range Dmin which the range finder is capable to measure, corresponds to one full beating during modulation (Nm =. It agrees (it means that Fb=fm, and from (follows that to F=4ΔfmFmin/. From here we find the minimum range measured by a frequency range finder:
Range between the purpose and RLS is most often measured in a radar-location. There are pulse, frequency and phase methods of measurement of range. The purpose of this work is the description of frequency and phase methods.
Set of the methods and technical means intended for detection of various objects in space, measurements of their coordinates and parameters of the movement by means of reception and the analysis of the electromagnetic waves radiated or reradiated by objects is called as a radar-location.
Frequency of Fm1 is chosen proceeding from the set most measured range, and the biggest large-scale frequency – according to the demanded accuracy of measurements. Thus the number of scales has to be such that at recalculation of this mistake on the next exact scale the maximum phase error of a scale did not exceed 2π.
At the same time large-scale frequency influences the accuracy of determination of range. Really, from a formula (range =Δφ/4πF =λΔφ/4π and if the phasemeter measures Δφ with a mean square mistake σΔφ, range decides on a mean square mistake
The following indications of a range finder will already correspond to two (Nm=2; Fb=2fm), we rub (Fb=3fm), etc. to full beats for one period of modulation. Means, there is an error of discretization of measurement of range equal to jump
Apparently, the contradiction is inherent in all phase range finders: the increase in large-scale frequency promotes increase of accuracy of measurements, but reduces a limit of unambiguously measured range. Let's consider how this contradiction in two phase methods put into practice is allowed.
It is clear, that the already the filter pass-band ΔF, the is higher resolution on range and the less possible divergences between truth and the range of the purpose specified by the indicator. Same the increase in frequency of modulation and deviation of frequency promotes.
In one half-cycle of modulation of Tm/2 the frequency of the fprd transmitter increases also speed ν> 0, and in other half-cycle – on the contrary; at the same time the frequency of Fd cannot physically be negative size. Therefore in a formula (absolute value of speed is entered