JP2008141291A - Microwave filter and high frequency oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave filter of low loss and high Q value in high frequency band and a high frequency oscillator of high Q value with a simple structure. <P>SOLUTION: In the microwave filter and the high frequency oscillator, an oscillator 2 and a band pass filter 3 are provided on an identical crystal substrate 1 high in Q value. A high order overtone of the oscillator 2 is used to form the length of an overlapped part of a microstrip line 4 of the band pass filter 3 to be connected to an output terminal of the oscillator 2 so that it becomes an electric length of λg/4 of a desired pass frequency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microwave filter and a high-frequency vibrator using a crystal resonator, and more particularly to a microwave filter and a high-frequency vibrator realizing a low loss and a high Q value.

  Conventionally, many microwave band filters have been put to practical use, such as those using waveguides, those using transmission lines, and those using multilayer ceramics.

Conventionally, there has been an overtone oscillation circuit that uses an odd-order harmonic component (3f0, 5f0; so-called overtone frequency) of the fundamental frequency (f0) instead of the fundamental frequency of the vibrator.
Further, when the Q value is high, sharp resonance characteristics and filter characteristics are obtained, and the crystal has a high Q value.

  As prior art of the microwave filter, Japanese Patent Application Laid-Open No. 05-007125 (Patent Document 1), Japanese Patent Application Laid-Open No. 06-334468 (Patent Document 2), Japanese Patent Application Laid-Open No. 2002-077684 (Patent Document 3), There is 2001-308680 (patent document 4).

Patent Document 1 describes a structure in which a bandpass filter such as a highpass / lowpass is formed on a substrate of a piezoelectric resonator in a surface wave filter.
Patent Document 2 describes a structure in which a part of a matching circuit such as a microstrip line is formed on a substrate of a piezoelectric resonator in a surface acoustic wave device.
Patent Document 3 describes a structure in which a bandpass filter is formed on a substrate of a piezoelectric resonator in a surface wave filter.
Patent Document 4 describes a structure having a band-pass characteristic by forming a dual mode filter on the same substrate as a crystal resonator and connecting capacitors in parallel in a piezoelectric filter.

Further, as a prior art of the overtone oscillation circuit, there is JP-A-2002-232234 (Patent Document 5).
In Patent Document 5, in a crystal resonator composed of a quartz piece having a thickness-shear vibration state in which the vibration frequency is inversely proportional to the thickness, a first vibration region and a second vibration region having different thicknesses are provided, one of which serves as an oscillator, and the other Is a resonator that forms a filter, and operates as a first vibration region wave overtone vibration, and the second vibration region is described as a composite vibrator that operates as a fundamental wave vibration.

JP 05-007125 A Japanese Patent Laid-Open No. 06-334468 JP 2002-0776840 A JP 2001-308680 A JP 2002-232234 A

  However, the conventional filters shown in Patent Documents 1 to 4 are intended for a several hundred MHz band, and it is impossible to obtain a filter that realizes a low loss and a high Q value in a high frequency band of 1 GHz or higher. There was a problem.

  Further, the conventional oscillator circuit shown in Patent Document 5 describes a configuration that facilitates frequency adjustment in a high frequency band using an overtone resonator and an overtone resonator, but the configuration is complicated. There is a problem that the manufacturing process is complicated.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a microwave filter and a high-frequency vibrator having a simple configuration and a low loss and a high Q value in a high frequency band.

  The present invention for solving the problems of the above-described conventional example is a microwave filter having a vibrator and a band-pass filter, the vibrator having a signal input terminal formed on one surface of a quartz substrate. An output terminal formed on the other surface of the quartz substrate so as to face the input terminal, and the bandpass filter is connected to the output terminal and arranged in parallel, and the plurality of microstrip lines. A ground plane formed on one surface of the quartz substrate facing the stripline, the vibrator is a vibrator having a fundamental frequency component and an odd-order harmonic component, and a bandpass filter A band-pass filter that passes any one of the odd harmonic components as a pass frequency and suppresses the fundamental frequency component and other unnecessary harmonic components. It is.

  The present invention is also characterized in that, in the microwave filter, the electrical length of the overlapping portion between adjacent microstrip lines is a quarter wavelength of the desired pass frequency.

  According to the present invention, a microwave oscillation circuit includes any one of the microwave filters described above.

  The present invention also provides a high-frequency vibrator having a vibrator and a bandpass filter, the vibrator including a signal input terminal formed on one surface of the quartz substrate and the other surface of the quartz substrate. The band-pass filter includes a plurality of microstrip lines connected to the output terminal and arranged in parallel, and a quartz substrate facing the plurality of microstrip lines. A ground plane formed on one surface, the vibrator is a vibrator having a fundamental frequency component and an odd-order harmonic component, and the band-pass filter is an odd-order harmonic component, The present invention is characterized in that it is a band-pass filter that allows any one of the harmonic components to pass as a passing frequency and suppresses the fundamental frequency component and other unnecessary harmonic components.

  The present invention is also characterized in that, in the high-frequency vibrator described above, the electrical length of the overlapping portion between adjacent microstrip lines is a quarter wavelength of a desired passing frequency.

  In addition, the present invention is characterized in that a microwave oscillation circuit includes the high-frequency vibrator described above.

  According to the present invention, in the microwave filter, the vibrator and the bandpass filter are provided on the same crystal substrate, and the vibrator has a fundamental frequency component and an odd-order harmonic component (overtone). A microstrip type band in which the bandpass filter passes one of the odd-order harmonic components as a pass frequency and suppresses the fundamental frequency component and other unnecessary harmonic components. Because it is a microwave filter that is a pass filter, it is possible to perform metal pattern formation all at once, simplifying the manufacturing process, suppressing loss, and for high frequency bands with high Q values There is an effect that the filter can be realized.

  In addition, according to the present invention, since the electrical length of the overlapping portion between the adjacent microstrip lines is a microwave filter having a length of a quarter wavelength of the desired passing frequency, the adjacent microstrip lines are adjacent to each other. By changing the length of the overlapping portion, it is possible to provide a filter that passes a desired pass frequency.

  According to the present invention, it is possible to realize a microwave oscillator having excellent phase noise characteristics by configuring a microwave oscillator including the microwave filter having the above-described configuration.

  According to the present invention, in the high frequency vibrator, the vibrator and the band pass filter are provided on the same crystal substrate, and the vibrator has a fundamental frequency component and an odd-order harmonic component (overtone). Microstrip type that is a vibrator and the band-pass filter passes one of the odd harmonic components as a passing frequency and suppresses the fundamental frequency component and other unnecessary harmonic components. Since the high-frequency vibrator is a band-pass filter, the metal pattern can be formed all at once so that the manufacturing process can be simplified, the loss can be suppressed, and the high-frequency vibration with high Q value There is an effect that a child can be realized.

Embodiments of the present invention will be described with reference to the drawings.
The microwave filter according to the embodiment of the present invention is a microwave filter that uses a quartz substrate having a high Q value to improve filter characteristics, and is a combination of a high-frequency crystal resonator and a simple microwave bandpass filter. Yes, the crystal unit uses harmonic components, the bandpass filter is formed by a microstrip filter, and the crystal unit and the bandpass filter are collectively formed on the same crystal substrate. A microwave filter having a low loss and a high Q value is realized with the configuration.

  The high-frequency vibrator according to the embodiment of the present invention includes a crystal resonator and a band-pass filter, the crystal resonator uses a harmonic component, the band-pass filter is formed of a microstrip filter, A transducer and a bandpass filter are formed on the same quartz substrate at the same time. By using a high-frequency transducer with a simple configuration, a microwave oscillation circuit with excellent phase noise characteristics can be realized. is there.

FIG. 1A is a plan view showing a configuration of a microwave filter (the present filter) according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. .
As shown in FIG. 1A, the microwave filter according to the embodiment of the present invention has a configuration in which a vibrator 2 and a bandpass filter 3 are formed on a quartz substrate 1. Further, as shown in (b), the ground plane 5 and the metal wiring of the input electrode 6 are provided on the bottom surface of the crystal substrate 1.

  The vibrator 2 is a vibrator formed in a concave portion provided on the quartz substrate 1. The input electrode 6 on the bottom surface of the substrate serves as an input terminal, and the electrode in the concave portion on the top surface of the substrate serves as an output terminal. The vibrator 2 is configured by sandwiching a crystal substrate between electrodes.

In addition to the fundamental frequency f0, the vibrator 2 outputs the third harmonic 3f0 and the fifth harmonic 5f0 as harmonic components.
Here, for example, if the vibrator 2 is a vibrator having a fundamental frequency of 0.8 GHz, 800 MHz, 2.4 GHz, and 4 GHz are also output together.

  That is, when the vibrator 2 is used as a 2.4 GHz filter, the frequencies of 0.8 GHz and 4 GHz are also passed. Therefore, this filter is provided with a bandpass filter 3 that removes unnecessary signals of 0.8 GHz and 4 GHz.

  The band-pass filter 3 is a filter comprising a plurality of microstrip lines 4 having signal lines arranged in parallel at regular intervals on the same quartz crystal substrate as the vibrator 2 and a ground surface 5 provided on the bottom surface of the substrate. It is.

In particular, in this filter, as shown in FIG. 1A, the output terminal of the crystal resonator 2 and the microstrip line are connected to each other and formed with a common metal pattern.
Furthermore, in this filter, when the wavelength of a desired frequency is λg (electric length), the length of the overlapping portion (overlapping portion) between adjacent microstrip lines 4 arranged in parallel to each other is λg / 4 is formed. In this filter, the electrical length of the overlapping portion of the microstrip line 4 is λg / 4 with respect to 2.4 GHz. As a result, the bandpass filter 3 passes a 2.4 GHz band signal.

  The electrical length of the overlap portion of the microstrip line 4 is set to a quarter wavelength (λg / 4) of a desired frequency. When a signal in the 4 GHz band is desired to pass, the quarter wavelength (λg / 4).

  In this way, in the present filter, a high-performance high-frequency band with a simple configuration is formed by combining the vibrator 2 and the band-pass filter 3 formed of a microstrip filter on the same crystal substrate 1. The filter for is realized.

Thereby, for example, on the surface of the quartz substrate 1, the electrode pattern of the output terminal of the vibrator 2 and the microstrip line 4 of the bandpass filter 3 can be integrally formed by a common vapor deposition and patterning process. Similarly, since the ground surface 5 and the input electrode 6 can be integrally formed on the back surface of the quartz substrate 1, the manufacturing process can be simplified.
Furthermore, by using a common substrate, consistency between circuits can be improved and power loss can be reduced.

The operation of the microwave filter having the above configuration will be described.
1A, when 4 GHz that is a necessary wave and a high frequency that is an unnecessary wave are input from the upper left, 0.8 GHz of the fundamental wave frequency that is the resonance frequency of the vibrator 2, 2.4 GHz and 5 times of the third harmonic. The harmonic 4 GHz signal passes through the vibrator 2. Other frequencies are suppressed.

Signals of 0.8 GHz, 2.4 GHz, and 4 GHz are input to the band pass filter 3. Since the length of the overlap portion of the microstrip line 4 is λg / 4 at 4 GHz, the overlap portions of the microstrip at 4 GHz are coupled by electromagnetic coupling and capacitive coupling, and only 4 GHz is extracted. ) The signal is output to the lower right, and the fundamental 0.8 GHz and 2.4 GHz signals are removed.
In this way, the apparatus operates.

Another configuration example of the filter circuit will be described with reference to FIG. FIG. 2 is a plan view showing another configuration example of the present filter.
In the microwave filter shown in FIG. 2, the individual components such as the vibrator 2 ′, the band-pass filter 3 ′, and the microwave strip line 4 ′ are the same as the components of the microwave filter shown in FIG. The filter shown in FIG. 2 is arranged symmetrically with respect to the side in the short direction of the filter shown in FIG.

  That is, in the microwave filter of FIG. 2, an input signal is input from the upper right, and a signal having a desired pass frequency is output to the lower left through the vibrator 2 ′ and the microstrip line 4 ′.

  Further, in the microwave filter shown in FIGS. 1 and 2, the microstrip line 4 is formed in a direction orthogonal to the transmission line connected from the vibrator 2, and is short with respect to the short side of the illustrated filter. A plurality of parallel strips are arranged in parallel, but a plurality of microstrip lines 4 may be arranged obliquely in parallel with the angle with the transmission line connected from the vibrator 2 being an angle other than 90 degrees.

Also, even if the input and output of the microwave filter shown in FIGS. 1 and 2 are reversed so that the bandpass filter and the vibrator are arranged in this order, the filter has the same characteristics. is there.
In this way, by preparing filters with the same function and various circuit arrangements, it is easy to incorporate them into various devices, and the application range can be expanded.

Here, the pass characteristics of this filter will be described with reference to FIG. FIG. 3 is an explanatory diagram showing the pass characteristics of this filter.
In FIG. 3, the pass characteristics of only the vibrator, the pass characteristics of only the band pass filter, and the pass characteristics of the present filter including the vibrator and the band pass filter are shown in comparison.
As shown in FIG. 3, in the case of only the vibrator, the fundamental frequency (f0), the third harmonic (3f0), and the fifth harmonic (5f0) all pass. In the case of only the bandpass filter, the pass characteristic is a gentle curve and does not have a sharp characteristic. By combining the transducer and bandpass filter, the 5th harmonic, which is the desired frequency, is selectively passed, and the filter characteristics are steep. The fundamental frequency (f0) and the 3rd harmonic (3f0) pass through. It is suppressed.

Further, the band-pass filter 3 can be used in shapes other than those shown in FIGS. FIGS. 4A and 4B are schematic explanatory views showing another configuration example of the band-pass filter 3. FIG. 4A is a hairpin type, and FIG. 4B is a spiral type.
The band-pass filter 3 can be constituted by a hairpin type microstrip line as shown in FIG. 4 (a) and a spiral type microstrip line as shown in FIG. 4 (b), each passing a desired frequency. What is necessary is just to pattern to the length and shape to make.

Furthermore, a microwave oscillation circuit can be configured using this filter. FIG. 5 is a configuration block diagram of a microwave oscillation circuit using this filter.
As shown in FIG. 5, the oscillation circuit using the microwave filter of the present embodiment includes a microwave filter that passes the fifth harmonic, an amplifier that amplifies the signal, and a phase shift circuit that performs phase conversion with delay. Is an oscillation circuit that outputs a fifth harmonic (5f0).

  According to the microwave filter according to the embodiment of the present invention, the vibrator 2 and the bandpass filter 3 are provided on the quartz substrate 1 having a high Q value, and the high-order overtone of the vibrator 2 is used to provide a band. Since the length of the overlap portion of the microstrip line 4 constituting the pass filter 3 is formed to be λg / 4 of a desired frequency, for example, the fifth-order overshoot of a vibrator having a fundamental resonance of 0.8 GHz By making the resonance of the 4 GHz tone and the length of the overlap portion of the microstrip line 4 be λg / 4 of the 4 GHz signal, it can function as a 4 GHz band-pass filter, with a simple configuration and a high frequency band. It is possible to realize a high-performance filter for use.

  Further, according to the present filter, the vibrator 2 and the band pass filter 3 are provided on the same crystal substrate 1, so that the output electrode of the vibrator 2 on the surface and the metal of the microstrip line 4 of the band pass filter 3 are provided. The pattern formation and the metal pattern formation of the ground surface 5 and the input electrode 6 on the back surface can be performed in a lump, and the manufacturing process can be simplified and the power loss can be reduced.

  Furthermore, according to the present filter, the circuit arrangement may be reversed, and the filter circuit can be used even when the input and the output are reversed, thereby flexibly responding to various mounting restrictions. It is possible to increase the number of applicable devices.

  Furthermore, the configuration of this filter can be used as it is in a microwave oscillation circuit, and there is an effect that it is possible to provide a microwave oscillation circuit having excellent phase noise characteristics.

As another embodiment of the present invention, an example in which the configuration shown in FIGS. 1, 2, and 4 is used as a high-frequency vibrator will be described. An oscillation circuit using such a high-frequency vibrator will be described with reference to FIG. FIG. 6 is a schematic circuit explanatory diagram illustrating an example of an oscillation circuit (the present oscillation circuit) using the high-frequency vibrator having the configuration illustrated in FIG. 1, FIG. 2, or 4.
As shown in FIG. 6, the oscillation circuit includes a high-frequency vibrator 10, CMOS inverters 11 and 12, capacitors C1 and C2, and resistors R1 and R2, and the configuration of the high-frequency vibrator 10 is as follows. The configuration shown in FIG. 1, FIG. 2, or FIG.

  In the oscillation circuit configured as described above, the resistor R2 is, for example, 1 MΩ, and the output frequency from the CMOS inverter 12 can be made variable by appropriately setting the values of the capacitor C1 and the resistor R1.

  The high-frequency vibrator according to another embodiment of the present invention has an effect of realizing an oscillation circuit having excellent phase noise characteristics with a simple configuration.

  The present invention is suitable for a microwave filter and a high-frequency vibrator that realize a low loss and a high Q value.

(A) is a top view which shows the structure of the microwave filter (this filter) which concerns on embodiment of this invention, (b) is AA 'sectional drawing of (a). It is a top view which shows another structural example of this filter. It is explanatory drawing which shows the passage characteristic of this filter. It is a schematic explanatory drawing which shows another structural example of the band pass filter 3, (a) is a hairpin type, (b) is a spiral type. It is a block diagram of the configuration of a microwave oscillation circuit using this filter. FIG. 5 is a schematic circuit explanatory diagram illustrating an example of an oscillation circuit (the present oscillation circuit) using a high-frequency vibrator having the configuration of FIG. 1, FIG. 2, or FIG. 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Quartz substrate, 2 ... Vibrator, 3 ... Band pass filter, 4 ... Microstrip line, 5 ... Ground plane, 6 ... Input electrode, 10 ... High frequency vibrator, 11, 12 ... CMOS inverter

Claims (6)

A microwave filter having a vibrator and a bandpass filter,
The vibrator includes a signal input terminal formed on one surface of the quartz substrate, and an output terminal formed on the other surface of the quartz substrate so as to face the input terminal,
The band-pass filter includes a plurality of microstrip lines connected to the output terminal and arranged in parallel, and a ground surface formed on one surface of the quartz substrate so as to face the plurality of microstrip lines. ,
The vibrator is a vibrator having a fundamental frequency component and an odd harmonic component,
The bandpass filter is a bandpass filter that passes any harmonic component of the odd-order harmonic components as a passing frequency and suppresses the fundamental frequency component and other unnecessary harmonic components. A microwave filter characterized by that.   2. The microwave filter according to claim 1, wherein an electrical length of an overlapping portion between adjacent microstrip lines is a quarter wavelength of a desired passing frequency.   A microwave oscillation circuit comprising the microwave filter according to claim 1. A high-frequency vibrator having a vibrator and a bandpass filter,
The vibrator includes a signal input terminal formed on one surface of the quartz substrate, and an output terminal formed on the other surface of the quartz substrate so as to face the input terminal,
The band-pass filter includes a plurality of microstrip lines connected to the output terminal and arranged in parallel, and a ground surface formed on one surface of the quartz substrate so as to face the plurality of microstrip lines. ,
The vibrator is a vibrator having a fundamental frequency component and an odd harmonic component,
The bandpass filter is a bandpass filter that passes any harmonic component of the odd-order harmonic components as a passing frequency and suppresses the fundamental frequency component and other unnecessary harmonic components. A high-frequency vibrator characterized by that.   5. The high-frequency vibrator according to claim 4, wherein an electrical length of an overlapping portion between adjacent microstrip lines is a length of a quarter wavelength of a desired passing frequency.   A microwave oscillation circuit comprising the high-frequency vibrator according to claim 4.

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