Communications: directive radio wave systems and devices (e.g. – Directive – Including antenna pattern plotting
Reexamination Certificate
1999-04-07
2001-06-19
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including antenna pattern plotting
C343S703000
Reexamination Certificate
active
06249248
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic wave measuring apparatus and a method for evaluating and measuring radiation directivity of an electromagnetic wave using the same.
2. Description of the Related Art
Generally, an electromagnetic wave radiated from an antenna or an electromagnetic wave radiated from a device itself are evaluated for its energy and directivity in a method in which a device to be evaluated is placed using a large anechoic chamber and an electromagnetic wave thereof is received and observed at a sufficiently distant position. The reason for using the RF anechoic chamber is to prevent an electromagnetic wave from entering from the outside and to eliminate an effect of a reflected wave upon the measurement. The reason for performing the measurement at a sufficiently distant position is to measure the radiated electromagnetic wave in the far field and to reduce an error caused by a changed sensitivity due to an effect of the device to be evaluated upon a receiving antenna.
This method, however, involves very large evaluating equipment (for example, 10 m×10 m×10 m in size). Thus, a near field measuring method (Tasuku Teshirogi: “Measurement in Neighborhood Field for Antenna”, Shingakusi, vol.62, no.10, pp.1145-1153, October 1979) has been developed as a method for evaluating an antenna. The near field measuring method includes: (a) plane scanning; (b) cylindrical plane scanning; and (c) spherical scanning. The methods (b) and (c) imply the extreme difficulty of accurately measuring the perimeter of a device to be evaluated and involve a large amount of operation required for correction of a probe antenna and for conversion from a near field to a far field, so that these methods have not been brought into practice widely. Thus, the method (a) has been used generally.
However, the above-mentioned conventional, (a) plane scanning method, has a disadvantage that it can be adapted only to an antenna with a relatively narrow directivity such as an aperture antenna. The cause thereof is that the method performs conversion from the near field to the far field on the assumption that a source of an electromagnetic wave is planar.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electromagnetic wave measuring apparatus capable of accurately estimating radiation directivity from an antenna having a relatively wide directivity or from an antenna integral-type communication device and a method for evaluating and measuring the radiation directivity of an electromagnetic wave.
The electromagnetic wave measuring apparatus of the present invention comprises a probe scanner movable in the x direction, the y direction, the z direction and a rotating direction; a fixed probe antenna, a relative position of which does not change against a measured object; a control/record and operation/display unit; an interference measuring unit; and a level detector. The probe scanner has a sensor for measuring a three-dimensional shape and a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave attached thereto.
A method for evaluating and measuring radiation directivity of an electromagnetic wave with an electromagnetic wave measuring apparatus of the present invention has the steps of: measuring and recording an object shape distribution of an antenna integral-type communication device to be observed with a sensor for measuring a three-dimensional shape, and measuring and recording a scanning distribution of interference complex data between a detected signal with a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave and a detected signal with a fixed probe antenna, a relative position of which does not change against a measured object, as a two-dimensional electric field distribution or a two-dimensional magnetic field distribution, based on movement with a predetermined step as a minimum movement unit; displaying the object shape distribution and the two-dimensional electric field distribution or the two-dimensional magnetic field distribution in a superimposed state on a screen; specifying a line area and a plane area of the antenna integral-type communication device for the display screen; deriving a complex current distribution of the specified line area and plane area from the object shape distribution and the two-dimensional electric field distribution or the two-dimensional magnetic field distribution; deriving directivity from the object shape distribution and the complex current distribution of the line area or the plane area; and displaying the derived directivity.
The step of deriving a complex current distribution of the specified line area and plane area from the object shape distribution and the two-dimensional electric field distribution or the two-dimensional magnetic field distribution may include performing predetermined weighting for the specified line area and the plane area.
An electromagnetic wave measuring apparatus of the present invention comprises a probe scanner movable in the x direction, the y direction, the z direction and a rotating direction; a control/record and operation/display unit; and a network analyzer. The probe scanner has a sensor for measuring a three-dimensional shape and a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave attached thereto.
A method for evaluating and measuring radiation directivity of an electromagnetic wave with an electromagnetic wave measuring apparatus of the present invention has the steps of: measuring and recording an object shape distribution of an antenna to be observed with a sensor for measuring a three-dimensional shape, and measuring and recording a complex transmission characteristic which is a two-dimensional electric field distribution or a two-dimensional magnetic field distribution by adding an RF output signal of a network analyzer to an antenna to be observed, receiving an electromagnetic wave radiated from the antenna with a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave and inputting an RF input of the electromagnetic wave to the network analyzer, based on movement with a predetermined step as a minimum movement unit; displaying the object shape distribution and the complex transmission characteristic in a superimposed state on a screen; specifying a line area of the antenna for the display screen; deriving a complex current distribution of the specified line area from the object shape distribution and the complex transmission characteristic; deriving directivity from the object shape distribution and the complex current distribution of the line area; and displaying the derived directivity.
Therefore, the electromagnetic wave measuring apparatus or the evaluating and measuring method of the electromagnetic wave irradiation directivity with the electromagnetic wave measuring apparatus of the present invention can be used to accurately measure an extreme near field with plane scanning and shape of a device to be evaluated, thereby correctly measuring irradiation directivity from an antenna having a relatively wide directivity or an antenna integral-type communication device.
Additionally, an electromagnetic wave state in an antenna integral-type communication device such as a portable telephone, which heretofore could not be evaluated without using large measuring equipment such as an RF anechoic chamber, can be evaluated using very compact measuring equipment.
REFERENCES:
patent: 4968983 (1990-11-01), Maeda
patent: 5410319 (1995-04-01), Lopez et al.
patent: 5410324 (1995-04-01), Bolomey et al.
patent: 5432523 (1995-07-01), Simmers et al.
Tasuku Teshirogi, “Near-Field Antenna Measurement,” Shingakusi, vol. 62, No. 10, (Oct. 1979), pgs. 1145-1153.
Advantest Corporation
Blum Theodore M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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