JP4772617B2 - High frequency oscillator - Google Patents

Description

  The present invention relates to a high-frequency oscillator using a dielectric resonator. More specifically, the present invention relates to a high-frequency oscillator that can suppress unnecessary spurious oscillation that is half the original oscillation frequency.

  A high-frequency oscillator using a dielectric resonator has a microstrip line formed on the surface of a dielectric substrate having a ground conductor film formed on the back surface, and components such as a dielectric resonator, a transistor, and a resistor are mounted. An oscillation circuit is formed. For example, as shown in an equivalent circuit diagram in FIG. 3, the bipolar transistor 1 has a base B connected to the first microstrip line 3, a collector C connected to the second microstrip line 4, and an emitter E It is mounted on the dielectric substrate 5 so as to be grounded. The dielectric resonator 2 is mounted on the surface of the dielectric substrate 5 so as to be coupled to both the first and second microstrip lines 3 and 4. An output terminal Out is connected to the collector terminal C of the transistor 1 via an output load resistor 8 and a capacitive coupling unit 10, and a DC power supply is supplied to the base terminal B via a base bias resistor 6 and a collector bias resistor 7. Connected to terminal Vcc. Note that a connection portion between the base bias resistor 6 and the collector bias resistor 7 is connected to the collector terminal C so that power is also supplied to the collector terminal C. Further, an oscillation control capacitor 9 is connected between a connection portion between the collector bias resistor 7 and the DC power supply terminal Vcc and the ground (see, for example, Patent Document 1).

The first microstrip line 3 constitutes a feedback side circuit together with the dielectric resonator 2, and the second microstrip line 4 constitutes an oscillation side circuit together with the dielectric resonator 2. The first and second microstrip lines 3 and 4 are considered to be convenient for easy oscillation at a desired frequency by facilitating coupling with the dielectric resonator 2 and have the same length. In addition, the dielectric resonator 2 is formed so as to be substantially symmetrical.
Japanese Patent Laying-Open No. 2004-328131 (FIG. 3)

A conventional high frequency oscillator using a dielectric resonator as described above oscillates at a desired frequency f ₀ based on the resonance frequency of the dielectric resonator. However, for example, load resistance is obtained sufficient feedback amount is consistent even at half the frequency of the desired frequency f _0, the oscillation occurs at the frequency phase of the in phase f _0/2 of the feedback circuit, unwanted spurious There is a problem of being output as a mode. Therefore, it is necessary to remove the unnecessary spurious mode by connecting a filter in the high-frequency oscillator or an external circuit, and there is a problem that the number of parts increases and the cost is increased, and the apparatus is increased in size.

  The present invention has been made to solve such a problem, and provides a high-frequency oscillator using a dielectric resonator that does not generate a spurious signal having a frequency half that of a desired frequency. The purpose is to do.

As a result of intensive studies in order to obtain a high-frequency oscillator that does not generate a spurious frequency that is ½ of a desired oscillation frequency f ₀ , the present inventor has made a first micro-connection connected to the input side (base) of the transistor. By changing the impedance by making the length of the strip line shorter than the second microstrip line connected to the output side (collector or emitter) of the transistor, the dielectric resonator and the first microstrip line relative to oscillate by the feedback amount of the feedback side circuit including the desired frequency f ₀ in changed without sufficient feedback is obtained in the feedback is attenuated at half the frequency of the desired frequency f ₀ not lead to oscillation by the circuit is not formed, oscillates only at the desired frequency f _0, it does not generate unwanted spurious It was found that the frequency oscillator can be obtained.

A high-frequency oscillator according to the present invention includes a dielectric substrate, a transistor provided on the dielectric substrate, a first microstrip line connected to the input side of the transistor and provided on the dielectric substrate, and the transistor And a second microstrip line provided on the dielectric substrate, and a dielectric resonance provided on the dielectric substrate so as to be coupled to the first and second microstrip lines, respectively. The first microstrip line is shorter than the second microstrip line , oscillates at a desired oscillation frequency f ₀ based on the resonance frequency of the dielectric resonator , and the desired The length is such that it does not oscillate at a frequency half that of the oscillation frequency f ₀ .

According to the present invention, the first microstrip line connected to the input side (eg, base) of the transistor is formed shorter than the second microstrip line connected to the output side (eg, collector or emitter). Therefore, the impedance on the side of the feedback circuit configured with the dielectric resonator changes and becomes an impedance that provides a sufficient feedback amount at a desired frequency, but is sufficient for a frequency that is ½ of the desired frequency. A feedback amount cannot be obtained because a large amount of feedback cannot be obtained. For this reason, sufficient feedback is obtained for the oscillation frequency f ₀ which is the original desired frequency and oscillation occurs. However, no feedback circuit is configured for a frequency which is ½ of the desired frequency, and oscillation occurs. Not reached. As a result, oscillation occurs only at the output of the original desired frequency, and only power at the desired frequency is output.

As a result, without mounting a component such as a filter to the high-frequency oscillator in or external circuit, by merely adjusting the length of the first microstrip line, unnecessary, such as f _0/2 for a desired frequency f ₀ Spurious is suppressed and only the output of the necessary frequency is obtained. In addition, since the first microstrip line is shortened, a space is generated on the dielectric substrate, and the microstrip line of the varactor diode port can be provided at that portion, and the high frequency oscillator can be formed without increasing the dielectric substrate. It can also be a voltage controlled oscillator (VCO).

Next, the high frequency oscillator of the present invention will be described with reference to the drawings. In the high frequency oscillator according to the present invention, the first microstrip line constituting the feedback side circuit is connected to the input side of the transistor, and the second microstrip line constituting the oscillation side circuit is connected to the output side of the transistor. Dielectric resonators are provided so as to be coupled to the first and second microstrip lines, respectively. The first microstrip line is shorter than the second microstrip line , oscillates at a desired oscillation frequency f ₀ based on the resonance frequency of the dielectric resonator , and 1 of the desired oscillation frequency f ₀ . The length is such that it does not oscillate at a frequency of / 2 .

  Specifically, FIG. 1 shows an equivalent circuit diagram of the embodiment, and FIG. 2 shows a layout diagram thereof. A dielectric resonator 2 is provided so as to be coupled to each of the first and second microstrip lines 3 and 4, and the first microstrip line 3 is more than the second microstrip line 4. It is short. Here, the length of the first microstrip line 3 is short so that a feedback circuit is not configured with respect to a frequency that is ½ of a desired frequency.

  A configuration in which a feedback-type high-frequency oscillator is formed by the transistor 1, the dielectric resonator 2, the first microstrip line 3, the second microstrip line 4, and the dielectric substrate 5 on which the ground conductor film is formed on the back surface is conventionally used. In the same manner as the transistor 1, a GaAsFET can be used in addition to a bipolar transistor. The example shown in FIG. 1 is an example of an npn-type grounded bipolar transistor, but it may not be grounded. The pnp-type is the same except that the emitter and collector are reversed. The dielectric resonator 2 can be the same as the conventional one.

  The present invention is characterized in that the line length Lb of the first microstrip line 3 is shorter than the line length Lc of the second microstrip line 4. That is, as described above, the present inventor suppresses the spurious due to the oscillation at the half frequency of the resonance frequency of the dielectric resonator 2 by the feedback type high frequency oscillator using the dielectric resonator 2. Therefore, earnest examination was repeated. That is, for example, when the desired oscillation frequency is 10.75 GHz, the lengths of the first and second microstrip lines 3 and 4 are both set to Lc = 4.7 mm, and the first microstrip line constituting the feedback circuit is formed. Only 3 was scraped from the tip (opposite side of the base terminal side) by about 0.2 to 0.3 mm and gradually shortened, and the occurrence of unnecessary spurious at 5.375 GHz which was a 1/2 frequency was examined. .

As a result, when the line length Lb of the first microstrip line 3 is 4.1 mm, unnecessary spurious of 5.375 GHz is generated, but when the line length Lb is 1.4 to 1.9 mm, the desired frequency f ₀ is generated. become a -90dB or less with respect to the output, the occurrence of unwanted spurious of f _0/2 is almost gone.

As described above, by shortening the length of the first microstrip line 3, it is possible to suppress the oscillation of the f _0/2, it is possible to prevent the occurrence of spurious. On the other hand, it has been found that the output of the original desired frequency has almost no effect and can suppress only spurious.

  In FIG. 1, the output terminal Out is connected to the collector terminal C of the transistor 1 via the output load resistor 8 and the capacitive coupling unit 10, and the DC power supply terminal Vcc is connected to the collector terminal C via the collector bias resistor 7. Yes. A DC power supply terminal Vcc is connected to the base terminal B of the transistor 1 via a base bias resistor 6 and a collector bias resistor 7.

  FIG. 2A shows an example of a layout diagram in which the transistor 1 and the dielectric resonator 2 are mounted on the dielectric substrate 5 and the microstrip lines 3 and 4 are formed. In FIG. 2 (a), the same parts as those in FIG. Further, since the dielectric resonator 2 and the transistor 3 have a thickness, the top view, the bottom view, the left side view, and the right side view of FIG. 2A are respectively shown in FIGS. 2B to 2E. A rear view of (a) is shown in FIG. The size of the dielectric substrate 5 is, for example, an alumina substrate having a length × width of about 15 mm × 8 mm and a thickness of about 0.6 mm, and the ground conductor film provided on the back surface of the dielectric substrate 5 has a thickness of 3 The microstrip lines 3 and 4 are formed of a multilayer film of copper / nickel / gold with a thickness of about 4 μm, and the same multilayer film is formed with the same thickness as the ground conductor film and is patterned. A through hole for grounding is exposed on the back surface of the dielectric substrate 5. The resistors 6, 7, and 8 are chip resistors, and the capacitor 9 is a chip capacitor, both of which are square-shaped soldered.

  The present invention can be used for a communication device, a measuring device, a detector, a radar device, and the like using a high frequency such as a microwave and a millimeter wave, such as a satellite broadcast receiving converter, a distance measuring device, and a Doppler sensor.

1 is an equivalent circuit diagram showing an embodiment of a high-frequency oscillator according to the present invention. It is a figure which shows the layout figure of the high frequency oscillator shown by FIG. It is an equivalent circuit diagram which shows an example of the conventional high frequency oscillator.

Explanation of symbols

1 Transistor 2 Dielectric Resonator 3 First Microstrip Line 4 Second Microstrip Line 5 Dielectric Substrate 6 Base Bias Resistor 7 Collector Bias Resistor 8 Output Load Resistor 9 Oscillation Control Capacitor

Claims (1)

A dielectric substrate, a transistor provided on the dielectric substrate, connected to an input side of the transistor, a first microstrip line provided on the dielectric substrate, and connected to an output side of the transistor; A second microstrip line provided on the dielectric substrate, and a dielectric resonator provided on the dielectric substrate so as to be coupled to each of the first and second microstrip lines, The first microstrip line is shorter than the second microstrip line , oscillates at a desired oscillation frequency f ₀ based on the resonance frequency of the dielectric resonator , and 1 of the desired oscillation frequency f ₀ A high frequency oscillator having a length that does not oscillate at a frequency of / 2 .

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