GPS Active Antenna & GPS Passive Antenna

GPS antennas play an important role in agriculture, aviation, environment, maritime transportation, public safety and disaster relief, railways, space, surveying and mapping. It has high positioning accuracy and fast satellite collection speed. GPS antennas can be divided into active and passive, so what is the difference between both items?

Passive GPS antenna: When using a passive GPS antenna, because there is only one ceramic chip to receive the satellite signal from the sky, it is directly connected to the RF-IN pin of the module. This connection method has a simple structure, mature technology, and small footprint, suitable for Yu emphasizes on compact space GPS navigation products, Bluetooth GPS, mobile GPS and other small GPS consumer products.

The layout of this antenna is from the pin of the antenna to the RF-IN pin of the module. This wire needs to be matched with 50 ohm impedance, and there must be no electromagnetic interference near the antenna. The PCB design and the EMI design requirements of the whole machine are relatively high. High, but if well designed passive antenna GPS products also have very good performance and consume less power.

Active GPS antenna: Usually for devices or vehicle-mounted devices, since the device is often far away from the GPS receiving module, considering the convenience of installation, there may be a distance of more than 1 meter. In this case, we can only choose to have The source GPS antenna needs to be compensated for signal attenuation of the antenna length. Generally, there are two-stage low-noise amplifiers (LNA) to amplify the front-end signal of the antenna. The amplified signal is output through the cable, and the cable synchronously provides the DC voltage required by the LNA.

Because the signal received by the antenna is received and amplified in the active antenna receiving head, and is far away from the GPS equipment or other electrical equipment, the source of interference is minimal, and the installation location can be selected in a very ideal environment due to the extended antenna distance. Therefore, the signal is often felt stronger in actual use.

The common GPS antennas are all square, and the satellite signal is resonated by the silver layer on the surface and the ceramic body. The disadvantage of the square antenna is that the antenna surface must face the sky for its signal to be good.
And like the four-arm helical antenna (GPS omnidirectional antenna), the antenna is cylindrical, and the way of collecting stars is different. It can collect stars in 360 degrees, which is its benefit! The signal of the square antenna is almost the same as the omnidirectional antenna (3db).
Because the antenna surface is a silver layer, its anti-oxidation ability is very weak (hand sweat, rain, moisture...) These will oxidize the surface of the antenna. After a long time, the silver layer does not look so bright, it will produce a rust-like color, this antenna will affect the signal of the receiving star (GPS antenna frequency is: 1575.42), will produce frequency deviation (frequency deviation High or low), resulting in a small number of satellites, a signal that is not strong enough, and poor multipath expansion capability (multipath refers to the signal reflected by the glass, the signal reflected by the leaves, the signal reflected by the water...). Because GPS works by directly receiving 24 satellites in the sky, the more GPS receives multipath signals, the greater its drift range will be!

Therefore, if the product structure allows, it is recommended to add a shell to the antenna, preferably waterproof. Such as: The good thing is that it is anti-oxidation and anti-interference EMC (wire interference or radiation interference), so the general four-axis aircraft model is to put the GPS antenna on top, higher than all other electronic devices!

In addition, regarding the difference between active and passive GPS antennas: the so-called passive antenna is a ceramic body with no circuit amplification part; the active antenna is the ceramic body plus level 1 or level 2 amplification. The signal of the passive antenna is around 3dbi, and the signal of the active antenna is around 18dbi (level 1 amplification). The signal of the antenna does not determine the quality of the entire product, but also depends on the matching between the GPS antenna and the GPS module. Passive antenna + GPS module, the circuit part is amplified at level 2, the signal reaches 28dbi, this effect will be very good. Active antenna 18dbi+GPS module, the circuit part is amplified at level 1, and the signal is almost at 28dbi, so the effect is the same! So it's not that active antennas must be effective.

Contact: Effy

Email: sales@fyxdz.com

Mobile: 86 - 13509623256