JP2004320664A - Microwaveband voltage controlled oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwaveband voltage controlled oscillator in which the variable frequency width can be expanded without deteriorating the phase noise characteristics. <P>SOLUTION: The microwaveband voltage controlled oscillator is provided with a transistor TR11 for oscillation, a stub Stub18 provided in an emitter electrode, a varactor diode circuit (Stub12, C13 and Stub14, C15) parallel connecting a plurality of serial connection circuits composed of varactors and stubs, a microstrip line Line16 of which one end is connected to a base electrode and the other end is connected to the varactor, and a plurality of control circuits (APCV1, 2) for independently applying a control voltage to each of varactors (C13 and C15). Any one of the control voltages to be independently applied to the respective varactors is successively variably controlled within the range from its lower limit to its upper limit, and all the range of variable synthetic capacity of the varactor diode circuits is controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a microwave band voltage controlled oscillator, and more particularly to a microwave band voltage controlled oscillator having improved control (modulation) characteristics.
[0002]
[Prior art]
FIG. 7 is a diagram showing a basic circuit configuration of a Colpitts oscillator. This is a basic oscillation circuit usually used in a microwave band oscillator. A common-collector transistor is used as an active element for oscillation. A capacitor C23 is connected between the base and the emitter, between the emitter and the ground, and between the base and the ground. This is a Colpitts oscillator in which C24 and coil L22 are connected.
[0003]
FIG. 8 is a diagram showing a configuration of a microwave band voltage controlled oscillator (microwave band VCO) using a microstrip line resonator among conventional microwave band voltage controlled oscillators having the basic circuit configuration shown in FIG. .
[0004]
This circuit configuration has a base-emitter parasitic capacitance of the transistor TR31 in C23, an open stub Stub36 of a microstrip line in C24, an open stub Stub32, a variable capacitance C33, and a microstrip line in relation to FIG. A circuit portion including the line Line34 and the capacitor C35 corresponds to L22 (hereinafter, this portion is referred to as a "resonator portion").
[0005]
[Problems to be solved by the invention]
The operating principle of the microwave band VCO shown in FIG. 8 is that the variable capacitor C33 is constituted by a varactor diode (variable capacitor diode), and by changing the voltage applied to the varactor diode, the electrical phase length of the resonator portion is changed. And the oscillation frequency is determined correspondingly. Therefore, the variable frequency width is determined by the capacitance change ratio of the variable capacitor C33 and the equivalent capacitance adjusted by the length of the open stub Stub 32 at the tip of the resonator portion.
[0006]
Therefore, in order to extend the variable frequency range of the Colpitts oscillator, it is conceivable to (1) use a varactor diode having a large capacitance change ratio, (2) increase the equivalent capacitance of the Stub 32, and the like.
[0007]
Here, in order to widen the frequency variable range, it is most desirable to increase the change ratio of the varactor diode in (1). However, since this characteristic can be controlled by the physical properties of the varactor diode, the change ratio is limited. Is difficult to set freely. Therefore, the variable frequency width is expanded by adjusting the Stub 32 of (2), but the coupling of the varactor is strengthened. In this case, the modulation sensitivity (the amount of frequency change per applied voltage) naturally increases with the expansion of the variable frequency width.
[0008]
FIG. 9 is a diagram showing characteristics of the oscillation frequency and the modulation sensitivity of the conventional Colpitts type oscillator shown in FIG. 8 with respect to a voltage applied to a varactor diode. If the variable frequency width of the frequency characteristic (solid line) of the control range by the applied voltage is expanded (thick line) by adjusting Stub, the modulation sensitivity characteristic (dotted line) also increases (thick line).
[0009]
On the other hand, the modulation sensitivity characteristic is also expanded by the expansion of the variable frequency width, and the frequency change sensitivity to a very small voltage of the applied voltage (APCV) of the varactor diode is particularly increased. The influence of the frequency shift and the like due to the noise of the generation part becomes remarkable.
[0010]
Therefore, in the microwave band VCO having the circuit configuration shown in FIG. 8, there is a trade-off between the expansion of the variable frequency width and the improvement of the phase noise characteristic. In microwave communication and the like, since a signal having excellent phase noise characteristics is required, expansion of the variable frequency width by a method that causes deterioration of the phase noise characteristics may not be allowed.
[0011]
An object of the present invention is to provide a microwave band voltage controlled oscillator capable of expanding a variable frequency width and improving a phase noise characteristic.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a microwave band voltage controlled oscillator capable of expanding a variable frequency width without deteriorating phase noise characteristics.
[0012]
[Means for Solving the Problems]
The microwave band voltage controlled oscillator of the present invention is a microwave band voltage controlled oscillator that controls the oscillation frequency with a varactor diode,
A control voltage is independently applied to a varactor diode circuit (variable capacitance circuit) in which a plurality of varactor diodes (for example, C13 and C15 in FIG. 1) and an open stub series connection circuit are connected in parallel, and each varactor diode of the varactor diode circuit. And a plurality of control circuits (for example, APCV1 and APCV2 in FIG. 1).
[0013]
Further, the microwave band voltage controlled oscillator has an active element for oscillation, an open stub provided on an output electrode of the active element, and one end connected to the control electrode of the active element and the other end of the varactor diode circuit. And a transmission line (for example, Line 16 in FIG. 1) connected to each varactor diode side. A grounded-collector transistor for oscillation, an open stub provided at the emitter electrode of the transistor, and one end connected to the base electrode of the transistor and the other end connected to each varactor diode side of the varactor diode circuit. And a transmission line, comprising a Colpitts oscillator.
[0014]
Further, the microwave band voltage controlled oscillator variably controls one of the control voltages to be independently applied to each varactor diode by the plurality of control circuits within a range from a lower limit to an upper limit of the varactor diode. Controls the entire variable range of the combined capacitance of the diode circuit.By independently adjusting the length of multiple open stubs, the dependence of the applied voltage on the modulation sensitivity within the variable frequency range Is reduced. Further, by individually adjusting the lengths of the plurality of open stubs, a part of the frequency characteristics is made to overlap, and a control voltage that is variably controlled in any of the overlapping frequency ranges is switched. I do. In the variable control of the control voltage applied to the plurality of control terminals, the variable control voltage in the range of the minimum value and the maximum value of the variable range of each control voltage is variable control of only one of the plurality of varactor diodes. The control is performed such that the variable control on the upper or lower limit of the control voltage partially overlaps with the variable control on the lower or upper limit of another control voltage.
[0015]
More specifically, in a microwave band voltage controlled oscillator using a microstrip line resonator, a frequency control unit composed of a varactor diode is configured by connecting a plurality of varactor diodes and a series connection circuit of an open stub in parallel. By individually controlling the varactor diodes, the variable frequency width is expanded without affecting other characteristics required for the voltage controlled oscillator, such as the control voltage range, modulation sensitivity, and phase noise characteristics.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
(Description of configuration)
FIG. 1 is a diagram showing a configuration of a microwave band VCO according to a first embodiment of the present invention. A transistor TR11 as an active element for oscillation, an open stub Stub18 provided by a microstrip line provided on the emitter electrode side of the transistor TR11, and an open stub Stub12 provided on the base electrode side of the transistor TR11 and a variable capacitor C13 composed of a varactor diode. A series connection circuit and a series connection circuit of an open stub Stub14 and a variable capacitance C15 composed of a varactor diode are connected in parallel on the variable capacitance side, and comprise a series connection circuit of a microstrip line Line16 and a capacitance C17 connected to the connection point. Input terminals (control terminals) of the applied voltages APCV1 and APCV2 provided at the circuit portion and the connection point between the open stub Stub12 and the variable capacitor C13 and the connection point between the open stub Stub14 and the variable capacitor C15, respectively. If, it consists of.
[0017]
In the Colpitts oscillator according to the present embodiment, the feedback circuit has a parasitic capacitance between the base and the emitter of the transistor TR11 and the capacitance of the open stub Stub18, the open stub Stub12, the variable capacitor C13 and the open stub Stub14, the variable capacitor C15. It is composed of a circuit portion composed of a microstrip line Line16 and a capacitor C17.
[0018]
The Colpitts oscillator according to the present embodiment is different from the configuration of the conventional Colpitts oscillator shown in FIG. 8 in that a series circuit of a varactor diode and an open stub is connected to a resonator (Line 16) in parallel (Stub12 and C13 and Stub14). And C15 in parallel).
[0019]
According to the configuration of the present embodiment, it is possible to reduce the dependence of the modulation sensitivity on the applied voltage within the variable frequency range by independently adjusting the lengths of Stub 12 and Stub 14.
[0020]
The voltage applied to the variable capacitors C13 and C15 (APCV1 and APCV2) is configured to be supplied independently of each other, so that the variable frequency range is expanded without controlling the applied voltage and causing the deterioration of the phase noise characteristic. It is possible to do.
[0021]
(Description of operation)
A preferred operation of the microwave band VCO of the first embodiment will be described below. In this embodiment, one of the applied voltages APCV1 and APCV2 of the two control terminals is operated as a fixed voltage, and the other is operated as a variable voltage for frequency control. As a specific example of this control method, the variable frequency range is divided into two high and low frequency ranges,
(1) In a low frequency portion, the applied voltage APCV1 is fixed to 0 V, and the applied voltage APCV2 is changed as a frequency control voltage in the range of APCV2 = 0 to 10 V.
(2) In a high frequency portion, APCV2 is fixed at 10V, and APCV1 is changed as a frequency control voltage in a range of APCV1 = 0 to 10V.
It is preferable to adopt the control method described above.
[0022]
FIG. 2 is a diagram illustrating the relationship between the control voltage, the oscillation frequency, and the modulation sensitivity when the control method according to the present embodiment is used. As can be seen from the figure, the modulation sensitivity can be suppressed lower than in the case where the variable frequency range is widened only by adjusting the Stub 32 by the conventional configuration shown in FIG. Low modulation sensitivity means that the frequency stability against external noise can be suppressed low, and as a result, phase noise also exhibits excellent characteristics.
(Other embodiments)
In the first embodiment, an example has been described in which two series-connected circuits including an open stub and a variable capacitor are provided in a resonator portion. However, by increasing the series-connected circuit, modulation sensitivity can be increased. It is possible to further suppress.
[0023]
FIG. 3 is a diagram showing a configuration of the second embodiment using three series-connected circuits. Another series connection circuit of a varactor diode and an open stub is connected in parallel to the resonator section, and three applied voltages APCV1, APCV2, and APCV3 are independently applied, so that the modulation sensitivity to the expansion of the variable frequency range is improved. More increase. As a result, it is possible to suppress the deterioration of the phase noise characteristic.
[0024]
As a specific example of the control method according to the second embodiment, the variable frequency range is divided into three low, medium, and high frequency ranges.
(1) In the low frequency portion, the applied voltage APCV1 is fixed to 0 V and APCV2 is fixed to 0 V, and the applied voltage APCV3 is changed as a frequency control voltage in the range of APCV3 = 0 to 10 V.
(2) In the middle part of the frequency, the applied voltage APCV1 is fixed to 0 V and APCV3 is fixed to 10 V, and the applied voltage APCV2 is changed as a frequency control voltage in the range of APCV2 = 0 to 10 V.
{Circle around (3)} APCV2 = 10V and APCV3 = 10V are fixed in the high frequency portion, and APCV1 is changed as a frequency control voltage in the range of APCV1 = 0 to 10V.
It is preferable to adopt the control method described above.
[0025]
FIG. 4 is a diagram illustrating the relationship between the control voltage, the oscillation frequency, and the modulation sensitivity according to the second embodiment. As shown in FIG. 4, the increase in modulation sensitivity can be further suppressed with respect to the expansion of the variable frequency range due to the increase in the series connection circuit, and the deterioration of the phase noise characteristic is suppressed.
[0026]
FIG. 5 is a diagram showing the configuration of the third embodiment. By further connecting a plurality (n) of varactor diodes and open stubs to the resonator portion, it is possible to further suppress the increase in modulation sensitivity with respect to the expansion of the variable frequency range, and as a result, to suppress the deterioration of phase noise characteristics. It is composed. In the third embodiment, the variable frequency range is divided into a plurality of frequency ranges in accordance with the parallel number n of the resonator portions, and similarly, the applied voltages APCV1 to APCVn corresponding to the low to high frequency ranges are respectively sequentially determined. Control is performed so as to increase from the minimum value to the maximum value.
[0027]
A fourth embodiment in which the variation in the modulation sensitivity in the above embodiment is further suppressed will be described. In the fourth embodiment, variations in modulation sensitivity are suppressed by individually adjusting the electrical lengths of open stubs of a series connection circuit including a plurality of open stubs and variable capacitors.
FIG. 6 is a diagram illustrating frequency characteristics and modulation sensitivity characteristics according to the fourth embodiment. The fourth embodiment is an example of a configuration including two series-connected circuits each including an open stub and a variable capacitor, and optimizes electric length adjustment of the open stubs Stub12 and Stub14.
[0028]
For example, in a microwave band voltage controlled oscillator having two series-connected circuits, the length of the Stub 12 is reduced to reduce the capacitance, the length of the Stub 14 is set to be longer than that of the Stub 12, and the capacitance is set to be larger. Modulation sensitivity and variation can be suppressed in the entire frequency range expanded by a low frequency region where APCV2 is varied at 0V and a high frequency region where APCV1 is varied by setting APCV2 = 10V.
[0029]
In the present embodiment, the variable frequencies can be partially overlapped between the control range (1) and the control range (2), and the variable frequency is set as a switching point between the control range (1) and the control range (2). By appropriately selecting within the overlapping range, control is performed so as to further suppress the variation in modulation sensitivity.
The above adjustment method is similarly applicable to a microwave band voltage controlled oscillator having three or more series connected circuits. Variations in modulation sensitivity can be suppressed by sequentially adjusting the length of the Stub from the low-frequency region to the high-frequency region, and the switching control is appropriately selected as a control voltage switching point.
[0030]
In the above-described embodiment, an example in which the configuration and the control method in which the variable control of the voltage applied to the control terminal is always performed only by a single device has been described, but the configuration is such that the control voltage is partially overlapped and variable. It is also possible. The control voltage applied independently to each varactor diode by the plurality of control circuits is partially overlapped within the range from the lower limit to the upper limit, and is variably controlled by the control voltage sequentially, and the combined capacitance of the varactor diode circuit is variable. By performing control over the entire range, modulation sensitivity and variations are suppressed over the entire frequency range.
[0031]
In the above description, the Colpitts-type transistor oscillator configuration was described as the configuration of the voltage-controlled oscillator.However, as a preferred oscillator configuration of the present invention, an active element for oscillation, an open stub provided on the output electrode of the active element, A voltage-controlled oscillator or the like having one end connected to the control electrode of the active element and the other end connected to each varactor diode side of the varactor diode circuit, that is, the oscillation frequency can be controlled by the varactor diode. It goes without saying that the present invention can be applied to a voltage controlled oscillator.
[0032]
【The invention's effect】
According to the microwave band voltage controlled oscillator of the present invention, the varactor diode circuit for controlling the oscillation frequency employs a configuration in which a plurality of varactor diodes and open stub series-connected circuits are connected in parallel, and the control voltage is independently applied to each varactor diode. Is applied, it is possible to suppress a change in modulation sensitivity even if the variable frequency range is sufficiently expanded, as compared with a case where the variable frequency range is expanded only by adjustment using a single open stub. Further, since the modulation sensitivity is low, the frequency stability against external noise can be suppressed low, and as a result, it is possible to obtain excellent characteristics with respect to phase noise.
[0033]
In particular, the control voltage independently applied to each varactor diode is sequentially variably controlled within a range from the lower limit to the upper limit, and control over the variable range of the combined capacitance of the varactor diode circuit is performed. As a result, the modulation sensitivity can be kept low.
Further, by appropriately selecting the lengths of the plurality of open stubs, it is possible to set each frequency variable width and modulation sensitivity to be as equal as possible. Furthermore, the electric length adjustment of a plurality of open stubs is further independently and independently optimized, so that a part of the control range overlaps in the frequency domain, and the switching point is appropriately selected to further reduce the variation in modulation sensitivity. It becomes possible.
[0034]
As described above, according to the present invention, while the variable frequency range is expanded, the modulation sensitivity is kept low, so that the phase noise characteristics are not degraded, and the variation in the modulation sensitivity within the variable frequency range can be suppressed. A suitable microwave band voltage controlled oscillator can be realized.For example, in the application to a voltage controlled oscillator of a PLL circuit, the frequency is locked, and the margin for determining the constant with respect to the variation of the modulation sensitivity of the PLL circuit is increased, so that the design becomes easy. There is also the advantage of becoming.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a diagram illustrating a relationship among a control voltage, an oscillation frequency, and a modulation sensitivity according to the first embodiment.
FIG. 3 is a diagram illustrating a configuration of a second embodiment.
FIG. 4 is a diagram illustrating a relationship between a control voltage, an oscillation frequency, and modulation sensitivity according to a second embodiment.
FIG. 5 is a diagram illustrating a configuration of a third embodiment.
FIG. 6 is a diagram illustrating a control voltage, a frequency characteristic, and a modulation sensitivity characteristic according to a fourth embodiment.
FIG. 7 is a diagram showing a basic circuit configuration of a Colpitts oscillator.
FIG. 8 is a diagram showing a configuration of a microwave band voltage controlled oscillator using a microstrip line resonator made of a conventional Colpitts oscillator.
FIG. 9 is a diagram showing characteristics of applied voltage, oscillation frequency, and modulation sensitivity of a conventional Colpitts oscillator.
[Explanation of symbols]
TR11 Transistor C17 Capacitor Line, Line16 Microstrip transmission line C13, C15 Varactor diode Stub, Stub13, 15, 18 Open stub

Claims (6)

A microwave band voltage controlled oscillator that controls an oscillation frequency by a varactor diode,
A microcontroller comprising: a varactor diode circuit in which a plurality of varactor diode and open stub series-connected circuits are connected in parallel; and a plurality of control circuits that independently apply a control voltage to each varactor diode of the varactor diode circuit. Waveband voltage controlled oscillator. An active element for oscillation, an open stub provided on an output electrode of the active element, and a transmission line having one end connected to a control electrode of the active element and the other end connected to each varactor diode side of the varactor diode circuit. 2. The microwave band voltage controlled oscillator according to claim 1, comprising: A grounded collector transistor for oscillation, an open stub provided at the emitter electrode of the transistor, and a transmission line having one end connected to the base electrode of the transistor and the other end connected to each varactor diode side of the varactor diode circuit. 2. The microwave band voltage controlled oscillator according to claim 1, comprising: a Colpitts type oscillator. By controlling the control voltage applied independently to each varactor diode by the plurality of control circuits in a range from the lower limit to the upper limit, the composite capacitance of the varactor diode circuit can be varied. 4. The microwave band voltage controlled oscillator according to claim 1, wherein the entire range can be controlled. 5. The method according to claim 1, wherein the length of the plurality of open stubs is independently adjusted to reduce the dependency of the modulation sensitivity on the applied voltage within a variable frequency range. Microwave band voltage controlled oscillator. By independently adjusting the lengths of the plurality of open stubs, a part of the frequency characteristics are made to overlap, and a control voltage for variably controlling at any point within the overlapping frequency range is switched. The microwave band voltage controlled oscillator according to claim 4, wherein

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