JP2007202066A - Electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently suppress a high frequency current at a position where an integrated circuit is mounted, on a ground of a data processing circuit even when the ground of the data processing circuit is disposed in the vicinity of a ground of a radio circuit. <P>SOLUTION: An electronic device of the present invention includes a current injection circuit 4 which is connected to a ground 1 of the radio circuit and a ground 2 of the data processing circuit, for injecting a current in the same direction as a current flowing to the ground 1 of the radio circuit, from the ground 1 of the radio circuit to the ground 2 of the data processing circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for preventing high-frequency current flowing in a wireless circuit from interfering with an integrated circuit on a data processing circuit in an electronic device.

  In electronic devices such as mobile phones, when a printed circuit board equipped with an integrated circuit such as LSI (Large Scale Integration) is placed near the antenna, a strong high-frequency current flows through the printed circuit board and electromagnetic coupling occurs. was there. An electronic device that suppresses such electromagnetic coupling is disclosed in Patent Document 1, for example.

  Referring to FIG. 15, the electronic device disclosed in Patent Document 1 processes, on a printed circuit board 60, an antenna unit 70 that transmits and receives radio signals to and from a base station, and a radio signal that is transmitted and received by the antenna unit 70. A wireless circuit 71, a data processing circuit 72 on which an integrated circuit such as an LSI that processes various digital signals is mounted, and a power feeding unit 73 that supplies a signal to the antenna unit 70 and a signal from the antenna unit 70 to each circuit. Is provided. The printed circuit board 60 is a multilayer board in which a signal layer is formed on the first layer 61, a ground layer 83 is formed on the second layer 62, a power supply layer is formed on the third layer 63, and a signal layer is formed on the fourth layer 64. Part of the third layer 63 and the fourth layer 64 is a circuit pattern 74. A current control mechanism 80 is further provided on the printed circuit board 60 in order to separate the wireless circuit 71 and the data processing circuit 72 from each other. In the current control mechanism unit 80, metal surfaces 81 and 82 are arranged on upper and lower layers. In addition, the current control mechanism 80 has a line of via holes 84 in a straight line at a position near the center that is separated from the ends of the metal surfaces 81 and 82 by a quarter wavelength (= Lr, Ld) of the current to be controlled. Is formed.

  That is, in the electronic device disclosed in Patent Document 1, the input impedance is high at a position that is a quarter wavelength away from the ends of the metal surfaces 81 and 82, and current does not easily flow from the wireless circuit 71 to the data processing circuit 72. By utilizing this, electromagnetic coupling is suppressed.

  However, the electronic device disclosed in Patent Document 1 needs to provide the current control mechanism 80 over a 1/4 wavelength region, and requires a large occupied area.

On the other hand, in electronic equipment, for example, countermeasures against static electricity separate the frame ground to which static electricity is applied from the internal signal ground used for the return of LSI, etc., and connect these two grounds with a single ferrite bead. It is generally performed (see, for example, Patent Document 2). This ferrite bead is inserted for the purpose of suppressing the high-frequency component generated during electrostatic discharge from entering the signal ground by increasing the internal impedance of the electronic device as much as possible at high frequencies.
JP 2002-314491 A JP 2000-269613 A

  The electronic device can be configured to separate the ground of the wireless circuit and the ground of the data processing circuit by applying the technology for separating the signal ground and the frame ground. If the two grounds are sufficiently separated from each other, it is possible to sufficiently suppress the influence of the high-frequency current flowing through the ground of the wireless circuit on the LSI of the data processing circuit.

  However, in the case of a small electronic device, as shown in FIG. 16, in many cases, the ground 1 of the radio circuit and the ground 2 of the data processing circuit cannot be sufficiently separated. For this reason, the high-frequency current flowing through the ground 1 of the radio circuit may be electromagnetically coupled to the ground 2 of the nearby data processing circuit, causing an integrated circuit such as the LSI 3 sensitive to the high frequency to malfunction.

  Therefore, an object of the present invention is to sufficiently suppress the high-frequency current at the mounting position of the integrated circuit on the ground of the data processing circuit even when the ground of the data processing circuit is arranged in the vicinity of the ground of the wireless circuit. It is to provide an electronic device that can be used.

In order to achieve the above object, the present invention provides:
In an electronic apparatus having a printed circuit board on which a radio circuit for processing a radio signal and a data processing circuit for processing a digital signal are mounted, and a ground of the radio circuit and a ground of the data processing circuit are separated ,
The current for connecting the ground of the wireless circuit and the ground of the data processing circuit, and injecting the current in the same direction as the current flowing through the ground of the wireless circuit from the ground of the wireless circuit to the ground of the data processing circuit It further has an injection circuit.

  According to this configuration, when the ground of the data processing circuit is disposed in the vicinity of the ground of the wireless circuit, a high-frequency current having a reverse phase induced by the high-frequency current flowing through the ground of the wireless circuit flows in the ground of the data processing circuit. .

  However, since the current in the same direction as the current that flows to the ground of the wireless circuit is injected from the ground of the wireless circuit to the ground of the data processing circuit through the current injection circuit, the reverse phase that flows to the ground of the data processing circuit by this injected current. The high frequency current is canceled out.

  Therefore, since the high frequency current distribution can be minimized at an arbitrary position on the ground of the data processing circuit, if the integrated circuit is mounted at that position, the high frequency current can be sufficiently suppressed at the mounting position of the integrated circuit.

  In addition, it is possible to easily design the high-frequency countermeasures around the integrated circuit and reduce the number of high-frequency countermeasure components. In addition, since the ground of the wireless circuit is not easily affected by the digital noise of the data processing circuit, the failure of the wireless circuit can be suppressed. In addition, since the radiation pattern of the antenna is governed by the ground current of the radio circuit, it is possible to easily perform an original design of the antenna.

  The current injection circuit may be a pattern of the printed circuit board that connects the ground of the wireless circuit and the ground of the data processing circuit.

Moreover, the two printed circuit boards are provided, and the two printed circuit boards are connected by a cable.
The current injection circuit may be a pattern of the printed circuit board that connects the ground of the wireless circuit and the ground of the data processing circuit, and may be provided at one place on each of the two printed circuit boards. .

  According to this configuration, the impedance of the current injection circuit can be controlled by the pattern width and length of the printed circuit board even when the distribution of the high-frequency current changes due to the change in the frequency used in the electronic device. Can do.

  Further, the current injection circuit may be two or more capacitors each connecting the ground of the wireless circuit and the ground of the data processing circuit.

  According to this configuration, the impedance of the current injection circuit is controlled by the distance between the capacitors and the capacitance value of the capacitor even when the distribution of the high-frequency current changes with the change of the frequency used in the electronic device. be able to.

A current monitor circuit provided on the ground of the data processing circuit for monitoring a current flowing in the ground of the data processing circuit;
The current injection circuit may control a current injection amount injected from the ground of the wireless circuit to the ground of the data processing circuit based on the current value of the current monitored by the current monitor circuit.

  According to this configuration, even when the current distribution in the ground of the data processing circuit changes greatly due to environmental changes, the current injection amount can be automatically controlled following this.

The current injection circuit includes:
A variable resistor connecting the ground of the wireless circuit and the ground of the data processing circuit;
A control circuit that determines the current injection amount so that the current value of the current monitored by the current monitor circuit becomes a minimum value, and controls the resistance value of the variable resistor so as to be the determined current injection amount It is good also as having.

  According to this configuration, by controlling the current injection amount by the resistance value of the variable resistor, the current value of the current flowing through the ground of the data processing circuit can be controlled to be the minimum value.

  As described above, the electronic apparatus of the present invention has a configuration in which a current injection circuit is provided for injecting a current in the same direction as the current flowing through the ground of the wireless circuit from the ground of the wireless circuit to the ground of the data processing circuit. .

  Here, when the ground of the data processing circuit is disposed in the vicinity of the ground of the wireless circuit, a high-frequency current having a reverse phase induced by the high-frequency current flowing through the ground of the wireless circuit flows through the ground of the data processing circuit.

  However, in the present invention, a current in the same direction as the current flowing through the ground of the wireless circuit is injected from the ground of the wireless circuit to the ground of the data processing circuit through the current injection circuit. The high-frequency current of the opposite phase that flows through is canceled out.

  Therefore, since the high-frequency current distribution can be minimized at an arbitrary position on the ground of the data processing circuit, if the integrated circuit is mounted at that position, the high-frequency current can be sufficiently suppressed at the mounting position of the integrated circuit. An effect is obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of an electronic apparatus according to the present invention.

  Referring to FIG. 1, the electronic apparatus according to the present embodiment includes a wireless circuit that processes a wireless signal transmitted and received by an antenna and various digital signals (for example, digital audio in the case of a mobile phone) on the same printed circuit board. Data processing circuit for processing signals, digital image signals, and the like). An LSI 3 which is an integrated circuit is mounted on the ground 2 of the data processing circuit, and the ground 1 of the wireless circuit and the ground 2 of the data processing circuit are separated. The printed board is a multilayer board, but in FIG. 1, only the ground layer is shown, and the other layers are omitted. In FIG. 1, fine holes such as slits and via holes, signal patterns, power supply patterns, and the like are also omitted. In FIG. 1, the high-frequency oscillation circuit is represented by placing a transmission source in a semi-loop shape on the upper portion of the wireless circuit near the center of the ground 1.

  Furthermore, the electronic device of the present embodiment connects the ground 1 of the wireless circuit and the ground 2 of the data processing circuit, and the current in the same phase (in the same direction) as the current flowing through the ground 1 of the wireless circuit is supplied from the ground 1 of the wireless circuit. A current injection circuit 4 for injection into the ground 2 of the data processing circuit is provided. Although details will be described later, the current injection circuit 4 can be configured using a printed circuit board pattern, a capacitor, a variable resistor, and the like.

  When the above-described oscillation circuit operates, the current distribution of the ground 1 of the wireless circuit shows a distribution that is maximum near the center. On the other hand, a current in the opposite phase (reverse direction) to the ground 1 of the opposite radio circuit tends to flow through the ground 2 of the data processing circuit.

  However, in the present embodiment, a current of the same phase is injected from the ground 1 of the wireless circuit through the current injection circuit 4 to the ground 2 of the data processing circuit. Therefore, the reverse phase that flows to the ground 2 of the data processing circuit by this injected current. Current will be canceled out.

  Accordingly, since the reverse-phase current flowing through the ground 2 of the data processing circuit is greatly reduced, the high-frequency current at the mounting position of the LSI 3 is also greatly reduced.

  In FIG. 1, the current injection circuits 4 are provided at two locations near both the left and right ends. However, depending on the shape of the ground 1 of the wireless circuit and the ground 2 of the data processing circuit and the mounting position of the LSI 3, any one of them is provided. It can also be provided only at the location.

  In FIG. 1, when the power supply pattern of the power supply is spread in a planar shape, a gap between the ground 1 of the wireless circuit and the ground 2 of the data processing circuit is created by the power supply surface of the wireless circuit and the power supply surface of the data processing circuit. It is configured not to be blocked. For example, if one of the power supply surfaces is configured to straddle the above-described gap, electromagnetic wave leakage occurs in the straddling portion, and thus the effect of the present invention that the high-frequency current is reduced at the mounting position of the LSI 3 is impaired. .

  FIG. 2 is a diagram illustrating an application example of the electronic device illustrated in FIG. 1. Here, the electronic device shown in FIG. 1 is applied to a small electronic device such as a mobile phone.

  Referring to FIG. 2, in the electronic apparatus of this example, the ground 2 of the central data processing circuit and the grounds 1 of the upper and lower radio circuits are connected by current injection circuits 4 in the vicinity of the left and right ends, respectively.

  In the electronic apparatus of this example, a part of the current flowing in the ground 1 of the upper and lower radio circuits is shunted and flows to the ground 2 of the central data processing circuit through the current injection circuit 4. Therefore, the reverse-phase current flowing in the two upper and lower sides of the ground 2 of the data processing circuit is canceled by the common-mode current injected from the ground 1 of the upper and lower radio circuits.

  In addition, when an in-phase current flows through the ground 1 of the upper and lower wireless circuits, the magnetic field generated by the ground 1 of the upper and lower wireless circuits cancels out with the ground 2 of the central data processing circuit, and the high-frequency current is minimized. A region arises.

  In practice, a pattern for supplying power from the radio circuit is added to the ground 1 of the upper and lower radio circuits. Therefore, as shown in FIG. 3, there is a case where power is supplied in a form in which the ground 1 of the wireless circuit has a U shape and the ground 1 of the wireless circuit is provided on one of the short sides of the ground 2 of the data processing circuit. Many.

  FIG. 4 is a diagram illustrating still another application example of the electronic device illustrated in FIG. 1. Here, the electronic device shown in FIG. 1 is applied to a small electronic device such as a mobile phone.

  Referring to FIG. 4, in the wireless device of this example, the ground 2 of the central data processing circuit and the ground 1 of the square-shaped wireless circuit that circulates around the current are present on both short sides of the ground 2 of the data processing circuit. They are connected by an injection circuit 4.

  As described above, there are various combinations of the ground 1 of the wireless circuit and the ground 2 of the data processing circuit. However, in either configuration, the high-frequency current at the installation position of the LSI 3 is suppressed by canceling out the current of the portion of the data processing circuit ground 2 facing the ground 1 of the wireless circuit by the current flowing through the ground 1 of the wireless circuit. It is configured to do.

  FIG. 5 is a diagram illustrating still another application example of the electronic device illustrated in FIG. 1. Here, the electronic device shown in FIG. 1 is applied to a foldable mobile phone.

  Referring to FIG. 5, in the electronic apparatus of this example, two printed boards are provided in each of the upper and lower casings, and the two printed boards are connected by a flexible table or the like. A ground 1 for the radio circuit and a ground 2 for the data processing circuit are provided over the two printed boards. The antenna directivity as a mobile phone is mainly determined by the current flowing in the ground 1 of the radio circuit. The LSI 3 for digital signal processing is provided on the ground 2 of each data processing circuit of the two printed boards.

  In addition, a high-frequency current is distributed on the ground 1 of the wireless circuit, and a reverse-phase current flows on the ground 2 of the opposing data processing circuit. For this reason, the ground 1 of the radio circuit and the ground of the data processing circuit are provided at one place on each of the two printed boards, that is, in two places which are the farthest points of the short sides of the left and right ends of the two printed boards in FIG. 2 is provided.

  5 shows an example in which the ground 1 of the wireless circuit and the ground 2 of the data processing circuit are arranged on the same flexible cable. However, the ground 1 of the wireless circuit and the ground 2 of the data processing circuit are different from each other. Even when connected by a cable, basically the same effect can be obtained.

  FIG. 6 is a diagram illustrating another configuration example of the electronic apparatus according to the invention.

  Referring to FIG. 6, in addition to the current injection circuit 4, the electronic device of the present embodiment is a current monitor for monitoring the current flowing in the ground 2 of the data processing circuit in the vicinity of the LSI 3 on the ground 2 of the data processing circuit. A circuit 5 is provided.

  In FIG. 6, in order to monitor the high-frequency current flowing into the LSI 3 and the high-frequency current flowing out from the LSI 3, the current monitor circuits 5 are provided at two locations upstream and downstream of the high-frequency current of the LSI 3. It can also be provided in only one place. However, when the LSI 3 is a large-scale integrated circuit having several hundred pins or more, the average current distribution can be monitored by installing the current monitor circuits 5 at two locations as shown in FIG.

  The current monitor circuit 5 can be composed of a magnetic field sensor such as a loop magnetic field sensor, a Hall element, or an MR element. It is also possible to configure the loop type magnetic field sensor as a printed circuit board pattern and embed it in the printed circuit board. Further, since the direction of current spreads two-dimensionally, it is possible to obtain the optimum value by monitoring the current in the two directions X and Y.

  FIG. 7 is a diagram for explaining the configuration of the current injection circuit 4 and the current monitor circuit 5 shown in FIG.

  Referring to FIG. 7, the current monitor circuit 5 includes a magnetic field sensor 51 that detects a high-frequency current flowing in the ground 2 of the data processing circuit, a preamplifier 52 that amplifies the high-frequency current detected by the magnetic field sensor 51, and a preamplifier 52. A high-frequency rectifier circuit 53 that rectifies the amplified high-frequency current, and a buffer 54 that shapes the high-frequency current rectified by the high-frequency rectifier circuit 53 and outputs the current to the current injection circuit 4 as a monitor current. .

  Further, the current injection circuit 4 connects a ferrite bead 41 for connecting the ground 1 of the wireless circuit and the ground 2 of the data processing circuit in a DC manner, and connects the ground 1 of the wireless circuit and the ground 2 of the data processing circuit. A variable resistor 42, a driver 43 for changing the resistance value of the variable resistor 42, and a current monitor value indicating the current value of the monitor current output from the current monitor circuit 5 are derived, and based on the derived current monitor value And a control circuit 44 that determines the current injection amount and sets the resistance value of the variable resistor 42 in the driver 43 so as to be the determined current injection amount. Instead of the ferrite bead 41, another element that exhibits a low resistance value at the DC level and increases the resistance value at a high frequency can be used.

  FIG. 8 is a flowchart for explaining an example of processing until the current injection amount is determined such that the current monitor value becomes the minimum value in the electronic device shown in FIG.

Referring to FIG. 8, the current monitor circuit 5 monitors the high frequency current flowing in the ground 2 of the data processing circuit, and outputs the high frequency current to the current injection circuit 4 as a monitor current (step 801). Next, the control circuit 44 of the current injection circuit 4 receives the monitor current output from the current monitor circuit 5, converts the monitor current into a digital value by A / D conversion, and converts the digital value to the current current. the monitor value I _n (step 802). The current monitor value is derived at regular intervals.

The control circuit 44 determines the current injection amount so that the current monitor value becomes the minimum value. Therefore, the control circuit 44, as shown in FIG. 9, the current injection amount on the horizontal axis, in order to create a graph plotting the current monitor value on the vertical axis, each time to derive a current monitoring value I _n, current injection The amount is increased by a certain amount ΔI. The current monitor value changes as shown in FIG. That is, I _n <I _n-1 until the current monitor value reaches the minimum value, but I _n > I _n-1 after the current monitor value reaches the minimum value.

If n is 1 or I _n <I _n-1 (step 803), the control circuit 44 determines that the current monitor value has not yet reached the minimum value, and the current injection amount I is The resistance value of the variable resistor 42 is set in the driver 43 so as to be the current injection amount I + ΔI at the next n + 1 (step 804). In response to this, the driver 43 changes the resistance value of the variable resistor 42 according to the setting of the control circuit 44 (step 805).

  As a result, the amount of current injected from the ground 1 of the wireless circuit to the ground 2 of the data processing circuit changes, so that the high-frequency current flowing through the ground 2 of the data processing circuit also changes. Accordingly, the monitor current monitored by the current monitor circuit 5 in step 801 and the current monitor value derived by the control circuit 44 in step 802 change.

By repeating the above processing, when I _n > I _n−1 in step 803, the control circuit 44 determines that the current monitor value has reached the minimum value, and the current injection amount I is the previous n−1. A resistance value of the variable resistor 42 is set in the driver 43 so that the current injection amount I-ΔI at that time is reached (step 806). In response to this, the driver 43 changes the resistance value of the variable resistor 42 according to the setting of the control circuit 44 (step 807).

With the above processing, the current monitor value is set to the minimum value, and the processing ends. In FIG. 9, since I _n > I _n−1 when n = 6, the current injection amount at the next n = 7 is the current injection amount at the previous n = 5. It is the same.

  Note that the method of determining the current injection amount with the current monitor value as the minimum value is not limited to the example of FIG. 8, and it goes without saying that other methods such as the Newton method may be used. Further, if the increment of ΔI is large, the difference from the true minimum value becomes large. On the other hand, if the increment of ΔI is small, the difference from the true minimum value is small, but the number of repetitions until the current injection amount that is the minimum value is determined increases, so that the processing time increases.

  Hereinafter, the electronic apparatus of the present invention will be described in detail with reference to examples.

Example 1
FIG. 10 is a diagram illustrating the configuration of the electronic apparatus according to the first embodiment of the present invention.

  Referring to FIG. 10, the electronic device of this embodiment is the simplest example of the electronic device shown in FIG. That is, the current injection circuit 4 is configured by a printed circuit board pattern that connects the ground 1 of the radio circuit and the ground 2 of the data processing circuit. In the case of this configuration, the impedance of the current injection circuit 4 is controlled by the width and length of the pattern. This controls the current injection amount and suppresses the current distribution in the vicinity of the LSI 3 that is sensitive to the high-frequency current.

(Example 2)
FIG. 11 is a diagram illustrating a configuration of an electronic apparatus according to the second embodiment of the present invention. This embodiment is an embodiment in which the electronic device shown in FIG. 1 is applied to a foldable mobile phone.

  Referring to FIG. 11, in the electronic device of this example, the left lower housing is provided with an 8 cm × 4 cm printed circuit board, and the right upper housing is provided with a 9 cm × 4 cm printed circuit board. These two printed circuit boards are connected by a flexible cable. In addition, a ground 1 of a wireless circuit having a width of 5 mm is disposed in the periphery of the two printed circuit boards, and a ground 2 of the data processing circuit is disposed on the inside thereof. The antenna is connected to the ground 1 of the radio circuit on the side (right end) opposite to the flexible cable of the right printed circuit board, and is fed from the base of the antenna. In the right printed board, the gap, that is, the distance between the two grounds is 3 mm, and in the left printed board, the gap is 1 mm. The left printed board has one 1 mm wide pattern current injection circuit 4 in the upper left gap, and the right printed board has one 1 mm wide pattern current injection circuit 4 in the upper right gap. There are places.

  FIG. 12 is a diagram showing a simulation result of FDTD (Finite Difference Time Domain) using the electronic device shown in FIG. 11 as a model. Here, currents in the X direction are compared with relative values at a frequency of 1 GHz. 12A is a simulation result of a model in which neither of the two current injection circuits 4 in FIG. 11 is provided and there is no contact point between the wireless circuit and the data processing circuit. FIG. 11 shows a simulation result of a model in which only the left printed circuit board current injection circuit 4 is provided, and FIG. 12C shows a simulation result of the model of FIG.

  Referring to FIG. 12, in (a), a strong current distribution was observed at the installation position of the LSI 3 indicated by the black frame near the flexible cable. In (b), the current distribution at the installation position of the LSI 3 is rather deteriorated. In (c), it can be seen that the high-frequency current is sufficiently low in the vicinity of the flexible cable.

  As described above, when the ground 1 of the wireless circuit is connected to the ground 2 of the data processing circuit, it is assumed that the high-frequency current increases in the ground 2 of the data processing circuit. By controlling the frequency, the high-frequency current can be kept low at the installation position of the LSI 3 sensitive to the high frequency.

(Example 3)
FIG. 13 is a diagram illustrating a configuration of an electronic apparatus according to the third embodiment of the present invention.

  Referring to FIG. 13, the electronic device of the present embodiment includes the current injection circuit 4 of the electronic device shown in FIG. 1 with two capacitors each connecting the ground 1 of the radio circuit and the ground 2 of the data processing circuit. It is composed. In this embodiment, the current injection circuit 4 is referred to as a capacitor 4.

  The distance between the two capacitors 4 is set according to the distance between the ground 1 of the radio circuit and the ground 2 of the data processing circuit, and the high-frequency current interferes with the LSI 3 by controlling the capacitance of the capacitor 4. Is set so that the phases of the currents flowing through the two capacitors 4 differ from each other by 180 ° at the frequency at which the suppression is to occur.

  In the case where the capacitor 4 is configured under this condition, if a structure constituted by the ground 1 of the radio circuit and the ground 2 of the data processing circuit is regarded as a slot line, the slot line has a mode resonance corresponding to half-wave resonance. Occurs, and a current that can cancel the current flowing to the ground 2 of the data processing circuit to the maximum extent flows.

  FIG. 14 is a diagram illustrating the amplitude and phase according to the distance between two capacitors.

  Referring to FIG. 14, the capacitor 4 has a characteristic of advancing the phase. Therefore, the distance between the two capacitors 4 may be substantially shorter than a half wavelength at a desired frequency.

  In the present embodiment, by appropriately selecting the capacitance value of the capacitor 4, the capacitor 4 can be mounted at an arbitrary position, and the degree of freedom in design increases.

It is a figure which shows one structural example of the electronic device of this invention. It is a figure which shows one application example of the electronic device shown in FIG. It is a figure which shows the other application example of the electronic device shown in FIG. It is a figure which shows the further another application example of the electronic device shown in FIG. It is a figure which shows the further another application example of the electronic device shown in FIG. It is a figure which shows the other structural example of the electronic device of this invention. It is a figure explaining the structure of the current injection circuit and current monitor circuit which were shown in FIG. 7 is a flowchart for explaining an example of processing until a current injection amount is determined such that a current monitor value becomes a minimum value in the electronic device shown in FIG. 6. 7 is a graph showing a relationship between a current injection amount and a current monitoring amount in the electronic device shown in FIG. 6. It is a figure which shows the structure of the electronic device of Example 1 of this invention. It is a figure which shows the structure of the electronic device of Example 2 of this invention. It is a figure which shows the simulation result of FDTD which used the electronic device shown in FIG. 11 as a model. It is a figure which shows the structure of the electronic device of Example 3 of this invention. In the electronic device shown in FIG. 13, it is a figure which shows the amplitude and phase according to the distance between capacitors, (a) is a figure which shows the amplitude and phase when the distance between capacitors is expanded, (a) is a capacitor It is a figure which shows the amplitude and phase when the distance between them is narrowed. It is a figure which shows one structural example of the conventional electronic device, (a) is a perspective view, (b) is sectional drawing. It is a figure which shows the other structural example of the conventional electronic device.

Explanation of symbols

1 Ground of a radio circuit 2 Ground of a data processing circuit 3 LSI
4 Current injection circuit 5 Current monitor circuit

Claims (6)

In an electronic apparatus having a printed circuit board on which a radio circuit for processing a radio signal and a data processing circuit for processing a digital signal are mounted, and a ground of the radio circuit and a ground of the data processing circuit are separated ,
The current for connecting the ground of the wireless circuit and the ground of the data processing circuit, and injecting the current in the same direction as the current flowing through the ground of the wireless circuit from the ground of the wireless circuit to the ground of the data processing circuit An electronic device further having an injection circuit.   The electronic device according to claim 1, wherein the current injection circuit is a pattern of the printed circuit board that connects a ground of the wireless circuit and a ground of the data processing circuit. Two printed circuit boards are provided, and the two printed circuit boards are connected by a cable.
The current injection circuit is a pattern of the printed circuit board that connects a ground of the wireless circuit and a ground of the data processing circuit, and is provided at one place on each of the two printed circuit boards. Item 2. The electronic device according to Item 1.   The electronic device according to claim 1, wherein each of the current injection circuits is two or more capacitors that connect a ground of the wireless circuit and a ground of the data processing circuit. A current monitor circuit provided on the ground of the data processing circuit for monitoring a current flowing to the ground of the data processing circuit;
2. The current injection circuit according to claim 1, wherein the current injection circuit controls a current injection amount injected from a ground of the wireless circuit to a ground of the data processing circuit based on a current value of a current monitored by the current monitor circuit. Electronics. The current injection circuit includes:
A variable resistor connecting the ground of the wireless circuit and the ground of the data processing circuit;
A control circuit that determines the current injection amount so that the current value of the current monitored by the current monitor circuit becomes a minimum value, and controls the resistance value of the variable resistor so as to be the determined current injection amount The electronic device according to claim 5, comprising: