JP3806652B2 - Noise removal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a noise removing device, for example, a noise removing device that reduces noise in a high-frequency signal path between integrated circuits.
[0002]
[Prior art]
Recent electronic devices are remarkably reduced in size, weight and performance. For this reason, the electronic circuit is configured using a lot of integrated circuits (ICs) rather than individual electronic components. A high-frequency signal (data) flows through a signal line or a data communication line between such integrated circuits. The signal lines through which these high-frequency signals flow are mixed with noise from the outside or mixed into surrounding circuits. In particular, when the signal is a pulse-like signal such as high-frequency digital data, noise generated in the signal transient is significant.
[0003]
The prior art in such a technical field is disclosed in, for example, “High-frequency noise removal method and high-frequency noise removal device” in Japanese Patent Application Laid-Open No. 11-127123. That is, the conventional high frequency noise removing device is generally configured as shown in FIG. 4 (A) or (B). These conventional high-frequency noise removal apparatuses 30A or 30B use common (same) circuit elements for a plurality of signal lines 40 interconnecting the integrated circuits 31 and 32, respectively.
[0004]
That is, in the high frequency noise removing device 30A of FIG. 4A, resistors 41 to 43 are connected in series to the signal line 40 that interconnects the integrated circuits 31 and 32, respectively. Resistance values R1 to R3 of these resistors 41 to 43 have substantially equal values. On the other hand, in the high frequency noise removing device 30B shown in FIG. 4B, inductors 44 to 46 are connected in series with the signal line 40 in series.
[0005]
[Problems to be solved by the invention]
If the resistors 41 to 43 are used in the signal line 40 as in the high frequency noise removing device 30A, it is small and inexpensive. However, when the resistance values R1 to R3 are increased, the high-frequency signal waveform transmitted through the signal line 40 is rounded. Therefore, when the resistance values R1 to R3 are reduced, noise is not sufficiently removed, and there is a problem that the noise removal effect is small.
[0006]
On the other hand, the high frequency noise removal circuit 30B uses inductors 44 to 46 that use a magnetic core such as an air core coil or ferrite. Inductors increase impedance at high frequencies, and are effective in removing high-frequency noise. However, the desired inductance is disadvantageous in that it takes up more space than the resistor and is expensive. In particular, when a ferrite core or the like is used, there is a problem that the occupied area increases and the cost increases.
[0007]
OBJECT OF THE INVENTION
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a noise removal device capable of realizing a good noise removal characteristic at a relatively small size and low cost.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, the noise removal apparatus according to the present invention employs the following characteristic configuration.
[0009]
(1) The circuit blocks are interconnected by a plurality of signal lines, and when data is communicated by synchronizing the data flowing through each signal line, a noise removal element is inserted into the signal line to flow through the signal line. In a noise removal device that reduces high-frequency signal noise,
At least one of the plurality of signal lines uses an inductor as the noise removing element, the remaining signal lines use resistors, and the resistor has a resistance value corresponding to an impedance in a predetermined low frequency region of the inductor. Is set, and the signal line to which the inductor is connected is a noise removal apparatus that uses a signal line that includes the highest harmonic component frequency.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration and operation of a preferred embodiment of a noise removing device according to the present invention will be described in detail with reference to the accompanying drawings.
[0014]
First, FIG. 1 is a configuration diagram of a first embodiment of a noise removing device according to the present invention. This noise eliminator 10A includes integrated circuits 11 and 12 that are circuit blocks that operate at high frequencies, and a plurality of (three in the illustrated example) signals through which the integrated circuits 11 and 12 are interconnected and high-frequency signals flow. (Or data communication) It is configured by the line 20, and data communication is performed by synchronizing data flowing through each signal line. Different types of elements are used as noise removal (or reduction) elements connected to the plurality of signal lines 20.
[0015]
That is, in the noise removing apparatus 10A of the first embodiment shown in FIG. 1, the harmonic frequency component is the largest among the three signal lines 20, and one signal line that affects the other has an inductor (L4). ) 21 is connected in series to the signal line, and resistors (R4) 22 and (R5) 23 are connected in series to the other two signal lines, respectively.
[0016]
FIG. 2 is a frequency (horizontal axis) vs. impedance (vertical axis) characteristic diagram of the inductor 21 connected to the signal line 20 of the noise removing apparatus 10A shown in FIG. The inductor 21 is preferably a high frequency noise filter inductor using a ferrite core, but an air-core coil may be used. As shown in FIG. 2, the impedance of the inductor 21 is substantially zero at a low frequency, and the impedance increases as the frequency increases (however, the impedance increases due to the distributed capacitance (capacitance) and the like as the frequency increases further. descend).
[0017]
In the noise removing apparatus 10A shown in FIG. 1, the integrated circuits 11 and 12 are assumed to operate in a frequency region (data communication frequency) indicated by a in FIG. The inductor 21 is selected so as to have a predetermined high impedance at the harmonic component frequency of the integrated circuits 11 and 12 indicated by b in FIG. Therefore, the resistors 22 and 23 are made to function in the data communication frequency region a where the impedance of the inductor 21 is substantially 0 or extremely small. In other words, the resistance value corresponding to the impedance in the low frequency region a of the inductor 21 is set for these resistors.
[0018]
Next, FIG. 3 is a block diagram of a second embodiment of the noise removing apparatus according to the present invention. Similarly to the above-described noise removing apparatus 10A, the noise removing apparatus 10B is also configured by the integrated circuits 11 and 12 and a plurality of signal lines 20 to which different types of noise removing elements are connected. For example, of the three signal lines, inductors (L5) 24 and (L6) 25 are connected in series to two signal lines having a higher harmonic frequency component, and resistor (R6) 26 is connected to the remaining one signal line. Connected in series.
[0019]
The configuration and operation of the preferred embodiment of the noise removing device according to the present invention have been described in detail above. However, such an embodiment is merely an example of the present invention and does not limit the present invention. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention. In the above-described embodiment, there are three signal lines. However, even when there are four or more signal lines, different types of noise removing elements are used. That is, an inductor is used for at least one signal line, and resistors are used for the remaining signal lines.
[0020]
【The invention's effect】
As understood from the above description, according to the noise removing apparatus of the present invention, the following remarkable effects in practical use can be obtained. In other words, expensive parts are used for the signal line between circuit blocks (integrated circuits) or data communication lines with the highest harmonic component frequency (lines that affect others), and inexpensive parts are used for other lines. Since it can be used, the harmonic component removal capability (performance) can provide the same effect as when expensive components are used for all signal lines.
[0021]
For example, when the present invention is applied to an FM radio, both the case where an inductor is used for all signal lines and the case where an inductor is used only for a signal line having the highest harmonic content according to the present invention are shown as a result of an experiment. The improvement in radio sensitivity suppression was substantially equivalent at 10 dBμV.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment of a noise removing device according to the present invention;
FIG. 2 shows frequency vs. impedance characteristics of an inductor.
FIG. 3 is a configuration diagram of a second embodiment of a noise removing device according to the present invention.
FIG. 4 is a configuration diagram of a conventional high-frequency noise removing device.
[Explanation of symbols]
10A, 10B Noise removal device 11, 12 Circuit block (integrated circuit)
20 Signal (data communication) lines 21, 24, 25 Inductors 22, 23, 26 Resistance

Claims (1)

When circuit blocks are interconnected by a plurality of signal lines and data is communicated in synchronization with the data flowing through each signal line, a noise removal element is inserted into the signal line and a high-frequency signal flowing through the signal line is transmitted. In a noise removal device that reduces noise,
At least one of the plurality of signal lines uses an inductor as the noise removing element, the remaining signal lines use resistors, and the resistor has a resistance value corresponding to an impedance in a predetermined low frequency region of the inductor. Is set, and the signal line to which the inductor is connected is a signal line including the highest harmonic component frequency.

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