JPS5845207B2 - Polar mechanical filter - Google Patents

Description

Detailed Description of the Invention The present invention provides a mechanical filter comprising a cascade connection of a bending transverse vibrating sound bar resonator and a longitudinal vibrating thin bar coupler, which is a polarized mechanical filter that is easy to manufacture and has less harmful spurious response. It is related to filters.

A well-known method for polarizing a mechanical filter is to skip over an adjacent resonator and couple it to another resonator using an additional coupler.

Therefore, in order to have one pole each in the low and high attenuation regions of the passband, an additional coupler is used to couple the resonators with an even number of resonators in between, and the cut-off It is also well known that vibrations propagated through the main coupler and vibrations propagated by the additional coupler are connected so as to cancel each other out in a low-frequency damping region close to .

Figure 1 shows a mechanical filter that is based on the above-mentioned technical thinking and is made up of a cascade connection of a bending transverse vibrating transducer resonator and a longitudinally vibrating thin bar coupler, and has two attenuation poles in each attenuation region on both sides of the pass band. 1 is a perspective view showing the conventional structure of a nine-element polarized mechanical filter having the following characteristics.

In the figure, 1.1' is a sound piece made of a constant elastic material of nickel-span C type, and a conversion resonator is formed by pasting piezoelectric ceramic plates 2, 2' (not visible in the figure) such as PZT.

Reference numerals 3, 4, . . . 9 are resonators made of constant elastic materials, and all of them perform first-mode bending transverse vibration as shown by broken lines.

Reference numerals 10, 11, . . . , 17 are thin rods made of a constant elastic material and are main connectors that propagate longitudinal vibrations, and are butt-welded at the center of the layer lines of each resonator.

Reference numerals 18 and 19 are thin rods made of constant elastic material and are additional coupling elements that propagate longitudinal vibrations.

18 and 19 are the side surfaces 20 of the resonators 3 and 5, and 6 and 9, which sandwich 3, 4, 7, and 82 resonators, respectively.
．． Welded connections are made at 21 and 22.23.

As is well known, each resonator of the filter vibrates in the same phase in the lower attenuation region as shown by the broken line, so the weld distance of 18°19, that is, the effective length l, is equal to the longitudinal vibration propagating within 18.19. Where λ is the wavelength, λ/2<j? <λ.

In the conventional structure as described above, the resonators 3, 9 and 6 generate useless couplets from the additional couplers 18, 19 and from both 18°19 in the plane containing the main coupler and the additional coupler. It has the disadvantage that it receives vibrational force (for example, as shown by arrow 24) and induces useless vibrations, causing spurious responses.

The present invention has been made to eliminate the above-mentioned drawbacks.
This will be explained in detail below.

2 and 3 are perspective views showing embodiments of the present invention, respectively.1.
1', 2.2'4.5, 7, 8, 10.11...17
Everything up to this point is the same as that shown in FIG. 1 with the same reference numerals.

A feature of the present invention is that the resonators 3', 6', 9' that couple the additional couplers 18', 19' use second-mode bending transverse vibrating bars as shown by broken lines.

Therefore, the center points of the vibration layer lines at two points 3', 6', and 9' are 25, 26 (both not visible in the figure), 2γ, 28°, 27', 28'(27',28' are not visible in the figure). (not visible) 25, 2γ, 27', 29 of 2930 are main connectors 1
113, 14, and 16 are butted and welded to 26°28.
At 28' and 30, the additional connectors is' and is' are butt welded.

The lengths of the additional connectors 18' and 19' are 3/, 5/,
Since the phase relationship of the vibrations 9/ is in the same phase as shown by the broken line in the lower attenuation region, of course λ/2<1<λ.

The difference between Figures 2 and 3 is, as is clear from the diagram, whether the vibration plane directions of resonators 3', 6', and 9' are in the same direction as the vibration planes of the other resonators or at right angles. It is.

According to the structure of the present invention as described above, 3/, 6/, g
/In each vibrating bar, the vibration force acts on the center of the two layer lines, and useless couple vibration forces do not act, so harmful spurious responses are less likely to occur, and the main connector and additional connector All are joined at the center of the vibration layer line of the resonator, so even slight deviations in the joining position have little negative effect on the overall characteristics, and practical effects such as increasing manufacturing tolerances. There is.

The above description has been about a case in which an additional coupler is used to connect resonators that sandwich an even number of resonators, but the present invention provides an additional coupling between resonators that are sandwiched between an odd number of resonators. Of course, it can also be used in a polarized mechanical filter that combines the two and has one attenuation pole on the high-frequency side or the low-frequency side of the attenuation range.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of a conventional polarized mechanical filter, Fig. 2 is a perspective view showing an embodiment of the present invention, and Fig. 3 is a perspective view showing an example of a conventional polarized mechanical filter.
The figure is a perspective view showing another embodiment of the present invention. 1, F... Conversion resonator, 3', 4, 5.6'
,? . 8.9'... Main resonator, 10-11...
・Main connector, 18', 19'...Additional connector.

Claims (1)

[Claims] 1 A mechanical filter consisting of a cascade connection of a bending transverse vibrating acoustic bar resonator and a longitudinal vibrating thin rod coupler, in which the adjacent resonator is skipped and the other resonator is coupled with an additional coupler. In the polarized mechanical filter, the resonator to which the additional coupler is connected is a resonator that performs second-mode bending transverse vibration, and the other resonators are resonators that perform first-mode bending transverse vibration. 1. A polarized mechanical filter characterized in that a coupler and an additional coupler are butt-welded at the center of the vibration layer line of a resonator.