Summary of the invention
The purpose of this invention is to provide and a kind ofly be fit to be installed on the low orbit satellite, receive double-frequency GPS antenna through the GPS occultation signal of atmosphere refraction.Because occultation weak output signal, GPS occultation antenna require gain greater than 10dB, generally adopt the array antenna scheme.1 * 4 array antenna that antenna of the present invention is made up of four element antennas realizes that four element antennas are equally distributed.Element antenna adopts stacked slit coupled microstrip antenna form.Form by two-layer radiation medium plate and one deck feed dielectric plate.
The present invention has considered the mechanical performance and the temperature characterisitic of antenna when design in addition, to satisfy the operational environment of satellite.Adopt in radiation patch on the basis of four bars support, hollow space is filled support with the medium honeycomb, bottom reflecting plate adopts the lightweight aluminium cellular board, and this kind lightweight construction has good shock resistance and anti-vibration ability, satisfies spaceborne requirement.
Two carrier frequencies of GPS are respectively: L1=1575.42MHz, L2=1227.6MHz.The design broad-band antenna covers two frequencies certain difficulty.Take all factors into consideration several antenna forms, element antenna is selected to realize with stacked slit coupled microstrip antenna form.Element antenna adopts stacked slit coupled microstrip antenna form, and two frequency ranges are used different radiation patch, and two frequencies are separated from each other, and have taken into account two frequency ranges.Feeding network adopts the feeding classification of slit coupling in order to obtain wide frequency band.The cross gap coupling that adopts centering simultaneously is to obtain circular polarization.Because in this case, the line polarization wave of two quadratures is encouraged separately, and two line polarization wave amplitudes are identical, and phase difference is 90 °, therefore can obtain axial ratio bandwidth preferably.
Double-frequency GPS antenna of the present invention is fit to be installed in and utilizes Radio occultation to carry out atmosphere and ionospheric probing on the low orbit satellite.
The advantage of invention
1. double-deck radiation patch is two frequency ranges of corresponding GPS respectively, and two frequency ranges are used different radiation patch, and two frequencies are separated from each other, and have taken into account two frequency ranges.
2. the feeding classification of cross gap coupling, the line polarization wave of two quadratures is encouraged separately, and two line polarization wave amplitudes are identical, and phase difference is 90 °, therefore can obtain axial ratio bandwidth preferably.
3. adopt the four-point feed mode, antenna has phase center stability preferably.
4. support section adopts the medium honeycomb to fill, and the scheme of aluminum honeycomb panel is adopted in the bottom, and in light weight, good mechanical property is beneficial to spaceborne.
Embodiment
Fig. 1 is the element antenna structure, adopts stacked slit coupled microstrip antenna form, and two frequency ranges are used different radiation patch, and two frequencies are separated from each other, and have taken into account two frequency ranges.Feeding network adopts the feeding classification of slit coupling in order to obtain wide frequency band.The cross gap coupling that adopts centering simultaneously is to obtain circular polarization.Because in this case, the line polarization wave of two quadratures is encouraged separately, and two line polarization wave amplitudes are identical, and phase difference is 90 °, therefore can obtain axial ratio bandwidth preferably.
Stacked slit coupled microstrip antenna, form by two-layer radiation medium plate, one deck feed dielectric plate and reflected bottom plate, it consists of upper strata radiation patch and lower floor's radiation patch respectively on two-layer radiation medium plate, below two-layer radiation medium plate, be the feed dielectric plate, the cross gap feed is arranged on the feed dielectric plate, below feeder panel, also have reflected bottom plate.Between two radiation medium plates, between feed dielectric plate and the lower floor's radiation medium plate, backing material is arranged all between feed dielectric plate and the reflected bottom plate.
The selection of the major parameter of decision antenna performance:
(1) selection of dielectric-slab: in general, low-k and relative thicker medium bandwidth can compare broad.But the energy that is coupled to bottom layer of patches is along with the thickness of medium increases and reduces, and dielectric thickness and dielectric constant also influence the mutual coupling between upper strata paster and the lower floor's paster.Selecting dielectric constant for use is 2.3, and thickness is the dielectric-slab of 0.8mm.
(2) length of paster and width: constitute for 90 ° because circular polarization is linear polarization phase shift by two quadratures, so paster to require be foursquare.Owing to the close coupling between two pasters, the size of paster must be taken all factors into consideration two frequencies and design.Radiation patch corresponding L1 frequency in upper strata is the square of 78mm * 78mm.The corresponding L2 frequency of lower floor's radiation patch is the square of 83mm * 83mm.
(3) length in slit and width: it mainly is to be controlled by the length in slit that signal is coupled to bottom layer of patches from feeder line.Long slit can be improved the degree of coupling but also be increased unwanted backward radiation simultaneously.The width in slit also influences the degree of coupling, but does not have effect length so obvious.Determine that the slit is the rectangle of 51.6mm * 3.8mm.
(4) spacing between each layer: the spacing between each layer influences the mutual coupling between upper strata radiation patch and the lower floor's radiation patch, also influences the output of feeding network energy.The spacing of upper strata radiation medium plate and lower floor's radiation medium plate is 7mm, and the spacing of lower floor's radiation medium plate and feed dielectric plate is 11mm, and feed dielectric plate and reflected bottom plate spacing are 15mm.
Fig. 2 is the antenna feeding network schematic diagram, its effect be with cross gap coupling obtain etc. the linear polarization signal of amplitude synthesize a right-handed circular polarization signal and finish impedance matching simultaneously, utilize microstrip circuit to realize.Article four, feeder line synthesizes one tunnel output by the constant-amplitude signal that the slit coupling obtains by three " Wilkinson " power combiners.Each bar slit of cross gap and two feeder line quadratures wherein, the signal of the two ends coupling in a same like this slit has just been introduced one 180 ° phase shift.Simultaneously, also exist 90 ° phase shift between two slits, on four distributing points, just formed 0 °, 90 °, 180 °, 270 ° continuous phase change like this.Two " Wilkinson " power combiners near distributing point are synthetic with the distributing point signal (one of them introduces 90 ° of phase shifts) of two vicinities.The input of the 3rd power combiner is linked in one of them synthesizer output with an other power combiner after 180 ° of phase shifts.The input and output impedance of power combiner is 50 ohm of couplings.Feeding network designs on the centre frequency of 1.4GHz, can guarantee that it covers L1 and two frequencies of L2.
Fig. 3 is an antenna power synthesizer schematic construction, and 1 ~ 4 input is with the corresponding respectively output of receiving 4 element antennas of cable, and behind two " Wilkinson " power combiners, the concentration of energy of entire antenna is at delivery outlet.
Fig. 4 is antenna shapes figure, four squares are represented four stacked slit coupled microstrip antennas, 1 * 4 array antenna that antenna is made up of four element antennas, four element antennas are equally distributed, element antenna adopts stacked slit coupled microstrip antenna form, is made up of two-layer radiation medium plate, one deck feed dielectric plate and reflected bottom plate.
Four element antennas are in one line, the interval between the adjustment unit antenna, the gain that makes them is with superimposed.Can realize the design of array antenna.
Fig. 5 is the antenna cross-section structure, the corresponding L1 frequency of upper strata paster media plate, and the corresponding L2 frequency of lower floor's paster media plate also has feeder panel and reflected bottom plate below.For satisfying spaceborne structural requirement, adopt at each layer dielectric-slab on the basis of four bars support, hollow space is filled support with glass fibre reinforced plastic honeycomb plate.Filled support, bottom reflecting plate adopts the lightweight aluminium cellular board, this kind lightweight construction, but good shock resistance and anti-vibration ability are arranged, and make antenna have good structural behaviour, satisfy spaceborne requirement.