Signal strength in telecommunications

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In telecommunications, especially in radio frequency, signal strength (also referred to as terrain strength ) refers to the transmitter power output as received by the reference antenna at the distance from the antenna transmission. High-powered transmitters, such as those used in broadcasting, are expressed in dB-millivolts per meter (dBmV/m). For systems with very low power, such as cell phones, signal strength is usually expressed in dB-microvolts per meter (dBÃ,ÂμV/m) or in decibels above the reference level of one milliwatt (dBm). In broadcasting terminology, 1 mV/m is 1000 Ã,ÂμV/m or 60 dBÃ,Âμ (often written dBu).

Example

• 100 dBÃ,Âμ or 100 mV/m: blanketing interference can occur on multiple receivers
• 60 dBÃ,Âμ or 1.0 mV/m: often considered the edge of a radio station's protection area in North America
• 40 dBÃ,Âμ or 0.1 mV/m: the minimum power at which the station can be received with acceptable quality on most recipients

Video Signal strength in telecommunications

Relationship with average radiated power

The strength of the electric field at a given point can be determined from the power delivered to the transmitting antenna, geometry and radiation resistance. Consider the case of dipole half-wave center-fed in free space, where the total length of L is equal to one half wavelength (?/2). If built from a thin conductor, the current distribution is essentially sinusoidal and the radiating electric field is given by

$Â\; Â{\displaystyle Â\; Â\; Â\; Â\; Â\; Â\; Â}$ _{          E                        ?                         (          r        )         =                                    Â       Â ·     Â    Â        I                                ?        ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ,       Â                            Â 2               ?    Â                ?                                ?        ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ,       Â       ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂï <½                    Â                                                                  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ|                                                                                                         ?                     2                 <      ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ,                  cos                                 ?    ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ, <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<                             Â Â <Â>                           ?                                                e                 Â                       Â (                              ?                t              -      Â          Â         ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ,                  )                                            {\ displaystyle E _ {\ theta} {r} = {- jI _ {\ circ} \ over 2 \ pi \ varepsilon _ {\ circ} c \, \} \ cos \ left {\ scriptstyle {\ pi \ over 2} \ cos \ theta \ right) \ over \ sin \ theta} e ^ {j \ left (\ omega t-kr \ right)}}  Â}

Memecahkan rumus ini untuk hasil arus puncak

${\ displaystyle I _ {\ circ} = 2 \ pi \ varepsilon _ {\ circ} c \, r \ vert E _ {\ pi/2} (r) \ vert \ ,.}  ÂÂ$

Daya rata-rata antena adalah

${\ displaystyle {P_ {avg} = {1 \ over 2} R_ {a} \, I _ {\ circ} ^ {2}}}  ÂÂ$

Therefore, if the average power for dipole half dipole antennas is 1 mW, then the maximum electric field at 313 m (1027 ft) is 1 mV/m (60 dBÃ,Âμ).

Untuk dipol pendek ( ${\ displaystyle \ scriptstyle {L \ ll \ lambda/2}}  ÂÂ$ ) distribusi saat ini hampir berbentuk segitiga. Dalam hal ini, medan listrik dan ketahanan radiasi

${\ displaystyle E _ {\ theta} (r) = {- jI _ {\ circ} \ sin (\ theta) \ over 4 \ varepsilon _ {\ circ} c \, r} \ kiri ({L \ over \ lambda} \ right) e ^ {j \ left (\ omega t-kr \ right)} \, \ quad R_ {a} = 20 \ pi ^ {2} \ kiri ({L \ over \ lambda} \ right) ^ {2}.}  ÂÂ$

Dengan menggunakan prosedur yang serupa dengan itu di atas, medan listrik maksimum untuk dipole pendek pusat-makan adalah

${\ displaystyle \ vert E _ {\ pi/2} (r) \ vert \, = \, {1 \ over \ pi \ varepsilon _ {\ circ} c \, r} {\ sqrt {P_ {avg} \ over 160}} \, = \, {9.48 \ over r} {\ sqrt {P_ {avg}}} \ quad (L \ ll \ lambda/2) \ ,. }  ÂÂ$

Maps Signal strength in telecommunications

Sinyal RF

Although there are cell phone BTS networks in many countries globally, there are still many areas in countries that do not have good reception. Some rural areas can not possibly be effectively closed because the cost of setting up cell towers is too high for only a few customers. Even in high reception areas it is often found that the basements and interior of large buildings have poor reception.

Weak signal strength may also be caused by destructive interference from signals from local towers in urban areas, or by construction materials used in some buildings that cause rapid attenuation of signal strength. Large buildings such as warehouses, hospitals and factories often have no signals that can be used more than a few feet from the outer wall.

This is especially true for networks that operate at higher frequencies because these are attenuated more quickly by intervening obstacles, although they can use reflection and diffraction to avoid obstacles.

Estimated signal strength received

Perkiraan kekuatan sinyal yang diterima dalam tag RFID aktif dapat diperkirakan sebagai berikut:

$            {\displaystyle         d        B        m_{            e          }        =        -        \mathrm{43,0}        -        \mathrm{40,0}        \text{Â}        {}_{}}$ log                         10                                                  (                                        r                R                                   )                           {\ displaystyle dBm_ {e} = - 43.0-40.0 \ \ log _ {10} \ kiri ({\ frac {r} {R}} \ right)}   

Lebih umum, Anda dapat membawa eksponen path loss ke dalam akun:

$            {\displaystyle         d        B        m_{            e          }        =        -        \mathrm{43,0}        -        \mathrm{10,0}        \text{Â}        ?        \text{Â}        {}_{}}$ log                         10                                                  (                                        r                R                                   )                           {\ displaystyle dBm_ {e} = - 43.0-10.0 \ \ gamma \ \ log _ {10} \ kiri ({\ frac {r} {R}} \ kanan) }   

Effective path damage depends on frequency, topography, and environmental conditions.

Sebenarnya seseorang bisa menggunakan kekuatan sinyal dBm ₀ manapun pada jarak r ₀ sebagai referensi:

$            {\displaystyle         d        B        m_{            e          }        =        d        B        m_{            0          }        -        \mathrm{10,0}        \text{Â}        ?        \text{Â}        {}_{}}$ log                         10                                                  (                                        r                                 r                                     0                                                                   )                           {\ displaystyle dBm_ {e} = dBm_ {0} -10.0 \ \ gamma \ \ log _ {10} \ kiri ({\ frac {r} {r_ {0} }} \ right)}   

Jumlah dekade

$            {\displaystyle         {}_{}}$ log                         10                                       (          R                    /                   r         )                  {\ displaystyle \ log_ {10} (R/r)}    akan memberikan perkiraan jumlah dekade, yang bertepatan dengan kehilangan jalur rata-rata 40 dB/dekade.

Perkirakan radius sel

Ketika kita mengukur jarak sel r dan menerima pasangan dBm _m , maka kita dapat memperkirakan radius sel rata-rata sebagai berikut:

${\ displaystyle R_ {e} = \ operatorname {avg} [\ r \ 10 ^ {(dBm_ {m} 43.0)/40.0} \]}  ÂÂ$

A special calculation model exists to plan the location of new cell towers, taking into account local conditions and radio equipment parameters. Consider also that mobile radio signals have line-of-sight propagation, unless reflexion will occur.

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See also

• Cel-Fi
• Mobile networks
• Mobile
• Mobile repeater
• Call dropped
• Dead zone (phone)
• Field strength in free space
• Field strength meter
• Signal strength indication received
• S meter
• Signal (electrical engineering)
• Mobile signals
• Mobile coverage

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References

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External links

Source of the article : Wikipedia