MULTISECTION PRECISION-TUNED MONOLITHIC CRYSTAL FILTERS

• US 3,732,510 A
• Filed: 10/12/1970
• Issued: 05/08/1973
• Est. Priority Date: 10/12/1970
• Status: Expired due to Term

• Current Assignee: Warren Perry Mason
• Original Assignee: Warren Perry Mason
• Inventors: Mason, Warren Perry
• Primary Examiner(s): Saalbach, Herman Karl
• Assistant Examiner(s): Chatmon, Jr., Saxfield
• Application Number:
  US05/079,881
• Time in Patent Office: 939 Days
• Field of Search: 333/72,30,71 310/8.2,9.5
• US Class Current: 333/191
• CPC Class Codes: H03H 9/566 Electric coupling means therefor H03H9/0095 takes precedence

Abstract

In a monolithic crystal filter characterized by a combination of mass loading and acoustic coupling, passband shaping is enhanced by shunting one or more intermediate electrode pairs with a reactive element. Precision tuning is achieved by varying the plating on a desired intermediate filter section with adjacent sections either open-circuited or reactively shunted.

Claims

1. A monolithic crystal filter comprising, in combination, input and output electrode pairs and at least one intermediate electrode pair, a common piezoelectric wafer sandwiched between each of said pairs, means for applying an electrical signal to said input electrode pair, means for extracting a translation of said electrical signal from said output electrical pair;

and a floating, ungrounded, conducting path including a reactive element shunting said one intermediate electrode pair.

2. Apparatus in accordance with claim 1 wherein said element is a capacitor.

3. Apparatus in accordance with claim 1 wherein said element is an inductor.

4. A monolithic crystal filter comprising, in combination, input and output electrode pairs;

a plurality of intermediate electrode pairs;

a common piezoeleCtrice body sandwiched between each of said pairs, and a floating, ungrounded, conducting path including reactive means shunting at least one of said intermediate electrode pairs;

each of said intermediate electrode pairs not shunted by one of said reactive means being short-circuited.

5. A method for adjusting the bandpass characteristics of a monolithic crystal filter having a piezoelectric body sandwiched between a plurality of pairs of electrodes including an input pair, an output pair, and at least one intermediate pair, comprising the steps of:

open-circuiting those electrode pairs adjacent to the electrode pair of the filter section to be tuned;

adjusting the frequency of said last named section by changing the mass loading thereof, and short-circuiting all intermediate ones of said electrode pairs.

6. A method for adjusting the bandpass characteristics of a monolithic crystal filter having a piezoelectric body sandwiched between a plurality of pairs of electrodes including an input pair, an output pair, and at least one intermediate pair, said method including the steps of:

shunting by reactive means those electrode pairs adjacent to the electrode pair of the section to be tuned, open-circuiting said last named electrode pair, adjusting the frequency of said section to be tuned by adjusting the mass loading of said last named electrode pair, and short-circuiting all of said intermediate pairs.

7. A method for adjusting the resonant characteristics of one section of a multisection monolithic crystal filter wherein said sections include an input electrode pair, an output electrode pair and at least one intermediate electrode pair and each of said electrode pairs sandwiches a common piezoelectric body therebetween, said method including the steps of:

open-circuiting the electrode pair of the section to be adjusted, open-circuiting each of the electrode pairs adjacent to the section to be adjusted, and adjusting the resonant frequency of the section to be tuned by adjusting the mass loading of the corresponding electrode pair.

8. A method for adjusting the resonant characteristics of one section of a multisection monolithic crystal filter wherein said sections include an input electrode pair, an output electrode pair and at least one intermediate electrode pair, and each of said electrode pairs sandwiches a common piezoelectric body therebetween, said method including the steps of:

open-circuiting the electrode pair of the section to be tuned, shunting each of the electrode pairs adjacent to said section to be tuned with a respective reactive element, and adjusting the resonant frequency of said section to be tuned by adjusting the mass loading of said last named electrode pair.

9. The method in accordance with claim 8 further including the steps of:

short-circuiting all of said reactive pairs and removing each of said respective reactive element.