KR100831076B1 - Balun-band pass filter using dual-mode ring resonator - Google Patents

Abstract

A balun-bandpass filter using a dual-mode ring resonator is provided to realize both a balun characteristic and a band pass filter characteristic in a band width by a simple microstrip line path structure. A balun-bandpass filter using a dual-mode ring resonator includes a substrate, a one-wavelength ring resonator(50), an input terminal(60), a first output terminal(70), and a second output terminal(80). The one-wavelength ring resonator includes a first line path(51), a second line path(52), a third line path(53), and an open stub line path. The input terminal supplies an input signal from the outside from the ring resonator. The first output terminal generates a first output signal from the ring resonator. The second output terminal generates a second output signal of the same level of the first output signal from the ring resonator and a phase difference of 180 degrees from the first output signal from the ring resonator. The ring resonator has a two-stage band pass characteristic through forming a dual mode by differentiating impedance between the first line path and the second line path through the first and second output terminal in the input terminal.

Description

BALUN-BAND PASS FILTER USING DUAL-MODE RING RESONATOR}

1 is a block diagram of a general wireless communication system.

2A and 2B show the basic functions of the balun.

3 is a block diagram of a coaxial Marchand balun.

Figure 4 is a block diagram showing another coaxial Marchand balloon.

5A and 5B are diagrams illustrating a Marchand balun in the form of a micro strip.

6A and 6B show a half-wavelength balun.

7 is a conceptual block diagram using mutual coupling between resonators.

8 is a graph showing a change in frequency according to the coupling coefficient.

9 is a schematic diagram of a dual mode resonator using stub lines.

10 is a schematic diagram of a dual mode ring resonator using a multistage impedance line.

11A and 11B are respectively a balun-band pass filter and an equivalent circuit structure thereof according to the present invention.

12A and 12B are equivalent circuits for the upper and lower paths of the balun-band pass filter according to the present invention.

13 is a graph showing total transmission admittance versus impedance difference.

14 is a graph showing a result of simulating the transmission parameter S (2,1) by converting the entire transmission admittance into the S parameter.

15A and 15B are graphs showing simulation results of coupling coefficients according to impedance differences. FIG. 15A is a reflection loss and FIG. 15B is a graph of coupling coefficients.

FIG. 16 is a graph showing the shift of attenuation pole frequency with increasing 180 ° length line impedance Z ₃ between outputs.

18 is a graph showing the shift of the attenuation pole frequency with an increase in the stub line impedance Z _s .

19 is a photograph of a manufactured balun-band pass filter.

20 is a graph showing a comparison of the simulation results for the frequency response characteristics and the measurement results of the sample of the present invention.

21 is a graph showing a comparison between the simulation results of the output difference and the frequency of the two output stages and the measurement result of the sample of the present invention.

* Explanation of Signs of Major Parts of Drawings *

50: ring resonator 51-53: first to third lines

54: open stub line 60: input terminal

70: first output stage 80: second output stage

The present invention relates to a balun-band pass filter using a dual mode ring resonator, and more particularly, to obtain an unbalanced phase characteristic by placing each output stage in a symmetrical position in a single wavelength dual mode ring resonator. The present invention relates to a balun-band pass filter (Balun-BPF) using a dual-mode ring resonator having a balun characteristic that realizes a dual mode by providing an impedance difference between lines and performs an unbalance-balance conversion of an input / output signal.

Recently, almost all electronic devices are using wireless communication technology, and the existing wired communication is also being replaced by wireless communication. Accordingly, various wireless communication technologies such as ultra wide band (UWB), wireless LAN, Zigbee, and Bluetooth are being developed, and also wireless devices used in the communication technology are being developed. Performance is also developing rapidly. With the acceleration of the development of communication technology and performance, the development of miniaturization and light weight of wireless communication devices and devices is also rapidly accelerating.

However, in proportion to the increasing usage due to the technology development and performance improvement of the wireless communication system, communication noise factors such as communication interference between radio devices and the increase of radio wave generation sources are also increasing. In recent years, resistance to noise and harmonics is basically required for the elements constituting the wireless communication system.

In line with these demands, balanced signal devices such as amplifiers and mixers that use balanced signals that are easy to remove noise and harmonics are increasing in wireless communication systems. However, this is not the only use of these balanced signal elements in wireless communication systems. Devices using unbalanced signals, such as conventional filters and antennas, are also important and necessary to be used simultaneously. Thus, in the system, the unbalanced signal element and the balanced element are used simultaneously, and a device called balun is used as an intermediate conversion between the elements using the two signals. For this reason, balun has become a fundamental element in all wireless communication systems that use the recent unbalanced and balanced signals.

Usually, the balun is used with a band pass filter (BPF) between the antenna and the low noise amplifier (LNA) on the communication module, and is continuously connected to the front end or the rear end of the band pass filter, together with this filter to unbalance the input and output signals. And filtering together.

Conventionally, a technique in which a balloon is combined with an antenna is disclosed in Korean Patent Laid-Open Publication Nos. 2001-10509 and 5,873,833, and an FBAR filter having an unbalanced input / output structure implemented using a volume elastic resonance (FBAR) is disclosed. A microwave mixer having a balun having a square coaxial transmission line is disclosed in Japanese Patent Laid-Open No. 2006-27606, and a microwave mixer is disclosed in Japanese Patent Laid-Open No. 2001-93792, and a balun on a millimeter wave plane using a directional coupler is disclosed. Publication No. 2001-10897.

Since the balun is placed at the front or the rear of the bandpass filter, combining the bandpass filter and the balun into a single device not only has a great advantage in area, size, etc. in a wireless communication system, but also can bring great efficiency in the design of the system. have.

However, as described above, in spite of many advantages, a technique in which a band pass filter and a balun are combined into one device has not been proposed.

Accordingly, the present invention has been made to solve the above problems, and its object is to obtain an unbalanced phase characteristic by placing each output stage in a symmetrical position in a one-wavelength dual mode ring resonator, and achieve impedance between input and output lines. The present invention provides a balun-band pass filter using a dual-mode ring resonator having a balun characteristic that performs unbalance-balanced conversion of input and output signals by implementing a two-stage bandpass characteristic by forming a dual mode by providing a difference. .

Another object of the present invention is a simple microstrip line structure, which can simultaneously implement a balun and a band pass filter in a bandwidth so that a dual mode ring can be applied to various fields of ultra high frequency and millimeter wave fields requiring small capacity and area. To provide a balun-band pass filter using a resonator.

The present invention for achieving the above object, a substrate made of a dielectric; Both ends are connected to the first and second lines having a length of λ / 4, respectively, and both ends are connected to both ends of the first and second lines, respectively, and have a third line having a length of λ / 2 and a middle line of the third line. A wavelength ring resonator having an open stub line extending in a vertical direction and having a generally rectangular shape and formed using a microstrip line on the substrate; An input terminal coupled to a connection portion between the first line and the second line to apply an input signal to a ring resonator from the outside; A first output end coupled to a connection portion between one side end of the first line and a third line to generate a first output signal from the ring resonator; And a second output terminal coupled to a connection between the other end of the first line and the third line, the second output terminal having a 180 ° phase difference from the ring resonator and generating a second output signal having the same magnitude from the ring resonator. Using the dual mode ring resonator, characterized in that the ring resonator has a two-stage bandpass characteristic by forming a dual mode by providing an impedance difference between the first and the second line from the input terminal to the first and second output terminals Provide a balun-band pass filter.

The open stub line extends in the inward direction of the ring resonator, which is advantageous in reducing the size.

In addition, a third line having a length of? / 2 is disposed between the first and second output terminals, and a first and second line having a length of? / 4 is disposed between the input terminal and the first and second output terminals, respectively. And the phase characteristic between the second output terminal satisfies the phase characteristic of the balun.

Furthermore, in the present invention, the magnitude of the coupling coefficient and the number and position of the attenuation poles can be set by adjusting the difference between the first and second impedances of the first and second lines.

In this case, one attenuation pole of the band pass filter is formed when the first impedance and the second impedance of the first and second lines are the same, and when the first impedance is larger than the second impedance, the attenuation pole is not formed. For example, when the first impedance is smaller than the second impedance, one attenuation pole is formed on each side based on the center frequency.

In addition, the uppermost and lowermost resonant frequencies are changed according to the magnitude of the absolute value of the difference between the first impedance and the second impedance of the first and second lines, and proportionally to the magnitude of the absolute value of the difference between the first impedance and the second impedance. The interval between the uppermost and lowermost resonant frequencies is widened.

In the balun-band pass filter of the present invention, it is possible to set the position of the attenuation poles by the impedance of the open stub line and the impedance of the third line of? / 2 length.

In this case, as the impedance of the third line increases, the two attenuation poles move to a lower frequency band, and as the impedance of the open stub line increases, the two attenuation poles move to a higher frequency band.

In addition, it is preferable that the input / output terminal and the ring resonator are coupled to each other by using a gap coupling line in parallel.

(Example)

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, a Balun-BPF having a balun function according to the present invention in which a balun and a band pass filter continuously used in a wireless communication system are implemented as a single element using a ring resonator having a simple microstrip line structure will be described. do.

The Balun-BPF of the present invention uses a conventional one wavelength (λ) length ring resonator as a structure for simultaneously satisfying the characteristics of the balun and the band pass filter, and another one at a symmetrical position with the existing output stage. By adding the output stage of, the balun's 180 ° unbalanced phase characteristic was exhibited. In addition, the two-stage band pass characteristic is generated by providing a predetermined impedance difference between the upper and lower lines passing from the input terminal to each output terminal.

More specifically, in the present invention, a balun that uses only two stages in the balun is modified so that a line having a length of λ / 2 is disposed between the two outputs and a line having a length of λ / 4 is disposed between the input and the output, respectively. The phase characteristics were made to satisfy the balun's phase characteristics.

In addition, the mutual coupling amount of the resonance period is controlled by using the dual mode characteristic of the ring resonator, and the operation of the two-stage band pass filter can be performed equivalently by controlling the mutual coupling amount.

Below, the structure of a general wireless communication system is demonstrated first, and then the outline | summary and kind of a balun element are demonstrated. Next, the ring resonator used as a basic structure for implementing the balun and the band pass filter will be described.

The structure of the Balun-BPF according to the present invention is then described and analyzed using ABCD parameters and admittance parameters. Through the ABCD parameter analysis of the basic line, the parameters of the overall structure are obtained, and the overall transmission admittance is derived using the ABCD-Y parameter conversion table. The derived transmission admittance finds any desired filter condition by finding the variation of Transmission zeros and coupling coefficients according to the specified parameters.

In addition, the Balun-BPF of the present invention satisfies both the balun characteristics and the bandpass filter characteristics by directly fabricating and measuring the optimized structure.

1. Composition of general wireless communication system

A block diagram of a general wireless communication system is briefly shown in FIG. First, from the left side of the drawing, the antenna 1 for transmission and reception is located at the outermost side, and at the rear end of the antenna, only a desired frequency is selected from among random signals received through the antenna 1 at reception, and also at the time of transmission. A band pass filter (BPF) 2 is connected for selectively transmitting only a frequency of a desired signal among internally generated signals and noise signals that may be generated due to many causes.

A balun 3 is positioned between the band pass filter 2 and the Tx / Rx switch 4 to perform an arbitration role between two devices using two different signals. do. In addition, a switch element 4 and a transceiver 5 for arranging a transmission / reception mode are disposed at the rear end of the balun 3, and the transceiver 5 is an mixer for amplifying a signal and a mixer for making an output signal. And other elements are arranged. Finally, the internal memory and the control unit 6 for controlling and manipulating the system are located in the general wireless communication system.

As can be seen, in most wireless communication systems, bandpass filters and baluns are placed in the middle of elements that use balanced signals, such as switch elements, mixers, and amplifiers, and those that use unbalanced signals, such as antennas and filters. It is usually located so that the filtering and conversion of the signal can be performed at once.

2. Overview of Balun

The balun has been proposed in various structures since it was proposed by Marchand in 1944, and its design and analysis methods have been proposed in various ways. Balun is a compound word of BALance + UNbalance, a device that occupies an important position in a microwave device, and refers to any circuit or structure that converts an unbalanced signal into a balanced signal. Of course, the same is true of balun when performing the reverse conversion function.

Here, the unbalanced signal is a signal transmitted through one signal line with respect to a common reference voltage (Ground), and the balanced signal generally means a signal transmitted through two lines. A simple concept of this balun is shown briefly in FIG. Baluns on the microwave circuits function to interconnect components that use balanced signals from mixers or amplifiers and components that input and output unbalanced signals. The characteristic represents two balanced outputs for one unbalanced input. In addition, in a particular frequency domain, it is a basic condition of the balun that the two output stages have a 180 ° phase difference and the same magnitude.

The research on balun starts from Marchand type balun presented by the first Marchand, and various studies are currently being conducted for miniaturization and stable operation such as balun using coaxial line and balun using microstrip line.

3. Types of balun

3 shows a coaxial Marchand balun using a coaxial line, which is the most basic form of a balun using a phase in which the internal current and the external current of the coaxial line are reversed. One side of the coaxial cable is grounded and inputs a signal to create an unbalanced signal, and the other side uses an inner shaft and an outer surface to form a balanced signal. Looking at the current flow simply, the current I _in1 flowing along the inner surface of the outer conductor 12 is generated by the current I _co1 flowing along the inner surface of the inner conductor 11.

The current I _out1 flowing along the outer surface of the outer conductor 12 is a short stub line 13a of length λ / 4 formed by the outer conductor 12 of the coaxial line extending to the inside and the entire conductor surrounding it. No current flows because it appears to be opened by .13b). Similarly, since I _out2 also does not flow current, current I _in2 in the opposite direction flows in the direction of I _B2 to I _co2 having the same size as I _co1 . Thus, as shown in FIG. 3, the current I _B2 is equal to I _B1 and produces a balanced signal having the same phase and opposite phase. Here, the open stub line 14 having a length of λ / 4 through which the current I _co2 flows serves to make the phase shift constant over a wide frequency band.

Coaxial balun has the advantage that its structure and principle are simple and have excellent characteristics over a wide frequency band.However, coaxial lines are difficult to fabricate and bulky, making them difficult to apply to other circuits. However, as a balun of the most basic principle, it is still a structure that is frequently used to obtain a balun with excellent characteristics.

4 is a structure of a balloon for applying Marchand balun to a wider band and improving characteristics. This structure is formed by connecting two coaxial lines 15 and 16 in parallel. Where Z _b and Z _a are the impedances of the upper and lower lines, respectively, and Z _ab is the characteristic impedance of the balanced transmission line by the outside of the coaxial line.

5 is a balun implemented by replacing the coaxial line of the coaxial balun of FIG. 4 with a microstrip line. The basic principle is the same as that of the coaxial balun because it only replaces the coaxial line of the coaxial balun with a microstrip line. 5 (a) is a structure in which a single coaxial line is simply replaced by a microstrip, and FIG. 5 (b) is a balun that allows to approach the characteristics of a balun using a coaxial line using a microstrip coupling line.

Compared with the balun of FIG. 4, the first coupling line portion of the input coincides with the inner conductor of the coaxial line, and the next coupling line portion coincides with the outer surface of the coaxial line. The ground plane of the coaxial line grounded one end of the coupling line. Looking at the basic signal flow, the other end of two λ / 4 combined lines with unbalanced signals applied to half-wavelength (λ / 2) lines with open ends and grounded at one end at the input and half-wavelength ends, respectively. Equilibrium signals of equal magnitude and opposite phases can be obtained from the part.

Since the balun of the microstrip structure uses microstrip lines instead of the coaxial line, the performance of the microstrip structure is easy to implement due to the actual manufacturing advantages of the microstrip structure, although the performance is lower than that of the coaxial balun. It can be mass-produced and can be easily and simply applied to other circuits through a printed circuit board (PCB), which is widely used for high frequency circuits.

FIG. 6 is a simple balun structure that gives a 180 ° phase difference between outputs using a λ / 2 length line. This structure is based on the principle that the phase difference between the two outputs is 180 ° by simply placing one or periodically the line 21 of λ / 2 between the two balanced outputs. This structure has the advantage that the principle is simple and easy to implement since it only uses a λ / 2 length microstrip line. However, since the length of λ / 2 can be applied only at a limited frequency, the use band is narrow. In order to improve this, as shown in FIG. 6 (b), a method of periodically arranging a structure having a "c" shape consisting of a line 21 having a length of λ / 2 and resonators 22a and 22b having a length of λ / 4 is provided. have. However, this structure also uses a large number of structures periodically to improve the characteristics, there is a disadvantage that the overall area becomes larger.

4. Bandpass Filter Using Mutual Coupling

In general, when converted from the basic forms of the lowpass filter to the bandpass or bandstop filter, it consists of a series resonator and a parallel resonator. However, when implementing a filter for a particular type of transmission line, there are cases where only serial elements or parallel elements are desired. In this case, a band pass or band stop filter may be implemented using an impedance K and an admittance J inverter. In order to make the characteristic of the filter using the inverter the same as that of the filter implemented with the lumped element, the reflection coefficient seen from the input terminal must be the same.

In general, when an inverter 33 or a coupling element is applied between resonators 31 and 32 having the same resonant frequency as shown in FIG. 7, the frequency becomes wider based on the resonant frequency. That is, as the coupling coefficient increases as shown in FIG. 8, the frequency interval spreading becomes wider.

Therefore, a two-stage band pass filter can be designed using mutual coupling between bandstop resonators having the same characteristics. In addition, the band pass bandwidth can be adjusted by varying the amount of mutual coupling.

5. Design of Filter Using Dual-Mode Ring Resonator

Ring resonators are often used to implement dual-mode filters because of their ability to easily obtain bandpass response by providing discontinuities such as simple patches, slots, or notches.

The basic principle of a ring resonator is that in a circular ring structure, if a patch, slot, or notch is inserted at the midpoint of the input / output part, two different paths are formed from the input to the output. Even-odd mode, which is a degenerate mode, occurs. In general, the resonance and degenerate modes of generation usually exist in the plane of symmetry within the structure, and the resulting even-odd mode can be used to design the characteristics of the filter.

9 illustrates a structure in which a stub line is inserted into a symmetry point, which is one of the most basic structures for generating a filter by generating a dual mode using a ring resonator. As shown in FIG. 9, a stub line 45 for perturbation is disposed at a dotted line, which is a symmetry point between the input 41 and the output 42, and a path 43 having a length of λ / 4 and a stub line between the input and the output. There is a path 44 of length 3λ / 4. Port portions of the input 41 and output 42 consist of coupling gaps, rather than simple line connections, to enhance the bimodal characteristics. The length and width of the stub line 45 in this structure are important parameters for determining the size and ratio of each even-odd mode.

FIG. 10 is similar to the method of inserting the stub line of FIG. 9, in which the path 45a having a different impedance and the path 43 having a length of lambda / 4 are different for a path having a length of 3λ / 4; There is a multi-stage impedance method of switching to the lines 44a and 44b having the same pattern. If the stub line method is changed according to the length of the stub line, the multi-stage impedance method is characterized by how much impedance (Z _p ) and how long (2θ _p ) is replaced by the line 45a section with different impedance. This is determined. However, the basic structure analysis or filter design method is similar to the stub line method.

6. Planar structure and equivalent circuit of Balun-BPF according to the present invention

The planar structure and equivalent circuit of the Balun-BPF proposed in the present invention are shown in FIGS. 11A and 11B.

In the present invention, to implement the balun and the band pass filter as a single Balun-BPF using a simple microstrip line structure, a phase difference of 180 ° between outputs is obtained by using the λ / 2 length line of FIGS. 5 and 6 described above. A method of designing a balun of a microstrip structure, a method of designing a two-stage bandpass filter using mutual coupling between resonators having the same characteristics of FIGS. 7 and 8, and the dual mode ring resonator and stub line of FIGS. 9 and 10. Filter design and deformation method of stub line are considered.

Balun-BPF according to the present invention obtained in consideration of the above design method is a structure for simultaneously satisfying the characteristics of the balun and the band pass filter, as shown in Figure 11a, the overall structure is the input terminal 60 (P1) and the first output terminal 70 : One new second output stage 80 (P3) is formed based on the wavelength ring resonator 50 as long as the first line 51 having a length of λ / 4 is disposed between P2) and the existing first output stage 70. By adding one more to the symmetrical position, i.e., the other end of the second line 52 of length λ / 4 from the input end 60 to the lower path, consequently the λ / between the first and second output ends 70, 80. A third length 53 of two lengths is arranged to satisfy the 180 ° phase difference unbalanced phase characteristic of the balun.

In addition, a dual mode is formed by providing an impedance difference between the upper and lower first and second lines 51 and 52 from the input terminal 60 to the respective output terminals 70 and 80 so that the two-stage band pass characteristics are improved. Appeared.

Furthermore, an open stub 54 inserted between the input and output stages to create a dual mode filter is placed in the middle of the 180 ° line between the two output stages 70 and 80, i.e., the third line 53 having a length of λ / 2. It was inserted and positioned inward of the ring resonator 50 to reduce the total area.

In the present invention, a third line 53 having a length of λ / 2 is disposed between the two output terminals 70 and 80, and a line having a length of λ / 4 is disposed between the input terminal 60 and the two output terminals 70 and 80, respectively. The phase characteristics between the two output terminals 70 and 80 satisfy the balun's phase characteristics. That is, when an unbalanced signal is applied to the input terminal 60, a balanced signal having the same magnitude and opposite phases can be obtained from the first and second output terminals 70 and 80.

In addition, the mutual coupling amount of the resonance period was adjusted by using the dual mode characteristic of the ring resonator 50, and the operation of the two-stage band pass filter was equivalently performed by controlling the mutual coupling amount.

Moreover, the capacitance C _g between the input / output terminals 60, 70, 80 and the ring resonator 50 shown in the equivalent circuit of FIG. 11B is, as shown in FIG. 11A, to improve the dual mode characteristic in the practical structure. A parallel line gap coupling between the input / output terminals 60, 70, 80 and the ring resonator 50 is implemented.

Hereinafter will be described the characteristics of Balun-BPF according to the present invention implemented as described above.

6-1. Formation of attenuation poles

In order to examine the relationship between the line impedance and the attenuation pole, the input terminal P1 and the first output terminal P2 are set as input / output terminals. In the equivalent circuit of FIG. 11B, the second output terminal P3 has a characteristic impedance Z ₀ . Replaced by. The path from the input terminal P1 to the first output terminal P2 is divided into two paths, respectively, by using the ABCD parameter and the Y parameter. The paths are divided into upper and lower sides, respectively, and the divided paths are shown in FIGS. 12A and 12B. .

First, the transmission admittances of the up and down paths were obtained, respectively, and then the total transmission admittances were obtained.

Each ABCD parameter for the up and down paths is represented by Equations 1 and 2 below.

Here, C = cosβl, S = j sinβl, and Z _p and Z _s are impedances of the line of the second output terminal P3 and the open stub 54, and are expressed by Equations 3 and 4 below.

When the B component is obtained by arranging the ABCD parameters obtained above, Equations 5 and 6 are obtained.

Referring to the parameter conversion table, since the transmission admittance is Y ₂₁ = -1 / B, the transmission admittance of the entire structure can be obtained by using Equations 5 and 6 as shown in Equation 7 below.

는 전체 전송 어드미턴스,

과

는 각각 상측 경로와 하측 경로의 전송 어드미턴스이고,

과

는 각각 상측 경로와 하측 경로의 ABCD 파라미터의 B성분이다.here,

Full transmission admittance,

and

Are transmission admittances of the upper path and the lower path, respectively,

and

Are B components of ABCD parameters of the upper path and the lower path, respectively.

Knowing the total transmission admittance, it can be used to determine transmission zeros. Transmission-zeros is a parameter that can determine the attenuation pole among the characteristics of the filter, and can be obtained by using Equation 7 as a value where the transmission admittance becomes zero. When transmission-zeros are obtained using Equation 7, it is shown in Equation 8 below. As can be seen from the equation, it can be seen that the absolute values of the transmission admittances of the upper path and the lower path are the same.

) 지점을 나타낸다. FIG. 13 is a graph showing total transmission admittances. The point where the x-axis (normal frequency) and the graph curve meet is shown in transmission-zeros (

) Represents a point.

Here, the variable (x) of the graph is the impedance (Z ₁ , Z ₂ ) of the upper and lower first and second lines 51 and 52 directly connected from the input terminal 60 to the first and second output terminals 70 and 80. As a difference, it has a relationship as shown in Equation 9 below.

In the result of FIG. 13, the transmission-zeros point is determined by the impedance difference x between the impedances Z ₁ and Z ₂ of the upper and lower first and second lines 51 and 52 directed to the respective output terminals 70 and 80. It can be seen that. When Z ₁ and Z ₂ the same (when the size of the x day 0) is one, when Z ₁ is greater than Z ₂ (when the size of the negative x days) does the attenuation pole is formed. However, when Z ₁ is smaller than Z ₂ (when x is a positive number), one transmission-zero point is formed on each side based on the center frequency.

이 되는 지점 즉, 감쇄극을 위의 수학식 8을 이용하여 그래프로 나타낸 결과로서, 그래프에서 보듯이 감쇄극은 임피던스 차(x)에 의해 결정이 되며, Z₁과 Z₂가 같을 때는 한 개, Z₁이 Z₂보다 큰 경우는 감쇄극이 형성 되지 않고, Z₁이 Z₂보다 작은 경우는 중심 주파수의 양옆에 하나씩 감쇄극이 형성이 된다.That is, in FIG. 13, the transmission admittance is

The attenuation poles, that is, the attenuation poles are graphed using Equation 8 above. As shown in the graph, the attenuation poles are determined by the impedance difference (x), and one when Z ₁ and Z ₂ are the same. When Z ₁ is larger than Z ₂ , the attenuation poles are not formed. When Z ₁ is smaller than Z ₂ , the attenuation poles are formed one by one on both sides of the center frequency.

Next, FIG. 14 shows a simulation by confirming the transmission parameter S (2,1) by converting the total transmission admittance calculated above into the S parameter. Similarly, the parameters of the graph were simulated by setting the impedance difference (x) between the impedances Z ₁ and Z ₂ of the upper and lower first and second lines 51 and 52.

As we have already seen in the graph of transmission-zeros, the simulation result of S (2,1) is the same as before, and when _one of Z ₁ and Z ₂ is the same, there is one attenuation pole, and when Z ₁ and Z ₂ are larger than If it is not formed and is smaller than Z ₁ and Z ₂ , it can be seen that one attenuation pole is formed on each side based on the center frequency. Therefore, when the filter is designed in consideration of the magnitude of the impedance difference (x) when inserting the attenuation pole for improving the skirt characteristics, the attenuation pole can be formed at a desired point.

 6-2. Coupling factor

A change in the coupling coefficient according to the impedance difference x between the impedances Z ₁ and Z ₂ of the upper and lower first and second lines 51 and 52 is represented as shown in FIG. 15B. Coupling coefficient was calculated using the following equation (10).

Here, k is a coupling coefficient, f ₀₂ and f ₀₁ are frequencies at the top and bottom of the pass band, respectively, and the positions thereof are shown in FIG. 15A. f ₀₂ and f ₀₁ were obtained by simulation of x using the Y parameter calculated earlier.

First, in FIG. 15A, it can be seen that the uppermost and lowermost resonant frequencies vary according to the magnitude of the absolute value of x. If the magnitude of x is less than about 2.4, there is one resonant frequency, and if it is larger than that, the distance between the two resonant frequencies f ₀₂ and f ₀₁ becomes wider in proportion to the magnitude of x. have.

Referring to FIG. 15B for the coupling coefficient, the coupling coefficient is also determined according to the value of x. If the magnitude of x is smaller than about 2.4, the coupling coefficient is 0, and if it is larger than that, the magnitude of x is larger. It can be seen that the magnitude of the coupling coefficient increases in proportion to. In other words, it can be seen from the results of FIG. 15B that the impedance difference has a large influence on the determination of the coupling coefficient as well as the attenuation electrode.

6-3. Attenuation movement

Hereinafter, the impedance of the open stub 54 line between the impedance Z ₃ of the third line 53 of λ / 2 length between the two output terminals 70 and 80 and the third line 53a and 53b ( Z _s ).

First, FIG. 17 shows how the attenuation pole frequency moves while increasing the impedance Z ₃ of the third line 53 having a length of? / 2. The results show that the frequency shift values of the low band and the high band do not coincide exactly, but in general, as the impedance Z ₃ of the third line 53 of length λ / 2 increases, the two attenuation poles move to a lower frequency band, so λ / 2. It can be seen that the impedance Z ₃ of the length third line 53 and the frequency position of the attenuation electrode are in inverse proportion.

Next, the trend of attenuation pole frequency shifts while increasing the impedance Z _s of the open stub 54 line between the third line 53 of the? / 2 length. Here, the input impedance of the Z _s stub line is expressed by Equation 11 below.

Where Z _s is the characteristic impedance of the stub line and β l _s is the electrical length of the stub line.

As a result, it can be seen that as the impedance Z _s of the stub line increases as opposed to the impedance Z ₃ of the third line 53 of length λ / 2, the two attenuation poles move to a higher frequency band. The impedance Z _s of the line and the frequency position of the attenuation electrode are in proportional relation.

6-4. Sample production and measurement results

Sample fabrication was performed using Taconic's RF-60A substrate with relative permittivity ε _r = 6.15, thickness 0.64 mm and dielectric loss tan δ = 0.0025. The produced Balun-BPF was measured using Anritsu's VNA 37397C, the actual Balun-BPF is shown in Figure 18. As a result of the fabrication, the size of the inner ring excluding the input / output terminals 60, 70, and 80 had an area of 16.5 × 16.5 mm 2.

19, 20 and 21 compare the S parameter measurement results of the simulation and the actual Balun-BPF produced. As a result of the measurement, the insertion loss was -2 ~ -3dB, which is 2 ~ 3dB lower than the simulation in the actual fabrication measurement, but the overall characteristics such as the position of the attenuation pole and the pass band were the same as the simulation. The reason why the insertion loss is 2 to 3 dB lower than that of the simulation is due to the low Q value of the ring resonator 50 and the loss due to the substrate during manufacturing. The Q value can be calculated by equation (12).

The calculation result shows that the Q value is very low, about 135.

Referring to the characteristics of the band pass filter of FIG. 19, a two-pass band having a bandwidth of about 42 MHz is shown as a center frequency of 2.45 GHz, and the difference between the two output stages 70 and 80 is also almost within 1 dB as shown in FIG. There is no. As shown in FIG. 21, the phase difference characteristic of FIG. 21 is 181 ° to 184 ° as a whole, and the phase difference characteristic of the balun is sufficiently satisfied since it has a range of about 1 ° to 4 ° about 180 °.

In the existing wireless communication system, the balun and the bandpass filter are separately connected to the system, taking up a large area in the system. As described above, the present invention provides a Balun-BPF in which the existing balun and the band pass filter are implemented as a single device using a dual mode ring resonator.

In the present invention, in order to satisfy the characteristics of the balun and at the same time to obtain the bandpass characteristics, a ring resonator structure is used which easily obtains the bandpass response characteristics by adding discontinuities such as simple patches or slots to the balun. The addition of one more output stage resulted in a third line of λ / 2 length between the two output stages, resulting in a 180 ° unbalanced phase characteristic of the balun.

In addition, through the analysis of the transmission admittance parameter, the magnitude of the coupling coefficient and the number and position of the attenuation poles could be determined by adjusting the impedance difference between the upper and lower first and second lines from the input to the output. The position of the attenuation electrode can be adjusted by the impedance of the line and the impedance of the third line having a length of? / 2.

Furthermore, the optimized Balun-BPF of the present invention exhibited the characteristics of a balun that satisfies both the characteristics of the two-stage bandpass filter, the unbalanced phase of 181 ° to 184 °, and the power distribution difference within 1dB between the outputs in the passband.

The Balun-BPF proposed in the present invention is a simple microstrip line structure that can simultaneously implement the characteristics of the balun and the bandpass filter within the bandwidth, so that it can be applied to various fields such as the ultra-high frequency field and the military wave field requiring less capacity and area. Can be applied.

Claims (9)

A substrate made of a dielectric; Both ends are connected to the first and second lines having a length of λ / 4, respectively, and both ends are connected to both ends of the first and second lines, respectively, and have a third line having a length of λ / 2 and a middle line of the third line. A wavelength ring resonator having an open stub line extending in a vertical direction and formed in a generally rectangular shape and formed using a microstrip line on the substrate; An input terminal coupled to a connection portion between the first line and the second line to apply an input signal to a ring resonator from the outside; A first output end coupled to a connection portion between one side end of the first line and a third line to generate a first output signal from the ring resonator; A second output end coupled to a connection between the other end of the first line and the third line, the second output end having a 180 ° phase difference from the ring resonator and generating a second output signal having the same magnitude, The dual mode ring resonator has a two-stage bandpass characteristic by providing a dual mode by providing an impedance difference between the first and second lines from the input terminal to the first and second output terminals. Balun-band pass filter used. The balun-band pass filter according to claim 1, wherein the open stub line extends inwardly of the ring resonator. The third line of claim 1, wherein a third line having a length of? / 2 is disposed between the first and second output terminals such that the phase characteristic between the first and second output terminals satisfies the phase characteristic of the balun. 2. A balun-band pass filter using a bimodal ring resonator, wherein the first and second lines having a length of λ / 4 are disposed between two output terminals. 2. The dual mode ring resonator of claim 1, wherein the magnitude of the coupling coefficient and the number and position of the attenuation poles are set by adjusting the first and second impedance differences between the first and second lines. Balun-band pass filter. The attenuation pole of the band pass filter is formed when the first impedance and the second impedance of the first and second lines are the same, and the attenuation pole is formed when the first impedance is larger than the second impedance. Balun-band pass filter using a dual-mode ring resonator, characterized in that the attenuation poles are formed on each side based on the center frequency when the first impedance is less than the second impedance. The absolute value of the difference between the first impedance and the second impedance according to claim 4, wherein the resonant frequency of the uppermost and lowermost is changed according to the magnitude of the absolute value of the difference between the first impedance and the second impedance of the first and second lines. A balun-band pass filter using a bimodal ring resonator, characterized in that the spacing between the top and bottom resonant frequencies is widened in proportion to the magnitude. The balun using a dual mode ring resonator according to any one of claims 1 to 6, wherein the position of the attenuation pole is set according to the impedance of the open stub line and the impedance of the? / 2 length third line. -Band pass filter. 8. The method of claim 7, wherein the two attenuation poles move to a lower frequency band as the impedance of the third line increases, and the two attenuation poles move to a higher frequency band as the impedance of the open stub line increases. Balun-band pass filter using mode ring resonator. The balun-band pass filter according to any one of claims 1 to 6, wherein the input / output stage and the ring resonator are respectively coupled by using parallel line gap coupling.

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