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The main factors affecting the performance of the

We know , GPS is a satellite by receiving the signal for positioning or navigation terminal ( what is GPS ) . In the process of receiving a signal which must be used in the antenna , the signal will be called the receiving antenna GPS antenna. GPS satellite signal and the divided L1 L2, respectively 1575.42MHZ frequency and 1228MHZ, wherein L1 is open to civil signals , the signal is circularly polarized (GPS Principles ) . The signal strength is about 166-DBM, a relatively weak signal. These characteristics determine the need to prepare for the GPS signal receiving antenna specialist . Here Xiaobian introduce the GPS car antenna performance and Precautions knowledge (GPS positioning ) . Affect the performance of the GPS antenna is mainly the following aspects


A ceramic piece : good or bad , and sintering of ceramic powders directly affect its performance. Now commercially used ceramic mainly 25 × 25,18 × 18,15 × 15,12 × 12. Ceramic sheet size , the greater the dielectric constant , the higher the resonance frequency , the better the acceptance . Most ceramic square design , to ensure consistency in the XY direction substantially resonant , so as to achieve a uniform closing star effect.


2, the silver layer : a layer of silver ceramic antenna surface can affect the antenna resonance frequency. Ceramic ideal GPS frequency accuracy falls 1575.42MHz, the antenna is very susceptible to the surrounding frequency environmental effects , particularly in the assembly of the machine must be adjusted by the shape of the silver surface coatings to adjust the frequency again held at 1575.42MHz . Therefore GPS antenna machine manufacturers in the procurement must meet antenna manufacturers, providing the whole sample for testing.


3, the feed point : ceramic antenna resonance signals collected and sent to the back-end through the feed point . Due to the antenna impedance , the antenna feed point at the center of generally not , but to make minor adjustments in the XY directions . Such simple impedance matching without increasing the cost . Only in a uniaxial direction called single partial antennas are made in the two-axis movement is called double side.


4, the amplifier circuit : carrying a ceramic PCB antenna shape and size . Since the GPS has a touchdown rebound characteristics , when the background is 7cm × 7cm ground without interruption , performance patch antenna can play to the extreme . Although the exterior of the structure and other factors, but try to maintain a considerable area and uniform shape . Amplifier gain must be selected to match the back-end LNA gain. Sirf before the GSC3F request signal input shall not exceed the total gain 29dB, otherwise the signal will produce oversaturated self-excited .


GPS antenna has four important parameters : Gain (Gain), VSWR (VSWR), noise figure (Noise figure), axial ratio (Axial ratio). With particular emphasis on the axial ratio , which is an important indicator of overall signal gain for different directions of difference . Because the satellites are randomly distributed in the sky hemisphere , so the sensitivity of the antenna in all directions to ensure both are very important to close . Receive antenna axial ratio performance, appearance of the structure , the whole internal circuits and EMI and other effects .


GPS antenna Precautions


1.GPS not 100% position, but do not believe the nonsense -GPS positioning indoors unlike cell broadcasting , anywhere can receive signals , many things can affect gps reception , including Sky satellite distribution , buildings , viaducts, waves , leaves , lattice thermal paper , something that will affect too much, in general, from the point of view gps location , you can see the area of the sky that can receive gps signal area .


(2) Do not use one or two , or a day or two , it was decided gps is good or bad - because the sky satellite states are different every day , maybe the same place , am the recipient cell , but can not locate the evening , there may be , there may be several days to locate the situation is not good.


(3) compare gps is good or bad , must be compared with the same time - a lot of people buy a new gps, will say that I had a better use of the sinking that kind of thing , but to say , but not correct , because the use of different time and place , and finally the result is a lot worse , you must use the long-term , or simultaneously with , the two kinds of gps can feel different points .


4.GPS signal strength meter , has been insufficient to buy a GPS reference - we buy gps, just look at the map of the reception tables may have previously quite accurate, but now gps, see the table in order to allow the recipient looking up , so there are false signals or signal simulation , etc., reception table is indeed very beautiful, but perhaps positioning allowed , not even the display is not necessarily correct .


5 There is no so-called indoor positioning gps- basically no signal is no signal indoors , the real indoor positioning , start from cold start in the room, but you can locate , real indoor positioning , but basically indoor positioning is meaningless no, because I'm not at home navigation.


6 buy gps, no need to purchase brand choice , but you can choose to use the chip inside - basically , doing a lot of gps manufacturer , vendor selection only consider service only, the recipient is not necessarily the best manufacturers , Generally say the same chip gps, different vendors do , the effect will not be much difference , so do not choose to select gps brand , you can choose gps receiver chip .


7 in the end I want to use Bluetooth , CF gps, or gps mouse -? Generally, this is a matter of debate , using Bluetooth or cf, must worry about gps or pda at any time without electricity problems , and higher costs, but you can navigate anywhere , using gps mouse is affordable and good reception , do not worry about the power problem , but cable problems.


8 positioning, GPS is not necessarily wrong - basically positioning error can be less than 20 meters , are regarded as good gps , and in addition , gps location is not very accurate in the way, the reason may be many possible adverse reception , causing error , it may be a problem with the map data , there may be a way very wide, so it looks like a stable offset gps road , with a long time you know gps or map issue.


9 Buy gps, specification table is for reference -gps specifications completed within a few seconds what position, what few meters error , sensitivity and so forth , these are nice to write , to really use to know , really, compare specifications table is a waste of time .


10 using the GPS, do not close communication costs - although we all know, but still it was always thought to be another close monthly fee.


11 When the store said a bad xxx gps , do not believe - may not be sold in the store , or another large stock of things , it is recommended that you buy the other a gps.


12.GPS able to put the car to put the car - in addition to an external antenna , gps mouse like this kind of thing , to put the car to put the car, because although there are waterproof gps , but long on the outside , will inevitably be linked time point , but also close to closing on and off to go, but will be dry on the outside to go Oh , we recommend carefully selected lattice thermal paper or thermal paper cut a hole in the frame , paste else looks not ugly.


13 If the GPS is a new buy for the first time , or the state is already a cold start , go to the open air outside the car be fixed positioning - As a positioning speed faster, and less likely to have some strange phenomenon , if under cold start conditions directly on the road, even if the signal is strong, but could not locate the destination of all Oh ! ! this is very important , positioning exhausted, and then into the car, the recipient will not see the car comparison poor , while the longer time single gps , satellite data can be stored longer time , if the long-term need , such as a ~ two weeks , gps cold start may be restored to the state .


Summary


GPS antenna is right-hand polarized ceramic dielectric , its components are: ceramic antenna , low noise signal modules , cables, connectors, this paper describes the main factors affecting the performance of the GPS antenna and Precautions basics. 


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