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faq:freedom-from-feedback [2015/04/21 16:12] hess |
faq:freedom-from-feedback [2015/10/14 11:06] (current) fachet [GSM-R] |
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====== Freedom from Feedback ====== | ====== Freedom from Feedback ====== | ||
- | As a rule of thumb, a good decoupling required a distance of 5 to 10 λ. (([λ] Lambda = Wave length)) | + | As a theoretical rule of thumb, a good decoupling requires a distance of 5 to 10 λ.(([λ] Lambda = Wave length = v/f with v∼3×10<sup>8</sup> m/s.))\\ |
- | In practive, in most cases a distance of 3 λ is sufficient. \\ | + | However, in practive often a distance of 3 λ is sufficient. \\ |
- | <html> | + | |
- | λ = v/f with v∼3×10<sup>8<sup> m/s. | + | |
- | </html> | + | |
+ | At 2.1 GHz (e.g. UMTS) the formula returns 300'000'000/2'100'000'000 = 300/2100 = 0.14m. | ||
- | For GSM-R Deutsche Bahn requires a decoupling of up to -60 dBm. According to a simulation of one of our antenna supplier a distanec of 350 cm is sufficant to fulfill this requirements | + | Three λ will then be 0.42m i.e. 42cm. |
- | Source: {{:faq:entkopplung_gsm-r_-_v02.pdf|}} | + | ===== GSM-R ===== |
+ | For GSM-R Deutsche Bahn requires a decoupling of up to -60 dBm. According to a simulation of one of our antenna supplier a distance of 350 cm is sufficant to fulfill this requirements | ||
+ | |||
+ | Source: {{{{:faq:simulation_report_decoupling_gsm-r_v06.pdf|}} | ||
+ | |||
+ | Quelle: {{:faq:simulation_report_entkopplung_gsm-r_v06.pdf|}} |