JP4391722B2 - Voltage controlled oscillator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage controlled oscillator used for a transceiver such as a radio communication system and a radar system in a microwave band and a millimeter wave band, and more particularly to a voltage controlled oscillator with reduced phase noise.
[0002]
[Prior art]
FIG. 12 is a circuit configuration diagram showing a conventional voltage controlled oscillator.
In FIG. 12, 1 is an oscillation output terminal of the voltage controlled oscillator, and 5 is a resonator constituting the main body of the voltage controlled oscillator.
[0003]
Reference numeral 2 denotes a variable voltage power source in the resonator 5 that generates a DC voltage, and constitutes an applied power source for the cathode of the variable capacitance diode 4 (described later).
Reference numeral 3 denotes an active element made of an oscillation FET (oscillation element), which has a negative resistance with respect to an applied voltage. Further, the output terminal of the active element 3 constitutes the oscillation output terminal 1.
[0004]
Reference numeral 4 denotes a variable capacitance diode in the resonator 5. The cathode is connected to the output terminal of the variable voltage power supply 2 and the anode is grounded.
As will be described later, the oscillation frequency output from the oscillation output terminal 1 is variably set according to the magnitude of the DC voltage applied from the variable voltage power supply 2 to the variable capacitance diode 4.
[0005]
Reference numeral 7 denotes a 90-degree inverter line, and reference numeral 8 denotes an open-end (or short-circuited) microstrip line connected to one end of the 90-degree inverter line 7. The microstrip line 8 has a half wavelength of a desired oscillation frequency, and constitutes a main (first) resonance circuit in the resonator 5.
[0006]
The 90-degree inverter line 7 constitutes a sub (second) resonance circuit in the resonator 5 together with the inductor 21 (described later) and the variable capacitance diode 4, and is connected in parallel to the microstrip line 8.
[0007]
Reference numeral 10 denotes a phase adjusting microstrip line inserted into the output terminal of the resonator 5, and the output terminal of the phase adjusting microstrip line 10 is connected to the input terminal of the active element 3.
[0008]
Reference numeral 21 denotes a lumped constant inductor (hereinafter simply referred to as “inductor”) having one end connected to the cathode of the variable capacitance diode 4, and the other end of the inductor 21 is connected to the 90-degree inverter line 7.
The variable capacitance diode 4, the inductor 21, and the 90-degree inverter line 7 connected in series constitute the above-described second resonance circuit.
[0009]
As shown in FIG. 12, the resonator 5 connected to the input side of the active element 3 includes a first resonance circuit (microstrip line 8) connected in parallel to each other and a second resonance circuit (90-degree inverter line). 7, an inductor 21, a variable capacitance diode 4), and a variable voltage power source 2 that applies a DC voltage to the cathode of the variable capacitance diode 4.
[0010]
Next, the operation of the conventional voltage controlled oscillator shown in FIG. 12 will be described with reference to FIGS.
FIG. 13 is an explanatory view showing reflection on both sides when a conventional voltage controlled oscillator is separated, FIG. 14 is an explanatory view showing frequency characteristics of reflection gain (amplitude) on the resonator 5 side by the conventional voltage controlled oscillator, and FIG. FIG. 16 is an explanatory diagram showing the frequency characteristics of the reflection gain (amplitude) on the active element 3 side of the conventional voltage controlled oscillator, FIG. 16 is an explanatory diagram showing the frequency characteristics of the loop gain of the conventional voltage controlled oscillator, and FIG. FIG. 18 is an explanatory diagram showing the frequency characteristics of the connection point phase of each resonance circuit by the conventional voltage controlled oscillator.
[0011]
In general, a voltage controlled oscillator creates a loop gain by connecting a resonator 5 to an active element 3 having a negative resistance as shown in FIG.
Further, the loop phase is superimposed in the same phase through the phase adjusting microstrip line 10 so that the power is amplified and the oscillation operation is performed.
[0012]
Further, generally, the variable capacitance diode 4 is connected to the inductor 21 in the resonator 5, and the oscillation frequency is variably set by the DC voltage applied from the variable voltage power supply 2 to the variable capacitance diode 4. .
[0013]
In FIG. 12, an oscillation operation is performed by connecting a microstrip line 8 (first resonance circuit) having an open end to the active element 3.
Further, by connecting a series resonance circuit composed of the variable capacitance diode 4, the inductor 21 and the 90-degree inverter line 7 (second resonance circuit) to the microstrip line 8, the entire resonator 5 operates as a parallel resonance circuit. Then, the operation as a voltage controlled oscillator is performed.
[0014]
At this time, as shown in FIG. 13, the voltage controlled oscillator shown in FIG. 12 is separated at the connection point between the microstrip line 10 for phase adjustment and the resonator 5, and the first reflection S11 on the resonator 5 side Considering the second reflection S22 on the microstrip line 10 side for phase adjustment.
[0015]
Here, as shown in FIG. 14, the first reflection S11 has an amplitude characteristic having a loss at a desired (target) oscillation frequency fo.
The second reflection S22 is designed to have a gain at the oscillation frequency fo as shown in FIG.
[0016]
The sum of the reflections S11 and S22 is the loop gain, and the loop gain has a gain at the oscillation frequency fo as shown in FIG.
[0017]
On the other hand, with respect to the loop phase, the oscillation condition is satisfied in that the superposition of the phases of the reflections S11 and S22 becomes 0 [deg] (that is, in-phase) as shown in FIG.
Therefore, the design is performed so that the oscillation frequency fo becomes 0 degrees by appropriately setting the line length of the microstrip line 10 for phase adjustment.
[0018]
At this time, the entire phase of the resonator 5 is superimposed on the phase of the first resonance circuit (see the broken line) and the phase of the second resonance circuit (see the one-dot chain line) as shown by the solid line in FIG. Is represented by
[0019]
The above configuration is described in, for example, a paper described in “Asia Pacific Microwave Conference” TU3A-1 held in 1998, “AV-band MMIC VCO with a Sub-Resonator Coupled by a 90-degree inverter”. .
[0020]
It is known that the phase noise characteristic in the voltage controlled oscillator as shown in FIG. 12 is better as the Q value of the resonator 5 is higher.
The Q value of the resonator 5 is expressed by the overall phase inclination of the resonator 5. This phase inclination is obtained by superimposing the phase inclinations at the resonance frequencies of the two resonance circuits 7 and 8 connected in parallel. It is.
[0021]
[Problems to be solved by the invention]
As described above, the conventional voltage controlled oscillator uses the first resonance circuit composed of the microstrip line 8 and the second resonance circuit composed of the 90-degree inverter line 7, the inductor 21, and the variable capacitance diode 4, and Since the frequency at which the reflection phase of each resonance circuit is 180 degrees at the connection point of the resonance circuit is made to coincide with the oscillation frequency fo, the Q value becomes lower than that of a dielectric resonator or the like, and phase noise characteristics. There was a problem of getting worse.
[0022]
The present invention has been made to solve the above-described problems. The setting conditions of the first and second resonance circuits in the resonator are changed, and each resonance circuit is connected at the connection point of each resonance circuit. By setting the frequency at which the reflection phase is 180 degrees to shift in the opposite direction from the oscillation frequency, a voltage controlled oscillator with improved phase noise characteristics can be obtained by increasing the Q value in the vicinity of the oscillation frequency. Objective.
[0023]
[Means for Solving the Problems]
A voltage controlled oscillator according to the present invention includes an oscillation output terminal that supplies a desired oscillation frequency, a resonator having first and second resonance circuits connected in parallel to each other, and a connection between the first and second resonance circuits A phase adjustment circuit connected to the point, and an oscillation element having a negative resistance inserted between the phase adjustment circuit and the oscillation output terminal, the second resonance circuit including a variable capacitance diode, and a variable capacitance A voltage controlled oscillator in which an oscillation frequency is variably set according to the magnitude of a DC voltage applied to a diode, wherein the first resonance circuit includes a first distributed constant line or a lumped constant inductor. The second resonance circuit includes a second circuit element including a second distributed constant line or a lumped constant inductor, and a variable capacitance diode connected in series to the second circuit element. The frequency at which the reflection phase of the second resonance circuit is 180 degrees at the connection point of the first and second resonance circuits is set to be higher than the oscillation frequency, and the first is the connection point of the first and second resonance circuits. The frequency at which the reflection phase of the resonance circuit becomes 180 degrees is set lower than the oscillation frequency so that the resonance frequency of the resonator matches the oscillation frequency.
[0024]
The voltage controlled oscillator according to the present invention includes an oscillation output terminal for supplying a desired oscillation frequency, a resonator having first and second resonance circuits connected in parallel to each other, and first and second resonance circuits. A phase adjustment circuit connected to the connection point of the oscillation circuit, and an oscillation element having a negative resistance inserted between the phase adjustment circuit and the oscillation output terminal, the second resonance circuit includes a variable capacitance diode, A voltage controlled oscillator in which an oscillation frequency is variably set according to the magnitude of a DC voltage applied to a variable capacitance diode, wherein the first resonance circuit includes a first distributed constant line or a lumped constant inductor. The second resonant circuit includes a second circuit element including a second distributed constant line or a lumped constant inductor, and a variable capacitance diode connected in series to the second circuit element. The frequency at which the reflection phase of the first resonance circuit is 180 degrees at the connection point of the first and second resonance circuits is set higher than the oscillation frequency, and the connection point between the first and second resonance circuits is The frequency at which the reflection phase of the second resonance circuit becomes 180 degrees is set lower than the oscillation frequency so that the resonance frequency of the resonator matches the oscillation frequency.
[0025]
The second resonant circuit of the voltage controlled oscillator according to the present invention includes a coupled line inserted between the connection point of the first and second resonant circuits and the second circuit element.
[0026]
The first resonance circuit of the voltage controlled oscillator according to the present invention includes a second variable capacitance diode connected in series to the first circuit element.
[0027]
In addition, the first and second distributed constant lines of the voltage controlled oscillator according to the present invention are constituted by first and second microstrip lines, respectively.
[0028]
The oscillation element of the voltage controlled oscillator according to the present invention is constituted by an active element made of a high mobility transistor or a bipolar transistor.
[0029]
The voltage controlled oscillator according to the present invention includes an N-1 harmonic reflection circuit inserted between an oscillation element and an oscillation output terminal, and outputs an N harmonic of the oscillation frequency from the oscillation output terminal. .
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.
[0031]
FIG. 1 is a circuit configuration diagram showing Embodiment 1 of the present invention. The same components as those described above (see FIG. 12) are denoted by the same reference numerals, or “A” after the reference numerals. Detailed description is omitted.
[0032]
In FIG. 1, a resonator 5A includes a microstrip line 6A in place of the 90-degree inverter line 7 and the inductor 21 described above.
The microstrip line 6A, together with the variable capacitance diode 4, constitutes a second resonance circuit in the resonator 5A.
[0033]
The frequency at which the reflection phase of the second resonance circuit is 180 degrees at the connection point of each resonance circuit in the resonator 5 is set to be higher than the desired oscillation frequency fo, and the reflection phase of the first resonance circuit is 180 degrees. The frequency to be increased is set lower than the oscillation frequency fo so that the resonance frequency of the resonator 5 matches the oscillation frequency fo.
Thereby, the Q value of the resonator 5 in the vicinity of the resonance frequency is set to a sufficiently high value.
[0034]
FIG. 2 is an explanatory diagram showing the reflection phase characteristic of the resonator 5A according to the first embodiment of the present invention, and shows the reflection phase characteristic of the resonator 5A at the connection point of the two resonance circuits.
In FIG. 2, a thin solid line 11A indicates the reflection phase characteristic of the first resonance circuit (microstrip line 8A), and a broken line 12A indicates the reflection phase characteristic of the second resonance circuit (variable capacitance diode 4 and microstrip line 6A). A thick solid line 13A indicates the reflection phase characteristic of the resonator 5A, and fo indicates a desired oscillation frequency.
[0035]
Next, the operation according to the first embodiment of the present invention shown in FIG. 1 will be described with reference to FIG.
Note that the frequency characteristics as shown in FIG. 2 can be set by adjusting the line lengths of the strip lines 6A and 8A.
[0036]
As indicated by a broken line 12A in FIG. 2, the first short circuit point (that is, the point at which the phase becomes 180 degrees) of the second resonance circuit (variable capacitance diode 4 and microstrip line 6A) is a desired oscillation frequency. The frequency f2A is set to be sufficiently higher than fo.
[0037]
Further, as shown by a thick solid line 13A in FIG. 2, the reflection phase characteristics of the resonator 5A in which the respective resonance circuits are connected in parallel resonate in parallel at a desired oscillation frequency fo (that is, the phase becomes 0 degree). Thus, the first short-circuit point of the microstrip line 8A (first resonance circuit) is set to a frequency f1A lower than the desired oscillation frequency fo.
[0038]
Here, since the frequency f2A changes by changing the DC voltage from the variable voltage power supply 2 and changing the capacitance of the variable capacitance diode 4, the oscillation frequency fo can be changed accordingly.
[0039]
The reflection phase characteristic of the resonator 5A indicated by the solid line 13A in FIG. 2 is a characteristic in which the phase is closer to 180 degrees (that is, the impedance is lower) between the solid line 11A and the broken line 12A indicating the two phase characteristics. And the phase changes abruptly.
[0040]
From this, the phase characteristic indicated by the solid line 13A in the vicinity of the oscillation frequency fo can obtain a sufficiently large gradient as compared with the phase gradient of each resonance circuit.
Therefore, the Q value of the resonator 5A in the vicinity of the oscillation frequency fo can be significantly improved (increased).
[0041]
The voltage-controlled oscillator having the resonator 5A having the above configuration can change the frequency with a high Q value, and can reduce phase noise.
[0042]
Embodiment 2. FIG.
In the first embodiment, the frequency f2A at the first short-circuit point of the reflection phase characteristic (see the broken line 12A) of the second resonance circuit is set to the reflection phase characteristic (see the solid line 11A) of the first resonance circuit. Although the frequency is set lower than the frequency f3A at the second short-circuit point, the height relationship between the frequencies f2A and f3A may be set in reverse.
[0043]
FIG. 3 is an explanatory diagram showing the reflection phase characteristic of the resonator 5B according to the second embodiment of the present invention in which the frequency f2B is set higher than the frequency f3B, and the reflection phase of the resonator 5B at the connection point of the two resonance circuits. The characteristics are shown.
In this case, the circuit configuration of the resonator 5B is as shown in FIG. 1, and only the set values of the line lengths of the microstrip lines 6A and 8A are different.
[0044]
In FIG. 3, the same reference numerals as those described above (see FIG. 2) are given the same reference numerals or “B” after the same reference numerals, and the thin solid line 11B is the reflection phase characteristic of the first resonance circuit, and the broken line 12B. Represents the reflection phase characteristic of the second resonance circuit, and the thick solid line 13B represents the reflection phase characteristic of the resonator 5B.
[0045]
Next, the operation according to Embodiment 2 of the present invention will be described with reference to FIG. 3 together with FIG.
As indicated by a broken line 12B in FIG. 3, the first short-circuit point of the second resonance circuit is set to a frequency f2B that is sufficiently higher than the desired oscillation frequency fo.
[0046]
Further, the first short circuit of the first resonance circuit is set so that the reflection phase characteristic 13B of the resonator 5B in which the resonance circuits are connected in parallel resonates in parallel at the desired oscillation frequency fo (that is, the phase becomes 0 degree). The point is set to a frequency f1B lower than the desired oscillation frequency fo.
[0047]
Here, since the frequency f2B is changed by changing the capacitance of the variable capacitance diode 4 in FIG. 1, the oscillation frequency fo can be changed accordingly.
[0048]
At this time, the frequency f2B, which is the first short circuit point of the second resonance circuit (see the broken line 12B), is changed to the second short circuit point (that is, the phase is -180 degrees) of the first resonance circuit (see the solid line 11B). Even if the frequency f3B is set higher than the frequency f3B, the reflection phase characteristic of the resonator 5B (see the solid line 13B) changes abruptly in the vicinity of the oscillation frequency fo. Therefore, the same effect as in the first embodiment can be obtained. can get.
[0049]
Embodiment 3 FIG.
In the first embodiment, the frequency at which the reflection phase of the second resonance circuit is 180 degrees is set higher than the oscillation frequency fo at the connection point of each resonance circuit in the resonator 5A, and the first resonance The frequency at which the reflection phase of the circuit is 180 degrees is set lower than the oscillation frequency fo so that the resonance frequency of the resonator 5A matches the oscillation frequency fo, but the frequency at which the reflection phase of each resonance circuit is 180 degrees. May be set in an inverse relationship to the oscillation frequency fo.
[0050]
FIG. 4 is a circuit configuration diagram showing Embodiment 3 of the present invention in which the frequency at which the reflection phase of each resonance circuit is 180 degrees is set in an inverse relationship to the oscillation frequency fo.
In FIG. 4, the same components as those described above (see FIG. 1) are denoted by the same reference numerals or “C” after the reference numerals, and detailed description thereof is omitted.
[0051]
In this case, the frequency at which the reflection phase of the first resonance circuit is 180 degrees at the connection point of each resonance circuit in the resonator 5C is set higher than the oscillation frequency fo, and the reflection phase of the second resonance circuit is The frequency of 180 degrees is set lower than the oscillation frequency fo so that the resonance frequency of the resonator 5C matches the oscillation frequency fo.
[0052]
FIG. 5 is an explanatory diagram showing the reflection phase characteristic of the resonator 5C according to Embodiment 3 of the present invention, and shows the reflection phase characteristic of the resonator 5C at the connection point of each resonance circuit. In FIG. 5, the same reference numerals as those described above (see FIG. 2) are given the same reference numerals or “C” after the reference signs, 11 C is the reflection phase characteristic of the first resonance circuit, and 12 C is the second resonance. The reflection phase characteristic of the circuit, 13C, indicates the reflection phase characteristic of the resonator 5C.
[0053]
Next, the operation according to the third embodiment of the present invention shown in FIG. 4 will be described with reference to FIG.
As shown by a straight line 11C in FIG. 5, the first short-circuit point of the first resonance circuit is set to a frequency f1C that is sufficiently higher than the desired oscillation frequency fo.
[0054]
Further, the first short-circuit point of the second resonance circuit is set so that the reflection phase characteristic of the resonator 5C (see the solid line 13C) resonates in parallel at the desired oscillation frequency fo (that is, the phase becomes 0 degree). The frequency f2C is set lower than the desired oscillation frequency fo.
[0055]
Here, since the frequency f2C is changed by changing the capacitance of the variable capacitance diode 4, the oscillation frequency fo can be changed accordingly.
[0056]
The reflection phase characteristic of the resonator 5C (see the solid line 13C) has a characteristic in which the phase is close to 180 degrees (that is, the impedance is lower) of the two reflection phase characteristics (see the solid line 11C and the broken line 12C). The phase changes abruptly.
[0057]
From this, the reflection phase characteristic of the resonator 5C (see the solid line 13C) can obtain a sufficiently large gradient in the vicinity of the oscillation frequency fo as compared to the phase gradient of each resonance circuit. Can be significantly improved.
[0058]
As described above, the voltage controlled oscillator having the resonator 5C having the above-described configuration can change the frequency with a high Q value, and can reduce the phase noise.
[0059]
Embodiment 4 FIG.
In the third embodiment, the frequency f1C at the first short circuit point of the reflection phase characteristic (see the solid line 11C) of the first resonance circuit is set to the reflection phase characteristic (see the broken line 12C) of the second resonance circuit. Although the frequency is set lower than the frequency f4C at the second short-circuit point, the height relationship between the frequencies f1C and f4C may be set in reverse.
[0060]
FIG. 6 is an explanatory diagram showing the reflection phase characteristics of the resonator 5D according to the fourth embodiment of the present invention in which the frequency f1D is set higher than the frequency f4D, and the reflection phase of the resonator 5D at the connection point of the two resonance circuits. The characteristics are shown.
In this case, the circuit configuration of the resonator 5D is as shown in FIG. 4, and only the set values of the line lengths of the microstrip lines 6C and 8C are different.
[0061]
In FIG. 6, the same reference numerals as those described above (see FIG. 5) are given the same reference numerals or “D” after the same reference numerals, and the thin solid line 11 </ b> D represents the reflection phase characteristic of the first resonance circuit, and the broken line 12 </ b> D. Represents the reflection phase characteristic of the second resonance circuit, and the thick solid line 13D represents the reflection phase characteristic of the resonator 5D.
[0062]
Next, the operation according to the fourth embodiment of the present invention will be described with reference to FIG. 6 together with FIG.
The first short-circuit point of the first resonance circuit (see solid line 11D) is set to a frequency f1D that is sufficiently higher than the desired oscillation frequency fo.
[0063]
Further, the first resonance circuit (see the broken line 12D) of the second resonance circuit (see the broken line 12D) is set so that the reflection phase characteristic of the resonator 5D (see the solid line 13D) resonates in parallel at the desired oscillation frequency fo (that is, the phase becomes 0 degree). The short-circuit point is set to a frequency f2 lower than the desired oscillation frequency fo.
[0064]
Here, since the frequency f2D is changed by changing the capacitance of the variable capacitance diode 4 (see FIG. 4), the oscillation frequency fo can be changed accordingly.
[0065]
At this time, even if the first short circuit point f1D of the first resonance circuit (see the solid line 11D) is set higher than the second short circuit point f4D of the second resonance circuit (see the broken line 12D), the oscillation frequency fo Since the reflection phase characteristic of the resonator 5D (see the solid line 13D) changes abruptly in the vicinity, the same effect as in the third embodiment is obtained.
[0066]
Embodiment 5 FIG.
In the first to fourth embodiments, the second resonant circuit is directly connected to the connection point with the first resonant circuit. However, the second resonant circuit may be connected via a coupling line.
[0067]
FIG. 7 is a circuit configuration diagram showing Embodiment 5 of the present invention in which a coupling line is inserted into the second resonance circuit.
In FIG. 7, the same components as those described above (see FIGS. 1 and 4) are denoted by the same reference numerals, or “E” after the reference numerals, and detailed description thereof is omitted.
[0068]
In this case, a coupling line 9E is interposed between the connection point of each resonance circuit in the resonator 5E and the microstrip line 6E (second circuit element).
The microstrip line 8E constitutes a first resonance circuit, and the coupling line 9E, the microstrip line 6E, and the variable capacitance diode 4 constitute a second resonance circuit.
[0069]
As shown in FIG. 7, by connecting the coupling line 9E in addition to the microstrip line 6E, in addition to the above-described effects, the functions of the inductance component necessary for parallel resonance and the band-pass filter can be achieved. The second resonance circuit can be operated only in a desired frequency band.
[0070]
Embodiment 6 FIG.
In the first to fifth embodiments described above, the first resonance circuit is configured by a microstrip line with an open tip (or short-circuited tip). However, similarly to the second resonance circuit, the microstrip line and the variable capacitance diode are used. You may comprise by a series circuit.
[0071]
FIG. 8 is a circuit configuration diagram showing Embodiment 6 of the present invention in which the first resonance circuit is configured in the same manner as the second resonance circuit.
In FIG. 8, the same components as those described above (see FIGS. 1, 4, and 7) are denoted by the same reference numerals, or “F” after the reference numerals, and detailed description thereof is omitted. Also in this case, the operation principle is the same as described above.
[0072]
Reference numerals 2a, 4a, and 6a denote a variable voltage power source, a variable capacitance diode, and a microstrip line that form the second resonance circuit, respectively.
Similarly, 2b, 4b, and 6b are a variable voltage power source, a variable capacitance diode, and a microstrip line that constitute the first resonance circuit, respectively.
[0073]
FIG. 9 is an explanatory diagram showing the reflection phase characteristics of the resonator 5F according to the sixth embodiment of the present invention, and the method of setting the frequencies f1F, f2F, and f4F at the respective short-circuit points is the same as described above.
[0074]
As shown in FIG. 8, by providing the variable capacitance diode 4b also in the first resonance circuit, in addition to the above-described effects, the short-circuit points f1F and f2F of each resonance circuit in FIG. 9 can be moved simultaneously. , Variation in the Q value can be reduced.
[0075]
Further, by setting a DC voltage from a variable voltage power supply 2b different from the variable voltage power supply 2a as a voltage applied to the variable capacitance diode 4b, the variable frequency range can be widened.
[0076]
Embodiment 7 FIG.
In the first to sixth embodiments, the microstrip line (distributed constant line) is provided as the circuit element in each resonance circuit, but an inductor may be provided.
[0077]
FIG. 10 is a circuit diagram showing a seventh embodiment of the present invention in which an inductor is provided in place of the microstrip line in the resonator.
In FIG. 10, the same components as those described above (see FIGS. 1, 4, 7, and 8) are denoted by the same reference numerals or “G” after the reference numerals, and detailed description thereof is omitted. .
[0078]
Reference numeral 21 a denotes an inductor that is connected to a connection point of each resonance circuit to form a second resonance circuit, and the other end is connected to the variable capacitance diode 4.
Reference numeral 21b denotes an inductor constituting the second resonance circuit, and the other end is grounded.
[0079]
In the above-described embodiment, the inductance component necessary for the resonance circuit is created by the microstrip line. However, the location of the microstrip line is replaced with the lumped constant inductances 21a and 21b as shown in FIG. As a result, in addition to the above-described operation and effect, further downsizing can be realized and a higher Q value can be set.
[0080]
Embodiment 8 FIG.
Although the oscillation FET is used as the active element 3 in the first to seventh embodiments, a bipolar transistor, HBT, high mobility transistor (HEMT), or the like may be used.
[0081]
In this case as well, since the Q value of the resonator can be increased as described above, it can be applied in common regardless of which element is selected as the active element 3.
[0082]
Further, for example, higher frequency can be realized by using HEMT, and phase noise can be further reduced by applying a bipolar element.
[0083]
Embodiment 9 FIG.
In the above first to eighth embodiments, the output terminal of the active element 3 is directly connected to the oscillation output terminal 1, but an N-1 harmonic reflection circuit may be interposed.
[0084]
FIG. 11 is a circuit configuration diagram showing Embodiment 9 of the present invention in which an N−1 harmonic reflection circuit is inserted between the oscillation output terminal 1 and the active element 3.
In FIG. 11, the same components as those described above (see FIGS. 1, 4, 7, 8, and 10) are denoted by the same reference numerals or “H” after the reference numerals. Is omitted.
[0085]
In this case, an N-1 harmonic reflection circuit 22H is interposed between the output terminal of the active element 3 and the oscillation output terminal 1.
As shown in FIG. 11, the N-1 harmonic reflection circuit including the fundamental wave is provided in the output circuit of the voltage controlled oscillator and the N harmonic wave of the oscillation frequency fo is output from the oscillation output terminal 1 to thereby obtain the above-described effects. In addition, the oscillation frequency can be further increased.
[0086]
【The invention's effect】
As described above, according to the present invention, the oscillation output terminal for supplying a desired oscillation frequency, the resonator having the first and second resonance circuits connected in parallel to each other, and the first and second resonance circuits A phase adjustment circuit connected to the connection point of the oscillation circuit, and an oscillation element having a negative resistance inserted between the phase adjustment circuit and the oscillation output terminal, the second resonance circuit includes a variable capacitance diode, A voltage controlled oscillator in which an oscillation frequency is variably set according to the magnitude of a DC voltage applied to a variable capacitance diode, wherein the first resonance circuit includes a first distributed constant line or a lumped constant inductor. The second resonance circuit includes a second circuit element including a second distributed constant line or a lumped constant inductor, and a variable capacitance diode connected in series to the second circuit element. The frequency at which the reflection phase of the second resonance circuit is 180 degrees at the connection point of the first and second resonance circuits is set to be higher than the oscillation frequency, and the first is the connection point of the first and second resonance circuits. The frequency at which the reflection phase of the resonance circuit is 180 degrees is set lower than the oscillation frequency so that the resonance frequency of the resonator matches the oscillation frequency. There is an effect that a voltage controlled oscillator having improved noise characteristics can be obtained.
[0087]
Further, according to the present invention, an oscillation output terminal that supplies a desired oscillation frequency, a resonator having first and second resonance circuits connected in parallel to each other, and a connection point between the first and second resonance circuits A phase adjustment circuit connected to the oscillation circuit, and an oscillation element having a negative resistance inserted between the phase adjustment circuit and the oscillation output terminal. The second resonance circuit includes a variable capacitance diode, and the variable capacitance diode And a first circuit element including a first distributed constant line or a lumped constant inductor, wherein the oscillation frequency is variably set according to the magnitude of the DC voltage applied to the first resonant circuit. The second resonant circuit includes a second circuit element including a second distributed constant line or a lumped constant inductor, and a variable capacitance diode connected in series to the second circuit element. Oh The frequency at which the reflection phase of the first resonance circuit is 180 degrees at the connection point of the second resonance circuit is set to be higher than the oscillation frequency, and the second resonance is generated at the connection point of the first and second resonance circuits. The frequency at which the reflection phase of the circuit is 180 degrees is set lower than the oscillation frequency so that the resonance frequency of the resonator matches the oscillation frequency. Therefore, the Q value near the oscillation frequency is increased to increase the phase noise characteristic. There is an effect that a voltage-controlled oscillator with improved can be obtained.
[0088]
In addition, according to the present invention, the second resonance circuit includes the coupling line inserted between the connection point of the first and second resonance circuits and the second circuit element, so that it is necessary for parallel resonance. There is an effect that a voltage-controlled oscillator that can serve both as an inductance component and a band-pass filter and can operate the second resonance circuit only in a desired frequency band is obtained.
[0089]
In addition, according to the present invention, the first resonant circuit includes the second variable capacitance diode connected in series with the first circuit element. Therefore, by simultaneously moving the short-circuit point of each resonant circuit, the Q value In addition to being able to suppress fluctuations, there is an effect that a voltage controlled oscillator capable of widening the variable frequency range can be obtained by setting a DC voltage individually applied to the second variable capacitance diode.
[0090]
Further, according to the present invention, since the first and second distributed constant lines are constituted by the first and second microstrip lines, respectively, the line length can be easily variably set, and each resonance There is an effect that a voltage controlled oscillator capable of easily adjusting the short-circuit point of the circuit can be obtained.
[0091]
Further, according to the present invention, since the oscillating element is composed of an active element composed of a high mobility transistor or a bipolar transistor, a voltage controlled oscillator capable of realizing higher frequency or further reducing phase noise. Is effective.
[0092]
In addition, according to the present invention, the N-1 harmonic reflection circuit inserted between the oscillation element and the oscillation output terminal is provided, and the N harmonic of the oscillation frequency is output from the oscillation output terminal. There is an effect of obtaining a voltage controlled oscillator capable of increasing the oscillation frequency.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing reflection phase characteristics of the resonator according to the first embodiment of the invention.
FIG. 3 is an explanatory diagram showing reflection phase characteristics of a resonator according to a second embodiment of the present invention.
FIG. 4 is a circuit configuration diagram showing Embodiment 3 of the present invention.
FIG. 5 is an explanatory diagram showing reflection phase characteristics of a resonator according to a third embodiment of the present invention.
FIG. 6 is an explanatory diagram showing reflection phase characteristics of a resonator according to a fourth embodiment of the present invention.
FIG. 7 is a circuit configuration diagram showing Embodiment 5 of the present invention.
FIG. 8 is a circuit configuration diagram showing Embodiment 6 of the present invention.
FIG. 9 is an explanatory diagram showing reflection phase characteristics of a resonator according to a sixth embodiment of the invention.
FIG. 10 is a circuit configuration diagram showing Embodiment 7 of the present invention.
FIG. 11 is a circuit configuration diagram showing Embodiment 9 of the present invention.
FIG. 12 is a circuit configuration diagram showing a conventional voltage controlled oscillator.
FIG. 13 is an explanatory diagram showing the operation of a conventional voltage controlled oscillator.
FIG. 14 is an explanatory diagram showing the reflection amplitude on the resonator side by a conventional voltage controlled oscillator.
FIG. 15 is an explanatory diagram showing the reflection amplitude on the oscillation element side by a conventional voltage controlled oscillator.
FIG. 16 is an explanatory diagram showing loop gain by a conventional voltage controlled oscillator.
FIG. 17 is an explanatory diagram showing a loop phase by a conventional voltage controlled oscillator.
FIG. 18 is an explanatory diagram showing a phase of a connection point of each resonance circuit by a conventional voltage controlled oscillator.
[Explanation of symbols]
1 Oscillation output terminal 2, 2a, 2b Variable voltage power supply, 3 Active element, 4, 4a, 4b Variable capacitance diode, 5A-5H Resonator, 6A, 6a, 6b, 6C, 6E, 6H Microstrip line (second 8A, 8C, 8E, 8H Microstrip line (first resonant circuit), 9E Coupling line, 10A, 10C, 10E-10H Microstrip line for phase adjustment, 11A-11D, 11F First Reflection phase characteristic of resonance circuit, 12A to 12D, 12F Reflection phase characteristic of second resonance circuit, 13A to 13D, 13F Reflection phase characteristic of resonator, 21a, 21b Lumped constant inductor, 22H N-1 harmonic wave reflection circuit, f1A, f1D, f1F Phase short circuit point of the first resonance circuit, f2A, f2D, f2F Phase short circuit point of the second resonance circuit, fo Oscillation frequency .

Claims (7)

An oscillation output terminal for supplying a desired oscillation frequency;
A resonator having first and second resonant circuits connected in parallel to each other;
A phase adjustment circuit connected to a connection point of the first and second resonance circuits;
An oscillation element having a negative resistance inserted between the phase adjustment circuit and the oscillation output terminal;
The second resonant circuit includes a variable capacitance diode,
A voltage controlled oscillator in which the oscillation frequency is variably set according to the magnitude of a DC voltage applied to the variable capacitance diode;
The first resonant circuit is constituted by a first circuit element including a first distributed constant line or a lumped constant inductor,
The second resonant circuit includes a second circuit element including a second distributed constant line or a lumped constant inductor, and the variable capacitance diode connected in series to the second circuit element.
The frequency at which the reflection phase of the second resonance circuit is 180 degrees at the connection point of the first and second resonance circuits is set higher than the oscillation frequency,
The frequency at which the reflection phase of the first resonance circuit is 180 degrees at the connection point of the first and second resonance circuits is greater than the oscillation frequency so that the resonance frequency of the resonator matches the oscillation frequency. A voltage-controlled oscillator characterized by being set low. An oscillation output terminal for supplying a desired oscillation frequency;
A resonator having first and second resonant circuits connected in parallel to each other;
A phase adjustment circuit connected to a connection point of the first and second resonance circuits;
An oscillation element having a negative resistance inserted between the phase adjustment circuit and the oscillation output terminal;
The second resonant circuit includes a variable capacitance diode,
A voltage controlled oscillator in which the oscillation frequency is variably set according to the magnitude of a DC voltage applied to the variable capacitance diode;
The first resonant circuit is constituted by a first circuit element including a first distributed constant line or a lumped constant inductor,
The second resonant circuit includes a second circuit element including a second distributed constant line or a lumped constant inductor, and the variable capacitance diode connected in series to the second circuit element.
The frequency at which the reflection phase of the first resonant circuit is 180 degrees at the connection point of the first and second resonant circuits is set higher than the oscillation frequency,
The frequency at which the reflection phase of the second resonance circuit is 180 degrees at the connection point of the first and second resonance circuits is greater than the oscillation frequency so that the resonance frequency of the resonator matches the oscillation frequency. A voltage-controlled oscillator characterized by being set low. The said 2nd resonance circuit contains the coupling line inserted between the connection point of the said 1st and 2nd resonance circuit, and the said 2nd circuit element, The Claim 1 or Claim 2 characterized by the above-mentioned. The voltage controlled oscillator described in 1. 4. The voltage control according to claim 1, wherein the first resonance circuit includes a second variable capacitance diode connected in series to the first circuit element. 5. Oscillator. 5. The voltage control according to claim 1, wherein the first and second distributed constant lines are configured by first and second microstrip lines, respectively. 6. Oscillator. 6. The voltage controlled oscillator according to claim 1, wherein the oscillating element is constituted by an active element made of a high mobility transistor or a bipolar transistor. An N-1 harmonic reflection circuit inserted between the oscillation element and the oscillation output terminal;
The voltage controlled oscillator according to any one of claims 1 to 6, wherein an N-fold wave of the oscillation frequency is output from the oscillation output terminal.

Images