US3716808A
Expired / Lapsed
US
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Bandpass filter including monolithic crystal elements with resonating portions selected for symmetrical response
Assignee: Motorola Solutions Inc
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Filing: 1971-05-20
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Granted: 1973-02-13
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Expires: 1991-05-20
Abstract
Abstract A bandpass filter circuit includes a pair of dual coupled monolithic crystal filter elements each formed by a wafer of quartz, or other piezoelectric material, with two pairs of electrodes thereon, each pair cooperating with the wafer to form a resonating portion. The two dual coupled crystal elements are cascade coupled, with the signal to be selected applied to the first pair of electrodes on the first element, then coupled from the second pair of electrodes of the first element to the first pair of electrodes of the second element, and the selected signal derived from the second pair of electrodes of the second element. To reduce the requirement for inductive coupling elements in the filter, the monolithic filter elements are constructed so that the resonant frequencies of certain resonating portions thereof are below the mesh frequencies of the filter, which are at the center frequency of the filter. To provide a filter response characteristic having improved selectivity, i.e. steep skirts, a capacitor is bridged across the electrodes of at least one of the crystal elements. This causes a non-symmetrical response, and to correct this, the filter elements are constructed so that the resonant frequency of one resonating portion of at least one of the crystal elements is increased.
Inventors
- 👤 C Smith
- 👤 S Malinowski
- 👤 J Dailing
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 17:59
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/54; H03H9/542
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
141 words
A monolithic filter for providing a symmetrical response about a given center frequency including a piezoelectric resonating element having first and second opposite sides with first and second pairs of electrodes thereon and the electrodes of each pair being on opposite sides of the resonating element, means coupled to said first pair of electrodes for applying signals thereto, means coupled to said second pair of electrodes for deriving selected signals therefrom, and capacitor means connected between one electrode of each pair which is on the same side of said resonating element, said resonating element and said first pair of electrodes thereon being constructed to be resonant at a first frequency below the center frequency of the filter, and said resonating element and said second pair of electrodes thereon being constructed to be resonant at a second frequency above said first frequency.
Claim 2
Dependent Claim
141 words
A monolithic filter for providing a symmetrical response about a given center frequency including a piezoelectric resonating element having first and second opposite sides with first and second pairs of electrodes thereon and the electrodes of each pair being on opposite sides of the resonating element, means coupled to said first pair of electrodes for applying signals thereto, means coupled to said second pair of electrodes for deriving selected signals therefrom, and capacitor means connected between one electrode of each pair which is on the same side of said resonating element, said resonating element and said first pair of electrodes thereon being constructed to be resonant at a first frequency below the center frequency of the filter, and said resonating element and said second pair of electrodes thereon being constructed to be resonant at a second frequency above said first frequency.
Claim 3
Dependent Claim
141 words
A monolithic filter for providing a symmetrical response about a given center frequency including a piezoelectric resonating element having first and second opposite sides with first and second pairs of electrodes thereon and the electrodes of each pair being on opposite sides of the resonating element, means coupled to said first pair of electrodes for applying signals thereto, means coupled to said second pair of electrodes for deriving selected signals therefrom, and capacitor means connected between one electrode of each pair which is on the same side of said resonating element, said resonating element and said first pair of electrodes thereon being constructed to be resonant at a first frequency below the center frequency of the filter, and said resonating element and said second pair of electrodes thereon being constructed to be resonant at a second frequency above said first frequency.
Claim 4
Dependent Claim
141 words
A monolithic filter for providing a symmetrical response about a given center frequency including a piezoelectric resonating element having first and second opposite sides with first and second pairs of electrodes thereon and the electrodes of each pair being on opposite sides of the resonating element, means coupled to said first pair of electrodes for applying signals thereto, means coupled to said second pair of electrodes for deriving selected signals therefrom, and capacitor means connected between one electrode of each pair which is on the same side of said resonating element, said resonating element and said first pair of electrodes thereon being constructed to be resonant at a first frequency below the center frequency of the filter, and said resonating element and said second pair of electrodes thereon being constructed to be resonant at a second frequency above said first frequency.
Claim 5
Dependent Claim
19 words
A filter in accordance with claim 1 wherein said second frequency is substantially the center frequency of the filter.
Claim 6
Dependent Claim
19 words
A filter in accordance with claim 1 wherein said second frequency is above the center frequency of the filter.
Claim 7
Dependent Claim
33 words
A filter in accordance with claim 3 wherein said second frequency is above the center frequency of the filter by substantially the same amount that said first frequency is below the center frequency.
Claim 8
Dependent Claim
184 words
A monolithic crystal filter circuit for providing a symmetrical bandpass about a given center frequency, including in combination, first and second piezoelectric crystal elements each having first and second spaced pairs of electrodes thereon forming first and second resonating portions coupled through the crystal element, means coupled to said first pair of electrodes of said first element for applying signals thereto, means coupled to said second pair of electrodes of said first element and to said first pair of electrodes of said second element for coupling signals from said first element to said second element, means coupled to said second pair of electrodes of said second elements for deriving selected signals therefrom, said second resonating portions of said first element and said first resonating portions of said second element being constructed to be resonant at a first frequency below the center frequency of the filter, and capacitor means connected between said first and second pairs of electrodes of one of said piezoelectric elements, said one piezoelectric element having a resonating portion thereof constructed to be resonant at a second frequency above said first frequency.
Claim 9
Dependent Claim
184 words
A monolithic crystal filter circuit for providing a symmetrical bandpass about a given center frequency, including in combination, first and second piezoelectric crystal elements each having first and second spaced pairs of electrodes thereon forming first and second resonating portions coupled through the crystal element, means coupled to said first pair of electrodes of said first element for applying signals thereto, means coupled to said second pair of electrodes of said first element and to said first pair of electrodes of said second element for coupling signals from said first element to said second element, means coupled to said second pair of electrodes of said second elements for deriving selected signals therefrom, said second resonating portions of said first element and said first resonating portions of said second element being constructed to be resonant at a first frequency below the center frequency of the filter, and capacitor means connected between said first and second pairs of electrodes of one of said piezoelectric elements, said one piezoelectric element having a resonating portion thereof constructed to be resonant at a second frequency above said first frequency.
Claim 10
Dependent Claim
35 words
A filter in accordance with claim 5 wherein said first frequency is below the center frequency of the filter by an amount of the order of 30 percent of the bandwidth of the filter circuit.
Claim 11
Dependent Claim
19 words
A filter in accordance with claim 5 wherein said second frequency is substantially the center frequency of the filter.
Claim 12
Dependent Claim
19 words
A filter in accordance with claim 5 wherein said second frequency is above the center frequency of the filter.
Claim 13
Dependent Claim
34 words
A filter in accordance with claim 8 wherein said second frequency is above the center frequency of the filter by substantially the same amount that said first frequency is below the center frequency thereof.
Claim 14
Dependent Claim
43 words
A filter in accordance with claim 5 wherein said capacitor means is connected between said first and second pairs of electrodes of said second element, and said second resonating portion of said second element is constructed to be resonant at said second frequency.
Claim 15
Dependent Claim
28 words
A filter in accordance with claim 10 wherein said first resonating portion of said first element is constructed to be resonant at a frequency above said first frequency.
Claim 16
Dependent Claim
38 words
A filter in accordance with claim 10 wherein said first resonating portion of said first element is constructed to be resonant at said second frequency, and said second frequency is at substantially the center frequency of the filter.
Claim 17
Dependent Claim
43 words
A filter in accordance with claim 10 wherein said second frequency is above the center frequency of the filter, and said first resonating portion of said first element is constructed to be resonant at a frequency above the center frequency of the filter.
Claim 18
Dependent Claim
57 words
A filter in accordance with claim 5 including first and second capacitor means connected between said first and second pairs of electrodes of said first and second elements, respectively, and wherein said first resonating portion of said first element and said second resonating portion of said second element are constructed to be resonant above said first frequency.
Claim 19
Dependent Claim
34 words
A filter in accordance with claim 14 wherein said first resonating portion of said first element and said second resonating portion of said second element are resonant above the center frequency of the filter.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-13 | 1976-08-14 | 1977-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-13 | 1980-08-14 | 1981-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-13 | 1984-08-14 | 1985-02-13 | $7700.00 | Window Closed / Lapsed |