The ceramic GPS antenna is a right-hand polarized ceramic medium, and its components are a ceramic antenna, low-noise signal module, cables, and connectors. This article mainly introduces the main factors affecting the performance of GPS antennas and the basic knowledge of their use.
First. 4 Factors affecting GPS antenna performance
1. Ceramic sheet
The quality of the ceramic powder and the sintering process directly affect its performance. The ceramic sheets currently used in the market are mainly 25×25, 18×18, 15×15, 12×12. The larger the area of the ceramic sheet, the larger the dielectric constant, the higher the resonance frequency, and the better the receiving effect.
The ceramic sheets are mostly square in design to ensure that the resonance in the XY direction is basically the same, so as to achieve the effect of uniform star collection.
2. Silver layer
The silver layer on the ceramic antenna surface can affect the antenna resonance frequency. The ideal GPS ceramic chip frequency point accurately falls at 1575.42MHz, but the antenna frequency point is very easily affected by the surrounding environment, especially when assembled in the whole machine, the frequency point must be adjusted to maintain the frequency point at 1575.42MHz by adjusting the shape of the silver coating.
Therefore, GPS manufacturers must cooperate with the antenna manufacturers when purchasing antennas, and provide complete samples for testing.
3. Feed points
The ceramic antenna collects the resonance signal through the feed point and sends it to the back end. Due to antenna impedance matching, the feed point is generally not in the center of the antenna but slightly adjusted in the XY direction.
This impedance matching method is simple and does not increase the cost. Moving only in the direction of a single axis is called a single-biased antenna, and moving in both axes is called a double-biased antenna.
4. Amplifying circuit
The shape and area of the PCB carrying the ceramic antenna. Because GPS has the characteristics of ground bounce, when the background is 7cm×7cm uninterrupted ground, the effectiveness of the patch antenna can be exerted to the extreme.
Although restricted by factors such as appearance and structure, try to keep a considerable area and uniform shape. The choice of the gain of the amplifying circuit must match the gain of the back-end LNA. Sirf’s GSC3F requires that the total gain before signal input should not exceed 29dB, otherwise the signal will be oversaturated and will cause self-excitation. (Noise figure), axial ratio (Axial ratio).
Among them, the shaft ratio is particularly emphasized, which is an important indicator to measure the difference of the signal gain of the whole machine in different directions.
Since satellites are randomly distributed on the hemispherical sky, it is very important to ensure that the antennas have similar sensitivity in all directions.
The axial ratio is affected by the antenna performance, appearance structure, internal circuit of the whole machine, and EMI.
Second. Precautions for using GPS antenna
1. GPS cannot be 100% positioned
GPS is not like a mobile phone broadcast, it can receive signals anywhere, many things will affect the GPS reception, including the distribution of sky stars, buildings, viaducts, radio waves, leaves, grid thermal paper, etc.
Generally speaking, looking up from the GPS position, the area where the sky can be seen is the area where the GPS can receive the signal.
2. Don't use it once or twice, or one or two days, it will determine the quality of GPS
Since the status of the sky satellites is different every day, maybe the same place, the reception is full in the morning, but the location cannot be located at night, it is possible, or it may be bad for several days.
3. To compare the quality of GPS, you must compare them in the same place at the same time
Many people who buy a new GPS will say that the one they used before is better, but in this way, it is not correct, because the time and place of use are different, the final result is much worse, and it must be used for a long time or at the same time in order to feel the difference between the two types of GPS.
4. GPS reception intensity meter is no longer sufficient as a reference for GPS purchase
Everyone who buys GPS will only look at the reception table on the electronic map. It may be quite accurate before, but nowadays, in order to make the reception table look good, there are fake signals, simulated signals, etc. The reception meter is indeed very beautiful, but it may not be positioned correctly or even not displayed correctly.
5. Should I use Bluetooth, CF GPS, or vehicle GPS?
Generally speaking, this is a matter of different opinions. When using Bluetooth or cf, you must worry about the problem of GPS or PDA running out of power at any time, and the cost is high, but you can navigate anytime, anywhere,
The use of vehicle GPS is economical, affordable, and good. You don’t have to worry about power problems, but the cable is troublesome.
6. Inaccurate positioning is not necessarily the fault of GPS
Basically, the positioning error can be within 20 meters, which is considered a good GPS. In addition, the GPS position is not very accurate on the road. There may be many reasons, and the reception may be poor, causing errors.
It may be a problem with the map data, or it may be a road. It is very wide, so it seems that the GPS is stably offset from the road. After a long time, you will know whether it is a GPS or a map problem.
7. Buy GPS, the specification table is for reference only
What GPS specifications can complete positioning in a few seconds, what errors in meters, sensitivity, and so on. These are all well-written, and you will know it only when you really use it. To be honest, comparing specifications is a waste of time.
8. Use GPS, no communication fee
Although everyone knows it, there are still people who always think that another monthly fee will be charged.
9. Vehicle GPS can be placed in the car
In addition to external antennas, things like vehicle GPS can be placed in the car, truck, and trailer as long as they can be placed in the car because although the GPS is waterproof, it will inevitably be exposed to water if it is placed outside for a long time.
10. If GPS is newly purchased for the first time, or it is already in a cold-start state, please go to an open place to locate outside the car
In this way, the positioning speed is faster, and there will be less strange phenomena. If you go directly on the road in the cold start state, even if the signal is very strong, you may not be able to locate the destination!!
After positioning, put it in the car to see if the reception in the car will be worse. In addition, the longer the single GPS is used, the longer the satellite data can be saved. If it is not used for a long time, the same By two weeks, GPS may return to a cold start state.
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