TW201342704A - Balanced type common mode signal suppression dual frequency bandpass filter designed by T type and lambda/2 stepp impedance resonator (SIR) - Google Patents

Abstract

A balanced type common mode signal suppression dual frequency bandpass filter designed by T type and lambda/2 step impedance resonator (SIR) comprises: a microwave substrate, a first step impedance resonator, a second step impedance resonator, a first T type resonator, and a second T type resonator. The first and second step impedance resonators and the first and second T type resonators have the same resonance frequencies which are the central frequency points of two working bands during differential mode operation. Two ends of the horizontal arm of the first and second T type resonators are grounded to generate a transmission zero point on the coupled mode of the first and second stepped impedance resonators during common mode operation; in addition, in order to enhance the compression of common mode signal, a high impedance open-stub is added to the center of the second step impedance resonator to the output end so as to increase the zero point mechanism to achieve common mode response compression.

Description

Design of balanced dual-band pass filter with common mode signal suppression by T-type and λ/2 stepped impedance resonator (SIR)

The invention is applied to the technical field of band-pass filters, in particular to a balanced dual-band pass filter with a T-type and λ/2 stepped impedance resonator (SIR) for suppressing common mode signals. It uses appropriate arrangements of the structure and adds a high-impedance open-circuit stub to the center of the step-step impedance resonator (SIR) to stagger the common-mode frequency and strengthen the suppressor of the common-mode signal.

A good balanced filter must have both good differential mode response and rejection of common mode signals. Balanced filters can be divided into the following two main design concepts: The first is a coupled line architecture [Y.-S. Lin and CH Chen, "Novel balanced coupled-line bandpass filters," in In Proc. URSI Int. Eleectromag. Theory Symp., pp. 567-569, 2004.] [C.-H. Wu, C.-H. Wang, and CH Chen, "Novel balanced coupled-line bandpass filters with common-mode noise suppression," IEEE Trans. Microw. Theory Tech., vol. 55, no. 2, pp. 287-295, Feb. 2007. The second is a resonator coupling architecture [C.-H. Wu, C.-H. Wang, and CH Chen, "Stopband-extended balanced bandpass filter using coupled stepped-impedance resonators," IEEE Microw. Wireless Compon. Lett ., vol. 17, no. 7, Jul. 2007.][C.-H. Wu, C.-H. Wang, and CH Chen, "Balanced coupled-resonator bandpass filters using multisection resonators for common-mode suppression and Stopband extension," IEEE Microw. Wireless Compon. Lett., vol. 17, no. 7, Jul. 2007.], but all of the above documents reveal Single-frequency balanced bandpass filters do not meet today's communication systems.

Therefore, in view of the problems existing in the above-mentioned conventional structure, how to develop an innovative structure that is more ideal and practical, the consumers are eagerly awaiting, and the relevant industry must strive to develop the goal and direction of breakthrough.

In view of this, the inventor has been engaged in the manufacturing development and design experience of related products for many years. After detailed design and careful evaluation, the inventor has finally obtained the practical invention.

Due to the rapid spread of wireless mobile communication products, the transmission channel and quality must be increased in response to market demand. The balanced filters of the conventional coupled-line architecture and the resonator coupling architecture are single-band balanced band-pass filters, which cannot meet the current communication system. Needed.

In order to improve the above problems, the present invention provides a balanced dual-band pass filter with a T-type and a λ/2 stepped impedance resonator (SIR) for suppressing a common mode signal, comprising: a microwave substrate, a a first stepped impedance resonator, a second stepped impedance resonator, a first T-type resonator and a second T-type resonator, the first and second step steps are performed during differential mode operation The resonant frequency of the impedance resonator and the first and second T-type resonators are designed to be the same as the center frequency point of the two operating bands. In the common mode operation, the first and second step impedance resonators resonate in the even mode, but the first and second T resonators do not have the resonant frequency, and are grounded at both ends of the horizontal arm. A transmission zero can be generated on the even mode of the first and second step impedance resonators, so that the output of the common mode signal can be reduced during coupling to achieve the suppression effect. In addition, in order to enhance common mode rejection, the present invention adds a high-impedance open-circuit stub to the center of the second-step impedance resonator at the output end to increase the zero-point mechanism to suppress the common mode response.

The invention adopts a T-type and λ/2 step-type impedance resonator (SIR) to design a balanced dual-band pass filter with a common mode signal, and determines the dual frequency center frequency by changing the impedance ratio of the stepped impedance resonator. The T-type resonator is designed to operate in the desired frequency band, and the two ends of the horizontal arm of the resonator are grounded, and the structure can generate a transmission zero point in the common mode band. In addition, a high-impedance open-circuit stub is added to the center of the stepped impedance resonator at the output to stagger the common-mode frequency, so that the common mode is suppressed to -20 dB in the frequency range of 1-7 GHz, which has a good common mode. Noise suppression effect.

The above-mentioned objects, structures and features of the present invention will be described in detail with reference to the preferred embodiments of the present invention. .

Referring to the first to sixth figures, the present invention provides a balanced dual-band pass filter with a T-type and λ/2 stepped impedance resonator (SIR) for suppressing common mode signals, including: a microwave a substrate (90) having a plate thickness of 0.635 mm, a dielectric constant of 10.2, and a loss tangent of 0.0023; a first step impedance resonator (10), the first step The impedance resonator (10) is a half-wavelength (λ/2) two-step impedance resonator disposed on the left half plane of the surface of the microwave substrate (90); a second step impedance resonator (20) The second step impedance resonator (20) is also a half-wavelength (λ/2) two-step impedance resonator, and the structure is exactly the same as the first step impedance resonator (10). Disposed on the right half plane of the surface of the microwave substrate (90), and disposed symmetrically with the second symmetric plane (80) and the first stepped impedance resonator (10), and the second step impedance resonance The central portion of the device (20) is loaded with a high-impedance open-circuit stub (50). The structure of the high-impedance open-circuit stub (50) is as shown in the first figure: the sixteenth dimension (L51) = 2.7 mm. Seventeen size (L52) = 1.4mm, the common mode signal is suppressed by staggering the resonant frequency; a first T-type resonator (30), the first T-type resonator (30) is short-circuited at both ends, and is configured An upper half plane on the surface of the microwave substrate (90); and a second T-type resonator (40), the second T-type resonator (40) is short-circuited at both ends, and the first T-type resonator is configured Exactly the same, disposed in the lower half plane of the surface of the microwave substrate (90), and arranged symmetrically with the first T-shaped resonator (30) in a first symmetry plane (70), the open stub of the middle portion A transmission zero at 3.85 GHz can be provided to achieve the goal of suppressing common mode signals.

The foregoing considerations facilitate analysis. The present invention defines a first step impedance resonator (10) and a second step impedance resonator (20) as a resonator A, a first T-type resonator (30) and a second T. The type resonator (40) is defined as a resonator B. A balanced filter signal can be divided into a differential mode and a common mode, and a plane of symmetry (POS) is used as a reference plane for analysis, when operating in a differential mode. The POS is considered to be an electrical wall (short-circuit to ground); when operating in common mode, the POS is considered a magnetic wall (open circuit). The present invention first designs the first ( f _{A 1} ), the second ( f _{A 2} ), and the third frequency ( f _{A 3} ) of the resonator _A to 2.45, 3.85, and 5.25 GHz, respectively. When the filter operates in the differential mode, the first symmetry plane (70) can be regarded as being short-circuited to ground, in which case the resonator A is only excited by the odd mode, and the odd mode is the first and third resonances. Mode (the resonance frequency is 2.45 and 5.25 GHz, respectively); when operating in the common mode, the first plane of symmetry (70) can be regarded as an open circuit, and at this time, the resonator A only has an even mode excited, and its even The mode is the second resonant mode (its resonant frequency is 3.85 GHz).

Since the resonator B does not cross the first symmetry plane (70), the modes excited are the same in the differential mode and the common mode operation, but since the structure is symmetrical, the parity mode can be used. Do the analysis. Accordingly, the first ( f _{B 1} ), the second ( f _{B 2} ), and the third resonant frequency ( f _{B 3} ) of the resonator _B are first designed to be 2.45, 5.25, and 7.7 GHz, respectively. When the resonator B operates in the odd mode, the second symmetry plane (80) can be regarded as a short circuit to the ground, and at this time, the half circuit of the resonator B can be equivalent to a λ/2 grounded resonator, which generates The resonant mode is the third mode of the complete resonator B (its frequency is 7.7 GHz). When operating in the even mode, the second symmetry plane (80) is regarded as an open circuit, and the half circuit of the resonator B can be equivalent to an SIR (since the lengths of the two sections are the same, the following formula can be used to obtain the same The structural mode), the resulting resonant modes are the first and second modes of the resonator B (resonant frequencies of 2.45 and 5.25 GHz), as shown in the second figure, by the known SIR literature [M. Sagawa M. Makimoto, and S. Yamashita, "Geometrical structures and fundmamental characteristics of microwave stepped-impedance resonators," IEEE Trans. Microwave Thory Tech., vol. 45, no. 7, pp. 1078-1085, Jul. 1997. It is known that the present invention compares the frequency ratio of the second and third resonance frequencies ( f _{A 2} and f _{A 3} ) of the resonator _A to the fundamental frequency ( f _{A 1} ) and the second resonance of the resonator _B ( f _{B 2} The frequency ratios to the fundamental frequency ( f _{B 1} ) are expressed as follows:

R _ZA and R _ZB in the formulas (1), (2) and (3) are the impedance ratios of the low impedance to the high impedance of the resonator A and the resonator B, respectively. According to the above formula, the resonator of the design circuit can be obtained. The impedance ratio of A to resonator B is 2.42; the corresponding length is 7.7 (6.9) mm at the fundamental frequency (2.45 GHz), wherein the present invention designs the high impedance portion of resonator A (resonator B) to 60. Ω (22 Ω), the structure size of the resonator A and the resonator B can be determined by the above parameters, and the result is as shown in the first figure. 1. Resonator A part: first size (L11) = 2 mm, Two dimensions (L12) = 2 mm, third dimension (L13) = 4.2 mm, fourth dimension (L14) = 4.75 mm, fifth dimension (L15) = 5 mm, sixth dimension (L16) = 1 mm, seventh dimension ( L21)=0.45mm, eighth size (L22)=1.5mm, ninth size (L23)=0.54mm, tenth size (L24)=6mm; 2.resonator B part: eleventh size (L31) = 2 mm, twelfth dimension (L32) = 6.7 mm, thirteenth dimension (L33) = 2.2 mm, fourteenth dimension (L34) = 14.5 mm, fifteenth dimension (L35) = 0.5 mm. When operating in differential mode, because the resonant frequency is designed the same, the signal can be coupled from the input to the output to achieve the desired design. When operating in the common mode, the coupling of the signal can be reduced due to the different resonant frequencies of each other. In addition, the central open circuit segment to be loaded in the resonator B is designed to have a transmission zero at 3.85 GHz, which further suppresses the common mode response of the resonator A.

In order to obtain the coupling pitch between the resonators and to match the frequency of each frequency band, the circuit of the present invention uses the Butterworth function as the filter response, and the frequency 寛(Δ) of the two bands is 7% (to satisfy the design) The frequency range of the WLAN and some security ranges are reserved), and the component parameters of the low-pass filter prototype are g ₀ =1, g ₁ =1, g ₂ = 2, g ₃ =1, g ₄ =1, And operate in the differential mode, the required resonator coupling coefficient ( = ) and the external quality factor of the external resonator A of the input and output ( ) as shown below [J.-S. Hong and MJ Lancaster, Microstrip filters for RF/Microwave Application, John Wiley and Sons, pp. 129-159, 2001.]:

According to formulas (4) and (5), the present invention simulates using an electromagnetic simulation software, and makes a graph of parameter changes, and simultaneously selects a coupling coefficient and an external quality factor corresponding to the above calculated parameters, and selects a coupling pitch (S). And the feeding position (t), as shown in the third A diagram and the third B diagram.

In order to enhance the suppression effect of the common mode, the present invention utilizes the characteristics of the POS to perform a common mode operation, and loads a high-impedance open-circuit stub (50) at the center of the resonator A at the output end to increase the zero-point mechanism to achieve a total suppression. The mode is shown in the fourth figure. When the differential mode is operated, the POS is regarded as a short-circuit ground. The high-impedance open-circuit stub (50) will not affect the signal transmission, so it will not affect the differential mode.

In addition, in practice, in order to have enough space to accommodate and weld the SMA joint, the feed line is bent at 45° and extended out, and the final adjustment is made. The actual size of the circuit is as shown in the first figure.

Please refer to the fifth and fifth B diagrams for the frequency response diagram of the balanced dual-band pass filter simulation and measurement. In the differential mode operation, the center of the first frequency band and the second frequency band measurement (analog) The frequencies are 2.44 (2.44), 5.24 (5.24) GHz, and the 3dB bandwidth is 2.39-2.51 (2.4-2.5) and 5.13-5.4 (5.13-5.41) GHz. The insertion loss measurement (analog) minimum is 2.09 (1.7), 2.15 (1.33) dB. In the common mode operation, the insertion loss of the measurement (analog) in the frequency range of 1-7 GHz is greater than 20 dB, and the total circuit area does not include the feed line area of 16.35 × 20.5 mm ² , as shown in the sixth figure.

The foregoing is a description of the preferred embodiments of the present invention, and the invention can be modified and modified without departing from the spirit and scope of the invention. Changes and modifications are to be covered in the scope defined by the scope of the patent application below.

(10). . . First stepped impedance resonator

(20). . . Second step stepped impedance resonator

(30). . . First T-type resonator

(40). . . Second T-type resonator

(50). . . High impedance open circuit segment

(70). . . First plane of symmetry

(80). . . Second plane of symmetry

(90). . . Microwave substrate

(L11). . . First size

(L12). . . Second size

(L13). . . Third size

(L14). . . Fourth size

(L15). . . Fifth size

(L16). . . Sixth size

(L21). . . Seventh size

(L22). . . Eighth size

(L23). . . Ninth size

(L24). . . Tenth size

(L31). . . Eleventh size

(L32). . . Twelfth size

(L33). . . Thirteenth size

(L34). . . Fourteenth size

(L35). . . Fifteenth size

(L51). . . Sixteenth size

(L52). . . Seventeenth size

(M _AB =M _BA ). . . Coupling coefficient

(S). . . Coupling pitch

(t). . . Feeding position

(A). . . Resonator A

(B). . . Resonator B

( ). . . Common mode input reflection coefficient

( ). . . Common mode forward transmission coefficient

( ). . . Differential mode input reflection coefficient

( ). . . Differential mode forward transmission coefficient

( ). . . Signal input

( ). . . Signal input

( ). . . Signal output

( ). . . Signal output

The first figure is a balanced dual-band pass filter architecture diagram of the present invention.

Second figure: A modal analysis diagram of the T-type resonator of the present invention.

Figure 3A is a graph showing the coupling coefficient versus coupling pitch variation of the present invention.

Figure 3B is a graph of the external quality factor versus feed position variation of the present invention.

Figure 4 is a comparison of common mode response usage and unused open circuit segments of the present invention.

Figure 5A is a differential mode frequency response diagram of the analog dual-band pass filter simulation and measurement of the present invention.

Figure 5B is a common mode frequency response diagram of the analog dual-band pass filter simulation and measurement of the present invention.

Fig. 6 is a comparison photograph of a balanced dual-band pass filter implementation circuit of the present invention and a coin.

(10). . . First stepped impedance resonator

(20). . . Second step stepped impedance resonator

(30). . . First T-type resonator

(40). . . Second T-type resonator

(50). . . High impedance open circuit segment

(70). . . First plane of symmetry

(80). . . Second plane of symmetry

(90). . . Microwave substrate

(L11). . . First size

(L12). . . Second size

(L13). . . Third size

(L14). . . Fourth size

(L15). . . Fifth size

(L16). . . Sixth size

(L21). . . Seventh size

(L22). . . Eighth size

(L23). . . Ninth size

(L24). . . Tenth size

(L31). . . Eleventh size

(L32). . . Twelfth size

(L33). . . Thirteenth size

(L34). . . Fourteenth size

(L35). . . Fifteenth size

(L51). . . Sixteenth size

(L52). . . Seventeenth size

( ). . . Signal input

( ). . . Signal input

( ). . . Signal output

( ). . . Signal output

Claims (8)

A balanced dual-band pass filter with a T-type and λ/2 step impedance resonator (SIR) for suppressing common mode signals includes: a microwave substrate; a first step impedance resonator, The first stepped impedance resonator is a half-wave two-step impedance resonator disposed on a left half plane of the surface of the microwave substrate; a second step impedance resonator, the second step impedance resonance The device is also a half-wavelength (λ/2) two-step impedance resonator, and has the same structure as the first stepped impedance resonator, and is disposed on the right half plane of the surface of the microwave substrate, and is a second The symmetric plane is symmetrically arranged with the first-order stepped impedance resonator, and the second stepped impedance resonator is loaded with a high-impedance open-circuit residual section; a first T-type resonator, the first T-type resonance Short-circuited at both ends of the device, disposed on the upper half plane of the surface of the microwave substrate; and a second T-type resonator, the second T-type resonator is short-circuited at both ends, and the structure is completely the same as that of the first T-type resonator Disposed on a lower half plane of the surface of the microwave substrate and in a first pair A first plane and the T-shaped resonators disposed symmetrically goes lower, wherein the open stub may be provided between a transmission zero in the 3.85 GHz, whereby the common mode signal to inhibit head to. A balanced dual-band pass filter for suppressing common mode signals is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 1 of the patent application, wherein the high-impedance open-circuit stub is provided. The sixteenth dimension is 2.7 mm and the seventeenth dimension is 1.4 mm. A balanced dual-band pass filter for suppressing common mode signals is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 1, wherein the first and second steps are The impedance of the impedance resonator is 60Ω. A balanced dual-band pass filter for suppressing common mode signals is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 1, wherein the first and second T-type resonances are used. The high impedance of the device is 22Ω. A balanced dual-band pass filter for suppressing common mode signals is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 1, wherein the first and second steps are The impedance ratio of the impedance resonator and the first and second T-type resonators is 2.42. A balanced dual-band pass filter for suppressing common mode signals is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 1, wherein the microwave substrate has a thickness of 0.635 mm. The dielectric constant is 10.2 and the loss tangent is 0.0023. A balanced dual-band pass filter for suppressing common mode signals is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 1, wherein the first and second steps are The impedance resonator has the same resonant frequency as the first and second T-type resonators, and each of the resonant frequencies is a center frequency of the first and second frequency bands. A balanced dual-band pass filter with a common mode signal is designed with a T-type and a λ/2 stepped impedance resonator (SIR) as described in claim 7 of the patent application, wherein the centers of the first and second frequency bands are The frequencies are 2.45 GHz and 5.25 GHz, respectively.