Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
2002-01-29
2003-07-22
Nguyen, Hoang (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
C343S772000
Reexamination Certificate
active
06597322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a primary radiator for use in a beam scanning antenna in the microwave or millimeter wave band, and more particularly to a primary radiator capable of moving an electromagnetic wave output part in a two dimensional plane without causing unwanted leakage of a high frequency signal, and a phase shifter and beam scanning antenna using the same.
2. Description of the Related Art
A variety of beam scanning antennas using electromagnetic beams in the microwave or millimeter wave band have been proposed in the prior art. There are two major methods of beam scanning: mechanical beam scanning and electronic beam scanning.
In the mechanical beam scanning method, beam scanning is performed by moving a portion of an antenna that has a given directionality or by moving the entire antenna. According to this method, the construction is simple because usually one antenna is moved to scan one beam. However, the provision of the mechanical movement involves the problem that high speed beam scanning is difficult in the case of a large antenna.
The electronic beam scanning is classified into two types: one that uses an array antenna constructed from an array of antenna elements and scans the beam by controlling the phases of the high frequency signals fed to the respective elements by means of phase shifters, and the other that uses a plurality of antennas having different directionalities and scans the beam by switching among them by means of switches. These types of beam scanning can accomplish high speed beam scanning because they do not require the provision of mechanical movements, but the problem is that the phase shifters and the switches are expensive, limiting the use of these types of antennas.
Latching ferrite phase shifter are commonly used as the phase shifters for electronic beam scanning type antennas. Since this type of phase shifter usually controls the phase in eight steps, i.e., in increments of 45 degrees, there arises the problem that, with this type, the phase cannot be controlled continuously. It is also said that this type of phase shifter has the problem that the response time is slow compared with the switch.
On the other hand, PIN diodes are commonly used as the switches for switching among the antennas. However, the PIN diode is a switch that switches between open and closed states, and therefore has the problem of large insertion loss. Another problem is high cost, because as many switches are required as there are antennas.
In recent years, with advances in semiconductor fabrication technology, phase shifters and switches have begun to be fabricated in MMIC (Microwave Monolithic Integrated Circuit) form, promising to increase the performance of beam scanning antennas, but since the MMIC is also expensive, there is a need to provide an inexpensive phase shifter that can control the phase.
In view of this, the applicant has proposed in Japanese Unexamined Patent Publication JP-A 2001-127524 (2001) a beam scanning antenna comprising a primary radiator placed between two parallel metal plates, a wave collector constructed from a dielectric lens or a reflector or the like, and a plurality of slots formed in one of the parallel plates. According to this beam scanning antenna, a high frequency spherical wave signal radiated from the primary radiator propagates through the space between the parallel plates, and is converted into a plane wave by the wave collector. Further, the positional relationship between the primary radiator and the wave collector is varied and, using this as a phase shifter, the tilting of the electromagnetic wave phase can be controlled. The beam can be scanned by externally radiating the high frequency signal, whose phase has been controlled by the phase shifter, directly through the slots formed in one of the parallel plates, or by feeding the high frequency signal to another antenna element mounted outside the slots. This beam scanning antenna can be fabricated at low cost because it is constructed using the parallel plates, the wave collector forming the phase shifter, and the primary radiator.
The beam scanning antenna proposed in JP-A 2001-127524 by the applicant requires that either the wave collector or the primary radiator or both be moved to vary the positional relationship between the wave collector and the primary radiator. Both the wave collector and the primary radiator are placed between the parallel plates, and the high frequency spherical wave signal radiated from the primary radiator, after being converted into the plane wave by the wave collector, is fed to the slots acting as radiating elements or feed windows to the outside. Therefore, to allow the wave collector or the primary radiator to move, a prescribed gap must be provided between each parallel plate and the wave collector or the primary radiator.
However, when a gap is provided between each parallel plate and the wave collector, the sum of the high frequency signal converted into the plane wave by the wave collector and the high frequency spherical wave signal passed unchanged through the gap between each parallel plate and the wave collector is fed to the slots. In this case, the spherical wave and the plane wave arrive out of phase at the slot feed point; as a result, in some instances, the phase of the high frequency signal fed to the slots may be disturbed.
On the other hand, when a gap is provided between each parallel plate and the primary radiator, since the wave source consists only of the primary radiator which has directionality, the phase is relatively unaffected. However, a high frequency transmitter/receiver is usually connected to the primary radiator, and the transmitter/receiver is a precision component and relatively large in weight; hence the problem that moving the primary radiator for beam scanning tends to increase the chance of transmitter/receiver failure.
SUMMARY OF THE INVENTION
The present invention has been devised to overcome the above-outlined problems of the prior art, and an object of the invention is to provide a phase shifter comprising a wave collector and a primary radiator, and a primary radiator for use in a beam scanning antenna that uses such a phase shifter, wherein the primary radiator is constructed as a component structurally independent of a transmitter/receiver connected to it so that only the primary radiator can be moved without moving the transmitter/receiver, thereby achieving the construction of an inexpensive, high-reliability, and high-performance phase shifter and beam scanning antenna using such a primary radiator.
Another object of the invention is to provide a phase shifter that is constructed by arranging the above primary radiator and wave collector between parallel plates, and that can control the phase continuously by varying the positional relationship between the primary radiator and the wave collector.
A further object of the invention is to provide a beam scanning antenna which includes slots formed in one of parallel plates that form part of the phase shifter constructed using the above primary radiator, and which scans the beam by radiating a high-frequency signal directly through the slots after controlling the phase by the wave collector, or by feeding through the slots the high frequency signal to another antenna that is mounted outside the parallel plates.
The inventor has conducted extensive studies on the previously described problems and has found that the problems associated with the prior art can be solved by employing the following configuration.
The invention provides a primary radiator comprising:
a base part in an upper surface of which a groove having a width of ½ to {fraction (1/1)} of signal wavelength of a high frequency signal and a depth approximately equal to ¼ of the signal wavelength, and whose inner wall is formed of an electrically conductive material, is formed as a waveguide for the high frequency signal; and
a moving part formed of an electrically conductive material and placed above
Hogan & Hartson LLP
Kyocera Corporation
Nguyen Hoang
LandOfFree
Primary radiator, phase shifter, and beam scanning antenna does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Primary radiator, phase shifter, and beam scanning antenna, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Primary radiator, phase shifter, and beam scanning antenna will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3107011