JPS5858030B2 - High frequency electromagnetic field sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency electromagnetic field sensor, that is, a means for detecting the magnitude of high frequency energy or its distribution.

Traditionally, to detect electromagnetic fields in a cavity resonator, such as an oven, the conductor wall has either a small aperture through which the electric field is detected by a probe, or a loop is used to detect the magnetic field. method is known.

However, in ovens where the internal electromagnetic field distribution changes depending on the load or Stark rotation, it is difficult to detect the average electromagnetic field strength using a small number of the above sensors. Ta.

The object of the present invention is to realize a sensor that detects the energy distribution of a high-frequency electromagnetic field by a simple means.

In order to achieve the above object, the present invention provides an electric field sensor consisting of a conductor piece and a detection diode that are capacitively coupled to an electric field perpendicular to the opening surface of a metal container, and a conductor piece that loop-couples to a magnetic field parallel to the opening surface, and a detection diode. The magnetic field sensor is composed of two sets of magnetic field sensors consisting of detection diodes, and the magnitude of high frequency energy near the opening is detected by signals from the three types of sensors.

FIG. 1 shows the configuration of an embodiment of a sensor according to the present invention.

In the same figure, 1 is the X-direction component of the magnetic field existing in space,
2 is also the Y direction component, 5 is also the Z direction component of the electric field,
4 is an electromagnetic field coupling window, 5 is a high frequency electromagnetic sensor case, 6
1 is an antenna pattern for electric field coupling, and 7 and 8 are antenna patterns for magnetic field coupling, and the antenna portion of the sensor is constituted by these antenna patterns.

The following circuit is used to convert the electromagnetic field coupled with the antenna into DC output.

9 is a DC output detection circuit for HX, 14 is for HY, and 16 is a DC output detection circuit for EZ.

In the detection circuit 9, 10 is a detection diode, 11 is a capacitor for temporally smoothing the detection output, 12 is a variable resistor for adjusting the output voltage, and 13 is an HX output terminal.

15 is the output terminal of HY, 17 is the LZ detection circuit, choke coil added to 16, 18 is the bypass capacitor, 1
9 is an output terminal of the EZ.

The strength of the electromagnetic field that exists in space due to these circuits is H
It can be detected as three DC components: X, HY, and EZ.

That is, according to the high-frequency electromagnetic field sensor of the present invention, near the aperture, the high-frequency energy E of By multiplying each output by an appropriate coefficient and adding it, you can obtain a signal proportional to the magnitude of its energy.

Sensitivity can be adjusted by changing the dimensions of the electromagnetic field coupling window 4 at the center of the sensor, depending on the strength of the electromagnetic field component.
It also serves as protection for the detection diode.

When using such an electromagnetic field sensor to measure the electromagnetic field in a space inside a metal container, for example when measuring the electromagnetic field distribution inside a microwave oven, lead wires are usually required. , it is difficult to measure points in space, and it is convenient to measure on the wall of the oven.

At the oven wall, all electric fields parallel to the wall are zero, and only the perpendicular electric field can be detected.

At a position away from the wall, there is also an electric field parallel to the wall, and the magnitude of this is proportional to the current or magnetic field flowing through the wall, so two orthogonal magnetic field components parallel to the wall are detected and an appropriate coefficient is calculated. Multiplying the values and adding them will represent the magnitude of the electric field in the vicinity of that point.

By providing a large number of such measurement points on the wall surface and determining the deviation of the measured values, it is possible to deal with uneven heating.

FIG. 2 shows an embodiment of an electromagnetic field sensor structure in which the electromagnetic field sensor of the present invention is fixed to a wall inside a container and the electromagnetic field distribution is measured.

Figure 2 shows the coupling antenna 6.7.8 and the detection diode 1.
0 is built into the case.

In FIG. 2, 20 is the mounting part of the electromagnetic field sensor, 21
2 is a dielectric substrate supporting an electromagnetic field antenna pattern 6.7°8, and 22 is a back cover of the electromagnetic field case.

This electromagnetic field sensor is placed inside the microwave oven,
Figure 3 shows a device designed to measure electromagnetic field distribution.

In FIG. 3, 23 is a microwave oven, 24 is an oven,
25 is an electromagnetic field sensor of the present invention.

Nine electromagnetic field sensors 25 are arranged at appropriate intervals.

In this example, the same effect can be achieved by placing it on the bottom of the oven, or fixing it to the side wall or ceiling.

The part of the electromagnetic field sensor that is installed in the oven is the part shown in Figure 2, and the other parts are taken out using the output lead wire, and the distribution level can be recorded by recording each output level with a multi-pen recorder or by displaying it on a flat surface. can be known.

In this way, the high frequency electromagnetic field sensor of the present invention can be said to be an effective method when measuring the strength of an electromagnetic field in a space on a nearby wall surface.

The detection diode 10 is selected from one with relatively high detection sensitivity in the frequency band to be detected, and variations in the individual detection characteristics due to variations in the characteristics of the detection diode 10 and dimensional errors in the antenna patterns 6, 7, 8, etc. variable resistance 1
2 can be adjusted and calibrated.

Figure 4 shows the output characteristics of one electromagnetic field detector installed in a microwave oven.

In the output characteristics when the microwave oven is turned on and left for a while, 26 corresponds to the electric field component and 27.28 corresponds to the magnetic field component.

If such characteristics can be obtained from a large number of electromagnetic field sensors placed on the bottom of the oven, it will be possible to know the uniformity of the electromagnetic field distribution that causes uneven heating, and it will be possible to judge the quality of the oven design.

The parts used in this example were (the dielectric substrate 21 is a glass epoxy substrate, the detection diode is a 0.1-3 GHz band Si
GaAs diodes are also available (e.g. mixer diodes sold at a unit price of 60 yen), and both are commercially available at low prices as general-purpose products.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the principle of the present invention, FIG. 2 is a perspective sectional view of some embodiments of the present invention, and FIG. 3 is a diagram of the high-frequency electromagnetic field sensor of the present invention placed on the bottom of a commercially available microwave oven. FIG. 4 shows the output characteristics of the high frequency electromagnetic field sensor. 4... Electromagnetic field coupling window, 5... Case,
6... Antenna pattern for electric field coupling, 7 8... For magnetic field coupling.

Claims (1)

[Scope of Claims] 1. An electric field sensor comprising at least one opening provided in a part of the surface of a sealed metal container and comprising a conductor piece and a detection diode that capacitively couples to an electric field perpendicular to the surface; 2 consisting of mutually orthogonal conductor pieces loop-coupled to a magnetic field parallel to the surface and respective detection diodes.
A high-frequency electromagnetic field sensor that is composed of a set of magnetic field sensors and detects the magnitude of ultra-high frequency energy near an opening using signals from the three types of sensors described above. 2. The high-frequency electromagnetic field sensor according to item 1, wherein the capacitively coupled conductor piece and the loop-coupled mutually orthogonal conductor pieces are constructed on the same substrate.