US5107220A
Expired / Lapsed
US
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Frequency synthesizer
Assignee: Mitsubishi Electric Corp
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Filing: 1991-04-09
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Granted: 1992-04-21
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Expires: 2011-04-09
Abstract
Abstract A frequency synthesizer includes a control circuit which outputs changeover signals for bringing one of a number of filters included in a loop filter into electrical connection with a VCO outputting a desired frequency signal, such that a phase difference signal passes through one filter when a demand for frequency changeover is made, and provides a frequency division ratio corresponding to said one filter to a variable frequency divider and a reference frequency divider whose phases are compared to produce the phase difference signal. In addition, the control circuit successively supplies changeover signals for performing selection of respective filters through each of which the phase difference signal passes, and provides frequency division ratios corresponding to filters tuned to the variable frequency divider and the reference frequency divider to change the output frequency of the VCO incrementally. Furthermore, the control circuit provides changeover signals for connection filters employed in a steady state. The time required between each step in the frequency changeover process can be shortened by setting a time constant for each of the filters to a value such that an intermediate output signal representative of a frequency determined by the frequency division ratio corresponding to each filter is stabilized in a short period of time.
Inventors
- 👤 Akira Andoh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:46
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/06; H03L7/08; H03L7/10; H03L7/107; H03L7/1075; H03L7/16; H03L7/18; H03L7/197; H03L7/1972; H03L7/085; H03L7/089; H03L7/0891
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
144 words
A frequency synthesizer, comprising: a voltage controlled oscillator (VCO) for generating an output signal having a frequency corresponding to a control voltage signal; and means for switching said control voltage signal from a first value corresponding to a first output frequency to a second value corresponding to a second desired frequency, including means for changing said control voltage signal from said first value to at least one intermediate value corresponding to an intermediate frequency between said first output frequency and said second desired frequency, filter means for outputting said control voltage signal to said VCO and having a plurality of selectable frequency characteristics, and control means for providing command signals to said means for changing and to said filter to select frequency characteristics of said filter corresponding to said intermediate frequency when said at least one value is selected by said means for changing.
Claim 2
Dependent Claim
144 words
A frequency synthesizer, comprising: a voltage controlled oscillator (VCO) for generating an output signal having a frequency corresponding to a control voltage signal; and means for switching said control voltage signal from a first value corresponding to a first output frequency to a second value corresponding to a second desired frequency, including means for changing said control voltage signal from said first value to at least one intermediate value corresponding to an intermediate frequency between said first output frequency and said second desired frequency, filter means for outputting said control voltage signal to said VCO and having a plurality of selectable frequency characteristics, and control means for providing command signals to said means for changing and to said filter to select frequency characteristics of said filter corresponding to said intermediate frequency when said at least one value is selected by said means for changing.
Claim 3
Dependent Claim
129 words
A frequency synthesizer according to claim 1, wherein said means for changing comprises: a variable frequency divider for dividing the frequency of said output signal of said VCO by a frequency division ratio corresponding to a command signal from said control means; a reference frequency divider for dividing a frequency of a reference signal by a frequency division ratio corresponding to a command signal from said control means; a phase detector for detecting a phase difference between the frequency-divided signals of said variable frequency divider and said reference frequency divider and outputting a phase difference signal corresponding to the detected phase difference; and a charge pump for converting said phase difference signal into an analog voltage quantity as a control voltage signal which is applied to said filter means.
Claim 4
Dependent Claim
58 words
A frequency synthesizer according to claim 2, wherein said filter means comprises: a plurality of filter circuits each having a time constant corresponding to particular frequency division ratios; and switching means for connecting and disconnecting each of said plurality of filter circuits to said VCO and said charge pump in accordance with command signals from said control means.
Claim 5
Dependent Claim
117 words
A frequency synthesizer according to claim 3, wherein said means for changing changes said control voltage signal from said first value to a first intermediate value corresponding to a first intermediate frequency, from said first intermediate value to a second intermediate value corresponding to a second intermediate frequency, and from said second intermediate value to said second value corresponding to said second desired frequency, and said plurality of filter circuits comprises a first filter circuit having a time constant corresponding to said first intermediate value, a second filter circuit having a time constant corresponding to said second intermediate value, and a third filter circuit having a time constant corresponding to said first value and said second value.
Claim 6
Dependent Claim
34 words
A frequency synthesizer according to claim 4, wherein said third filter circuit is connected to said VCO and said charge pump in a steady state mode of operation, and includes a low pass filter.
Claim 7
Dependent Claim
53 words
A frequency synthesizer according to claim 5, wherein said filter means further comprises: charge/discharge means for charging and discharging capacitors of filter circuits disconnected from said VCO and said charge pump to a voltage equal to said control voltage signal outputted by a filter circuit connected to said VCO and said charge pump.
Claim 8
Dependent Claim
46 words
A frequency synthesizer according to claim 6, wherein said charge/discharge means comprises a voltage follower for receiving a voltage from said charge pump, and a plurality of switches for selectively connecting an output of said voltage follower to each of said capacitors of said filter circuits.
Claim 9
Dependent Claim
43 words
A frequency synthesizer according to claim 7, wherein said control means stores information regarding the time required for said control voltage to enter a steady state for each of said filter circuits, and updates said command signals upon the expiration of said time.
Claim 10
Dependent Claim
49 words
A frequency synthesizer according to claim 2, further comprising a phase synchronous detector for detecting a coincidence in phase between said variable frequency divider and said reference frequency divider and outputting a phase coincidence signal to said control means to cause said control means to update said command signals.
Claim 11
Dependent Claim
49 words
A frequency synthesizer according to claim 6, further comprising a phase synchronous detector for detecting a coincidence in phase between said variable frequency divider and said reference frequency divider and outputting a phase coincidence signal to said control means to cause said control means to update said command signals.
References Cited (Backward Citations)
US4893087A
Cited
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1995-04-21 | 1995-10-21 | 1996-04-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-04-21 | 1999-10-21 | 2000-04-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-04-21 | 2003-10-21 | 2004-04-21 | $7700.00 | Window Closed / Lapsed |