KR20070068102A - Voltage controlled oscillator circuit - Google Patents

Abstract

The present invention relates to a voltage controlled oscillator (VCO) circuit, and a voltage controlled oscillator (VCO) circuit according to the present invention comprises: a power supply unit for supplying power; A resonator configured to receive power from the power supply unit to generate a reference frequency signal and to provide the reference frequency signal to a baseband unit of the wireless transmission / reception system; And a filter unit connected between the power supply unit and the resonator unit and filtering phase noise of the power supply unit.

According to the present invention, by removing the phase noise of the voltage oscillator circuit power supply portion, the spurious characteristics, the single tone desensitization (STD) characteristics, and the inter-modulation distortion (IMD) characteristics of the receiving side of the wireless transmission / reception system are improved, and thus the reception sensitivity is improved. Is improved, and there is an effect of stably supplying power to a receiver without the influence of an external power source.

In addition, the voltage controlled oscillator circuit is included in the receiving end of the wireless transmission / reception system implemented as the front end module, thereby providing a stable reference frequency signal and minimizing the size of the front end module product.

Description

Voltage controlled oscillator circuit

1 is a block circuit diagram schematically showing the components of a conventional CDMA mobile communication terminal.

2 is a block diagram schematically illustrating a connection configuration of a conventional Temperature Compensated X-tal Oscillator (TCXO) circuit, a phase synchronization circuit, and a voltage controlled oscillator circuit.

3 is a circuit diagram illustrating a structure of a conventional voltage controlled oscillator circuit power supply unit.

4 is a block diagram schematically illustrating a connection configuration of a TCXO circuit, a phase synchronization circuit, and a voltage controlled oscillator circuit according to an embodiment of the present invention.

5 is a circuit diagram showing components of a voltage controlled oscillator circuit according to an embodiment of the present invention.

6 is a graph showing waveforms of an oscillation signal processed in a resonator according to an exemplary embodiment of the present invention.

7 is an enlarged graph illustrating an oscillation signal processed in a resonance unit of a voltage controlled oscillator circuit according to a conventional embodiment.

8 is an enlarged graph illustrating an oscillation signal processed in a resonance unit of a voltage controlled oscillator circuit according to an exemplary embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

700: voltage controlled oscillator circuit 710: resonator

720: filter unit 730: power unit

The present invention relates to a voltage controlled oscillator (VCO) circuit.

Recently, the development of wireless transmission and reception systems including mobile phones is accelerating. In other words, in the early days, the wireless transmission / reception system used to make a call with the other party and transmit a simple short message (SMS), but now it provides a video-on-demand (VOD) service that provides a large broadcast program or a movie, You can take a picture, record a video like a camcorder, and send a picture or video to the other party.

As described above, the wireless transmission / reception system needs to include a device capable of performing each function as various functions are added in addition to voice calls, which increases the overall size of the wireless transmission / reception system.

However, since the wireless transmit / receive system should be convenient to carry while performing various functions, the miniaturization of the wireless transmit / receive system and improvement of reception performance are required.

Therefore, a wireless transceiver system implemented as a front end module capable of performing various functions together with a miniaturization of a circuit configuration or a chip performing each function has been developed. In the case of a wireless transmission / reception system, there is a problem in that power cannot be stably supplied due to interference.

In particular, the power source noise component of the voltage controlled oscillator circuit, which greatly affects the reception performance, has a lot of effects on the receiving end of the wireless transmission / reception system.

Hereinafter, a representative CDMA mobile communication terminal among wireless transmission / reception systems will be described.

1 is a block circuit diagram schematically showing the components of a conventional CDMA mobile communication terminal.

Referring to FIG. 1, a conventional CDMA mobile communication terminal 1000 includes a baseband unit 100, a signal processing unit 200, a front end unit 300, a GPS unit 400, and a TCXO 500.

First, the baseband unit 100 processes an input signal received from the signal processing unit 200, and transmits the processed digital signal to the signal processing unit 200.

The signal processor 200 includes a receiver side signal processor 240 and a transmitter side signal processor 220.

The transmitter side signal processor 220 includes a plurality of amplifiers 221, 222, 224, and 225, frequency mixers 223 and 226, a transmitter side voltage controlled oscillator circuit 227, a transmitter side phase synchronizer circuit 228, and a receiver side. A phase synchronization circuit 229 is provided, and converts the digital signal received from the baseband unit 100 into an RF signal.

The receiver side signal processor 240 includes an LPF 245, a receiver side voltage controlled oscillator circuit 241, a plurality of frequency mixers 242 and 243, and a synthesizer 244, and is received from the front end unit 300. Convert the RF signal to an intermediate frequency signal.

The front end unit 300 includes a transmission BPF 310, a reception BPF 340, a power amplifier 320, a low noise amplifier 350, a duplexer 330, and a diplexer 360, and the baseband. The RF signal received from the end 100 is transmitted through the antenna or the RF signal received from the antenna is transmitted to the signal processor 200.

The GPS unit 400 includes a BPF 430, a low noise amplifier 420, and a frequency mixer 410, and separates only the GPS signal from the RF signal received from the antenna and transmits the GPS signal to the signal processor 200.

However, since the received signal level of the CDMA mobile communication terminal 1000 is moved in a very wide range from -110 dBm to -25 dBm, the power supply unit of the voltage controlled oscillator of the receiving end acts as an important factor affecting the receiving end. In particular, the phase noise of the receiver voltage controlled oscillator circuit is an important factor that greatly affects the sensitivity of the received signal.

2 is a block diagram schematically illustrating a connection configuration of a conventional TCXO (Temperature Compensated X-tal Oscillator) circuit, a phase synchronization circuit, and a voltage controlled oscillator circuit.

2, the voltage controlled oscillator circuit 241 is a circuit for providing a reference frequency signal to the baseband unit 100 of the mobile communication terminal. The reference frequency signal is used for synthesizing an intermediate frequency signal.

However, for example, the reference frequency signal provided by the voltage controlled oscillator circuit 241 may be minutely flowed to become unstable due to a change in external environment such as temperature, and in this case, the intermediate frequency processed by the baseband unit 100. Distortion can occur in the signal.

For this reason, in order to stabilize the reference frequency signal of the voltage controlled oscillator circuit 241, a TCXO circuit 500 and a phase synchronization circuit 229 are provided, and the phase synchronization circuit 229 is provided from the voltage controlled oscillator circuit 241. The reference frequency transmitted to the baseband unit 100 is detected and compared with the oscillation frequency signal provided by the TCXO circuit 500, and a control signal corresponding to the frequency difference is generated and output to the voltage controlled oscillator circuit 241.

Accordingly, when the reference frequency signal flows, the phase synchronization circuit 229 detects this to generate / transfer a control signal, and thus the voltage controlled oscillator circuit 241 may maintain a stable output of the reference frequency according to the control signal.

However, when the power supply unit 241b of the voltage controlled oscillator circuit 241 supplies power to the resonator unit 241a, only the TCXO circuit 500 and the phase synchronization circuit 229 are caused by noise components mixed in the power supply. Since the factor cannot be eliminated, a stable reference frequency output may not be maintained.

3 is a circuit diagram exemplarily illustrating a structure of a power supply unit of a conventional voltage controlled oscillator circuit.

Referring to FIG. 3, there is shown a power supply structure of a voltage controlled oscillator (VCO) circuit, in which a DC voltage and a bypass capacitor are connected in parallel.

The voltage controlled oscillator circuit is an energy conversion circuit for converting DC power into AC power, and a DC voltage is connected to a power supply unit of the voltage controlled oscillator circuit to supply energy to the voltage controlled oscillator circuit.

At this time, the bypass capacitor removes the noise component at the resonance frequency, but only the noise component of the specific frequency band is removed, which is insufficient to improve the phase noise of the power supply unit.

In general, the configuration and function of the CDMA mobile communication terminal 1000 are as described above, and the reference frequency signal transmitted from the voltage controlled oscillator is required when the signal processing unit 200 converts the RF signal into an intermediate frequency signal. .

However, when the voltage-controlled oscillator circuit is implemented as a single module, there is a high probability that phase noise is mixed, which is a major cause of deteriorating the receiver performance. In particular, when a wireless transmission / reception system is implemented as a single module, there is a problem in that phase noise of a power source becomes serious.

In other words, in the case of a wireless transmission / reception system implemented with a single module, there is a need to configure a circuit for supplying stable power to a voltage controlled oscillator as a single module as a factor in which performance and size are in conflict.

Accordingly, the present invention provides a power stage structure for effectively removing phase noise components of a voltage controlled oscillator (VCO) circuit power source in a wireless transmit / receive system implemented as a front end module. The purpose.

In order to achieve the above object, the voltage controlled oscillator (VCO) circuit according to the present invention relates to a wireless transmission and reception system, a power supply for supplying power; A resonator configured to receive power from the power supply unit to generate a reference frequency signal and to provide the reference frequency signal to a baseband unit of the wireless transmission / reception system; And a filter unit connected between the power supply unit and the resonator unit to filter phase noise of the power supply unit.

In order to achieve the above object, the front end module according to the present invention relates to a wireless transmission and reception system, a power supply for supplying power; A resonator configured to receive power from the power supply unit to generate a reference frequency signal and to provide the reference frequency signal to a baseband unit of the wireless transmission / reception system; And a filter unit connected between the power supply unit and the resonator unit to filter phase noise of the power supply unit.

Hereinafter, a voltage controlled oscillator circuit according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The voltage controlled oscillator circuit will be applied to a CDMA mobile communication terminal.

4 is a block diagram schematically illustrating a connection configuration of a TCXO circuit 500, a phase locked circuit (Rx PLL) 600, and a voltage controlled oscillator circuit 700 according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the voltage controlled oscillator circuit 700 is a circuit for providing a reference frequency signal to the base band unit 800 of the mobile communication terminal, and includes a resonator 710, a filter 720, and a power supply 730. It is provided.

Since the reference frequency signal transmitted from the voltage controlled oscillator circuit 700 is used for synthesis of intermediate frequencies in the baseband unit 800 of the mobile communication terminal, the voltage controlled oscillator circuit 700 must deliver a stable signal.

However, the reference frequency signal provided by the voltage controlled oscillator circuit 700 may be in an unstable state due to external environmental change factors such as temperature and noise components generated when power is supplied from the power supply unit 730. In this case, distortion may occur in the intermediate frequency signal processed by the baseband unit 800.

Therefore, in order to deliver a stable reference frequency signal, it is necessary to improve external factors such as temperature and phase noise of the power supply unit 730.

First, the TCXO circuit 500 and the phase synchronization circuit 600 are provided to stabilize the reference frequency signal of the voltage controlled oscillator circuit 700 by removing external environmental change factors such as temperature. The phase synchronization circuit 600 ) Detects a reference frequency signal transmitted from the voltage controlled oscillator circuit 700 to the baseband unit 800 and compares it with the oscillation frequency signal provided from the TCXO circuit 500, and generates a control signal corresponding to the frequency difference. Output to the voltage controlled oscillator circuit 700.

Therefore, when the reference frequency signal flows, the phase synchronization circuit 600 detects this to generate / transfer a control signal, so that the voltage controlled oscillator circuit 700 can maintain a stable output of the reference frequency according to the control signal.

The TCXO circuit 500 is a device for controlling the frequency disturbance according to the temperature change in the crystal oscillator. The TCXO circuit 500 provides an oscillation frequency signal having a constant value of frequency to the temperature change to the phase synchronization circuit 600.

Mainly, the TCXO circuit 500 oscillates a fixed fixed frequency signal over 2.5 ppm even in a large temperature change (usually, minus 30 degrees to 75 degrees).

The phase synchronization circuit 600 includes a frequency detector 610, a divider 620, a charge pump 630, and a loop filter 640.

The frequency detector 610 receives an oscillation frequency signal from the TCXO circuit 500 and detects and compares a reference frequency signal output from the voltage controlled oscillator circuit 700.

In general, the reference frequency signal provided by the voltage controlled oscillator circuit 700 is a high frequency signal (for example, a frequency signal in "㎓") signal, and the oscillation frequency signal provided by the TCXO circuit 500 is compared to the reference frequency signal. Relatively low frequency signals (e.g., frequency signals in " MHz ").

Therefore, in order to compare the frequency of the reference frequency signal and the oscillation frequency signal, the frequency detector 610 needs to convert the reference frequency signal to a relatively low frequency through the divider 620.

For example, if the TCXO circuit 500 provides an oscillation frequency signal of 100 MHz and the voltage controlled oscillator circuit 700 provides a reference frequency signal of 1.1 kHz, the divider divides the reference frequency signal by 1/10. The signal is converted into a signal of comparable units.

The frequency detector 610 compares the frequency of the oscillation frequency signal and the converted reference frequency signal and transfers a control signal corresponding to the frequency difference to the charge pump 630, and the charge pump 630 supplies a current value according to the control signal. Adjust

According to the above example, the 100 MHz oscillation frequency signal of the TCXO circuit 500 is compared with the converted 110 MHz reference frequency signal, and the frequency detector 610 corresponds to the difference between the oscillation frequency signal and the reference frequency signal, that is, the difference of 10 MHz. A control signal having a current amount to be generated is generated.

The charge pump 630 is an electronic circuit that supplies or absorbs a certain amount of charge according to a control signal.

That is, the charge pump 630 supplies a specific amount of charge to the loop filter 640 by a branch circuit when the voltage of the reference frequency signal is greater than that of the oscillation frequency signal, and the voltage of the reference frequency signal is smaller than that of the oscillation frequency signal. If a small amount of charge is drawn from the low pass filter 640, the branch circuit draws a certain amount of charge from the low pass filter 640.

The control signal whose current amount is adjusted according to the control signal is transmitted to the low pass filter 640. For example, a secondary filter including two capacitors and one resistor may be used.

The capacitor connected in parallel with the resistor adjusts the amount of charge and push of the charge pump 630 to adjust the voltage of the voltage controlled oscillator circuit 700 and to reduce the spurious characteristics generated in the phase synchronization circuit 600. .

In general, the frequency detector 610, the divider 620, and the charge pump 630 of the reception phase synchronizer 600 are arranged on a transmitting chip, and the low pass filter 640 receives the received signal. May be placed on a chip.

Next, when the voltage controlled oscillator circuit 700 is implemented as a front end module, it is necessary to improve phase noise of the power supply unit 730 since the probability of mixing phase noise increases and thus affects reception performance.

In order to improve phase noise of the power supply unit 730, the filter unit 720 is provided between the power supply unit 730 and the resonator unit 710, and the filter unit 720 is connected to the power supply unit 730. When power is supplied to the resonator 710, phase components are removed through a capacitor.

Accordingly, the voltage controlled oscillator circuit 700 may provide a stable reference frequency to the baseband unit 800 by receiving power having improved phase noise from the power supply unit 730.

In the CDMA mobile communication terminal of the present invention, the frequency detector 610, the divider 620, and the charge pump 630, which are components of the phase-side phase synchronization circuit 600, may be included in the transmission chip of the CDMA mobile communication terminal. have.

However, the reception level of the CDMA mobile communication terminal is in a very wide range of -110dBm to -25dBm, and the noise component of the receiver side voltage controlled oscillator circuit 700 greatly affects the reception performance.

Hereinafter, a structure for improving the noise component of the voltage controlled oscillator circuit 700 will be described.

5 is a circuit diagram illustrating components of the voltage controlled oscillator circuit 700 according to an embodiment of the present invention.

Referring to FIG. 5, the voltage controlled oscillator circuit 700 generates a reference frequency signal by receiving power from a power supply unit 730 for supplying power and the power supply unit 730, and converts the reference frequency signal into a base of a CDMA mobile communication terminal. And a filter unit 720 connected between the power supply unit 730 and the resonance unit 710 and filtering phase noise of the power supply.

First, the power supply unit 730 is connected to the DC power supply terminal of the mobile communication terminal to supply energy to the voltage controlled oscillator circuit 700, the power supply unit 730 is provided with a bypass capacitor connected in parallel with the DC power supply power supply noise Remove the ingredients.

The filter unit 720 is provided with at least one filter stage including a resistor and a capacitor connected in parallel. The filter unit 720 improves phase noise of the power supplied from the power source unit 730.

For example, the filter unit 720 includes a first filter stage composed of a first resistor and a first capacitor connected in parallel, a second filter stage composed of a second resistor and a second capacitor connected in parallel, and two filter stages connected in series. Filter out phase noise over the second order.

The resonator 710 compares the frequency of the oscillation frequency signal provided from the TCXO circuit 500 with the frequency of the reference frequency signal generated by the resonator 710 to generate a control signal according to the frequency difference 600. The resonator 710 receives the control signal and generates a reference frequency signal corresponding to the control signal input from the phase synchronization circuit 600.

In addition, the resonator 710 provides the generated reference frequency signal to the baseband unit. The provided reference frequency signal may be used in a frequency synthesizer.

The power supply unit 730, the resonance unit 710, and the filter unit 720 of the voltage controlled oscillation circuit 700 are embedded in a receiving chip of a CDMA mobile communication terminal, and the resonance unit 710 embedded in the receiving chip is Provides a reference frequency signal to the baseband unit on the receiving side.

The CDMA mobile communication terminal is implemented as a front end module, and the power supply unit 730, the resonator unit 710, and the filter unit 720 are implemented in the front end module.

6 is a graph illustrating waveforms of an oscillation signal processed in a resonator according to an exemplary embodiment of the present invention, and FIG. 7 is an enlarged diagram illustrating an oscillation signal processed in a resonator of a voltage controlled oscillator circuit according to a conventional embodiment. One graph. 8 is an enlarged graph illustrating an oscillation signal processed in a resonator of a voltage controlled oscillator circuit according to an exemplary embodiment of the present invention.

The horizontal axis of each graph represents a frequency band, and the vertical axis represents power.

Referring to FIG. 6, each element constituting the resonator 710 concentrates energy in a region of 1.764 kHz and generates an electrical resonance phenomenon to oscillate a reference frequency signal.

The resonator 710 transmits the reference frequency signal to the base side of the receiver side, which is composed of the movement of charge accumulated in the capacitor C1 shown in FIG.

7 and 8 are enlarged graphs of reference frequency signals in which oscillation occurs, and FIG. 7 is a waveform of an output value of a conventional voltage controlled oscillator 241, and the slope of the graph is -100.83 dBc / Hz.

8 is a waveform of the output value of the voltage controlled oscillator 700 according to the embodiment of the present invention, the slope of the graph is -108.50dBc / Hz (where, when expressing the current signal magnitude for 1mW in dBm, dBc Is a unit representing the magnitude difference of a signal expressed in dBm).

It can be seen that the output waveform of the voltage controlled oscillator according to the present invention is improved by about 8 to 9 dBC / Hz as a result of performing the second phase noise filtering.

The present invention has been described above with reference to the preferred embodiments, which are merely examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

According to the voltage-controlled oscillation circuit according to the present invention, by removing the phase noise of the voltage oscillator circuit power supply portion, the spurious characteristics, the single tone desensitization (STD) characteristics, the inter-modulation distortion (IMD) characteristics of the receiving side of the radio transceiver system. The characteristic is improved, the reception sensitivity is improved, and there is an effect that can stably supply power to the receiver without the influence of external power.

In addition, the voltage controlled oscillator circuit is included in the receiving end of the wireless transmission / reception system implemented as the front end module, thereby providing a stable reference frequency signal and minimizing the size of the front end module product.

Claims (6)

In a wireless transmission and reception system, A power supply unit supplying power; A resonator configured to receive power from the power supply unit to generate a reference frequency signal and to provide the reference frequency signal to a baseband unit of the wireless transmission / reception system; And Voltage controlled oscillator (VCO) circuit connected between the power supply and the resonator including a filter for filtering the phase noise of the power supply. The method of claim 1, wherein the filter unit A voltage controlled oscillator circuit comprising at least one filter stage comprising a resistor and a capacitor. The method of claim 1, wherein the resonator unit It is connected to the phase synchronization circuit for generating a control signal according to the frequency difference by comparing the frequency of the oscillation frequency signal provided from the TCXO (Temperature compensated crystal oscillator) circuit and the reference frequency signal generated in the resonator, input from the phase synchronization circuit A voltage controlled oscillator circuit for generating a reference frequency signal corresponding to the control signal. The method of claim 1, wherein the resonator unit And outputting the reference frequency signal to a frequency synthesizer of the baseband unit. The method of claim 1, The power supply unit, the resonator unit, and the filter unit are embedded in a receiving chip of the wireless transmission / reception system, and the resonance unit embedded in the receiving chip provides a reference frequency signal to a baseband unit on the receiving side. Circuit. In a wireless transmission and reception system, A power supply unit supplying power; A resonator configured to receive power from the power supply unit to generate a reference frequency signal and to provide the reference frequency signal to a baseband unit of the wireless transmission / reception system; And A front end module connected between the power supply unit and the resonator unit and including a filter unit for filtering phase noise of the power supply unit.

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