JPS63179603A - Band-pass filter - Google Patents

Abstract

PURPOSE:To attain low cost and miniaturization by providing an inductance in parallel with an LC series resonance circuit and winding an earth winding on the inductance overlappingly by one turn or over in the opposite winding direction. CONSTITUTION:An inductance L3 is provided in parallel with a series resonance circuit comprising an inductance L2 and a capacitor C2 to provide an attenuation pole at a low frequency and the earth winding LE is wound on the inductance L3 in the opposite winding direction to that of the inductance L3. Thus, an optional attenuation pole is provided to a frequency higher than the pass band of the band-pass filter. Thus, the band-pass filter whose size is decreased is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a bandpass filter used in various electronic devices.

2. Description of the Related Art In recent years, with the advancement of various electronic devices, filters have been provided in which the characteristics of the electronic components used in these devices are sharply reduced in bands other than the passband. Therefore, filters that sharply reduce the low and high frequencies have also been provided for pandopass filters and f-ruta filters.

The conventional bandpass filter mentioned above will be explained below with reference to the drawings.

Figure 3 (This is an equivalent circuit showing the configuration of a conventional band-pass filter. As shown in the equivalent circuit of Figure 3, the conventional band-pass filter consists of a parallel resonant circuit consisting of an inductance L4 and a capacitor C1, and an inductance L2 , consists of an in-line resonant circuit consisting of a capacitor C2, and when provided with attenuation at any point in the frequency band higher and lower than the passband, an inductor 7s L5.LC parallel circuit is connected in parallel to the LC series resonant circuit. It was common to add an inductance L4 in series with the bandpass filter shown in FIG. 4. FIG. 4 is an amplitude characteristic diagram of the bandpass filter shown in FIG.

Problems to be Solved by the Invention The Cono bandpass filter requires four inductances L1 to L4 and two fixed capacitors C4 to C2, which requires two inductances compared to a bandpass filter without attenuation poles. This required an extra layer, leading to an increase in costs.

In view of the above problems, the present invention replaces the conventional bandpass filter with an attenuation pole with four inductances and two capacitors with three inductances and two capacitors.
The present invention provides an inexpensive and compact bandpass filter, which is composed of several capacitors and one inductance is composed of several turns of ground winding.

Means for Solving the Problems In order to solve the above problems, the bandpass filter of the present invention includes an inductance in parallel with the LC series resonant circuit in order to provide an attenuation pole at an arbitrary point at a frequency lower than the passband. is provided, and the earth winding is wound over the inductance in a direction opposite to this winding direction in an overlapping manner of 1 tl - 1 turn or more.

Function In this way, in order to provide an attenuation pole in the lower range than the passband of a band-pass filter, the ground winding can be wound inexpensively and with a large shape by wrapping several turns of the ground winding on top of the wound inductance in the opposite direction to the inductance. It becomes possible to provide an arbitrary attenuation pole in a region higher than the passband without having to do so.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is an equivalent circuit showing the configuration of a bandpass filter in an embodiment of the present invention. In the figure, in order to provide an attenuation pole in the low range, inductance L2,
An inductance L3 is configured in parallel with the series resonant circuit of the capacitor C2, and a ground winding L8 is wound around one inductance in the opposite direction to the inductance L3.

In the figure, capacitor C1 and inductance L indicate a parallel resonant circuit.

In the figure, inductance L3U inductance L2° is an inductance configured in parallel with the series resonant circuit of capacitor C2 and provided with an arbitrary attenuation pole lower than the passband of the bandpass filter.

FIG. 2 shows the amplitude characteristics when the ground winding shown in FIG. 1 of the present invention is varied between 1 and 10 turns. In the diagram, M is L8
is set to 1 turn, B is set to 6 turns, and C is set to 10 turns.

In this way, by overlapping several turns of the ground winding Lxt in the opposite winding direction to the inductance L5 wound to provide an attenuation pole in the low frequency range, the frequency side higher than the pass range of the band pass filter is can be provided with an arbitrary attenuation pole.

It has been experimentally confirmed that if all turns of the earth winding are wound in the same direction as the inductance L3 over the inductance L3, there will be no attenuation pole in the high range.

Effects of the Invention As described above, the present invention replaces the conventional trap-equipped bandpass filter with four inductances and two capacitors with three inductances, several turns of ground winding, and two capacitors. By making it possible to obtain the same characteristics with a capacitor, it is possible to provide an inexpensive and miniaturized bandpass filter.Furthermore, by changing the ground winding, it is possible to provide all attenuation poles on the higher frequency side than the passband. It has the practical value of being able to adjust to any desired frequency.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of a band-pass filter according to an embodiment of the present invention, FIG. 2 is an amplitude characteristic diagram of the same band-pass filter, and FIG. 3 is an equivalent circuit diagram of a conventional band-pass filter.
FIG. 4 is an amplitude characteristic diagram of the bandpass filter shown in the equivalent circuit of FIG. 3. L,,L2. L,...Inductance, C1,
C2... Capacitor, L... Earth winding. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2" Figure 3 Figure 4"

Claims (1)

[Claims] Consists of an LC series resonant circuit and an LC parallel resonant circuit,
In order to provide an attenuation pole at an arbitrary frequency lower than the passband, an inductance is provided in parallel with the LC series resonant circuit, and one or more turns of the earth winding in the opposite direction to the winding direction of the LC series resonance circuit are placed on top of the inductance. Wrapped bandpass filter.