JP2009118438A - Oscillation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the oscillation frequency of an oscillation circuit by a simple structure. <P>SOLUTION: First and second distribution constant lines 11 and 12 having a predetermined length are disposed to be approximately parallel to each other. A predetermined direct-current voltage VDD or direct current is supplied to first ends of the first and second distribution constant lines 11 and 12. One or a plurality of capacitative elements C11, C12, ... are connected between intermediate portions of the first distribution constant line 11 and intermediate portions of the second distribution constant line 12. An oscillation circuit in which switching means Q11 and Q12 are mutually connected is formed between second ends of the first and second distribution constant lines 11 and 12 and a ground potential part. The oscillation frequency can be controlled by setting the connecting positions of the capacitative elements C11, C12, ... on the first and second distribution constant lines 11 and 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oscillation circuit that oscillates a high-frequency signal, and more particularly to an oscillation circuit capable of high-resolution oscillation frequency control.

An example of a conventional oscillation circuit is shown in FIG.
The configuration of FIG. 7 will be described. A power supply terminal capable of obtaining a predetermined DC voltage VDD is connected to one end of each of the switching elements Q1 and Q2, and the oscillation signal output terminals 2 and 3 are connected to the other ends of the switching elements Q1 and Q2. Pull out. Switching elements Q1 and Q2 use P-type MOS transistors. Then, the other end side of the switching element Q1 is connected to the gate terminal of the switching element Q2, and the other end side of the switching element Q2 is connected to the gate terminal of the switching element Q1.

  The other end of the switching element Q1 is connected to one end of the switching element Q3, and the other end of the switching element Q3 is grounded. Further, the other end of the switching element Q2 is connected to one end of the switching element Q4, and the other end of the switching element Q3 is grounded. Then, one end side of the switching element Q3 is connected to the gate terminal of the switching element Q4, and one end side of the switching element Q4 is connected to the gate terminal of the switching element Q3.

A coil L1 is connected between a connection point between the other end of the switching element Q1 and one end of the switching element Q3, and a connection point between the other end of the switching element Q2 and one end of the switching element Q4. A series circuit of C1 and C2 is connected.
Here, a varactor whose capacitance is changed by an applied voltage is used as the two capacitive elements C1 and C2, and the control voltage Vc is supplied from the control terminal 1 to the connection point of the two capacitive elements C1 and C2.

  With this configuration, the capacitance values of the two capacitive elements C1 and C2 change according to the voltage value supplied from the control terminal 1 to the connection point of the two capacitive elements C1 and C2, and the capacitive elements C1 and C2 And the resonance characteristic of the resonance circuit composed of the coil L1 changes, the oscillation frequency of the oscillation circuit changes, and the frequency of the oscillation signal obtained at the oscillation signal output terminals 2 and 3 changes. The oscillation signal Vout obtained at the oscillation signal output terminal 2 and the oscillation signal Vout ′ obtained at the oscillation signal output terminal 3 are signals having the same frequency and opposite phases.

Patent Document 1 describes an example of this type of oscillation circuit.
JP 2007-266700 A

  By the way, in the case of the configuration of the oscillation circuit shown in FIG. 8, the capacitance value is controlled by the voltage value of the control signal supplied from the outside to the control terminal 1 to control the output oscillation frequency. In order to obtain it, it is necessary to strictly control the voltage value, and a frequency resolution of about 0.01% with respect to the oscillation frequency is required, but since it is an analog voltage value, strict control is difficult. There is a problem that the configuration for obtaining a desired oscillation frequency is complicated. In order to obtain a desired frequency only by setting the capacitance value in the circuit of FIG. 7, it is necessary to set the capacitance value very delicately, in particular, in order to obtain an oscillation frequency required in a high frequency band such as the GHz band. This requires a small-capacitance capacitor that is difficult to realize in practice, resulting in an unrealistic circuit configuration.

  Conventionally, in order to obtain a desired frequency using such an oscillation circuit, a PLL circuit (phase locked loop circuit) incorporating this oscillation circuit is configured, and the output frequency is fed back and controlled. In general, the required frequency is obtained by multiplying or dividing the oscillation output, which complicates the configuration.

  An object of the present invention is to make it possible to control the oscillation frequency of an oscillation circuit with high resolution with a simple configuration.

In the oscillation circuit of the present invention, first and second distributed constant lines having a predetermined length are arranged substantially in parallel, one end of each of the first and second distributed constant lines is connected, and a predetermined point is connected to a connection point of the one end. Supply DC voltage or DC current. Then, one or a plurality of capacitive elements are connected between the middle of the first distributed constant line and the middle of the second distributed constant line.
Further, the first switching means is connected between the other end of the first distributed constant line and the ground potential portion, and the second switching constant line is connected between the other end of the second distributed constant line and the ground potential portion. 2 switching means are connected, the first switching means is controlled by a signal obtained at the other end of the second distributed constant line, and the second switching means is controlled at the other end of the first distributed constant line. It is configured to oscillate with the signal obtained. The oscillation signal is extracted from the other end of the first or second distributed constant line.

  According to the present invention, by preparing the first and second distributed constant lines and connecting the capacitive element in the middle thereof, the oscillation frequency can be controlled by setting the connection position of the capacitive element in the line. Become. Therefore, instead of the conventional voltage control, it is possible to set the oscillation frequency using the connection position of the capacitive element as a parameter, and strict oscillation frequency control different from the conventional voltage control is possible.

  For example, there is a configuration in which a plurality of capacitive elements having different connection positions are prepared, and the plurality of capacitive elements are selectively connected, so that the oscillation frequency can be varied by control to digitally select the capacitive elements to be connected. Thus, a desired oscillation frequency can be obtained with simple control.

Below, the example of embodiment of this invention is demonstrated using FIGS.
FIG. 1 is a diagram illustrating a basic configuration example of the oscillation circuit of the present embodiment. The configuration of FIG. 1 will be described. A first distributed constant line 11 and a second distributed constant line 12 each made of a conductive material having a predetermined length are prepared, and both distributed constant lines 11 and 12 are connected. They are arranged almost in parallel at a predetermined interval. Then, one end (hereinafter, this one end is referred to as a “short-circuit end”) 11a, 12a of both distributed constant lines 11, 12 is connected, and a predetermined DC power supply voltage VDD is supplied to the connection point. When the DC power supply voltage VDD is connected to the connection point, a current source 15 is connected as shown in FIG. 1 to supply a DC current from the current source 15. When the oscillation circuit of this example is configured as an integrated circuit, for example, the two distributed constant lines 11 and 12 are formed in a planar circuit formation direction of the integrated circuit (that is, a direction orthogonal to the thickness direction of the integrated circuit). ) In a straight line.

The other ends of the two distributed constant lines 11 and 12 (hereinafter referred to as “open ends”) 11b and 12b are not connected. Between the open ends 11b and 12b and the ground potential portion, An oscillation circuit in which two switching elements Q11 and Q12 are connected to each other is configured.
That is, the open end 11b of the first distributed constant line 11 is connected to the ground potential portion via the switching element Q11, and the open end 12b of the second distributed constant line 12 is connected to the ground potential portion via the switching element Q12. Connect to. The gate that is the control end of the switching element Q11 is connected to the open end 12b side of the second distributed constant line 12, and the gate that is the control end of the switching element Q12 is connected to the open end of the first distributed constant line 11. Connect to the 11b side. For example, MOS transistors are used as the switching elements Q11 and Q12.

  Then, the oscillation signal output terminal 13 is drawn out from the connection point between the open end 11b of the first distributed constant line 11 and the switching element Q11, and the oscillation signal output Vout is obtained at the output terminal 13. Further, the oscillation signal output terminal 14 is drawn out from the connection point between the open end 12b of the second distributed constant line 12 and the switching element Q12, and the oscillation signal output Vout ′ is obtained at the output terminal 14. The oscillation signal Vout obtained at the oscillation signal output terminal 13 and the oscillation signal Vout ′ obtained at the oscillation signal output terminal 14 are signals having the same frequency and opposite phases.

In this embodiment, one or a plurality of capacitors are connected between the first distributed constant line 11 and the second distributed constant line 12 arranged in parallel. In the example of FIG. 1, four capacitors C11, C12, C13, and C14 are arranged evenly at almost equal intervals. The capacitors C11 to C14 may be elements having the same capacitance value.
In the case of the transmission circuit of the present embodiment, the oscillation frequency in the oscillation circuit is determined by the arrangement positions of the capacitors C11 to C14 on the distributed constant lines 11 and 12 and the respective capacitance values. Therefore, for example, when four capacitors C11 to C14 are prepared as shown in FIG. 1, even if each capacitor has the same capacitance value, two distributions are provided for each capacitor C11, C12, C13, and C14. The oscillation frequency can be changed by setting the position where the constant lines 11 and 12 are connected.
In the above description, as shown in FIG. 1, the current source 15 is connected to the one ends 11a and 12a of the first and second distributed constant lines 11 and 12, but the first current source 15 is not provided. The DC voltage VDD may be directly supplied to the one ends 11a and 12a of the second distributed constant lines 11 and 12. However, the performance is better when the current source 15 is connected.

  Further, as shown in FIG. 2, a current source 16 is connected between the switching elements Q11, Q12 and the ground potential portion, and the supply path of the DC voltage VDD and the first and second distributed constant lines 11, It is good also as a structure which does not connect a current source between the one ends 11a and 12a of 12. The other parts of FIG. 2 are configured in the same manner as the circuit of FIG.

The point that the oscillation frequency can be set in the configuration shown in FIG. 1 and the configuration shown in FIG. 2 will be described below.
In the present embodiment, a phenomenon is used in which the sensitivity df _osc / dC causing the change in the oscillation frequency due to the change in the capacitance of the capacitor varies greatly depending on the position of the capacitance on the distributed constant line.
That is, when the oscillator oscillates, a standing wave is generated, and the voltage is maximum at the open ends of the distributed constant lines 11 and 12 and is minimum at the short-circuit ends. Therefore, if the capacitance is distributed on the distributed constant lines 11 and 12, the change in the oscillation frequency with respect to each capacitance change becomes the maximum when the capacitor is arranged at the open ends 11b and 12b, and the short-circuit ends 11a and 12a. This is the minimum when a capacitor is placed at the position.

FIG. 3 is a diagram showing the position dependency of the frequency change with respect to the capacitance change. The distance indicated by the horizontal axis in FIG. 3 indicates the distance from the open end of the distributed constant lines 11 and 12 in [mm], and the vertical axis indicates the frequency step [MHz]. In this example, the influence of the presence or absence of a capacitor having the same capacitance value on the change of the oscillation frequency is shown. As shown in FIG. 2, in the case of the capacitor provided at the position of the open end, it is possible to give an oscillation frequency change of about 400 MHz. On the other hand, it can be seen that the frequency change due to the presence or absence of the capacitor decreases as the position of the short-circuit end is approached.
Therefore, in the circuit configuration shown in FIG. 1 or FIG. 2, the frequency of the oscillation signal obtained at the output terminals 13 and 14 of this circuit can be set by setting the number and position of the capacitors connecting the two distributed constant lines 11 and 12. Can be set to a desired frequency.

FIG. 4 is a voltage waveform showing that a standing wave is generated when the oscillator oscillates, and that the voltage is maximum at the open end of the distributed constant lines 11 and 12 and is minimum at the short-circuited end. . In FIG. 4, the vertical axis represents voltage, and here, there is a voltage change from +2 V to −2 V, the horizontal axis represents time, and the voltage change with time. Furthermore, the depth direction in FIG. 4 is shown as a distance from the short-circuit end. In this example, the distance is shown up to 4 [mm].
As shown in FIG. 4, it can be seen that the voltage is maximum at the open end and minimum at the short-circuit end. In the present embodiment, this fact is utilized positively to change the oscillation frequency at the position of the capacitor on the distributed constant lines 11 and 12.

In order to obtain a desired oscillation frequency in the circuit of FIG. 1 or FIG. 2, a large frequency change is performed by controlling the capacitance provided near the open ends 11b and 12b of the distributed constant lines 11 and 12, and a small frequency change is The control is performed by controlling the capacitance provided at positions near the short-circuit ends 11a and 12a of the distributed constant lines 11 and 12. By doing so, a large variable resolution can be obtained, and high-resolution oscillation frequency control is possible.
Specifically, for example, even if all the four capacitors C11 to C14 shown in FIG. 1 or FIG. 2 have the same capacitance value, the output terminals 13 and 14 can be selected by selecting the positions to be connected to the distributed constant lines 11 and 12. The frequency of the oscillation signal obtained can be set to a necessary frequency. Of course, the oscillation frequency is selected by combining the proper setting of the capacitance values of the capacitors C11 to C14 and the selection of the positions where the capacitors C11 to C14 are connected to the distributed constant lines 11 and 12. Also good.

  Next, a configuration for varying the oscillation frequency in the oscillation circuit according to the embodiment of the present invention will be described with reference to FIGS. 5 and 6 show different examples. 5 and FIG. 6, the same reference numerals are given to the portions corresponding to FIG.

First, the configuration of FIG. 5 will be described. In this example, variable capacitance elements C21 to C28 are used as a configuration for changing the oscillation frequency.
That is, as shown in FIG. 5, the short-circuit end 11a of the first distributed constant line 11 and the short-circuit end 12a of the second distributed constant line 12 arranged in parallel are connected, and a DC power source is connected to the connection point. The current source 15 to which the voltage VDD is supplied is connected to supply the current from the current source 15. The switching elements Q11 and Q12 are connected between the short-circuit ends 11b and 12b of the first and second distributed constant lines 11 and 12 and the ground potential portion, and the gates of the respective switching elements Q11 and Q12 are connected. The oscillation circuit is configured by connecting to the short-circuited end 12b or 11b side of the other distributed constant line.

In the example of FIG. 5, between the two distributed constant lines 11 and 12, a series circuit of two variable capacitance elements C21 and C22, a series circuit of two variable capacitance elements C23 and C24, and two Are connected to a series circuit of the variable capacitance elements C25 and C26 and a series circuit of two variable capacitance elements C27 and C28. The control signals V11, V12, V13, and V14 obtained from the control signal input terminals 21, 22, 23, and 24 are supplied to the connection points of the four series circuits.
As each of the variable capacitance elements C21 to C28, here, a varactor whose capacitance value is controlled by a voltage value is used. Depending on the voltage value of each control signal V11, V12, V13, V14, four variable capacitance elements The capacitance value of the series circuit is controlled.

The setting of the position where the series circuit of the four variable capacitance elements is connected to the distributed constant lines 11 and 12 is as already described in the configuration of FIG. That is, the change of the oscillation frequency with respect to the capacitance change is maximized when a capacitor is disposed at the positions of the open ends 11b and 12b, and is minimized when the capacitor is disposed at the positions of the short-circuit ends 11a and 12a. The arrangement is such that a desired oscillation frequency can be obtained.
Then, by controlling the voltage values of the control signals V11, V12, V13, and V14 obtained at the control signal input terminals 21, 22, 23, and 24, they are obtained at the output terminals 13 and 14 in the circuit configuration of FIG. The oscillation frequencies Vout and Vout ′ can be varied. The voltage values of the control signals V11, V12, V13, and V14 may be varied in an analog manner. A configuration may be selected from among them.

In the example of FIG. 5, an example is provided in which a series circuit of four variable capacitance elements is provided. However, according to the variable range of the frequency that needs to be taken out from the output terminal 13 or 14, an arbitrary number of plural plural capacitance elements can be obtained from one series circuit. A series circuit can be selected as appropriate. In this case, as a capacitive element for connecting the two distributed constant lines 11 and 12, not all of the elements are constituted by variable capacitive elements, but some of the elements are capacitors whose capacitance values are determined as in the example of FIG. It is good.
Also in the example of FIG. 5, the current source 16 may be connected to the ground side as shown in FIG. 2 instead of the current source 15.

Next, the example of FIG. 6 will be described. Between two distributed constant lines 11 and 12, a series circuit of two capacitors C31 and C32 and a switch S11, a series circuit of two capacitors C33 and C33 and a switch S12, and two capacitors C35 , C36 and a switch S13 and a series circuit of two capacitors C37 and C38 and a switch S14 are connected. However, each of the switches S11, S12, S13, S14 is connected between two capacitors in the example of FIG.
And opening / closing of each switch S11, S12, S13, S14 is controlled by the control signals V21, V22, V23, V24 obtained at the control signal input terminals 31, 32, 33, 34. For example, semiconductor switches are used as the switches S11, S12, S13, and S14.

The setting of the position where the series circuit of four capacitors and switches is connected to the distributed constant lines 11 and 12 is as already described in the configuration of FIG. That is, the change of the oscillation frequency with respect to the capacitance change is maximized when a capacitor is disposed at the positions of the open ends 11b and 12b, and is minimized when the capacitor is disposed at the positions of the short-circuit ends 11a and 12a. The arrangement is such that a desired oscillation frequency can be obtained.
Then, by controlling the opening and closing of each switch individually by the control signals V21, V22, V23, and V24 obtained at the control signal input terminals 31, 32, 33, and 34, the output terminal 13 has the circuit configuration of FIG. , 14 can be varied in the oscillation frequencies Vout and Vout ′. Since the control based on the signals obtained for the control signals V21, V22, V23, and V24 is merely to open or close the switch, for example, one of two values of high level “H” and low level “L”. The structure which supplies these selectively may be sufficient. By adopting a configuration in which the capacitance is switched by the semiconductor switch in this way, the semiconductor switch configured by a transistor or the like is configured to be controlled by voltage, is not current-type control, the switch resistance can be ignored, and the capacitance can be improved. To be able to control.

In the example of FIG. 6, an example in which a series circuit of four capacitors and switches is provided is provided. However, according to a variable range of the frequency that needs to be taken out from the output terminal 13 or 14, an arbitrary plurality of plural circuits are provided from one series circuit. A series circuit can be selected as appropriate. In this case, as a capacitor for connecting the two distributed constant lines 11 and 12, not all capacitors are connected in series with the switch, but some elements are not provided with a switch as in the example of FIG. It is good also as a structure directly connected with two distributed constant lines.
Also in the example of FIG. 6, the current source 16 may be connected to the ground potential side as shown in FIG. 2 instead of the current source 15.

  FIG. 7 shows the capacitance position on the line, the change in oscillation frequency (FIG. 7A), and the change in frequency step (FIG. 7B) in the configuration of FIGS. . In both FIG. 7A and FIG. 7B, the horizontal axis indicates the distance [mm] from the open end to the position where the capacitor is connected, and the vertical axis in FIG. 7A is the output oscillation frequency. In this example, it is shown that the position where the capacitors having the same capacitance value are connected is changed on the lines 11 and 12 to change from about 8.8 GHz to 9.8 GHz. Further, as shown in FIG. 7B, it can be seen that the frequency step is freely changed from 400 MHz step to 0 MHz depending on the connection position of the capacitors having the same capacitance value.

  As can be seen from FIG. 7, not only can the oscillation frequency be greatly changed by changing the position where capacitors having the same capacitance value are connected on the line, but also the connection of capacitors or variable capacitance elements arranged closer to the short-circuit end side. By adopting the control configuration, it is possible to control a very small oscillation frequency, and it is possible to easily perform a switch from a large frequency change to a small frequency change by setting a switch voltage or a control voltage of a varactor. Therefore, even when a circuit is constructed using a capacitor having a practically realizable capacitance value, the variable range of the oscillation frequency can be increased, and high-resolution oscillator frequency control can be performed. Further, unlike the conventional oscillation circuit, frequency control can be performed by digital control, and the control configuration is simplified.

  In the above-described embodiment, the varactor is used as the variable capacitance element. However, other variable capacitance elements may be used. Further, the values of the oscillation frequency and the frequency step shown in FIGS. 3, 4, and 7 are examples, and are not limited to these values.

It is a block diagram which shows the example of a basic composition of the oscillation circuit of one embodiment of this invention. FIG. 2 is a configuration diagram illustrating an example in which a connection position of a current source of the oscillation circuit of FIG. 1 is changed. It is the characteristic view which showed the example of the position dependence with respect to the capacity | capacitance change in one embodiment of this invention. It is the characteristic view which showed the example of the relationship between the position in one embodiment of this invention, time, and voltage. It is a block diagram which shows the example (Example 1) of the oscillation circuit of one embodiment of this invention. It is a block diagram which shows the example (Example 2) of the oscillation circuit of one embodiment of this invention. It is a characteristic view which shows the variable characteristic example of the oscillation frequency in one embodiment of this invention. It is a block diagram which shows an example of the conventional oscillation circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... 1st distributed constant line, 11a ... Short-circuit end, 11b ... Open end, 12 ... 2nd distributed constant line, 12a ... Short-circuit end, 12b ... Open end, 13, 14 ... Oscillation signal output terminal, 15, 16 ... Current source, 21-24, 31-34 ... Control signal input terminal, C11-C14 ... Capacitor, C21-C28 ... Capacitance variable element, C31-C38 ... Capacitor, Q11, Q12 ... Switching element, S11-S14 ... Switch

Claims (5)

First and second distributed constant lines having a predetermined length are arranged substantially in parallel, one end of each of the first and second distributed constant lines is connected, and a predetermined DC voltage or DC current is supplied to a connection point of the one end. And
Connecting one or more capacitive elements between the middle of the first distributed constant line and the middle of the second distributed constant line;
A first switching means is connected between the other end of the first distributed constant line and the ground potential portion, and a second switching device is connected between the other end of the second distributed constant line and the ground potential portion. Connecting two switching means,
The first switching means is controlled by a signal obtained at the other end of the second distributed constant line, and the second switching means is controlled by a signal obtained at the other end of the first distributed constant line. Done
An oscillation circuit characterized in that an oscillation signal is extracted from the other end of the first or second distributed constant line. The oscillation circuit according to claim 1,
An oscillation circuit, wherein the frequency of the oscillation signal is controlled by setting a position where the capacitive element is connected on the first and second distributed constant lines. The oscillation circuit according to claim 1 or 2,
Providing a selection means for selectively connecting the one or more capacitive elements to the first and second distributed constant lines;
An oscillation circuit characterized in that the frequency of the oscillation signal is made variable by selection of a capacitive element connected to the first and second distributed constant lines by the selection means. The oscillation circuit according to claim 3, wherein
An oscillation circuit characterized in that the selection means is constituted by switching means. The oscillation circuit according to claim 3, wherein
As the capacitive element, a capacitive variable element whose capacitance value is controlled,
The oscillation circuit according to claim 1, wherein the selection means is means for selectively changing a capacitance of the capacitance variable element.

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