Type of ultra-wide band SAW filter

Abstract

The present invention discloses a type of ultra-wide band SAW filter which comprises a first SAW resonator group and a second SAW resonator group that are connected to form a ladder structure. Each SAW resonator in the said first SAW resonator group has the same film thickness; each SAW resonator in the said second SAW resonator group has the same film thickness; the film thickness of each SAW resonator in the said first SAW resonator group is the same as or different from the film thickness of each SAW resonator in the said second SAW resonator group. The SAW filter according to the present invention can realize the pass-band non-parasitic mode response and is a high-performance ultra-wide band filter with a bandwidth of 6-20% of the center frequency and an insertion loss of less than 2 dB, and the present invention features small size, low cost and a broad application prospect in the field of military and civilian communications equipment.

Claims

1. A type of ultra-wide band SAW filter, comprising a first SAW resonator group and a second SAW resonator group that are connected to form a ladder structure, wherein each SAW resonator in the first SAW resonator group has a same first film thickness, each SAW resonator in the second SAW resonator group has a same second film thickness and the first film thickness is different from the second film thickness, wherein the first film thickness and the second film thickness are selected to eliminate a parasitic mode in a passband of the SAW filter.

2. The ultra-wide band SAW filter according to claim 1, wherein, the said SAW resonators of the first and second SAW resonator groups are made on the dielectric substrates which are made of a Y-rotated 0-64° lithium niobate material.

3. The ultra-wide band SAW filter according to claim 1, further comprising electrodes connected to the first and second SAW resonator groups; the electrodes being made of copper, tungsten, gold or platinum material.

Description

BRIEF DESCRIPTION OF DRAWINGS

Description of Drawings

(1) FIG. 1 is a structural diagram of the present invention.

(2) FIG. 2 is a cross-sectional view of the structure of the present invention.

(3) FIG. 3 is a simulation result diagram of one embodiment of the present invention.

INVENTION EMBODIMENTS

Embodiments of the Present Invention

(4) FIG. 1 is a structural diagram of the present invention. FIG. 2 is a cross-sectional view of the structure of the present invention. As shown in FIGS. 1 and 2, the present invention comprises dielectric substrates 10 on which the series SAW resonator groups 3, 4, 5 & 6 and the parallel SAW resonator groups 7, 8 & 9 are mounted. The series SAW resonator groups 3, 4, 5 & 6 and the parallel SAW resonator groups 7, 8 & 9 are connected to form a ladder structure. The ladder structure that is formed by four series SAW resonators and three parallel SAW resonators as shown in FIG. 1 is used in the present embodiment. The number of series SAW resonators and parallel SAW resonators may be increased or decreased depending on the different design requirements such as different center frequencies and bandwidths. The ladder structure has excellent stop-band suppression performance and can guarantee the performance of the filter in the stop-band.

(5) The series SAW resonator groups 3, 4, 5 & 6 are H1 in thickness while the parallel SAW resonator groups 7, 8 & 9 are H2 in thickness. In the present invention, the SAW filter utilizes two groups of SAW resonator arrays with different thicknesses to optimize the series and parallel SAW resonators respectively so as to eliminate the parasitic mode and utilizes the gap between the film thicknesses to further widen the bandwidth of the filter. As shown in FIG. 2, H1=H2 in the present embodiment, preferably, H1 H2.

(6) The dielectric substrates 10 are made of the Y-rotated 0-64° lithium niobate material. Such piezoelectric material has a large electromechanical coupling coefficient, which is beneficial to the transmission of the pass-band signal and can guarantee that the filter has a low insertion loss in the wide pass-band range.

(7) A first electrode 1 and a second electrode 2 are connected to both ends of the series SAW resonator groups 3, 4, 5 & 6 respectively and serve as the input and output of the SAW filter. A first electrode 1 and a second electrode 2 are made of such heavy metal materials as copper, tungsten, gold or platinum.

(8) The present invention utilizes the large electromechanical coupling coefficient of the lithium niobate substrate, selects heavy metals such as copper, tungsten, gold or platinum as the electrode material and achieves the fabrication of the filter according to the present invention through designing the combination of two groups of ladder resonators with different thicknesses in conjunction with the micro-processing technology and two processes of graphic processing.

(9) In the present invention, the said design achieves a type of ultra-wide band SAW filter with a very low insertion loss through clever combination of material, structure and process.

(10) Only one preferred embodiment of the present invention is stated above and the present invention is not limited to the above-mentioned embodiment. It can be understood that any other improvements and changes that are directly derived or associated by the technicians in this filed from or with the spirit and idea of the present invention shall be deemed to be included within the protection scope of the present invention.