Radar device and method of measuring distance and reflecting factor

• US 20040263383A1
• Filed: 06/10/2004
• Published: 12/30/2004
• Est. Priority Date: 06/27/2003
• Status: Active Grant

• Current Assignee: Makita Corporation
• Original Assignee: Makita Corporation
• Inventors: Sako, Masahiko
• Granted Patent: US 7,009,552 B2
• Time in Patent Office: Days
• US Class Current: 342/118
• CPC Class Codes: G01S 13/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated

Abstract

A radar device for measuring distance within short range is provided. The radar device has a first wave-detecting circuit for multiplying radio wave voltage being transmitted from a transmitting antenna by radio wave voltage being received by a receiving antenna, in addition, the device has a second wave-detecting circuit for multiplying radio wave voltage being transmitted from the transmitting antenna by radio wave voltage shifted by the shifting means from the radio wave being received by the receiving antenna. Alternatively, the second wave-detecting circuit may multiply radio wave voltage shifted by the shifting means from the radio wave being transmitted from the transmitting antenna by radio wave voltage being received by the receiving antenna. Based on output voltages from the first and second detecting circuit, the distance to the target may be decided unambiguously.

Claims

1. A radar device comprises:

a transmitting antenna for transmitting sine-wave radio wave towards a target,

a receiving antenna for receiving radio wave reflected from the target,

a first wave-detecting circuit for multiplying radio wave voltage being transmitted from the transmitting antenna by radio wave voltage being received by the receiving antenna,

a shifting means for causing ¼

period phase shift in either the radio wave being transmitted or the radio wave being received, and

a second wave-detecting circuit for multiplying radio wave voltage being transmitted from the transmitting antenna by radio wave voltage shifted by the shifting means from the radio wave being received by the receiving antenna, or multiplying radio wave voltage shifted by the shifting means from the radio wave being transmitted from the transmitting antenna by radio wave voltage being received by the receiving antenna.

2. A radar device as set forth in claim 1, further comprises:

a means for calculating distance to the target on the basis of the ratio of the output voltage of the first wave-detecting circuit and the output voltage of the second wave-detecting circuit.

3. A radar device as set forth in claim 1, further comprises:

a means for calculating reflecting factor of the target on the basis of the sum of the square of the output voltage of the first wave-detecting circuit and the square of the output voltage of the second wave-detecting circuit.

4. A radar device as set forth in claim 1, wherein the shifting means comprises a second receiving antenna, the second receiving antenna being located at a position separated from the receiving antenna by a distance ¼

of the radio wave wavelength in addition to distance of an integer multiple of the radio wave wavelength at a further side of the receiving antenna from the target, whereby the radio wave received by the second receiving antenna has ¼

period phase shift behind the radio wave received by the receiving antenna.

5. A radar device as set forth in claim 1, wherein the shifting means comprises a delaying means for delaying by ¼

period from the radio wave received by the receiving antenna and outputting the delayed radio wave voltage.

6. A radar device as set forth in claim 1, wherein the shifting means comprises a delaying means for delaying by ¼

period from the radio wave transmitted from the transmitting antenna and outputting the delayed radio wave voltage.

7. A radar device as set forth in claim 1, further comprises:

a switching means, the switching means being selectable between a first state and a second state;

wherein hardware of the first wave-detecting circuit and the second wave-detecting circuit comprises a common wave-detecting circuit, in the first state, the radio wave being transmitted and the radio wave being received are input to the common wave-detecting circuit, and

in the second state, the radio wave voltage being transmitted and the radio wave shifted by the shifting means from the radio wave being received, or the radio wave shifted by the shifting means from the radio wave being transmitted and the radio wave being received are input to the common wave-detecting circuit.

8. A power tool comprises the radar device as defined in claim 1.

9. A radar device comprises:

a transmitting antenna for transmitting sine-wave radio wave towards a target,

a receiving antenna for receiving radio wave reflected from the target,

a first wave-detecting circuit and a second wave-detecting circuit for multiplying the radio wave voltage transmitted from the transmitting antenna by the radio wave voltage received by the receiving antenna, and

a shifting means causing ¼

period phase shift between Δ

p1 and Δ

p2, wherein Δ

p1 is phase difference between the transmitted radio wave and received radio wave multiplied by the first wave-detecting circuit, and Δ

p2 is phase difference between the transmitted radio wave and received radio wave multiplied by the second wave-detecting circuit.

10. A radar device as set forth in claim 9, wherein the sifting means is located in at least one of the following locations:

between the transmitting antenna and the first wave-detecting circuit,

between the receiving antenna and the first wave-detecting circuit,

between the transmitting antenna and the second wave-detecting circuit,

between the receiving antenna and the second wave-detecting circuit.

11. A radar device as set forth in claim 9, further comprises:

a means for calculating the distance to the target on the basis of the ratio of the output voltage of the first wave-detecting circuit and the output voltage of the second wave-detecting circuit.

12. A radar device as set forth in claim 9, further comprises:

a means for calculating reflecting factor of the target on the basis of the sum of the square of the output voltage of the first wave-detecting circuit and the square of the output voltage of the second wave-detecting circuit.

13. A radar device as set forth in claim 9, wherein the shifting means comprises a second receiving antenna, the second receiving antenna being located at a position separated from the receiving antenna by a distance ¼

of the radio wave wavelength in addition to distance of an integer multiple of the radio wave wavelength at a further side of the receiving antenna from the target, whereby the radio wave received by the second receiving antenna has ¼

period phase shift behind the radio wave received by the receiving antenna.

14. A radar device as set forth in claim 9, wherein the shifting means comprises a delaying means for delaying by ¼

period from the radio wave received by the receiving antenna and outputting the delayed radio wave voltage.

15. A radar device as set forth in claim 9, wherein the shifting means comprises a delaying means for delaying by ¼

period from the radio wave transmitted from the transmitting antenna and outputting the delayed radio wave voltage.

16. A radar device as set forth in claim 9, further comprises:

a switching means, the switching means being selectable between a first state and a second state;

wherein hardware of the first wave-detecting circuit and the second wave-detecting circuit comprises a common wave-detecting circuit,

in the first state, the radio wave being transmitted and the radio wave being received are input to the common wave-detecting circuit, and

in the second state, the radio wave voltage being transmitted and the radio wave shifted by the shifting means from the radio wave being received, or the radio wave shifted by the shifting means from the radio wave being transmitted and the radio wave being received are input to the common wave-detecting circuit.

17. A method of measuring distance to a target, the method comprises:

a step of transmitting sine-wave radio wave towards the target,

a step of receiving radio wave reflected from the target,

a first wave-detecting step of multiplying radio wave voltage transmitted by radio wave voltage received,

a second wave-detecting step of multiplying radio wave voltage transmitted by the radio wave voltage received,

a shifting step of causing ¼

period phase shift between Δ

p1 and Δ

p2, wherein Δ

p1 is phase difference between the transmitted radio wave and received radio wave multiplied in first wave-detecting step, and Δ

p2 is phase difference between the transmitted radio wave and received radio wave multiplied in the second wave-detecting step, and

a step of calculating the distance to the target on the basis of the ratio of the output voltage obtained by the first wave-detecting step and the output voltage obtained by the second wave-detecting process.

18. A method of measuring radio wave reflecting factor of a target, the method comprises:

a step of transmitting sine-wave radio wave towards the target,

a step of receiving radio wave reflected from the target,

a first wave-detecting step of multiplying radio wave voltage transmitted by radio wave voltage received,

a second wave-detecting step of multiplying radio wave voltage transmitted by radio wave voltage received,

a shifting step of causing ¼

period phase shift between Δ

p1 and Δ

p2,

wherein Δ

p1 is phase difference between the transmitted radio wave and received radio multiplied in the first wave-detecting step, and Δ

p2 is phase difference between the transmitted radio wave and received radio wave multiplied in the second wave-detecting step, and

a step of calculating reflecting factor of the target on the basis of the sum of the square of the output voltage obtained by the first wave-detecting step and the square of the output voltage obtained by the second wave-detecting step.