KR20010000129A - Dual-band voltage controlled oscillator by using variable resonant circuit - Google Patents

Abstract

PURPOSE: A dual-band VCO(voltage controlled oscillator) with a variable resonator is provided to reduce the entire size of a circuit and to have the exact dual-band frequency by switching characteristics of a transistor by outputting the dual-band frequency variably through a single variable resonator and an oscillator. 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-Operated Oscillator Using Variable Resonator {DUAL-BAND VOLTAGE CONTROLLED OSCILLATOR BY USING VARIABLE RESONANT CIRCUIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator having a dual band, and in particular, a dual band voltage controlled oscillator using a variable resonator which stably outputs a variable frequency signal in a dual band through a diode switch circuit. It is about.

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, there is a problem that the varistor diode switch connecting the middle of the microstrip does not work at all when the impedance of the microstrip inductor is larger than the impedance of the microstrip inductor.

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.

An object 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 diode switch circuit to reduce the overall circuit size by a simple circuit implementation The present invention provides a dual band voltage controlled oscillator using a variable resonator which can be reduced and secure an accurate dual band frequency by switching characteristics of a transistor.

The present invention for achieving the above object is a dual-band voltage controlled oscillator using a variable resonator, a variable resonator for resonating in any one of the variable frequency band of the dual band, the oscillator for oscillating the frequency of the variable resonator; And a dual band frequency selection unit having an amplifier for amplifying and outputting an oscillation signal of the oscillator and a diode 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 dual band voltage controlled oscillator using the variable resonator of the present invention, the variable resonator includes a first capacitor and an inductor connected in parallel to a predetermined voltage terminal to determine the first frequency band, and the first frequency to determine the second frequency band. And a second capacitor connected in parallel to the capacitor.

In the dual band voltage controlled oscillator using the variable resonator of the present invention, the dual band frequency selector includes an inductor connected in series to a switching signal terminal, a capacitor connected in parallel thereto, and a diode forward connected between the inductor and the ground terminal. The second capacitor is connected to the diode and is turned on / off according to the level of the switching signal to be further connected / removed in parallel to the first capacitor of the variable resonance part.

In the dual band voltage controlled oscillator using the variable resonator of the present invention, the voltage controlled oscillator is preferably manufactured by either a monolithic microwave integrated circuit (MMIC) or a mixed integrated circuit (HIC).

1 is a circuit diagram of a dual band voltage controlled oscillator using a variable resonator according to an embodiment of the present invention;

2A and 2B are graphs showing oscillation frequency and phase noise, respectively, when the dual band frequency selection unit is switched off in a dual band voltage controlled oscillator using the variable resonance unit of the present invention;

3A and 3B are graphs showing oscillation frequency and phase noise, respectively, when the dual band frequency selection unit is switched on in a dual band voltage controlled oscillator 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 using a variable resonator according to an embodiment of the present invention.

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

In the exemplary embodiment of the present invention, the variable resonator 10 includes the first capacitor C1 and the first inductor L1 connected in parallel to determine the first frequency band, and the capacitor C1 to determine the second frequency band. ) Includes a second capacitor C2 connected in parallel. In addition, the variable resonator 10 includes a resistor R1 and a third capacitor C3 connected in parallel to the control voltage terminal Vt, and first and second inductors L1 connected in parallel to the third capacitor C3. , L2, a varactor C4 and a fourth capacitor 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. It is composed of

Here, the varactor C4 generates a corresponding capacitance value according to the DC voltage change of the control voltage terminal Vt. The second inductor L2 prevents AC noise from entering the resonant circuit and prevents the oscillation signal from going to the control voltage terminal Vt. In addition, the varactor C4 and the remaining capacitors C1, C5, and C6 are used to precisely adjust the frequency band and determine the resonance frequency together with the first inductor L1. In addition, the third capacitor C3 causes the AC noise component of the control voltage Vt to disappear to the ground terminal.

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

The amplifier 30 is an inductor connected in parallel to the third bias resistor R4 and the third bias resistor R4 connected between the first bias resistor R2 and the power supply terminal Vcc of the oscillator 20. (L3), and a second collector connected to the inductor L3, a base connected to the connection node of the first and third bias resistors, and an emitter connected to the collector of the first transistor Q1 of the oscillator 20. A transistor Q2, a capacitor C11 connected between the collector and the ground terminal of the second transistor, and a capacitor C12 connected in parallel to the capacitor and outputting an output frequency. 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 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 an inductor L4 connected in series with the switching signal terminal Vsw, a capacitor C13 connected in parallel with the inductor L4, and a forward direction between the inductor L4 and the ground terminal. It consists of a connected diode D1. The inductor L4 blocks the AC noise component of the switch and prevents the oscillation signal from being grounded to the switch and disappears. The capacitor C13 causes the AC noise component to be grounded and extinguished. In addition, the diode D1 which plays the most important role of the present invention is turned on / off according to the level of the switching signal Vsw to parallel the value of the second capacitor C2 of the resonator 10 with the first capacitor C1. Add or don't.

The dual band voltage controlled oscillator using the variable resonator of the present invention configured as described above operates as follows.

First, when the switching signal Vsw becomes low in the dual band frequency selector 40 and the diode is turned off, the variable resonator 10 may exclude the first capacitor C1 except for the second capacitor C2, The resonant frequency is generated in the first frequency band (about 2.3 GHz) determined by the varactors C4 through the fifth and sixth capacitors C5 and C6 and the first inductor L1.

Thus, when the first transistor Q1 is turned on in response to the signal applied through the C6 capacitor, the oscillator 20 generates a negative resistance value through the bias capacitor C9, the sixth capacitor C7, and the resistor R5. The oscillation occurs in the first frequency band (about 2.3 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 a frequency in a first frequency band (about 2.3 GHz).

On the contrary, when the switching signal Vsw becomes high level in the dual band frequency selector 40 and the diode is turned on, the variable resonator 10 adds the second capacitor C2 in parallel to the first capacitor C1. And generates a resonant frequency in the second frequency band (about 2 GHz) determined by the varactor C4, the remaining capacitors C1, C5, C6, and the first inductor L1. At this time, when the diode is turned on, the values of the second capacitor C2 and the first capacitor C1 are added, so that the resonance frequency is lower than the first frequency band (about 2.3 GHz) when the diode is turned off.

Accordingly, the oscillator 20 and the amplification unit 30 operate the same oscillation and amplification as described above, and eventually output the frequency of the second frequency band (about 2 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 diode D1 is turned on or off in response to 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 the first or second frequency band. That is, when the diode D1 is turned off, the variable resonator 10 ignores the second capacitor C2 so that there is no change in the impedance value, and the LC resonant frequency is determined by the first capacitor C1 and the first inductor L1. Denotes a first frequency band (about 2.3 GHz). On the other hand, when the diode D1 is turned on, the LC capacitor frequency is lowered to the second frequency band (about 2 GHz) by selectively connecting the second capacitor C2 in parallel with the first capacitor C1 so that the impedance value is changed.

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 showing oscillation frequency and phase noise when the dual band frequency selector is switched off in the dual band voltage controlled oscillator using the variable resonance unit of the present invention, respectively. Referring to this, the dual band voltage controlled oscillator using the variable resonator according to the present invention sets the oscillation frequency to about 2.296 GHz when the switch is turned off.

3A and 3B are graphs illustrating oscillation frequency and phase noise when the dual band frequency selector is switched on in the dual band voltage controlled oscillator using the variable resonance unit of the present invention, respectively. Referring to this, the dual band voltage controlled oscillator of the present invention sets the oscillation frequency to about 2.020 GHz when the switch is turned on.

Accordingly, the dual band voltage controlled oscillator according to the present invention generates resonance frequencies of different dual bands because the impedance value for determining the variable frequency band is changed by a capacitor coupled in parallel according to the turn-on / turn-off of the diode.

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 diode. Implementation and control of the dual band oscillator is simplified.

For this reason, when the present invention is applied to a wireless communication system serving different frequency bands, the device can be miniaturized and the power consumption can be greatly reduced.

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 And a dual band frequency selector having a diode which is turned on / off to select any one of the variable frequency bands set by the variable resonator in response to a switching signal. 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. The method of claim 1 or 2, wherein the dual band frequency selection unit, And an inductor connected in series to a switching signal terminal, a capacitor connected in parallel thereto, and a diode connected forward between the inductor and the ground terminal. The method of claim 2 or 3, wherein the second capacitor, And a diode connected to the diode and turned on / off according to the level of the switching signal to be further connected / removed in parallel to the first capacitor of the variable resonance part. The oscillator of claim 1, wherein the voltage controlled oscillator A dual band voltage controlled oscillator using a variable resonator, characterized in that it is made of either monolithic microwave integrated circuit (MMIC) or mixed integrated circuit (HIC).