JP2003017936A - Voltage-controlled oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage-controlled oscillator that can easily cope with a high frequency tendency of the oscillation frequency and select the frequency band. SOLUTION: The voltage-controlled oscillator comprises a resonance circuit section X including a resonance circuit comprising a strip line 7, a variable capacitance diode 3, and capacitors 4, 5 and for applying an external voltage to the variable capacitance diode 3 to control the resonance frequency, a negative resistance circuit section Y including an oscillation TR 1, and an amplifier circuit section Z including an amplifier TR 2. One-side terminals of the strip line 7, the variable capacitance diode 3 and the capacitor 5 are connected in parallel to be a ground level and a switching diode 6 supplying a control signal to select the resonance frequency band is placed between the capacitor 5 and a point of the ground level.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a mobile communication device such as a dual / triple mode mobile phone.
The present invention relates to a voltage controlled oscillator having an oscillation frequency switching function. 2. Description of the Related Art In mobile band communication equipment, there is an increasing demand for smaller, lighter, thinner, and lower-voltage terminals, and a voltage-controlled oscillator provided with a voltage-controlled oscillation circuit mounted therein. However, there is a growing demand for lighter, smaller, and more cost-effective products. In addition, with the diversification of communication systems, a circuit configuration has been proposed for a voltage-controlled oscillator that outputs two different oscillation frequency bands, in which the circuit scale is reduced and the number of components is reduced. As shown in the partial block circuit diagram of FIG. 2, the voltage controlled oscillator includes a resonance circuit including a strip line, a variable capacitance diode, and a capacitor. A resonance circuit section X for controlling the frequency, a negative resistance circuit section Y including an oscillation transistor for outputting an oscillation signal based on the resonance frequency of the resonance circuit section, and an amplification circuit section including an amplification transistor for amplifying the oscillation signal Z. Conventionally, a circuit configuration of a voltage controlled oscillator that outputs a different oscillation frequency band is such that the resonance circuit portion X of the above-described respective circuit portions is configured as shown in FIG. 4 and can be switched to a predetermined resonance frequency band. Was like that. More specifically, considering the two resonance frequencies,
The line is divided into lines 16 and 17, a switching diode 18 is connected between the division point and the ground potential, and the switching diode 18 is ON / OFF controlled. That is, when the switching diode 18 is in the OFF state, the inductance component of the resonance circuit (consisting of the variable capacitance diode 3, the capacitors 4, 15 and the strip lines 16, 17) corresponds to the total length of the two lines 16, 17. Based on the relatively low resonance frequency corresponding to the resonance frequency, the oscillation output is in a low frequency band. Also, the switching diode 18 is ON
In this state, the parallel circuit of the parasitic inductor of the strip line 17 and the switching diode 18 and the series circuit of the strip line 16 constitute an inductor component, so that the combined inductor becomes small and the resonance frequency of the resonator increases. This results in an oscillation output in a high frequency band. In FIG. 4, a resistor 19 is a bias resistor for setting a bias voltage. However, when a voltage controlled oscillator corresponding to a high frequency whose resonance frequency exceeds 1 GHz is constructed, the strip line 16, strip line 17, which is a λ / 4 resonance element, and It is necessary to reduce the combined inductance of the switching diode 18 due to the parasitic inductor component. However, since the parasitic inductor component of the switching diode 18, which is a switching element, is fixed due to the structure of the circuit board on which the switching diode is mounted, the minimum value of the combined inductor is limited, and it is difficult to cope with higher frequencies. Become. For example, a parallel resonance circuit is formed by the combined capacitance of the variable capacitance diode 3, the capacitance correcting capacitor 4 and the capacitor 5, and the combined inductance of the two strip lines 16 and 17. In such a circuit, when the switching diode 18 is turned off, the inductance of the parallel resonance circuit is a combined inductance of the strip line 16 and the strip line 17. Further, the switching diode 18 is turned on.
In this case, the inductance component of the parallel resonance circuit becomes the combined inductance of the parasitic inductor components of the strip line 16, the strip line 17, and the switching diode 18. At this time, since the parasitic inductance of the switching diode 18 is sufficiently small at about 1 nH when the frequency is 1 to 2 GHz, the combined inductance of the parasitic inductance components of the strip line 17 and the switching diode 18 is A sufficiently small value depends on the parasitic inductor component. Therefore, the combined inductance of the parasitic inductance components of the strip line 16, the strip line 17, and the switching diode 18, which is the inductance of the parallel resonance circuit, depends on the strip line 16, and is smaller than when the switching diode 18 is OFF. When a high-frequency resonance circuit of about 2 GHz is formed, if the combined capacitance of the variable capacitance diode 3, the capacitance correcting capacitor 4 and the capacitor 5 is about 4 pF, the interactor becomes 1.58 nH. Since there are 18 parasitic inductors of about 1 nH, the inductance value of the strip line 16 needs to be a small value of 0.58 nH or less. However, in reality, it is practically impossible to reduce the inductance value of the strip line 16 to a very small value of 0.58 nH or less, and there has been a problem that higher frequencies cannot be realized. The present invention has been devised in view of the above problems, and has as its object to provide a voltage controlled oscillator which can easily cope with an increase in the oscillation frequency and can switch the frequency band. Is to do. According to the present invention, there is provided a resonance circuit including a resonance circuit including a strip line, a variable capacitance diode, and a capacitor, wherein an external voltage is supplied to the variable capacitance diode to control a resonance frequency. A voltage-controlled oscillator comprising: a negative resistance circuit section including an oscillation transistor that outputs an oscillation signal based on a resonance frequency of the resonance circuit section; and an amplification circuit section including a transistor that amplifies the oscillation signal. One end of the line, the variable capacitance diode, and one end of the capacitor are connected in parallel with each other so as to be at the ground potential, and between the capacitor and the ground potential, the anode side is connected to the capacitor, the cathode side is grounded, and the resonance frequency is connected to the anode side. A switching diode to which a control signal for switching the band is supplied A voltage-controlled oscillator characterized in that: According to the present invention, the switching diode is O
In the N state, a resonance circuit is formed by a variable capacitor, a capacitor, and a strip line, and an oscillation output is output based on a resonance frequency in a low frequency band. At this time, the parasitic inductor due to the switching diode is ignored because it is connected in series with the capacitor and connected in parallel with the strip line. When the switching diode is OFF, a small parasitic capacitance component of the switching diode and a series combined capacitance of the capacitor 14 are formed. However, the combined capacitance is smaller than when the switching diode is ON, and the VCO has a high frequency. Output band signal. Also, when the switching diode is in the ON state, the resonance circuit is switched for the low frequency band as described above. However, the capacitor connected in parallel to the strip line that is the resonance element is compared with the case where the switching diode is in the OFF state. Because it is big,
The control voltage sensitivity is smaller than in the high frequency band. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a voltage controlled oscillator according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a high-frequency component incorporating the voltage-controlled oscillator of the present invention. That is, the high-frequency component is formed on the multilayer circuit board integrally with the circuit other than the voltage-controlled oscillator, for example, the receiving circuit of the communication circuit. FIG.
In addition, on the surface of the multi-layer substrate 20, in addition to the predetermined surface wiring pattern, mounted are components 21 such as switching diodes, varicap diodes, and resistors that cannot be mounted in the multi-layer substrate, such as voltage-controlled oscillators and other circuits. . In addition, in the multilayer substrate 20, in addition to the internal wiring pattern, a capacitor electrode constituting various capacitors, a strip line serving as an inductor conductor, and a ground potential conductor film are formed. Note that a strip line or the like serving as an inductor conductor may be formed on the surface of the multilayer substrate 20. On the end face of such a multilayer substrate, terminal electrodes 22 serving as terminals of various circuits are formed. The voltage controlled oscillator formed on such a multilayer circuit board has a configuration shown in a partial block circuit diagram as shown in FIG. The resonance circuit section X which is a block circuit section in FIG. 2 has a circuit configuration shown in FIG. In FIG. 2, X is a resonance circuit, and Y
Is a negative resistance circuit section, and Z is an amplifier circuit section. 3 includes a strip line 7 serving as a resonance unit, a variable capacitance diode 3, a capacitor 1,
4 and 5, an inductor element 2, a switching diode 6, and a resistor 8. The negative resistance circuit section Y includes an oscillation transistor Tr1, various capacitors C5 to C7, and various resistors R1 to R7.
And 3. The amplifier circuit section Z includes an amplifying transistor Tr2, various capacitors C8 to C11, various resistors R4,
And an inductance element L2. In such an oscillating circuit, if the collector of the oscillating transistor Tr1 of the negative resistance circuit portion Y is grounded at a high frequency, the impedance seen from the base becomes negative, and the oscillating transistor Tr1 has a negative impedance. If the resonance circuit part X is connected to the resonance circuit via the coupling capacitor 10 and the other end is grounded, this circuit has the amplitude characteristic of the resonance circuit part X and the negative gain of the transistor of 1 or more, and the negative circuit of the resonance circuit and the transistor. Oscillate at a frequency that satisfies the condition that the sum of the phase angles of the sexes is 2nπ (n is an integer). Then, this oscillation signal is supplied to the amplification transistor Tr2, where it is amplified and oscillated and output from the output pin OUT. In the resonance circuit section X, the terminal VT is an external control voltage terminal. Further, a control voltage for controlling the capacitance component of the variable capacitance diode 3 is supplied to the external control voltage terminal VT. That is, by controlling the control voltage applied to the variable capacitance diode 3 to a predetermined value, the capacitance component of the variable capacitance diode 3 is further added to the LC resonance circuit including the strip line 7 and the capacitors 4 and 5. And the resonance frequency of the resonance circuit section X can be controlled to a predetermined value. The terminal ctl is a control terminal to which a signal for switching the resonance frequency of the resonance circuit to a predetermined frequency band is supplied. From this control terminal,
The bias voltage supplied to the switching diode 6 is applied. The specific structure of the resonance circuit section X is such that one end of the strip line 7 is connected to the capacitor 10 side and connected to the negative resistance circuit section Y, and is variable via one end of the capacitor 5 and the capacitor 4. Connected to the cathode of capacitance diode 3. The other end is grounded to the ground potential. In addition, capacitor 5, variable capacitance diode 3
Are connected to the strip line 7 in parallel. As described above, the cathode of the variable capacitance diode 3 is directly connected to the external control voltage terminal VT, and the anode is grounded to the ground potential. Thereby, the capacitance of the variable capacitance diode DV can be changed.
A switching diode 6 is arranged between the capacitor 5 and the ground potential. The switching diode 6 has an anode connected to the capacitor 5 and a cathode connected to the ground potential. Also, the anode of the switching diode 6 is connected via a resistor 8 to:
A bias voltage is supplied from the control terminal ctl. In the present invention, in the resonance circuit section X, the resonance circuit that determines the resonance frequency is composed of the combined capacitance of the variable capacitance diode 3, the capacitance correction capacitor 4 and the capacitor 5, and the inductance component of the strip line 7. It is composed of a parallel resonance circuit. Here, when the DC voltage applied to the external control voltage terminal VT changes, the DC voltage is applied to the variable capacitance diode 3, the reverse bias changes, and the capacitance value of the variable capacitance diode 3 changes. As a result, the capacitance component of the above-described parallel resonance circuit changes, and the resonance frequency changes. This is adjustment of the resonance frequency in a predetermined resonance frequency band. When a low-level signal (a signal for turning off the switching element) is input to the control terminal ctl for switching the resonance frequency band, the switching diode 6 which is a switching element connected in series with the bias resistor 8 is connected. Becomes OFF. For example, when the resonance frequency is about 1 GHz to 3 GHz, when the switching diode 6 is OFF, the combined capacitance of the capacitor 5 and the switching diode 6 is smaller than 1 pF because the capacitance has about 1 pF. When a high-level signal (a signal for turning on the switching element) is input to the control terminal ctl for switching the resonance frequency band, the switching diode 6 connected in series to the bias resistor 8
N. For example, when the resonance frequency is about 1 GHz to 3 GHz, about 1 n
Although it has an inductor of about H, this value is very small and can be ignored. As a result, the combined capacitance of the capacitor 5 and the switching diode 6 becomes almost the same as the capacitance value of the capacitor 5. With such an operation, the combined capacitance of the capacitor 5 and the switching diode 6 when the switching diode 6 is ON is larger than that when the switching diode 6 is OFF. The resonance frequency of the circuit is lower than when the switching diode 6 is off. Therefore, the oscillation frequency of the voltage controlled oscillator is
When the switching diode 6 is ON, the voltage is lower than when the switching diode 6 is OFF. For example, when the resonance circuit portion X is constituted by a resonance circuit of about 2 GHz exceeding 1 GHz, the combined capacitance of the variable capacitance diode 3, the capacitance correcting capacitor 4 and the capacitor 5 is changed from 4 pF to about 3 pF, and the inductor is changed. 1GHz because the circuit can be configured at 1.58nH
It is possible to switch the resonance frequency exceeding the above, and it is possible to easily cope with a higher frequency. Although the strip line 7 is used as the inductor conductor in the above-described embodiment, a coil pattern may be formed inside the multilayer substrate, or a microstrip line or a coil pattern may be formed on the surface of the multilayer substrate. May be formed. As described above, according to the present invention, there is no need to divide and arrange a strip line, and a small voltage controlled oscillator can be obtained. In addition, even if a voltage controlled oscillator having a resonance frequency in a high frequency region exceeding 1 GHz is configured, it is not necessary to set the intactor component of the resonance circuit to a very small value, and the voltage controlled oscillator is compatible with a higher frequency. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external perspective view of a multilayer circuit board including a voltage controlled oscillator according to the present invention. FIG. 2 is a partial block circuit diagram of a typical voltage controlled oscillator. FIG. 3 is a circuit diagram of a resonance circuit unit used in the voltage controlled oscillator of the present invention. FIG. 4 is a circuit diagram of a resonance circuit unit used in a conventional voltage controlled oscillator. [Description of Signs] X Resonance circuit section Y Negative resistance circuit section Z Amplification circuit section 7 Strip line 6 Switching diode

Claims (1)

Claims: 1. A resonance circuit section including a resonance circuit including a stripline, a variable capacitance diode, and a capacitor, for supplying an external voltage to the variable capacitance diode to control a resonance frequency, and a resonance circuit. A voltage-controlled oscillator comprising: a negative resistance circuit section including an oscillation transistor for outputting an oscillation signal based on a resonance frequency of the section; and an amplification circuit section including an amplification transistor for amplifying the oscillation signal. One end of the capacitive diode and one end of the capacitor are connected in parallel to each other so as to be at the ground potential, and between the capacitor and the ground potential, the anode side is connected to the capacitor, the cathode side is connected to the ground, and the resonance frequency band is connected to the anode side. A switching diode to which a control signal for switching is supplied Voltage controlled oscillator according to claim.