CN106099298A - Ultra broadband filter response power divider - Google Patents

Abstract

The invention discloses an ultra-wideband filter response power divider, which mainly solves the problem of too narrow bandwidth of the power divider in the prior art. It includes a microstrip dielectric substrate (1), an input port (2), two output ports (7, 8), two upper and lower broadband filters (3, 4), and the upper broadband filter (3) is composed of a high-pass filter unit ( 31), a ladder impedance transmission line (32) and a low-pass filter unit (33) are cascaded. The high-pass filter unit is composed of a main transmission line and a pair of short-circuit branches. The low-pass filter unit is composed of three sections of low-impedance transmission lines and four pairs of high-impedance branches alternately cascaded. The lower broadband filter (4) has the same structure as the upper broadband filter (3), and is arranged symmetrically, and an isolation resistor (6) is arranged between them. The invention can realize the band-pass filter response from 3GHz to 16GHz, and can be used for the radio frequency front end of the wireless communication system.

Description

Ultra Wideband Filter Response Power Divider

technical field

The invention belongs to the technical field of microwave devices, in particular to an ultra-wideband filter response power divider, which can be used for a radio frequency front end of a wireless communication system.

Background technique

With the rapid development of communication technology, people have higher and higher requirements for information transmission systems, hoping to obtain more spectrum resources to increase data transmission rates, improve system security, and reduce production costs. In this context, ultra-wideband UWB technology has become a research hotspot in the field of wireless communication because of its simple system structure, low cost, low power consumption, high security, low interference, and high data transmission rate. In the wireless communication system, the power splitter and the filter are two important microwave devices, which are often used together in the RF front-end circuit of the communication system. Since these two passive devices occupy a relatively large space in the RF front-end, It limits the miniaturization design of the wireless communication system to a great extent. The traditional method is to separately miniaturize the power splitter and filter, which can reduce the entire system to a certain extent, but the overall reduction space is relatively limited. In addition, in the miniaturization of the power splitter and filter In the optimized design, part of it is at the expense of insertion loss. In recent years, some researchers have gradually proposed a scheme to integrate the design of filters and power dividers. In one circuit structure, the functions of power dividers and filters can be realized at the same time, which can not only reduce the size of the circuit , but also to improve the loss of the system.

Ultra-wideband UWB technology was first used for military radar as the main purpose, and was lifted on February 14, 2002. The FCC of the United States Federal Communications Commission stipulated: "When the transmission power is lower than the specified value of radiation noise in the United States - 41.3dBm/MHz, that is, the power is Under the condition of 1mW/MHz, the frequency band from 3.1G to 10.6GHz can be used for imaging systems that scan underground and partition walls, automotive anti-collision radars, distance measurement and wireless data communication between home appliance terminals and portable terminals ".

In March 2008, Zhewang Ma, Wenqing He and others published "A Novel Compact Ultra-Wideband BandpassFilter Using Microstrip Stub-Loaded Dual -Mode Resonator Doublets", proposed an ultra-wideband filter, which can realize ultra-wideband of 3.3-10.4GHz, and the ultra-wideband working bandwidth only covers 3.3-10.4GHz, and cannot perform power division.

In January 2010, Kaijun Song and others published "Novel Ultra-Wideband (UWB) Multilayer Slotline Power Divider With Bandpass Response", a power divider with ultra-wideband filtering characteristics is proposed. Although this method can perform power division, the frequency band coverage can only reach 3.1GHz to 11.5GHz, which just covers the frequency range defined by ultra-wideband and cannot be further extended. , in order to achieve a wider frequency range, so that it cannot be used in the Ku band of satellite communication, and at the same time, the filtering response is slower at the edge of the passband, and the skirt is less steep.

Contents of the invention

The purpose of the present invention is to address the above-mentioned deficiencies in the prior art, and propose an ultra-wideband filter response power divider that can further extend the bandwidth, so as to extend the passband bandwidth to cover five octaves, that is, realize the frequency band from 3GHz to 16GHz , to meet the frequency band requirements of 14/12GHz satellite communication services.

In order to achieve the above object, the ultra-wideband filter response power divider of the present invention includes a microstrip dielectric substrate, an input port, two output ports, and two upper and lower symmetrical broadband filters; the two broadband filters and the input and output ports are engraved It is etched on the top of the dielectric substrate, and the bottom of the dielectric substrate is a metal grounding plate; the two ends of the upper broadband filter are respectively connected to the input port and the first output port, and the two ends of the lower broadband filter are respectively connected to the input port and the second output port. The connection is characterized in that each broadband filter is formed by cascading a high-pass filter unit, a stepped impedance transmission line, and a low-pass filter unit;

The high-pass filter unit is composed of a main transmission line and a pair of short-circuit stubs, and is used to realize a 3GHz high-pass filter response;

The low-pass filter unit adopts a string gourd type high and low impedance resonator structure, which is composed of three sections of low-impedance transmission lines and four pairs of high-impedance branches alternately cascaded to achieve a 16GHz low-pass filter response;

The high-pass filter unit and the low-pass filter unit are matched and connected through a ladder impedance transmission line, that is, the main transmission line and four pairs of high-impedance branches are respectively connected to both ends of the ladder impedance transmission line to realize the ultra-wideband filtering function.

The present invention has the following advantages:

1. The present invention realizes the ultra-wideband characteristic of the power splitter due to the adoption of a multi-stage transmission line cascade structure in the two branches of the power divider;

2. The present invention forms a high-pass filter unit by loading a pair of short-circuit stubs on the main transmission line of the power divider to realize the filter characteristics of the low-end frequency of the power divider and reduce the cut-off frequency of the low-end of the passband to 3GHz;

3. The present invention realizes the filter characteristics of the high-end frequency of the power divider by cascading the low-pass filter unit of the series gourd-type high-low impedance resonator structure before the output port of the power divider, and raises the high-end cut-off frequency of the passband to 16GHz .

Description of drawings

Fig. 1 is a three-dimensional structural diagram of the present invention;

Fig. 2 is two broadband filter structural diagrams of upper and lower symmetry among the present invention;

Fig. 3 is the enlarged structural diagram of low-pass filtering unit in the present invention;

FIG. 4 is a graph of transmission coefficients from an input port to an output port according to an embodiment of the present invention;

FIG. 5 is a graph showing the return loss of the input port and the isolation of the output port according to the embodiment of the present invention.

detailed description

Embodiments of the present invention are described in detail below in conjunction with accompanying drawings:

With reference to Fig. 1, Fig. 2 and Fig. 3, the present invention mainly consists of microstrip dielectric substrate 1, input port 2, two output ports 7,8, two broadband filters 3,4 up and down, two high-pass filter units 31, 41. Two upper and lower stepped impedance transmission lines 32, 42, two upper and lower low-pass filter units 33, 43, a metal ground plate 5, and an isolation resistor 6, wherein:

The microstrip dielectric substrate 1 adopts a double-sided copper-clad dielectric substrate with a dielectric constant of 2.45 and a plate thickness of 1mm, and a metal ground plate 5 under the double-sided copper-clad laminate;

The upper and lower high-pass filter units 31, 41 have the same structure and are placed symmetrically, that is, the upper high-pass filter unit 31 consists of a transmission line 311 with a length of L ₁ and a width of w ₁ and two transmission lines with a length of L ₄ and a width of w ₄ Composed of parallel short-circuit stubs 312, similarly, the lower high-pass filter unit 41 is composed of a transmission line 411 with a length of L ₁ ′ and a width of w ₁ ′ and two parallel short-circuit stubs 412 with a length of L ₄ ′ and a width of w ₄ ′ , where L ₁ =L ₁ '=18mm, w ₁ =w ₁ '=4mm, L ₄ =L ₄ '=3.2mm, w ₄ =w ₄ '=0.5mm, through these two high-pass filter units 31, 41 Achieve 3GHz high-pass response;

The upper and lower low-pass filter units 33, 43 are all realized by using a string gourd-type high and low impedance resonator structure, and placed symmetrically, that is, the upper and low-pass filter units 33 are respectively composed of low-impedance lines 331 and high-impedance lines 332, wherein, The low-impedance line is divided into three sections, the length of the left section and the right section are both w ₉ =2*L ₆ +w ₇ , and the width is L ₇ , the length of the middle section is w ₆ , and the width is L ₇ ; the high-impedance line It is divided into four sections, each of which is L ₅ in length and w ₅ in width. Similarly, the lower low-pass filter unit 43 is composed of a low-impedance line 431 and a high-impedance line 432, wherein the low-impedance line is divided into three sections, and the lengths of the left section and the right section are both w ₉ ′=2*L ₆ ′ +w ₇ ', the width is L ₇ ', the middle section is w ₆ ' in length, and the width is L ₇ '; the high-impedance line is divided into four sections, all of which are L ₅ ' in length and w ₅ ' in width, as shown in the figure 3 shown. Where w ₉ =w ₉ '=12.4mm, L ₇ =L ₇ '=0.4mm, w ₆ =w ₆ '=4mm; L ₅ =L ₅ '=0.4mm, w ₅ =w ₅ '=0.8mm, A low-pass response of 16 GHz can be achieved through this string gourd-type high and low impedance resonator structure.

The upper high-pass filter unit 31 and the upper low-pass filter unit 33 are matched and connected through a 50-ohm cascaded transmission line 32 to form the upper wide-band filter 3. Similarly, the lower wide-band filter 4 is also composed of these three parts, that is, the lower high-pass filter The unit 41 and the lower low-pass filtering unit 43 are matched and connected through a 50-ohm cascaded transmission line 42 , and they together form two upper and lower symmetrical wideband filters 3 and 4 . Wherein, the length of the transmission line 32 is L ₃ =8 mm, and the width is w ₃ =2.73 mm.

The isolation resistor 6 is arranged between the two upper and lower symmetrical broadband filters 3 and 4, and the size of the isolation resistor 6 determines the isolation characteristics of the power divider. In this example, there are seven resistors with the same resistance value, namely:

R ₁ =R ₂ =R ₃ =R ₄ =R ₅ =R ₆ =R ₇ =200Ω.

Effect of the present invention can be further illustrated by following simulation:

Simulation 1 simulates the transmission characteristics of the ultra-wideband filter response power divider of the present invention, and the result is shown in Fig. 4, wherein, S ₂₁ (dB) curve represents the transmission characteristics between the input port 2 and the first output port 7; S ₃₁ ( dB) curve represents the transfer characteristic between the input port 2 and the second output port 8 .

It can be seen from Fig. 4 that the ultra-wideband filter response power divider realizes the filter power division response in the 3-16GHz frequency band, and the distribution and insertion loss are less than 4.5dB.

Simulation 2, the reflection characteristics and isolation characteristics of the ultra-wideband filter response power splitter of the present invention are simulated, the result is by Fig. 5, wherein S ₁₁ (dB) curve represents the reflection characteristics of input port 2, and S ₂₃ (dB) represents the output port The isolation characteristic curve between 7 and output port 8.

It can be seen from FIG. 5 that the maximum value of the reflection characteristic curve S ₁₁ of the ultra-wideband filter of the present invention is less than -8dB, and the isolation S ₂₃ between output ports is greater than 10dB.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (7)

1. An ultra-broadband filter response power divider, comprising a microstrip dielectric substrate (1), an input port (2), two output ports (7, 8), two broadband filters (3, 4) up and down; the Two broadband filters and input and output ports are etched on the top of the dielectric substrate (1), and the metal ground plate (5) is below the dielectric substrate (1); the two ends of the upper broadband filter (3) are respectively connected to the input port ( 2) be connected with the first output port (7), the two ends of the lower broadband filter (4) are connected with the input port (2) and the second output port (8) respectively, it is characterized in that, The upper broadband filter (3) is formed by cascading a high-pass filter unit (31), a ladder impedance transmission line (32), and a low-pass filter unit (33); The high-pass filter unit (31) is composed of a main transmission line (311) and a pair of short-circuit stubs (312), and is used to realize a 3GHz high-pass filter response; The low-pass filter unit (33) adopts a gourd-type high and low impedance resonator structure in series, and is composed of three sections of low-impedance transmission lines (331) and four pairs of high-impedance branches (332) alternately cascaded to realize 16GHz low-pass filtering response; The high-pass filter unit (33) and the low-pass filter unit (31) are matched and connected through a ladder impedance transmission line (32), that is, the main transmission line (311) and four pairs of high-impedance branches (332) are respectively connected to two ends of the ladder impedance transmission line (32). end, to achieve ultra-wideband filtering function; The lower broadband filter (4) has the same structure as the upper broadband filter (3), and is placed symmetrically. 2. The ultra-wideband filter response power divider according to claim 1, characterized in that, the upper broadband filter (3) and the lower broadband filter (4) are respectively located at the first output port (7) and the second output port (8), the middle of the main transmission line in the upper broadband filter (3) and the symmetrical main transmission line of the lower broadband filter (4) are loaded with seven identical isolation resistors (6) for the first output port (7) and the first output port (7) and The second output port (8) is isolated to realize ultra-wideband power distribution. 3. ultra wideband filter response power distributor according to claim 1, is characterized in that, the characteristic impedance of main transmission line (311) is less than 50 ohms on the high-pass filtering unit, and length L ₁ satisfies _λgL /4＜L ₁ ＜λ _gL , where λ _gL represents an intermediate variable, f _cL is the cut-off frequency of the high-pass filter, c is the speed of light in vacuum, and ε _e is the effective dielectric constant of the microstrip plate. 4. ultra-broadband filter response power divider according to claim 1, it is characterized in that the length L4=λ _g L/4 of a pair of short-circuit stubs (312) forms, and the spacing between two stubs satisfies L ₈ =λ _gL /2, where λ _g L represents an intermediate variable, f _cL is the cut-off frequency of the high-pass filter, c is the speed of light in vacuum, and ε _e is the effective dielectric constant of the microstrip plate. 5. ultra-broadband filter response power divider according to claim 1, is characterized in that, low-impedance line (331) characteristic impedance is less than 50 ohms, length L ₇ ＜ _λgH /4, wherein _λgH represents intermediate variable, f _cH is the cut-off frequency of the low-pass filter, c is the speed of light in vacuum, and ε _e is the effective dielectric constant of the microstrip plate. 6. ultra-broadband filter response power divider according to claim 1, is characterized in that, high-impedance line (332) characteristic impedance is greater than 50 ohms, length L ₅ ＜ _λgH /4, wherein _λgH represents intermediate variable, f _cH is the cut-off frequency of the low-pass filter, c is the speed of light in vacuum, and ε _e is the effective dielectric constant of the microstrip plate. 7. The ultra-broadband filter response power divider according to claim 1, characterized in that the microstrip dielectric substrate (1) adopts a dielectric constant of 2.45, a double-sided copper-clad laminate with a thickness of 1mm, and metal etching on it The surface acts as a microstrip line surface, and the metal surface below acts as a ground plane (5).