CN106936403A - A kind of ultra wide band amplitude equalizer based on defect ground structure - Google Patents

Abstract

The invention discloses an ultra-wideband amplitude equalizer based on a defective ground structure. From signal input to output, an input port, an input matching circuit, a main transmission line, an output matching circuit, and an output port are arranged in sequence, and the metal formation under the dielectric substrate is set to load The DGS of the resistor, the amplitude equalizer of the present invention has the characteristics of ultra-wideband, small size, simple structure, easy to manufacture and mass production, and is worthy of promotion in the industry.

Description

A UWB Amplitude Equalizer Based on Defective Ground Structure

technical field

The invention belongs to the technical field of microwave and millimeter wave integration, and in particular relates to an ultra-wideband amplitude equalizer based on a defect ground structure.

Background technique

The equalizer is mainly used in modern radar electronic warfare. It is connected to the input or output of the high-power traveling wave tube and plays the role of gain equalization (amplitude equalizer) or phase equalization (phase equalizer). The key is how to selectively absorb excess microwave energy without reflecting energy back to the input port. For an amplitude equalizer that uses a resonant structure to absorb energy, the former needs to be correctly set up with the resonant structure and absorbing material, and the latter needs to have a good input-output match in the entire frequency band.

Specifications for amplitude equalizers. 1. The transmission characteristic curve of the amplitude equalizer should be exactly complementary to the transmission characteristic curve of the traveling wave tube amplifier, so a higher equalization accuracy is required; 2. The transmission characteristic curve of the system is roughly parabolic, so it is required that the structure of the standard amplitude weighing instrument has an inverted Bell-shaped transmission characteristic curve; 3. The fluctuation in the system gain band is large, so the equalization amount (S(2,1)) may be less than -10dB at some frequency points; 4. In order to avoid energy reflection, standing wave ratio (VSWR) is required Smaller; 5. If the pass-band bandwidth of the system requires the amplitude equalizer to have broadband characteristics; 6. In addition, as the equipment space becomes increasingly crowded, solid-state devices are required to have small size, light weight, good reliability, and convenience Integration and other features.

The current implementation of the amplitude equalizer. It can be roughly divided into two types: 1. Use an isolator without loss equalization network, so that the energy reflected by the equalizer is exported through the isolator; 2. Use a lossy balance network, which is composed of a resonator that can absorb energy, a matching circuit, and a main transmission line . The resonator selects the frequency, the resistor or absorber absorbs the energy, and the matching circuit adjusts the standing wave ratio. It is easy to make the VSWR of the amplitude equalizer of the isolator-free equalization network very small, but it is necessary to design an isolator, which is large in size and is not conducive to circuit integration. It is difficult to implement a broadband isolator; the amplitude equalization of the lossy equalization network is used Devices are widely used in the field of microwave and millimeter waves, with various forms, including a) lumped parameter type, b) waveguide type and coaxial type (stereo circuit), c) integrated transmission line type (planar circuit).

a) Lumped parameter type amplitude equalizer, the components are limited by parasitic parameters, so it is not suitable for use in high frequency bands;

b) Stereo circuit amplitude equalizer, the main transmission line can be waveguide or coaxial, and the resonator can be waveguide or coaxial resonant cavity. The energy on the main transmission line enters the resonant cavity through hole coupling or probe coupling, and there is a wave-absorbing material in the cavity to absorb energy. This type of amplitude equalizer has a large adjustable attenuation range, a high degree of freedom of adjustment, and a large power capacity, but it is large in size, complex in structure, poor in mechanical stability, and difficult to design and process;

c) Planar circuit amplitude equalizer, the main transmission line can be an integrated transmission line such as microstrip line, strip line, coplanar waveguide, etc., the resonator is composed of open or short-circuit resonant branches, and the energy-absorbing resistance is loaded in the resonant branches, or The gap between the resonant stub and the main transmission line. The resonant stub length of this type of amplitude equalizer is inversely proportional to the operating frequency, and the equalization amount of a single resonant stub is small.

In summary, the resonator of the amplitude equalizer of the lossy equalization network is loaded on the bypass, and the energy on the main transmission line is coupled to the resonator for absorption, and the amount of coupling depends largely on the coupling structure. The three-dimensional circuit is bulky, complex in structure, and inconvenient to debug; while the length of the resonant branch of the planar circuit is proportional to the wavelength, and the low-end size of the microwave frequency is large; the bandwidth of a single resonant branch is narrow, and the energy absorbed by the resistance is limited.

Defected Ground Structure (DGS, Defected Ground Structure) is to etch a pattern on the metal ground plate of the microstrip line to disturb the current distribution on the ground plate, thereby changing the distributed inductance and distributed capacitance of the microstrip line, showing a slow wave effect and Wide stopband characteristics. Microwave devices using DGS can obtain miniaturization and high performance that cannot be achieved by conventional technologies. Power splitters, couplers, amplifiers.

The invention is one of the level equalizers of the lossy equalization network planar circuit, which uses the band-stop characteristic of the DGS to replace the traditional resonator, and directly loads the resistance on the DGS to absorb excess energy. The equivalent circuit of this structure is also different from the traditional structure, and it is small in size and has good broadband characteristics.

Prior Art Similar to the Invention and Disadvantages

The stub resonant microstrip amplitude equalizer is the most commonly used planar circuit amplitude equalizer. By changing the size, shape, number, open or short circuit characteristics of the resonant stubs, and the matching circuit of the main transmission line, various structures can be evolved. The resonator of this structure is next to the microstrip line and consists of resonant stubs. Recently, there are also a few reports in the literature that the additional introduction of DGS into the traditional planar circuit amplitude equalizer can change the characteristic impedance of the main transmission line, thereby significantly improving the equalization amount and bandwidth, such as introducing dumbbell-shaped or "C"-shaped DGS in the metal ground layer . This structure is still a full-featured amplitude equalizer after the DGS is removed, and the additional DGS is introduced to improve the characteristics of the original amplitude equalizer. This method essentially constitutes a resonator by loading the resonant branches next to the microstrip line, and the resonator is connected in parallel with the main transmission line.

Disadvantage 1: The wavelength of the traditional planar circuit amplitude equalizer is proportional to the size of the resonant stub, and the resonant stub at the low end of the microwave frequency is longer, and the folding of the resonant stub may cause energy coupling due to the short distance;

Disadvantage 2: The single resonator of the traditional planar circuit amplitude equalizer absorbs less energy and has a narrow working bandwidth;

Disadvantage 3: If the traditional planar circuit amplitude equalizer is used to load the DGS, the DGS and the original resonator exist at the same time, the field distribution is relatively complicated, it is difficult to analyze theoretically, and it is difficult to debug.

Contents of the invention

The present invention adopts following technical scheme:

A kind of ultra-wideband amplitude equalizer based on defective ground structure, it is characterized in that comprising the DGS of dielectric substrate (8), input-output port, input-output matching circuit, main transmission line (5) and loading resistance; Described input-output port comprises Input port (1), output port (7); described input and output matching circuit is positioned at the signal layer of dielectric substrate (8), comprises input matching circuit (2), output matching circuit (6); described main transmission line (5 ) is connected to the input port (1) through the input matching circuit (2), and the other end of one end of the main transmission line (5) is connected to the output port (7) through the output matching circuit (6); the DGS of the loading resistor is located at The metal formation under the dielectric substrate (8) of the amplitude equalizer, the loaded resistance is located on the DGS.

The DGS of the loading resistor can be one or more "I" type, "C" type, "H" type, "E" type, "L" type, dumbbell type, spiral inductance type DGS of one or more loading resistors, and the DGS is located at The number of metal formations is not less than 1, and the size of the same DGS can be different.

The DGS of the load resistance includes "I" type DGS one (3), the resistance R' (10) placed on the "I" type DGS one (3), "I" type DGS two (4), placed on the " The resistance R (9) on the I" type DGS 2 (4), the number, length and width of the "I" type DGS, the inner edge distance, and the resistance value must be determined by the given operating frequency and performance requirements, and can be changed.

The working band range of this amplitude equalizer is 12-40GHz, the maximum equalization amount reaches 15dB, the return loss is better than 16dB, and VSWR<1.35.

The input and output matching circuits can share one circuit.

Problem to be solved by the present invention:

1. The traditional planar amplitude equalizer adopts the energy coupling mechanism, resulting in a small amount of equalization and a narrow operating frequency band of a single resonator;

2. The planar amplitude equalizer is additionally loaded with DGS, because the DGS and the original resonator have impedance mutations at the same time, resulting in complex structure and difficult debugging.

Main innovation points of the present invention:

DGS is set on the metal formation of the microstrip transmission line, which replaces the function of the traditional resonator by using its own wide stopband characteristics, expands the bandwidth, and has a simple structure and small size; the resistance is directly loaded on the DGS, which is equivalent to a resistance It is directly connected in series with the main transmission line, which improves the equalization amount.

Beneficial effects of the present invention:

The invention has simple structure and wide frequency band. From the complete technical scheme and structure introduced later (see attached figure), it can be seen that this invention has the characteristics of simple structure, small size, easy debugging and processing, and the structure can be as simple as consisting of a main transmission line and two gaps of loading resistors. It is 8×8mm ² . In the field of military applications where design, development, production, and testing costs are extremely high, the characteristics of simple structure, easy processing, and easy debugging can significantly reduce costs and shorten production cycles; small volume can provide more usable space for crowded electronic equipment . The excellent performance is mainly reflected in the ultra-wideband characteristics. The embodiment shows that this type of amplitude equalizer already has a 4-octave bandwidth, which realizes full coverage of the Ku, K, and Ka bands, and can work by adjusting the design size and adopting multi-stage DGS In a wider frequency band (of course, the frequency bandwidth can also be reduced to a certain extent). The design of resonators with ultra-wideband characteristics is usually a difficult point, and wideband amplitude equalizers are indispensable in the field of ultra-wideband radar and communication. This type of amplitude equalizer provides a simple and feasible method for the design of ultra-wideband amplitude equalizers , so it is worthy of large-scale production and promotion in the industry.

High Frequency Structure Simulator (HFSS, High Frequency Structure Simulator) confirms to the full-wave simulation of three-dimensional model, and the amplitude equalizer of a specific embodiment of the present invention can work in Ku, K, Ka wave band (12-40GHz), is inverted clock Type transmission characteristic curve, the maximum equalization amount reaches 15dB, the return loss is better than 16dB, VSWR<1.35, and has achieved good characteristics in the 4-octave frequency bandwidth, with an area of 8×8mm ² . The working center frequency and bandwidth can be changed by changing the design parameters and increasing the number of DGS. The size of the DGS mainly determines the center frequency, the resistance mainly determines the equalization amount, and the VSWR is related to many parameters. It can be significantly improved by choosing a matching structure.

For problem 1, this solution introduces DGS into the microstrip line amplitude equalizer, because the introduction of DGS can effectively reduce the device volume. DGS itself has a very wide working bandwidth, and if multi-level DGS is used, the bandwidth can be expanded;

Aiming at problem 2, this scheme designs the resistance that absorbs the radio frequency energy on the DGS. DGS has a wide stopband characteristic, so it can replace the traditional resonator, and it does not need to design a resonance branch in the signal layer at the same time. It has a simple structure and is easy to debug.

Therefore, the present invention is mainly composed of a main transmission line, an input and output port, an input and output matching circuit, and a DGS that loads a resistor, as shown in FIG. 1 . The whole circuit is designed as a planar circuit using a microstrip line. The microwave signal enters from the 50-ohm standard microstrip line input port, and is transmitted on the main transmission line after impedance transformation by the input matching circuit. The line width of the main transmission line depends on the power capacity and other technical indicators. Need to be sure. The metal ground part under the main transmission line is hollowed out (that is, DGS), which leads to changes in the distributed capacitance and inductance of the main transmission line. This structure can replace the role of the planar microstrip resonant stub, and has frequency selection characteristics and broadband characteristics. A resistor is loaded on the DGS, because the DGS destroys the current of the main transmission line on the metal ground. This structure is equivalent to a resistor directly connected in series with the main transmission line. When the resistance is located at the position with the largest surface current, it can obviously absorb microwave energy. When the energy is transmitted here, the signals of different frequencies are absorbed by the resistance differently, forming an inverted bell-shaped transmission characteristic curve. Then the microwave signal is transformed by the output matching circuit, and then output through the 50-ohm standard microstrip line output port. The input matching circuit and the output matching circuit can effectively improve the standing wave ratio. In the process of continuous simulation and debugging, it is found that the standing wave ratio can be improved in a wide frequency range by adjusting the size of the DGS and the resistance, and increasing the line width of the main microstrip transmission line can weaken the effect of increasing the characteristic impedance caused by the introduction of the DGS structure. This method It can solve the problem of broadband matching, so the input and output matching circuits are not necessary.

Preferably, the planar amplitude equalizer is implemented using a microstrip transmission line, which has a simple structure and is easy to process;

Preferably, the dielectric substrate of the planar amplitude equalizer adopts a single _- layer _Al2O3Al2O3 ceramic substrate, which has a relatively large dielectric constant and can reduce the volume of the device;

Preferably, the input and output ports adopt a 50-ohm standard microstrip line, which is convenient for connection with other devices;

Preferably, the DGS adopts "I" type DGS, and contains two stages of "I" type DGS, located under the main transmission line. Each "I" type DGS is equal in size, and the main transmission line divides it into two symmetrical parts. Each "I" type DGS has a wide stop band characteristic, and it is easy to debug, and the two-stage "I" type DGS can expand the bandwidth;

Preferably, the resistors are TaN film resistors, which are loaded in the middle of the "I" type DGS (right below the main transmission line), and the sizes of the two resistors are set according to the simulation requirements. The size of the resistor affects the standing wave ratio and the equalization amount, and the larger the resistance value, the greater the equalization amount.

Description of drawings

Fig. 1 is a three-dimensional structure diagram of an ultra-wideband amplitude equalizer based on a defect ground structure in the present invention;

Fig. 2 is a sectional view of an ultra-wideband amplitude equalizer based on a defect ground structure along the direction A-A' in Fig. 1 according to the present invention;

Fig. 3 is the schematic diagram of the plane where the main transmission line is located in the present invention;

Fig. 4 is the schematic diagram of the plane where the DGS of the load resistance is located in the present invention;

Fig. 5 is the HFSS simulation result of S parameter of a specific embodiment in the present invention;

Fig. 6 is the HFSS simulation result of the input standing wave ratio of a specific embodiment of the present invention.

Description of reference signs: 1. Input port; 2. Input matching circuit; 3. "I" type DGS 1; 4. "I" type DGS 2; 5. Main transmission line; 6. Output matching circuit; 7. Output port; 8. Dielectric substrate; 9. Resistance R; 10. Resistance R'.

detailed description

Below in conjunction with accompanying drawing, the present invention will be further described:

As shown in Figures 1-4, the UWB amplitude equalizer based on the defective ground structure of the present invention includes a main transmission line 5, an input and output port, an input and output matching circuit, and a DGS loading resistor. The main transmission line 5 is a microstrip transmission line located on the dielectric substrate 8 . The input and output ports include input port 1 and output port 7, which are respectively located at the input end and output end of the device. The input and output matching circuit (non-essential structure) includes an input matching circuit 2 and an output matching circuit 6. The input matching circuit 2 is located between the input port 1 and the main transmission line 5 to improve the input standing wave ratio; the output matching circuit 6 is located on the main transmission line Between 5 and output port 7, it is used to improve the output VSWR. The DGS loaded with resistors includes "I" type DGS-3, resistor R'10, "I" type DGS24, and resistor R9, located directly below the main transmission line 5 and under the dielectric substrate 8. "I" type DGS-3 and "I" type DGS-24 are long and narrow gaps dug on the microstrip line metal formation, and resistor R'10 and resistor R9 are respectively connected to "I" type DGS-3 and "I" "Type DGS II 4 on.

A kind of UWB amplitude equalizer based on defect ground structure of the present invention will be described in detail below with a specific embodiment, to further demonstrate the advantages of the present invention: In the present embodiment, the whole structure transmission line adopts microstrip line, and the dielectric substrate A single-layer Al2O3Al ₂ O ₃ ceramic substrate is used with a thickness of h=0.254mm. The width w0 of the microstrip line at the input port 1 and the output port 7 is w0=0.25mm, the line width w0=0.65mm of the main transmission line 5 in the middle, and the length l0=1mm. The DGS employs a two-stage "I" type DGS located in a metallic formation. "I" type DGS-3 and "I" type defect structure 24 are the same in size, and are symmetrical about the two symmetrical axes of the rectangular dielectric substrate, the gap length l1=3.4mm, width w1=0.24mm, the distance between the inner edges of the two d = 0.85 mm. Resistor R'10 and resistor R9 are respectively connected between the gaps of "I" type DGS-3 and "I" type DGS-24 with ceramic resistors, the connection direction is consistent with the signal transmission direction on the main transmission line 5, and the resistance values are respectively R'=50 ohms, R=200 ohms. Based on this structure and size, the VSWR is already very good, so the input matching circuit 2 and output matching circuit 6 are not designed in the signal layer. Figures 5-6 show the HFSS three-dimensional full-wave simulation results of this embodiment, and it can be seen that the standing wave ratio, return loss, and equalization are all very good.

It is worth noting that: the line width of the main transmission line 5 is set wider than the 50 ohm line, which can effectively improve the standing wave ratio; the input matching circuit 2 and the output matching circuit 6 have various forms, and the matching method of the microwave/radio frequency circuit can be used. It does not have to be designed on the signal layer, and the input and output matching circuits can also be omitted when the VSWR is good; the DGS that loads the resistor is located on the metal ground layer, and there are many types of DGS, such as "I" type, "C" type, Dumbbell type, spiral inductance type, "H" type, "E" type, "L" type, etc. can be used in combination, and multi-stage DGS can also be used. The resistance value and placement position vary with DGS, and the performance of the amplitude equalizer should be optimized under the premise of satisfying processing and installation.

The working process of the UWB amplitude equalizer based on the defective ground structure of the present invention is as follows: the microwave signal is fed from the input port 1, and then transmitted on the main transmission line 5 after the impedance transformation is performed by the input matching circuit 2. The DGS under the main transmission line (that is, the "I" type DGS-3 and the "I" type DGS-24 in the embodiment) changes the distributed capacitance and inductance of the main transmission line, replaces the role of the planar microstrip resonant stub, and has frequency selection characteristics and broadband characteristics. Connect resistor R'10 and resistor R9 between the gaps of "I" type DGS-3 and "I" type DGS-24, respectively, because DGS changes the current of the main transmission line 5 on the metal ground, and the resistance is equivalent to being directly connected in series On the main transmission line 5, the equalization amount in the entire frequency band increases with the increase of the resistance value, which is just opposite to the traditional planar amplitude equalizer. According to the simulation results, the placement of the resistor R'10 and the resistor R9 corresponds to the voltage wave node of the 25GHz signal. The surface current of the signal at this frequency is the largest, and the corresponding equalization amount is the largest. As the signal frequency gradually moves away from the resonance center, the absorbed energy is also sequentially weakened. Because of the wide stopband characteristic of DGS, it can form an inverted bell-shaped transmission characteristic curve in a wide frequency band. The microwave signal is output through the output port 7 after impedance transformation by the output matching circuit 6 .

The present invention provides an ultra-wideband amplitude equalizer based on a defective ground structure. DGS is made on the metal formation under the main transmission line of the microstrip, and the resistance is directly loaded on the DGS, which plays the role of the resonator in the original amplitude equalizer. It has the characteristics of ultra-wideband and simple structure. The simulation of the 3D model by HFSS has confirmed that the structure can work in 12-40GHz, the working bandwidth spans the Ku, K, and Ka bands, the maximum equalization value is better than 15dB, the return loss is better than 16dB, and the input standing wave ratio is less than 1.35. It is 8×8mm ² . Compared with the existing planar amplitude equalizer, the invention expands the bandwidth, reduces the size and has a simple structure, and provides a new method for the design of the broadband miniaturized amplitude equalizer. The structure of the invention is easy to manufacture and mass-produce, and is worthy of popularization in the industry.

It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (5)

1. a kind of ultra wide band amplitude equalizer based on defect ground structure, it is characterised in that including dielectric substrate (8), input and output The DGS of port, input and output matching circuit, main transmission line (5) and loading resistor；The input/output port includes input port (1), output port (7)；The input and output matching circuit is located at the signals layer of dielectric substrate (8), including input matching circuit (2), output matching circuit (6)；One end of the main transmission line (5) is connected by input matching circuit (2) with input port (1) Connect, the other end of main transmission line (5) is connected by output matching circuit (6) with output port (7)；The DGS of the loading resistor Metal ground layer under the dielectric substrate (8) of the amplitude equalizer, the resistance for being loaded is connected under DGS.

2. a kind of ultra wide band amplitude equalizer based on defect ground structure according to claim 1, it is characterised in that it is described plus The DGS for carrying resistance can be one or more loading resistor " I " type, " C " type, " H " type, " E " type, " L " type, dumbbell shape, spiral shells Rotation inductive type DGS, DGS are located at metal ground layer, and number is no less than 1, and DGS sizes of the same race can be with difference.

3. a kind of ultra wide band amplitude equalizer based on defect ground structure according to claim 1 or claim 2, it is characterised in that institute Stating the DGS of loading resistor includes " I " type DGS mono- (3), resistance R ' (10), " I " the type DGS bis- being placed on " I " type DGS mono- (3) (4), it is placed on the resistance R (9) on " I " type DGS bis- (4), " I " type DGS numbers length and width, inside edge distance, resistance value need to be by Given working frequency and performance requirement determine, can change.

4. a kind of ultra wide band amplitude equalizer based on defect ground structure according to claim 1, it is characterised in that the amplitude The service band scope of balanced device is 12-40GHz, and maximum equilibrium quantity reaches 15dB, and return loss is better than 16dB, VSWR<1.35.

5. a kind of ultra wide band amplitude equalizer based on defect ground structure according to claim 1, it is characterised in that input is defeated Going out match circuit can share a circuit.