JPS5852369B2 - Circuit board for surface wave filter element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit board for a surface wave filter element.

As shown in FIG. 1, the surface wave filter element has an input electrode made up of a pair of comb-shaped electrodes 1L12, and an output electrode made of a pair of comb-shaped electrodes 13 and 14, which is placed opposite to this input electrode. A piezoelectric substrate 15 is mounted and fixed on a stem 16, and is electrically connected to stem pins 17, 18.degree.

In a surface wave filter element having such a structure, the stem pin 17 is usually directly implanted in the stem 16 and serves as a ground terminal.

Other stem pins 18, 19, and 20 are implanted in the stem 16 via an insulating member, and the stem pin 18 serves as a signal input terminal, and the stem pins 19 and 20 serve as output terminals and are connected to the next stage differential amplifier, etc. ing.

In the figure, 21 is another grounding stem pin.

The above-mentioned surface wave filter element is fixed together with other parts to a circuit board having printed wiring in a predetermined shape, and is incorporated into a television device or the like.

Next, FIG. 2 shows a state in which a surface wave filter element is mounted and fixed on a conventional circuit board, as seen from the printed wiring side.

In the figure, the same reference numerals as in FIG. 1 indicate the same parts. That is, a portion of the circuit board 31 including a printed wiring section 32 connected to the signal input terminal 18, printed wiring sections 33 and 34 connected to the output terminals 19 and 20, and ground terminals 17 and 21 is a ground section 35. There is.

However, when a surface wave filter element, especially a surface wave filter element using a high impedance piezoelectric substrate, is mounted and fixed on the circuit board 31 having such printed wiring, the signal input terminal 18 and the output terminals 19 and 20 are asymmetrical. It is susceptible to induction, and for example, as shown in the curve 36 shown in FIG. 3, the trap points 37 and 38 become high, and radio waves with frequencies other than the required frequency enter the next stage differential amplifier etc. from the output terminals 19 and 20. This caused deterioration of the characteristics of the surface wave filter element.

The reason for using the high-impedance piezoelectric substrate mentioned above is that surface wave filter elements using a low-impedance piezoelectric substrate have poor variations in temperature characteristics and electrical characteristics. This is because the wave filter element has good temperature characteristics and extremely small variations in electrical characteristics.

The present invention has been made in view of the various drawbacks of the conventional circuit boards for surface wave filter elements described above, and provides a circuit board for surface wave filter elements particularly suitable for surface wave filter elements using high impedance piezoelectric substrates. It is intended to.

Next, a first embodiment of the present invention will be described with reference to FIG.

In the figure, the same reference numerals as in FIG. 1 indicate the same parts. That is, the circuit board 41 includes a printed wiring section 42 connected to the signal input terminal 18, printed wiring sections 43 and 44 electrically connected to the output terminals 19 and 20, and a portion including the ground terminals 17 and 21 as the ground section 35. This is the same as in the conventional circuit board, but in this embodiment, the signal input terminal 18 and this input terminal 1
8 and the output terminal 19 in the diagonal direction, an extending portion 47 is provided extending from the printed wiring portion 43 toward the signal input terminal 18.

By providing the extension portion 47 in this manner, induction between the signal input terminal 18 and the output terminals 19 and 20 is prevented,
By receiving the signal from this output terminal with a differential amplifier, it becomes possible to lower the trap points 49 and 50 of the curve 48 in FIG. It has become possible to improve the frequency characteristics of

That is, the extension part 47 has a width of 2 mm, a thickness of 0.1 mm, and a length of 71 nm.
By setting rIL, trap points 49 and 50 are 9 dB
The extension part 47 has a width of 2 mm and a thickness of 0.1 mm.
By setting the length to 4 mm, the trap point is 49,5
0 was able to improve by 3dB.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the figure, the same reference numerals as in FIG. 1 indicate the same parts. That is, a portion of the circuit board 51 including a printed wiring section 52 connected to the signal input terminal 18, printed wiring sections 53 and 54 connected to the output terminals 19 and 20, and ground terminals 17 and 21 becomes a ground section 55. The circuit board is the same as the conventional circuit board, but in this embodiment, the signal input terminal 18 and the output terminal 19 are
An extension part 5 is connected to the printed wiring part 53 including the output terminal 19 and extends in the direction of the signal input terminal 18 along a straight line (referred to as a diagonal direction in the present invention) 56 connecting the intermediate part between .
By providing 7, the signal input terminal 18 and the output terminal 1
It is characterized by preventing induction between 9 and 20.

Next, a third embodiment of the present invention will be described with reference to FIG.

The same parts as in FIG. 1 are shown in the figure. That is, the circuit board 61 has a printed wiring section 62 connected to the signal input terminal 18 along a straight line connecting the intermediate portion between the signal input terminal 18 and the output terminals 19 and 20, that is, a diagonal direction 66, and the output terminals 19 and 20.
The printed wiring parts 63 and 64 connected to the ground terminal 1
The portion including 7.21 is a grounding portion 65.

That is, in this embodiment, the printed wiring sections 62, 63, and 64 are formed almost symmetrically with respect to the straight line 66.

By doing this, induction between the signal input terminal 18 and the output terminals 19 and 20 can be prevented, as in the other embodiments described above, but there is an advantage that the circuit board 61 can be manufactured easily.

Of course, various modifications can be made in addition to the embodiments described above.

As described above, according to the present invention, it is possible to improve the frequency characteristics of a surface wave filter element, and its industrial value is extremely high.

[Brief explanation of the drawing]

Figure 1 is a simplified explanatory diagram of a surface wave filter element, Figure 2 is an explanatory diagram showing a conventional circuit board for a surface wave filter element, and Figure 3 is an explanatory diagram showing a conventional surface wave filter element circuit board.
The figure is a frequency characteristic curve diagram of the surface wave filter element when the circuit board shown in Fig. 2 is used, Fig. 4 is an explanatory diagram showing the first embodiment of the present invention, and Fig. 5 is the circuit board shown in Fig. 4. FIG. 6 is an explanatory diagram showing the second embodiment of the present invention, and FIG. 7 is an explanatory diagram showing the third embodiment of the present invention. . 15... Piezoelectric substrate, 17, 18, 19, 20° 21... Stem pin, 31, 41, 5L61.
...Circuit board for surface wave filter element, 36, 48
...Frequency characteristic curve.

Claims (1)

[Scope of Claims] 1. A piezoelectric substrate having an input electrode and an output electrode each consisting of a pair of comb-shaped electrodes is mounted and fixed on a stem, and one of the input electrodes is led to a stem pin directly implanted in the stem. The other is electrically connected to a stem pin implanted in the stem via an insulating member to serve as a signal input terminal, and the pair of output electrodes are respectively implanted in the stem via an insulating material. The surface wave filter element is connected to a circuit board having a printed wiring having a predetermined shape via the respective stem pins. In the surface acoustic wave device, an extending portion extending in the direction of the signal input terminal is formed in a printed wiring portion to which an output terminal of the pair of output elements diagonally to the signal input terminal is fixed. Circuit board for filter element. 2. A piezoelectric substrate having an input electrode and an output electrode each consisting of a pair of comb-shaped electrodes is mounted and fixed on a stem, and one of the input electrodes is electrically connected to a stem pin directly implanted in the stem to serve as a ground terminal, The other electrode is electrically connected to a stem pin implanted in the stem via an insulating member to serve as a signal input terminal, and the pair of output electrodes is electrically connected to a stem pin implanted in the stem via an insulator, respectively. 1
In a circuit board for a surface wave filter element configured to connect a surface wave filter element as a pair of output terminals to a circuit board having printed wiring of a predetermined shape via the respective stem pins, A printed wiring part to which the signal input terminal is fixed is provided along a straight line connecting an intermediate part of the terminal and the signal input terminal, and a printed wiring part to which a pair of output terminals are fixed is provided substantially symmetrically along the straight line. A circuit board for a surface wave filter element, characterized in that: