JPH0324633B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an incident interference rejection ability evaluation device suitable for evaluating the rejection ability of a receiver against interference electric fields. Recently, the evaluation of the ability of a receiver to eliminate incident interference, that is, the noise resistance characteristics of a receiver against the influence of surrounding electromagnetic fields, has become a problem. This evaluation is performed by the Jatsky method as one means, but this has various problems as described later. 1 and 2 show examples of the configuration of an evaluation system using the Jacksky method, with FIG. 1 showing the configuration of a strip line (parallel conductor), and FIG. 2 showing a block diagram of the evaluation system. The strip line consists of a lower conductor 1 and pillars 4a, 4b, 4 made of insulating material on the lower conductor 1.
It consists of an upper conductor 2 held in parallel at points c and 4d. Both ends 1a and 1b of the lower conductor 1 and both ends 2a and 2b of the upper conductor 2 are narrowed as shown in the figure, and the ends 1a and 2a, 1b and 2b correspond to each other.
are mechanically connected in a tapered manner through an insulator. The dimensions of the strip line are L _a = 2000mm, L _b = 2750mm,
It is illustrated with W ₁ =900 mm, W ₂ =600 mm, and H = 800 mm. One combined end of the strip line constitutes a feeding end 3a for applying a disturbance signal to the parallel conductors 1 and 2, and is connected to a matching circuit 10 via a feeding coaxial line (not shown). The interfering signal is the matching circuit 10
The signal is supplied from a disturbance signal generator 11 which is provided via a signal generator. The other coupling end 3b is terminated with a terminating resistor 12. A receiver to be measured 6 is placed on the lower conductor 1 of the strip line via an insulating plastic or wooden stand 5, and a receiver 6 to be measured is placed on the lower conductor 1 of the strip line via a stand 5 made of plastic or wood for insulation. Power is supplied. A desired signal generator 14 is further connected to the receiver 6 via an antenna blocking filter 6, and the desired signal is applied to the receiver 6. An audio frequency voltmeter 17 is provided and the output signal of the receiver 6 is taken out. With the above configuration, the rejection ability of the receiver 6 for incident interference can be measured by increasing the level of the interference signal generator 11 from a low level, and according to this method, the rejection ability in the frequency range of 150KHz to 150MHz can be measured. It is possible to evaluate abilities. By the way, it is said that in an unbalanced driven line such as the above-mentioned strip line, the length of one circumference of the line operates as an antenna at a frequency corresponding to one wavelength. When a strip line operates as an antenna, electromagnetic waves are radiated to the outside, reflected by reflectors around the strip line, such as walls, the person measuring the measurement, or the measuring device, and then re-entering the strip line. . Therefore,
The electric field inside the strip line cannot maintain a predetermined strength, making appropriate evaluation difficult. The appropriate electric field strength inside the stripline is illustrated by the calibration curve shown in FIG. In this method, a metal plate measuring 20 cm on a side is placed at a height of 1 cm above the lower conductor of a strip line, and the high-frequency voltage of the metal plate relative to the lower conductor is measured using an appropriate measuring device, such as a high-frequency millivoltmeter. indicates the detection voltage (mV) of the metal plate, and the horizontal axis indicates the frequency (MHz). A in the figure is the calibration curve when the no-load voltage of the unmodulated measurement transmitter is 10V. It is said that it must be within a range of ±2 dB centered on curve A. However, if electromagnetic waves are re-injected, the voltage value of the metal plate will deviate from the above range, making it difficult to properly evaluate the rejection ability of the receiver. This is explained in more detail in FIG. FIG. 4 shows an incident interference rejection ability evaluation device in which the strip line explained in FIG. , width 3.0m, height 2.5m. The frequency characteristics of the detected voltage (voltage of the metal plate) in the above configuration are shown in FIG. As is clear from the figure, the detected voltage of the metal plate greatly deviates from the permissible range of the calibration curve described in FIG. SUMMARY OF THE INVENTION Therefore, the present invention aims to improve the above-mentioned drawbacks of the prior art, and its object is to provide an incident interference rejection ability evaluation device that can appropriately maintain the electric field strength inside the strip line. A feature of the present invention for achieving this purpose is that both ends of the upper conductor and lower conductor, which are parallel to each other, are mechanically connected in a tapered manner through an insulator, and a disturbance signal feeding end is formed at one end, and a terminating resistor connecting end is formed at the other end. In an incident interference rejection ability evaluation device that evaluates the interference rejection ability of a test device by simulating a disturbing electromagnetic field by simulating a disturbing electromagnetic field by simulating a disturbing electromagnetic field by placing a strip line in a closed metal case, the inside surface of the metal case is The strip line is placed in the metal case such that the magnetic radio wave absorber to be attached and the lower conductor of the strip line are electrically connected to the metal case via damping resistors at both ends of the parallel portion of the lower conductor. a power feeding coaxial line having one end connected to the disturbance signal feeding end of the strip line and the other end passing through the metal case and connected to an external device for supplying the disturbance signal; An incident interference rejection ability evaluation device having an insulator with a large high frequency loss that electrically insulates between a wire and a metal case, and a resistance buffle provided in the strip line opposite to the tapered part of the line. be. Embodiments of the present invention will be described below with reference to the drawings. 6 and 7 show an embodiment of the incident interference rejection ability evaluation device according to the present invention, in which FIG. 6 shows a plan view and FIG. 7 shows a sectional view taken along the line AA in FIG. 6. In the figure, reference numeral 20 is a radio anechoic box having a radio wave absorber 30 attached to the entire inner surface of a metal case 19 having a substantially rectangular parallelepiped shape, and has a door 21 for allowing the user to enter and exit or the measuring device to be carried in and out. Radio wave absorber 3
0, the size of the anechoic box and the measurement frequency are
Since the frequency is 150MHz or less, a thin ferrite radio wave absorber is suitable. The dimensions of the anechoic box 20 are, for example, length L _c 3 m, width W _c 2.6 m, and height H _c
The length is 2.6m, and the strip line shown in Figure 1 will be installed within it. As shown in FIG .
The lower conductor 1 is placed on an insulating holder 60 so as to coincide with one diagonal line of 0a, and the distance between the upper conductor 2 of the strip line and the ceiling of the anechoic box 20 is equal to the parallel conductor 1 of the strip line. ,2
The distance is set to be greater than the distance between the two. The purpose of arranging them diagonally is to make the anechoic box smaller and to increase the working area inside the anechoic box, and the reason why the distance between the strip line and the ceiling of the anechoic box is large is to make the anechoic box smaller. This is to prevent a drop in impedance. The holding stand 60 is made of wood, for example, and considering the influence of the floor surface 20a on the electric field strength within the strip line,
It is desirable that the height h be approximately 70 cm. This height h satisfies the above requirement of increasing the distance between the strip line and the ceiling of the dark box. Grounding conductor plates 70a and 70b, one end of which is grounded to the metal case 19 of the anechoic box 20 , are provided on both sides of the holding base 60, and the corresponding ends of each conductor plate and the parallel portion of the lower conductor 1 of the strip line are connected to each other. are electrically coupled via damping resistors 80a and 80b, respectively. A damping resistor of around 200 (Ω) is desirable. As shown in FIG. 6, one end of a power feeding coaxial cable 40 for supplying a disturbance signal is connected to the feeding end 3a of the strip line. coaxial cable 4
The other end of 0 is led out of the anechoic box 20 through electrical insulation between it and the anechoic box 20 by an insulating ring 50, and is connected to an external device (interference signal generator 11 in FIG. 2) that supplies a disturbance signal. be done. insulation ring 50
As the material, a material with high electrical insulation and high frequency loss, such as ferrite or dust core, is used. The insulating ring 50 is provided in close contact between the coaxial cable 40 and the anechoic box 20 , and its dimensions are, for example, 50 mm to 100 mm thick, 16 mm outer diameter, and 8 mm inner diameter.
are used. Inside the strip line, as shown in Figure 7,
Resistor buffles 90a and 90b are provided opposite the tapered portion of the strip line. The resistor baffle is formed of an insulator 91 so as to substantially partition the tapered part and the parallel conductor part of the strip line.
a, 91b. FIG. 8 shows an experimental example of the incident interference rejection ability evaluation apparatus having the above configuration. Note that the specifications in this experimental example are as follows.

[Table] As is clear from Figure 8, the tolerance range (±2 dB) of the calibration curve A in Figure 3 is satisfied, and the dip and peak (portions outside the tolerance range) in Figure 5 are completely removed. Can be done. According to the configuration of the present invention, the tolerance range of the calibration curve is satisfied for the following reasons. (1) Since the strip line is placed inside an anechoic box equipped with a radio wave absorber, the effect on the electric field strength within the line due to re-injection of electromagnetic waves at frequencies higher than the frequency at which the strip line operates as an antenna is suppressed. thing. (2) Since the coaxial cable for supplying the interference signal is electrically insulated from the anechoic box, a kind of distributed constant circuit formed by the strip line, the wall of the anechoic box, and the coaxial cable becomes an open circuit, which causes resonance. As a result, the large dip that occurs near 10MHz can be removed. Note that since a material with a high high frequency loss such as ferrite is used as an insulator between the coaxial cable and the anechoic box, there is no risk of high frequencies leaking from inside. (3) Since the strip line is grounded to the anechoic box via a damping resistor, it is possible to suppress resonance caused by a type of distributed constant circuit that is formed between the strip line and the anechoic box when directly grounded, and It is possible to remove large deeps that occur in This is Figure 9A, Figure 9B, Figure 9
This is made clear from Figure C. FIG. 9A shows the case where the strip line is directly grounded without using a resistor, FIG. 9B shows the case where it is grounded through a 200Ω damping resistor, and FIG. 9C shows the case where it is electrically floating. As is clear from these experimental examples, when directly grounded, the dip near 30MHz is not improved, and when electrically floated, it falls within the allowable range, but a large dip occurs near 7MHz. . (4) Since a resistor buffle is provided in the strip line, it is possible to suppress the standing waves generated in the line by the electromagnetic waves radiated into space from the tapered part of the strip line, as shown in Figure 9B. It should be possible to remove peaks near 70MHz. Although the length of the coaxial cable inside the anechoic box was not mentioned in the above example, depending on the length of the cable exposed inside the anechoic box, resonance may occur due to coupling with the electric field inside the strip line. There is a risk. To prevent this, it is desirable that the length of the cable inside the anechoic box be 1/4 or less of the wavelength of the highest frequency used (150MHz), but in practice it is difficult to wire at this length. Therefore, the length of the cable floating in space should be reduced to 1/4 or less, and the other part should be brought into contact with, for example, a ferrite radio wave absorber on the floor before being drawn out. In this case, it is desirable that the portion that is routed in contact with the ferrite be approximately 1/3 of the total length. This makes it possible to damp the resonance of the cable by utilizing the magnetic loss of ferrite. As explained above, according to the present invention, it is possible to appropriately maintain the electric field strength inside a parallel conductor in a desired frequency range, and it is also possible to provide an incident interference rejection ability evaluation device with a compact size. It can be easily installed as part of the final inspection department in the equipment manufacturing process.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the strip line, Figure 2 is a block diagram of the incident interference rejection ability evaluation system, and Figure 3 is a block diagram of the system for evaluating the ability to reject incident interference.
The figure shows a calibration curve, FIG. 4 shows a conventional example of an incident interference rejection ability evaluation device, FIG. 5 shows a frequency characteristic of the configuration shown in FIG. FIG. 7 is a sectional view taken along the line AA in FIG. 6, FIG. 8 is an experimental example of the incident interference rejection ability evaluation device according to the present invention, and FIG. 9A is the frequency characteristic when the strip line is directly grounded to the anechoic box. Figure 9B
9 shows the frequency characteristics when the strip line is grounded to the anechoic box via a resistor, and FIG. 9C shows the frequency characteristics when the strip line and the anechoic box are electrically insulated. 1: lower conductor, 2: upper conductor, 3a: feeding end,
3b: terminating resistor end, 6: receiver under test, 20: anechoic box, 30: radio wave absorber, 40: power feeding coaxial cable, 50: insulating ring, 60: holding stand, 80
a, 80b: damping resistance, 90a, 90b:
Resistance body Batsuful.

Claims (1)

[Claims] 1. A strip line is placed in a closed metal case, with both ends of the upper conductor and lower conductor parallel to each other mechanically connected in a tapered shape through an insulator, with one end forming a disturbance signal feeding end and the other end forming a terminating resistor connecting end. In the incident interference rejection ability evaluation device, which evaluates the interference rejection ability of a test device by simulating a disturbing electromagnetic field by supplying a interference signal, a magnetic radio wave absorber attached to the inner surface of the metal case and the strip line are provided. means for holding the strip line in the metal case so that the lower conductor is electrically connected to the metal case via a damping resistor at both ends of the parallel portion of the lower conductor; electrically insulating between a power feeding coaxial cable that is connected to a disturbance signal feeding end and whose other end passes through the metal case and is connected to an external device that supplies the disturbance signal, and the power feeding coaxial cable and the metal case; 1. An incident interference rejection performance evaluation device comprising: an insulator having a large high-frequency loss; and a resistance buffle provided in the strip line opposite to the tapered portion of the line.