KR20150134149A

KR20150134149A - Differential colpitts oscillstor

Info

Publication number: KR20150134149A
Application number: KR1020140061140A
Authority: KR
Inventors: 이재성; 김남형
Original assignee: 고려대학교 산학협력단
Priority date: 2014-05-21
Filing date: 2014-05-21
Publication date: 2015-12-01

Abstract

The present invention relates to a differential C-Pitch oscillator in which a C-Pitch oscillator having a gate-drain feedback structure is implemented differentially.
A differential Coulchitz oscillator according to an embodiment of the present invention includes: a first load connected between a first gate and a first drain; And a second load coupled to the first load, the second load being coupled between the second gate and the second drain.

Description

[0001] DIFFERENTIAL COLPITTS OSCILLSTOR [0002]

The present invention relates to a differential C-Pitch oscillator, and more particularly, to a differential C-Pitch oscillator in which a C-Pitch oscillator having a gate-drain return structure is implemented in a differential manner.

A voltage-controlled oscillator (VCO) is a circuit that can change the frequency of an oscillation signal according to an externally applied voltage, and is used as an important component in a wireless transceiver.

Among these voltage-controlled oscillators, the LC-type voltage-controlled oscillator is an oscillator using a negative resistance (-gm) according to the positive feedback of the circuit. In this oscillator, the oscillation frequency can be controlled by controlling the capacitance value existing on the circuit through the control signal.

As an LC-type voltage-controlled oscillator, a voice conductance LC oscillator using negative resistance characteristics according to positive feedback by a transistor is widely known.

An oscillator that operates differentially to an RF transceiver for communication is responsible for generating the carrier frequency. In this case, since the phase noise characteristic of the Colpitts oscillator is superior to that of the LC cross-coupled oscillator, a Colpitts oscillator is preferred at high frequencies. A related prior art document is 10-1043418.

Generally, in order to implement a differential of a Colpitts oscillator, an LC cross-coupled negative return structure is used. Due to the LC cross coupling method, the oscillation frequency of the oscillator greatly decreases due to the parasitic component in the transistor.

Therefore, it is necessary to study the oscillator with improved phase noise characteristics and reduced operating frequency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a differential C-PITZ oscillator in which phase noise characteristics and operating frequency drop portions are improved while securing a differential implementation.

According to an aspect of the present invention, there is provided a semiconductor device comprising: a first load connected between a first gate and a first drain; And a second load coupled to the first load, the second load being coupled between a second gate and a second drain.

The differential COFs oscillator according to an embodiment of the present invention can realize a differential implementation, improve the phase noise characteristic, and minimize the operating frequency drop loss.

1 is a circuit diagram of a Colpitts oscillator of a gate-drain feedback structure employed in a differential C-Pitch oscillator according to an embodiment of the present invention.
2 is another C-Fitz circuit diagram for comparison with the circuit diagram of the Colpitts oscillator of FIG.
FIG. 3 is a graph showing the results of experiments on the negative resistance in the circuit diagrams of FIGS. 1 and 2. FIG.
4 is a graph showing voltage phases at both ends of the gate and drain in the circuit diagram of Fig.
5 is a diagram illustrating a state in which a differential voltage that is opposite in phase to an input and an output of a transmission line coupler according to an embodiment of the present invention is applied.
FIG. 6 is a graph showing a result of simulating the magnitude of the voltage applied to the input and output terminals according to the voltage phase difference between the input and the output when the same power is applied to the input and the output, respectively, in the situation shown in FIG.
7 is a differential C-Pitch oscillator according to one embodiment of the present invention.
8 is an oscillator for comparison with Fig.
Fig. 9 shows the operating frequencies of the oscillators of Figs. 1, 2, 7 and 8 under the same conditions.
Fig. 10 shows the negative resistance of Figs. 7 and 8. Fig.
11 is a graph showing the satellite noise characteristics of Figs. 7 and 8. Fig.

Hereinafter, a differential C-Pitch oscillator according to an embodiment of the present invention will be described with reference to the drawings.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this specification, the terms "comprising ", or" comprising ", etc. should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

1 is a circuit diagram of a Colpitts oscillator of a gate-drain feedback structure adopted in a differential C-Pitch oscillator according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a C- to be.

The colpitts oscillator of FIG. 1 has a structure in which a load L is connected between a gate and a drain, whereas an oscillator of FIG. 2 has a structure in which a load L is connected only to a gate.

The Colpitts oscillator of FIG. 1 is a Colpitts oscillator circuit having a structure in which a load L is connected between a gate and a drain. The admittance at node a1 of the corresponding Colpitts oscillator circuit is expressed by the following equation (1).

Where gm is the transconductance, w is 2 * pi * freq, freq is the operating frequency and L is the impedance of the inductor acting as a load. The inductor may be replaced with a microstrip line. C1 and C2 are capacitors.

In Equation (1), the impedance in the oscillation condition is calculated as follows.

The structure of FIG. 2 is generally used because a bias can be applied to the gate and the drain separately. 1 and 2, the values of C1 and C2 are the same.

According to the calculation of Equation (2), it can be seen that when the load inductor of the Colpitts oscillator is connected only to the drain (FIG. 2), the relative negative resistance is improved. As shown in FIG. 2, when the inductor is connected to the drain of the load inductor only and the inductor is connected to the gate-drain feedback structure of FIG. 1, the simulation result of the negative resistance is as shown in FIG. 3 and the performance is improved in the structure of FIG. have.

As shown, Figure 3 (a) shows the negative resistance of Figure 1, with a value of about -57.91 ohm. Also, Fig. 3 (b) shows the negative resistance of Fig. 2, and its value is about -737.4 ohm. It can be seen from FIG. 1 that the negative resistance is improved as compared with FIG. The closer the value of negative resistance is to zero, the better the oscillation is. Therefore, it can be said that the colpitts oscillator of FIG. 1 oscillates more easily than the colpitts oscillator of FIG. 2.

4 is a graph showing voltage phases at both ends of the gate and drain in the circuit diagram of Fig.

As shown, FIG. 4 shows that the voltage phase at both ends of the gate-drain is reversed on the Colpitts oscillator of the gate-drain feedback structure and the voltage levels are similar.

5 is a diagram illustrating a state in which a differential voltage that is opposite in phase to an input and an output of a transmission line coupler according to an embodiment of the present invention is applied.

Input 1 (in1) and input 2 (in2) have a phase difference of 180 degrees. When the same power is applied to the input and the output, the magnitude of the voltage applied to the actual input and the output is simulated according to the voltage phase difference between the input and output as shown in FIG.

FIG. 6 is a graph showing a result of simulating the magnitude of the voltage applied to the input and output terminals according to the voltage phase difference between the input and the output when the same power is applied to the input and the output, respectively, in the situation shown in FIG.

According to FIG. 6, when a signal having a phase difference of 0 degrees and 180 degrees is applied to the input and the output, the voltage magnitude between the input and the output is the same, and when the phase difference is 0 degree, Able to know.

By using the results of FIG. 5 and FIG. 6 and employing the circuit diagram of FIG. 1, a differential COFs oscillator as shown in FIG. 7 can be implemented.

7 is a differential C-Pitch oscillator according to one embodiment of the present invention.

FIG. 7 is a circuit using a transmission line as a load between the gate and the drain of the gate-drain feedback structure of FIG. 1 and applying the transmission line coupling as shown in FIG. The colpitts oscillator of FIG. 7 includes a first rod L1 and a second rod L2 magnetically coupled to the first rod L1. The first load L1 is connected to the drain and gate of the first transistor M1 and the second load L2 is connected to the drain and gate of the second transistor M2.

The Colpitts circuit including the first rod L1 and the Colpitts circuit including the second rod L2 are symmetrical to each other in the mirror image. The upper end of the first load L1 is connected to the drain of the first transistor M1 and the lower end of the first load L1 is connected to the gate of the first transistor M1. The upper end of the second load L2 is connected to the gate of the second transistor M2 and the lower end of the second load L2 is connected to the drain of the second transistor M2.

The phase applied to the upper input terminal of the first rod L1 and the phase applied to the upper input terminal of the second rod L2 have phases opposite to each other. Of course, the phase applied to the lower input end of the first rod L1 and the phase applied to the lower input end of the second rod L2 have opposite phases to each other.

As shown in FIG. 5, when a phase difference of 0 degrees between the input and the output is applied, the maximum voltage is applied between the transmission line couplers. Thus, if the circuit is configured as shown in FIG. 7 by inverting b and b_bar of the output portion, The Colpitts oscillator is implemented as a differential, and a negative feedback circuit is formed between them to improve the negative resistance and the phase noise characteristic.

8 is an oscillator for comparison with Fig. FIG. 8 shows a structure in which the Colpitts circuit of FIG. 2 is coupled.

Fig. 9 shows the operating frequencies of the oscillators of Figs. 1, 2, 7 and 8 under the same conditions.

As shown in FIG. 9, in the case of FIGS. 2 and 8 (in the case of a general differential C-Pitch oscillator), the operating frequency has dropped by 35.5%. However, in the case of FIGS. 1 and 7 (in the case of a differential C- The operating frequency is reduced by 28.2%, which is about 7% of the normal structure.

Fig. 10 shows the negative resistance of Figs. 7 and 8. Fig.

Fig. 10 (a) shows the negative resistance in Fig. 7, and Fig. 10 (b) shows the negative resistance in Fig. That is, FIG. 7 shows the negative resistance characteristic when the operating frequency is the same as that of FIG. 7 according to an embodiment of the present invention. In the case of the negative resistance, the smaller the value, the more advantageous the initial oscillation condition (start-up). FIG. 10 shows that the structure of FIG. 7 is improved by about 16.3% in the negative resistance compared to the conventional structure (FIG. 8), and the initial oscillation condition is advantageous.

11 is a graph showing the satellite noise characteristics of Figs. 7 and 8. Fig.

Fig. 11 shows the phase noise characteristics of Figs. 7 and 8 under the same condition as Fig.

FIG. 11 shows that the structure of FIG. 7 is improved by about 2 to 3 dB compared to the general structure (FIG. 8 structure) in phase noise.

The above-described differential Coulchitz oscillator is not limited in the configuration and the method of the above-described embodiments, but the embodiments may be modified such that all or some of the embodiments are selectively combined .

L: Load
C: Capacitor
M: transistor

Claims

A first load coupled between the first gate and the first drain; And
And a second load coupled to the first load, the second load being coupled between a second gate and a second drain.

The method according to claim 1,
Wherein the first gate and the first drain have a phase difference of 180 degrees and the second gate and the second drain have a phase difference of 180 degrees.

The method according to claim 1,
And the first rod and the second rod are magnetically coupled.

The method according to claim 1,
Wherein a phase applied to a first input of the first rod and a phase applied to a second input of the second rod are opposite in phase, the first input and the second input being positioned symmetrically with respect to each other Differential Coulisz oscillator with a differential.

2. The apparatus of claim 1, wherein the first rod and the second rod
An inductor, and an inductor and a microstrip.