JP2004179706A - Two-frequency switching crystal oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-frequency switching oscillator which is easily designed by adopting an optimum condition for each frequency band. <P>SOLUTION: The oscillator is provided with first and second crystal oscillators each composed of an oscillation circuit 3 including a crystal vibrator, first and second electronic switches are placed between the first crystal oscillator and a power supply and between the second crystal oscillator and the power supply, respectively, third and fourth switches are placed at outputs of the first and second crystal oscillators, and connected in common to form an output terminal, and the first switch and the third switch, and the second switch and the fourth switch are configured such that on / off-operations of them are inverted to each other. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dual-frequency switching type crystal oscillator (hereinafter, referred to as a dual-frequency switching oscillator) that selectively uses two oscillation frequencies for use in an industrial technical field, and in particular, selectively selects a load resistance value of a crystal oscillator. The present invention relates to a crystal oscillator that is different from the above.
[0002]
[Prior art]
BACKGROUND OF THE INVENTION Crystal oscillators are used in particular as frequency reference sources and are applied, for example, in optical communication systems. In recent years, there is a case where it is desired to use, for example, one of a 150 MHz band and a 600 MHz band in a system, and a dual frequency switching oscillator is required (Patent Documents 1 and 2).
[0003]
FIG. 3 is a block diagram of a crystal oscillator for explaining a conventional example.
The two-frequency switching oscillator includes first and second quartz oscillators 1 (ab) having different oscillation frequencies in a 150 MHz band and a 600 MHz band, and is connected to an oscillation circuit 3 by an electronic switch 2. The electronic switch is composed of, for example, a transistor, and the oscillation circuit 3 is, for example, a Colpitts type having an oscillation amplifier (not shown). Normally, as shown in FIG. 4, the voltage variable capacitance element 4 is inserted into the oscillation closed loop to be of a voltage control type. Reference numeral 5 in the drawing is a high-frequency element resistance.
[0004]
[Problems to be solved by the invention]
(Problems of the prior art) However, the two-frequency switching oscillator configured as described above shares the 150 MHz and 600 MHz band oscillation circuits 3. Therefore, the oscillating circuit 3 must satisfy the oscillating conditions in any frequency band, making it impossible to apply optimum conditions for each frequency band and making the design difficult.
(Object of the Invention) It is an object of the present invention to provide a dual-frequency switching oscillator which can apply an optimum condition for each frequency band and facilitates design.
[0006]
[Patent Document 1] Japanese Patent Application No. 2001-163236 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-290153
[Means for Solving the Problems]
The present invention includes a first crystal oscillator and a second crystal oscillator each including an oscillation circuit including a crystal oscillator, and a first electronic switch and a second crystal switch between the first crystal oscillator and the second crystal oscillator and a power supply. An electronic switch is provided, and a third switch and a fourth switch are provided on the output side of the first crystal oscillator and the second crystal oscillator, and are commonly connected to form an output terminal, and the first switch, the third switch, and the The second switch and the fourth switch are configured such that ON / OFF operations are opposite to each other.
[0008]
Thus, when the first switch and the third switch are turned on, for example, the second switch and the fourth switch are turned off. Therefore, the first crystal oscillator operates and the second crystal oscillator stops. In addition, since the first crystal oscillator and the second crystal oscillator are electrically disconnected, there is no influence of the second crystal oscillator. Hereinafter, an embodiment of the present invention will be described.
[0009]
【Example】
FIG. 1 is a block diagram of a dual frequency switching oscillator for explaining an embodiment of the present invention. The same parts as those in the prior art are denoted by the same reference numerals, and description thereof will be simplified or omitted.
[0010]
The two-frequency switching oscillator includes a first crystal oscillator 6a and a second crystal oscillator 6b each including an oscillation circuit 3 (ab) including a crystal resonator 1 (ab). The first and second crystal oscillators 6 (ab) have first and second electronic switches 7 (ab) between a common power supply Vcc. In addition, the output terminal Vout is shared, and third and fourth switches 7 (cd) are provided between the output terminal Vout and the output terminal. Each electronic switch 7 (abcd) is composed of a MOS, a transistor, or the like.
[0011]
Then, the first and third switches 7 (ac) are connected to the selection terminal 9 via the inverter 8, and the second and fourth switches 7 (bd) are directly connected to the selection terminal 9. The selection terminal 9 is connected to a power supply Vcc via a resistor 11, and has a conductive line 10 that can be grounded between the power supply Vcc and the ground. The conduction line 10 has an open end in an initial state.
[0012]
In such a case, if the conductive line 10 is first set to the open end in the initial state, the following operation is performed. That is, a 1 signal is input to the second and fourth electronic switches 7 (bd) and a 0 signal is input to the first and third switches 7 (ac) by the inverter 8 according to the power supply voltage. Therefore, when each of the first to fourth electronic switches 7 (abcd) is turned on (conducted) by one signal and turned off (cut off) by zero signal, the second crystal oscillator 6b operates, and the first crystal oscillator 6a It will be stopped.
[0013]
Further, the fourth switch 7d is turned on to conduct to the output terminal Vout, the third switch 7c is turned off, and the output terminal Vout and the first and second crystal oscillators 6 (ab) are electrically cut off. Therefore, when the conduction line 10 is an open end, the second crystal oscillator 6b is selected to operate (oscillate). Then, the first and second crystal oscillators 6 (ab) are cut off by the third switch 7c.
[0014]
Next, assuming that the conductive line 10 is grounded, the following operation is performed. That is, since the power supply Vcc is grounded, a 0 signal is input to the second and fourth switches 7 (bd), and a 1 signal is input to the first and third switches 7 (ac) by the inverter 8. Therefore, in this case, contrary to the above, the first and third switches 7 (ac) are turned on, the first crystal oscillator 6a is operated to conduct to the output terminal Vout, and the second and fourth switches 7 (ac) are turned on. bd) is turned off to stop the second crystal oscillator 6b, and the output terminal Vout and the first and second crystal oscillators 6 (ab) are electrically disconnected.
[0015]
For this reason, in this embodiment, the second crystal oscillator 6b can be operated when the conductive line 10 is set to the open end, and the first crystal oscillator 6a can be operated when grounded to the ground. In short, the first and third switches 7 (ac) and the second and fourth switches 7 (bd) operate by selecting the first or second crystal oscillator 6 (ab) such that the ON / OFF operations are opposite to each other. I do.
[0016]
In either case, since the first and second crystal oscillators 6 (ab) are electrically cut off, the design is facilitated as independent oscillators. Then, it is possible to design the first and second crystal oscillators 6 (ab) under optimum conditions for each frequency band. If the third and fourth switches 7 (cd) are turned on while the second crystal oscillator 6 b is in operation, the first crystal oscillator 6 a acts as a load on the second crystal oscillator 6 b and exerts an influence. Make it difficult.
[0017]
[Other matters]
In the above embodiment, one of the first and second crystal oscillators 6 (ab) is selected, and the other is stopped by turning off the first or second switch 7 (ab) by a 0 signal or a 1 signal. It may be configured as shown in FIG. That is, the semiconductor fuse element 12 is inserted between the first and second switches 6 (ab) of the first and second crystal oscillators 7 (ab) and the power supply Vcc.
[0018]
For example, when the first crystal oscillator 6a is operated and the second crystal oscillator 6b is stopped, the first crystal oscillator 6a is stopped, the second crystal oscillator 6b is turned on, and an overcurrent is supplied from another power supply. Disconnect. Thereby, the second crystal oscillator 6b may be completely disabled to prevent the influence on the first crystal oscillator 6a.
[0019]
Further, the first to fourth switches 7 (abcd) are turned on by one signal and turned off by 0 signal, but may be turned on by 0 signal and turned off by 1 signal. And, needless to say, a voltage-controlled oscillator may be inserted by inserting a voltage variable capacitance element into the oscillation closed loop. Further, the frequency band is set to the 150 MHz band and the 600 MHz band, but the present invention is not limited to this, and any two different frequencies can be applied.
[0020]
【The invention's effect】
The present invention includes a first crystal oscillator and a second crystal oscillator each including an oscillation circuit including a crystal oscillator, and a first electronic switch and a second crystal switch between the first crystal oscillator and the second crystal oscillator and a power supply. An electronic switch is provided, and a third switch and a fourth switch are provided on the output side of the first crystal oscillator and the second crystal oscillator, and are commonly connected to form an output terminal, and the first switch, the third switch, and the The second switch and the fourth switch are configured such that ON / OFF operations are opposite to each other. Accordingly, it is an object of the present invention to provide a two-frequency switching oscillator that can apply an optimum condition for each frequency band and facilitates design.
[Brief description of the drawings]
FIG. 1 is a block diagram of a dual-frequency switching oscillator illustrating one embodiment of the present invention.
FIG. 2 is a block diagram of a dual-frequency switching oscillator illustrating another embodiment of the present invention.
FIG. 3 is a block diagram of a dual-frequency switching oscillator illustrating a conventional example.
FIG. 4 is a block diagram of a dual-frequency switching oscillator illustrating another example of the conventional example.
[Explanation of symbols]
Reference Signs List 1 crystal oscillator, 2, 7 electronic switch, 3 oscillation circuit, 4 voltage variable capacitance element, 5 high-frequency element resistance, 6 crystal oscillator, 8 inverter, 9 selection terminal, 10 conduction line, 11 resistance, 12 semiconductor fuse element.

Claims (1)

A first crystal oscillator and a second crystal oscillator each including an oscillation circuit including a crystal oscillator are provided, and a first electronic switch and a second electronic switch are provided between the first crystal oscillator, the second crystal oscillator, and a power supply. At the same time, a third switch and a fourth switch are provided on the output side of the first crystal oscillator and the second crystal oscillator and connected in common to form an output terminal, and the first switch, the third switch, the second switch, A two-frequency switching type crystal oscillator characterized in that ON / OFF operations of the fourth switch are opposite to those of the fourth switch.

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