Embodiment
Below in conjunction with accompanying drawing a kind of micro-strip array antenna of the embodiment of the invention is described in detail.
Should be clear and definite, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills are not making all other embodiment that obtained under the creative work prerequisite, all belong to the scope of the present invention's protection.
A kind of micro-strip array antenna of embodiments of the invention; Comprise the antenna array of forming by two above bays; The same delegation of said antenna array comprises two above bays; Be arranged in bay with delegation, the corresponding connection of each output port of each bay and a multipath power distributor, and and the adjacent antenna array element that do not wait of the distance of the row center line of said antenna array between be connected with the transformer section of cascade.
Multipath power distributor can be said with reference to figure 2, is made up of microstrip line, and comprising input port B is arranged, output port C, A are distributing point.Shown in Figure 2 is one No. four power divider, thereby four output ports are arranged.No. four power dividers for adopting in the preferred embodiment of the present invention shown in Figure 2; Realize the present invention; The multipath power distributor that can correspondingly with the columns of antenna array adopt any greater than two-way for example, can be No. five power dividers or No. six power dividers etc.
As shown in Figure 3, if this antenna array is the matrix of N * 4, explain that then each row has 4 bays 100 in this antenna array, with the corresponding connection of four output ports of each bay 100 in the delegation with one No. four power divider 300.In like manner, if the matrix of N * M then will couple together with each bay 100 in the delegation through a M road power divider, and need N M road power divider altogether.
For array antenna shown in Figure 1; Make the main lobe wave beam of array antenna can cover this track; Do not diffuse into adjacent lane again, the array number of array antenna is wanted eight at least, needs to use a plurality of two-way power dividers could the electric current of distributing point be delivered to each antenna radiation unit.Because per two bays just need to use a two-way power divider feed, thereby array antenna shown in Figure 1 needs 15 two-way power dividers altogether.Thereby the feed structure of such array antenna is very complicated, and antenna volume is huge, is unfavorable for the miniaturization of system configuration.
Because embodiments of the invention adopt a multipath power distributor to connect by above bay with two of delegation; Can reduce the number of power divider; If the matrix of N * 4 then only needs N No. four power dividers, thereby reduce the volume of antenna array.
And be connected with the transformer section of cascade between the adjacent antenna array element that the distance of the row center line of said antenna array does not wait; Non-constant amplitude feed can be realized being positioned at, and the purpose of suppressed sidelobes level can be reached through the impedance magnitude of each transformer section in the transformer section of adjustment cascade with the bay of delegation.Owing to adopt a multipath power distributor to connect with each bay in the delegation; Thereby the microstrip line length that connects between each bay in the present embodiment is shorter; Consequent medium and conductor losses are less, and the suppressing antenna main lobe gain descends preferably.
On the basis of such scheme, the said bay that is arranged in delegation, to both sides, the spacing between the bay reduces gradually from the centre.Also be connected with transformer section 400 between each said bay 100 and the corresponding multipath power distributor.
Transformer section 400 is generally the microstrip line that a segment length is about 1/4 guide wavelength.Guide wavelength λ refers to the wavelength of electromagnetic wave in microstrip line, can pass through formula
Calculate, wherein v is the propagation velocity of electromagnetic wave in microstrip line, and f is electromagnetic frequency.The microstrip line that one segment length is approximately the quarter-wave guide wavelength can transform to desirable real number input impedance with the real number load impedance.Therefore; Can will arrive identical to the input impedance matching between the distributing point (for example A point) with each bay (for example first row) of delegation through transformer section; Thereby distributing point is controlled to be the integral multiple of 2 π to phase difference between the distributing point of each bay, thereby reaches purpose with the bay homophase feed of delegation.And in the antenna array shown in Fig. 1; The non-constant amplitude feed of each array element that Sidelobe Suppression adopted utilizes T type branch line to realize; It can encourage higher mode at the discontinuity place; Be difficult to guarantee the homophase feed of each array element, a series of problems such as can cause like this that antenna radiation efficiency descends, main lobe greatest irradiation center, deviation in driction track and sidelobe level are raised have increased the transaction probability of errors.Present embodiment of the present invention can be realized the homophase feed through simple power division network, and can avoid occurring above-described problem.
Also be connected with transformer section 600 and transformer section 700 in the said antenna array between the different rows, and the spacing between the different rows can equate.To be positioned on the row center line of antenna array outermost two transformer sections and represent that with 600 middle usefulness 700 is represented.In order to reach the purpose of homophase feed, the width of transformer section 600 and transformer section 700 is different usually, i.e. impedance is different.Through transformer section 600 and transformer section 700 with connecting between the different rows, thereby can guarantee the impedance matching and the homophase feed of entire antenna matrix.
The main lobe of array antenna on the greatest irradiation direction, also can produce some parasitic secondary lobe and back lobes, wherein near first sidelobe level of main lobe generally than higher, can produce other channels and disturb.The sidelobe level of array antenna receives the influence of various factors such as diffraction effect and machining accuracy of amplitude and phase place, the mutual coupling between the bay, the sheet edge of structure, each bay feed of feeding network.Wherein, the feed amplitude of bay has decisive influence to the sidelobe level size.The sudden change discontinuity of feed amplitude can cause the appearance of big secondary lobe, can make discontinuity minimum and locate become zero distribution of gradual change on the edge of, thereby make sidelobe level minimum.Generally speaking, if to amplitude feeds such as each array elements, the sidelobe level of array antenna is about-13dB, can not satisfy the ETC demands of applications.
If with two segment length is the transformer section cascade of quarter-wave guide wavelength, just can form the transformer section of a similar transformer.For example, the impedance of supposing feeder line between the adjacent antenna array element is 100 ohm, and length is a guide wavelength.If will be wherein length be that the feed line impedance of quarter-wave guide wavelength becomes 50 ohm, just can obtain the feed amplitude and be 1: 2 array antenna.And the conversion of this impedance only just can realize through the live width that changes microstrip line, does not need the T type branch line in the two-way power splitter, greatly reduces the feeding network difficulty of design.
On the basis of such scheme; In the said bay, comprise: near first transformer section 510 in the said antenna array outside with near second transformer section 520 at said antenna array center with the transformer section 500 of the cascade that is connected between the bay that the row distance between center line of said antenna array does not wait with delegation.In order to reach the purpose that the feed amplitude is reduced to both sides array element by center array element gradually, the width of said first transformer section 510 is greater than the width of said second transformer section 520.
Therefore for embodiments of the invention; First transformer section 510 and the width of second transformer section 520 of the transformer section 500 through the control cascade; The then impedance of these two transformer sections of may command, thus can reach the purpose of controlling the feed amplitude between the adjacent antenna array element.The feed amplitude ratio of the transformer section through regulating cascade has been realized non-constant amplitude feed, thereby has been reached the purpose of control sidelobe level.
Below the antenna array through 4 * 4 is an example, and the present invention will be described.
As shown in Figure 4, be the sketch map of the antenna array of embodiments of the invention 4 * 4.In the present embodiment, the distance between two array antenna array element L2 and the L3 is 0.7~0.9 guide wavelength.For a preferable scheme, the distance between L2 and the L3 can be 0.7 guide wavelength, and the distance between L1 and the L2, between L3 and the L4 is than the little 0.3~0.5mm of the distance between L2 and the L3.
In the transformer section 500 of cascade, the ratio of the impedance 510 of said first transformer section and the impedance of said second transformer section 520 was preferably 58: 100 less than 58: 100, can access lower sidelobe level thereby distribute according to Chebyshev.
It is the amplitude distribution of optimization compromise that Chebyshev distributes, through adopting the distribute feed amplitude of controlling level bay of Chebyshev, and under the situation that guarantees main lobe gain, effective suppressed sidelobes level.In an embodiment of the present invention, it is 40~60 ohm that the impedance 510 of first transformer section can be chosen impedance, and it is 80~120 ohm that second transformer section 520 can be chosen impedance.Distribute according to Chebyshev, the ratio of the feed amplitude of center array element and edge array element is less than 0.58 o'clock, can realize that sidelobe level is less than-17dB.
In addition, bay all passes through transformer section 400 input impedance matching to 80 with each bay~120 ohm in each row.Also will be impedance-matched to 80~120 ohm between the different rows through transformer section 600 and 700.A kind of preferred scheme does, the input impedance of bays all in the entire antenna matrix is all matched 100 ohm.In this way, can realize the impedance matching of entire antenna matrix and each bay in the whole array antenna carried out the homophase feed.
In a preferred embodiment of the present invention, the substrate dielectric constant of this array antenna is 2.55, and loss tangent is 0.0019, and the thickness of substrate is 1.6mm.The design of feeding network for ease; Bay is selected the left-hand circular polarization or the right-handed circular polarization antenna of single-point feedback; Thereby can on antenna, encourage simultaneously the transverse magnetic mode of 90 ° of polarization orthogonal, phase phasic difference, synthetic polarization of electromagnetic field mode is a circular polarization.Concrete way of realization includes but not limited to several kinds shown in Fig. 5: cut a pair of leg-of-mutton circular polarized antenna array element X1; Cut a foursquare circular polarized antenna array element X2, the circular polarized antenna array element X4 of the circular polarized antenna array element X3 of diagonal angle feed and center grooved.Obtain Fig. 6 and antenna performance shown in Figure 7 when in this case, 4 * 4 antenna array being impedance-matched to 100 ohm.Fig. 6 is the standing wave curve of present embodiment array antenna, and Fig. 7 is the lobe directions figure of present embodiment array antenna.As shown in Figure 6, standing-wave ratio is less than the 400MHz nearly of the impedance bandwidth below 2, the needed 50MHz bandwidth of the system that is far longer than.As shown in Figure 7, the main lobe gain of antenna reaches 17dB, and level all is 22 degree with vertical lobe width, and sidelobe level-17dB satisfies the needs that ETC communicates by letter fully.
The above; Be merely embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.