JPH0831755B2 - LC band pass filter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LC bandpass filter used in various electronic devices.

2. Description of the Related Art In recent years, electronic devices tend to be light, thin, short, and small, and miniaturization of electronic parts used in these electronic devices is emphasized in order to increase the density of parts. Also in the field of high frequency filters, miniaturized parts have come to be provided.

The conventional LC bandpass filter described above will be described below with reference to the drawings.

FIG. 4 shows an equivalent circuit diagram of a conventional LC bandpass filter with an attenuation pole.

In FIG. 4, 1,2,20 are coils, 3,4,5 are capacitors, 6 is mutual induction coupling, and 7 is a grounding part.

FIG. 4 shows a first LC series resonance circuit composed of the coil 20 and the capacitor 3 and a second LC composed of the coil 1 and the capacitor 4 when the attenuation pole is provided in the high band as shown in FIG.
Although the coil 6 of the series resonance circuit is configured by mutual induction coupling 6, but when the amplitude frequency characteristic at the attenuation pole is not good, the first LC series resonance circuit and the capacitor 21 are connected as shown in FIG. Are connected in parallel [in Fig. 6, the first LC
The capacitor 21 is connected in parallel with the series resonance circuit, but the second LC series resonance circuit may be used.] Attenuation pole 2 as shown in FIG.
There were two 2,23.

FIG. 5 shows the amplitude frequency characteristics in FIG. FIG. 6 shows an equivalent circuit when the first LC series resonance circuit and the capacitor 21 are connected in parallel. In FIG. 6, 1,2,20 are coils, 3,4,5 are capacitors, 6 is mutual induction coupling, 7 is a ground part, and 21 is a capacitor connected in parallel with the first LC series resonance circuit. . FIG. 7 shows the amplitude frequency characteristics in the case of the equivalent circuit shown in FIG.

In FIG. 7, 22 is a first attenuation pole and 23 is a second attenuation pole.

Problems to be Solved by the Invention However, the configuration shown in FIG. 6 has a drawback that the number of capacitors 21 is increased by one and the size is increased.

In view of the above drawbacks, the present invention provides an LC bandpass filter that can be configured as a circuit without increasing the number of capacitors and without increasing the size.

Means for Solving the Problems In order to achieve this object, the LC bandpass filter of the present invention has a coil of a first or a second LC series resonance circuit, which is wound in the same winding groove of a multiple bobbin. The second attenuation pole of the amplitude frequency characteristic can be selected by the distributed capacitance generated between the divided windings.

Action With this configuration, the attenuation pole can be freely set without increasing the number of capacitors.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an equivalent circuit diagram of an LC bandpass filter in the case where the coil of the first LC series resonance circuit is split winding on a multiple bobbin. In FIG. 1, reference numerals 1 and 2 are coils, 3,4,5 are capacitors, 7 is a grounding portion, 8 is a coil having split windings, and 6 is a distributed capacitance formed by a coil 8 of split windings. The capacitor 3 and the coil 8 form a first LC series resonance circuit, the coil 1 and the capacitor 4 form a second LC series resonance circuit, and the coil 2 and the capacitor 5 form an LC parallel resonance circuit. There is. The LC parallel resonance circuit is inserted and connected between the connection point of the first and second LC series resonance circuits and the ground section 7.

FIG. 2 is a perspective view of an LC bandpass filter using a multiple bobbin in which the coil of the first LC series resonance circuit is divided and wound in the same groove of the multiple bobbin. In FIG. 2, 9 is a multiple bobbin, 10 is the first winding of the coil 8 composed of split windings, 11 is the last winding of the coil 8 composed of split windings, and 12 is split winding. When you draw a line
The fixed winding wound in the adjacent groove for facilitating regulation of the number of windings and the winding direction of the last winding 11, 13 is the first winding groove of the multiple bobbin 9, and 14 is the same second winding groove. A winding groove, 15 is the third winding groove, and 16 is a terminal planted in the collar of the multiple bobbin 9.
Further, capacitors 3, 5, 4 are arranged on the collar of the multiple bobbin 9 and connected and fixed to the terminal 16. Further, in the first winding groove 13 of the multiple bobbin 9, the coil 8 by the divided winding is
In the second winding groove 14, the coil 2 and the coil 8 formed by the split winding are provided.
The fixed winding 12 and the coil 1 are wound in the third winding groove 15.

The operation of the LC bandpass filter configured as described above will be described below.

When splitting the coil 8 of the first LC series resonant circuit shown in FIG. 2, the first winding 10 of the split winding is placed in the first winding groove 13.
Winding a predetermined number of times and winding one turn in the second winding groove 14
After fixing the end of 10 and the beginning of the next winding 11, return to the first winding groove 13 and repeat winding the last winding 11 in the same winding direction as the winding 10 by a predetermined number. Wire to terminal 16. Then, the distributed capacitance 6 formed between the windings 10 and 11 is adjusted by changing the turns ratio of the first winding 10 and the last winding 11 of the divided windings, and the distribution capacitance 6 is adjusted as shown in FIG. The two attenuation poles can be freely moved, and an LC bandpass filter that is inexpensive and does not increase in shape can be configured without adding a special capacitor.

FIG. 3 shows amplitude-frequency characteristics when the winding ratio of the divided winding is changed. In Fig. 3, 17 is a split winding ratio of 5: 1, 18 is a split winding ratio of 3: 1 and 19 is a split winding ratio of 2: 1. .

As described above, the LC bandpass filter according to the present embodiment divides the coil of the first or second LC series resonance circuit into the same groove of the multiple bobbin and changes the winding ratio between the windings. The second attenuation pole can be freely changed by adjusting the generated distributed capacitance, and because it can be composed of only windings, it is an LC bandpass filter that is inexpensive and has a predetermined amount of attenuation without increasing the size. Can be configured, and the industrial effect is great.

In the embodiment, the LC bandpass filter including two LC series resonance circuits and one LC parallel resonance circuit is described, but an LC bandpass filter including more LC series resonance circuits and LC parallel resonance circuits is used. In one case LC
The same effect can be obtained by splitting the coils of the series resonance circuit. Further, the fixed winding 12 of the coil 8 by the split winding may be wound by providing a completely separate groove, or may be fixed by being hooked on a part of the flange.

As described above, according to the present invention, the coil of the first or second LC series resonance circuit is configured by the split windings, and the distributed capacitance generated between the split windings is adjusted by the winding ratio and the winding direction. This allows the second attenuation pole to be freely changed, and does not require a separate capacitor to increase the size, and can be achieved only by the winding, which is a significant cost advantage. The practical value is enormous.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of an LC bandpass filter according to an embodiment of the present invention, and FIG. 2 is a multiplex circuit in which the coils of the first LC series resonance circuit of the present invention are divided into multiple bobbins. Fig. 3 is a perspective view of a bobbin, Fig. 3 is an amplitude-frequency characteristic diagram when the split winding ratio is changed, Fig. 4 is an equivalent circuit diagram of an LC bandpass filter with attenuation pole, and Fig. 5 is with attenuation pole
Amplitude frequency characteristic diagram of LC band pass filter, Fig. 6 is an equivalent circuit diagram when a capacitor is connected in parallel to the first LC series resonance circuit, and Fig. 7 is a coil in parallel with the first LC series resonance circuit. It is an amplitude frequency characteristic figure at the time of connecting. 1,2 ... Coil, 3,4,5 ... Capacitor, 7 ... Ground part, 8 ... Split coil part.

Claims (1)

[Claims] 1. A first LC series resonance circuit, a second LC series resonance circuit, and an LC parallel resonance circuit inserted and connected between a connection point of the first and second LC series resonance circuits and ground. Composed,
The coil of each resonance circuit is wound around each winding groove of the multiple bobbin, and the coil of the first or second LC series resonant circuit is divided into the same winding groove of the multiple bobbin, and An LC bandpass filter configured to select the second attenuation pole of the amplitude frequency characteristic according to the distributed capacitance generated between the split windings.