: power (W) available from an isotropic antenna located at this point pr : wavelength (m).  3 The free-space basic transmission loss for a radar system (symbols: or Lbr A0r) systems represent a special case because the signal is subjected to a loss while propagating both from the transmitter to the target and from the target to the receiver. For radars using a common antenna for both transmitter and receiver, a radar free-space basic transmission loss, Lbr, can be written as follows: 103.4 20 log 40 log 10 log (6)     mmmmmmdB Lbr d – where: : radar target cross-section (m2)  : distance from the radar to the target (km) d : frequency of the system (MHz). f The radar target cross-section of an object is the ratio of the total isotropically equivalent scattered power to the incident power density. 4 Conversion formulae On the basis of free-space propagation, the following conversion formulae may be used. Field strength for a given isotropically transmitted power:  20 log  74.8 (7) E Pt d – Isotropically received power for a given field strength: 20 log 167.2 (8) Pr  E f – – Free-space basic transmission loss for a given isotropically transmitted power and field strength: 20 log 167.2 (9) Lbf  Pt E  f  – Power flux-density for a given field strength: 145.8 (10)  S E – where: : isotropically transmitted power (dB(W)) Pt : isotropically received (dB(W)) Pr : electric field strength (dB(V/m)) E : frequency (GHz) f : radio path length (km) d : free-space basic transmission loss (dB) Lbf : power flux-density (dB(W/m2)). S Note that equations (7) and (9) can be used to derive equation (4).
pr : power (W) available from an isotropic antenna located at this point  : wavelength (m). 3 The free-space basic transmission loss for a radar system (symbols: Lbr or A0r) systems represent a special case because the signal is subjected to a loss while propagating both from the transmitter to the target and from the target to the receiver. For radars using a common antenna for both transmitter and receiver, a radar free-space basic transmission loss, Lbr, can be written as follows: Lbr  103.4  20 log   40 log d – 10 log mmmmmmdB (6) where:  : radar target cross-section (m2) d : distance from the radar to the target (km) f : frequency of the system (MHz). The radar target cross-section of an object is the ratio of the total isotropically equivalent scattered power to the incident power density. 4 Conversion formulae On the basis of free-space propagation, the following conversion formulae may be used. Field strength for a given isotropically transmitted power: E  Pt – 20 log d  74.8 (7) Isotropically received power for a given field strength: Pr  E – 20 log f – 167.2 (8) Free-space basic transmission loss for a given isotropically transmitted power and field strength: Lbf  Pt – E  20 log f  167.2 (9) Power flux-density for a given field strength: S  E – 145.8 (10) where: Pt : isotropically transmitted power (dB(W)) Pr : isotropically received (dB(W)) E : electric field strength (dB(V/m)) f : frequency (GHz) d : radio path length (km) Lbf : free-space basic transmission loss (dB) S : power flux-density (dB(W/m2)). Note that equations (7) and (9) can be used to derive equation (4).
R-REC-P.525-3-201611-I!!MSW-E.docx