KR20010000130A - Dual-band voltage controlled oscillator for pcs/imt-2000 application by using variable resonant circuit - Google Patents

Abstract

PURPOSE: A dual-band VCO(voltage controlled oscillator) for application of PCS/IMT-2000(personal communication system/international mobile telecommunication system) with a variable resonator is provided to reduce the entire size of a circuit by outputting dual-band frequency variably through a single variable resonator and an oscillator depending on turning-on/off of a transistor. CONSTITUTION: A diode is turned off by a low-level switching signal of a dual-band frequency selector(40). A variable resonator(10) generates resonance frequency by a first frequency band decided by the other components(C1,C4-6,L1) except a second capacitor(C2). An oscillator(20) generates negative resistance and the first frequency band starts to oscillate when a first transistor(Q1) is turned on. An amplifier(30) amplifies the signal and matches impedance through capacitors(C11,C12). In a high-level switching signal of the dual-band frequency selector(40), the variable resonator(10) adds the second capacitor(C2) parallel to the first(C1) and generates the resonance frequency. The resonance frequency is lower than the first frequency band on turning-off of the diode. Therefore, the oscillator(20) and amplifier(30) output a second frequency band.

Description

DUAL-BAND VOLTAGE CONTROLLED OSCILLATOR FOR PCS / IMT-2000 APPLICATION BY USING VARIABLE RESONANT CIRCUIT}

The present invention relates to a voltage controlled oscillator having a dual-band, in particular PCS / using a variable resonator capable of oscillating the signal in the variable frequency band of the correct dual band through the transistor switch circuit A dual band voltage controlled oscillator for IMT-2000 applications.

As wireless service advances, next-generation digital mobile phones and PCS, as well as next-generation WLL and IMT-2000, will be serviced in the future. This next generation wireless communication service requires various functions such as processing capacity of high capacity data such as image transmission.

These wireless communication services use different frequency bands, for example, 800 MHz band for digital portable telephones, 1.9 GHz band for PCS, 1.8 to 2.1 GHz band for IMT-2000, and 2.2 GHz band for next-generation wireless communication services. do.

It is natural that the RF transceiver of this next generation wireless communication system has a voltage controlled oscillator that provides radio frequency (RF) used in the aforementioned wireless communication service.

Moreover, in the transition period, which is the beginning of the next generation wireless communication service, a function for receiving multiple communication services by one terminal must be required. In order to receive two frequency bands, a dual-band VCO is required to generate an intermediate frequency corresponding to each frequency band.

The dual band oscillator known as the prior art is disclosed and filed by Japan Electric on November 11, 1996, a dual band VCO of Japanese Patent Application Laid-open No. 10-145262. This Japanese Patent Publication VCO connects a switch in the middle of the microstrip inductor in the resonant section, and converts the length of the microstrip inductor at the time of switching on and off to obtain another frequency. It is a technique to convert. However, if the varistor transistor switch connected in the middle of the microstrip is larger than the impedance of the microstrip inductor, there is a problem that it does not work at all.

Another conventional dual band oscillator is disclosed and published by Motorola on August 15, 1997, a dual band voltage controlled oscillator of US Pat. No. 58,21820. This U.S. patent technique uses an oscillator transistor independently to switch on / off complementarily on / off when a different inductor is connected to a resonator to convert the frequency. Since this technique simply binds each oscillator to a switch circuit, it is possible to obtain the desired dual-band oscillation frequency. However, since the switch circuit is a form of two oscillators simply bundled in a physical coupling, the overall circuit size becomes large and the oscillator There was difficulty controlling together.

The purpose of the present invention is to solve the problems of the prior art as described above by varying the frequency of the dual band through one variable resonator and the oscillator according to the on / off of the transistor switch circuit to reduce the overall circuit size by a simple circuit implementation The present invention provides a dual band voltage controlled oscillator for PCS / IMT-2000 applications using a variable resonator.

In order to achieve the above object, the present invention provides a dual band voltage controlled oscillator using a variable resonator, comprising: a variable resonator for resonating to any one frequency band among variable frequencies of a dual band, an oscillator for oscillating a frequency of the variable resonator; And a dual band frequency selector having an amplifier for amplifying and outputting the oscillation signal of the oscillator and a transistor turned on / off to select any one of the variable frequency bands set by the variable resonator in response to the switching signal.

In the present invention, the variable resonator includes a first capacitor and an inductor connected in parallel to a predetermined voltage terminal to determine a first frequency band, and a second capacitor connected in parallel to the first capacitor to determine a second frequency band. Include.

In the present invention, the dual band frequency selector includes a first inductor connected in series to a switching signal terminal, first and second resistors connected in series between the first inductor and a ground terminal, and a second connected to a connection node of the resistor. And an inductor and a transistor driven by the voltage of the second inductor to conduct the first inductor and the ground terminal. In addition, the second capacitor is connected to the transistor and is preferably turned on / off according to the level of the switching signal to be additionally connected / removed in parallel to the first capacitor of the variable resonance part.

In the present invention, the voltage controlled oscillator is characterized in that it is made of any one of monolithic microwave integrated circuit (MMIC) or mixed integrated circuit (HIC).

1 is a circuit diagram of a dual band voltage controlled oscillator for a PCS / IMT-2000 application using a variable resonator according to an embodiment of the present invention;

2A and 2B are graphs respectively showing oscillation frequency and phase noise when a dual band frequency selector is switched on in a dual band voltage controlled oscillator for a PCS / IMT-2000 application using a variable resonance unit of the present invention;

3A and 3B are graphs respectively showing oscillation frequency and phase noise when the dual band frequency selector is switched off in a dual band voltage controlled oscillator for a PCS / IMT-2000 application using the variable resonance unit of the present invention.

<Explanation of symbols for main parts of drawing>

10: variable resonator 20: oscillator

30: amplification unit 40: dual band frequency selection unit

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram of a dual band voltage controlled oscillator for PCS / IMT-2000 application using a variable resonator according to an embodiment of the present invention.

Referring to FIG. 1, the dual band voltage controlled oscillator of the present invention includes a variable resonator 10, an oscillator 20, an amplifier 30, and a dual band frequency selector 40.

In the embodiment of the present invention, the variable resonator 10 includes a first capacitor C1 and a first inductor L1 connected in parallel to determine a first frequency band, and the first capacitor to determine a second frequency band. And a second capacitor C2 connected in parallel to C1. In addition, the variable resonator 10 includes resistors R1 and varactor C4 connected in parallel to the control voltage terminal Vt, and first and second inductors L1 and L2 in parallel with the varactor C4. And third and fourth capacitors C3 and C5 connected in parallel between the first and second inductors L1 and L2, and a fifth capacitor C6 connected in parallel to the first capacitor C1. . Here, the capacitor C3 is for removing the AC noise of the control voltage (Vt) and the second inductor (L2) prevents the AC noise from entering the resonant circuit and at the same time prevents the oscillation signal from passing to the control voltage terminal. Do it. The selector C4 and the remaining capacitors C1, C5, and C6 are for precisely adjusting the frequency band.

The oscillator 20 includes first and second bias resistors R2 and R3 connected in series to C6 of the variable resonator 10 and a base connected to a connection node of the resistor and connected between the emitter and the ground. R5) and bypass capacitor C8 connected in parallel to the first transistor Q1, the sixth and seventh capacitors C7 and C9 connected in parallel to the base of the first transistor Q1, and the first transistor ( And an eighth capacitor C10 connected between the collector of Q1) and ground. Here, the bypass capacitor C8, the sixth capacitor C7, and the resistor R5 generate a negative resistance value to cause oscillation. The capacitor C9 serves as an AC coupling with the DC block.

The amplifier 30 includes a third bias resistor R4 connected between the first bias resistor R2 and the power supply terminal Vcc of the oscillator 20 and a third bias resistor R4 in parallel. A collector is connected to a third inductor L3 and the third inductor L3, a base is connected to a connection node of the first and third bias resistors R2 and R4, and the emitter is a first transistor of the oscillator 20. A second transistor Q2 connected to the collector of Q1, a capacitor C11 connected between the collector of the second transistor and a ground terminal, and a capacitor C12 connected in parallel to the capacitor and outputting an output frequency. It is composed. Here, the third bias resistor R4 serves to match the bias voltage with the first and second bias resistors R2 and R3 of the oscillator 20. The third inductor L3 serves as an AC blocking function, and the capacitors C11 and C12 connected to the collector of the second transistor Q2 perform impedance matching.

The dual band frequency selector 40 includes a fourth inductor L4 connected in series to the switching signal terminal Vsw, and resistors R6 and R7 connected in series between the fourth inductor L4 and the ground terminal. And a fifth inductor L5 connected to the connection node of the resistor and a transistor Q3 driven by the voltage of the fifth inductor L5 to conduct the fourth inductor L4 and the ground terminal. In this case, the fourth and fifth inductors L4 and L5 are used to prevent the oscillation signal from disappearing, and the resistors R6 and R7 are used as a driving power source of the transistor by voltage-dividing the switching signal. In addition, the transistor Q3, which plays the most important role of the present invention, is turned on / off according to the level of the switching signal Vsw so that the value of the second capacitor C2 of the resonator 10 may be changed from the first capacitor C1. Add or do not add in parallel.

The dual band voltage controlled oscillator for the PCS / IMT-2000 application using the variable resonance unit of the present invention configured as described above operates as follows.

First, when the switching signal Vsw becomes the low level (0V) in the dual band frequency selector 40 and the transistor Q3 is turned off, the variable resonator 10 may exclude the second capacitor C2. The resonance frequency is generated in the first frequency band (about 2.258 GHz) determined by the one capacitor C1, the varactor C4, the remaining capacitors C5 and C6, and the first inductor L1. In fact, when the transistor Q3 is turned off, since the base portion is not completely open, the charging voltage of the second capacitor C2 somewhat affects the impedance of the variable resonator 10, which is the transistor Q3. The size is very small compared to the turned-on state.

Thus, when the first transistor Q1 is turned on in response to a signal applied through the C6 capacitor, the oscillator 20 may have a negative resistance value through the bypass capacitor C8, the sixth capacitor C7, and the resistor R5. The oscillation occurs in the first frequency band (about 2.258 GHz) of the variable resonator 10.

The amplifier 30 amplifies the oscillated signal through the second transistor Q2, which is a common emitter, and corresponds to the bias voltages of the first to third bias resistors R2, R3, and R4. Impedance matching is performed through capacitors C11 and C12 to output the frequency Vo of the first frequency band (about 2.258 GHz).

On the contrary, when the switching signal Vsw becomes a high level (about 2V) in the dual band frequency selector 40 and the transistor Q3 is turned on, the variable resonator 10 converts the second capacitor C2 to the first capacitor. Add in parallel to C1 and generate a resonant frequency in the second frequency band (about 1.706 GHz) determined by the varactor C4 and the remaining capacitors C5 and C6 and the first inductor L1. At this time, when the transistor Q3 is turned on, the values of the second capacitor C2 and the first capacitor C1 are added, so that the resonance frequency is higher than the first frequency band (about 2.258 GHz) when the transistor Q3 is turned off. Lowers.

Accordingly, the oscillator 20 and the amplifier 30 operate the same oscillation and amplification as described above, and eventually output the frequency Vo of the second frequency band (about 1.706 GHz) to the output terminal.

Therefore, in the dual band voltage controlled oscillator using the variable resonator of the present invention, the variable resonator 10 is resonant as the transistor Q3 is turned on or off in accordance with the switching signal Vsw in the dual band frequency selector 40. The impedance value LC for determining the frequency is varied to generate a signal in a first frequency band (about 2.258 GHz) or a second frequency band (about 1.706 GHz). That is, when the transistor Q3 is turned off, the variable resonator 10 disregards the second capacitor C2 so that there is no change in the impedance value, and sets the LC resonance frequency by the first capacitor C1 and the inductor L1. 1 frequency band (approximately 2.258 GHz). On the other hand, when the transistor Q3 is turned on, the LC capacitor frequency is lowered to the second frequency band (about 1.706 GHz) by selectively connecting the second capacitor C2 to the first capacitor C1 so that the impedance value changes.

On the other hand, in order to commercialize the dual band voltage controlled oscillator using the variable resonator of the present invention, it is preferable to manufacture either monolithic microwave integrated circuit (MMIC) or mixed integrated circuit (HIC).

2A and 2B are graphs illustrating oscillation frequency and phase noise when the dual band frequency selector is switched on in the dual band voltage controlled oscillator for the PCS / IMT-2000 application using the variable resonance unit of the present invention. Referring to this, it is shown that the dual band voltage controlled oscillator of the present invention generates an oscillation frequency of about 1.706 GHz when the switch is turned on.

3A and 3B are graphs illustrating oscillation frequency and phase noise when the dual band frequency selector is switched off in the dual band voltage controlled oscillator for the PCS / IMT-2000 application using the variable resonance unit of the present invention. Referring to this, it is shown that the dual band voltage controlled oscillator of the present invention generates an oscillation frequency of about 2.258 GHz when the switch is turned off.

As shown in the graphs, the dual band voltage controlled oscillator of the present invention has a good driving characteristic of the transistor, and thus it is possible to accurately obtain the desired dual band frequency rather than using a diode as a general switch element.

Accordingly, the dual band voltage controlled oscillator according to the present invention is variably changed in impedance by a capacitor coupled in parallel with the turn on / off of the transistor to generate mutually different dual band resonant frequencies.

As described above, the present invention simplifies the oscillator circuit compared to the prior art by selectively outputting a dual band frequency signal through one resonant circuit and an oscillator circuit which variably change the resonant frequency by turning on / off the transistor. Implementation and control of the dual band oscillator is simplified. In addition, the present invention can ensure an accurate double band frequency by the switching characteristics of the transistor.

Therefore, when the present invention is applied to a wireless communication system serving different frequency bands, that is, PCS and IMT-2000 applications, it is possible to achieve a miniaturization of the device while greatly reducing power consumption.

On the other hand, the present invention is not limited to the above-described embodiment, various modifications are possible by those skilled in the art within the spirit and scope of the present invention described in the claims to be described later.

Claims (5)

In a dual band voltage controlled oscillator using a variable resonator, A variable resonator configured to resonate in any one frequency band among variable frequencies of a dual band; An oscillator for oscillating the frequency of the variable resonator; An amplifier for amplifying and outputting an oscillation signal of the oscillator; And PCS / IMT-2000 application using a variable resonator comprising a dual band frequency selector having a transistor turned on / off to select any one of the variable frequency bands set by the variable resonator in response to a switching signal. Dual band voltage controlled oscillator. The method of claim 1, wherein the variable resonator, And a first capacitor and an inductor connected in parallel to a predetermined voltage terminal to determine a first frequency band, and a second capacitor connected in parallel to the first capacitor to determine a second frequency band. Dual band voltage controlled oscillator for PCS / IMT-2000 applications. The method of claim 1 or 2, wherein the dual band frequency selection unit, A first inductor connected in series to a switching signal terminal, first and second resistors connected in series between the first inductor and a ground terminal, a second inductor connected to a connection node of the resistor, and a voltage of the second inductor A dual band voltage controlled oscillator for PCS / IMT-2000 application using a variable resonator, characterized in that it comprises a transistor which is driven by to conduct a first inductor and a ground terminal. The method of claim 2 or 3, wherein the second capacitor, Dual band voltage control for the PCS / IMT-2000 application using the variable resonator, which is connected to the transistor and is turned on / off according to the level of the switching signal and further connected / removed in parallel to the first capacitor of the variable resonator unit. oscillator. The oscillator of claim 1, wherein the voltage controlled oscillator A dual band voltage controlled oscillator for PCS / IMT-2000 application using a variable resonator, characterized in that it is made of monolithic microwave integrated circuit (MMIC) or mixed integrated circuit (HIC).