RF滤波器结构学习.docx

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1、Stub-loaded resonators, which have an easily controlled resonant frequency, have been applied to normal conductor DBPFs 3 -5.支节加载谐振器，由于很容易控制其中心频率，故它已经应用在普通的双通带滤 波器中。They have two resonance modes of even and odd modes. The even-mode resonant frequency can be easily tuned while keeping the odd-mode on

2、e basically the same. However, it is difficult to keep the even-mode one basically the same while tuning the odd-mode one.它有两种谐振模式:奇模和偶模，在保持奇模谐振频率不变的前提下很容易来调 节和控制偶模谐振频率。但是在偶模不变的情况下，却很难改变奇模的谐振频率。Fig. 1. (a) ConfigLirarjoji of proposed du a I-band resonator, (b) odd-mode, and (c) even-mode excitation.

3、Therefore, we proposed a novel dual-band bandpass stub-loaded resonator which can be independently controlled of the resonant frequency of the even and odd modes 11, 12.因此，我们提出了一种新型的双通带滤波器，采用支节加载的方式可以独 立控制奇模和偶模的谐振频率。Fig. 1(a) shows the configuration of the dual-band bandpass stub-loaded resonator we

4、 developed. It consists of a meander open-loop resonator and an open stub. The meander resonator is used for not only miniaturizing the dual-band resonator size but also decreasing the space between resonators due to weak coupling property.图1.a给出了双通带支节加载谐振器的结构图。它包含一个弯曲的开环谐振器 和一个开路支节；那个弯折的谐振器不仅可以减小双通

5、带滤波器的尺寸，而且可 以减小由于弱耦合特性谐振器之间的空间。This symmetric configuration enables analysis in terms of even- and odd- mode excitations (the A-A plane behaves as an electric/magnetic wall for odd/even excitation). Fig. 1(b) and (c) show the odd-mode excitation and even-mode excitation. 这种对称的电路结构可以使用奇偶模分析的方法，奇模时对应于

6、电壁，偶模时对应于磁壁。For odd-mode excitation, there is a voltage null along the middle of the resonator, as shown in Fig. 1(b). Hence, the tapping point of the stub is actually a virtual ground for the odd-mode. As a consequence, the stub does not affect the odd mode resonant frequency. For even-mode excitat

7、ion, there is no current flow through the symmetrical plane. Thus, we can bisect the circuit with open circuits at the A-Aplane, so that an even mode resonator which is constructed with meander line and the open stub is obtained, as shown in Fig. 1(c).对于奇模激励下，谐振器的中点相当于是电压的零点。因此支节加载的那个点对于偶模来 说相当于是接地点

8、，结论就是支节的长度不影响偶模的谐振频率。对于在偶模激励下，没 有电流在对称平面上流动。故可以把电路看作是从中间开路，因此，可以获得由曲折线和 开路的支节构成的偶模谐振器，The odd-mode resonant frequency was mainly determined by the length of the meander open-loop resonator see Fig. 1(b). The configuration of the proposed resonator for three values of length L2, and the simulated res

9、onant frequency responses for the three values are plotted in Fig. 2. Increasing L2 from 0.3 to 1.5 mm effectively shifted the odd-mode resonant frequency 250 MHz while leaving the even-mode resonant frequency basically the same. This is because the electrical length of even mode resonance was not c

10、hanged, as shown in Fig. 2, and the stub does not affect the odd-mode resonant frequency.奇模谐振频率主要是由弯折的开环谐振器的长度决定的，正是谐振器参数中的L2控制的， 通过改变L2的长度，保持L1的长度不变，可以发现仅影响第一个谐振频率，第二个不变，Fig. 2. Configuration of proposed resonator with length Lq of 0.3, 0.9.1.5 mm and simulated resonant frequency responses for diff

11、erent values of h如Fig. 3. Coniiguration of proposed rcsojmtor with length of 4.55, 4.05.3.55 mm and si mu J ate d resonant frequency response fbr different values of Li.The even-mode resonant frequency is mainly determined by the total length of the meander open-loop resonator and stub see Fig. 1(c)

12、. The configuration of the proposed resonator for three values of length L1, and the simulated resonant frequency responses for the three values are plotted in Fig. 3. Reducing L1 from 4.55 to 3.55 mm without changing L2 e ffectively shifted the even-mode resonant frequency 407 MHz while leaving the

13、 odd-mode resonant frequency basically the same. This is because the electrical length of odd-mode resonance was not changed, as shown in Fig. 3, and the stub does not affect the odd-mode resonant frequency.偶模谐振频率主要是由 弯折开路环和加载的支节决定，也就是L1参数，改变L1,保持L2不变，可以发现奇模谐振0.02QaI i h I I I 1 I 1 I I i 0.0150.010

14、.005-1J0.20.250.30.355 4r5O,d mm频率不变。The designed center frequencies of the first and second bands were set to 3.5 and 5.0 GHz. A lowpass prototype Chebyshev response with a 0.1-dB ripple was used. The designed bandwidths of both bands were set to the same fractional bandwidth, 2%.Since the fraction

15、al bandwidths of the two bands were the same, the coupling coefficients for the two bands were the same (K12 = K23 = M12 = M23 = 0.018), respectively. Note that once the couplingSimulated coupling coefficients for two resonators as a function of d.coefficient of one band has been set, that of the ot

16、her bandis determined. Thus, it is verydifficult to flexibly control theI mmFig. 5. (a) Layout of coupling resonators and additional capacitance-loaded microstrip line, (b) Simulated coupling coefficients of a pair of proposed resonators with additional microstrip line as a function of Lcoupling coe

17、fficients of both bands when a conventional DBPF is used.第一个通带的耦合系数 0.018是通过调节耦合间距 d来实现的（d=0.35mm）, 在不影响第一通带耦合系 数的前提下，通过增加附加 的微带传输线来减小第二 通带的耦合强度。在没有加微带线的前提下， 第二通带的耦合主要是磁 耦合，因此要增加电耦合来 减弱原来的耦合。To overcome this problem, we introduced an additional capacitance-loaded microstrip line to enable the coupli

18、ng coefficients to be flexibly controlled. The idea is to control the first band coupling coefficient mainly by adjusting the distance between the resonators and to control the second one by adjusting the structural parameters of the additional microstrip line while the coupling coefficient of the f

19、irst band remains basically the same. To achieve the required coupling coefficient of 0.018 for the first band, we first set distance d between the resonators to 0.35 mm on the basis of the relationship shown in Fig. 4. To obtain the same coupling coefficient of the first and second band, we had to

20、decrease the second band coupling coefficient by adding the additional microstrip line between coupled resonators which did not affect the first band coupling coefficient. We previously reported an H-shaped waveguide placed between combline coupled resonators is an effective method to decrease the t

21、otal coupling coefficient without changing the space between resonators if the coupling with and without the H-shaped waveguide have different signs 15. The sign of the coupling coefficient was obtained from the simulated phase of the transmission response referred from elsewhere 14. The simulated c

22、oupling coefficient of the second band without the additional microstrip line with a distance d = 0.35 mm is positive (mixed coupling, but magnetic dominant). Thus, we should introduce negative coupling (electric coupling) to decrease it.The coupling between the resonators is controlled by adjusting

23、 additional microstrip line length l, the gap between the microstrip line and each resonator, and the width of the microstrip line. We set the coupling gap to 0.1 mm and the microstrip line width to 0.2 mm. The coupling coefficients of the resonators with an additional capacitance-loaded microstrip line between them as a function of l are shown in Fig. 5(b). The coupling coefficient of the second band was decreased substantially while that of the first band remained basically the same.L1的上下平面是不变的，即保持L1的长度不变。变化的是L2,故变量的参考点选择很重要， 改变L2的长度，11-12的长度随之改变。4.25l122.352.35U.D2.35产5/.25 .1.