KR100731975B1 - Oscillator Core with Capacitive Common Node for Frequency Multiplication - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator (VCO) having a push-push type frequency multiplier for effectively obtaining high frequency oscillation, and particularly to obtain an output of a frequency multiplied in an ultra high frequency band. An oscillator core that obtains twice the frequency output from a common ground capacitor common terminal coupled between a pair of coupled transistors and the two. This results in a doubled frequency output from the voltage controlled oscillator itself, without the need for a separate frequency multiplier, thereby providing a semiconductor area in the implementation of a single monolithic microwave integrated circuit (MMIC) or a radio frequency integrated circuit (RF integrated circuit). It has the advantage of reducing over current consumption.

An oscillator core using a capacitor common terminal for frequency multiplication of the present invention is cross-coupled with a positive feedback structure to compensate for signal loss in an LC resonator and an LC resonator composed of an inductor and a capacitor to determine an oscillation frequency and obtain a stable signal. In the oscillator core consisting of a plurality of transistors, the common ground capacitor common terminal is connected by connecting a capacitor between the base terminals of the pair of symmetrical transistors constituting the oscillator core, and the frequency output is doubled from the common ground capacitor common terminal It is characterized in that the extraction.

Voltage controlled oscillator, frequency multiplication, capacitor common terminal, microwave integration circuit, RF integrated circuit, diode distortion characteristics, rise time, fall time,

Description

Oscillator Core with Capacitive Common Node for Frequency Multiplication

1 is a block diagram of a device for obtaining a double frequency output by connecting a separate frequency multiplier (Frequency Multiplier) to a conventional high frequency oscillator core (Oscillator Core).

2 is a block diagram of a device for obtaining a double frequency output at an emitter common node of a conventional negative resistance cross-coupled differential oscillator.

3 is a block diagram of an oscillator core using a capacitor common terminal for frequency multiplication according to a preferred embodiment of the present invention.

4 is a configuration diagram of an oscillator core showing the flow of a current signal in a cross-coupled network according to the present invention.

5 is a voltage-current characteristic diagram showing a voltage signal relationship with respect to a magnitude of a current signal in a base-emitter junction transistor according to the present invention.

Figure 6 is a block diagram of the oscillator core showing the flow of current in the on / off state of the oscillator core transistor according to the present invention.

7 is a distortion characteristic diagram of a voltage signal with respect to a current signal in a transistor base terminal according to the present invention;

8 is a small-signal equivalent circuit diagram of a network cross-coupled from the collector terminal to the opposite transistor in accordance with the present invention.

9 is a voltage signal diagram illustrating a difference between a rise time and a fall time of a voltage signal at a base end of a transistor according to the present invention;

10 is a change in output power according to the increase of the common terminal capacitor C ₂ according to the present invention.

11 is an exemplary diagram of a voltage signal showing an output of which the frequency obtained by the capacitor common terminal of the voltage controlled oscillator according to the present invention is doubled.

12 is a circuit diagram of a bipolar junction transistor (BJT), which is an active device of an embodiment of the present invention, replaced with a field effect transistor (FET).

FIG. 13 is a circuit diagram using a common capacitor terminal in a general differential type oscillator in which a Colpitts oscillator is formed in a balanced structure rather than a cross-coupled negative resistance differential oscillator as in the present invention.

Fig. 14 is a circuit diagram in which a capacitor common terminal of the embodiment of the present invention is replaced with a resistance common terminal.

******* Explanation of symbols on the main parts of the drawings *******

110: LC tank 120: cross-coupled transistor network

121, 122: coupling capacitor

131: Vc- terminal 132: Vc + terminal

133: first transistor 134: second transistor

135: common terminal capacitor

136 and 137: capacitors for forming a capacitor common terminal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator (VCO) in which a push-push type frequency multiplier is incorporated in a circuit to efficiently obtain high frequency oscillation, and particularly, a cross-coupled differential. By using the ideal switching characteristics of the transistor connected in the structure of the oscillator to obtain an output frequency corresponding to twice the resonant frequency of the LC resonator from the common ground capacitor common terminal.

With the development of high frequency communication, oscillators are required to operate stably with high output frequency and low phase noise. One suitable device is a cross-coupled differential structure oscillator.

In general, in order for an oscillator having an LC resonator to oscillate in a high frequency band, an inductor and a capacitor, which are individual elements constituting the LC resonator, need to be physically very small. In an actual semiconductor process, an error in device values becomes larger for small devices. It is known that the higher the operating frequency of the oscillator, the greater the difference between the design value and the actual operating frequency after manufacture.

In order to improve the practical problem of the voltage controlled oscillator using the LC resonator, the oscillator itself is operated at a low frequency and multiplied to obtain an output frequency, and one of the structures commonly used as a multiplier circuit for frequency multiplication is used. It is a push-push method.

1 is a block diagram of a device that additionally connects a push-push frequency multiplier to a conventional general voltage controlled oscillator core to obtain twice the frequency output. Among the harmonics, odd-order harmonics are canceled and only even-order harmonics are added in the same phase and appear at the output stage. At this time, the desired frequency is obtained through the filter. Since this method requires a separate frequency multiplier, there is a disadvantage in that the semiconductor area and the current consumption are increased when configuring an ultra high frequency integrated circuit (MMIC) or an RF integrated circuit (RFIC).

2 is a block diagram of a device that obtains twice the frequency output from the emitter common terminal of a conventional negative resistance cross-coupled differential oscillator, which is a common emitter to increase the output power slightly reduced in the high frequency band When a load of an inductor is added to a terminal, there is a problem in that the total area of the circuit due to the inductor load increases when fabricating a high frequency integrated circuit (MMIC).

The present invention has been proposed to solve the above problems, and in particular, by connecting a capacitor to the base terminal of the two transistors of the conventional differential oscillator core, the distorted voltage signal generated by the characteristics of the base-emitter diode of the two transistors The summation at the virtual ground capacitor capacitive common node cancels the fundamental frequency and yields twice the output frequency. Thus, by using the common ground capacitor common terminal for frequency multiplication, a separate frequency multiplier or element is not required as in the conventional oscillator, so the oscillator core is simple in design and has a small semiconductor area and low power consumption. The purpose is.

In order to achieve the above object, according to the first aspect of the present invention, a transistor network cross-coupled with a positive feedback structure for producing a negative resistance component to compensate for the resistive loss of the LC resonator and the LC resonator to determine the fundamental oscillation frequency An oscillator core comprising: a common ground capacitor connected to a base terminal of a pair of symmetrical transistors constituting the oscillator core to form a virtual ground capacitor common terminal, and generating a double frequency output from the virtual ground capacitor common terminal It is characterized by.

In addition, the output of the virtual ground capacitor common terminal of the present invention generates a double output frequency using the nonlinear characteristic of the diode voltage-current characteristic curve at the base-emitter junction of the symmetrical transistor operating in the active region. It is characterized by.

In addition, the output of the common ground capacitor common terminal of the present invention uses the difference between the rise time and the fall time according to the change of the base input resistance generated as the base input current changes in the symmetrical transistor operating in the active region. It is characterized by generating a double output frequency.

In addition, the output of the common ground capacitor common terminal of the present invention, it is possible to increase the output power by using the reduction characteristic of the rise time according to the change of the common capacitor capacity connected to the base terminal of the symmetrical transistor.

According to a second aspect of the present invention, an oscillator core comprising an LC resonator for determining an oscillation frequency and a transistor network in which a pair of symmetric transistors are differentially coupled to compensate for the loss of the LC resonator is provided, and the base terminal of the symmetric transistor is provided. The capacitors are commonly connected to each other to form a common ground capacitor common terminal, and generate twice the frequency output power from the common ground capacitor common terminal.

Finally, according to the third aspect of the present invention, an oscillator core composed of a transistor network cross-coupled with a positive feedback structure for producing a negative resistance component to compensate for resistive losses of an LC resonator and an LC resonator for determining a fundamental oscillation frequency And a resistor is commonly connected to the base terminal of the symmetric transistor to form a virtual ground resistor common terminal, and generates twice the frequency output power from the virtual ground resistor common terminal.

Hereinafter, exemplary embodiments of an oscillator core using a capacitor common terminal for frequency multiplication according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a configuration diagram of an oscillator core using a capacitor common terminal for frequency multiplication according to a preferred embodiment of the present invention, and FIG. 4 is a configuration of an oscillator core showing a current signal flow in a cross-coupled network according to the present invention. 5 is a voltage-current characteristic diagram illustrating distortion characteristics of a voltage signal with respect to a magnitude of a current signal in a base-emitter junction transistor according to the present invention. FIG. 6 is an on / off state of an oscillator core transistor according to the present invention. Fig. 7 is a diagram illustrating a distortion characteristic of a voltage signal with respect to a current signal in a transistor base terminal according to the present invention, and Fig. 8 is a cross section from a collector terminal to an opposite transistor according to the present invention. Small-signal Equivalent Circuit of a Combined Network, FIG. 9 shows at the base end of a transistor according to the invention. Voltage characteristic showing the rise time and fall time difference between the pressure signal, and Fig. 10 is a variation of the output power according to the common terminal capacitor increases in C ₂ in accordance with the present invention, is 11 two eoteonaen in capacitor common terminal according to the invention A voltage characteristic diagram showing a frequency output signal multiplied by a factor of two.

As shown in FIG. 3, an oscillator core using a capacitor common terminal for frequency multiplication, which is an embodiment of the present invention, includes an LC resonator 110 composed of an inductor and a variable capacitor diode and a crossover network for transistor cross coupling. The first transistor 133 and the second transistor 134 for generating a negative resistance component for compensating for the attenuation of a signal generated by the parasitic resistance component of the LC resonator 110 and the LC resonator 110 are cross-coupled. By extracting the sum of two differential voltages (131,132) having a phase difference of 180 ^o from the capacitors (136, 137) connected to the base input terminals of the first and second transistors (133, 134), the fundamental frequency component is suppressed and doubled. Will produce a frequency output.

The main principle of generating an output signal at the common terminal 135 of the capacitors 136 and 137 is largely divided into two.

One of the two signals having a phase difference of 180 ^o causes distortion in the signal due to nonlinearity of the diode voltage-current characteristic curves of the base-emitters of the first and second transistors 133 and 134. It is added at the common terminal 135 through the capacitors 136 and 137 and has a double output frequency.

In addition, the other is a capacitance that cross-connects the outputs of the first and second transistors 133 and 134 with the inputs of the opposite transistors, resulting in a time constant difference between the rise time and the fall time of the signal, resulting in power of the second harmonic component. Is increased. At this time, when the two signals are added at the common terminal 135 through the capacitors 136 and 137, the fundamental frequency component having a 180 ^° difference in phase disappears and only the second harmonic component remains, thereby doubling the frequency output power. Is generated.

The two reasons mentioned above work in combination, so that the common terminal 135 of the capacitors 136 and 137 can obtain, for example, twice the frequency output power at the oscillation frequency of the voltage controlled oscillator core.

Hereinafter, a characteristic in which an output frequency of an oscillator core using a capacitor common terminal for frequency multiplication according to a preferred embodiment of the present invention is doubled will be described in detail.

The output signal multiplied by the double frequency according to the embodiment of the present invention can be obtained by using the distortion of the signal due to nonlinearity that must exist in the circuit. However, it is assumed here that the two current signals of the negative output and the positive output having the phase difference of 180 ^o are the signals without distortion that repeat the ideal on / off.

4 shows the flow of signals in a cross-coupled network. Since the circuit of the oscillator core using the capacitor common terminal for frequency multiplication has a symmetrical circuit, if the Vc- terminal 131 is a negative signal, the Vc + terminal 132 is positive. Is a signal of.

The positive signal of the Vc-terminal 131 passes through the coupling capacitor 121 to the base of the second transistor 134 and the capacitor common terminals Vout and 135 through the coupling capacitor 121. Since 135 is a virtual ground for the fundamental frequency component, the fundamental frequency component disappears from the capacitor common terminal 135 and only the 2nd harmonics component is output.

On the contrary, if the signal of the Vc + terminal 132 is a positive signal, the signal of the Vc- terminal 131 becomes a negative signal and moves along the opposite path, thereby producing a 2nd harmonic output as described above. You get

The magnitude of the second harmonic at the capacitor common terminal 135 depends on how much the voltage signal is distorted at the base terminal.

5 conceptually illustrates the distortion of a voltage signal. When the current signal is repeatedly rising and falling, the upper part of the voltage signal is lowered by the exponential voltage-current characteristic curve of the diode at the base-emitter junction. It can be seen that compared to the distortion.

This result is because the magnitude of the base input resistance changes as the current signal rises and falls, and thus the slope of the signal changes during the rise and fall.

값의 변화를 구체적으로 설명하면, 도 6에 도시된 바와 같이, 발진기 코어의 두 트랜지스터(133, 134)는 180^o 의 위상 차이를 갖고 온/오프를 반복하게 되며 발진기 코어의 전체 전류는 고정 전류원(Current Source)에 의해 2I_t로 제한되는데, 제1 트랜지스터(133)에 베이스 전류신호가 양의 신호로 인가되면 제1 트랜지스터(133)는 도통되어

의 전류를 흘리게 되는 반면, 반대쪽 제2 트랜지스터(134)에 베이스 전류신호가 음의 신호로 인가되어 제2 트랜지스터(134)는 차단되어

의 전류가 된다. 이 때, 제1 및 제2 트랜지스터(133, 134)의 베이스 입력저항

는 서로 다른 값을 갖게 되어 상승시간과 하강시간에서의 전압신호의 기울기 차이가 발생되는 것이다. 제1 및 제2 트랜지스터(133, 134)의 베이스 입력 저항을 각각

,

라고 하면, 차단되는 제1 트랜지스터의

은 다음과 같이 구해진다.

이므로, These bass input resistance

Specifically, as shown in FIG. 6, the two transistors 133 and 134 of the oscillator core are repeatedly turned on and off with a phase difference of 180 ^° and the total current of the oscillator core is a fixed current source. (Current Source) is limited to 2I _t . When the base current signal is applied to the first transistor 133 as a positive signal, the first transistor 133 is turned on.

While the current flows through, the base current signal is applied to the opposite second transistor 134 as a negative signal so that the second transistor 134 is cut off.

Becomes the current of. At this time, the base input resistance of the first and second transistors 133 and 134

Have different values, resulting in a difference in slope of the voltage signal at the rise time and the fall time. Base input resistances of the first and second transistors 133 and 134, respectively.

,

Speaking of the first transistor to be blocked

Is obtained as follows.

Because of,

의 조건에 의해

는 매우 큰 값의 저항성분이 된다. 여기서,

는 트랜지스터의 이미터 공통 증폭기에서의 전류 증폭률이다. 반면, 반대쪽의 제2 트랜지스터(134)는 도통되어

는

이므로, Become,

By the terms of

Becomes a very large resistance component. here,

Is the current amplification factor in the emitter common amplifier of the transistor. On the other hand, the second transistor 134 on the opposite side is turned on

Is

Because of,

보다 저항성분이 작게 되는 것을 알 수 있고, 수학식1과 수학식2의 관계로부터 Become relatively

It can be seen that the resistance component becomes smaller, and from the relationship between Equations 1 and 2

The result can be seen.

The distortion of the voltage signal according to the change of the base input resistance as shown in Equation 3 is shown in detail as shown in FIG. The current signal (dotted line) and the voltage signal (solid line) are generated with a phase difference of ^90o later than the current signal due to the characteristics of the base-emitter junction capacitor, and the rise time of the signal due to the junction capacitor component and the base input resistance component. Differences in descent time will occur. The base input resistance r _p decreases as the base current signal rises (area-1). As shown in FIG. 7, the slope of the rise of the voltage signal is higher than the current signal at the peak point where the current and voltage signals rise. On the contrary, while the current signal falls from the positive maximum to the negative maximum (area-2), the base input resistance r _p becomes larger and larger so that the falling slope of the voltage signal becomes gentle and the voltage signal is distorted. You can see that. As such, the distorted input voltage signals at the bases of the two first and second transistors 133 and 134 are added to each other with a 180 ° phase difference at the capacitor common terminal 135 to obtain a double frequency output. In addition, when the current supplied to the oscillator core is increased, the magnitude of the voltage signal distorted at the base terminals of the transistors 133 and 134 is also increased, thereby increasing the magnitude of the output power.

Another feature for obtaining twice the frequency output of the embodiment of the present invention is that the time constant value of the signal rise time is reduced in the cross-coupled network so that the output is obtained. For simplicity, the two opposing amplifiers of the oscillator core are perfectly symmetric, assuming that the collector signal input to the base of the transistor is ideal, if only one of the two symmetrical amplifiers interprets the signal for one of the amplifiers, the other The signal result for the amplifier of is same. An equivalent circuit for interpreting a signal for one amplifier is shown in FIG.

FIG. 8 is a small-signal equivalent circuit of a network cross-coupled from the collector terminal to the opposite transistor, replacing the LC-tank (110 in FIG. 3) with any ideal signal source and replacing the opposite transistor at the collector terminal. The cross-coupled network (120 of FIG. 3) may be represented as a small-signal equivalent circuit. If the time constant for the signal flow in an equivalent circuit is expressed by a formula,

은 커플링 커패시터,

는 공통단자 커패시터,

는 트랜지스터의 베이스-이미터 접합 커패시턴스 성분이며,

는 트랜지스터의 베이스 입력 저항이다. 컬렉터의 전압신호는

_,

_,

에 충전이 이루어지게 되고 충전된 에너지는 대부분 커패시터 공통단자로 방전하게 되고 일부는 트랜지스터의 베이스 입력 단자로 방전하게 된다. 수학식4에서

과

가 고정된 값을 갖는다면, 충전시의 전체 커패시턴스 값은 공통단자 커패시터

의 용량 값에 의해 변하게 되고

의 용량 값이 커질수록 전체 시상수

의 값은 작아지게 된다. 결과적으로 트랜지스터 베이스 입력 단에서의 신호는 도 9에 도시된 바와 같이, 상승시간이 하강시간보다 짧아지게 되어 2차 고조파 성분의 전력이 증가되어 커패시터 공통단자(Vout)에서 체배된 주파수 출력전력이 증가하는 특성을 얻을 수 있게 된다. 이러한 공통단자 커패시터

의 용량 값의 증가에 따른 출력전력의 변화를 도 10에 나타내었다. 도면에서와 같이

의 용량 값이 증가하면 상승시간이 짧아져 출력전력이 증가하는 특성을 보여주고 있다. Becomes here,

Silver coupling capacitor,

Is a common terminal capacitor,

Is the base-emitter junction capacitance component of the transistor,

Is the base input resistance of the transistor. The voltage signal of the collector

_,

_,

In this case, most of the charged energy is discharged to the common terminal of the capacitor, and some of the energy is discharged to the base input terminal of the transistor. In Equation 4

and

Has a fixed value, the total capacitance value during charging is the common terminal capacitor.

Is changed by the capacity value of

The larger the time value, the greater the time constant

The value of becomes small. As a result, the signal at the transistor base input terminal has a rise time shorter than the fall time, as shown in FIG. 9, thereby increasing the power of the second harmonic component, thereby increasing the frequency output power multiplied by the capacitor common terminal Vout. To obtain the characteristics. These common terminal capacitor

The change in output power with increasing capacitance value is shown in FIG. 10. As in the drawing

As the capacity value increases, the rise time is shortened and the output power increases.

It can be seen from the above simple equation that the time constant of the rise time and the fall time is generated, and as a result, as shown in FIG. 11, the frequency output doubled at the capacitor common terminal (135 in FIG. 3) is obtained. It becomes possible.

The present invention is applicable to other active devices and oscillators of different structures as in the following example. FIG. 12 is a circuit diagram of a bipolar junction transistor (BJT) as an active device of an embodiment of the present invention replaced with a field effect transistor (FET). FIG. 13 is a circuit diagram using a common capacitor terminal in a general differential type oscillator having a balanced structure instead of a cross-coupled negative resistance differential oscillator as in the present invention, and as shown in FIG. 12. Can be configured not only for bipolar junction transistors but also for field effect transistors. In addition, as shown in FIG. 14, the capacitor common terminal is replaced with the register common terminal, thereby enabling a circuit configuration. Using embodiments of the present invention and several possible circuits, it is possible to extract twice the frequency into the LC tank.

The oscillator core using the capacitor common terminal for frequency multiplication, as in the present invention and some embodiments described above, is not limited to the above embodiments and can be modified in various ways within the scope of the technical spirit of the present invention. .

According to the oscillator core using the capacitor common terminal for frequency multiplication of the present invention made as described above, by using the capacitor common terminal without additional circuitry or elements in the design of the cross-coupled differential voltage controlled oscillator for the high frequency band, Frequency output corresponding to twice the oscillator core frequency can be obtained, and semiconductor area and current consumption can be reduced when implementing a single monolithic microwave integrated circuit (MMIC) or radio frequency integrated circuit (RF). Has an advantage.

Claims (7)

An oscillator core comprising an LC resonator for determining an oscillation frequency and a transistor network in which a pair of symmetric transistors are cross-coupled in a positive feedback structure to generate a negative resistance component to compensate for the resistive loss of the LC resonator, A capacitor common terminal for frequency multiplication is characterized in that a capacitor is commonly connected to a base terminal of the symmetric transistor to form a virtual ground capacitor common terminal, and generates twice the frequency output power from the virtual ground capacitor common terminal. Oscillator Core Used. The method of claim 1, The output of the common ground capacitor common terminal generates twice the frequency output power by using a nonlinear region of a diode voltage-current characteristic curve at the base-emitter junction of the symmetric transistor operating in an active region. Oscillator core using capacitor common terminal for frequency multiplication. The method of claim 1, The output of the common ground capacitor common terminal outputs twice the frequency by using a difference between a rise time and a fall time of a signal generated by a change in a base input resistance caused by a base input current of the symmetric transistor operating in an active region. Oscillator core using a capacitor common terminal for frequency multiplication, characterized in that to generate a. The method according to any one of claims 1 to 3, The output of the common ground capacitor common terminal is characterized in that the output power is increased by the difference between the rise time and fall time generated because the capacitor component and the resistance component is changed at the input terminal of the capacitor and the symmetric transistor configured in the cross-network. Oscillator core using a capacitor common terminal for frequency multiplication. The method according to any one of claims 1 to 3, The symmetric transistor is a bipolar junction transistor or a field effect transistor, characterized in that the oscillator core using a capacitor common terminal for frequency multiplication. An oscillator core comprising an LC resonator for determining an oscillation frequency and a transistor network in which a pair of symmetric transistors are differentially coupled to compensate for the loss of the LC resonator, A capacitor common terminal for frequency multiplication is characterized in that a capacitor is commonly connected to a base terminal of the symmetric transistor to form a virtual ground capacitor common terminal, and generates twice the frequency output power from the virtual ground capacitor common terminal. Oscillator Core Used. An oscillator core comprising an LC resonator for determining an oscillation frequency and a transistor network in which a pair of symmetrical transistors are cross-coupled in a positive feedback structure to generate a negative resistance component to compensate for the loss of the LC resonator, And a resistor connected to the base terminal of the symmetric transistor in common to form a virtual ground resistor common terminal, and generating twice the frequency output power from the virtual ground resistor common terminal.

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