US5874866A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Phase-shift oscillator having ladder-type saw filter feedback circuit
Assignee: Fujitsu Ltd
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Filing: 1997-09-25
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Granted: 1999-02-23
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Expires: 2017-09-25
Abstract
Abstract An oscillation circuit of phase-shift type includes a surface acoustic wave filter in a feedback circuit, the surface acoustic wave filter having first and second one-port surface acoustic wave resonators of different resonance frequencies connected in a ladder configuration. The oscillation circuit has a high C/N ratio with a large bandwidth of variable frequency and can be fabricated in a small size with low costs.
Inventors
- 👤 Yoshio Satoh
- 👤 Osamu Ikata
- 👤 Takashi Matsuda
- 👤 Yoshitaka Takahashi
- 👤 Ivan Dimitrov Avramov
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 00:59
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6423; H03H9/6433; H03H9/6483; H03B; H03B5/00; H03B5/30; H03B5/32; H03B5/326
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
39 words
An oscillation circuit of phase-shift type comprising a surface acoustic wave filter in a feedback circuit, the surface acoustic wave filter having first and second one-port surface acoustic wave resonators of different resonance frequencies connected in a ladder configuration.
Claim 2
Dependent Claim
39 words
An oscillation circuit of phase-shift type comprising a surface acoustic wave filter in a feedback circuit, the surface acoustic wave filter having first and second one-port surface acoustic wave resonators of different resonance frequencies connected in a ladder configuration.
Claim 3
Dependent Claim
91 words
An oscillation circuit according to claim 1, wherein the surface acoustic wave filter includes a plurality of the first one-port surface acoustic wave resonators disposed in a parallel arm and a plurality of the second one-port surface acoustic wave resonators disposed in a series arm, the first one-port surface acoustic wave resonators each having a predetermined resonance frequency f rp and an anti-resonance frequency f ap , and the second one-port surface acoustic wave resonators each having a resonance frequency f rs approximately equal to the anti-resonance frequency f as .
Claim 4
Dependent Claim
120 words
An oscillation circuit according to claim 2, wherein the resonance frequency f rs of the second one-port surface acoustic wave resonator in the series arm is larger than the anti-resonance frequency f ap of the first one-port surface acoustic wave resonator in the parallel arm and a value obtained by normalizing a difference Δf=f rs -f ap with the resonance frequency f rs is greater than 0 and smaller than α which is given by the following formula: ##EQU4## wherein Cop represents a static capacitance of the first one-port surface acoustic wave resonator in the parallel arm, Cos represents a static capacitance of the second one-port surface acoustic wave resonator in the series arm, and γ represents a capacitance ratio.
Claim 5
Dependent Claim
100 words
An oscillation circuit according to claim 2 or 3, wherein the first one-port surface acoustic wave resonator and the second one-port surface acoustic wave resonator are designed to satisfy the following inequality: Cop/Cos<-0.32+2.82/n, wherein Cop represents a static capacitance of the first one-port surface acoustic wave resonator in the parallel arm, Cos represents a static capacitance of the second one-port surface acoustic wave resonator in the series arm, and n is the number of stages connected in cascade configuration when the first one-port surface acoustic wave resonator and the second one-port surface acoustic wave resonator are counted as a unit.
Claim 6
Dependent Claim
42 words
An oscillation circuit according to claim 4, wherein an arithmetic mean of Cop/Cos in the stages is smaller than -0.32+2.82/n if the value Cop/Cos of the pair of the first and second one-port surface acoustic wave resonators differs from stage to stage.
Claim 7
Dependent Claim
35 words
An oscillation circuit according to claim 1 or 2, wherein a phase change of phase characteristics in the passband of the surface acoustic wave filter is within the range of 0 degrees to 160 degrees.
Claim 8
Dependent Claim
33 words
An oscillation circuit according to claim 4, wherein a phase change of phase characteristics in the passband of the surface acoustic wave filter is within the range of 0 degrees to 160 degrees.
Claim 9
Dependent Claim
39 words
An oscillation circuit according to claim 1, 2, or 3, wherein the surface acoustic wave filter is formed on a piezoelectric single-crystal substrate selected from the group consisting of LiTaO 3 , LiNbO 3 , and KNbO 3 .
Claim 10
Dependent Claim
36 words
An oscillation circuit according to claim 4, wherein the surface acoustic wave filter is formed on a piezoelectric single-crystal substrate selected from the group consisting of LiTaO 3 , LiNbO 3 , and KNbO 3 .
Claim 11
Dependent Claim
36 words
An oscillation circuit according to claim 5, wherein the surface acoustic wave filter is formed on a piezoelectric single-crystal substrate selected from the group consisting of LiTaO 3 , LiNbO 3 , and KNbO 3 .
Claim 12
Dependent Claim
36 words
An oscillation circuit according to claim 6, wherein the surface acoustic wave filter is formed on a piezoelectric single-crystal substrate selected from the group consisting of LiTaO 3 , LiNbO 3 , and KNbO 3 .
Claim 13
Dependent Claim
36 words
An oscillation circuit according to claim 7, wherein the surface acoustic wave filter is formed on a piezoelectric single-crystal substrate selected from the group consisting of LiTaO 3 , LiNbO 3 , and KNbO 3 .
References Cited (Backward Citations)
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| 3.5 Years (Year 4) | 2002-02-22 | 2002-08-24 | 2003-02-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-02-22 | 2006-08-24 | 2007-02-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-02-22 | 2010-08-24 | 2011-02-23 | $7700.00 | Window Closed / Lapsed |