Method for measuring the distance and/or the relative velocity between two objects

• US 4,851,851 A
• Filed: 07/21/1987
• Issued: 07/25/1989
• Est. Priority Date: 12/12/1985
• Status: Expired due to Fees

• Current Assignee: Stiftelsen Institutet For Mikrovagsteknik Vid Tekniska Hogskolan I Stockholm
• Original Assignee: Stiftelsen Institutet For Mikrovagsteknik Vid Tekniska Hogskolan I Stockholm
• Inventors: Hane, Bengt
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Hellner, Mark
• Application Number:
  US07/088,847
• Time in Patent Office: 735 Days
• Field of Search: 342/43, 342/112, 342/118, 342/125, 342/127, 342/129
• US Class Current: 342/112
• CPC Class Codes: G01S 13/38 wherein more than one modulation frequency is used
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement

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 φ between the transmitted signals are formed, these phase differences corresponding to the distance between the transmitter-receiver unit and the transponder.

Claims

1. A method of measuring the distance between, and/or the mutual relative speed, of two objects which respectively include a transmitter-receiver unit and a transponder, and in which method a phase comparison is made between a signal transmitted from the transmitter-receiver unit and a signal received in said unit from the transponder, wherein the transmitter-receiver unit is caused to transmit plural signals of microwave frequency, approximately about 2450 MHz;

said transmission of plural signals comprising transmitting a first signal having a first frequency;

transmitting at least one second signal having a higher or a lower frequency than said first signal;

transmitting a third signal having the same frequency as said first mentioned signal;

said first, second and third signals being transmitted in succession, all of said first, second and third signals being of microwave frequency as herein set forth, and all of said first, second and third signals, while transmitted, being continuous wave signals whereby, for each said transmitted signal a phase difference φ

between the transmitted and received signal is formed, which phase differences correspond to the distance between the transmitter receiver unit and the transponder, characterized in that said second signal includes a first series of signals that form a frequency series of successively rising frequencies and a second series of signals that form a frequency series of successively falling frequencies, said first series, and said second series, being transmitted in succession, whereby a median value (slope L9) is formed of the respective change of the phase difference with the frequency (slope L8;

L9) that occurs during the series of rising frequencies and falling frequencies respectively, which median value (slope L9) corresponds to said distance.

2. A method according to claim 1, characterized in that the first and the third said transmitted signals, both have a frequency of 2450 MHz;

and in that the frequency differential between the frequency of said first and third transmitted signals and the frequency of the said second transmitted signal is substantially lower, and within the range from 50 kHz to 50 MHz.

3. A method according to claim 1, characterized in that the difference between two mutually adjacent frequencies in each said series of frequencies is constant, about 50 kHz.

4. A method according to claim 1, characterized by transmitting in succession a plurality of series of said first, second, and third signals, in which the frequency difference between the said second signal and the two remaining signals rises, which corresponds to a successive decrease in the unambiguous distance range between the objects.

5. A method according to claim 1, characterized by transmitting in a first stage and in succession a plurality of series of said first, second, and third signals, in which the frequency difference between the second signal and the two remaining signals rises, which corresponds to a successive decrease in the unambiguous distance range between the objects;

and by transmitting in a second stage said two frequency series of successively rising and successively falling frequencies respectively, and determining the distance between the unambiguous distance range.

6. A method according to claim 4, characterized in that said series of said first, second, and third signals are at least three in number;

and in that said frequency differences rise in accordance with a series which is an even multiple of the lowest frequency difference, for example the series 50 kHz, 500 kHz and 50 MHz.

7. A method according to claim 1, characterized by forming the differential between the phase difference that occurs when transmitting the first transmitted frequency and the phase difference that occurs when transmitting the last transmitted frequency, which last transmitted frequency is equal to the first transmitted frequency, said differential corresponding to the momentary velocity of one object in relation to the other.