Method and apparatus for measuring distances
First Claim
1. 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 which the transmitter-receiver unit transmits a signal to the transponder and receives a signal transmitted by the transponder, these signals being signals of microwave frequencies characterized by transmitting a first unmodulated microwave signal (S1'"'"';
- S1) from the transmitter-receiver unit (1;
40);
receiving said signal (S1'"'"';
S1) in the transponder (2;
18;
41);
generating in the transponder a second signal (S3'"'"';
S3) of much lower frequency Fm ;
modulating said second signal (S3'"'"';
S3) in the transponder on a signal (S2'"'"';
S6) having a microwave frequency so that said modulated signal contains the phase of the unmodulated microwave signal received by the transponder;
transmitting the modulated signal (S7'"'"';
S7) from the transponder to the transmitter-receiver unit (1;
29;
40) in which said signal is received and mixed down with the first signal (S1'"'"';
S1) and subsequently (a) low-passed filtered, to form a first measuring signal (s10'"'"';
S10) having the frequency Fm, the phase of which corresponds to the phase difference between the first microwave signal (S1'"'"';
S1) and the microwave signal received in the transmitter-receiver unit (1;
19;
40), and (b) demodulated, therewith to obtain a second measuring signal (S12'"'"';
S12) having the frequency Fm, the phase of which corresponds to the phase of the second signal (S3'"'"';
S3) generated in the transponder; and
by comparing the phases of the measuring signals (S10'"'"';
S12'"'"';
S10;
S12) in a phase comparison circuit (13;
27), forming a phase difference therebetween, said difference between the measuring signals being due to the phase shift of the undemodulated microwave signal transmitted from the transmitter-receiver unit caused by its travel to the transponder and back again, and thereby being proportional to the distance between said two objects.
1 Assignment
0 Petitions
Accused Products
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 Fm 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 Fm, the phase of which corresponds to the phase difference between the first microwave signal (S1) and the microwave signal (S8) received in the transmitter-receiver unit (19) and (b) de-modulated, thereby to form a second measuring signal (S12) having the frequency Fm, the phase of which corresponds to the phase of the second signal (S3) generated in the transponder (18). The phases of the two measuring signals (S10, S12) are compared in a phase comparison circuit (27) to form a difference therebetween, this difference being proportional to the distance between the objects.
-
Citations
15 Claims
-
1. 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 which the transmitter-receiver unit transmits a signal to the transponder and receives a signal transmitted by the transponder, these signals being signals of microwave frequencies characterized by transmitting a first unmodulated microwave signal (S1'"'"';
- S1) from the transmitter-receiver unit (1;
40);
receiving said signal (S1'"'"';
S1) in the transponder (2;
18;
41);
generating in the transponder a second signal (S3'"'"';
S3) of much lower frequency Fm ;
modulating said second signal (S3'"'"';
S3) in the transponder on a signal (S2'"'"';
S6) having a microwave frequency so that said modulated signal contains the phase of the unmodulated microwave signal received by the transponder;
transmitting the modulated signal (S7'"'"';
S7) from the transponder to the transmitter-receiver unit (1;
29;
40) in which said signal is received and mixed down with the first signal (S1'"'"';
S1) and subsequently (a) low-passed filtered, to form a first measuring signal (s10'"'"';
S10) having the frequency Fm, the phase of which corresponds to the phase difference between the first microwave signal (S1'"'"';
S1) and the microwave signal received in the transmitter-receiver unit (1;
19;
40), and (b) demodulated, therewith to obtain a second measuring signal (S12'"'"';
S12) having the frequency Fm, the phase of which corresponds to the phase of the second signal (S3'"'"';
S3) generated in the transponder; and
by comparing the phases of the measuring signals (S10'"'"';
S12'"'"';
S10;
S12) in a phase comparison circuit (13;
27), forming a phase difference therebetween, said difference between the measuring signals being due to the phase shift of the undemodulated microwave signal transmitted from the transmitter-receiver unit caused by its travel to the transponder and back again, and thereby being proportional to the distance between said two objects. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- S1) from the transmitter-receiver unit (1;
-
9. Apparatus for measuring the distance between a first object, incorporating a transmitter-receiver unit, and a second object, incorporating a transponder, in which apparatus the transmitter-receiver unit is constructed to transmit a signal of microwave frequency to the transponder and to receive a signal of microwave frequency transmitted therefrom, characterized in that the transmitter-receiver unit (1;
- 19;
40) includes a microwave oscillator (7;
20) and a transmitting aerial (3;
21) and receiving aerial (4;
22);
that the transponder (2;
18;
41) includes a receiving aerial (6;
28) and a transmitting aerial (5;
29), the transponder being intended to receive an unmodulated microwave signal (S1'"'"';
S1) transmitted from the transmitter-receiver unit;
that the transponder incorporates signal generating means (8;
32;
33) for generating a second signal (S3'"'"';
S3) of much lower frequency Fm than the frequency of the unmodulated microwave signal;
that a first modulator (17;
31) is provided in the transponder for modulating said second signal (S3'"'"';
S3) on a signal (S2'"'"';
S6) having a microwave frequency so that said modulated signal contains the phase of the unmodulated microwave signal received by the transponder, which transponder is constructed to transmit this modulated signal to the transmitter-receiver unit, which unit is constructed to receive said signal;
that the transmitter-receiver unit includes a mixer (9;
23) for mixing down the received signal (S8'"'"';
S8) with the frequency generated by the microwave oscillator (7;
20); and
in that the transmitter-receiver unit is constructed to divide a thus received signal, partly via a low-pass filter (10;
24) so as to produce a measuring signal (S10'"'"';
S10) having the aforesaid frequency Fm the phase of which corresponds to the phase difference between the phase of the signal (S1'"'"';
S1) transmitted from the transmitter-receiver unit and the phase of the signal (S8'"'"';
S8) received in said unit, and partly via a detector circuit (11,12;
25,26) for demodulating the signal received by the transmitter-receiver unit, thereby to form a second measuring signal (S12'"'"';
S12) having the frequency Fm, the phase of which corresponds to the phase of the signal (S3'"'"';
S3) of frequency Fm generated in the transponder (2;
18;
41); and
in that the transmitter-receiver unit (1;
19;
40) incorporates a phase comparison circuit (13;
27) for comparing the phases of the aforesaid measuring signals, the difference between the measuring signals being due to the phase shift of the unmodulated microwave signal transmitted from the transmitter-receiver unit caused by its travel to the transponder and back again, which is proportional to the distance (R) between said objects. - View Dependent Claims (10, 11, 12, 13, 14, 15)
- 19;
Specification