JPS62274908A - Filter circuit - Google Patents

Abstract

PURPOSE:To constitute a circuit with a small number of elements by cascading the first filter circuit which is switched to a low-pass filter characteristic and a high-pass filter characteristic and the second filter circuit which is switched to a band pass filter characteristic and a band stop filter characteristic. CONSTITUTION:When a voltage is impressed to power supply terminal 8 in a preceding-stage circuit, a diode 4 and a diode 3 are made conductive and non-conductive respectively and the input and the output are grounded by capacitors 17 and 18 to from a low pass filter whose input and output are connected by coils 11 and 12. When a voltage is impressed to a power supply terminal 10 in a succeedingstage circuit, a diode 6 and a diode 5 are made conductive and non-conductive respectively and the input and the output are earthed by a parallel circuit consisting of a coil 15 and a capacitor 21 and that consisting of a coil 16 and a capacitor 22 to form a band pass filter whose input and output are connected by series circuits consisting of coils 13 and 14 and capacitors 19 and 20. The preceding-stage circuit and the succeeding-stage circuit are cascaded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention is used for a cheese, etc. that receives a signal band such as a television signal by dividing it into a plurality of signal bands. Related to filter circuits.

[Conventional technology]

Regarding a filter circuit consisting of a plurality of filters that divide a signal band, as shown in Japanese Unexamined Patent Publication No. 57-72410, switching diodes are provided at the input and output of each filter and connected in parallel to select the reception band. There are known circuits that do this. .

[The point that the invention is trying to solve]

The above conventional technology requires a band for each filter.

Capacitors and coils because out-of-range attenuation is obtained.

The number of circuit components increases.

The purpose of the present invention is to simplify the circuit and reduce the number of elements.

The purpose of this invention is to realize a filter circuit that can be configured with a number of children.

[Means for solving problems]

In order to achieve the above object, the present invention includes a fill.

Filter circuits with switching characteristics are connected in cascade. .

That is, the first filter characteristic and the second filter.

A first filter circuit and a third filter whose characteristics are switched.

A second filter circuit that switches between a filter characteristic and a fourth filter characteristic is connected in cascade.

[Effect]

By cascading the first filter circuit and the second filter circuit, for example, the first filter characteristic can be changed to the fifth filter characteristic by cascading the third filter characteristic or the fourth filter characteristic. Convert one filter characteristic into two so as to obtain a sixth filter characteristic.

It can be used for filter characteristics, and circuit components can be shared.

Therefore, the number of circuit components can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows CATV signals from 50 to 800 MHz.

This is a filter circuit used for the input of a tuner that receives a TV signal and a TV double signal. In Figure 1, 1 is the signalman.

2 is a signal output terminal, 3 to 6 are for signal switching.

switching diode, 7 to 10 are power supply terminals,
11 to 16 are coils, 17 to 29 are capacitors,
Of these, 23 to 29 are bypass capacitors for blocking direct current. Further, 30 to 37 are resistors.

The circuit shown in FIG. 1 is composed of a circuit from a signal input terminal 1 to a capacitor 24 to a signal output terminal 2 (second-stage circuit). In the front stage circuit, when a voltage is applied to the power supply terminal 8, the diode 4 becomes conductive, and the diode 3 becomes conductive.
becomes non-conductive, and the input and output are connected to capacitor 17.
, 18 is grounded, and the input and output are connected to the coils 11 and 12.
Low pass phi connected by.

A router is formed. Also, voltage is applied to the power supply terminal 7.

When applied, diode 3 is in a conductive state, da.

The diode 4 is in a non-conducting state, and the input and output are grounded through coils 11 and 12, respectively, and the input and output are connected.

A high pass filter connected by capacitors 17 and 18.

It is formed. Next is the power supply for the subsequent circuit.

When a voltage is applied to the terminal 10, the diode 6 becomes conductive, the diode 5 becomes non-conductive, and the input and output are connected to the parallel circuit of the coil 15 and capacitor 21, and the coil 1, respectively.
6 and a capacitor 22 in a parallel circuit, and the input and output are connected by a series circuit of coils 13 and 14 and capacitors 9 and 20, forming a panned passph.

irta is formed. In addition, the low current ion 6 at the power supply terminal 9 becomes non-conductive, and the input and output are connected to the series circuit of the coil 13 and the capacitor 9 or to the coil 1.
4 and a capacitor 20 in series circuit, and the input and output are the coil 15 and the capacitor 214.

and a parallel circuit of the coil 16 and the capacitor 22.

are connected to form a bandstop circuit.

Figure 2 shows a low-pass filter.

Set the cutoff frequency to 190MH2, and pandopass.

The low cutoff frequency of the filter and bandstop filter is 100 MHz, and the high cutoff frequency is 300°M.
This shows the frequency characteristics of the attenuation amount when H2 is set.〇Coils 11 and 12 are each 22rLH and a capacitor.

17, 18 to 23 pF + coil 13.14 to 3 full H1° capacitor 19, 20 to 34 pF, coil 15.16.

45 nH, 17 capacitors 21 and 22 were selected to be 29 pF.

The characteristics of a low-pass filter are actually described in [38].

Characteristics of high-pass filter: Point I! Pandopa at 39.

The characteristics of the filter are shown by the dashed dotted line 40.

The characteristics of the whirlpool filter are shown by two-dot chain lines 41, respectively. Next, when the front-stage circuit and the rear-stage circuit are connected in cascade and a voltage is applied to 9, the front-stage circuit operates as a low-pass filter, and the rear-stage circuit operates as a band-stop filter. The following shows the low-pass filter characteristics of the power supply.

When voltage is applied to supply terminals 8 and 1o, the first stage is activated.

The path is a 0-hass filter, and the subsequent circuit is a panned passf.

It operates as a filter with a passband of -10 indicated by the dotted line 43.
Shows bandpass filter characteristics from 0 to 190 MHz.

vinegar. Also, apply voltage to power supply terminals 7 and 1o.

When added, the front stage circuit is a high pass filter and the rear stage circuit.

operates as a band-pass filter, and exhibits band-pass filter characteristics with a passband of 190 to soo MHz indicated by a dashed line 44°. Further, when a voltage is applied to the power supply terminals 7 and 9, the front-stage circuit operates as a high-pass filter, and the rear-stage circuit operates as a band-pass filter, and exhibits a cutoff frequency of 300 MHz and a high-frequency filter characteristic as shown by the two-point line 45. In this way, according to the embodiment shown in FIG. 1, there is a circuit that switches between a low-pass filter and a high-pass filter whose cutoff frequencies are close to each other, and a circuit that switches between a bandpass filter and a bandstop filter whose cutoff frequencies are close to each other. The cascade results in a filter that divides the frequency band into four. The circuit configuration of the example is shown below.

The filter and capacitor are shared for each filter characteristic.

As a result, the number of circuit components is extremely small.

ing. This filter circuit is the secondary of the tuner.

This improves the intermodulation characteristics, and for CATV signals of 50 to 550 MH2, the reception band is increased to 50 to 100 MH2.
, 100-190 MH2, 190-300 MH2
, 300~.

The high frequency of each reception band is 550 MHz.

The frequency is set to be twice the low frequency or less. Regarding the reception band division, for example, if you want to receive the VHF high band of the American channel in one band, the band division should be 50 to 90 MH.

90-168 MHz H2, 168-280 MHz
, 280 MH2~.

It is also conceivable to divide it into 550 MHz.

FIG. 4 shows a second embodiment. In Figure 4.

Components having the same functions as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals. The difference between FIG. 4 and FIG. 1 is that coils 46, 4B, 51 and capacitors 47, 49, 50, 52 are added. Of these, capacitors 47 and 50 are bypass capacitors.
7. Since it is a capacitor, it is a die for high frequency signals.

A coil 46 and a diode 5 are connected in parallel with the ode 4.

A parallel circuit of a coil 48 and a capacitor 49 is connected in parallel.

In addition, a coil 51 and a capacitor are connected in parallel with the diode 6.

The configuration is such that a series circuit of sensors 52 is added to each. In the case of the embodiment shown in FIG. 4, the front stage circuit is also the same.

Low-pass filter and high-pass filter, second stage.

Hashant filter and bandstop filter.

This is a configuration that can be switched from one to another. Figure 5 shows the diagram of Figure 4.

The frequency characteristics of the attenuation amount of the example are shown. Coilli. ,.

12 is 23rLH, = +y capacitor 17, 18 is 13-
pF.

Coil 46 is 16nH, coil 13 is 46rkH1-1
7 capacitor 19 is 19FLH, :ffil 14 is 52nH
, :+y capacitor 20 is 161)F, :Iil 48 is 3O
rLH,=ry capacitor 49 is 29pp, and coil 1
5 is 54 n H.

Capacitor 21 is 16pF, coil 16 is 49nH.

Capacitor 22 is 17pp, coil 51 is 21rLH.

The figure shows the case where the capacitors 52 are each selected to be 40 pF, but as in the first embodiment, a low-pass filter indicated by a solid line 53, a band-pass filter indicated by a dotted line 54, a chain-dot line 55, and a two-pass filter are used. Dot-dashed line.

Although the characteristics of the high-pass filter shown in 56 can be obtained, in this case, the number of circuit elements is smaller than that of the embodiment shown in FIG.

Although it has increased, a large amount of attenuation has been obtained. difference.

Furthermore, the coil 46 is used as a high-pass filter in the front stage circuit, and the coil 48 and capacitor 49 are used in the rear stage circuit.

When the band stop filter operates, the coil 51 and.

The capacitor 52 operates as a bandpass filter in the subsequent circuit.

Since it affects only the songwriting, there is a large degree of freedom in selecting circuit constants, which also improves the degree of freedom in designing circuit characteristics. Note that no element is connected in parallel to the diode 6, but a capacitor is connected in parallel.

In this case, the amount of attenuation of the low-pass filter can be further increased.

FIG. 6 shows a third embodiment. Components that perform the same functions as those in the embodiment shown in FIG. 4 are given the same reference numerals, but the differences from the embodiment shown in FIG. 62 and 63 are added, and the bypass capacitor 47 is a capacitor that resonates in series with the coil 46 in the receiving frequency band.

60. When voltage is applied to the power supply terminals 9 and 59, the coil 46° is grounded by the bypass capacitor 61, as shown in FIG.

It becomes a high-pass filter shown by a two-dot chain line 57, but when no voltage is applied to the power supply terminal 59, it becomes a carp.

The cable 46 is grounded by a capacitor 60. In this case.

When the capacitor 60 is selected to be 22 pF and the resonance frequency with the coil 46 is approximately 280 MH, the filter characteristics are as follows.
It becomes like the broken line 57 in the figure. In this way, according to the third embodiment shown in FIG. 6, a filter that divides the frequency band into five can be obtained with a simple configuration.

FIG. 7 shows a fourth embodiment. 64 in Figure 7
-71 are switching diodes, 72-80 are coils, 81-89 are capacitors, 90-93 are power supply terminals, and 94-105 are resistors. The coils 72 and 73 and capacitors 81 constitute a low-pass filter, and the coils 74 and capacitors 82 and 83 constitute a high-pass filter. In addition, the coils 75, 76, and 77, and the two condensers 84, 85, and B6 constitute a bandpass filter, and the coils 78, 79, 80, and the other condensers 84, 85, and B6 constitute a bandpass filter.

Bandstop fill with density sensors 87, 88, and 89.

It constitutes the Turn off the switching diode.

'7　Converter, low-pass filter and high-pass filter.

and configure the filter by selecting a bandpass filter and a bandstop filter. For example, power supply.

When voltage is applied to the supply terminal 90, the diode 64°65
is in a conductive state, and diodes 66 and 67 are in a non-conductive state.

The pre-stage circuit has low-pass filter characteristics.

Ru. Furthermore, if a voltage is applied to the power supply terminal 92, the subsequent circuit will have bandpass filter characteristics. If each filter characteristic is as shown in FIG. 2, the filter characteristic shown in FIG. 7 becomes a four-division filter characteristic as shown in FIG. 3 by switching the power supply terminal. In this case also coils and conte.

Since the sensor can be shared, the circuit can be simplified, and since each filter is separated, there is an advantage that there is a high degree of freedom in design.

In the above embodiments, two filter states are switched in each of the first stage and second stage, but the present invention is not limited to a configuration in which six or more filter states are switched.

Furthermore, it is not only possible to cascade the two stages, the front stage and the rear stage.

A structure of three or more stages of a'-connection is also possible.

〔Effect of the invention〕

According to the present invention, circuit configuration elements can be shared for a plurality of filter characteristics, so the circuit configuration is reduced.

It becomes possible to configure a filter circuit using the elements.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. 2FA is a characteristic diagram showing the frequency characteristics of the attenuation amount of the filter used in the circuit shown in FIG. 1, and FIG. 3 is a characteristic diagram showing the frequency characteristics of the overall attenuation amount of the circuit shown in FIG. 1. ,
Further, FIG. 4 is a circuit diagram showing a second embodiment of the present invention, and FIG. 5 is a characteristic diagram showing the frequency characteristics of the attenuation amount.
Figures 6 and 7 are respectively 3. FIG. 7 is a circuit diagram showing a fourth example. 3-6...Switching diode, 11-16...
・Coyle, Patent Attorney Masaru Ogawa 2 Kanuma sweat number (M) - 1z) muscle 4 solid, jI 50th number (MHz) 6th block also 7th

Claims (1)

[Claims] 1. A first filter circuit that switches between low-pass filter characteristics and high-pass filter characteristics, and a second filter circuit that switches between band-pass filter characteristics and band-stop filter characteristics are connected in cascade. Characteristic filter circuit. 2. The low and high cutoff frequencies of the bandpass filter and bandstop filter of the second filter circuit are close to each other, and the cutoff frequencies of the lowpass filter and highpass filter of the first filter circuit are close to each other. 2. The filter circuit according to claim 1, wherein the filter circuit is close to and between the high cutoff frequency and the low cutoff frequency. 3. The second filter circuit consists of a first resonant circuit consisting of a series connection of a first coil and a first capacitor, and a second resonant circuit consisting of a series connection of a second coil and a second capacitor. A third resonant circuit in which the input and output are connected by the connection, and a third resonant circuit consisting of a parallel connection of a third coil and a third capacitor, and a fourth resonant circuit consisting of a parallel connection of a fourth coil and a fourth capacitor. Input and output are connected by series connection, and a connection point between the first and second resonant circuits and a connection point between the third and fourth resonant circuits are grounded by first and second switching diodes, respectively. 3. A filter circuit according to claim 2, characterized in that: