Radar Systems and Radio Aids to Navigation by A.K. Sen & A.B. Bhattacharya

Author:A.K. Sen & A.B. Bhattacharya [A.B. Bhattacharya, A.K. Sen]
Language: eng
Format: epub
Publisher: Mercury Learning and Information
Published: 2018-02-09T05:00:00+00:00

11.12.2Determination of Radar Parameters

The average power received Pr at range r can be expressed as

(11.6)

where Pi = peak transmitted power in the pulses

G = antenna gain

h = pulse length in space

λ = wavelength

θ = beam width between half power points

and r = range

Again (11.7)

where | k |2 is a function of the dielectric constant of the targets and is approximately 0.93 for water and 0.179 for ice in the microwave band. By equations (11.6) and (11.7)

(11.8)

The quantity commonly designated by Z is known as the reflectivity factor.

In practice the gain G is realized only at the center of the beam, and the intensity tapers off with increasing axial angle. If the antenna is a circular paraboloid, the distribution of intensity in the main beam is closely approximated by the Gaussian function of the axial angle α and is expressed as

(11.9)

An effective beam width θe can be found by integrating the actual beam intensity pattern for two-way transmission out to some axial angle α1 which is considered large enough to include all the scatterers contributing to the signal. Then,

(11.10)

Integration of equation (11.10) yields

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