KR100384243B1 - Phase Noise Enhancement Method for Miniature Voltage Controlled Oscillator composed of Integrated Circuits - Google Patents

Abstract

The present invention dramatically improves the low phase noise characteristics of a chip-type voltage controlled oscillator (VCO) implemented by technologies such as MMIC (Monolithic Microwave Integrated Circuits) or RFIC (Radio Frequency IC). The present invention relates to a method for improving phase noise of an integrated circuit type miniature voltage controlled oscillation device. The present invention is composed of a general PCB or ceramic PCB which is FR4 or epoxy PCB, and has a substrate having a multilayer structure of at least one layer for mounting circuit elements and / or circuit patterns, and SMT (Surface). Oscillating part attached on the substrate in the form of Mounting Technology (Chip-On-Board) or Var-Chip (Varactor Diode) for adjusting oscillation frequency and choke filter for noise reduction And a resonator comprising a microstrip line for determining a resonant frequency and phase noise.

According to the present invention, it is possible to greatly improve the low phase noise characteristic of the existing integrated circuit voltage controlled oscillator and to obtain the advantage of changing the oscillation frequency by laser trimming the external microstrip line. In addition, since it is possible to implement components that are difficult to mount in a chip from outside, chip manufacturing cost can be reduced. In addition, it has the same phase noise characteristics as a voltage controlled oscillator composed of conventional R, L, C, etc., and has a high level of integration. And the volume can be greatly reduced.

Description

Phase Noise Enhancement Method for Miniature Voltage Controlled Oscillator composed of Integrated Circuits}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated circuit type miniature voltage controlled oscillation device for improving phase noise, and more particularly, to a chip type implemented by technologies such as MMIC (Monolithic Microwave Integrated Circuits) or RFIC (Radio Frequency IC). The present invention relates to a method for improving the phase noise of an integrated circuit type miniature voltage controlled oscillator that can significantly improve the low phase noise characteristic of a voltage controlled oscillator (VCO).

With the rapid development of mobile communication technology, the size and weight of the user terminal for ensuring the mobility and portability of the user are decreasing, and the light and small size of the parts used is rapidly being achieved.

The voltage controlled oscillator is the main part of the frequency synthesizer that sets the channel of the transceiver.The output level, phase noise, and harmonic characteristics of the oscillation signal are the RF core parts that directly determine the system sensitivity and operation characteristics. Research on improvement has been made steadily. The voltage controlled oscillator for mobile communication devices was mainly used as a resonator for oscillation until the 1990s, but according to the trend of miniaturization, the Colpitts method in which the resonator is mounted in a multilayer PCB structure is mainly used.

In terms of circuit configuration, a single oscillator structure using a single bipolar transistor is used or a two stage oscillator using a separate buffer amplifier in cascode form for stabilizing output and characteristics is mainly used.

1 is a general circuit diagram of a voltage controlled oscillator, in which a frequency controller 101 is input from a microstrip line (Choke SL) and a control voltage (Vt) stage for a choke filter to block AC noise of an input control voltage. A varactor diode (Cv) having a variable capacitance at both ends according to the control voltage to be formed, and a coupling capacitor (C1) for determining the connection with the resonator 102 and the oscillation frequency variable range.

The resonator 102 is composed of a resonant microscript line SL and a compensation capacitor Cx, and the total equivalent capacitance used in the frequency control unit 101 and the oscillator 103 at the rear end and the like. The resonance frequency is determined by the inductance value of the microscript line SL. Here, the capacitor C2 is a clap capacitor that couples the resonator 102 and the oscillator 103.

The oscillator 103 is composed of two transistors Q1 and Q2 and their peripheral circuits. The transistor Q1 and its peripheral circuits are used for oscillation, and the transistor Q2 and its peripheral circuits are used for the oscillation signal. Used for amplification, they are cascoded.

The base terminal of the transistor Q2 is in a high frequency ground state through a bypass capacitor C5, and is connected to the oscillation transistor Q1 through an emitter terminal to amplify the oscillation signal. have. The power supply voltage (Vcc) terminal is a power supply terminal of the entire voltage controlled oscillator, and is used to cut off the noise of the power supply terminal by using the bypass capacitor (C9) for the power filter. The oscillation output terminal (RFout) outputs an oscillation signal Output terminal.

In the oscillation unit 103, when the transistor Q1 becomes the collector ground, the oscillation condition is satisfied, so the capacitor C6 should be in the high frequency ground state. However, when the capacitance of the capacitor C6 is determined to be fully grounded at high frequency, the oscillation output of the oscillator cannot be transmitted to the transistor Q2, so an appropriate capacitance value of the capacitor C6 should be used. In other words, when the capacitance value of the capacitor C6 is increased, stable oscillation can be obtained, but since the output signal is relatively attenuated, a trade-off of the capacitance value of the capacitor C6 should be taken.

Conventional modular voltage controlled oscillator of the modular structure is the circuit shown in Figure 1 is a resistor (R), inductance (L), capacitor (C), transistor (Q), etc. Although the phase noise characteristics are excellent in the method of assembling above, the size and weight are so large that it cannot cope with the trend of light and small communication devices and the manufacturing cost is high.

In order to overcome such drawbacks, an integrated circuit type voltage controlled oscillator of the MMIC or RFIC type, in which the voltage controlled oscillator circuit of FIG. 1 is mounted in one single chip using semiconductor materials such as SiGe and GaAs, has recently been developed. . This type of product has the advantage that the size and weight of the product can be greatly reduced, and the manufacturing cost is also low.

However, such an integrated circuit type voltage controlled oscillator has a built-in resonator for oscillation inside the chip, so the phase noise characteristics are so poor that it cannot be used in a system requiring a high performance voltage controlled oscillator such as a mobile communication device. It is only partly used for low quality products.

The phase noise characteristic of the oscillator is mainly dependent on the Q (Quality Factor) value of the resonator, and the larger the Q value of the resonator, the better the phase noise characteristic is. In order to increase the Q value of the resonator unit, the Q values of L and C used in the resonator unit must be large, and the Q values of these L and C depend on the resistance components they have. If the L and C elements are mounted in the integrated circuit, the size of the L and C elements becomes small, so that the resistance component increases and the Q value decreases.

In general, the Q value of the capacitor is so large that it does not affect the phase noise characteristics, so it only depends on the Q value of L. In other words, since the integrated circuit type voltage controlled oscillator forms the resonator inductance L by a fine pattern processing in the chip, the Q value is very low, and thus, a voltage controlled oscillator having excellent phase noise characteristics cannot be realized.

On the other hand, the oscillation frequency of the integrated circuit type voltage controlled oscillator depends on the internal component values constituting the oscillator, and there are variations in internal component values in the semiconductor manufacturing process, and accordingly, the oscillation frequency is somewhat different from the target oscillation frequency. . Conventional voltage controlled oscillators adjust such oscillation frequency by laser trimming the microstrip line on the substrate. However, since the resonator of the integrated circuit type voltage controlled oscillator is inside the integrated circuit, the variation of component value generated in the manufacturing process is It has the disadvantage that it cannot adjust the center frequency variation by

In addition, the microstrip line (Choke SL) and the bypass capacitor (C5) (C9) for the choke filter (Choke filter) shown in FIG. 1 have a very large component value and chip size when mounted in an IC chip. Has a disadvantage in that it becomes very large and thus the manufacturing cost increases. Reducing the values of the choke filter microstrip lines (Choke SL) and capacitors (C5) and (C9) in order to reduce manufacturing costs inevitably degrades the phase noise characteristics as well as the RF characteristics such as the oscillation signal output level.

The present invention for overcoming the disadvantages described above can have a great effect on the varactor diode and the microscript line and the MMIC chip size as necessary to determine the phase noise and frequency adjustment characteristics of the voltage controlled oscillator. Integrated circuit for improving phase noise that allows voltage-controlled oscillators in parts other than choke filter microstrip lines and bypass capacitors to be MMIC or RFIC and can be combined with each other on separate boards It is an object of the present invention to provide a miniature voltage controlled oscillation element.

In other words, the present invention implements the low phase noise characteristics of the integrated circuit voltage controlled oscillator by implementing the resonator, the frequency controller and, if necessary, the components having the large component values on the substrate outside the integrated circuit. It is an object of the present invention to provide an integrated circuit type miniature voltage controlled oscillation element for improving phase noise, which greatly improves and finely adjusts the oscillation frequency error by trimming the microstrip line. The purpose is to reduce the cost of the chip.

In addition, the present invention has the same phase noise characteristics as the modular voltage controlled oscillator composed of conventional R, L, C, etc., but also enables high-density product configuration, reducing manufacturing cost and size of the product. The purpose of the present invention is to provide an integrated circuit-type micro voltage controlled oscillation device for improving phase noise, which can greatly reduce weight, volume, and volume.

1 is a circuit diagram illustrating a general voltage controlled oscillator.

2 is a configuration circuit diagram of a voltage controlled oscillator according to the present invention.

3 is an assembly view of the voltage controlled oscillation element according to the present invention.

Figure 4 is a detailed view showing the structure of the microstrip line used in the present invention.

5 is an equivalent circuit diagram of a resonator unit including a microstrip line and a capacitor used in the present invention.

6 is a graph showing the Q value of the microstrip line and the phase noise characteristics according to the present invention.

※ Explanation of code about main part of drawing ※

1 substrate 2 voltage controlled oscillator chip

3: shield plate 4,9: ground plane

5: Circuit Pattern 6: Via (Through Hole)

7: conductor portion 8: dielectric

SL: Microstrip Line Cv: Varactor Diode

An integrated circuit-type micro voltage controlled oscillation device for improving phase noise according to the present invention for achieving the above object includes a substrate having a multilayer structure of one or more layers for mounting a circuit element and / or a circuit pattern; One chip is a voltage-controlled oscillator including an oscillation frequency adjuster composed of varactor diodes and a resonator, oscillator and amplifier except for the resonant microstrip line that determines resonant frequency and phase noise. a voltage controlled oscillator chip integrated in a chip and attached to the substrate, and a microstrip for varactor diode and choke filter attached to a circuit pattern on the substrate to adjust the oscillation frequency of the voltage controlled oscillator An oscillation frequency adjusting unit composed of lines and a resonance frequency of the voltage controlled oscillator printed on the surface of the substrate And a microstrip line for determining phase noise and, if necessary, a large value of components difficult to be mounted in a chip on the substrate.

A routing or solder mask is formed on the substrate so that the circuit elements on the substrate may be mounted and operated in a circuit, and a power line and a control line for operation of the circuit elements mounted on the substrate. And a circuit pattern corresponding to an output line is formed on the substrate, and the routing, solder mask, power line, control line, and output line are connected to the bottom surface of the substrate by vias or through holes. It is electrically connected to a (soldering pad). Here, the substrate may be used as one of FR4, epoxy PCB or ceramic, alumina PCB and the like.

The voltage controlled oscillator chip is preferably formed by MMIC (Monolithic Microwave Integrated Circuits) or RFIC (Radio Frequency Integrated Circuits).

The voltage controlled oscillator chip and varactor diode are preferably attached to the substrate in the form of Surface Mounting Technology (SMT) or Chip-On-Board (COB).

The microstrip line SL may be laser trimmed by a laser beam to finely adjust the oscillation center frequency error, and the choke filter microstrip line CHoke SL may be a substrate. It is preferable to form in the pattern of a phase.

Another embodiment of the present invention is characterized in that a shield plate (shield plate) is further provided for protecting the circuit elements and EMI shielding on the substrate.

Here, it is preferable that the shielding plate and the substrate are combined by soldering and / or high temperature sputtering.

Hereinafter, a preferred embodiment of the present invention will be described in more detail with an exemplary drawing.

As shown in FIG. 2, the integrated circuit-type micro voltage controlled oscillator according to the present invention has a portion indicated by a dotted line in FIG. 2 inside the voltage controlled oscillator chip 2 implemented by a technique such as MMIC or RFIC, that is, a frequency controller and a resonance. The part, oscillator, buffer amplifier, and peripheral circuit elements necessary for the circuit implementation are built in, thereby generating a desired oscillation frequency.

The voltage controlled oscillator chip 2 has a bar for varying the oscillation frequency by the control voltage Vt in addition to the terminals of the control voltage Vt, the power supply voltage Vcc, the oscillation output RFout, and the ground GND. Terminals for connecting the raptor diode Cv and the microstrip line SL for the resonator part are formed. The voltage controlled oscillator chip (2) and the oscillation frequency variable varactor diode (Cv) are connected to the RFIC by a circuit pattern (5) formed on a substrate (1) made of epoxy or ceramic PCB, etc. The SL is formed on the substrate 1 to have a maximum Q value, and components having large component values such as the choke filter microstrip line Choke SL and the capacitors C5 and C9 are also embedded in the chip. Or may be mounted on the substrate 1. If necessary, the oscillation center frequency can be easily changed by mounting the oscillation center frequency adjusting capacitor Cx attached in parallel with the resonant microstrip line SL outside the chip.

As mentioned earlier, the phase noise characteristics of the oscillator depend mainly on the Q value of the resonator and the noise figure (NF) of the varactor diode (Cv). In the present invention, it is possible to mount the inductance (L) of the resonator unit outside the chip (integrated circuit) to increase the Q value of the LC resonator unit, thereby improving the phase noise characteristics of the oscillator.

The inductance used in the present invention preferably uses a chip inductor or a microstrip line SL formed on the substrate 1 in order to reduce the size of the product. In order to increase the Q value of the resonator part, the Q value of the inductance L used in the resonator part needs to be large, and since the Q value of the inductance L depends on the resistance component of the inductance L, the smaller the size of the inductance element L is. The resistance increases and the Q value drops.

The use of an external microstrip line (SL) can greatly improve the low Q value and phase noise characteristics of conventional integrated voltage controlled oscillators. In addition, compared to the conventional integrated circuit type voltage controlled oscillator, which was unable to adjust the oscillation center frequency error generated in the manufacturing process due to the resonance inductance inside the chip, fine adjustment of the external microstrip line SL using laser trimming was performed. Because of this, significant benefits in manufacturing and quality control can be obtained.

If necessary, the oscillation center frequency can be easily changed by mounting the oscillation center frequency adjusting capacitor Cx attached in parallel with the resonant microstrip line SL outside the chip.

In addition, when the component value of the choke filter microstrip line (Choke SL) and the bypass capacitor (C5) (C9) are large, and they are mounted in the IC chip, when the chip size becomes very large, the oscillation signal output level is established. In addition to achieving the desired RF characteristics, it is possible to obtain a cost reduction effect for chip fabrication.

FIG. 3 is an assembly diagram of a voltage controlled oscillation device including an integrated circuit type micro voltage controlled oscillator chip 2 configured as described above, and a microstrip line SL of a resonance part on a substrate 1 composed of FR4, epoxy, or ceramic PCB. By adjusting the oscillation center frequency error by laser trimming or the like, the voltage controlled oscillator chip (2) and varactor diode (Cv) are formed on the substrate (1). Is mounted using a chip-on-board (COB) or surface mounting technology (SMT) technology. The varactor diode Cv of the frequency controller including the capacitor C1 is mounted with an independent varactor product having excellent phase noise characteristics as shown in FIG. 3 or embedded inside the voltage controlled oscillator chip 2. You can also In addition, large component values such as a choke filter microstrip line (Choke SL) and bypass capacitors (C5) and C9 may be mounted or embedded in the chip 2.

Here, the substrate 1 is made of a material such as ceramic, alumina, epoxy, FR4, and the like to mount circuit elements (voltage controlled oscillator chip and varactor diode) and circuit pattern 5. It is composed of one layer or more multilayers, and is combined with the shielding plate 3 for circuit protection and EMI shielding by soldering and / or high temperature sputtering.

A routing or solder mask is formed on the upper surface of the substrate 1 so that the circuit elements may be mounted and operated in a circuit, and the operation of the circuit elements mounted on the upper surface of the substrate 1 may be performed. A circuit pattern 5 corresponding to a power line, a control line, an output line, and the like, and a soldering pad formed on the bottom surface of the substrate 1 through a through hole or via 6. It is electrically connected to the soldering pad. Here, reference numeral 4 is a ground plane connecting the circuit elements formed on the substrate 1 to ground.

4 is a perspective view showing an embodiment for showing the structure of the microstrip line SL used in the present invention, wherein the microstrip line SL has a length L, a width W, a thickness t, and the like. The conductive portion 7 having high conductivity is positioned on the dielectric 8 such as alumina and ceramic, and is connected to the ground plane 9 by vias 6 or through holes.

FIG. 5 shows an equivalent circuit of the resonator including the synthesized capacitance Co and the compensation capacitor Cx inside and outside the microstrip line SL and the voltage controlled oscillator chip 2 formed as described above.

Here, the equivalent inductance Lo of the microstrip line SL is as in Equation 1 below,

Where Zo is the characteristic impedance of the line and fo is the resonance frequency.

In general, since the Q value of the capacitor is very large and can be ignored, the Q value of the resonator part from the equivalent circuit of FIG. 5 mainly depends on the Q value of the microstrip line SL and is approximated by Equation 2 below.

Where ω is the angular frequency, ω = 2 π f, and r represents the resistance component at frequency f.

In general, assuming that the conductor has a width (W), a thickness (t), and a length (L), σ, the DC resistance r _DC at the low frequency is expressed by Equation 3, and the AC resistance at the high frequency. r _ac can be obtained from Equation 4. Where δ is the skin depth at high frequency and is represented by equation (5).

As can be seen from the above equations, when the length L is constant, if the geometric cross-sectional area S, W, or t of the microstrip line SL is reduced, the value of Q decreases since the conductor resistance r of Equation 2 is increased.

6 shows the relationship between the Q value of the resonator unit and the phase noise characteristic. As shown in FIG. 6, when the Q value is decreased, the frequency selectivity of the resonator unit is decreased, thereby making it impossible to reduce or eliminate noise (phase noise) generated near the oscillation frequency. If the size of the microstrip line SL is reduced, the loss resistance increases accordingly, resulting in a decrease in the Q value and a worsening of phase noise.

In conclusion, if the resonator is integrated in the integrated circuit chip for miniaturization, the geometric size Q value of the microstrip line SL is reduced, so that an oscillator having excellent phase noise characteristics cannot be realized, and frequency variation or center frequency change generated during mass production Frequency fine tuning is not possible. In addition, the varactor diode (Cv) used in the frequency controller is also difficult to expect excellent phase noise characteristics when embedded in the integrated circuit chip, it is impossible to change the frequency variable range, change the center frequency.

Therefore, in the present invention, the varactor diode Cv and the microstrip line SL, which determine the phase noise characteristics of the voltage-controlled oscillator, are mounted outside the MMIC or RFIC integrated circuit chip, thereby providing excellent phase noise characteristics and frequency fine tuning. At the same time, it is possible to provide cost savings and flexibility in the chip design process by housing parts that are difficult to be mounted inside the chip when necessary. In addition, the oscillation center frequency can be easily changed by mounting the oscillation center frequency adjusting capacitor Cx attached in parallel with the resonant microstrip line SL outside the chip.

According to the present invention, it is possible to drastically improve the low phase noise characteristic of an integrated circuit type voltage controlled oscillator, and to fine-tune the center frequency, which was impossible in the above scheme. In other words, the resonator and the frequency controller that influence the phase noise characteristics are implemented on the substrate of FR4, ceramic, epoxy, alumina PCB, etc. outside the integrated circuit chip to increase the Q value of the resonator, which greatly improves the low phase noise characteristics and at the same time. By trimming the microstrip line, the oscillation frequency can be fine tuned.

In addition, according to the present invention, it has the same phase noise characteristics as the modular voltage controlled oscillator and enables a high-integration product configuration, which can reduce the manufacturing price, greatly reduce the size, weight and volume of the product, and significantly reduce the defective rate of the product. Can be reduced.

In addition, according to the present invention, since the resonator and the frequency controller are implemented on the substrate, the actual circuit can be easily implemented and the correction and correction such as the change of the center frequency can be made very easy. In addition, it is possible to reduce the effect on temperature, which is a disadvantage of the integrated circuit type voltage controlled oscillator, by using a ceramic PCB, etc., which has the advantage of realizing a product having the same temperature characteristics as the ceramic product. In addition, by connecting the part to the main board using ceramic PCB, the heat received from the main board can be minimized.

If necessary, the oscillation center frequency can be easily changed by mounting the oscillation center frequency adjusting capacitor Cx attached in parallel with the resonant microstrip line SL outside the chip.

In addition, if the component values are large, such as choke filter microstrip lines (Choke SL) and bypass capacitors (C5) (C9), and they are mounted inside the IC chip, the chip is oscillated by mounting them externally if necessary. In addition to achieving desired RF characteristics such as signal output levels, chip manufacturing cost savings can be achieved.

Although the present invention has been described in detail above with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical spirit of the present invention, and such modifications and modifications belong to the appended claims.

Claims (10)

Elements and microstrip lines such as varactor diode and one chip integrated voltage controlled oscillator, capacitor for adjusting oscillation center frequency, choke filter microstrip line, and two bypass capacitors In the integrated circuit type miniature voltage controlled oscillation device for improving the formed phase noise, A routing or solder mask is formed on the substrate so that the circuit elements on the substrate may be mounted and operated in a circuit, and a power line and a control line for operation of the circuit elements mounted on the substrate. And a circuit pattern corresponding to an output line is formed on the substrate, and the routing, solder mask, power line, control line, and output line are connected to the bottom surface of the substrate by vias or through holes. An integrated circuit type miniature voltage controlled oscillation element for improving phase noise, which is electrically connected to a holding pad. delete The method of claim 1, The substrate is FR4, an epoxy (epoxy) PCB or a ceramic PCB, alumina (alumina), characterized in that the integrated circuit type miniature voltage controlled oscillation device for improving the phase noise. The method of claim 1, The voltage controlled oscillator chip is an integrated circuit type miniature voltage controlled oscillator for improving the phase noise, characterized in that formed by MMIC (Monolithic Microwave Integrated Circuits) or RFIC (Radio Frequency Integrated Circuits). The method of claim 1, The voltage controlled oscillator chip and varactor diodes are attached to the substrate in the form of Surface Mounting Technology (SMT) or Chip-On-Board (COB), etc. Controlled oscillation element. The method of claim 1, The microstrip line is laser trimmed by a laser beam to enable fine tuning of the oscillation center frequency. The integrated circuit type miniature voltage controlled oscillation element for improving the phase noise. The method of claim 1, An oscillation center frequency adjusting capacitor (Cx) is attached to the circuit pattern on the substrate so that the oscillation center frequency can be changed together with the microstrip line. . The method of claim 1, A device having a large component value such as a choke filter microstrip line (Choke SL) and a bypass capacitor (C5) (C9) attached to a circuit pattern on the substrate to assist the circuit operation of the voltage controlled oscillator Integrated circuit type miniature voltage controlled oscillation device for improving the phase noise, characterized in that provided. The method of claim 1, An integrated circuit-type micro voltage controlled oscillation device for improving the phase noise, characterized in that the shield plate (shield) for the circuit element protection and EMI shielding on the substrate is further provided. The method of claim 9, The shielding plate and the substrate, the integrated circuit type miniature voltage controlled oscillation element for improving the phase noise, characterized in that coupled to the soldering (soldering) and / or high temperature sputtering method.