Abstract: Times t.sub.1 and t.sub.2 required for two electromagnetic waves having different wavelengths to propagate from a reference point to a target point are measured. Necessary meteorological conditions along the path are also measured to determine refractivities N.sub.1 and N.sub.2 of the path for the two electromagnetic waves as:N.sub.1 =.alpha..sub.1 .multidot..rho..sub.s +.beta..sub.1 .multidot..rho..sub.wN.sub.2 =.alpha..sub.2 .multidot..rho..sub.s +.beta..sub.2 .multidot..rho..sub.wwhere .rho..sub.s and .rho..sub.w are densities of dry air and water vapor in the path, respectively. Length of the path D is calculated using the following formula:D=[t.sub.1 +{(.alpha..sub.1 +.beta..sub.1 .multidot..rho..sub.w /.rho..sub.s).multidot.(t.sub.2 -t.sub.1)}/{(.alpha..sub.1 +.beta..sub.1 .multidot..rho..sub.w /.rho..sub.s)-(.alpha..sub.2 +.beta..sub.2 .multidot..rho..sub.w /.rho..sub.s)}].multidot.C.where C is the speed of an electromagnetic wave in vacuum.

Abstract: The invention relates to a measuring system having a measuring array comprising a transmission and reception section and an electronic evaluation unit. In accordance with the invention, the distance between a first point and a second point is determined by moving the measuring array between the two points using the Doppler effect, with an intermediate frequency being formed in the transmission and reception section from the transmission frequency of the signal emitted by the transmission section and from the reception frequency of the signal reflected off a fixed object and picked up in the reception section, and the number of periods of intermediate frequency generated during the measuring operation being counted in the electronic evaluation unit to derive the distance.

Abstract: An apparatus and method for identifying the path/time relationships of a projectile within a weapon barrel, even upon live firing, includes a coupling element having at least two openings in a sidewall thereof through which a generated electromagnetic wave is divided and then introduced into the barrel. The divided wave includes wave parts that propagate toward and away from the barrel, the parts propagating toward the barrel adding up and being introduced into the barrel while the parts propagating away from the barrel cancel each other out. The wave reflects off from the projectile and is then received after undergoing an inverse division.

Abstract: A propagation time detecting system wherein a transmitting station transmits to a receiving station, over a plurality of transmitting paths or lines having different propagation times, a transmission signal comprising a sequence of transmission data digitized by a clock signal of a clock frequency. The receiving station receives the transmission signal through the respective transmitting paths or lines as different received signals, and reproduces the sequence of transmission data and the clock signal as different reproduced sequences of transmission data and different reproduced clock signals, from which differences are detected among the different propagation times. In order to improve the accuracy of the detected differences, at least one subcarrier signal with a frequency higher than the clock frequency is also transmitted together with the transmission signal.

Abstract: In a method of detecting the deflection of the blades 13 of a helicopter rotor as it rotates, a beam 14 of radiation from a transmitter/receiver 11 encounters the tips of the rotating blades which send reflected signals to the receiver. The phase difference due to deflection of the blade tip can be used to give a measure of the deflection of each blade, and that can be displayed graphically as shown in FIGS. 7-10 for the various blades at various speeds. In a related method of measuring deflections of the blades 111 for a tail rotor, a laser beam transmitter 16 in FIG. 14 has its reflected beam 122, 123 from an undeflected blade 111 or a deflected blade 111' received by a particular receiver in a linear array 119 of receivers so that the particular receiver gives an indication of the amount of deflection.

Abstract: A method of measuring the distance between two objects and/or the speed of one object in relation to the other, the objects incorporating respectively a transmitter-receiver unit and a transponder or reflector, in which method a phase comparison is made between a signal transmitted by the transmitter-receiver unit and a signal received in the transmitter-receiver unit and transmitted from the transponder or reflector. In accordance with the invention the transmitter-receiver unit is caused to transmit signals of microwave frequency, preferably about 2450 MHz, this transmission comprising the transmission of a first signal having a first frequency, the transmission of at least one second signal having a higher or lower frequency, and the transmission of a third signal having the same frequency as the first mentioned signal, wherewith the phase differences .phi.

Abstract: An accurate ranging system for position determination of a mobile unit using trilateralization. A pair of active reflectors return signals transmitted by the mobile unit in phase at the reflectors, after compensating for interval circuit delay. The mobile unit compares the phases and determines mutual distances and thus its position. The invention includes a two frequency technique for compensating for inaccuracies introduced at distances in excess of one wavelength and for inaccuracies observed at a large multiple of wavelengths, and also includes means for dynamically compensating for drift.

Abstract: A system and method are disclosed for measuring medium range distances, of about 1-10 meters, to a target. A transmission signal is reflected off the target, with the phase difference between the transmitted and received signals taken as an indication of the target distance. The transmitter and receiver are part of a phase-locked loop, with a VCO adjusting the transmission frequency until a predetermined transmission-reception phase difference is reached. A coarse distance measurement is first obtained by comparing the transmitted signal with the received signal, followed by a fine distance measurement in which a multiple of the transmission signal frequency is compared with the received signal. The frequency multiplication in the preferred embodiment is obtained by dividing the VCO output frequency to obtain the transmission frequency. The transmission signal is initialy set at a low frequency prior to the coarse adjustment to avoid phase ambiguities.

Abstract: A laser radar system wherein a beam of continuous wave (CW) electromagnetic energy is generated with frequency modulation (FM) and amplitude modulation (AM) being imposed thereon to produce an amplitude and frequency modulated, continuous wave beam of energy. The AM-FM CW beam is transmitted toward a selected target, portions of the transmitted beam being reflected by the target and received along with portions of the transmitted beam reflected by unselected targets and atmospheric clutter. A first signal is produced in response to the frequency modulation on the received beam portions reflected by the selected target, such first signal representing the approximate range of the selected target and substantially resolving the selected target from unselected targets and atmospheric clutter and having a relatively long ambiguous range interval.

Abstract: A method for measuring the distance between a first object, which incorporates a transmitter-receiver unit, and a second object, which incorporates a transponder. In accordance with the invention there is transmitted from the transmitter-receiver unit (19) a first microwave signal (S1), which is received in the transponder (18). A second signal (S3) of much lower frequency F.sub.m is generated in the transponder and is modulated on a signal (S6) of microwave frequency in the transponder to form a modulated signal (S7). The modulated signal (S7) is transmitted from the transponder to the transmitter-receiver unit (19), where it is received and mixed down with the first signal (S1) and thereafter is (a) low-pass filtered to form a first measuring signal (S10) having the frequency F.sub.

Abstract: A method and device are provided for measuring the propagation time of a wave, wherein a wave is transmitted modulated in amplitude by a modulation signal. The wave reflected by an obstacle is received after a propagation time and the amplitude thereof is detected. The average value of the product of the detected signal and a reference signal is calculated and the delay with respect to the modulation signal is controlled so as to cancel out the average value. The modulation signal and the reference signal comprise a succession of elementary signals chosen so as to allow, in a single measurement, a long propagation time to be determined without ambiguity and with high accuracy.

Abstract: A signal is transmitted from a first location to a remote second location where a target carrying a transponder is positioned. The transponder re-radiates the signal to the first location where it is received. A phase comparator generates from the transmitted and received signals a measurement of their phase difference which is functionally related to the distance between the first and second locations. In one embodiment, the transponder is a passive parametric oscillator, being powered by energy received from the transmitted signal, which generates and transmits a subharmonic of the transmitted signal.

Abstract: In a continuous wave electromagnetic positioning or distance measuring system of the Wadley type (see U.S. Pat. No. 2,907,999) a number of secondary phase measurements are obtained from a number of successively produced primary phase measurements in such a manner that any instrumental errors incorporated in the primary phase measurements are eliminated. Each secondary phase measurement represents the fractional part of the phase delay that would be experienced by a signal of accurately known measuring frequency when propagated electromagnetically along a propagation path corresponding in length to the distance to be measured. The measuring frequency is determined by the frequencies of pattern and auxiliary pattern signals used in obtaining the primary phase measurements.