JPH0575381A - Comb filter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a high-performance comb filter in which a widening element is added to a bypass means connected in parallel with a delay line. In a comb type filter in which a delay line 7 and a bypass means VC are connected in parallel, each input terminal of the delay line 7 and the bypass means VC is connected through a widening element Tr, and an input electric signal is A first electric signal passing through the delay line 7 via the amplification element Tr and a second electric signal passing through the bypass means VC via the amplification element Tr are generated, and these first and second electric signals are generated. A combined output signal obtained by combining the electric signals is obtained from the output terminals 9 and 10. [Effect] The widening element prevents an unwanted wave (double wave) generated in the medium of the delay line from flowing into the bypass means, and a good comb-shaped characteristic is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a comb filter using a delay line, and more particularly to a high-performance comb filter having a widening element added to a bypass means connected in parallel with the delay line.

[0002]

BACKGROUND OF THE INVENTION Comb filters are used in electronic equipment such as televisions and are used, for example, to separate a chrominance signal and a luminance signal which are intercarriers in a television signal.

The circuit configuration and electrical characteristics of a conventional comb filter are shown in FIGS. In FIG. 7, reference numeral 5 is a delay line made of glass having a converter provided at the input and output ends as a medium, and 6 is a variable capacitor for bypass connected in parallel to the delay line 5.

Then, the input signals applied to the input terminals 1 and 2 are combined with the first electric signal passing through the delay line 5 and the second electric signal passing through the variable capacitor 6, and are output to the output terminals 3 and 4. The combined output signal is generated.

The composite output signal has a comb-shaped characteristic as shown in FIG. Here, in the medium of the delay line 5, an ultrasonic wave emitted from an input transducer provided on the left side of the drawing of FIG. 7 propagates as shown by an arrow A, and this ultrasonic wave is an output transducer provided on the right side of the drawing of FIG. To be converted into an electric signal by the output converter.

[0006]

However, according to the above construction, the so-called ultrasonic wave emitted from the input transducer is partially reflected in the direction of arrow B in the output transducer as shown by the dotted line in the drawing. The second harmonic reaches the input converter again,
The arriving ultrasonic wave is converted into an electric signal by the input converter, and the electric signal is bypassed by the variable capacitor 6
However, there is a problem in that a good comb filter cannot be obtained as a result.

[0007]

According to the present invention, in a comb-shaped filter having a delay line and a bypass means connected in parallel, each input terminal of the delay line and the bypass means is connected through a widening element. And the input electrical signal causes a first electrical signal passing through the delay line through the amplification element and a second electrical signal passing through a bypass means through the amplification element, the first electrical signal , A combined output signal obtained by combining the second electric signals is obtained from the output terminal.

[0008]

This comb-shaped filter prevents the electric signal from flowing into the bypass due to the above-mentioned second harmonic, and obtains a good comb-shaped characteristic.

[0009]

EXAMPLES Next, examples of the comb filter according to the present invention will be described. 1, 2 and 3 are diagrams showing a first embodiment of a comb filter according to the present invention.

In FIG. 1, R ₁ and R ₂ are bias resistors, T _r is an amplifying transistor, R ₃ is a load resistor, and 7
Is a delay line, VR is a resistance for gain adjustment, VC is a variable capacitance element which is an impedance element for bypass, R ₄ ,
R ₅ , R ₆ , and R ₇ are load resistors, L ₁ and L ₂ are impedance matching coils, and + B is a power source. here,
The reason why the variable capacitance element VC is used is that the adjustment of phase, impedance matching and the like can be performed by the variable capacitance element having a small shape size without performing adjustment by the coil L ₂ , so that the overall shape after assembly becomes small. Because.

Now, when a television signal is applied to the input terminal 8, a first electric signal passing through the delay line 7 via the transistor Tr and a second electric signal passing through the impedance VC also via the transistor Tr. Signal and
These first and second electric signals are combined in the load resistors R _{4 to} R ₅ , and the combined electric signal is output terminal 9,
Taken out from 10. Here, the electric signal taken out from the output terminals 9 and 10 is only one of the luminance signal and the color signal of the television signal.

According to the above-mentioned structure, the transistor Tr reaches the input converter of the delay line by the so-called second harmonic wave generated in the medium of the delay line 7 and the transistor Tr is generated even if an electric signal is generated by the input converter. Therefore, the electric signal does not flow to the variable element VC which is the bypass impedance element. Therefore, a good comb filter is always formed by the variable capacitance element VC and the delay line 7.

FIG. 2 is a structural diagram formed based on the circuit configuration of FIG. In the figure, 7 is a delay line, 11 is a plate-shaped delay body made of glass, 12 and 13 are input converters and output converters respectively provided on the end faces of the delay medium 11, and 26 is one input and output converter 12. , A lead wire fixed to each electrode 13
Is an absorber that fixes an epoxy resin or the like formed on the surface of the delay medium 11 and absorbs unnecessary ultrasonic waves among the ultrasonic waves propagating in the delay medium. Reference numeral 20 is a phenolic or ceramic insulating substrate printed on the surface, and reference numerals 21, 23 and 24 are resistors R ₁ to
R ₇ , coils L ₁ , L ₂ , 22 are transistors Tr, 2
Reference numeral 5 is an adjusting resistor VR, 27 is a variable capacitance element VC, and 28 are external terminals 8 to 10 and a ground terminal. Reference numeral 29 denotes a pin made of a conductive material which projects from the lower surface of the substrate 20 and electrically connects and fixes to the lead wire 26 of the delay line 7 at the projection. Three
Reference numerals 0 and 40 denote case halves for accommodating the delay line 7 and the insulating substrate 20 in which the above-described components are assembled. FIG. 3 is a perspective view of the comb filter that has been assembled.

In the above structure, since each part constituting the comb-type filter such as the amplification circuit, the delay line and the impedance matching is unitized, the delay time, frequency characteristic and input / output impedance at the time of assembling, etc. Can be adjusted in relation to each other.

FIG. 4 shows a second comb-shaped filter according to the present invention.
It is a figure which shows an Example. Although the reference numerals and detailed description are omitted in the figure, the point that an npn-type transistor is used as a widening element is largely different from FIG. Also in this embodiment, as in the case of the above-mentioned first embodiment, the widening element prevents the double wave generated in the medium of the delay line from flowing into the bypass impedance element, and a good comb-shaped filter is formed. To be done.

FIG. 5 shows a third comb-shaped filter according to the present invention.
It is a figure which shows an Example. Although the reference numerals and detailed description are omitted in the figure, the point that the output side is used as an inductive coupling circuit is greatly different from that of the first embodiment. Also in this embodiment, as in the case of the first and second embodiments, the widening element prevents the double line generated in the medium of the delay line from flowing into the bypass impedance element. A filter is formed.

FIG. 6 shows a fourth comb-shaped filter according to the present invention.
It is a figure which shows an Example. In the figure, although the reference numerals and detailed description are omitted, it is described above that the variable capacitance element is not used as the bypass means as in FIG. 1 and the emitter of the transistor which is the amplification element is directly connected to the coil which is the load. It differs greatly from the first embodiment. In addition, a fixed element may be used as the bypass means. Also in this embodiment, as in the case of the first, second and third embodiments described above, the amplification element prevents the double wave generated in the medium of the delay line from flowing into the bypass means, and a good comb shape is obtained. A filter is formed.

In the above description, without connecting one end of each of the bypass impedance element and the delay line to the emitter and collector of the amplification element, for example, one end of the delay line is connected to the collector of the transistor Tr in FIG. One end of the bypass impedance element VC may be connected to the base of the transistor Tr, respectively.

[0019]

As described above, the comb filter according to the present invention is a comb filter in which the delay line and the bypass means are connected in parallel, and the input ends of the delay line and the bypass means are widened. A first electrical signal connected through the element, the input electrical signal passing through the delay element through the delay line, and a second electrical signal passing through the amplifying element through the bypass means.
, And the combined output signal obtained by combining the first and second electric signals is obtained from the output terminal. Therefore, an unnecessary wave (double wave) generated on the input side of the delay line is generated. However, since it does not flow into the bypass means as it is, there is an effect that good comb-shaped filter characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is an exploded perspective view showing the structure of the first embodiment.

FIG. 3 is a perspective view showing a first embodiment.

FIG. 4 is a circuit diagram showing a second embodiment.

FIG. 5 is a circuit diagram showing a third embodiment.

FIG. 6 is a circuit diagram showing a fourth embodiment.

FIG. 7 is a circuit diagram showing a conventional example.

FIG. 8 is a general comb filter characteristic diagram.

[Explanation of symbols]

 7 Delay line VC Bypass means 8 Input terminal 9, 10 Output terminal

Claims (3)

[Claims] 1. A comb-type filter comprising a delay line and a bypass means connected in parallel, wherein each input terminal of the delay line and the bypass means is connected through a widening element, and an input electric signal is supplied to the input electric signal. First passing through the delay line through the width element
And the second electric signal passing through the bypass means via the amplification element, and the combined output signal obtained by combining the first and second electric signals is obtained from the output terminal. Comb-shaped filter. 2. The comb filter according to claim 1, wherein an impedance element is used as the bypass means. 3. The comb filter according to claim 1, wherein a variable impedance element is used as the bypass means.