JP2005167572A - Frequency switching type high-frequency oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frequency switching type high-frequency oscillator capable of sufficiently reducing spurious noise from an oscillation circuit and selecting a frequency only in a desired high-frequency band, in a frequency selection type oscillator that selects a harmonic component from a plurality of crystal oscillators having different fundamental wave frequencies and changes one of the high frequencies for outputting. <P>SOLUTION: When a desired frequency band is selected from a frequency signal from the oscillation circuits 10a, 10b for generating different high frequencies, function sections corresponding to two bands to be passed, respectively, are accommodated in one package as a selection element used for selection elements 20a, 20b. The two selection elements are used for establishing a two-stage connection of the same selection band, thus achieving a frequency switching high-frequency oscillator of which the spurious noise is sufficiently reduced and frequency quality is superior. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a frequency-switchable high-frequency oscillator, and more particularly to a frequency-selective oscillator that selects harmonic components from a plurality of crystal oscillators having different fundamental wave frequencies and switches and outputs one of the high-frequency frequencies. It is about.

Conventionally, each of the oscillation frequencies from two oscillating circuits that oscillate at different frequencies is band-selected by passing through a selection element, and one of the frequencies after the band selection is switched by a changeover switch to change the frequency from a single output terminal. There is a frequency-switching type high-frequency oscillator (also called a selectable OSC) that is designed to output.
For example, when a frequency switching type high frequency oscillator is used as a clock supply source for a communication device or the like that handles a plurality of carrier frequencies, a voltage controlled crystal oscillator (VCXO: Voltage Controlled) that generally uses a highly stable crystal resonator as its vibration source. Often, the structure is a Crystal Oscillator. Here, when the frequency to be obtained from the frequency-switching type high-frequency oscillator exceeds 600 MHz, the fundamental wave of the crystal resonator is multiplied, and only a desired multiplied wave component is selected by a filter and then amplified. A high frequency is output by obtaining a target frequency or intentionally distorting the output of the crystal oscillation circuit to increase a harmonic component and selecting a desired harmonic component by a filter.

FIG. 4 is a block diagram showing a configuration example of a conventional frequency switching type high-frequency oscillator used in an optical communication device.
For simplification of description, description of the voltage control portion as VCXO is omitted below.
The frequency-switching type high-frequency oscillator 100 shown in this figure includes an oscillation circuit 10a that generates a predetermined frequency, a selection element 120a that selects a predetermined frequency band component from an output generated by the oscillation circuit 10a, and the oscillation circuit 1. An oscillation circuit 10b that generates a different predetermined frequency, a selection element 120b that selects a predetermined frequency band component from an output generated by the oscillation circuit 10b, and a power supply voltage to be supplied to either the oscillation circuit 10a or the oscillation circuit 10b. A first changeover switch (switch SW) 30 for selectively switching whether to give, and an output signal of the selection element 120a and an output signal of the selection element 120a as inputs, and a second changeover switch (selective changeover) Switch SW) 40 and a broadband amplifier 50 that amplifies the signal from the second switch 40 and outputs the amplified signal from the frequency output terminal. Eteiru. The first changeover switch 30 and the second changeover switch 40 are supplied with a changeover control signal from a changeover SW control terminal.
The oscillation circuit 10a uses a crystal resonator having a fundamental wave of 155 MHz and multiplies this fundamental frequency by 4 to generate 622 MHz (frequency f _A ), and the oscillation circuit 10b has a fundamental wave of 166 MHz. Using a crystal oscillator, this basic frequency is multiplied by 4 to generate 666 MHz (frequency _B ).
The selection element 120a is a surface acoustic wave (SAW) filter and selects a frequency component (band) with the 622 MHz band as a pass band, and the selection element 120b is a surface acoustic wave (SAW) filter and is a 666 MHz. A frequency component (band) is selected using the band as a pass band.

The frequency switching type high-frequency oscillator shown in this example functions as follows. That is, when the power supply voltage from the power supply terminal is supplied to either the oscillation circuit 10a or the oscillation circuit 10b by the first changeover switch 30, the supplied oscillation circuit starts operation. Here, for example, a case where a switching control signal is given to the switching SW control terminal so as to select the frequency f _A side (622 MHz) will be described. Since the first changeover switch 30 supplies the power supply voltage to the oscillation circuit 10a, the oscillation circuit 10a oscillates and outputs 622 MHz. Next, the selection element 120a blocks the unnecessary radiation wave other than 622 MHz from the output of the oscillation circuit 10a, and selects the frequency band by passing only the frequency component of 622 MHz. The signal output from the selection element 120a is given to the second changeover switch 40. Since the second changeover switch 40 operates so as to select the output side of the selection element 120a, the signal output from the selection element 120a is supplied to the wideband amplifier 50, and is amplified by the wideband amplifier 50 to be output from the frequency output terminal. A frequency signal of 622 MHz is output.
At this time, since the power supply voltage is not supplied to the oscillation circuit 10b, the oscillation circuit 10b does not operate.

On the other hand, when the switching control signal is given to the switching SW control terminal so as to select the frequency f _B side (666 MHz), the first switching switch 30 and the second switching switch 40 are on the opposite side to the above. The oscillation circuit 10b operates. Therefore, the signal output from the selection element 120b is supplied to the broadband amplifier 50, and is amplified by the broadband amplifier 50 to output a frequency signal of 666 MHz from the frequency output terminal.

The configuration of the selection elements 120a and 120b used in the above-described conventional frequency switching type high-frequency oscillator 100 will be described with reference to the drawings.
FIG. 5 is a diagram showing a configuration example of the selection element used in FIG.
The selection element shown in this figure corresponds to the selection element 120a and the selection element 120b described above, and shows a configuration in each element package. That is, the selection element 120a includes an electrode part Pa1 and an electrode part Pa2 each including an IDT (Interdigital Transducer) electrode, and the electrode parts Pa1 and Pa2 have a transversal SAW filter whose pass band is a 622 MHz band. Function as. On the other hand, the selection element 120b similarly includes an electrode part Pb1 and an electrode part Pb2, and the electrode parts Pa1 and Pa2 function as a transversal SAW filter whose pass band is a 666 MHz band.

  Although the frequency switching type high-frequency oscillator 100 is configured by the selection element as described above, in recent years, the configuration of the selection element itself has changed, and miniaturization has progressed. For example, as shown in Japanese Patent Application Laid-Open No. 2000-224000, there is a product in which two filtering function units are stored in one selection element package. The configuration disclosed in this publication is also called a dual-in-package SAW filter.

FIG. 6 is a diagram showing a configuration example of a selection element when a dual-in-package SAW filter is applied as a selection element to the conventional frequency switching type high frequency oscillator shown in FIG.
The selection element 20 shown in this figure has two filtering function units in one package, and one of the function units is a SAW filter having a pass band in the 622 MHz band constituted by the electrode unit Pa1 and the electrode unit Pa2. The other is a SAW filter having a pass band in the 666 MHz band constituted by the electrode part Pb1 and the electrode part Pb2.
That is, if a dual-in-package SAW filter is used as the selection element, the frequency switching type high-frequency oscillator can be reduced in size. As an example of the frequency-switching type high-frequency oscillator which is miniaturized in this way, there is one proposed in Japanese Patent Laid-Open No. 2002-335127.

FIG. 7 is a diagram showing a configuration example of a selection element corresponding to Japanese Patent Laid-Open No. 2002-335127 (FIG. 2), and FIG. 8 is a frequency switching type high frequency when the configuration of the selection element shown in FIG. 7 is applied. It is a block diagram which shows the example of an oscillator. Note that the same functional parts as those shown in FIGS. 4 and 6 are given the same reference numerals, and descriptions thereof are omitted.
As shown in the example of FIG. 7, if an unbalanced circuit is configured using the selection element 20 formed of a dual-in-package SAW filter, the output sides of the two filtering function units, that is, the electrode units Pa2 and Pb2 are coupled. Therefore, the output can be connected to the broadband amplifier 50 in the subsequent stage. That is, as shown in the frequency-switching high-frequency oscillator 200 of FIG. 8, a frequency-switching high-frequency oscillator that outputs by switching between 622 MHz and 666 MHz from the frequency output terminal without obtaining the second switch 40 is obtained. Can do.
JP 2000-224000 A JP 2002-335127 A

However, in the conventional frequency switching type high frequency oscillator described above, unnecessary radiation from the oscillation circuit cannot be sufficiently reduced, and it may be difficult to select a frequency only in a desired high frequency band.
When the unnecessary radiation from the oscillation circuit cannot be sufficiently reduced, the frequency output from the frequency switching type high frequency oscillator includes a lot of noise components, and there is a problem that the frequency quality is deteriorated.

  In order to solve the above-mentioned problems, the invention according to claim 1 of the frequency-switching type high-frequency oscillator according to the present invention selects the band of the oscillation frequency from two oscillation circuits that oscillate different frequencies by passing through the selection element. In the frequency switching type high-frequency oscillator in which any one of the frequencies after the band selection is switched by a changeover switch and the frequency is output from a single output terminal, the selection element corresponds to each of the two bands to be passed. The functional unit is housed in one package, and two selection elements are used to form a two-stage connection of the same selection band.

  According to a second aspect of the frequency-switching type high-frequency oscillator of the present invention, in the frequency-switching type high-frequency oscillator according to the first aspect, the selection element has two bands to be passed on one piezoelectric substrate. Two types of surface acoustic wave filters corresponding to each of the filters are configured and accommodated in one package.

  According to a third aspect of the frequency-switching high-frequency oscillator of the present invention, in the frequency-switching high-frequency oscillator according to the second aspect, the surface acoustic wave filter is a transversal type. And

  According to a fourth aspect of the frequency-switching high-frequency oscillator of the present invention, in the frequency-switching high-frequency oscillator according to any one of the first to third aspects, each of the two frequencies to be switched and output exceeds 600 MHz. It is a value.

  When the frequency switching type high frequency oscillator of the present invention uses two selection elements to make a two-stage connection of the same selection band, the selection element has a function unit corresponding to each of the two bands to be passed in one package. Since it is configured using the elements contained in it, it can be configured with two identical selection elements without increasing the types of selection elements, and it can sufficiently reduce unnecessary radiation from the oscillation circuit, and only in the desired high frequency band. Therefore, there is an advantage that it is possible to realize a frequency-switching type high-frequency oscillator excellent in frequency quality without causing complication of the circuit.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
FIG. 1 is a functional block diagram showing an embodiment of a frequency switching type high frequency oscillator according to the present invention. Note that functional blocks similar to those shown in FIG. 4 described above are denoted by the same reference numerals, and description thereof is omitted.
That is, the frequency-switching type high-frequency oscillator 1 shown in this figure is configured by using the selection elements 20a and 20b, and is a connection for giving one of the outputs of the selection elements to one input of the other selection element. ing.

The selection elements 20a and 20b are the same as those shown in FIG. 4 described above, and are selection elements composed of dual-in-package SAW filters in which two filtering function units are stored in one selection element package. is there.
Here, the connection relationship between the selection elements 20a and 20b will be specifically described with reference to the drawings.

FIG. 2 is a diagram showing an example of the configuration and connection of the selection element used in the frequency-switching type high-frequency oscillator according to the present invention.
As shown in this figure, the selection elements 20a and 20b have the same configuration and have an input / output corresponding to 622 MHz and an input / output corresponding to 666 MHz in one package.
The selection element 20a is connected so as to input the frequency signal including 622 MHz output from the oscillation circuit 10a to the electrode portion Pa1, and the frequency-selected (first filtered) 622 MHz frequency signal is output from the electrode portion Pa2. Is done. The frequency signal output from the electrode section Pa2 side is connected to be input to the electrode section Pa1 side of the other selection element 20b, and the frequency signal of 622 MHz that has been further frequency-selected (second filtering) is connected to the selection element 20b. It is output from the electrode part Pa2 side, and this is connected to one input of the changeover switch 40.
The selection element 20b is connected so as to input the frequency signal including 666 MHz output from the oscillation circuit 10b to the electrode part Pb1 side, and the frequency signal of the frequency selection (first filtering) 666 MHz is output from the electrode part Pa2 side. Is done. The frequency signal output from the electrode part Pb2 side is connected so as to be input to the electrode part Pb1 side of the other selection element 20a, and the frequency signal of 666 MHz subjected to frequency selection (second filtering) is supplied to the selection element 20a. It is output from the electrode part Pb2 side, and this is connected to the other input of the changeover switch 40.

In this way, since the two frequency signals of 622 MHz and 666 MHz, which are the required frequencies, are frequency-selected through two stages of filtering, unnecessary radiation is further reduced. As a result, although the level of the required frequency band is lowered due to the insertion loss for two stages, the frequencies other than the respective required frequency bands (noise components due to unnecessary radiation) are sufficiently reduced. Will improve.
Further, since the frequency switching type high-frequency oscillator 1 using such a configuration of the selection element uses a selection element composed of a dual-in-package SAW filter, the conventional frequency switching type high-frequency oscillator 100 shown in FIG. Compared to the above, the area required for mounting the selection element is hardly increased, and the selection element 20a and 20b are mounted at the time of component mounting because two types of selection elements are used. There is also an effect that no mistake occurs.

Further, in the above-described example, the case where the selection elements 20a and 20b are arranged to be cross-connected as shown in the drawing is shown, but the frequency switching type high-frequency oscillator of the present invention is not limited to this, As shown in FIG. 3, the selection elements 20a and 20b may be connected straight.
FIG. 3 is a diagram showing another example of the configuration and connection of the selection element used in the frequency-switching type high-frequency oscillator according to the present invention.
Even in this example, the selection elements 20a and 20b have exactly the same configuration as shown in FIG. 2 described above, and input / output corresponding to 622 MHz and input / output corresponding to 666 MHz. In a single package.
The selection element 20a is connected so as to input the frequency signal including 622 MHz output from the oscillation circuit 10a to the electrode part Pa1, and on the other hand, the frequency signal including 666 MHz output from the oscillation circuit 10b is input to the electrode part Pb1. Connect to do.
Then, frequency signals of 622 MHz and 666 MHz, which are respectively frequency-selected (first filtering), are output from the electrode portions Pa2 and Pb2.
The selection element 20b is connected to input the 622 MHz frequency signal output from the electrode part Pa2 of the selection element 20a to the electrode part Pa1, and on the other hand, the frequency of 666 MHz output from the electrode part Pb2 of the selection element 20a. It connects so that a signal may be input into the electrode part Pb1 side.
Then, frequency signals of 622 MHz and 666 MHz that have been frequency-selected (second filtering) are output from the electrode portions Pa2 and Pb2 side of the selection element 20b, and these are connected to two inputs of the changeover switch 40, respectively.

  Even with this configuration, the two frequency signals of 622 MHz and 666 MHz, which are the required frequencies, are frequency-selected through two stages of filtering, so unnecessary radiation is further reduced and frequency switching with excellent frequency quality is achieved. Type high-frequency oscillator can be obtained.

As described above, the frequency-switching type high-frequency oscillator according to the present invention uses the selection elements 20a and 20b in selecting a desired frequency band from the frequency signals from the oscillation circuits 10a and 10b that generate different high-frequency frequencies. As a selection element to be used, a function unit corresponding to each of two bands to be passed is accommodated in one package, and two selection elements are used to form a two-stage connection of the same selection band. Therefore, it is possible to realize a frequency-switching type high-frequency oscillator with high frequency quality in which unnecessary radiation is sufficiently reduced.
In the above embodiment, the transversal SAW filter has been shown and described. However, other SAW filters such as a multimode filter may be used as necessary.

It is a functional block diagram showing an embodiment of a frequency switching type high frequency oscillator according to the present invention. It is a figure which shows the example of a structure and connection of the selection element used for the frequency switching type | mold high frequency oscillator which concerns on this invention. It is a figure which shows the example of a structure of the selection element used for the frequency switching type | mold high frequency oscillator which concerns on this invention, and another connection. It is a functional block diagram which shows the structural example of the conventional frequency switching type | mold high frequency oscillator. It is a figure which shows the structural example of the selection element used in FIG. It is a figure which shows the structural example of the selection element at the time of applying a dual in package SAW filter as a selection element to the conventional frequency switching type | mold high frequency oscillator shown in FIG. It is a figure which shows the structural example of the selection element shown by the prior literature. FIG. 8 is a block diagram illustrating an example of a frequency switching type high-frequency oscillator when the configuration of the selection element illustrated in FIG. 7 is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Frequency switching type high frequency oscillator 10a ... Oscillation circuit (622MHz)
10b: Oscillator circuit (666 MHz)
20, 20a, 20b ... selection element (dual-in-package type)
30 ... 1st changeover switch 40 ... 2nd changeover switch 50 ... Broadband amplifier 100 ... Frequency change type high frequency oscillator 120a, 120b ... Selection element 200 ... Frequency change type high frequency oscillator Pa1, Pa2, Pb1, Pb2 ... Electrode part

Claims (4)

Oscillation frequencies from two oscillating circuits that oscillate at different frequencies are each band-selected by passing through a selection element, and one of the frequencies after band selection is switched by a changeover switch, and the frequency is output from a single output terminal. In such a frequency switching type high frequency oscillator,
The selection element is one in which a functional unit corresponding to each of the two bands to be passed is accommodated in one package.
A frequency-switching type high-frequency oscillator characterized by using two selection elements to form a two-stage connection of the same selection band.   The selection element comprises two types of surface acoustic wave filters corresponding to two bands to be passed on one piezoelectric substrate, and accommodates them in one package. The frequency-switching type high-frequency oscillator according to claim 1.   3. The frequency-switching type high-frequency oscillator according to claim 2, wherein the surface acoustic wave filter is a transversal type. 4. The frequency-switching type high-frequency oscillator according to claim 1, wherein the two frequencies to be switched and output are both values exceeding 600 MHz.

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