CN202363565U - High-selectivity double-band-pass filter with independently tunable passbands - Google Patents

Abstract

The utility model discloses a high-selectivity double-bandpass filter with independently adjustable passbands, which comprises an upper-layer microstrip structure, a middle-layer dielectric substrate and a lower-layer grounding metal plate. The filter is composed of four resonators, each resonator includes a microstrip line and a varactor diode, each resonator is a quarter-wavelength resonator, and is arranged symmetrically about the central longitudinal axis of the microstrip structure. The first resonator and the second resonator use the microstrip line directly connected to the resonator and coupled in parallel with the resonator as the feed structure, and the third and fourth resonators use a microstrip line coupled in parallel with the resonator The wire serves as the feed structure. In addition, the utility model adopts a pseudo-interdigitated structure to generate a transmission zero point, so that the filter has higher selectivity. The utility model has the characteristics of adjustable center frequency of double-pass bands and independent tuning.

Description

Highly Selective Dual Bandpass Filters with Independently Adjustable Passbands

technical field

The utility model relates to a double-bandpass filter with adjustable center frequency, in particular to an adjustable double-bandpass filter which does not affect each other when the center frequency is tuned and can be applied to radio frequency front-end circuits. device.

Background technique

In today's society, with the development of wireless communication, the design of low-cost, high-performance reconfigurable RF subsystem has become a hot issue. Reconfigurable communication systems have an extremely urgent need for tunable filters that can cover a large frequency range.

At present, many researchers have used many different adjustment devices for the design of adjustable band-pass filters, among which there are several typical methods. The first method is to change the length of the resonator through a varactor diode to change the resonant frequency, such as J.Long and C.Z.Li, "A tunable microstrip bandpass filter with two independently adjustable transmission zeros," IEEE Microw.Wireless Compon. Lett., vol.21, no.2, pp.74-76, Feb.2010.5±0.5? ? . The second method is to use a PIN diode structure to design an adjustable bandpass filter, such as G.L.Dai and M.Y.Xia, "Design of compact dual-band switchable bandpass filter," Electronics Letters, vol.45, no.10, pp.506 -507, May.2009. The third method is to use ferrite components to design tunable filters, such as M. Norling, D. Kuylenstierna, A. Vorobiev, and S. Gevorgian, "Layout optimization of small-size ferroelectric parallel-plate varactors," IEEE Trans. Microw .Theory Tech., vol.58, no.6, pp.1475-1484, June.2010. What the utility model adopts is the first method—using a varactor diode to change the resonant frequency.

At this stage, single pass band tunable filters have attracted a lot of attention. Such as V.Sekar, M.Armendariz, and K.Entesari. "A 1.2-1.6 GHz substrate-integrated-waveguide RF MEMS tunable filter," IEEE Trans. Microw. Theory Tech., vol.59, no.4, pp.866- 876, Apr. 2010.5 ± 0.5. In order to further optimize the performance of the single passband tunable filter, domestic researchers use lumped elements to suppress the harmonics of the passband. Such as X.Y.Zhang and Q.Xue, "High-selectivity tunable bandpass filters with harmonic suppression," IEEE Trans. Microw. Theory Tech., vol.58, no.4, pp.964-969, Apr.2010. However, the single passband tunable filter can only be tunable in a single frequency range, so its frequency coverage is very limited. In order to solve this problem, the utility model provides a high-selectivity dual-bandpass filter with independently adjustable passbands.

Utility model content

The purpose of the utility model is to overcome the above-mentioned deficiencies in the prior art, and provide a highly selective dual-bandpass filter with independently adjustable passbands.

For realizing the utility model purpose, the technical scheme that the utility model adopts is as follows:

A highly selective dual bandpass filter with independently adjustable passbands, including an upper microstrip structure, an intermediate dielectric substrate and a lower grounded metal plate; the upper microstrip structure is attached to the upper surface of the intermediate dielectric substrate, and the lower grounded metal plate is attached On the lower surface of the intermediate dielectric substrate; the upper microstrip structure includes a port feeder line, a port microstrip line and four resonators; the four resonators are quarter-wavelength resonators, and the four resonators are arranged symmetrically The structure of the upper two resonators is the same, the lower two resonators have the same structure, the port microstrip line is located between the upper two resonators and the lower two resonators, and the upper two resonators The resonator is directly connected to the port feeder and coupled in parallel, and the two lower resonators are coupled in parallel to the port feeder. The coupling mode between the first resonator, the second resonator, the third resonator and the fourth resonator and the port feeder is a coupling mode in which electric coupling and magnetic coupling are mixed.

In the above-mentioned high-selectivity dual-bandpass filter with independently adjustable passband, the first resonator located on the upper left includes a first varactor diode, a coupled microstrip line part and an uncoupled microstrip line part, wherein the coupled microstrip line The line part is formed by sequentially connecting the fourth microstrip line, the fifth microstrip line and the sixth microstrip line, and the uncoupled microstrip line part includes the first microstrip line, the second microstrip line and the third microstrip line, One end of the first microstrip line is connected to the cathode of the first varactor diode, and the anode of the first varactor diode is connected to the ground metal of the lower layer through a capacitor through a metallized via hole passing through the intermediate dielectric substrate. The first microstrip line , the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line and the sixth microstrip line are connected in sequence, and the end of the sixth microstrip line passes through the metallization process of the intermediate dielectric substrate The hole is connected to the ground metal of the lower layer; the third resonator located at the lower left includes the third varactor diode and the coupling microstrip line part, wherein the coupling microstrip line part is sequentially connected by the tenth microstrip line and the eleventh microstrip line. One end of the tenth microstrip line is connected to the cathode of the third varactor diode, and the anode of the third varactor diode is connected to the ground metal of the lower layer through a capacitor through a metallized via hole passing through the intermediate dielectric substrate. The tenth microstrip line The other end of the strip line is connected to one end of the eleventh microstrip line; the other end of the eleventh microstrip line passes through the metallized via hole of the intermediate dielectric substrate and is connected to the ground metal of the lower layer.

In the above-mentioned highly selective dual-bandpass filter with independently adjustable passbands, the electrical length L+ΔL of the resonator located at the upper left is a quarter of the wavelength λ corresponding to the low resonance frequency f of the dual-bandpass filter One; where, L is the actual microstrip line length, ΔL is the first varactor diode equivalent microstrip line length of the first resonator on the upper left; the actual microstrip line length L is the first microstrip line, the second The sum of the lengths of the microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line and the sixth microstrip line; the length of the coupling section is equal to the fourth microstrip line, the fifth microstrip line and the sixth microstrip line The sum of the lengths of the six microstrip lines; the electrical length L'+ΔL' of the resonator located at the bottom left is a quarter of the wavelength λ' corresponding to the high resonant frequency f' of the double bandpass filter, where L' is the actual microstrip line length, ΔL' is the third varactor diode equivalent microstrip line length of the third resonator on the lower left; the actual microstrip line length L' is the tenth microstrip line, the eleventh microstrip line The sum of the lengths; the length of the coupling interval is equal to the sum of the lengths of the tenth microstrip line and the eleventh microstrip line.

In the above-mentioned high-selectivity dual-bandpass filter with independently adjustable passbands, the coupled microstrip line part of the resonator at the upper left is sequentially connected by the fourth microstrip line, the fifth microstrip line and the sixth microstrip line An n-shaped structure is formed, and the coupling microstrip line part of the resonator located at the lower left is sequentially connected by the tenth microstrip line and the eleventh microstrip line to form an L-shaped structure.

In the above-mentioned high-selectivity double-bandpass filter with independently adjustable passband, the port feeder includes a coupled feeder part and a non-coupled feeder part, wherein the coupled feeder part includes upper and lower parts, and the upper part is composed of the first The seventh microstrip line, the eighth microstrip line and the ninth microstrip line are connected in sequence; the seventh microstrip line is connected to the fourth microstrip line to achieve a stronger coupling between the feeder line and the resonator; the lower part consists of the second The thirteenth microstrip line and the fourteenth microstrip line are connected in sequence; the uncoupled feeder line part of the port feeder line is composed of the twelfth microstrip line; the coupled feeder line part of the port feeder line and the resonator coupled microstrip line part There is an electromagnetic coupling gap with a width of 0.2±0.05mm between them; the port microstrip line part includes the sixteenth microstrip line; the first resonator and the second resonator are located above the sixteenth microstrip line, and the third resonator , The fourth resonator is located below the sixteenth microstrip line.

In the above-mentioned high-selectivity double-bandpass filter with independently adjustable passband, the upper part of the coupled feeder of the port feeder is composed of the seventh microstrip line, the eighth microstrip line and the ninth microstrip line connected in sequence shaped structure, located inside the n-shaped structure of the first resonator coupling microstrip line part; The six microstrip lines are parallel; the lower part of the coupling feeder line of the port feeder line is sequentially connected by the thirteenth microstrip line and the fourteenth microstrip line to form an L-shaped structure, which is located inside the L-shaped structure of the part of the resonator coupling microstrip line ; The thirteenth microstrip line and the fourteenth microstrip line are parallel to the tenth microstrip line and the eleventh microstrip line respectively.

In the above-mentioned highly selective dual-bandpass filter with independently adjustable passbands, the adjustable resonant frequency ranges of the adjustable dual-bandpass filter are 570-690MHz and 1.156-1.336GHz respectively, and the first microstrip line The length is 2.6±0.2mm, the length of the second microstrip line is 12.4±0.3mm, the length of the third microstrip line is 3.0±0.1mm, the length of the fourth microstrip line is 13.6±0.2mm, the fifth microstrip line The length of the line is 9.1±0.4mm, the length of the sixth microstrip line is 14.1±0.3mm, the coupling distance between the four resonators and the port feeder is 0.2±0.05mm, the first microstrip line, The width of the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line and the sixth microstrip line is 0.7±0.1mm, and the width of the seventh microstrip line, the eighth microstrip line and the The width of the ninth microstrip line is 0.9mm, the width of the sixteenth microstrip line is 1.84mm, and the characteristic impedance of the sixteenth microstrip line is 50Ω; the lengths of the tenth microstrip line and the eleventh microstrip line are respectively 10.5±0.5mm and 7.0±0.4mm, the gap between the tenth microstrip line and the thirteenth microstrip line is 0.2±0.05mm; between the first resonator, the second resonator, the third resonator, and the fourth resonator The gap between them is 0.4mm; the length of the fifteenth microstrip line is 1.8±0.2mm, and the distance between each microstrip line is 0.2±0.05mm; the varactor diodes of the first resonator and the second resonator are set With the same bias voltage, the varactor diodes of the third resonator and the fourth resonator are set with the same bias voltage.

In addition, the fifteenth microstrip line uses six microstrip lines to form a pseudo-interdigitated structure to generate transmission zeros to enhance the selectivity of the passband.

Compared with the prior art, the utility model has the following advantages:

(1) Has two adjustable passbands. For ordinary adjustable bandpass filters, there is often only one adjustable passband. However, the utility model realizes two adjustable passbands, thereby greatly increasing the frequency coverage of the filter.

(2) Independent tuning can be realized between the two passbands without mutual influence. In the utility model, when the central frequency of one adjustable passband is changed, the other passband is not affected, and independent tuning is completely realized. It can make the two passbands work more stably.

Description of drawings

Figure 1 is a block diagram of a highly selective dual bandpass filter with independently adjustable passbands.

Fig. 2 is the topological structure of adjustable double band-pass filter.

Fig. 3a is an equivalent schematic diagram of the electromagnetic coupling structure of the tunable dual bandpass filter.

Fig. 3b is an equivalent circuit diagram of a resonator of an adjustable dual bandpass filter under different bias voltages.

Fig. 4 is a structural schematic diagram of a highly selective dual-bandpass filter with independently adjustable passbands.

Fig. 5a is a simulation curve diagram of the transmission characteristic of the low-pass band part of the adjustable dual-band-pass filter when the central frequency is changed.

Fig. 5b is a simulation curve diagram of the transmission characteristic of the high-pass band part of the adjustable dual-band-pass filter when the center frequency is changed.

Fig. 6a is an actual measurement curve of the transmission characteristic of the adjustable double-bandpass filter with the center frequency changed in the low-passband part.

Fig. 6b is an actual measurement curve of the transmission characteristic when the high-pass band part of the adjustable dual-band-pass filter changes the central frequency.

Detailed ways

The utility model will be described in further detail below in conjunction with the accompanying drawings, but the scope of protection claimed by the utility model is not limited to the scope of the following examples.

As shown in Figure 1, a highly selective dual-bandpass filter with independently adjustable passbands includes an upper microstrip structure, an intermediate dielectric substrate, and a lower grounded metal plate; the upper microstrip structure is attached to the upper surface of the intermediate dielectric substrate , the lower ground metal plate is attached to the lower surface of the intermediate dielectric substrate; the upper microstrip structure includes port feeders, port microstrip lines and four resonators; the four resonators are quarter-wavelength resonators, and the four resonators The resonators are arranged in a left-right symmetrical structure, the first resonator and the second resonator at the top have the same structure, the third resonator and the fourth resonator at the bottom have the same structure; the first resonator at the upper left includes the first Varactor diode 17, coupled microstrip line part and uncoupled microstrip line part; the coupled microstrip line part of the first resonator consists of the fourth microstrip line 4, the fifth microstrip line 5 and the sixth microstrip line 6 in sequence Connected into an n-shaped structure; the uncoupled microstrip line part of the resonator includes the first microstrip line 1, the second microstrip line 2, and the third microstrip line 3; one end of the first microstrip line 1 is connected to the first varactor The cathode of the diode 17 is connected, the anode of the first varactor diode 17 is connected to the ground metal of the lower layer through a metallized via hole passing through the intermediate dielectric substrate through a capacitor, the first microstrip line 1, the second microstrip line 2, the second microstrip line The third microstrip line 3, the fourth microstrip line 4, the fifth microstrip line 5 and the sixth microstrip line 6 are connected in sequence, and the end of the sixth microstrip line 6 passes through the metallized via hole of the intermediate dielectric substrate and the lower layer The ground metal is connected; the third resonator located at the lower left includes the third varactor diode 18 and the coupled microstrip line part, and the coupled microstrip line part of the third resonator is composed of the tenth microstrip line 10 and the eleventh microstrip line 11 are sequentially connected to form an L-shaped structure; one end of the tenth microstrip line 10 is connected to the cathode of the third varactor diode 18, and the anode of the third varactor diode 18 passes through a capacitor through a metallized via hole passing through the intermediate dielectric substrate The other end of the tenth microstrip line 10 is connected to the eleventh microstrip line 11; the other end of the eleventh microstrip line 11 passes through the metallized via hole of the intermediate dielectric substrate and is connected to the underlying ground metal .

The port feeder includes a coupled feeder part and an uncoupled feeder part, wherein the coupled feeder part includes upper and lower parts, and the upper part of the coupled feeder consists of the seventh microstrip line 7, the eighth microstrip line 8 and the second microstrip line. Nine microstrip lines 9 are sequentially connected to form an n-shaped structure, which is located inside the n-shaped structure of the first resonator coupling microstrip line; the seventh microstrip line 7, the eighth microstrip line 8 and the ninth microstrip line 9 are respectively connected to The fourth microstrip line 4, the fifth microstrip line 5 and the sixth microstrip line 6 are parallel; the seventh microstrip line 7 is connected to the fourth microstrip line 4 to achieve stronger coupling between the feeder line and the resonator; The lower part of the coupling feed line is connected in turn by the twelfth microstrip line 12, the thirteenth microstrip line 13 and the fourteenth microstrip line 14 to form an n-shaped structure, which is located inside the L-shaped structure of the resonator coupling microstrip line part The thirteenth microstrip line 13 and the fourteenth microstrip line 14 are parallel to the tenth microstrip line 10 and the eleventh microstrip line 11 respectively; the uncoupled feeder line part of the port feeder line includes the sixteenth microstrip line 16. The first resonator and the second resonator are located above the sixteenth microstrip line 16 , and the third resonator and the fourth resonator are located below the sixteenth microstrip line 16 . The characteristic impedance of the sixteenth microstrip line 16 is 50Ω; an electromagnetic coupling spacing with a width of 0.2±0.05mm is set between the resonator coupling microstrip line part and the port feeder coupling feeder line part to realize electromagnetic coupling; the electromagnetic coupling spacing It depends on the strength of coupling.

调整谐振器的第一变容二极管17的偏置电压，则第一变容二极管17的等效电容会发生改变，其等效微带线长度也会随之改变，从而谐振频率发生变化；如图3b所示，当第一变容二极管17的等效电容C_v1＞C_v2时，对应的等效微带线长度ΔL₁＞ΔL₂，对应的谐振频率f₁＜f₂。因此通过调整第一变容二极管17的偏压，可以调整通带滤波器的中心频率。选定第一变容二极管17和确定滤波器工作的谐振频率调谐范围最小f_min和最大f_max之后，可以确定第一变容二极管17的等效微带线长度的变化范围，然后根据等效微带线的总长度为四分之一波长的特性就可以确定实际微带线的长度L。实际上部分微带线长度L₁为图1中第一微带线1、第二微带线2、第三微带线3、第四微带线4、第五微带线5和第六微带线6的长度之和。同理，下部分微带线长度L₂为图1中第十微带线10、第十一微带线11的长度之和。The first resonator is composed of a microstrip line and a first varactor diode 17, one end of the microstrip line is connected to the cathode of the first varactor diode 17, and the other end passes through a metallized via hole in the intermediate dielectric substrate and is connected to the lower ground metal; The lengths of the first microstrip line 1, the second microstrip line 2, the third microstrip line 3, the fourth microstrip line 4, the fifth microstrip line 5 and the sixth microstrip line 6 of the first resonator are summed The total length of the equivalent microstrip line of the first varactor diode 17 is a quarter wavelength corresponding to the lower resonance frequency of the filter. The resonance frequency of the first resonator is mainly adjusted by the bias voltage of the first varactor diode 17 . When the parasitic effect is neglected, the first varactor diode 17 can be equivalent to a section of microstrip line with an open terminal. As shown in Figure 3a, the oblique area indicates that the actual length of the microstrip line is L; the first varactor diode 17 is equivalent to a microstrip line with a length ΔL; the electrical length L+ΔL of the first resonator is the resonant frequency f A quarter of the corresponding wavelength λ; the resonant frequency f is inversely proportional to the electrical length, that is

Adjust the bias voltage of the first varactor diode 17 of the resonator, then the equivalent capacitance of the first varactor diode 17 will change, and its equivalent microstrip line length will also change accordingly, so that the resonance frequency will change; As shown in FIG. 3 b , when the equivalent capacitance C _v1 >C _v2 of the first varactor diode 17 , the corresponding equivalent microstrip line length ΔL ₁ >ΔL ₂ , and the corresponding resonant frequency f ₁ <f ₂ . Therefore, by adjusting the bias voltage of the first varactor diode 17, the center frequency of the passband filter can be adjusted. After selecting the first varactor diode 17 and determining the minimum f _min and maximum f _max of the resonant frequency tuning range of filter operation, the variation range of the equivalent microstrip line length of the first varactor diode 17 can be determined, and then according to the equivalent The characteristic that the total length of the microstrip line is a quarter wavelength can determine the length L of the actual microstrip line. Actually part of the microstrip line length L ₁ is the first microstrip line 1, the second microstrip line 2, the third microstrip line 3, the fourth microstrip line 4, the fifth microstrip line 5 and the sixth microstrip line in Fig. 1 The sum of the lengths of the microstrip lines 6. Similarly, the length L ₂ of the lower part of the microstrip line is the sum of the lengths of the tenth microstrip line 10 and the eleventh microstrip line 11 in FIG. 1 .

The coupling mode adopted by the resonator of the high-selectivity dual band-pass filter with independently adjustable pass bands and the port feeder is a hybrid electromagnetic coupling mode. As shown in Figure 1, the coupling structure of the upper part consists of the fourth microstrip line 4, the fifth microstrip line 5, the sixth microstrip line 6, the seventh microstrip line 7, the eighth microstrip line 8, the ninth microstrip line Composed of striplines 9, the coupling structure of the lower part is composed of the tenth microstrip line 10, the eleventh microstrip line 11, the twelfth microstrip line 12, the thirteenth microstrip line 13, and the fourteenth microstrip line 14 . The upper part adopts the access coupling structure as the feed structure corresponding to the low-pass band resonator. This is because the coupling between the resonator and the feeder can be effectively enhanced by adopting the access structure. The quality factor Q _e of the low passband is mainly composed of the gap between the fourth microstrip line 4 and the seventh microstrip line 7, the position where the seventh microstrip line 7 is connected to the fourth microstrip line 4, the fourth microstrip line 4 and the line width of the seventh microstrip line 7 are determined. The coupling coefficient between the first resonator and the second resonator in the upper part is determined by the width of the gap between them and the length of the sixth microstrip line 6 . The lower part corresponds to the high passband part of the filter characteristic curve. The quality factor of the high-pass band is mainly determined by the distance between the thirteenth microstrip line 13 and the tenth microstrip line 10 , and the length of the thirteenth microstrip line 13 and the fourteenth microstrip line 14 . The coupling coefficient between the third resonator and the fourth resonator is determined by the width of the gap between them and the length of the eleventh microstrip line 11 . As shown in Figure 2, J′ _0,1 , J′ _1,2 , J′ _2,3 , J″ _0,1 , J″ _1,2 , J″ _2,3 respectively represent the first port and the first resonance conductor, the first resonator and the second resonator, the second resonator and the second port, the first port and the third resonator, the third resonator and the fourth resonator, the fourth resonator and the second port Nano-inverted converter; G represents the characteristic admittance of the input and output ports; Z _coupling represents the impedance coupling matrix of the filter; L′ ₁ , L′ ₂ , L′ ₃ , L′ ₄ represent the first resonator and the second resonator respectively The equivalent inductance of the third resonator, the fourth resonator; C′ ₁ , C′ ₂ , C′ ₃ , C′ ₄ represent the first resonator, the second resonator, the third resonator, the The equivalent capacitance of the resonator; the utility model adopted a parallel feed structure, so the quality factor Qe and the coupling coefficient k of the upper and lower passbands are independent of each other. In addition, the utility model adopts a pseudo-interdigitated structure to generate transmission The coupling strength of the pseudo-interdigitated structure is determined by the number, length and gap width of the fifteenth microstrip lines 15 .

Example

The structure of a highly selective dual-bandpass filter with independently adjustable passbands is shown in Figure 1, and the relevant dimensions are shown in Figure 4 below. The thickness of the dielectric substrate is 0.81mm, the relative permittivity is 3.38, and the loss tangent is 0.0027. The serpentine structure of the resonator can effectively reduce the size of the filter. The first varactor diode 17, the second varactor diode 19, the third varactor diode 18, and the fourth varactor diode 20 adopt Toshiba's 1sv277, and the negative pole of the first varactor diode 17 is connected to one end of the microstrip line, and the other end passes through a The metallized via hole passing through the intermediate dielectric substrate is connected to the ground metal of the lower layer. As shown in Figure 4, the size parameters of the microstrip lines of the filter are as follows: the length of the first microstrip line 1 is L ₅ =2.6±0.2mm, and the length of the second microstrip line 2 is L ₄ =12.4±0.3mm , the length of the third microstrip line 3 is L ₃ =3.0±0.1mm, the length of the fourth microstrip line 4 is L ₂ =13.6±0.2mm, and the length of the fifth microstrip line 5 is L ₁ =9.1±0.4 mm, the length of the sixth microstrip line 6 is L ₁ +W ₁ +W ₂ +g ₂ =14.1±0.3mm, the coupling distance between the resonator and the port feeder is g ₂ =g ₄ =0.2±0.05mm , the width of the first microstrip line 1, the second microstrip line 2, the third microstrip line 3, the fourth microstrip line 4, the fifth microstrip line 5 and the sixth microstrip line 6 is W ₁ =0.7± 0.1mm, the width of the seventh microstrip line 7, the eighth microstrip line 8 and the ninth microstrip line 9 is W ₂ =0.9mm, the width of the sixteenth microstrip line 16 is W ₅ =1.84mm, the tenth microstrip line The characteristic impedance of the six microstrip lines 16 is 50Ω. The lengths of the tenth microstrip line 10 and the eleventh microstrip line 11 are L ₉ =10.5±0.5 mm and L ₈ +W ₄ +W ₆ +g ₄ =7.0±0.4 mm, respectively. The width of the tenth microstrip line 10 and the eleventh microstrip line 11 is W ₆ =0.7±0.1mm, the width of the twelfth microstrip line 12 , the thirteenth microstrip line 13 and the fourteenth microstrip line 14 W ₄ =0.3±0.1mm. The gap between the two resonators is g ₁ =g ₅ =0.3±0.1 mm. The length of the fifteenth microstrip line 15 is L ₇ =1.8±0.2 mm, and the gap between each microstrip line is g ₃ =0.2±0.05 mm. The respective length and width of these microstrip lines are selected to obtain the desired input/output impedance characteristics, in-band transmission characteristics, and out-of-band attenuation characteristics. Figure 5a and Figure 5b are the simulation results when the center frequency of the low-pass band and high-pass band of the adjustable double-bandpass filter designed according to the above parameters is changed; the horizontal axis in the output characteristic curve represents the frequency, and the vertical axis represents Transmission characteristics S ₂₁ , S ₁₁ ; the dotted line is the simulation result of S ₁₁ , and the solid line is the simulation result of S ₂₁ . Curves a ₁ , b ₁ , and c ₁ in Fig. 5a respectively represent the simulation curves of the transmission characteristic S ₂₁ when the center frequencies of the low-pass band are 570MHz, 630MHz, and 690MHz and the center frequency of the high-pass band is 1.3GHz. Curves a ₂ and b ₂ , c ₂ represent the simulation curves of the transmission characteristic S ₁₁ when the center frequencies of the low-pass band are 570MHz, 630MHz, and 690MHz respectively and the center frequency of the high-pass band is 1.3GHz. Curves a ₁ , b ₁ , and c ₁ in Fig. 5b represent the simulation curves of the transmission characteristic S ₂₁ when the center frequencies of the high-pass band are 1.156GHz, 1.24GHz, and 1.336GHz respectively and the center frequency of the low-pass band is 604MHz. Curves a ₂ , b ₂ and c ₂ represent the simulation curves of the transmission characteristic S ₁₁ when the center frequencies of the high-pass band are 1.156 GHz, 1.24 GHz, and 1.336 GHz and the center frequency of the low-pass band is 604 MHz, respectively. Figure 6a and Figure 6b are the actual measurement results when the center frequencies of the low-pass band and high-pass band of the adjustable double-bandpass filter designed according to the above parameters are changed; the horizontal axis in the output characteristic curve represents frequency, and the vertical axis represents Transmission characteristics S ₂₁ , S ₁₁ ; the dotted line is the actual measurement result of S ₁₁ , and the solid line is the actual measurement result of S ₂₁ . Curves a ₁ , b ₁ , and c ₁ in Fig. 6a respectively represent the actual measurement curves of the transmission characteristic S ₂₁ when the center frequency of the low-pass band is 570MHz, 630MHz, and 690MHz and the center frequency of the high-pass band is 1.3GHz. Curves a ₂ , b ₂ and c ₂ represent the actual measurement curves of the transmission characteristic S ₁₁ when the center frequencies of the low-pass band are 570MHz, 630MHz, and 690MHz respectively and the center frequency of the high-pass band is 1.3GHz. Curves a ₁ , b ₁ , and c ₁ in Figure 6b represent the actual measurement curves of the transmission characteristic S ₂₁ when the center frequencies of the high-pass band are 1.156GHz, 1.24GHz, and 1.336GHz and the center frequency of the low-pass band is 604MHz, respectively. Curve a ₂ , b ₂ , and c ₂ represent the actual measurement curves of the transmission characteristic S ₁₁ when the center frequencies of the high-pass band are 1.156 GHz, 1.24 GHz, and 1.336 GHz and the center frequency of the low-pass band is 604 MHz, respectively. The test results are basically consistent with the simulation results, and the simulation and testing are completed using Agilent's commercial electromagnetic simulation software ADS and E5071C network analyzer respectively. It can be seen from the test results that the center frequency of the low-pass band can be adjusted in the range of 570-690MHz, while the center frequency of the high-pass band can be adjusted in the range of 1.156-1.336GHz; the transmission characteristic curve in Figure 6a is in the low-pass band The center frequencies are 570MHz, 630MHz, 690MHz and the center frequency of the high-pass band is 1.3GHz. Taking the S ₁₁ -3dB suppression level commonly used in band-pass filters as a standard, the bandwidths at -3dB are 40MHz, 52MHz, and 60MHz respectively. ; It can be seen that the bandwidth at -3dB is 50±10MHz when the low passband changes. The transmission characteristic curve in Figure 6b is measured when the center frequencies of the high-pass band are 1.156GHz, 1.24GHz, 1.336GHz and the center frequency of the low-pass band is 604MHz. The commonly used S ₁₁ -3dB suppression level of the band-pass filter is taken as Standard, the bandwidth at -3dB is 67MHz, 78MHz, and 82MHz respectively; it can be seen that the bandwidth at -3dB is 70±10MHz when the high-pass band changes. The test results show that no matter whether the low passband or the high passband is changed, the other passband is not affected, and the goal of independent tuning of the dual passbands is achieved.

The simulation and actual measurement results of the embodiment show that when the center frequency of any one of the two passbands is tuned, the transmission characteristics of the other passband in the embodiment remain basically unchanged, achieving the goal of independent tuning.

The above is only a preferred example of the utility model, and is not intended to limit the utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (7)

1. have the high selectivity dual band pass filter of independent adjustable passband, comprise upper strata microstrip structure, intermediate layer medium substrate and lower floor's grounding plate; The upper strata microstrip structure is attached to intermediate layer medium substrate upper surface, and lower floor's grounding plate is attached to intermediate layer medium substrate lower surface; It is characterized in that: the upper strata microstrip structure comprises port feed line, port microstrip line and four resonators; Four resonators all are the quarter-wave resonance devices; Four resonators are arranged into symmetrical structure; Two resonator structures that are positioned at the top are identical, and two resonator structures that are positioned at the below are identical, the port microstrip line of filter above two resonators and below two resonators between; Two resonators that are positioned at the top directly link to each other and parallel coupling with the port feed line, are positioned at two resonators and the parallel coupling of port feed line of below.

2. according to the said high selectivity dual band pass filter of claim 1 with independent adjustable passband; It is characterized in that being positioned at upper left first resonator and comprise first variable capacitance diode, coupled microstrip line part and non-coupled microstrip line part; Wherein the coupled microstrip line part is connected in sequence by the 4th microstrip line, the 5th microstrip line and the 6th microstrip line; Non-coupled microstrip line partly comprises first microstrip line, second microstrip line and the 3rd microstrip line; One end of first microstrip line links to each other with the negative pole of first variable capacitance diode; The positive pole of first variable capacitance diode links to each other with the lower floor grounded metal through the metallization via hole that passes the intermediate layer medium substrate through an electric capacity; First microstrip line, second microstrip line, the 3rd microstrip line, the 4th microstrip line, the 5th microstrip line and the 6th microstrip line are connected in order, and the metallization via hole that the 6th microstrip line end passes the intermediate layer medium substrate links to each other with the lower floor grounded metal; The 3rd resonator that is positioned at the lower left comprises the 3rd variable capacitance diode and coupled microstrip line part; Wherein the coupled microstrip line part is connected in sequence by the tenth microstrip line, the 11 microstrip line; One end of the tenth microstrip line links to each other with the negative pole of the 3rd variable capacitance diode; The positive pole of the 3rd variable capacitance diode links to each other with the lower floor grounded metal through the metallization via hole that passes the intermediate layer medium substrate through an electric capacity, and the tenth microstrip line other end links to each other with an end of the 11 microstrip line; The metallization via hole that the other end of the 11 microstrip line passes the intermediate layer medium substrate links to each other with the lower floor grounded metal.

3. according to the said high selectivity dual band pass filter with independent adjustable passband of claim 2, the electrical length L+ Δ L that it is characterized in that being positioned at upper left resonator is 1/4th of the corresponding wavelength X of the low resonant frequency f of said dual band pass filter; Wherein, L is actual microstrip line length, and Δ L is first variable capacitance diode equivalence microstrip line length of upper left first resonator; Actual microstrip line length L is the length sum of first microstrip line, second microstrip line, the 3rd microstrip line, the 4th microstrip line, the 5th microstrip line and the 6th microstrip line; Length between the coupled zone equals the 4th microstrip line, the length summation of the 5th microstrip line and the 6th microstrip line; The electrical length L '+Δ L ' that is positioned at the resonator of lower left for the corresponding wavelength X of the high resonance frequency f ' of said dual band pass filter ' 1/4th; Wherein L ' is actual microstrip line length, and Δ L ' is the 3rd variable capacitance diode equivalence microstrip line length of the resonator of lower left; Actual microstrip line length L ' be the length sum of the tenth microstrip line, the 11 microstrip line; Length between the coupled zone equals the length summation of the tenth microstrip line, the 11 microstrip line.

4. according to the said high selectivity dual band pass filter of claim 2 with independent adjustable passband; It is characterized in that the coupled microstrip line part that is positioned at upper left resonator is in turn connected into n shape structure by the 4th microstrip line, the 5th microstrip line and the 6th microstrip line, the coupled microstrip line part that is positioned at the resonator of lower left is in turn connected into L shaped structure by the tenth microstrip line, the 11 microstrip line.

5. according to the said high selectivity dual band pass filter of claim 2 with independent adjustable passband; It is characterized in that said port feed line comprises coupling feed line part and non-coupling feed line part; The feed line that wherein is coupled partly comprises two parts up and down, and top is connected and composed by the 7th microstrip line, the 8th microstrip line and the 9th microstrip line successively; The 7th microstrip line is connected with the 4th microstrip line and realizes stronger coupling between the feed line resonator; The lower part is connected and composed by the 13 microstrip line and the 14 microstrip line successively; The non-coupling feed line part of port feed line is made up of the 12 microstrip line; Be provided with the electromagnetic coupled gap that width is 0.2 ± 0.05mm between the port feed line coupling feed line part resonator coupled microstrip line part; The port microstrip line comprises the 16 microstrip line; First resonator, second resonator are positioned at the 16 microstrip line top, and the 3rd resonator, the 4th resonator are positioned at the 16 microstrip line below.

6. according to the said high selectivity dual band pass filter of claim 5 with independent adjustable passband; The top that it is characterized in that the coupling feed line of port feed line connects and composes n shape structure successively by the 7th microstrip line, the 8th microstrip line and the 9th microstrip line, is positioned at the inboard of the first resonator coupled microstrip line part n shape structure; The 7th microstrip line, the 8th microstrip line and the 9th little band are parallel with the 6th microstrip line with the 4th microstrip line, the 5th microstrip line respectively; The lower part of the coupling feed line of port feed line connects and composes L shaped structure successively by the 13 microstrip line and the 14 microstrip line, is positioned at the inboard of resonator coupled microstrip line partial L shape structure; The 13 microstrip line is parallel with the 11 microstrip line with the tenth microstrip line respectively with the 14 microstrip line.

7. the high selectivity dual band pass filter with independent adjustable passband according to claim 6 is characterized in that the length of first microstrip line is 2.6 ± 0.2mm; The length of second microstrip line is 12.4 ± 0.3mm; The length of the 3rd microstrip line is 3.0 ± 0.1mm, and the length of the 4th microstrip line is 13.6 ± 0.2mm, and the length of the 5th microstrip line is 9.1 ± 0.4mm; The length of the 6th microstrip line is 14.1 ± 0.3mm; Coupling spacing between said four resonators and the port feed line is 0.2 ± 0.05mm, and the width of first microstrip line, second microstrip line, the 3rd microstrip line, the 4th microstrip line, the 5th microstrip line and the 6th microstrip line is 0.7 ± 0.1mm, and the width of the 7th microstrip line, the 8th microstrip line and the 9th microstrip line is 0.9mm; The width of the 16 microstrip line is 1.84mm, and the characteristic impedance of the 16 microstrip line is 50 Ω; The length of the tenth microstrip line, the 11 microstrip line is respectively 10.5 ± 0.5mm and 7.0 ± 0.4mm, and the gap of the tenth microstrip line and the 13 microstrip line is 0.2 ± 0.05mm; Gap between first resonator, second resonator and the 3rd resonator, the 4th resonator is 0.4mm; The length of the 15 microstrip line is 1.8 ± 0.2mm, and the spacing between each bar microstrip line is 0.2 ± 0.05mm; The variable capacitance diode of first resonator, second resonator is provided with identical bias voltage, and the variable capacitance diode of the 3rd resonator, the 4th resonator is provided with identical bias voltage.

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