CN101320826A - Integrated micro-strip antenna filter coupling structure - Google Patents

Abstract

This invention is related to a micro-strip antenna, especially a coupling structure of a micro-strip antenna radiation unit and a filter. This invention discloses an integral coupling structure of micro-strip antenna filter, which is able to achieve a ruled transmission line length in a limited space without specially matching the network to process the coupling connection of the antenna and the filer. The technical proposal of this invention is that the integral coupling structure of micro-strip antenna filter includes a radiation unit, a filer and a feeder line adhered at a medium substrate; said radiation unit is connected with the filer through the feeder line; said feeder line is a curve line. This invention is applied to the micro-strip antenna system and the direct coupling of the radiation unit and the filer without specially couple to match the network; adopting the meandering micro-strip feeder line is able to achieve the needed feeder line length and the design parameter in the limited space and reduce the system volume. This invention has advantages of compact structure and low loss of insertion.

Description

Integrated micro-strip antenna filter coupling structure

Technical field

The present invention relates to microstrip antenna, particularly the coupled structure of microstrip antenna radiating element and filter.

Background technology

The design of modern microwave system is subjected to restrictions such as performance, weight, size and cost of manufacture, and at the single circuit in the system concrete index and requirement is arranged all.In the traditional circuit design process, for two different electronic circuits, as have the radiating element (antenna) and a filter of the microstrip antenna of filter, by the identical input and output impedance (50 Ω or 75 Ω) of input/output terminal regulation at two electronic circuits, realize impedance matching, two electronic circuits connect the most at last.If the input/output port of antenna and filter can not be realized good impedance matching, input/output port will produce bigger insertion loss, thereby influence the performance of system.In order to reach the impedance matching of input/output port, between two electronic circuits, add matching network usually.But this has increased the complexity that whole system designs, and has increased weight, volume and the overall losses of system simultaneously.Simultaneously, with the separately design of two electronic circuits, connect then, this has also ignored the coupled problem between two circuit.On the other hand, the feeder line that antenna is connected with filter, be referred to as transmission line at the microwave technology neighborhood, sometimes need to consider its path-length, as reach 1/4 of operating frequency of antenna wavelength, for the microwave below the 10GHz frequency, only the length of transmission line will be greater than 7.5mm, and this is unfavorable for the miniaturization of system.

Summary of the invention

Technical problem to be solved by this invention just provides a kind of integrated micro-strip antenna filter coupling structure, does not need special matching network to carry out being of coupled connections of antenna and filter, and can reach the length of transmission line of regulation in the confined space.

The present invention solve the technical problem, the technical scheme that adopts is that integrated micro-strip antenna filter coupling structure comprises attached to the radiating element on the dielectric substrate, filter and feeder line, described radiating element is connected with filter by feeder line, and described feeder line is a meander line.

The invention has the beneficial effects as follows that radiating element and filter directly are coupled by microstrip feed line in the microstrip antenna, do not need special coupling matching network; The co-design of radiating element and filter meets the design concept of microwave system more; Adopt tortuous circuitous microstrip feed line can reach feeder line length and the design parameter that needs, can reduce system bulk, have compact conformation, insert the low characteristics of loss in limited space.

Description of drawings

Fig. 1 is a prior art microstrip antenna schematic diagram;

Fig. 2 is the upward view of Fig. 1;

Fig. 3 is the rearview of Fig. 1;

Fig. 4 is the schematic diagram of embodiment 1;

Fig. 5 is the antenna system S11 curve chart of embodiment 1;

Fig. 6 is the S11 and the S21 curve chart of rectangular coil line;

Fig. 7 is the schematic diagram of embodiment 2

Fig. 8 is round screw thread line S11 and S21 curve chart;

Fig. 9 is the schematic diagram of embodiment 3 feeder lines;

Figure 10 is the S11 and the S21 comparison diagram of embodiment 3 and prior art;

Figure 11 is the schematic diagram of embodiment 4 feeder lines;

Figure 12 is S11 and the S21 curve chart of embodiment 4.

Embodiment

The present invention does not require that at antenna and filter junction antenna and filter satisfy 50 Ω or 75 Ω impedance matchings, adjust the transmission range of radiating element by optimized Algorithm to filter, cooperate the width of adjusting the interior feed line of this distance, make the junction reflection minimum, the present invention has solved the coupled problem between antenna and the filter simultaneously.The feeder line of antenna and filter adopts zigzag Microstrip line and/or snail microstrip line, can adjust its length in the communication system confined space easily, uses microstrip antenna system both can satisfy the design parameter requirement, the space that can also the minimizing system occupies.

Technical scheme of the present invention is, integrated micro-strip antenna filter coupling structure comprises that attached to the radiating element on the dielectric substrate, filter and feeder line, described radiating element is connected with filter by feeder line, and described feeder line is a meander line;

Further, described meander line is equidistant meander line;

Or described meander line is a spacing gradual change meander line;

Further, described meander line is the snail line;

Concrete, described snail line is the rectangular coil line;

Or described snail line is the round screw thread line;

Especially, described meander line is λ/4 transmission lines, and described λ is the wavelength of microstrip antenna centre frequency correspondence;

Further, the described dielectric substrate back side and filter and feeder line corresponding position are coated with ground plane.

Fig. 1, Fig. 2, Fig. 3 show the microstrip antenna schematic diagram of prior art.Microstrip antenna comprises dielectric substrate 42 among the figure, and what this dielectric substrate 42 adopted is FR4 type dielectric material, and relative dielectric constant is about 4.32." ten " font sheet metal (or coat that the one side of dielectric substrate 42 is adhered to, be radiating element 41 down together), radiating element 41 is the microstrip feed line (transmission line) of t by length for W2 thickness for the L3 width, be connected with 1/4 wavelength coupling edge 45 of loop filter 40, another 1/4 wavelength coupling edge 45 of loop filter 40 is that other circuit of microstrip feed line 46 and microwave system of W1 are connected by width.The ring frame that sheet metal constitutes among Fig. 1 is a resonator 44.As can be seen, the sheet metal ground plane 43 that dielectric substrate 42 another sides adhere to exists only in the back side of microstrip feed line and filter from Fig. 2 and Fig. 3, and the radiating element back side does not have ground plane.The relevant structural parameters of above-mentioned filter 40 see also Mohd Khairul Mohd Salleh, Ga? tan Prigent, the exercise question that Olivier Pigaglio and RaymondCrampagne deliver on " IEEE Transactions on Microwave Theory and Techniques " is the article of " Quarter-Wavelength Side-Coupled Ring Resonator for Bandpass Filters ".

Below microstrip transmission line is carried out theory analysis.

Suppose that micro belt line width is w, the dielectric substrate dielectric constant is ε, and thickness is t, and there is metal ground plate at the microstrip line back side.Owing to be present in air and the medium, so what transmit in the microstrip line is accurate TEM ripple.The microstrip line transmission characteristic can be passed through effective dielectric constant ε _ReWith characteristic impedance Z _cDescribe.

${\mathrm{\ϵ}}_{\mathrm{re}}=\frac{C_d}{C_a}---\left(1\right)$

$Z_c=\frac{1}{c\sqrt{C_a{C}_d}}---\left(2\right)$

C wherein _dCapacitance per unit length when existing for dielectric layer, C _aBe that dielectric layer is air capacitance per unit length when replacing, c is the light velocity.Hammerstad and Jensen (" Accurate models for microstrip computer-aideddesign, " IEEE MTT-S, 1980, Digest pp.407-409.) provides expression formula comparatively accurately:

${\mathrm{\ϵ}}_{\mathrm{re}}=\frac{{\mathrm{\ϵ}}_r+1}{2}+\frac{{\mathrm{\ϵ}}_r-1}{2}{(1+\frac{10}{u})}^{-\mathrm{ab}}---\left(3\right)$

U=W/t wherein,

$a=1+\frac{1}{49}\ln \left(\frac{u^4+{\left(\frac{u}{52}\right)}^2}{u^4+0.432}\right)+\frac{1}{18.7}\ln \[1+{\left(\frac{u}{18.1}\right)}^3\],$

$b=0.564{\left(\frac{{\mathrm{\ϵ}}_r-0.9}{{\mathrm{\ϵ}}_r+3}\right)}^{0.053},$

Work as ε _r≤ 128,0.01≤u≤100 o'clock, precision is higher than 0.2%.

$Z_c=\frac{\mathrm{\η}}{2\mathrm{\π}\sqrt{{\mathrm{\ϵ}}_{\mathrm{re}}}}\ln \[\frac{F}{u}+\sqrt{{1+\left(\frac{2}{u}\right)}^2}\]---\left(4\right)$

U=W/t wherein, η=120 π ohms,

$F=6+(2\mathrm{\π}-6)\exp \[-{\left(\frac{30.666}{u}\right)}^{0.7528}\],$

When u≤1,

Precision is better than 0.01%,

When u≤1000,

Be better than 0.03%.

When width, length, the thickness of straight line microstrip line is respectively w, l, t, the inductance value that this lead had is

$L\left(\mathrm{nH}\right)=2\×{10}^{-4}l\[\ln \left(\frac{l}{w+t}\right)+1.193+0.2235\frac{w+t}{l}\].K_g---\left(5\right)$

K _gFor considering the modifying factor of metal ground plate influence, when the floor was close, this value diminished, and inductance value diminishes simultaneously.

The spiral type microstrip line can equivalence be an inductance, the spiral type microstrip line can be divided into n part, and for the rectangular coil line, every part is a straight line, and for round screw thread, every part is being seen a circle.

For the round screw thread line, the mutual inductance between i unit and j the circular cell is found the solution with following Neumann formula:

Be specially:

$M_{\mathrm{ij}}=\mathrm{\μ}\sqrt{\mathrm{ab}}\[(\frac{2}{k_{\mathrm{ij}}}-k_{\mathrm{ij}})K\left(k_{\mathrm{ij}}\right)-\frac{2}{k_{\mathrm{ij}}}E\left(k_{\mathrm{ij}}\right)\]---\left(7\right)$

Wherein

k _ij＝4ab/(a+b) ²，a＝r _i+(i-0.5)(w+s)，b＝r _i(j-0.5)(w+s)，

r _iBe the internal diameter of circular inductor, s is the well width (spacing) between every circle, and w is that microstrip line is wide.

For rectangular coil, two wide w of microstrip line, length is l, thickness is the mutual inductance between zero the elementary cell

$M=\frac{\mathrm{\&mu;<figure-callout\; id="4"\; label="l"\; filenames="A20081030276000131.png,A20081030276000141.png"\; state="\{\{state\}\}">l</figure-callout>}}{4\mathrm{\&pi;}}{\left(\frac{l}{w}\right)}^2[F\left(q\right){|}_{q=(w+s)/l}^{q=s/l}+F\left(q\right){|}_{q=(w+s)/l}^{(2w+s)/l}]---\left(8\right)$

Wherein $F\left(q\right)={\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="A20081030276000121.png,A20081030276000131.png"\; state="\{\{state\}\}">q</figure-callout>}}^2\mathrm{ar}\sinh \left(\frac{1}{q}\right)+\mathrm{qar}\sinh \left(q\right)+\frac{{\mathrm{<figure-callout\; id="3"\; label="q"\; filenames="A20081030276000121.png,A20081030276000131.png"\; state="\{\{state\}\}">q</figure-callout>}}^3}{3}-\frac{1}{3}{(1+q^2)}^{3/2}.$

Simultaneously we must consider primary coil and to the mutual inductance M between the mirror image coil of metal ground plate _Ij ^mFor the round screw thread line

$M_{\mathrm{ij}}^m=\mathrm{\&mu;}\sqrt{\mathrm{ab}}\&lsqb;(\frac{2}{k_{\mathrm{ij}}}-k_{\mathrm{ij}})K\left(k_{\mathrm{ij}}\right)-\frac{2}{k_{\mathrm{ij}}}E\left(k_{\mathrm{ij}}\right)\&rsqb;---\left(9\right)$

K wherein _Ij=4ab/ (4h ²+ (a+b) ²), a, b is the same.Above-mentioned various in,

Therefore, can get spiral type microstrip line total inductance is

$L=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{L}_i+2\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}\underset{j=i+1}{\overset{n}{\mathrm{\&Sigma;}}}{M}_{\mathrm{ij}}+\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\underset{j=1}{\overset{n}{\mathrm{\&Sigma;}}}{M}_{\mathrm{ij}}^m---\left(12\right)$

Embodiment 1

The structural representation of this routine microstrip antenna system as shown in Figure 4.Comprise that dielectric substrate 42, radiating element 41, the filter and the space length that are made of toroidal cavity resonator 44 and two quarter-wave resonance devices 45 are the feeder line of L3.The ground plane of this routine medium substrate 42 only is present in the filter and the feeder line back side, and radiating element 41 back sides do not have ground plane.The feed microstrip line 46 of filter also is the feeder line of microstrip antenna system simultaneously.This example adopts meander line in the space length L3 of the microstrip feed line of existing microstrip antenna, promptly the rectangular coil line 48 here adds microstrip filter, under the situation that the antenna system volume is increased, has realized the coupling of antenna and filter.The parameter of the microstrip feed line 46 of filter satisfies 50 Ω input coupling.According to the microstrip transmission line theory, data such as the width w by adjusting rectangular coil line 48, thickness t, distance s can change the parameter of microstrip feed line.Here can not satisfy 50 ohms impedance match requirements.Utilizing PSO algorithm (particle swarm optimization algorithm) or GA algorithm (genetic algorithm) to call Electromagnetic Simulation software I E3D, is the adaptive value function with the reflection coefficient S11 of feed end A, and structure is optimized, and makes S11 at least less than-10dB, guarantees the antenna performance after the associating.Fig. 5 is the relation of this routine microstrip antenna system S11 and frequency, and this microstrip antenna working frequency range is 2.45GHz-2.55GHz, is lower than-10dB in this frequency range internal reflection coefficient S 11.This structure by FILTER TO CONTROL the working frequency range of antenna, considered the coupling between antenna and the filter simultaneously, under the situation that does not increase antenna size, realized the coupling of antenna and filter.

Fig. 6 shows the reflection coefficient S11 of rectangular coil line and the relation curve of transmission coefficient S12 and frequency, this transmission line can be in 1GHz-4GHz and 0-3GHz scope transmission signals.Owing to adopt helical structure, take than small size when realizing quarter-wave length of transmission line, can be used in the co-design of antenna and filter the volume of minimizing microstrip antenna system.

Embodiment 2

This routine microstrip feed line is the round screw thread line, as shown in Figure 7.The parameter adjustment of round screw thread line microstrip feed line also can be by changing realizations such as helix width, spacing, the number of turns, helix radius.The relation of this routine feeder line transmission coefficient S21 and reflection coefficient S11 and frequency is referring to Fig. 8, and as can be seen, the reflection coefficient S11 of round screw thread line microstrip feed line is better than rectangular coil line microstrip feed line slightly, and is particularly apparent in view in 2～2.5GHz frequency range.

Embodiment 3

Fig. 9 shows the structure of equidistant meander line, and by adjusting spacing, bending times, live width etc. can meet the requirements of parameter in space length L3 scope.Figure 10 provides the transmission coefficient S21 and the reflection coefficient S11 comparison diagram of straight line microstrip line and equidistant meander line microstrip line, and two kinds of microstrip lines can keep the less loss transmission signals in the 0-10GHz scope as can be seen.Compare with the straight line microstrip line, the indentation microstrip line can be realized quarter-wave length of transmission line in shorter space length.In antenna and filter co-design, adopt equidistant zigzag Microstrip line will more save the space.

Embodiment 4

As shown in figure 11, be the structural representation of spacing gradual change zigzag Microstrip transmission line, Figure 12 shows the relation of transmission coefficient S21 and reflection coefficient S11 and frequency.The type transmission line transmission signals in the 0-9GHz scope produces less loss, because the microstrip line spacing diminishes gradually, makes this transmission line can realize quarter-wave length of transmission line in shorter space length.In antenna and filter co-design, adopt equidistant zigzag Microstrip line that antenna is connected with filter and will more save the space.

In the antenna system of the present invention, antenna (radiating element) and filter can adopt various structures, and particularly antenna structure is of a great variety, adopts coupled structure of the present invention, can realize the coupling of antenna and filter, go co-design.Microstrip antenna system of the present invention both can be used as reception antenna, also can be used as transmitting antenna, can be by selecting the suitable filters structure, the operating frequency of system is limited.

Claims (8)

1. integrated micro-strip antenna filter coupling structure comprises that attached to the radiating element on the dielectric substrate, filter and feeder line, described radiating element is connected with filter by feeder line, it is characterized in that, described feeder line is a meander line.

2. integrated micro-strip antenna filter coupling structure according to claim 1 is characterized in that, described meander line is equidistant meander line.

3. integrated micro-strip antenna filter coupling structure according to claim 1 is characterized in that, described meander line is a spacing gradual change meander line.

4. integrated micro-strip antenna filter coupling structure according to claim 1 is characterized in that, described meander line is the snail line.

5. integrated micro-strip antenna filter coupling structure according to claim 4 is characterized in that, described snail line is the rectangular coil line.

6. integrated micro-strip antenna filter coupling structure according to claim 4 is characterized in that, described snail line is the round screw thread line.

7. according to any described integrated micro-strip antenna filter coupling structure of claim 1～6, it is characterized in that described meander line is λ/4 transmission lines, described λ is the wavelength of radiating element centre frequency correspondence.

8. integrated micro-strip antenna filter coupling structure according to claim 7 is characterized in that, the described dielectric substrate back side and filter and feeder line corresponding position are coated with ground plane.

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