Transmitting/receiving antenna, isolator, high-frequency oscillator, and high-frequency transmitter-receiver using the same

• US 20050190101A1
• Filed: 02/25/2005
• Published: 09/01/2005
• Est. Priority Date: 02/26/2004
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Kishida, Yuji, Hayata, Kazuki, Hiramatsu, Nobuki, Takenoshita, Takeshi, Oya, Yoshiko
• Granted Patent: US 7,602,333 B2
• Time in Patent Office: Days
• US Class Current: 342/175
• CPC Class Codes: G01S 7/03 Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• CPC Class Codes: H01P 1/38 Circulators
• CPC Class Codes: H01Q 13/24 constituted by a dielectric or ferromagnetic rod or pipe H01Q13/28 takes precedence

Abstract

A millimeter-wave transmitter-receiver uses an NRD guide as a fundamental configuration and includes a millimeter-wave signal oscillator, a pulse modulator, a circulator, an antenna and a mixer. In the millimeter-wave transmitter-receiver, a line length of a third dielectric guide is set so that δ=±π in which δ is a phase difference at a center frequency between a portion of a transmission millimeter-wave signal, which is reflected via a third dielectric guide on the leading end portion of the third dielectric guide and returned to leak to a third connecting portion of the circulator, and another portion of the millimeter-wave signal, which leaks from a first connecting portion to the third connecting portion of the circulator. It is possible to reduce the change in the mixer output and enhance the millimeter-wave transmission/reception performance.

Claims

1. A transmitting/receiving antenna comprising:

a circulator having first, second and third transmission lines for transmitting a millimeter-wave signal which are radially connected to a peripheral edge portion of a magnetic element by first, second and third connecting portions, respectively, the circulator outputting a millimeter-wave signal inputted from one of the connecting portions, from either one of the connecting portions adjacent to the one connecting portion; and

an antenna connected to one end of the third transmission line the other end of which is connected to the third connecting portion,

wherein a line length of the third transmission line is set so that δ

=±

π

in which δ

is a phase difference at a center frequency between a signal Wa, which is a millimeter-wave signal portion reflected via the third transmission line on the antenna and returned to leak to the second connecting portion, and a signal Wb, which is another millimeter-wave signal portion having leaked from the first connecting portion through the circulator to the second connecting portion.

3. A millimeter-wave transmitter-receiver comprising:

a millimeter-wave oscillator for generating a millimeter-wave signal;

a branching device connected to the millimeter-wave oscillator, for branching a millimeter-wave signal and outputting transmittion millimeter-wave signals to one output terminal thereof and a local signal to another output terminal thereof;

the transmitting/receiving antenna of claim 1 in which an end portion of the first transmission line is connected to the one output terminal of the branching device; and

a mixer connected between the other output terminal of the branching device and the end portion of the second transmission line of the transmitting/receiving antenna, for mixing the local signal outputted to the other output terminal and the millimeter-wave signal received by the transmitting/receiving antenna, and outputting an intermediate-frequency signal.

5. The millimeter-wave transmitter-receiver of claim 3, wherein a power ratio of the one mill-wave signal portion Wa and another mill-wave signal portion Wb is set to 0.27 or more, and a phase difference δ

is set to δ

=±

π

±

0.42π

.

7. The millimeter-wave transmitter-receiver of claim 3, further comprising a pulse modulator which is interposed between the one output terminal of the branching device and a first transmission line of the circulator, pulse-modulates the transmission millimeter-wave signal branched to the one output terminal, and outputs the transmission millimeter-wave signal,

wherein the output terminal of the mixer is provided with a switching controller for opening the output terminal when the pulse-modulated transmission mill-wave signal is outputted from the pulse modulator.

2. A transmitting/receiving antenna comprising:

a pair of parallel flat plate conductors arranged in parallel at a spacing of one half or less of a wavelength of a millimeter-wave signal;

a circulator disposed between the parallel flat plate conductors on whose inner faces having two ferrite plates arranged to confront each other, the circulator having first, second and third dielectric guides for inputting/outputting the millimeter-wave signal which are radially connected to the peripheral edge portions of the two ferrite plates by first, second and third connecting portions, respectively, the circular outputting the millimeter-wave signal inputted from one of the connecting portions, from either one of the connecting portions adjacent to the one connecting portion; and

an antenna or a waveguide tube or primary radiator connected to the antenna, disposed on the parallel flat plate conductors, and connected to a through hole which is formed at a portion of one of the parallel flat plate conductors, the portion confronting a portion of the third dielectric guide one end of which is connected to the third connecting portion, in which portion electric field of a standing wave in an LSM mode is high,

wherein a length from the one end to the portion confronting the through hole of the third dielectric guide is set so that δ

=±

π

in which δ

is a phase difference at a center frequency between a signal Wa, which is a millimeter-wave signal portion reflected via the third dielectric guide on the through hole and returned to leak to the second connecting portion, and a signal Wb, which is another millimeter-wave signal portion having leaked from the first connecting portion through the circulator to the second connecting portion.

4. A millimeter-wave transmitter-receiver comprising

the transmitting/receiving antenna of claim 2;

a mill-wave signal oscillator disposed between the parallel flat plate conductors, and attached to the first dielectric guide for frequency-modulating the high-frequency signal outputted from the high-frequency diode and for propagating the modulated signal as the mill-wave signal via the first dielectric guide;

a pulse modulator disposed between the parallel flat plate conductors, and disposed midway of the first dielectric guide for pulsating the mill-wave signal and outputting the pulsated signal as the transmission mill-wave signal via the first dielectric guide;

a fourth dielectric guide disposed between the parallel flat plate conductors, and disposed so that its one end is close to the first dielectric guide or joined at its one end to the first dielectric guide to obtain electromagnetic coupling, for propagating a portion of the mill-wave signal; and

a mixer disposed between the parallel flat plate conductors, and configured so that a midway of the fourth dielectric guide and a midway of the third dielectric guide are close to or joined to each other to obtain electromagnetic coupling, for mixing the mill-wave signal portion and the received wave received by the transmitting/receiving antenna and generating the intermediate-frequency signal.

6. The millimeter-wave transmitter-receiver of claim 4, wherein a power ratio of the one mill-wave signal portion Wa and another mill-wave signal portion Wb is set to 0.27 or more, and a phase difference δ

is set to δ

=±

π

±

0.42π

.

8. The millimeter-wave transmitter-receiver of claim 4, wherein the output terminal of the mixer is provided with a switching controller for opening the output terminal when the pulse-modulated transmission mill-wave signal is outputted from the pulse modulator.

9. An isolator, comprising:

a circulator having first, second and third transmission lines for transmitting a high-frequency signal which are connected radially with a peripheral edge portion of a magnetic element by first, second and third connecting portions, respectively, the circulator outputting a high-frequency signal inputted from one of the connecting portions, from either one of the connecting portions adjacent to the one connecting portion; and

a non-reflective terminator having one end connected to the third connecting portion and connected to the other end of the third transmission line,

wherein a line length of the third transmission line is set so that δ

=±

π

in which δ

is a phase difference at a center frequency between signals Wa, which is a millimeter-wave signal portion reflected via the third transmission line on the non-reflective terminator and returned to leak to the first transmission line, and Wb, which is another millimeter-wave signal portion having leaked from the second transmission line through the circulator to the first transmission line.

14. A high-frequency oscillator comprising:

the isolator of claim 9;

and

a voltage-controlled oscillator connected to the input terminal of the isolator, for generating a high-frequency signal.

18. A high-frequency transmitting/receiving apparatus comprising:

the high-frequency oscillator of claim 14;

a branching device connected to the output terminal of the high-frequency oscillator, for branching a high-frequency signal and outputting the branched high-frequency signal to one output terminal and the other output terminal;

a modulator connected to the one output terminal, for modulating the high-frequency signal branched to the one output terminal, and outputting the transmission high-frequency signal;

a circulator having a first terminal, a second terminal and a third terminal around a magnetic element, for outputting a high-frequency signal inputted from one of the terminals in the recited order, from a next terminal adjacent to the one terminal and inputting an output from the modulator to the first terminal;

a transmitting/receiving antenna connected to the second terminal of the circulator; and

a mixer connected between the other output terminal of the branching device and the third terminal of the circulator, for mixing the high-frequency signal branched to the other output terminal and the high-frequency signal received by the transmitting/receiving antenna and outputting an intermediate-frequency signal.

20. A high-frequency transmitting/receiving apparatus comprising:

the high-frequency oscillator of claim 14;

a branching device connected to the output terminal of the high-frequency oscillator, for branching a high-frequency signal and outputting the branched signals to one output terminal and the other output terminal;

a modulator connected to the one output terminal for modulating the high-frequency signal branched to the one output terminal, and outputting the transmission high-frequency signal;

an isolator having one end connected to the output terminal of the modulator, for transmitting the transmission high-frequency signal from one end side to the other end side;

a transmitting antenna connected to the isolator;

a receiving antenna connected to the other output terminal of the branching device; and

a mixer connected between the other output terminal of the branching device and the receiving antenna, for mixing the high-frequency signal branched to the other output terminal and the high-frequency signal received by the receiving antenna and outputting an intermediate-frequency signal.

22. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 18;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

24. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 20;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

26. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 18, wherein the radar apparatus is used for detecting the objective.

28. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 20, wherein the radar apparatus is used for detecting the objective.

30. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 18, wherein the radar apparatus is used for detecting the objective.

32. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 20, wherein the radar apparatus is used for detecting the objective.

10. An isolator, comprising:

first and second circulators each having first, second and third transmission lines for transmitting the millimeter-wave signal which are radially connected to a peripheral edge portion of a magnetic element by first, second and third connecting portions, respectively, the circulators each outputting a millimeter-wave signal inputted from one of the connecting portions, from either one of the connecting portions adjacent to the one connecting portion, the circulators being so connected that the second transmission line of the first circulator acts as the first transmission line of the second circulator; and

non-reflective terminators each having an end connected to the third connecting portion, the non-reflective terminators each being connected to the other end of the third transmission line,

wherein frequency dependency of the isolation characteristics between a high-frequency signal transmitted from the first transmission line to the second transmission line and a high-frequency signal transmitted from the second transmission line to the first transmission line of the first circulator is different from frequency dependency of isolation characteristics between a high-frequency signal to transmit from the first transmission line to the second transmission line and a high-frequency to transmit from the second transmission line to the first transmission line of the second circulator.

15. A high-frequency oscillator comprising:

the isolator of claim 10;

and

a voltage-controlled oscillator connected to the input terminal of the isolator, for generating a high-frequency signal.

19. A high-frequency transmitting/receiving apparatus comprising:

the high-frequency oscillator of claim 15;

a branching device connected to the output terminal of the high-frequency oscillator, for branching a high-frequency signal and outputting the branched high-frequency signal to one output terminal and the other output terminal;

a modulator connected to the one output terminal, for modulating the high-frequency signal branched to the one output terminal, and outputting the transmission high-frequency signal;

a circulator having a first terminal, a second terminal and a third terminal around a magnetic element, for outputting a high-frequency signal inputted from one of the terminals in the recited order, from a next terminal adjacent to the one terminal and inputting an output from the modulator to the first terminal;

a transmitting/receiving antenna connected to the second terminal of the circulator; and

a mixer connected between the other output terminal of the branching device and the third terminal of the circulator, for mixing the high-frequency signal branched to the other output terminal and the high-frequency signal received by the transmitting/receiving antenna and outputting an intermediate-frequency signal.

21. A high-frequency transmitting/receiving apparatus comprising:

the high-frequency oscillator of claim 15;

a branching device connected to the output terminal of the high-frequency oscillator, for branching a high-frequency signal and outputting the branched signals to one output terminal and the other output terminal;

a modulator connected to the one output terminal for modulating the high-frequency signal branched to the one output terminal, and outputting the transmission high-frequency signal;

an isolator having one end connected to the output terminal of the modulator, for transmitting the transmission high-frequency signal from one end side to the other end side;

a transmitting antenna connected to the isolator;

a receiving antenna connected to the other output terminal of the branching device; and

a mixer connected between the other output terminal of the branching device and the receiving antenna, for mixing the high-frequency signal branched to the other output terminal and the high-frequency signal received by the receiving antenna and outputting an intermediate-frequency signal.

23. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 19;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

25. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 21;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

27. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 19, wherein the radar apparatus is used for detecting the objective.

29. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 21, wherein the radar apparatus is used for detecting the objective.

31. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 19, wherein the radar apparatus is used for detecting the objective.

33. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 21, wherein the radar apparatus is used for detecting the objective.

11. The isolator of cliam 10, wherein a line length of the third transmission line of each of the first and second circulators is set so that δ

=±

π

in which δ

is a phase difference at a center frequency between signals Wa, which is a high-frequency signal portion reflected via the third transmission line on the non-reflective terminator and returned to leak to the first transmission line, and Wb, which is another high-frequency signal portion having leaked from the second transmission line through the circulator to the first transmission line.

12. A high-frequency oscillator comprising:

a pair of parallel flat plate conductors arranged in parallel at a spacing of one half of less of a wavelength of a high-frequency signal;

first and second circulators disposed between the parallel flat plate conductors, having two ferrite plates disposed to confront each other in an inner face of the parallel flat plate conductors, an inputting dielectric guide, disposed radially with respect to the two ferrite plates, for inputting high frequency signal, a terminating dielectric guide having a non-reflective terminator provided at a leading end thereof and an outputting dielectric guide for outputting a high-frequency signal inputted to the inputting dielectric guide, the first and second circulators being so connected to each other that the outputting dielectric guide of the first circulator acts as the inputting dielectric guide of the second circulator; and

a voltage-controlled oscillator connected to an input terminal to which the high-frequency signal of the inputting dielectric guide of the first circulator is inputted,

wherein frequency dependency of isolation characteristics between the high-frequency signal to be transmitted from the inputting dielectric guide to the outputting dielectric guide and the high-frequency signal to be transmitted from the outputting dielectric guide to the inputting dielectric guide of the first circulator is different from frequency dependency of isolation characteristics between the high-frequency signal to be transmitted from the inputting dielectric guide to the outputting dielectric guide and the high-frequency signal to be transmitted from the outputting dielectric guide to the inputting dielectric guide of the second circulator.

13. The high-frequency oscillator of claim 12, wherein the frequency dependency is adjusted by making different at least one of spacing and size of the two ferrite plates between the first circulator and the second circulator.

16. A high-frequency transmitting/receiving apparatus comprising:

a pair of parallel flat plate conductors arranged in parallel at a spacing of one half or less of a wavelength of a millimeter-wave signal;

a first dielectric guide disposed between the parallel flat plate conductors;

a mill-wave signal oscillator attached to the first dielectric guide and disposed between the parallel flat plate conductors, for outputting a mill-wave signal outputted from the high-frequency oscillator to the first dielectric guide;

a pulse modulator disposed between the parallel flat plate conductors so as to be midway of the first dielectric guide, for pulsating the millimeter-wave signal and outputting the pulsated signal as a transmission mill-wave signal via the first dielectric guide;

a second dielectric guide disposed between the parallel flat plate conductors, and disposed so that its one end is close to the first dielectric guide or joined at its one end to the first dielectric guide to obtain electromagnetic coupling, for propagating a portion of the mill-wave signal;

a circulator disposed between the parallel flat plate conductors, including ferrite plates disposed in parallel to the parallel plat plate conductors, and a first connecting portion, a second connecting portion and a third connecting portion arranged at a predetermined spacing on the peripheral edge portion of the ferrite plate, each acting as input/output terminals of the millimeter-wave signal, for outputting a millimeter-wave signal inputted from one of the connecting portions, from either one of the connecting portions adjacent to the one connecting portion clockwise or counter-clockwise in the planes of the ferrite plates, the first connecting portion being connected to the millimeter-wave signal output terminal of the first dielectric guide;

a third dielectric guide disposed between the parallel flat plate conductors and connected to the second connecting portion of the circulator, for propagating the millimeter-wave signal, the third dielectric guide having a transmitting/receiving antenna at its leading end portion;

a fourth dielectric guide disposed between the parallel flat plate conductors and connected to the third connecting portion of the circulator, for propagating a received wave which is received by the transmitting/receiving antenna, is propagated via the third dielectric guide and is outputted from the third connecting portion;

a mixer disposed between the parallel flat plate conductors and configured so that either a midway of the second dielectric guide and a midway of the fourth dielectric guide are close to or joined to each other to obtain electromagnetic coupling, for mixing a portion of the transmitting millimeter-wave signal and the receiving-wave and generating the intermediate-frequency signal; and

a non-reflective terminator disposed between the parallel flat plate conductors and connected to an end portion on opposite side of the mixer of the second dielectric guide,

wherein the high-frequency oscillator of the millimeter-wave oscillator is the high-frequency oscillator of claim 12.

17. A high-frequency transmitting/receiving apparatus comprising:

a pair of parallel flat plate conductors arranged in parallel at a spacing of one half or less of a wavelength of a millimeter-wave signal;

a first dielectric guide disposed between the parallel flat plate conductors;

a mill-wave signal oscillator attached to the first dielectric guide and disposed between the parallel flat plate conductors, for outputting a mill-wave signal outputted from the high-frequency oscillator to the first dielectric guide;

a pulse modulator disposed between the parallel flat plate conductors so as to be midway of the first dielectric guide, for pulsating the millimeter-wave signal and outputting the pulsated signal as a transmission mill-wave signal from the first dielectric guide;

a second dielectric guide disposed between the parallel flat plate conductors, and disposed so that its one end is close to the first dielectric guide or joined at its one end to the first dielectric guide to obtain electromagnetic coupling, for propagating a portion of the mill-wave signal;

a circulator disposed between the parallel flat plate conductors, including ferrite plates disposed in parallel to the parallel plat plate conductors, and a first connecting portion, a second connecting portion and a third connecting portion arranged at a predetermined spacing on the peripheral edge portion of the ferrite plates, each acting as input/output terminals of the millimeter-wave signal, for outputting a millimeter-wave signal inputted from one of the connecting portions, from either one of the connecting portions adjacent to the one connecting portion clockwise or counter-clockwise in the planes of the ferrite plates, the first connecting portion being connected to the millimeter-wave signal output terminal of the first dielectric guide;

a third dielectric guide disposed between the parallel flat plate conductors and connected to the second connecting portion of the circulator, for propagating the millimeter-wave signal, the third dielectric guide having a transmitting antenna at its leading end portion;

a fourth dielectric guide disposed between the parallel flat plate conductors and having a receiving antenna at its leading end portion;

a fifth dielectric guide disposed between the parallel flat plate conductors and connected to the third connecting portion of the circulator, for propagating a received wave which is received and mixed by the transmitting antenna and attenuating the millimeter-wave signal at a non-reflective terminator disposed at its leading end portion;

a mixer disposed between the parallel flat plate conductors, arranged at another end portion of the fourth dielectric guide and configured so that either a midway of the second dielectric guide and a midway of the fourth dielectric guide are close to or joined to each other to obtain electromagnetic coupling, for mixing a portion of the transmitting millimeter-wave signal and the receiving-wave and generating the intermediate-frequency signal; and

a non-reflective terminator disposed between the parallel flat plate conductors and connected to an end portion on opposite side of the mixer of the second dielectric guide,

wherein the high-frequency oscillator of the millimeter-wave oscillator is the high-frequency oscillator of claim 12.

34. A high-frequency transmitter-receiver comprising:

a high-frequency oscillator for generating a high-frequency signal;

a branching device connected to the high-frequency oscillator, for branching a high-frequency signal and outputting the branched high-frequency signals to one output terminal and the other output terminal;

a modulator connected to the one output terminal, for modulating the high-frequency signal branched to the one output terminal and outputting the transmission high-frequency signal;

a circulator having a first terminal, a second terminal and a third terminal around a magnetic element, for outputting a high-frequency signal inputted from one of the terminals in the recited order, from a next terminal adjacent to the one terminal and inputting an output from the modulator to the first terminal;

a transmitting/receiving antenna connected to the second terminal of the circulator; and

a mixer connected between the other output terminal of the branching device and the third terminal of the circulator, for mixing the high-frequency signal branched to the other output terminal and the high-frequency signal received by the transmitting/receiving antenna and outputting an intermediate-frequency signal,

wherein a line length between the branching device and the modulator or a line length between the branching device on the side of the mixer and the modulator is set so that δ

=±

π

in which δ

is a phase difference at a center frequency between a signal Wa₂, which is a high-frequency signal which passes through the modulator in the OFF state, and a signal Wb₂, which is a high-frequency signal which passes the mixer and the circulator from the other output terminal of the branching device to the output terminal of the modulator and is reflected on the output terminal of the modulator.

40. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 34;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

43. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 40, wherein the radar apparatus is used for detecting the objective.

46. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 40, wherein the radar apparatus is used for detecting the objective.

35. A high-frequency transmitter-receiver comprising:

a high-frequency oscillator for generating a high-frequency signal;

a branching device connected to the high-frequency oscillator, for branching a high-frequency signal and outputting the branched high-frequency signals to one output terminal and the other output terminal;

a modulator connected to the one output terminal, for modulating the high-frequency signal branched to the one output terminal and outputting the transmission high-frequency signal;

a circulator having a first terminal, a second terminal and a third terminal around a magnetic element, for outputting a high-frequency signal inputted from one of the terminals in the recited order, from a next terminal adjacent to the one terminal and inputting an output from the modulator to the first terminal;

a transmitting/receiving antenna connected to the second terminal of the circulator; and

a mixer connected between the other output terminal of the branching device and the third terminal of the circulator, for mixing the high-frequency signal branched to the other output terminal and the high-frequency signal received by the transmitting/receiving antenna and outputting an intermediate-frequency signal,

wherein a branching ratio R of the branching device is expressed by R=Pb₁/Pa₁ (R;

an real number of 0 or more) and is set to R<

1, in which Wa₁ is a high-frequency signal to be outputted to one output terminal of the branching device, Pa₁ is an intensity thereof, Wb₁ is a high-frequency signal to be outputted to the other output terminal of the branching device and Pb₁ is an intensity thereof.

36. The high-frequency transmitter-receiver of claim 35, where in the branching ratio R is set to R=A₁/(B₁·

B₂·

B₃), in which A₁, B₁, B₂ and B₃ are a transmission coefficient of the high-frequency signal to transmit through the modulator in the OFF state, a transmission coefficient of the high-frequency signal to transmit between the two input terminals of the mixer, a transmission coefficient of the high-frequency signal to transmit between the third terminal and the first terminal of the circulator, and a reflection coefficient of the high-frequency signal to be reflected on the output terminal of the modulator, respectively.

37. The high-frequency transmitter-receiver of claim 35, wherein either a line length between the one output terminal of the branching device and the modulator or a line length between the other output terminal of the branching device and the modulator through the mixer and the circulator is set so that δ

=±

π

in which δ

is a phase difference at a center frequency between signal Wa₂, which is a high-frequency signal which passes through the modulator in the OFF state and signal Wb₂, which is a high-frequency signal which passes through the mixer and the circulator from the other output terminal of the branching device to the output terminal of the modulator and is reflected on the output terminal of the modulator.

41. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 35;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

44. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 41, wherein the radar apparatus is used for detecting the objective.

47. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 41, wherein the radar apparatus is used for detecting the objective.

38. A high-frequency transmitter-receiver comprising:

first and second circulators each having a first terminal, a second terminal and a third terminal around a magnetic element, for outputting a high-frequency signal inputted from one of the terminals, from either one of the terminals adjacent to the one terminal in the recited order;

a high-frequency oscillator connected to the first terminal of the first circulator, for generating a high-frequency signal;

a modulator connected between the second terminal of the first circulator and the first terminal of the second circulator, for transmitting the high-frequency signal to the side of the second circulator or for reflecting the high-frequency signal to the first circulator in response to a pulse signal;

a transmitting/receiving antenna connected to the second terminal of the second circulator; and

a mixer connected between the third terminal of the first circulator and the third terminal of the second circulator, for mixing the high-frequency signal reflected on the modulator and inputted from the third terminal of the first circulator and the high-frequency signal received by the transmitting/receiving antenna and inputted from the third terminal of the second circulator, and outputting an intermediate-frequency signal,

wherein δ

=±

π

in which δ

is a phase difference at a center frequency between a signal Wa, which is a high-frequency signal which passes through the modulator in the OFF state, and a signal Wb, which is a high-frequency signal which passes the mixer and the second circulator from the third terminal of the first circulator to the output terminal of the modulator and is reflected on the output terminal of the modulator.

39. The high-frequency transmitter-receiver of claim 38, wherein an attenuator or a variable attenuator is interposed between the first circulator and the mixer.

42. A radar apparatus comprising:

a high-frequency transmitter-receiver of claim 38;

and

a range information detector for processing an intermediate-frequency signal outputted from the high-frequency transmitter-receiver and detecting range information to an objective.

45. A radar-apparatus mounted vehicle comprising the radar apparatus of claim 42, wherein the radar apparatus is used for detecting the objective.

48. A radar-apparatus mounted small-sized boat comprising the radar apparatus of claim 42, wherein the radar apparatus is used for detecting the objective.