Communications: radio wave antennas – Antennas – With spaced or external radio wave refractor
Reexamination Certificate
1999-07-02
2001-01-09
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With spaced or external radio wave refractor
C343S753000
Reexamination Certificate
active
06172648
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a directional coupler using a dielectric guide, and to an antenna device and a transceiver using the directional coupler.
2. Description of the Related Art
Conventionally, a dielectric guide, comprising a dielectric strip provided between two conductive plates, is used as a guide for transmission in the milliwave band and the like. When forming a milliwave circuit using such dielectric guides, a directional coupler is used in a portion where electrical power is split between two dielectric guides.
A conventional directional coupler using dielectric guides comprises two dielectric strips, having a linear portion and a curved portion, which are provided at a predetermined distance apart between two conductive plates. The dielectric strips are arranged close together and the dielectric guides are coupled at this closely arranged portion.
A milliwave radar is an example of the milliwave circuit using dielectric guides described above. An antenna device used in a milliwave radar comprises a dielectric lens and a primary emitter provided at the focal point of the dielectric lens.
However, since the direction of the antenna in the conventional milliwave radar is fixed, in certain conditions it is not possible to achieve the intended sensitivity and measurements, as will be explained below. For instance, as shown in
FIG. 22
, when a vehicle is traveling on a multi-lane road, it is not possible to determine immediately whether other vehicles in front of it are traveling in the same lane based only on waves reflected from the other vehicles. That is, in
FIG. 22
, when the vehicle Cm emits a beam B
2
, it picks up not only waves reflected from the vehicle Ca which is traveling in front, but also waves reflected from the vehicle Cb which is traveling in the opposite lane. Furthermore, as shown in the example of
FIG. 23
, when the vehicle Cm emits a beam B
1
in the forward direction, it is unable to detect the vehicle Ca which is traveling in front in the same lane. Moreover, as shown in
FIG. 24
, when traveling on an curving road, even though the vehicle Cm emits a beam B
1
in the forward direction, it cannot detect the vehicle Ca in front of it.
One conceivable solution is to provide an antenna device, combining a primary emitter and a dielectric lens, in which the direction of the beam is tilted by changing the position of the primary emitter. In order to change the position of the primary emitter, the configuration should be arranged so that the dielectric guide connecting to the primary emitter and the other dielectric guide connecting to the circuit can be relatively displaced while remaining coupled with low loss. To achieve this, the configuration of the directional coupler using dielectric guides described above need only be arranged so that two dielectric guides can be relatively displaced.
However, the separated positions (separated faces) of the two dielectric guides of the directional coupler are parallel to the two dielectric strips provided closely together. With this configuration, the end faces of the conductive plates on either side of the dielectric strips are provided parallel to the direction of propagation of the electromagnetic waves of the two dielectric guides, and consequently the path of the current flowing through the conductive plates is broken at the end face portions of the conductive plates, causing reflection. As a result, there are problems such as the creation of unwanted modes other than the propagation mode, increased loss, or an inability to obtain desired characteristics of the directional coupler, etc.
The above example describes case where the two dielectric guides of the directional coupler portion are relatively displaced, but the directional coupler can be used when forming a single device incorporating circuit modules using dielectric guides, to couple the dielectric guides between the circuit modules. In this case too, the path of the current flowing through the conductive plates is broken between the circuit modules, causing reflection. As a result, there are problems of increased loss and inability to obtain desired signal transmission characteristics between the circuit modules.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a directional coupler comprising two separated dielectric guides, wherein the above problems of reflection and loss are eliminated.
To provide dielectric strips of two dielectric guides of a directional coupler close together in a predetermined region only, a bend must be provided in dielectric guide portions joined to the directional coupler. However, to reduce loss due to conversion from the LSM mode to the LSE mode, for instance, the radius of curvature of the bend must be large. As a result, the overall size of the device is increased, and when it is used to form an antenna device, the moving portion cannot be made light, making it difficult to deflect the beam quickly. On the other hand, when the space between opposing faces of the two conductive plates clasping the dielectric strip is made narrow, although the radius of curvature of the bend can be set freely as long as dielectric guides transmitting only in the LSM01 mode as used, the coupling portion must be made long in order to obtain adequate coupling, inevitably increasing the overall size of the device and making it difficult to lighten the moving portion. If the space between the dielectric strips in the coupling portion is extremely narrow, strong coupling can be obtained, but the characteristics of the directional coupler will greatly depend on the precision of the positioning of the two separated dielectric guides.
It is another object of the present invention enable the directional coupler and a device using the directional coupler to be easily miniturized, to enable the mass of the moving portion to be reduced, and to enable the direction of the beam to be deflected quickly.
The directional coupler of the present invention comprises first and second dielectric guides, each comprising a dielectric strip provided between two conductive plates, arranged with the end faces of the conductive plates touching or not touching, and the dielectric strips of the first and second dielectric guides are provided substantially parallel to each other in the vicinity of the end faces of the conductive plates, so that the first and second dielectric guides are structurally separate. Furthermore, a groove is provided in an end face of the conductive plates of one of the first and second dielectric guide, the groove having a short-circuiting face in a position at a distance from the electrode faces of approximately an integral multiple of half the wavelength of a propagated wave.
With this configuration, the electrode faces in the portion where the end faces of the conductive plates of the first and second dielectric guides are aligned function as an equivalently continuous portion. Therefore, although the two dielectric guides are separated by the conductive plate portions, there is almost no loss in this space. Furthermore, since there is almost no reflection, no spurious modes are caused by reflection.
Furthermore, in the present invention, a position at a distance from the electrode face of approximately an integral multiple of half the wavelength of a plane wave, which travels in a direction such that it has a wave-number vector component equal to a phase constant of a transmitted wave propagating through the dielectric guides, in the direction of a transmitted wave propagating through the dielectric guides, is a short-circuiting face.
A plane wave, propagating through the aligned portion of the end faces of the conductive plates of the first and second dielectric guides, travels in a direction determined according to its size and the size of a transmission wave, propagating along the length of the dielectric guides. That is, the size of the plane wave (wave-number k) is predetermined, and when the plane wave is projected in the tra
Kitamori Nobumasa
Kondou Nobuhiro
Nishida Hiroshi
Nishiyama Taiyo
Saitoh Atsushi
D Chuc Tran
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Wong Don
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