TWI429922B - Non-contact measurement method for electromagnetic interference - Google Patents

Description

Non-contact electromagnetic interference measurement method

The invention relates to an electromagnetic interference measurement method, in particular to a non-contact electromagnetic interference measurement method.

A conventional non-contact electromagnetic interference measurement method, as shown in Chinese Patent Publication No. 200841032, which has a spectrum analyzer and a near field probe electrically connected to the spectrum analyzer, the measurement method is The near-field probe performs a non-contact scanning on a test object to obtain a near-field spectrum, and the near-field spectrum can effectively confirm whether the object to be tested has an electromagnetic interference source, but the method cannot provide interference of the electromagnetic interference source. Path, if the object to be tested contains a plurality of circuit units, it is impossible to know whether the electromagnetic interference source causes electromagnetic interference to each of the circuit units.

The main object of the present invention is to provide a non-contact electromagnetic interference measurement method, including providing a test object, a wireless transmitting device, a first wireless receiving device, a vector network analyzer, and a spectrum analyzer. The vector network analyzer has a first communication port and a second communication port. The wireless transmitting device is electrically connected to the first communication port, and the first wireless receiving device is electrically connected to the second communication port. Providing a calibration reference component, the vector network analyzer measuring the calibration reference component to obtain a near-field probe factor; measuring the object to be tested by the spectrum analyzer to obtain a first interference source spectrum, The vector network analyzer measures the object to be tested to obtain a first path transfer function; multiplying the near field probe factor by the first interference source spectrum and the first path transfer function to obtain a second interference a source spectrum and a second path transfer function; adding the second interference source spectrum and the second path transfer function to obtain a predicted electromagnetic interference spectrum. The invention measures the object to be tested by the spectrum analyzer to obtain a first interference source spectrum and measures the object to be tested by the vector network analyzer to obtain a first path transfer function, and then performs correction through reduction. And the data analysis obtains the predicted electromagnetic interference spectrum, and the non-contact electromagnetic interference measurement method can effectively predict the interference path of the interference source, thereby solving the electromagnetic interference problem.

Please refer to FIG. 1 , which is a preferred embodiment of the present invention. The steps of the non-contact electromagnetic interference measurement method 1 are as follows: First, please refer to step (A), FIG. 2A and FIG. FIG. 2B and FIG. 5 provide a test object 10, a vector network analyzer 20, a spectrum analyzer 30, a wireless transmitting device 40, and a first wireless receiving device 41. The vector network analyzer 20 is provided. The first communication port 41 is electrically connected to the first communication port 21, and the first wireless receiving device 41 is electrically connected to the second communication port 22, In this embodiment, the object to be tested 10 needs to be placed stably and the object to be tested 10 is operated in a normal state to ensure the accuracy of the subsequent measurement. Refer to step (B) of FIG. 1 to correct the vector network. The analyzer 20 and the spectrum analyzer 30 are configured to perform an instrument (not shown) correction by a corrector, and the corrector is electrically connected to the first communication port 21 and the second communication.埠22 to correct the systematic error generated by the instrument itself. Next, please refer to steps (C) and 3 of Figure 1. A calibration reference component 50 is provided. The vector network analyzer 20 measures the calibration reference component 50 to obtain a near-field probe factor. Preferably, the vector network analyzer 20 is capable of penetrating-reflecting-line. (Thru-Reflect-Line, TRL) calibration method measures the calibration reference component 50 to measure the near-field probe factor including amplitude and phase information, and the near-field probe factor is used to correct the wireless transmission When the device 40 and the first wireless receiving device 41 transmit or receive a signal, the amount of signal attenuation generated at different frequencies, in this embodiment, the calibration reference member 50 can be a microstrip line 51, the microstrip The second end of the line 51 is electrically connected to the second communication port 22. The calibration reference member 50 further includes a terminal load 52. The terminal load 52 is electrically connected to the microstrip line 51, in this embodiment. The microstrip line 51 has wide frequency and low loss characteristics. In addition, please refer to FIG. 7 , which is a measurement curve of the near field probe factor, which is used as a reduction correction of the electromagnetic interference signal. Next, please refer to steps (D), 2A and 2B of Figure 1. The wireless transmitting device 40 and the first wireless receiving device 41 search for the electromagnetic interference source of the object to be tested 10. If the object 10 has a plurality of circuit units, it usually has a plurality of electromagnetic interference sources. Non-contact measurement is performed by near-field detection to find the measurement point where the strongest electromagnetic interference source is located. The strongest electromagnetic interference source is called equivalent electromagnetic interference source. Please refer to step (E) of Figure 1. 4 and 5, the vector network analyzer 20 measures the object to be tested 10 to obtain a first path transfer function, and the spectrum analyzer 30 measures the object to be tested 10 to obtain a first For an interference source spectrum, please refer to FIG. 2A and FIG. 2B, which is a measurement method of the first path transfer function in the non-contact electromagnetic interference measurement method 1, and the measurement method is near electric field or near In the form of a magnetic field, an induced current is generated on the object to be tested 10, so the vector network analyzer 20 can inject a test signal into the object to be tested 10 by the wireless transmitting device 40, and at the same time, the first wireless receiving The device 41 receives the test signal on the object to be tested 10 The electric field and the near magnetic field are converted into a power signal and then transmitted back to the vector network analyzer 20, and then the first path transfer function is obtained through analysis. In this embodiment, the wireless transmitting device 40 can be a near field. The probe 400, the first wireless receiving device 41 can be the near field probe 42 or an antenna 43, please refer to FIG. 4, which is a preferred embodiment for measuring the first transfer function. In an embodiment, the object to be tested is a liquid crystal display 11 having an antenna 12, and the first end of the antenna 12 is electrically connected to a first coaxial cable 44. The first communication device 41 is electrically connected to the antenna 12 of the liquid crystal display 11. In addition, the antenna 12 is likely to be interfered by an equivalent electromagnetic interference source. Preferably, the antenna 12 is a WWAN receiver, and the vector network analyzer 20 inputs a test signal to the equivalent electromagnetic interference source of the liquid crystal display 11 by the near field probe 42. Measuring point, when the test signal reaches the antenna 12 via the transfer path The first coaxial cable 44 receives the test signal sent by the antenna 12 and analyzes it through the vector network analyzer 20 to obtain the first path transfer function, and the phase information obtained by the near-field probe factor can restore the The phase delay of the first path transfer function. In addition, please refer to FIG. 5, which is a preferred embodiment for measuring the first interference spectrum. In this embodiment, it further has a preamplifier 60 and a first The wireless receiving device 45 is electrically connected to the spectrum analyzer 30 and the second wireless receiving device 45. In this embodiment, the second wireless receiving device 45 can be a near field probe 42. The spectral signal of the equivalent electromagnetic interference source of the liquid crystal display 11 is received by the near field probe 42 , amplified by the signal of the preamplifier 60, and finally the measured value is recorded by the spectrum analyzer 30, and the gain of the preamplifier 60 is obtained. The first interference source spectrum can be obtained by the correction of the step (B), and the measurement result is restored. Please refer to FIG. 6 , which is a measurement method of the electromagnetic interference spectrum actually generated by the antenna 12 . Measurement method A second coaxial cable 46 is electrically connected to the antenna 12, and the electromagnetic interference signal received from the antenna 12 is amplified by the signal of the preamplifier 60, and finally the measured value is recorded by the spectrum analyzer 30. Step (F) of the figure, multiplying the near-field probe factor by the first interference source spectrum to obtain a second interference source spectrum and multiplying the near-field probe factor by the first path transfer function to obtain a The second path transfer function, through the data operation described above, the interference source spectrum and the path transfer function can be corrected by the measurement curve of the near-field probe factor to restore the real data. Finally, refer to the step of FIG. 1 (G) And adding the second interference source spectrum and the second path transfer function to obtain a predicted electromagnetic interference spectrum. In step (G), the second interference source spectrum is in dBm, and the second path transfer function In the value of the dB value, the two can be directly added together. Please refer to FIG. 8A and FIG. 8B , which is to predict the antenna 12 of the liquid crystal display 11 by using the non-contact electromagnetic interference measurement method 1 . This is generated within the WWAN band Comparing the predicted electromagnetic interference spectrum curve with the electromagnetic interference spectrum curve actually generated by the antenna 12, the measurement system includes the GSM and UMTS bands in the WWAN band, and the 8A and 8B diagrams can be used to learn the two. The degree of coincidence is extremely high, and the higher harmonics of the pixel clock of the liquid crystal display 11 can be diagnosed to cause desensitization of the WWAN receiver. Please refer to FIG. 9A and FIG. 9B, which is the embodiment. The path transfer function measured in the path transfer function can be used to effectively improve the electromagnetic interference of the liquid crystal display 11 to the WWAN receiver by increasing the attenuation of the path. According to the present invention, the object to be tested is measured by the spectrum analyzer to obtain a first interference source spectrum, and the object to be tested is measured by the vector network analyzer to obtain a first path transfer function, and then restored. The predicted electromagnetic interference spectrum is obtained by calibration and data calculation, and the non-contact electromagnetic interference measurement method can effectively predict the interference path of the interference source, thereby solving the electromagnetic interference problem.
The scope of the present invention is defined by the scope of the appended claims, and any changes and modifications made by those skilled in the art without departing from the spirit and scope of the invention are within the scope of the present invention. .

1‧‧‧ Non-contact electromagnetic interference measurement method
10‧‧‧Test object
11‧‧‧LCD display
12‧‧‧Antenna
20‧‧‧Vector Network Analyzer
21‧‧‧First Communication埠
22‧‧‧Second Communications埠
30‧‧‧ spectrum analyzer
40‧‧‧Wireless transmitter
41‧‧‧First wireless receiver
42‧‧‧ Near field probe
43‧‧‧Antenna
44‧‧‧First coaxial cable
45‧‧‧Second wireless receiving device
46‧‧‧Second coaxial cable
50‧‧‧ calibration reference
51‧‧‧Microstrip line
52‧‧‧ terminal load
60‧‧‧Preamplifier

1 is a flow chart of a non-contact electromagnetic interference measurement method according to a first preferred embodiment of the present invention.
2A-2B is a diagram showing an example of measurement of a path transfer function of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
Figure 3 is a schematic diagram showing the measurement of the near-field probe factor of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
Figure 4 is a schematic diagram showing the measurement of the path transfer function of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
Figure 5 is a schematic diagram showing the measurement of the interference source spectrum of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
Figure 6 is a schematic diagram showing the measurement of the actual electromagnetic interference spectrum of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
Figure 7 is a graph showing the measurement of the near-field probe factor of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
8A-8B is a diagram showing the comparison of the predicted electromagnetic interference spectrum-actual electromagnetic interference spectrum of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.
9A-9B is a graph showing the measurement of the path transfer function of the non-contact electromagnetic interference measurement method according to the first preferred embodiment of the present invention.

1‧‧‧ Non-contact electromagnetic interference measurement method

10‧‧‧Test object

11‧‧‧LCD display

12‧‧‧Antenna

20‧‧‧Vector Network Analyzer

21‧‧‧First Communication埠

22‧‧‧Second Communications埠

40‧‧‧Wireless transmitter

42‧‧‧ Near field probe

44‧‧‧First coaxial cable

Claims (10)

A non-contact electromagnetic interference measurement method, which comprises:
Providing a device to be tested, a wireless transmitting device, a first wireless receiving device, a vector network analyzer, and a spectrum analyzer, the vector network analyzer having a first communication port and a second communication port. The wireless transmitting device is electrically connected to the first communication port, and the first wireless receiving device is electrically connected to the second communication port;
Providing a calibration reference component, the vector network analyzer measuring the calibration reference component to obtain a near field probe factor;
Measuring the object to be tested by the vector network analyzer to obtain a first path transfer function, and measuring the object to be measured by the spectrum analyzer to obtain a first interference source spectrum;
Multiplying the near-field probe factor by the first interference source spectrum to obtain a second interference source spectrum and multiplying the near-field probe factor by the first path transfer function to obtain a second path transfer function; The second interference source spectrum and the second path transfer function are added to obtain a predicted electromagnetic interference spectrum. The non-contact electromagnetic interference measurement method according to claim 1, wherein the first wireless receiving device can be a near field probe or an antenna. The non-contact electromagnetic interference measurement method according to claim 1, wherein the wireless transmitting device is a near field probe. The non-contact electromagnetic interference measurement method according to claim 1, further comprising a calibration vector network analyzer and the spectrum analyzer. The non-contact type electromagnetic interference measurement method according to the first aspect of the invention, wherein the calibration reference component is a microstrip line, and the end of the microstrip line is electrically connected to the second communication port. The non-contact type electromagnetic interference measuring method according to claim 5, wherein the calibration reference unit further comprises a terminal load, and the terminal load is electrically connected to the microstrip line. The non-contact type electromagnetic interference measurement method according to the first aspect of the invention, further comprising the electromagnetic interference source for searching the object to be tested by the wireless transmitting device and the wireless receiving device. The non-contact type electromagnetic interference measurement method according to claim 1, further comprising a preamplifier and a second wireless receiving device, wherein the preamplifier is electrically connected to the second wireless receiving device and the spectrum Analyzer. The non-contact electromagnetic interference measurement method according to the eighth aspect of the patent application, wherein the second wireless receiving device is a near field probe. The non-contact electromagnetic interference measurement method according to the first aspect of the patent application, wherein the vector network analyzer can perform a correction reference by a Thru-Reflect-Line (TRL) correction method. The measurement is performed to measure the probe factor including amplitude and phase information.