A

single message channel is baseband.

Characteristic Impedance of Free Space- is equal to the square root of the ratio of its

magnetic permeability to its electric permittivity.

Clutter Loss- attenuation due to trees and buildings in the front of the antenna be

propagated and back by the ionosphere.

Critical Angle- a maximum vertical angle of frequency at which it can be propagated

and still be refracted back by the ionosphere.

2

Critical Frequency- the highest frequency that can be propagated directly upward and

still be returned earth by the ionosphere.

dBm- used to reference the power level at a given point to one milliwatt.

Decibel (dB)- the basic yardstick used for making power measurements in

communications.

Diffraction - the modulation or redistribution of energy within a wave front when it

passes near the edge of an opaque object. It is the phenomenon that allows light or radio

waves to propagate (peek) around corners.

Digital Modulation- is the transmitted of digitally modulated analog signals (carriers)

between two or points in a communications system.

Direct waves- (see free space path)

Dispersive Fade Margin- gains in the equipment which are factored in because of

technical improvements on the system and how they improved the information signal

itself.

E- lines – European digital carrier system.

Fading- variations in the field strength of radio signal, usually gradual, that are caused by

changes in the transmission medium.

Field intensity - the intensity of the electric and magnetic fields of an electromagnetic

wave propagating in free space.

Flanges- interconnect parts of a microwave antenna system together.

Free Space Path- is the line of signal (LOS) path directly between transmit and receive

antennas (this is also called the direct waves).

2

Free Space Path Loss- the loss incurred by an electromagnetic wave as it propagates in a

straight line through vacuum with no absorption or reflection of energy by nearby

objects.

Frequency- the number of cycle computed per second by an alternating quantity, the

term usually used in describing frequency is cycle per second, on hertz.

Fresnel zones- described the amount of the front lobe power to the back lobe power of an

antenna.

Full Duplex (FDX)- (see duplexing).

Great Circle Distance- it is the shortest distance between any two points on a sphere.

Ground Wave - an electromagnetic wave that travels along the surface of earth.

Sometimes called “surface waves”.

Guard Band- a narrow frequency band provided between adjacent channels in certain

portions of the radio spectrum to prevent interference between stations.

Half Duplex- data transmission is possible in both directions but not at the same time.

K- Factor- the ratio of a hypothetical effective earth radius over 6370 km, which is the

true mean earth radius.

Maximum Usable Frequency (MUF)- the highest frequency that can be used for sky-

wave propagation between two specific points on earth’s surface.

Microwave communication- a high radio frequency link specifically designed to

provide signal connection between two specific points.

Polarization - orientation of the electric field vector in respect to the surface of the earth.

Power Density- the rate at which energy passes through a given surface area.

2

Radio Frequency (RF) Propagation- free-space propagation of electromagnetic waves.

Radio Horizon- the curvature of earth presents a horizon to space-wave propagation.

Receiver threshold - the minimum wide band carrier power (Cmin ) at the input to a

receiver that will provide a usable baseband output.

Reflection - the ability of electromagnetic transmission to bounce off a relatively smooth

surface.

Refraction- the in direction of a ray as it passes obliquely from one medium to another

with different velocities of propagation.

Skip distance (ds) – the minimum distance from a transmit antenna that a sky wave of

given frequency (which must be less than the Maximum Usable Frequency (MUF)) will

be returned to earth.

Surface wave - (see ground wave).

Waveguide- a special type of transmission line that consist of a conducting metallic tube

through which high frequency electromagnetic energy is propagated.

2

Description of the link

This long, over water link supports the wireless communication between Sagnay,

Camarines Sur and San Andres, Catanduanes. The connectivity requires 10 voice

channels, 10 video channels, 10 data channels and 10 spare channels which would be

required for future expansions.

This microwave radio link has a line type of 1xE3 with a rate of 34.368 Mbps and

a capacity of 480 channels. It operates in the 7.89 GHz to 8.20 GHz common carrier band

allocated to fixed point-to-point service. This frequency band was chosen since the rain

attenuation at these frequencies will not be a limiting factor in the link reliability.

Although the link is only 59 km long, the height restriction on the tower antenna required

100m at both site to provide adequate path clearance, and to avoid diffraction loss and

clutter loss. Using QPSK modulation the radio unit has an enough transmit power at both

site and have a much lower receive threshold. Since the elevation of the site A and site B

are different, we compute for the vertical inclination of the antenna. For the difference in

height of 286m, by using trigonometry we found that the vertical inclination of the

antenna is 0 16’ 39.85”.̊

2

MICROWAVE PLANNING

Condition:

Path length: 59 km

Reliability requirement: 99.9999%

Configuration: Non-protected (1 + 0)

Traffic capacity: 1 x E3 with a rate of 34.368 Mbps and a capacity of 480 channel.

Site A:

Latitude: 13o 34’ 3”

Longitude: 123 o 31’ 22.5”

Site B:

Latitude: 13o 38’ 15”

Longitude: 124 o 31’ 52.5”

LOCATION LONGITUDE LATITUDE

SITE A: Sagñay, Camarines Sur 1230 31’ 22.5” 130 34’ 3”

SITE B: San Andres, Catanduanes 1240 3’ 52.5 “ 130 38’ 15”

Computation for azimuth angle

C= Longitude B – Longitude A = LOB – LOA = 124˚ 3’ 52.5” - 123˚ 31’ 22.5” = 0˚ 32’ 30”½C = 0˚ 16’ 15”

(LB + LA) = 13˚ 38’ 15” + 13˚ 34’ 3” = 27˚ 12’ 18”

½(LB + LA = 13˚ 36’ 9”

(LB - LA) = 13˚ 38’ 15” - 13˚ 34’ 3” = 0˚ 4’ 12”

2

½(LB – LA) = 0˚ 2’ 6”

Log tan ½ (Y+X) = log cot ½ C + log cos ½ (LB – LA) – log sin ½ (LB + LA)

tan½ (Y+X) = log -1 [log cot ½ C + log cos ½ (LB – LA) – log sin ½ (LB + LA)]

½ (Y+X) = tan -1 {log -1[log cot ½ C + log cos ½ (LB – LA) – log sin ½ (LB + LA)]}

½ (Y+X) = tan -1 {log -1 [log cot 0˚ 16’ 15” + log cos 0˚ 2’ 6” – log sin 13˚ 36’ 9”]}

½ (Y+X) = 89˚ 56’ 10.69”

Log tan ½ (Y-X) = log cot ½ C + log sin ½ (LB – LA) – log cos ½ (LB + LA)

tan ½ (Y-X) = log -1[log cot ½ C + log sin ½ (LB – LA) – log cos ½ (LB + LA)]

½ (Y-X) = tan -1{log -1 [log cot ½ C + log sin ½ (LB – LA) – log cos ½ (LB + LA)]}

½ (Y-X) = tan -1{log -1 [log cot 0˚ 16’ 15”+ log sin 0˚ 2’ 6”- log cos 13˚ 34’ 3”]}

½ (Y-X) = 7˚ 34’ 20.91”

Log tan ½ (Z) = log tan ½ (LB – LA) + (Y+X) – log sin ½ (Y-X)

tan½ (Z) = log -1[log tan ½ (LB – LA) + (Y+X) – log sin ½ (Y-X)]

½ (Z) = 2 {tan -1[log tan 0˚ 2’ 6” + log sin 89˚ 56’ 10.69” - log sin 7˚ 34’ 20.9”]}

½ (Z) = 0˚ 31’ 52.26” + 7˚ 34’ 20.91”

2

D = Z *111.12

Where: D = distance in km.

D = 0˚ 31’ 52.26” *111.12

D = 59.02 km

Azimuth Angle

Y = ½ (Y+X) + ½ (Y-X)

Y = 89˚ 56’ 10.69” + 7˚ 34’ 20.91”

Y = 97˚ 31’ 31.6”

X = ½ (Y+X) – ½ (Y-X)

X = 89˚ 56’ 10.69”- 7˚ 34’ 20.91”

X = 82˚ 21’ 49.78”

2

2

Site A: Sagñay, Camarines sur

Population - 29 082 (2007)

Land Area - 108.19 km2 (41.8 sq mi)

Barangays – 19 Barangays

Mean temperature- 28.76 degrees Celsius

Maximum temperature- 31.92 degrees Celsius

Mean humidity- 82.94 %

Precipitation amount- 99.72 mm

Mean wind speed- 9 km/h

Maximum wind speed-225 km/h

Indicator for occurrence of: rain or drizzle- 3.6

Indicator for occurrence of: thunder- 1.6

Site B: San Andres, Cantanduanes

Population - 33,781 (2007)

Land area – 252.40 square kilometer

Barangays – 27 Barangays

Mean temperature- 25.94 degrees Celsius

Maximum temperature- 27.7 degrees Celsius

Mean humidity- 89.01 %

Precipitation amount- 430.46 mm

Mean wind speed- 19.1 km/h

Maximum wind speed-240 km/h

Indicator for occurrence of: rain or drizzle- 8.9

Indicator for occurrence of: thunder- 1.9

2

Transmitter and receiver equipment specifications

CFQ series 8 GHz digital microwave radio unit

Frequency range: 7.7 GHz – 8.3 GHz

Waveguide: WR112

Frequency = 7.05-10.00 GHz

Internal dimension = 1.122 x 0.497 in.

Connector: BNC F/F NI/SI UG-914/U

8 GHZ VSWR 1.25 ROHS

Flange: UBR 84

Antenna: VP4-71W

Where:

VP = unshielded, single polarized

4 = 4 ft., 1.2 m in diameter

71W = 7.125 GHz – 8.5 GHz

Type of map

Topographical Map

Scale = 1:250,000

Frequency band required.

8 GHz for 60 km

2

Channel plans available.

Frequency band: 8 GHz

Frequency range: 7.7 GHz to 8.3 GHz

Low band range: 7747.70 MHz to 7955.25 MHz

High band range: 8059.02 MHz to 8266.57 MHz

Duplex spacing: 311.32 MHz

Channel bandwidth for 1x E3: 28 MHz

No. of duplex channels = 7955.25 MHz - 7747.70 MHz

28 MHz

= 7.41 (7 channels)

Selecting 5 channel spacing above the high band and low band edge:

28 MHz * 5 = 140 MHz

Low Band Frequency

7747.70 MHz + 140 MHz = 7887.70 MHz

High Band Frequency

8059 MHz + 140 MHz = 8199.02 MHz

2

Minimum elevation of site A and site B.

h = d2/(12.75* k)

Where: d = (path length in km)/2

h = minimum site elevation in m.

k = 4/3

h = 29.52/ [12.75* (4/3)]

h = 51.19 m

2

Table plotting points along the path.

2

2

2

2

Determining minimum reliable tower height

Lk = d1d2/ 12.75* k

Lf = 17.3 * F % *

L = Lk + LF + LHF

Lk = 29 *30

12.75 *(4/3)

Lk = 51.18 m

LF = 17.3 * 0.60 *

LF = 14.18 m

L = Lk + LF + LFH

= 51.18 m + 14.18 m + 386 m

L = 451.36 m

Where: L = clearance criteria in meters

Lk= curvature factor in meters

Lf = fresnel factor in meters

LFH = arbitrary fixed height in meters

d1 = distance from site A to point, in kilometer

d2= distance from site B to point, in kilometer

D = path distance in kilometer

F% = fresnel zone percentage factor

f lower = low band transmit frequency in GHz

Clearance Criteria At Fixed Height of 386 Meters

2

Reflection Point looking from Site A (Transmitter at 100 m above MSL)

2

Fade Margins

2

Radio Configuration = Outdoor Mounted RF Module (ODU)

Transmit Power = 32 dBm

Receiver Threshold (1 x E3 at 8 GHz) = -86 dBm

Flexible Waveguide loss:

Low band frequency = (0.2624 dB/m) (0.6)

= 0.1574 dB

High band frequency = (0.2624 dB/m) (0.6)

= 0.1574 dB

Antenna used = 1.2 m in diameter (8 GHz) with Mid Band Gain of 37.5 dB

Waveguide used = WR112 (0.6 m flexible waveguide in site A and site B)

Connector Loss = 0.5 dB

Free Space Loss (FSL):

For Low Band:

FSL = 92.45 + 20 log10 (f * d)

FSL = 92.45 + 20 log10 (7.89 * 59)

FSL = 145.81 dB

For High Band:

2

FSL = 92.45 + 20 log10 (f * d)

FSL = 92.45 + 20 log10 (8.20 * 59)

FSL = 146.14 dB

Where: f = frequency

d = path length in Km

Computation for Low Band Frequency (7.89 GHz)

PARAMETERS VALUE UNITS

Microwave Radio Output Power 32.00 dBmConnector Loss (TX) 0.50 dBFlexible Waveguide Loss (TX) 0.16 dBAntenna Gain (TX) 37.50 dBFree Space Loss (FSL) 145.81 dBAntenna Gain (RX) 37.50 dBConnector Loss (RX) 0.50 dBFlexible Waveguide Loss (RX) 0.16 dBPower Input to Receiver (RSL) -39.13 dBMinimum Receiver Threshold -86.00 dBmThermal Fade Margin 42.87 dB

Computation for High Band Frequency (8.20 GHz)

2

PARAMETERS VALUE UNITS

Microwave Radio Output Power 32.00 dBmConnector Loss (TX) 0.50 dBFlexible Waveguide Loss (TX) 0.16 dBAntenna Gain (TX) 37.50 dBFree Space Loss (FSL) 146.14 dBAntenna Gain (RX) 37.50 dBConnector Loss (RX) 0.50 dBFlexible Waveguide Loss (RX) 0.16 dBPower Input to Receiver (RSL) -39.46 dBMinimum Receiver Threshold -86.00 dBmThermal Fade Margin 46.54 dB

Dispersive Fade Margin Dispersive Fade Margin at 1 x E3 is 90 dB.

Interference Fade Margin

Assume that no interference fade margin is given; therefore it is not included in the

computation.

2

2

Frequency in GHz

kH kV αV αH

1 0.0000387 0.0000352 0.1920000 0.8800002 0.0001540 0.0001380 0.9630000 0.9230004 0.0006500 0.0005910 1.1210000 1.0750006 0.0017500 0.0015500 1.3080000 1.2650007 0.0030100 0.0026500 1.3320000 1.3120008 0.0045400 0.0039500 1.2760000 1.31000010 0.0101000 0.0088700 1.2170000 1.26400012 0.0188000 0.0168000 1.1540000 1.20000015 0.0367000 0.0335000 1.0990000 1.12800020 0.0751000 0.0691000 1.0610000 1.06500025 0.1240000 0.1130000 1.0610000 1.03000030 0.1870000 0.1670000 1.0210000 1.00000035 0.2630000 0.2330000 0.9790000 0.96300040 0.3500000 0.3100000 0.9390000 0.929000

Rain Losses

CCIR/ITU-R Recommendation 530 rain attenuation

For Low Band Frequency (7.89 GHz)

M = (log10 f1 – log10 fx)/ (log10 f1 – log10 f2) note: f1 < fx <f2

M = (log10 7 – log10 7.89)/ (log10 7 – log10 10)

M = 0.33

k = log10-1

[log10k1 – M (log10k1 – log 10k2)]

k = log10-1 [log10 0.00887 – 0.33(log10 0.00887 – log10 0.00265)]

k = 0.00593604

α = α1 – M (α1 – α2)

α = 1.276 – 0.33 (1.276 – 1.332)

α = 1.29448

2

For High Band Frequency (8.20 GHz)

M = (log10 f1 – log10 fx)/ (log10 f1 – log10 f2) note: f1 < fx <f2

M = (log10 7 – log10 8.20)/ (log10 7 – log10 10)

M = 0.44

k = log10-1

[log10k1 – M (log10k1 – log 10k2)]

k = log10-1

[log10 0.0087 – 0.44(log10 0.0087 – log 10 0.00265)]

k = 0.005212732

α = α1 – M (α1 – α2)

α = 1.276 – 0.44(1.276 – 1.332)

α = 1.30064

Computation for the effective rain path length

D0 = 35 *ℓ - 0.015* R0.001 where: DE = effective rain path length

D0 = 35* ℓ - 0.015* 180 R0.001 = rainfall rate at 0.001% outage

D0 = 2.3521

DE = D/1 + (D/D0)

DE = 59/1 + (59/2.3521)

DE = 2.2619 km

Computation for the unit rain attenuation

2

For Low Band Frequency (7.89GHz)

k = 0.00593604

α = 1.29448

y = k *(R0.001) α

y = 0.00593604 (180) 1.29448

y = 4.9306

For High Band Frequency (8.20 GHz)

k = 0.005212732

α = 1.30064

y = k * (R0.001) α

y = 0.005212732 (180) 1.30064

y = 4.4706

Rain Attenuation

For Low Band Frequency (7.89 GHz)

A rain = DE * y

A rain = (2.2619) (4.4306)

A rain = 11.1525 dB

For High Band Frequency (7.89 GHz)

2

A rain = DE * y

A rain = (2.2619) (4.4706)

A rain = 10.1120 dB

Atmospheric Losses

Oxygen absorption loss

Computation for absorption loss at a path length of 30 km:

A0 = [7.19 * 10-3 + (6.09/f2 + 0.227) + (4.81/ (f – 57)2 + 1.5)] f2 * 10-3 dB/km

Where: f = frequency in GHz

For Low Band Transmit Frequency (7.89 GHz)

A0 = [7.19 * 10-3 + (6.09/ ((7.89)2 + 0.227) + (4.81/ (7.89 – 57)2 + 1.5)] [(7.89)2 * 10-3

dB/km]

A0 = [7.19-3 + 0.0975 + 1.99 * 10-3] [(7.89)2 * 10-3dB/km]

A0 = (0.10668) (7.892) (10-3) dB/km

A0 = 0.0066 dB/km

Atmospheric Losses for 59 km = (0.0066 dB/km) (59 km)

= 0.3894 dB

2

For High Band Transmit Frequency (8.20 GHz)

A0 = [7.19 *10-3 + (6.09/((8.20)2 + 0.227) + (4.81/(8.20 – 57)2 + 1.5)][ (8.20)2 * 10-3

dB/km]

A0 = [7.19-3 + 0.090266+ 2.02*10-3] [(8.20)2 * 10-3dB/km]

A0 = (0.09947) (8.202) (10-3) dB/km

A0 = 0.0067 dB/km

Atmospheric Losses for 59 km = (0.0067 dB/km) (59 km)

= 0.3946 dB

Water Vapor Loss

AH2O = [0.067 + (3/f2 + 7.3) + (9/(f – 1833)2 + 6) + (4.3/(f – 323.8)2 + 10]

[f2 * α *10-4dB/km]

Where: f = frequency in GHz

α= water vapor density in gm/m3 should be below 12 gm/m3

Computing for water vapor loss at a path length of 59km

For Low Band Frequency (7.89 GHz)

AH2O = [0.067 + (3/7.892 + 7.3) + (9/ (7.89 – 1833)2 + 6) + (4.3/ (7.89 – 323.8)2 + 10]

[7.892 * 10-4dB/km]

AH2O = (0.08129) (7.892) (12*10-4) dB/km

AH2O = 0.0061dB/km

Water Vapor Loss for 59 km = (0.0061 dB/km) (59km)

2

= 0.3583 dB

For High Band Frequency (8.20 GHz)

AH2O = [0.067 + (3/8.202 + 7.3) + (9/ (8.20 – 1833)2 + 6) + (4.3/(8.20 – 323.8)2 + 10]

[8.202* 10-4dB/km]

AH2O = 0.0066077 dB/km

Water Vapor Loss for 59 km = (0.0066077 dB/km)

= 0.3899 dB

Antenna Misalignment

A 0.5dB overall in the link budget to compensate the misalignment of the antenna during

installation.

2

2

2

Diffraction loss and clutter loss

Since there is no point along the path comes closer than 150% first Fresnel, there

is no need to compute for the diffraction loss and clutter loss.

Table of the given and calculated data

Computation for low band frequency-Tx = 7.89 GHz

RSL = transmitter output – (Tx) waveguide loss + (Tx) Antenna gain – FSL

+ (Rx) Antenna gain – (Rx) Waveguide loss

RSL = 32 dBm – 0.16 dB + 37.50 dB – 145.81 dB + 37.50 dB – 0.16

RSL = - 39.13 dB

TFM = RSL – Receiver Threshold

TFM = -39.13 dB – (- 86 dBm)

TFM = 46.87 dB

PARAMETERS VALUE UNITS

Microwave Radio Output Power 32.00 dBmConnector Loss (Tx) 0.50 dBFlexible Waveguide Loss (Tx) 0.16 dBAntenna gain 37.50 dBFree Space Loss (FSL) 145.81 dBAtmospheric Losses (Oxygen Absorption) 0.39 dBAtmospheric Losses (Water Vapor Loss) 0.36 dBRain Attenuation 11.15 dBAntenna misalignment loss 0.50 dBFlexible Waveguide Loss (Rx) 0.16 dBAntenna gain (Rx) 37.50 dBConnector Loss (Rx) 0.50 dBPower Input to Receiver (RSL) -39.13 dBMinimum Receiver Threshold -86.00 dBmThermal Fade Margin (TFM) 46.87 dBDispersive Fade Margin 90.00 dB

2

Calculation for high band frequency – Tx = 8.20 GHz

RSL = Transmitter Output – (Tx) Waveguide loss + (Tx) Antenna Gain – FSL

+ (Rx) Antenna Gain – (Rx) Waveguide Loss

RSL = 32dBm – 0.16dB + 37.50 dB – 146.14 dB + 37.50 dB – 0.16 dB

RSL = - 39.46 dB

Thermal Fade Margin = RSL – Receiver Threshold

TFM = - 39.46 dB – (-86 dBm)

TFM = 46.54 dB

PARAMETERS VALUE UNITS

Microwave Radio Output Power 32.00 dBmConnector Loss (Tx) 0.50 dBFlexible Waveguide Loss (Tx) 0.16 dBAntenna gain 37.50 dBFree Space Loss (FSL) 146.14 dBAtmospheric Losses (Oxygen Absorption) 0.39 dBAtmospheric Losses (Water Vapor Loss) 0.39 dBRain Attenuation 10.11 dBAntenna misalignment loss 0.50 dBFlexible Waveguide Loss (Rx) 0.16 dBAntenna gain (Rx) 37.50 dBConnector Loss (Rx) 0.50 dBPower Input to Receiver (RSL) -39.46 dBMinimum Receiver Threshold -86.00 dBmThermal Fade Margin (TFM) 46.54 dBDispersive Fade Margin 90.00 dB

Flat Fade Margin

Calculation for the Flat Fade Margin is given by the formula:

FM FLAT = -10 log [10 (-FMthermal/10) + 10 (-FMadj – chan/10) + 10 (-FMint/10)

+ 10 (-Fmdiff/10)]

2

For low band transmit frequency – Tx (7.89 GHz)

FMFLAT = -10 log [10 (-46.87/10)]

FMFLAT = 46.87 dB

For high band transmit frequency – Tx (8.20 GHz)

FMFLAT = -10 log [10 (-46.54/10)]

FMFLAT = 46.54 dB

Composite Fade Margin

Calculation for the composite or effective fade margin is given by the formula:

FM EFF = -10 log [10 (-FMflat/10) + RD *10 (-FMdsp/10)]

Where: RD = Fade Occurance Factor

For low band transmit frequency – Tx (7.89 GHz)

FM EFF = -10 log [10 (-46.87/10) + 7 *10 (-90/10)]

FM EFF = 46.8685 dB

For high band transmit frequency – Tx (8.20 GHz)

FM EFF = -10 log [10 (-46.54/10) + 7 *10 (-90/10)]

FM EFF = 46.5386 dB

Reliability Calculation

K – Q Reliability Calculation

U = K – Q f b d c * 10 (-FMeff/10)

Where: K – Q = Regional K – Q value

f = frequency in GHz

2

d = Path length in km

b,c = Regional Climate Factor

FMeff = Effective Fade Margin

For low band transmit frequency – Tx (7.89 GHz)

ULB = 1 *10 -9* 7.89 1.2 * 59 3.5 * 10 (-46.8685/10)

ULB = 3.869 * 10 -7

For high band transmit frequency – Tx (8.20 GHz)

UHB = 1 *10 -9* 7.89 1.2 * 59 3.5* 10 (-46.5386/10)

UHB = 4.372 * 10 -7

Unfaded Reliability is then computed as 1- unavailability

For low band transmit frequency – Tx (7.89 GHz)

RLB = (1 – 3.869 * 10 -7) * 100 %

RLB = 99.999961 %

For high band transmit frequency – Tx (8.20 GHz)

RHB = (1 – 4.372 * 10 -7) * 100 %

RHB = 99.999956%

Using the same value for K – Q of 1*10 -9, b = 1.2 and c = 3.5, the unavailability and

reliability for link due to rain can be calculated.

Rain Fade Margin = Effective Fade Margin – Rain Attenuation

For low band transmit frequency – Tx (7.89 GHz)

RFMLB = 46.8685 dB – 11.15 dB

RFMLB = 35.7185 dB

2

For high band transmit frequency – Tx (8.20 GHz)

RFMHB = 46.5386 dB – 10.11 dB

RFMHB = 36.4286 dB

For low band transmit frequency – Tx (7.89 GHz)

ULB = 1 *10 -9 * 7.89 1.2 * 59 3.5 * 10 (-35.7185/10)

ULB = 5.042 * 10 -6

For high band transmit frequency – Tx (8.20 GHz)

UHB = 1 *10 -9* 8.20 1.2 * 59 3.5 * 10 (-36.4286/10)

UHB = 4.484 * 10 -6

Reliability for low band transmit frequency – Tx (7.89 GHz)

RLB = (1 – 5.042 * 10 -6)* 100 %

RLB = 99.99949 %

Reliability for high band transmit frequency – Tx (8.20 GHz)

RHB = (1 - 4.484 * 10 -6) *100 %

RHB = 99.99955 %

K – Q Reliability with terrain roughness

Taking the standard deviation of regular increments of the path.

M = Average Elevation above MSL

2

S = Standard Deviation of the elevations in the path

Where: N = number of path length subdivisions between the two end stations

M = Average Elevation within the path

S = Standard Deviation of the elevation within the path

2

Path elevations do not include site elevations

Sum = 629.00 188745.00 Average = 10.84 3254.22

2

SD =

SD = 56.00

Calculation for the K – Q reliability with terrain roughness is given by the formula:

U = (K – Q / S 1.3) * f b *dc * 10(-FMeff /10)

Where: K – Q = Regional K – Q value

f = frequency in GHz

d = Path length in km

b and c = Regional Climate Factor

FMeff = Effective Fade Margin

S = Standard Deviation of the terrain elevation

(also called Roughness Factor)

For low band transmit frequency – Tx (7.89 GHz)

ULB = (1*10-9 / 56 1.3) * 7.891.2* 593.5 * 10(-46.8685 /10)

ULB = 2.065 * 10-9

For high band transmit frequency – Tx (8.20 GHz)

UHB = (1*10-9 / 56 1.3) * 7.891.2* 593.5* 10(-46.5386 /10)

UHB = 2.334 *10-9

2

Unfaded Reliability is then computed as:

For low band transmit frequency – Tx (7.89 GHz)

RLB = (1 -2.065 * 10-9) *100 %

RLB = 99.99999979 %

For high band transmit frequency – Tx (8.20 GHz)

RHB = (1 -2.334*10-9) * 100 %

RHB = 99.99999977 %

Calculating Rain Fade Margin:

RFM = Effective Fade Margin – Rain Attenuation

For low band transmit frequency – Tx (7.89 GHz)

RFM= 46.8685 dB – 11.15 dB

RFM= 35.7185 dB

For high band transmit frequency – Tx (8.20 GHz)

RFM= 46.5386 dB – 10.11 dB

RFM= 36.4286 dB

For low band transmit frequency – Tx (7.89 GHz)

ULB = (1 *10 -9/561.3) * 7.89 1.2 * 59 3.5 * 10 (-35.7185/10)

ULB = 2.691 * 10 -8

For high band transmit frequency – Tx (8.20 GHz)

UHB = (1*10-9 / 56 1.3) * 7.891.2 * 593.5 * 10(-36.4286 /10)

UHB = 2.394 * 10-8

2

Reliability for low band transmit frequency – Tx (7.89 GHz)

RLB = (1 – 2.691*10 -8) *100 %

RLB = 99.9999973 %

Reliability for high band transmit frequency – Tx (8.20 GHz)

RHB = (1 -2.394*10 -8) * 100 %

RHB = 99.9999976 %

Vigants – Barnette Calculation

The Vigants – Barnette unavailability formula is given as:

U = 6.0 * 10-7* c * f * d3 * 10(-FMeff /10)

Where: c= c factor value which is equal to 4 for the difficult propagation

Condition

f= frequency in GHz

d= path length in km

For low band transmit frequency – Tx (7.89 GHz)

ULB = 6.0 * 10-7*4*7.89 * 59 3 * 10 (-46.8685/10)

ULB = 7.998 *10 -5

For high band transmit frequency – Tx (8.20 GHz)

UHB = 6.0 *10-7 * 4*7.89 * 593 * 10(-46.5386 /10)

UHB = 8.969*10-5

2

Unfaded Reliability is:

For low band transmit frequency – Tx (7.89 GHz)

RLB = (1 -7.998 * 10-5) *100 %

RLB = 99.9920 %

For high band transmit frequency – Tx (8.20 GHz)

RHB = (1 -8.969 * 10-5) * 100 %

RHB = 99.10 %

Calculation for the unavailability due to rain is done:

Rain Fade Margin = Effective Fade Margin – Rain Attenuation

For low band transmit frequency – Tx (7.89 GHz)

RFM= 46.8685 dB – 11.15 dB

RFM= 35.7185 dB

For high band transmit frequency – Tx (8.20 GHz)

RFM= 46.5386 dB – 10.11 dB

RFM= 36.4286 dB

Unavailability during rain:

For low band transmit frequency – Tx (7.89 GHz)

ULB = 6.0 * 10-7 * 4 * 7.89 * 59 3 * 10 (-35.7185/10)

ULB = 1.04 * 10 -3

For high band transmit frequency – Tx (8.20 GHz)

UHB = 6.0 * 10-7 * 4 * 7.89 * 593*10(-36.4286 /10)

UHB = 9.19858 * 10-4

2

The reliability during rain:

For low band transmit frequency – Tx (7.89 GHz)

RLB = (1 -1.04 * 10-3) *100 %

RLB = 99.89576963 %

For high band transmit frequency – Tx (8.20 GHz)

RHB = (1 -9.19858 * 10-4) * 100 %

RHB = 99.908%

MICROWAVE PATH DATA SHEET

Capacity: 1xE3

Low band transmit frequency: 7.89 GHz

High band transmit frequency: 8.20 GHz

Equipment: CFQ series 8 GHz digital microwave radio unit

Site A: Sagñay, Camarines sur

Site B: San Andres, Catanduanes

Path length: 59 km

Modulation: QPSK

Site Information Low Band High Band

Site A Site B UnitsLongitude 123 o 31’ 22.5” 124 o 31’ 52.5” DMS

Latitude 13o 34’ 3” 13o 38’ 15” DMS

Site Elevation (Above Mean Sea Level) 100.00 100.00 m

2

Tower Elevation (Above Ground Level) 100.00 100.00 m

Azimuth From True North 82 o 21’ 49.78” NE 97 o 31’ 31.6” NW DMS

Equipment InformationSite A Site B Units

Transmitter Output Power 32.00 32.00 dBmReceiver Input Threshold -86.00 -86.00 dBmWaveguide length 0.60 0.60 dBWaveguide loss 0.16 0.16 dBConnector loss 0.50 0.50 dBAntenna Gain 37.50 37.50 dBAntenna Misalignment loss 0.50 0.50 dBWet/Frozen Antenna loss 0.50 0.50 dB

Path LossesSite A Site B Units

Free Space Loss 145.81 146.14 dBOxygen Absorption Loss 0.36 0.39 dBRain Attenuation 11.15 10.11 dB

Fade MarginsSite A Site B Units

Thermal Fade Margin 46.87 46.54 dBDispersive Fade Margin 90.00 90.00 dBFlat Fade Margin 46.87 46.54 dBEffective Fade Margin 46.8685 46.5386 dBRain Fade Margin 35.7185 36.4286 dB

Path ReliabilitySite A Site B Units

Unfaded Reliability (one way) 99.999961 99.999956 %Rain Reliability (one way) 99.99949 99.99955 %Link Reliability (Duplex) 99.999 99.999 %

2

2

Tower

The medium tower has the following physical properties:

• Maximum height - 104 m

• Parallel section - 10 m

• Parallel face width - 1 m

• Footprint for 104 m tower - 13.7 m

• Tower heights – in 2 m increments up to 60 m,

thereafter in 4 m increments up to 104 m

Foundation Designs

Tower Height

Concrete Volume

Rebar Excavation Backfill

(m3) (kg) (m3) (m3)

30 12 900 24 12

36 17 1258 33 16

40 18 1350 36 18

46 19 1078 50 31

50 26 1350 57 31

56 32 2242 60 28

60 41 3075 82 41

64 45 3375 90 45

72 48 4452 126 78

Antenna Loading CapacityTower capacity of 92 m tower under the following loading conditions:

Maximum survival wind speed

77.77 m/s

Antenna loading 10.5 kN or 6 m2 over the to 10m

2

2

2

Equipment Shelter

2

2

2

2

2

2

Building Description

Framework: The building shall have a complete, internal, self-supporting,

structural steel frame which does not rely on the exterior panels or roof cover panels for

any of its structural strength or framing. The building framework shall include 8 to 16

gauge, cold-formed, galvanized steel structural members. Building framework to have a

flush wall, post and beam format with girts and purlins, and full trusses on both endwalls

which easily allows for future expansion and/or modifications. Wall and ceiling structural

support system are to be designed to provide load carrying capability for anticipated

equipment loads using 16 gauge galvanized steel hat channels behind liner panel for

reinforcement as needed, with locations shown on approval drawings. Roof to have 8

gauges to 14 gauge solid web hot rolled steel trusses.

2

Insulation: Exterior walls shall have a minimum of 3.5”, fiberglass batt insulation

and a vapor barrier. The ceiling shall have a minimum of 6” cellulose insulation and a

vapor barrier. In addition to the insulation in the walls and ceiling, an additional 1”

cellulose insulation blanket shall be installed over the entire building framework and

under the exterior wall and roof panels, as a thermal break. The insulation system shall

provide a minimum of R-19 in the walls, R-24 above the ceiling, and R-30 in the floor.

Cellulose to have a minimum flame spread rating of 5

Roof: A roof pitched 1 inch in 12 or greater shall have a covering of overlapping,

18 gauge, G-90 galvanized, ribbed steel panels with a baked-on Kynar 500, PVDF resin-

based finish in manufacturer’s standard colors. Overlapping roof panels shall be installed

with appropriate self-tapping fasteners with integral gaskets. A roof with a pitch of less

than 1 inch in 12 shall have a roof covering of mechanically-seamed, 24 gauge, Standing-

Seam Roofing, with a minimum seam height of 2”. Standing seam roof panels shall be of

Galvalume steel, with a baked-on Kynar 500, PVDF resin-based coating and shall have

no visible fasteners on main run. Roof to include a matching, die-formed ridge cap, and a

fully supported 3” overhang. Properly sized attic space ventilation shall be provided.

Exterior Walls: The exterior walls shall be 18 gauge ribbed G-90 galvanized steel

panels with a baked-on PVDF resin-based finish in manufacturer’s standard colors.

Exterior siding panels to be overlapped and installed with appropriate self-tapping

fasteners with integral gaskets, and shall be removable without any disturbance to interior

panels. Butted seams are not allowed. All openings in walls are to be structurally framed,

2

sleeved, trimmed, and provided with external drip caps. Repair or replacement of exterior

panels must be able to be done entirely from outside.

Exterior Trim: The exterior trim package shall include stepped or boxed eave,

rake, fascia, base, corner, jamb, and header trim in, 26 gauge Galvalume material with

owner’s choice of standard KYNAR colors.

Interior Finish: The building’s interior walls and ceiling shall be lined with flush-

fit 22 gauge, roll-formed liner panels, with concealed fasteners and a baked-on White

polyester finish over G-90 galvanized substrate. The building interior shall feature a

complete matching trim system including base, jamb, header, and ceiling trim

Interior Dimensions: The building’s finished interior dimensions shall be no less

than 10 ½” in width and length from the exterior dimensions shown on the drawings.

Minimum floor to ceiling dimension shall be nominal 10’.

Fasteners, Adhesives, and Sealants: The fasteners, adhesives, and sealants utilized

shall be of types approved for use on this type of structure as required by the appropriate

agency or governing body, as covered in section 1.02 of these specifications.

Closures: Matching, pre-molded, closed cell elastomer closures provided by the

siding and roof panel manufacturer shall be installed according to the manufacturer’s

recommendations at the eave line, beneath the roof panels, and where the trim meets the

wall panels.

2

Station Layout

2

Conclusion

In designing a microwave communication link, the following should be

considered; choosing appropriate frequencies which may be used for a specific distance,

path terrain conditions, factor that affect microwave signals and the reliability of the link.

In a long haul, the proper of the transmit equipment should be high enough in

order to attain much higher reliability. It is more difficult also to attain a higher reliability

in an over water link because of higher reflection coefficient, and when the path length is

increases because of the increase in value of free space path loss.

The size of each Fresnel Zone varies based on the frequency of the radio

signal and the length of the path. As frequency decreases, the size of the Fresnel

Zone increases. As the length of the path increases, the size of the Fresnel Zone

also increases. A Fresnel Zone radius is greatest at the midpoint of the path.

Therefore, the midpoint requires the most clearance of any point in the path.

2

APPENDICES

2

2

2

2

2

2

2

REFERENCES

2

BOOKS:

Fundamentals of Microwave Communication with planning guide

By: Manny T. Rule

Electronic Communication System, Fundamental Through Advance

By: Wayne Tomasi

INTERNET SITES:

www.andrew.com

www.globalspec.com

www.commscope.com/andrew/eng/product/towers/index.html