CN101697379A - Coplanar waveguide weighting series-fed antenna - Google Patents

Abstract

The invention relates to a coplanar waveguide weighting series-fed antenna which comprises a medium substrate, wherein an upper ground and a microstrip antenna array are arranged on one surface of the medium substrate, a gap is arranged between the upper ground and the microstrip antenna array, the widths of a first microstrip antenna unit, a second microstrip antenna unit, a third microstrip antenna unit, a fourth microstrip antenna unit, till a n-th microstrip antenna unit are different, and n is a positive integer. The whole antenna and a feed system are formed on one medium substrate by the coplanar waveguide weighting series-fed antenna. The antenna is formed by the serial connection of six or more weighting coplanar waveguide radiation units. A gap between each radiation unit and the floor is fixed. A distance Gemag among the radiation units is also fixed, and a connecting line among the radiation units is about Gemag/2 (Gemag is waveguide wavelength) so as to ensure that the maximum radiation direction is broadside. The impedance of each radiation unit is less than 50Omga and capacitive, and the impedance of the connecting line of the radiation units is more than 50Omga and inductive.

Description

Coplanar waveguide weighting series-fed antenna

Technical field

The present invention relates to a kind of coplanar waveguide weighting series-fed antenna, be applied to antenna and feeding network in radar system and the communication system.

Background technology

Co-planar waveguide and traditional microstrip line more also have its distinctive feature; Make connection in series-parallel simple, that the active passive device surface is mounted easier, reduced the loss that surface wave causes.In addition since the characteristic impedance of co-planar waveguide by the ratio decision of signal band line width and line of rabbet joint width, so its size can be adjusted according to the actual requirements flexibly.

In order to realize the particular requirement of antenna beam, will adopt suitable antenna array amplitude-phase to distribute, this makes the feeding network complex structure of aerial array, and introduced bigger loss, reduced the radiation efficiency of antenna, particularly under the frequency applications situation, this phenomenon is particularly serious.With parallelly feeding compare, the length of microstrip transmission line in the feeding network can be significantly shortened in series feed, reduces the loss of feeding network, this feeding classification widely adopts in fixed beam antenna.

Traditional little band series fed antenna has excellent specific properties such as main lobe width is narrow, cross polarization level is low, is widely used among microwave and millimeter wave radar and the communication system.Existing little band series fed antenna all adopts the series feed mode of constant amplitude mostly at present, so just can't have some defectives with avoiding:

(1) characteristic impedance of microstrip line is by the width and the length decision of band line, so its size can not be adjusted.

Therefore (2) the series feed emittance of constant amplitude can not be controlled the emittance of each unit, minor level effectively.

Summary of the invention

The invention provides the coplanar waveguide weighting series-fed antenna that a kind of main lobe width is narrow, cross polarization level is low, the present invention can control the emittance of each radiating element, reduces the antenna side lobe level effectively.

The present invention adopts following technical scheme:

A kind of coplanar waveguide weighting series-fed antenna, comprise: dielectric substrate, on a surface of dielectric substrate, be provided with upper ground surface and microstrip antenna array, between upper ground surface and microstrip antenna array, be provided with the slit, form described microstrip antenna array first microband antenna unit, second microband antenna unit, the 3rd microband antenna unit, the 4th microband antenna unit ... the width of n microband antenna unit does not wait, n is a positive integer, lower surface at dielectric substrate is provided with lower floor, and following ground is connected by plated-through hole with upper ground surface.

Coplanar waveguide weighting series-fed antenna has formed entire antenna and feed system on a dielectric substrate.Antenna is by six even more adds to weigh co-planar waveguide radiating element serial connection and form.Slit between each radiating element and the floor is fixed.Spacing between each radiating element also is fixed value (λ g), and connecting line is about λ g/2 (λ g is a guide wavelength) to guarantee that the greatest irradiation direction is that the limit is penetrated between each radiating element.The impedance of radiating element is capacitive less than 50 Ω, and the impedance of radiating element connecting line is perception greater than 50 Ω, and the two forms the LC resonator makes its resonance in center frequency points.The sheet material of stable performance and ripe PCB processing technology can guarantee precision and the reliability made.

Compared with prior art, coplanar waveguide weighting series-fed antenna has the following advantages:

1) the present invention adopts the series feed technical measures of weighting, antenna adopts the series feed mode of weighting, can control the emittance of each radiating element, reduce the antenna side lobe level effectively, can satisfy harsh secondary lobe and require to make it to have that main lobe width is narrow, cross polarization level is low.The narrow directional radiation capacity that improves antenna of main lobe width makes it can satisfy harsh directionality needs; Can eliminate noise better and cross level is low, guarantee the purity of polarization.

2) characteristic impedance of feed end is by the ratio decision of signal band line width and line of rabbet joint width, so the size of feed end (being the size of the signal band line and the line of rabbet joint) can be adjusted according to the actual requirements flexibly, this advantage is helping the integrated total system of antenna and front end system.

3) sheet material of stable performance and ripe PCB processing technology make antenna accuracy of manufacture height, can produce in batches.

Description of drawings

Fig. 1 is a structural front view of the present invention, and wherein, W1-W6 radiating element width, a are the co-planar waveguide gap width, and s is a feed mid line width, and g is the feed gaps width, and L is a connecting line length, and W is the connecting line width.It is dorsal view of the present invention.

Fig. 2 is a dorsal view of the present invention.

Fig. 3 is the calculating and the test result figure of return loss of the present invention.

Fig. 4 is an E face directional diagram of the present invention.

Fig. 5 is a H face directional diagram of the present invention.

Embodiment

Embodiment 1

A kind of coplanar waveguide weighting series-fed antenna, comprise: dielectric substrate 1, on a surface of dielectric substrate 1, be provided with ground, upper strata 2 and microstrip antenna array 3, between upper ground surface 2 and microstrip antenna array 3, be provided with slit 4, form described microstrip antenna array 3 first microband antenna unit, second microband antenna unit, the 3rd microband antenna unit, the 4th microband antenna unit ... the width of n microband antenna unit does not wait, and n is a positive integer.Lower surface at dielectric substrate is provided with lower floor 5, and following ground 5 is connected by plated-through hole 6 with upper ground surface 2.Have between the microband antenna unit and satisfy following relational expression

$\left\{\begin{array}{c}{g}_1(1-{\left|{\mathrm{\Γ}}_1\right|}^2)=a_1\\ g_2\frac{\left({1-g}_1\right)}{g_1}(1-{\left|{\mathrm{\Γ}}_2\right|}^2)a_1=a_2\\ ...........................\\ g_i\frac{\left({1-g}_{i-1}\right)}{g_{i-1}}(1-{\left|{\mathrm{\Γ}}_i\right|}^2)a_{i-1}=a_i\\ ...........................\\ g_n\frac{(1-g_{n-1})}{g_{n-1}}(1-{\left|{\mathrm{\Γ}}_n\right|}^2)a_{n-1}=a_n\end{array}\right.---\left(1\right)$

$\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{g}_i=1,$ $g_i=\frac{G_{\mathrm{ri}}}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{G}_{\mathrm{ri}}},$ ${\mathrm{\Γ}}_i=\frac{{1-g}_i}{1+g_i}---\left(2\right)$

G wherein _iBe the normalization radiation conductance of each microstrip element, Γ _iBe the reflection coefficient of i knot, G _RiBe the radiation conductance of i unit, by radiation conductance G _RiCan be in the hope of the radiation witdth W of each radiating element _i, a ₁, a ₂..., a _i..., a _nBe the normalization weight coefficient, by radiation conductance G _RiCan ask for the radiation witdth W of each radiating element _iMethod is the method for knowing altogether at present, and concrete grammar is:

$G_r=\frac{1}{120{\mathrm{\π}}^2}\underset{0}{\overset{\mathrm{\π}}{\∫}}{\sin }^2\left(\frac{K_{0}W\cos \mathrm{\θ}}{2}\right){\tan }^2\mathrm{\θ}\sin \mathrm{\θd\θ}---\left(3\right)$

K ₀Wave number (K for free space ₀=2 π c/f _r), wherein c is the velocity of wave of free space, f _rCentre frequency for antenna.

For example: this method can adopt Taylor's weighting method to ask normalization coefficient, and described ai is the normalization weight coefficient, and concrete grammar is:

Ask Taylor's weighting excitation amplitude t of each radiating element _i

Wherein $t_i=1+2\underset{m=1}{\overset{q-1}{\mathrm{\Σ}}}{S}_n\left(m\right)\cos \left(\mathrm{mp}\right)$

In the formula

Q is Taylor's factor (can look into " Theory and Application of Antenna Arrays " Wiley NewYork, 1974, get q=5 herein), and L is the linear array total length, and N is a positive integer, d=L/ (unit number-1)

$S_n\left(m\right)=\left\{\begin{array}{cc}1& m=0\\ \frac{{[(q-1)!]}^2}{(q-1+m)!(q-1-m)!}\underset{i=1}{\overset{q-1}{\mathrm{\&Pi;}}}\{1-\frac{m^2}{{\mathrm{\&sigma;}}^2\{A^2+{(q-\frac{1}{2})}^2\}}\}& 0<m<q\end{array}\right.---\left(5\right)$

Wherein, $\mathrm{\&sigma;}=\frac{q}{\sqrt{A^2+{(q-\frac{1}{2})}^2}}$ Be broadening factor

Utilize $a_i=\frac{t_i}{\underset{1}{\overset{n}{\mathrm{\&Sigma;}}}{t}_i^2}$ Try to achieve the weight coefficient a of each radiating element _i

Embodiment 2

We have realized the coplanar waveguide weighting series-fed antenna of above introduction on 10.65GHz.The substrate dielectric constant is 2.65, and the substrate height is 1mm.

The specific design parameter sees the following form

??s	??g	??a	??w	??L	??h	??W 1
							??2.25	??0.5	??0.5	??1.5	??10.5	??1	??9
??W 2	??W 3	??W 4	??W 5	??W 6	??f r	??ε r
							??9	??8	??6	??3.5	??3	??10.65	??2.65

The present invention is to first microband antenna unit, second microband antenna unit, the 3rd microband antenna unit, the 4th little band sky

The line unit ... the width of n microband antenna unit is satisfied, and upward embodiment is described.

Antenna has been carried out test and emulation, and its result is as follows:

With reference to Fig. 3, the minimum echo loss of designed antenna is-20dB.Return loss during less than-10dB the beamwidth of antenna be 260MHz (10.54GHz-10.8GHz), solid line is a test curve, dotted line is a simulation curve.

With reference to Fig. 4, designed antenna side lobe is-16dB, and minor level-13dB compares with the constant amplitude weighting, and antenna side lobe has the decline of 3dB, has reached the series feed Expected Results of weighting.

The operation principle of coplanar waveguide weighting series-fed antenna and the course of work:

Antenna energy is by radiation step by step behind the feed end, and the radiation of antenna comes radiation by the equivalent longitudinally radiating slot of radiating element.Obtain the radiation conductance of each radiating element according to the ratio of each radiating element emittance, calculate the radiation witdth of each radiating element again according to radiation conductance.Connecting line is about λ between each radiating element _g/ 2 (λ _gBe guide wavelength) to guarantee that the greatest irradiation direction is that the limit is penetrated.The adjustment purpose of radiating element radiation witdth is will control the emittance of each radiating element and then effectively reduce secondary lobe.Radiating element and connecting line are formed a resonant element makes each radiating element all be operated under the condition of resonance, thereby makes antenna that less insertion loss be arranged.Connecting line is about λ between the radiating element _g/ 2 (λ _gBe guide wavelength) to guarantee that the greatest irradiation direction is that the limit is penetrated.

The present invention utilizes co-planar waveguide to do the feed part, and antenna adopts coplanar waveguide structure can effectively suppress surface wave, reduces the loss of antenna, improves radiation efficiency.In the design of co-planar waveguide array element, introduced the weighting theory, controlled the emittance of each radiating element accurately, thereby effectively reduce antenna side lobe.

Claims (2)

1. coplanar waveguide weighting series-fed antenna, comprise: dielectric substrate (1), it is characterized in that on a surface of dielectric substrate (1), being provided with upper ground surface (2) and microstrip antenna array (3), between upper ground surface (2) and microstrip antenna array (3), be provided with slit (4), first microband antenna unit of forming described microstrip antenna array (3), second microband antenna unit, the 3rd microband antenna unit, the 4th microband antenna unit, ... the width of n microband antenna unit does not wait, n is a positive integer, lower surface at dielectric substrate is provided with lower floor (5), and following ground (5) is connected by plated-through hole (6) with upper ground surface (2).

2. coplanar waveguide weighting series-fed antenna according to claim 1, it is characterized in that first microband antenna unit, second microband antenna unit, the 3rd microband antenna unit, the 4th microband antenna unit ... the n microband antenna unit satisfies formula

$\left\{\begin{array}{c}{g}_1(1-{\left|{\mathrm{\&Gamma;}}_1\right|}^2)=a_1\\ g_2\frac{(1-g_1)}{g_1}(1-{\left|{\mathrm{\&Gamma;}}_2\right|}^2)a_1=a_2\\ ...........................\\ g_i\frac{(g-g_{i-1})}{g_{i-1}}(1-{\left|{\mathrm{\&Gamma;}}_i\right|}^2)a_{i-1}=a_i\\ ...........................\\ g_n\frac{(1-g_{n-1})}{g_{n-1}}(1-{\left|{\mathrm{\&Gamma;}}_n\right|}^2)a_{n-1}=a_n\end{array}\right.---\left(1\right)$

$\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{g}_i=1,$ $g_i=\frac{G_{\mathrm{ri}}}{\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{G}_{\mathrm{ri}}},$ ${\mathrm{\&Gamma;}}_i=\frac{1-g_i}{1+g_i}---\left(2\right)$

G wherein _iBe the normalization radiation conductance of each microstrip element, Γ _iBe the reflection coefficient of i knot, G _RiBe the radiation conductance of i unit, by radiation conductance G _RiCan be in the hope of the radiation witdth W of each radiating element _i, a ₁, a ₂..., a _i..., a _nBe the normalization weight coefficient.

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