JP2003078350A - High-frequency voltage controlled oscillator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency voltage controlled oscillator circuit capable of increasing a frequency shift amount, increasing a variable frequency range and hardly causing a difference between the oscillation outputs. SOLUTION: The voltage controlled oscillator circuit comprises a resonance circuit section X including a resonance circuit consisting of a strip line S, a variable capacitance diode DV1 being inductively operated and a capacitor C2, a negative resistance circuit section Y, and an amplifier circuit section Z. A first variable capacitance diode DV2 for frequency shift and a second variable capacitance diode DV3 for frequency shift are arranged in series in an anode for the diode DV1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency voltage controlled oscillator used in mobile communication equipment such as a mobile phone for switching the channel frequency of a transmission / reception signal.

[0002]

2. Description of the Related Art In mobile band communication equipment, there is an increasing demand for smaller, lighter weight, thinner terminals and lower voltage, and a voltage controlled oscillator equipped with a voltage controlled oscillator circuit is also light and thin. The demand for shorter size and lower cost is increasing.

With the diversification of communication systems, there has been proposed a circuit configuration for reducing the circuit scale and the number of components in a voltage controlled oscillator that outputs two different oscillation frequency bands.

Mobile communication equipment manufacturers are studying to solve the problem, and the direct conversion method is becoming the mainstream as one of the solutions.

In the communication system of mobile communication equipment, this is conventionally called the super-heterodyne system, and in the receiving circuit, the received wave is once dropped to an intermediate frequency and then converted into an audio signal. Is a method of directly converting the audio signal into an audio signal. This method has become possible due to the development of baseband ICs. 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 system is more effective as the voltage controlled oscillator can be covered by a single transmitting / receiving oscillator. In the case of multi-system, the voltage controlled oscillator used in the direct conversion method is mainly a voltage controlled oscillator in the 3 GHz band.

However, in addition to the high frequency, this voltage controlled oscillator has a very wide frequency range.
I need 400MHz. When the voltage controlled oscillator circuit corresponding to the dual mode system (two communication systems having different transmission / reception frequency bands) or the triple mode system is supported, the frequency range is further expanded.
Further, the control voltage sensitivity for controlling the oscillation frequency of the voltage controlled oscillator is increasing.

That is, in the future, there will be a need for a high-frequency voltage-controlled oscillator capable of oscillating stably with a wider frequency range which can be varied more and more by a control voltage.

As shown in FIG. 4, the high frequency voltage controlled oscillator includes a resonance circuit composed of a strip line SL, a variable capacitance diode DV and a capacitor C3, and supplies an external voltage to the variable capacitance diode DV to change the resonance frequency. A resonance circuit section X to be controlled, a negative resistance circuit section Y including an oscillation transistor that outputs an oscillation signal based on the resonance frequency of the resonance circuit section X, and an amplification circuit section Z including an amplification transistor that amplifies the oscillation signal. It consists of and.

In such a voltage controlled oscillator circuit, in order to broaden the variable range of the oscillation frequency or support a plurality of oscillation frequency bands, the variable capacitance diode of FIG. And the switching diode Di is arranged in parallel with the strip line SLs. By supplying a shift control voltage to the switching diode Di from the shift control terminal Vs, the strip line SLs is separated from or connected to the variable capacitance diode DV, and the strip line SLs is inductively operated in a high frequency region. The combined inductance due to the inductance component of the capacitance diode DV and the inductance component of the strip line SLs changes stepwise, and the frequency of the oscillation output can be switched stepwise.

[0010]

However, the switching diode Di described above has a PI excellent in high frequency characteristics.
N diodes are often used. Then, a voltage is applied to the switching diode Di of this PIN diode,
The resonance frequency is shifted by utilizing the open (OFF) and short (ON) states. However, due to the characteristics of the switching diode Di, when the voltage is applied and short-circuited, it has an ON resistance, and the Q value of the resonant circuit deteriorates. In the open state, the capacitance between terminals affects the resonance frequency. Therefore, it is difficult to control the frequency of the oscillation output with the shift amount as designed.

Further, due to the characteristics of the variable capacitance diode, when a short circuit is caused by applying a voltage, it has an ON resistance, which deteriorates the Q value of the resonance circuit. In the open state, the capacitance between terminals affects the resonance frequency. Smaller capacitance between terminals is desirable. It is desirable that both the ON resistance and the inter-terminal capacitance of the variable capacitance diode are small, but due to the structure, the inter-terminal capacitance and the ON resistance have an inversely proportional relationship. When the oscillation frequency is shifted, characteristic deviation occurs in each frequency band. It is an object of the present invention to provide a voltage-controlled oscillator that is unlikely to cause a difference in oscillation output characteristics when switching frequency bands, can always obtain a stable oscillation state, and can cope with higher frequencies.

Further, there is a limit to obtaining a sufficiently wide shift amount by using one strip line SLs, and it is difficult to expand the variable frequency range by combining it with an external control voltage terminal.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to provide a high frequency voltage control type oscillation circuit capable of coping with high frequencies in which a shift amount can be increased. is there.

[0014]

According to the present invention, there is provided a resonance circuit section comprising a strip line, a variable capacitance diode, and a capacitor, for controlling an resonance frequency by supplying an external voltage to the variable capacitance diode. In a high frequency voltage control type oscillation circuit comprising a negative resistance circuit section including an oscillation transistor that outputs an oscillation signal based on the resonance frequency of the resonance circuit section and an amplification circuit section including an amplification transistor that amplifies the oscillation signal, A high frequency voltage control type oscillation circuit is characterized in that a plurality of frequency shifting variable capacitance diodes are arranged in series between an anode of the variable capacitance diode and a ground potential.

The frequency shifting variable capacitance diode is composed of first and second frequency shifting variable capacitance diodes whose cathodes are connected to each other, and a first frequency shifting variable capacitance diode connected to the capacitance diode. The connection portion with and is grounded via a resistor, and the frequency shift control terminal is arranged at the connection portion between the first frequency shift variable capacitance diode and the second frequency shift variable capacitance diode.

[0016]

In the present invention, the resonance frequency switching circuit (hereinafter referred to as shift circuit S) provided in the resonance circuit section is connected to the variable capacitance diode that operates inductively. The shift circuit includes a first frequency shifting variable capacitance diode,
A plurality of variable capacitance diodes for frequency shift, such as a second variable capacitance diode for frequency shift, are connected in series.

That is, the series combination of the variable capacitance diode that operates inductively at the oscillation frequency and the plurality of frequency shifting variable capacitance diodes increases the composition of the respective inductance components. As a result, the shift amount can be increased. Therefore, even if the oscillation frequency of the oscillation output is largely dispersed, it is possible to easily cope with the case where the variable frequency range is enlarged.

The frequency shifting variable capacitance diode is composed of first and second frequency shifting variable capacitance diodes whose cathode sides are connected to each other, and a first frequency shifting variable capacitance diode connected to the capacitance diode. The connection part of (1) was grounded via a resistor, and the frequency shift control terminal was arranged at the connection part between the first frequency shift variable capacitance diode and the second frequency shift variable capacitance diode. With this, the inductance of the first variable capacitance diode for frequency shift and the second variable capacitance diode for frequency shift can be simultaneously changed by one shift control signal, so that the control can be performed very easily.

[0019]

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

FIG. 1 shows a high frequency component, for example, a voltage controlled oscillator, in which the high frequency voltage control type oscillation circuit of the present invention is incorporated. That is, the high frequency component is formed on the multilayer circuit board integrally with the circuit, for example, the receiving circuit of the communication circuit, in addition to the voltage controlled oscillation circuit. In FIG. 1, on the surface of the multilayer substrate 10, in addition to the predetermined surface wiring pattern 11, circuit components such as a switching diode, a varicap diode, a resistor, and an IC chip such as a direct conversion which constitute a voltage controlled oscillator and other circuits. 12 is formed,
In addition to the internal wiring pattern, a strip electrode serving as a capacitor electrode, an inductor conductor, and a ground potential conductor film are formed in the multilayer substrate. Also,
A strip line or the like that serves as an inductor conductor may be formed on the surface of the multilayer substrate 10. On the end surface of such a multi-layer substrate 10, terminal electrodes 13 which are terminals of various circuits are formed.

The high frequency voltage control type oscillation circuit formed on such a multilayer circuit board 10 has a structure shown in a partial block circuit diagram as shown in FIG. The resonance circuit section X, which is the block circuit section in FIG. 2, has the circuit configuration shown in FIG. The voltage controlled oscillator circuit of the present invention is a high frequency voltage controlled oscillator circuit in which a direc-conversion type IC can correspond to the control IC of the receiver circuit. The oscillation output shifts two resonance frequencies, for example, 3.6 GHz and 3.7 GHz at the center frequency so that a wide range of frequencies can be changed. Wrap it. For example, if the center frequency of one resonance frequency can be varied at ± 200 MHz, for example, 3.4 GHz to 3.9 GHz as a whole.
Oscillation frequencies up to 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.

As shown in FIG. 3, the resonant circuit section X includes a strip line SL, a variable capacitance diode Dv1 that operates inductively, capacitors C1, C2, C3, an inductor element L1, and a first frequency shift. Variable capacitance diode DV2, a second frequency shifting variable capacitance diode DV3, resistors RS1 and RS2, and a capacitor C4. It should be noted that, of the above-mentioned resonant circuit section X, the first
Frequency shifting variable capacitance diode DV2, second frequency shifting variable capacitance diode DV3, resistor RS1,
The shift circuit shown by the dotted line is composed of RS2 and the capacitor C4.

Further, the resonance circuit section X has a control voltage terminal VT to which an external control voltage signal for varying the characteristic of the variable capacitance diode DV1 which operates inductively is supplied.
Further, the shift circuit is provided with a frequency shift control terminal Vs to which the shift voltage signal supplied to the first frequency shift variable capacitance diode DV2 and the second variable capacitance diode DV3 is supplied.

The negative resistance circuit section Y includes an oscillating transistor Tr1, various capacitors C5 to C7, and various resistors R1 to R.
3 and 3.

The amplifier circuit section Z includes an amplifying transistor Tr2, various capacitors C8 to C11, various resistors R4,
It is composed of 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 the same impedance. If the resonance circuit unit X is connected to the resonance circuit unit X via the coupling capacitor C3 and the other end is grounded, this circuit has an amplitude characteristic of the resonance circuit unit X and a negative gain of the transistor of 1 or more, and the resonance circuit and the transistor negative 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.
As seen from the coupling capacitor C3, the inductance component of the LC resonance circuit includes the strip line SL1, the variable capacitance diode DV1 that operates inductively, the first frequency shift variable capacitance diode DV2 of the shift circuit, and the second frequency shift variable. It becomes a synthetic inductance of the inductance component of the capacitance diode DV3, and the capacitance component of the LC resonance circuit becomes the capacitor C2.

When the control voltage VT is supplied from the control voltage terminal, the inductance of the variable capacitance diode 3 changes inductively, and for example, the oscillation frequency is continuously changed by continuously changing the control voltage. Can be changed.

The shift circuit is arranged on the anode side of the variable capacitance diode DV1 and at the ground potential. This shift circuit is configured by connecting a plurality of variable capacitance diodes for frequency shift in series. Specifically, the variable capacitance diode DV1 is arranged at the anode side and the ground potential. This shift circuit uses a variable capacitance diode DV.
The anode of the first variable capacitance diode DV2 for frequency shifting is connected to the anode side of the first diode, and the cathode of the second variable capacitance diode DV2 for frequency shifting is connected to the cathode of the first variable capacitance diode DV1 for frequency shifting. The anode of the second frequency shifting variable capacitance diode DV2 is connected to the ground potential.

The connecting portion between the variable capacitance diode DV1 and the first frequency shifting variable capacitance diode DV2 is connected to the ground potential with respect to the resistor RS1. Further, the first frequency shifting variable capacitance diode DV2 and the second frequency shifting variable capacitance diode DV
The shift voltage is supplied to the connection portion with 3 through the resistor RS2.

In the above shift circuit, when no voltage is supplied to the shift control terminal Vs, the external control terminal Vs is supplied.
By supplying a continuous predetermined voltage from T to the variable capacitance diode DV1, the voltage is changed.
It is applied between the ground potential via V1 and the resistor RS1, and this causes the variable capacitance diode DV.
A continuous inductive change of 1 and an oscillation output for continuously varying the oscillation frequency are obtained from the output terminal OUT.

In the above shift circuit, when a voltage of a predetermined value is supplied to the shift control terminal Vs, the shift voltage is the first frequency shifting variable capacitance diode D.
The voltage is applied from the cathode of V2 to the ground potential via the anode and the resistor RS1, and at the same time, is applied from the cathode of the second variable capacitance diode for frequency shift DV2 to the ground potential via the anode.

That is, the first and second frequency shifting variable capacitance diodes DV2 and DV3 both operate (have a predetermined inductive property), and the inductance component of the entire LC resonant circuit is greatly changed.

As a result, the frequency of the oscillation output can be changed stepwise by supplying or not supplying the shift voltage.
The amount of frequency shift can be controlled by the applied voltage. Moreover, since this shift circuit uses, for example, two variable capacitance diodes DV2 and DV3,
2 in comparison with the case where two variable capacitance diodes are used
A double shift amount can be obtained.

The variable capacitance diode D for frequency shifting is used.
By using a variable capacitance diode having a small ON resistance for V2 and DV3, it is possible to reduce the change in the impedance component and reduce the characteristic difference between the oscillation outputs before and after the shift.

FIG. 2 is a circuit diagram mainly showing a shift circuit portion of another high frequency voltage control type oscillation circuit of the present invention. In this circuit diagram, in order to match the impressions of the first frequency shift variable capacitance diode DV1 and the second frequency shift variable capacitance diode DV3 with the shift voltage,
For example, the first frequency shifting variable capacitance diode DV
Bias voltage is being supplied to 2. That is, a voltage is applied to the bias terminal Vd, and normally, the resistance RS1 and the resistance RS
The voltage divided into 3 is applied to the first frequency shifting variable capacitance diode DV2. By adjusting this applied voltage, the operations of the first frequency-shifting variable capacitance diode DV2 and the second frequency-shifting variable capacitance diode DV3 due to the shift voltage can be adjusted to be completely the same. It becomes very easy to control the operation by.

As described above, by using the frequency shift variable capacitance diodes DV2 and DV3 having a small resistance component between terminals, for example, the frequency before the resonance frequency is shifted to 3.4 GHz and the frequency after the resonance frequency is shifted. Frequency 3.
At 9 GHz, almost the same locus can be traced on the Smith chart, and the output level is 0 to 1 dBm and the fluctuation is very small regardless of switching of the resonance frequency band.

In the above embodiment, the strip line SL may be formed by forming a microstrip line on the surface of the multi-layer substrate, or may be formed as a strip line in the multi-layer substrate.

[0040]

As described above, according to the present invention, it is possible to obtain high-frequency oscillation, obtain an oscillation output in a wide frequency range, and increase the shift amount.

Moreover, these controls can be easily controlled with one shift voltage. Further, even if the frequency band is switched, there is no characteristic difference in the characteristics of the oscillation output, and a stable oscillation output can always be obtained.

[Brief description of drawings]

FIG. 1 is an external perspective view of a multilayer circuit board including a high frequency voltage control type oscillation circuit of the present invention.

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

FIG. 3 is a circuit diagram showing a part of another high frequency voltage control type oscillation circuit of the present invention.

FIG. 4 is a circuit diagram of a conventional high frequency voltage controlled oscillator circuit.

FIG. 5 is a circuit diagram showing a part of a conventional high frequency voltage control type oscillation circuit having a shift function.

[Explanation of symbols]

X resonance circuit section Y Negative resistance circuit part Z amplifier circuit section SL strip line DV1 variable capacitance diode DV2 Frequency shift variable capacitance diode DV3 Variable capacitance diode for frequency shift

Claims (2)

[Claims] 1. A resonance circuit section including a resonance circuit composed of a strip line, a variable capacitance diode and a capacitor, for controlling an resonance frequency by supplying an external voltage to the variable capacitance diode, and a resonance circuit section based on the resonance frequency of the resonance circuit section. A negative resistance circuit section including an oscillation transistor that outputs an oscillation signal and an amplification circuit section including an amplification transistor that amplifies the oscillation signal. A high-frequency voltage control type oscillation circuit in which a plurality of frequency shifting variable capacitance diodes are arranged in series between the potential and the potential. 2. The variable frequency diode for frequency shift comprises a first and a second variable capacitance diode for frequency shift whose cathodes are connected to each other, and a first variable capacitance diode for frequency shift which is connected to the capacitive diode. While grounding the connection part with and through the resistor,
2. The high frequency voltage controlled oscillator circuit according to claim 1, wherein a frequency shift control terminal is arranged at a connection portion between the first frequency shift variable capacitance diode and the second frequency shift variable capacitance diode.