JP2003046333A - Frequency shift type of high frequency voltage- controlled oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency shift type of high frequency voltage-controlled oscillation circuit with less output level fluctuations. SOLUTION: The voltage-controlled oscillator includes; a resonance circuit section X that includes a strip line SL3, first and second varactor diodes DvDV2 and capacitors and that controls the resonance frequency by first and second control voltages applied to the first varactor diode DV and the second varactor diode DV2; a negative resistance circuit section Y that includes an oscillation transistor(Tr)1 to output an oscillation signal; and an amplifier circuit section Z that includes an amplifier Tr2. The anode of the first varactor diode DV is connected to ground, the cathode is connected to one terminal of the strip line SL3, and the other terminal of the strip line SL3 is connected to the negative resistance circuit section Y via a capacitor C21, the second varactor diode DV2, and a coupling capacitor C4 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency shift type high frequency voltage controlled oscillator circuit capable of switching oscillation frequencies in a plurality of types of frequency bands.

[0002]

2. Description of the Related Art Conventionally, it has been known that a voltage controlled oscillator is used as a transmission oscillator of a mobile communication device or other communication devices and a local oscillator of a reception unit. Although mobile communication devices in the world are divided into several systems, the number of mobile communication devices compatible with dual systems and triple systems is increasing with the progress of world horns. However, the multi-systemization increases the number of parts accordingly, and the problems of "increasing volume" and "increasing cost" cannot be avoided. Mobile communication device manufacturers are considering to solve the problem. Currently, the "direct conversion method" is becoming the mainstream as one of the solutions.
This is the conventional method called "superheterodyne" in the communication system of mobile communication devices, in which the received wave is dropped to an intermediate frequency in the receiving circuit and then converted into an audio signal. It is a method of converting into a signal. With the development of baseband ICs, that method has become possible. This makes it possible to reduce parts. In addition, this method has a great effect on a circuit compatible with multi-system. This "direct conversion method" is
With regard to the voltage controlled oscillator, one transmitting and receiving oscillator is sufficient, which is more effective. In the case of multi-system, the voltage controlled oscillator used in the “direct conversion method” is in a high frequency region in the voltage controlled oscillator, and for example, the voltage controlled oscillator in the “3 GHz band” is becoming the mainstream.

However, in addition to the high frequency, this voltage controlled oscillator has a very wide frequency range and requires about 400 MHz. This is a case where dual system is taken as an example, and when the number is triple or more, the frequency range is further expanded, and the control voltage sensitivity for controlling the oscillation frequency of the voltage controlled oscillator is becoming higher. When this control voltage sensitivity becomes high, it becomes very difficult to design the PLL circuit around the voltage controlled oscillator that locks the frequency. Since the sensitivity is very high, it takes a very long time to lock the frequency, which causes a problem on the terminal, and the range of the control voltage sensitivity supported by the PLL-IC is limited. Absent. In order to form a stable PLL circuit while covering the frequency range in this way and to set the frequency control sensitivity low, a high frequency voltage controlled oscillator having a frequency shift function is required.

First, a general oscillation circuit, for example, a voltage controlled oscillation circuit will be described with reference to FIG. A resonance circuit unit X including a resonance circuit composed of a strip line SL, a variable capacitance diode DV, and capacitors C2 and C3, and supplying an external control voltage VT to the variable capacitance diode DV to control the resonance frequency, and a resonance circuit unit X. An oscillation transistor Tr1 that outputs an oscillation signal based on the resonance frequency of the resistors, resistors R1 and R2,
A negative resistance circuit section Y including capacitors C5 to C7, an amplification transistor Tr2 for amplifying an oscillation signal, a resistance R3,
It is composed of capacitors C8 to C11 and an amplifier circuit section Z including an inductance element L2.

In such an oscillating circuit, if the collector of the oscillating transistor Tr1 of the negative resistance circuit section Y is grounded at high frequency, the impedance seen from the base becomes negative, and the oscillating transistor Tr1 has a negative impedance. If the resonance circuit section X is connected to the capacitor via the coupling capacitor C4 and the other end is grounded, this circuit has the amplitude characteristics of the resonance circuit section X and the negative gain of the transistor of 1 or more, and the resonance circuit and the transistor have a negative polarity. It oscillates at a frequency that satisfies the condition that the sum of the sex phase angles is 2nπ (n is an integer). Then, this oscillation signal is supplied to the amplifying transistor Tr2, is amplified here, and is oscillated and output from the output element OUT.

In this voltage controlled oscillator circuit, the resonance frequency within the variable range of the variable capacitance diode DV, and thus the oscillation frequency, can be controlled within a predetermined range.

In order to obtain two kinds of oscillation outputs of the oscillation frequency of such a voltage controlled oscillation circuit and to widen the frequency variable range of the oscillation output, the inductance component and the capacitance component of the resonance circuit can be changed stepwise. Proposed.

FIG. 4 shows a resonant circuit portion of the voltage controlled oscillator circuit shown in FIG. 3 provided with a shift circuit for switching the resonant frequency. This is an example in which the strip line SL shown in FIG. 3 is divided into two and a switching diode Dz is connected. That is, the strip line SL is divided into two strip lines SL1 and SL2, and the switching diode Dz is connected to the connection point via the DC limiting capacitor CS. The anode of the switching diode Dz is connected via the DC limiting capacitor Cs, and is also connected to the shift terminal VS to which the shift voltage signal is supplied via the bias resistor Rs.

In FIG. 6, the switching diode Dz is turned on / off by the shift voltage signal. As a result, the electrical length of the strip line SL becomes equal to that of the strip line S.
There are a case where L1 (the switching diode Dz is in the ON state) and a case where the strip lines SL1 and SL2 are combined (the switching diode Dz is in the OFF state). That is, the inductance component of the LC resonance circuit is switched to perform the stepwise control of the resonance frequency.

Further, FIG. 5 shows a variable capacitance diode DV.
The resonance circuit section X of the high-frequency voltage controlled oscillation circuit applied when the oscillation output is equal to or higher than the self-resonance frequency, for example, 3 GHz or higher. In this resonant circuit, a variable capacitance diode DV that operates inductively and strip lines SL3 and L4 are connected in series, and a capacitor C3 is connected between one end of the strip line SL3 and the ground potential. .

In such an oscillator circuit, the switching diode Dz is connected in parallel with the strip line SL4, and the shift voltage VS is supplied to the anode of the switching diode Dz.

ON / OFF of this switching diode Dz
Switching diode Dz turns on by turning off
The operation becomes inductive, and an inductance component is added to the strip line SL4. As a result, the inductance component of the resonance circuit largely changes, and the resonance frequency can be switched.

[0013]

In the frequency shift type high frequency voltage controlled oscillator, the biggest problem is that deviation occurs in each oscillation output characteristic in the oscillation frequency band before and after the frequency shift. For example, it is desirable that the oscillation outputs have the same characteristics in the frequency band, but it is very difficult to output the same characteristics due to the influence of the shift circuit.

Further, the characteristics may be slightly changed due to the difference in the formation of the strip line or the like which constitutes the oscillation circuit, for example, the displacement of the line or the bleeding of the conductive paste. Generally, this fluctuation is corrected by providing a stub conductor on the strip line and performing laser trimming or the like. Further, when an oscillation circuit having a slightly different frequency band of the oscillation frequency is required, it is necessary to review the circuit constant of the oscillation circuit according to the required characteristics each time.

The present invention has been devised in view of the above problems, and an object thereof is that there is no difference in characteristics between a plurality of frequency bands of oscillation output, and that there is no fluctuation in characteristics due to differences in constituent parts. It is an object of the present invention to provide a frequency shift type high frequency voltage controlled oscillator circuit that can be easily adjusted.

[0016]

The present invention comprises a strip line and first and second variable capacitance diodes and capacitors, wherein the first variable capacitance diode and the second variable capacitance diode are provided.
Negative resistance circuit section including a resonance circuit section for controlling the resonance frequency by the first and second control voltages supplied to the variable capacitance diode, and an oscillation transistor for outputting an oscillation signal based on the resonance frequency of the resonance circuit section. And an amplifier circuit section including a transistor for amplifying an oscillation signal, wherein the anode side of the first variable capacitance diode is grounded and the cathode side is at one end of the strip line. In addition to being connected, the other end of the strip line is a frequency shift type high frequency voltage controlled oscillator circuit characterized in that it is connected to a negative resistance circuit section via a capacitor, a second variable capacitance diode, and a coupling capacitor. .

Further, a bias voltage is applied to the anode of the second variable capacitance diode, a cathode is grounded via a capacitor, and a frequency shift type high frequency voltage controlled oscillator circuit to which a second control voltage is applied. Is.

In the present invention, both the first variable capacitance diode and the second variable capacitance diode operate inductively in the high frequency region which is the oscillation frequency.

Therefore, the inductance component of the resonance circuit is a combination of the inductance component of the first variable capacitance diode, the inductance component of the strip line and the inductance component of the second variable capacitance diode. Further, the capacitance component of the resonance circuit becomes the capacitance component of the capacitor between the cathode of the second variable capacitance diode and the ground potential.

Therefore, the inductance component of the first variable capacitance diode can be arbitrarily adjusted, for example, continuously adjusted by the first control voltage supplied to the first variable capacitance diode.

The inductance component of the second variable capacitance diode can be arbitrarily adjusted, for example, intermittently adjusted by the second control voltage (shift voltage) supplied to the second variable capacitance diode. Here, a bias voltage of a constant voltage is always applied to the anode of the second variable capacitance diode in the oscillating operation state, and the second control voltage is applied to the cathode side. . That is, the inductance component of the second variable capacitance diode is determined by the potential difference between the bias voltage and the second control voltage.

By supplying a bias voltage of a constant voltage and switching the second control voltage to a stepwise voltage, the potential difference changes stepwise, and as a result, the inductance component of the resonance circuit changes stepwise. The oscillating frequency can be switched stepwise (shift).

Further, a first variable capacitance diode, a strip line, and a second variable capacitance diode which form an inductor component of the resonance circuit are connected in series, and their impedance components are the first and second impedance components. Independent of the operation of the variable capacitance diode.

Therefore, in the oscillation characteristics before and after the shift of the oscillation frequency, the difference in the output level hardly occurs.

Further, in the present invention, the inductance component of the strip line, which constitutes the inductance component of the resonance circuit, may slightly vary from the design value in forming the strip line. In addition, the required characteristics of the oscillation frequency may change.

In such a case, in particular, in the second variable capacitance diode, a voltage obtained by finely adjusting the value of the second control voltage from a predetermined value is used. As a result, it is possible to very easily cope with the fluctuation due to the formation of the strip line and the change of the oscillation frequency, and the shape of the strip line is greatly simplified.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The frequency shift type high frequency voltage controlled oscillator circuit of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a high frequency component incorporating the frequency shift type high frequency voltage controlled oscillator circuit of the present invention. That is,
In the high frequency component, in addition to the frequency shift type high frequency voltage controlled oscillation circuit, for example, a reception circuit of a communication circuit, a transmission circuit of the communication circuit, an antenna switch circuit, various filter parts, etc. are formed inside and on the surface of the multilayer circuit board. In FIG.
On the surface of the multilayer substrate 10, in addition to the predetermined surface wiring pattern 11 including an inductor conductor and a strip line, circuit components 12 such as a switching diode, a varicap diode, and a resistor that form a voltage controlled oscillator and other circuits are formed. Although not shown, inside the multilayer substrate, in addition to the internal wiring pattern and via-hole conductors, strip lines, microstrip lines, and ground potential conductor films that serve as capacitance electrodes and inductor conductors forming various capacitors are formed. .

On the end face of such a multi-layer substrate 10, terminal electrodes 13 which are terminals of various circuits are formed. The terminal electrode 13 includes a power supply voltage terminal, a ground potential terminal, a control voltage terminal, a shift control signal terminal, and the like.
It should be noted that various circuits formed on the multilayer substrate 1 and connection of each circuit in the multilayer substrate add, for example, an antenna terminal electrode, a reception signal output terminal, a transmission signal input terminal, and the like.

The frequency shift type high frequency voltage controlled oscillator formed on such a multilayer circuit board 10 has a circuit as shown in FIG.

The frequency shift type high frequency voltage controlled oscillator circuit of FIG. 2 is a high frequency voltage controlled oscillator circuit which can be used by a direc-conversion type IC as a control IC of a receiving circuit.
Then, the oscillation output is, for example, 3.6 GHz and 3.7 GHz at the center frequency so that a wide range of frequencies can be changed.
The two resonance frequencies are shifted, and a part of each frequency band is overlapped with each other. For example, 1
± 200MHz from the center frequency of one resonance frequency
If it is possible to change with,
Oscillation frequencies of up to 3.9 GHz are possible.

In FIG. 2, X is a resonance circuit section, and Y
Is a negative resistance circuit section, and Z is an amplifier circuit section.

The resonant circuit section X includes a strip line SL3, a first variable capacitance diode DV that operates inductively, a second variable capacitance diode DV2, and a capacitor C.
1 to C4, C21, an inductor element L, a bias voltage resistor RS, and resistors R10 and R11.
A control voltage terminal VT to which an external first control voltage supplied to the first variable capacitance diode DV3 is input, and a second control voltage (shift voltage VS) supplied to the second variable capacitance diode DV2 are supplied. A shift terminal VS. For the sake of convenience, the respective voltages and terminals are given the same reference numerals.

In the resonance circuit section X, the shift circuit is composed of a capacitor C21, a second variable capacitance diode DV2, a resistor RS, and resistors R10 and R11. still,
The capacitor C3 serves as a capacitance component of the LC resonance circuit and is a DC limiting capacitor for preventing the shift voltage VS from flowing to the ground.

Here, the second variable capacitance diode DV2
Is supplied with a forward bias voltage VC ′ from the anode side. The shift voltage VS is applied as a reverse bias voltage to the cathode of the second variable capacitance diode DV2. That is, in the second variable capacitance diode DV2,
Forward bias voltage VC 'and reverse bias voltage (shift voltage V
S) and a potential difference is applied, and the potential difference determines the inductance value of the second variable capacitance diode DV2 that operates inductively.

The negative resistance circuit section Y includes an oscillation transistor Tr1, various capacitors C5 to C7, and various resistors R1 to R.
2 and.

The amplifier circuit section Z is composed of an amplifying transistor Tr2, various capacitors C8 to C11, a resistor R3, and an inductance element L2.

In such an oscillating circuit, if the collector of the oscillating transistor Tr1 of the negative resistance circuit section Y is grounded at high frequency, the impedance seen from the base becomes negative, and the oscillating transistor Tr1 has a negative impedance. If the resonance circuit section X is connected to the capacitor via the coupling capacitor 10 and the other end is grounded, this circuit has the amplitude characteristics of the resonance circuit section X and the negative gain of the transistor of 1 or more, and the resonance circuit and the transistor have It oscillates at a frequency that satisfies the condition that the sum of the sex phase angles is 2nπ (n is an integer). Then, this oscillation signal is supplied to the amplifying transistor Tr2, is amplified here, and is oscillated and output from the output element OUT.

In the resonance circuit section X shown in FIG.
Forward bias voltage VC 'and reverse bias voltage (shift voltage V
Since the inductance value of the second variable-capacitance diode DV2, which is determined by the potential difference from S), constitutes the inductance component of the LC resonance circuit, the potential difference is set to two stepwise values to set the resonance frequency. It can be switched.

Here, when the strip line SL3 is formed, even if the desired characteristic at the time of setting is slightly changed due to the displacement of the conductor film or bleeding, the setting of this potential difference is
The value may be set so as to adjust the fluctuation of the strip line SL4. That is, a fine adjustment process of forming a stub conductor for mechanically adjusting the characteristics on the strip line SL4 and partially burning out the stub conductor or the strip line SL4 by irradiation with a laser beam is completely unnecessary.

Also, when it is desired to change the oscillation frequency, it becomes unnecessary to redesign the circuit constants of the strip line SL4 and the capacitor C3, and the shift voltage VS applied to the cathode of the second variable capacitance diode DV2 can be adjusted. Good.

In addition, since the potential difference applied to both ends of the second variable capacitance diode DV2 does not become zero when the oscillation circuit is operating, the operation and characteristics of the second variable capacitance diode DV2. Stabilizes.

Further, the second variable capacitance diode DV2
Has a potential of a difference between the forward bias voltage VC ′ and the reverse bias voltage (shift voltage VS), and has some inductance component. Then, the variation of the impedance of the second variable capacitance diode DV2 is reduced because there is any potential difference. Therefore, for example, when the shift voltage VS is set to a plurality of types of voltages with respect to the forward bias voltage VC ′ in order to obtain oscillation outputs at a plurality of oscillation frequency bands, oscillation in each oscillation frequency band is generated. The difference in output level can be reduced.

For example, the forward bias voltage VC 'is shifted so that the center frequency of the oscillation output on the low frequency side is 3.5 GHz and the center frequency of the oscillation output on the high frequency side is 3.75 GHz. The resonance circuit unit X in which the difference from the voltage VS is adjusted is set. It should be noted that, by the continuously changing first control voltage VT supplied to the first variable capacitance diode DV, the variable range is changed from the center frequency to 200 degrees, respectively.
It was set to MHz.

As a result, in the output having the center frequency of 3.5 GHz which is the first oscillation output, in the frequency variable range,
The output level characteristic was 0 to 0.8 dBm. Further, in the output having the center frequency of 3.75 GHz which is the second oscillation output, the output level characteristic is 0 to 0 even in the frequency variable range.
It was 0.8 dBm.

That is, it was confirmed that there is almost no difference in output level between the two oscillation outputs, and for example, it is a frequency shift type high frequency voltage controlled oscillator circuit capable of obtaining a wide variable range corresponding to a direct conversion type IC.

As the forward bias voltage VC ', a fixed voltage obtained by dividing the power supply voltage VCC of the frequency shift type high frequency voltage controlled oscillator circuit by the resistors R10 and R11 is used. Further, as the shift voltage VS as the second control voltage, a plurality of fixed potentials that change in stages are set.

However, the second control voltage (shift voltage VS) is set to a value other than a plurality of fixed potentials that change stepwise,
For example, a continuously changing voltage may be used.

Further, a shift voltage which is a second control voltage may be supplied to the anode side of the second variable capacitance diode DV, and a reverse bias voltage having a fixed voltage value may be supplied to the cathode side. .

Further, the second variable capacitance diode DV2
In consideration of the potential difference applied to the cathodes, both the voltages applied to the cathode and the anode may be continuously varying voltages.

[0050]

According to the present invention, the second inductively operating
The variable capacitance diode is connected in series with the strip line, and is connected to the negative resistance circuit section. A bias voltage and a shift voltage are applied to the anode and cathode of the second variable capacitance diode, respectively.

As a result, the second control voltage (shift voltage) supplied to the second variable capacitance diode causes the second
The inductance component of the variable capacitance diode can be arbitrarily adjusted, for example, continuously or intermittently, and the oscillating frequency can be switched (shifted) or continuously changed.

Further, since the impedance of the second variable capacitance diode does not fluctuate so much, the difference in the output level is less likely to occur in the oscillation characteristics before and after the oscillation frequency is shifted or varied.

Further, in the formation of the strip line which constitutes the inductance component of the resonance circuit, there are cases in which there is some variation from the design value. Further, even if the required characteristic of the oscillation frequency is changed, by adjusting the potential difference applied to the second variable capacitance diode, it is possible to very easily cope with the fluctuation due to the formation of the strip line and the change of the oscillation frequency.

[Brief description of drawings]

FIG. 1 is an external perspective view of a high frequency component including a frequency shift type high frequency voltage controlled oscillator circuit of the present invention.

FIG. 2 is a circuit diagram of a frequency shift type high frequency voltage controlled oscillator circuit of the present invention.

FIG. 3 is a circuit diagram of a conventional voltage controlled oscillator circuit.

FIG. 4 is a circuit diagram of a resonance circuit section of a conventional frequency shift type voltage controlled oscillator circuit.

FIG. 5 is a circuit diagram of a resonance circuit section of a conventional high frequency voltage controlled oscillator circuit.

FIG. 6 is a circuit diagram of a conventional frequency shift type high frequency voltage controlled oscillator circuit.

[Explanation of symbols]

X resonance circuit section Y Negative resistance circuit part Z amplifier circuit section C21 capacitor C4 coupling capacitor DV First variable capacitance diode DV2 Second variable capacitance diode S shift circuit VS shift voltage VC 'Forward bias voltage

Claims (2)

[Claims] 1. A strip line, first and second variable capacitance diodes and a capacitor, and resonance by first and second control voltages supplied to the first variable capacitance diode and the second variable capacitance diode. A resonance circuit unit that controls the frequency, a negative resistance circuit unit that includes an oscillation transistor that outputs an oscillation signal based on the resonance frequency of the resonance circuit unit, and an amplification circuit unit that includes a transistor that amplifies the oscillation signal. A frequency shift type high frequency voltage controlled oscillator circuit, wherein the anode side of the first variable capacitance diode is grounded,
A frequency shift characterized in that the cathode side is connected to one end of a strip line and the other end of the strip line is connected to a negative resistance circuit section via a capacitor, a second variable capacitance diode, and a coupling capacitor. Type high frequency voltage controlled oscillator circuit. 2. The frequency-shifted high-frequency voltage controlled oscillation according to claim 1, wherein a bias voltage is applied to the anode of the second variable capacitance diode, and a second control voltage is applied to the cathode. circuit.