Experimental estimations of measurement accuracy of delay time are presented for UHF- and SHF-band signals propagating in opened paths and paths closed by obstacles (wood). In experiments, request-response radar equipment was used which had two frequency channels of measurements.
In the UHF band, the channel has sounding and responding pulses manipulated by 1023 bit M-sequence, repetition tome of 0,1 ms and clock frequency of 10,08 MHz. Direct spread-spectrum technique was used with binary phase manipulation of carrier. Method of measurement arrival time is based on finding of \"gravity center\" of cross-correlation function (CCF). Calculation of \"center of gravity\" of CCF is provided after measuring system is set to synchronization on received consistently with step on time of 3,67 ns to 27 readouts of CCF. Jitter caused by equipment instability and noise, which occurs after signal\'s single travel, was estimated in short-range lines by value of 0,13 ns, and in extended-range lines by 0,18 ns. The variation of average delay time, caused by external temperature change in –5 C to +25 C range, has changed within 1 ns period.
In SHF channel the pulse signal without intrapulse modulation was used. In equipment the threshold method of measurement of the moment of arrival at which time position of crossing by an accepted signal of the threshold equal approximately 1,2 STD of internal noise of the receiver was accepted to the arrival moment has been realized. Thus, estimations of the moment of arrival stood out with timestep about 11 nanoseconds on each registered impulse and have been adhered to number (counted from the beginning of a window of registration) the clock impulse arriving on start ADC.
Measurement of delays of signals in SHF channel was carried out by means of АDC on which one input the signal from the receiver, on other input generated in equipment of a decimeter range impulses of start АDC shifted on time for some initial delay, proportional to extent of a line was given. Installation of this delay was made in the program image before occurrence of an accepted signal in a window of registration both in conducted, and in the leader points. The half-sum of a program delay with a delay in a registration window in ADC was an estimation of a delay of a signal on a line and also contained delays in equipment.
Iordan V., EHggert O., Knejjsel M. Rukovodstvo po geodezii.
T. 6 // Per. s 10-go nemeckogo izdanija. M.: Nedra. 1971.
Arbuzov JU.V. EHksperimentalnye issledovanija troposfernogo
kanala metodom impulsnojj radiolokacii s aktivnym otvetom // Radiotekhnika. 1975. T. 30. № 4. S. 14–18.
Kalinin A.I. Rasprostranenie radiovoln na trassakh nazemnykh i
kosmicheskikh radiolinijj. M.: Svjaz. 1979.
Krutikov M.V., Kornienko V.G., Tancajj P.I. Vlijanie peresechennojj
trassy RRV na tochnost izmerenija vremennojj zaderzhki v decimetrovom i
santimetrovom diapazonakh voln // Trudy VII Rossijjskojj nauchno-tekhnicheskojj
konferencii «Navigacija, gidrografija i okeanografija: prioritety razvitija i
innovacii morskojj dejatelnosti». SPb: Gosudarstvennyjj nauchno-issledovatelskijj
navigacionno-gidrograficheskijj institut. 2011. S. 234–243.