The main function of GPS antenna is to receive radio signals from GPS satellites and convert them into electrical signals that can be processed by the receiver, thereby achieving positioning function. The working principle and structure of GPS antenna can be explained from the following aspects:

1. Principle of GPS antenna

Signal reception: GPS satellites continuously send microwave signals to the Earth, which contain information such as timestamps and satellite positions. The GPS antenna is responsible for receiving these signals and transmitting them to the GPS receiver for processing.

Polarization characteristics of signals: GPS signals are right-handed circularly polarized (RHCP) microwave signals, therefore, antennas need to be able to receive circularly polarized signals to ensure good reception capability in different directions. This polarization method enables effective reception of signals even after reflection or refraction.

Resonant frequency: GPS satellites mainly emit signals in two frequency bands, namely L1 frequency band (1575.42 MHz) and L2 frequency band (1227.60 MHz). The GPS antenna must be able to resonate at these frequencies to ensure effective reception of these signals.

Signal amplification: In order to enhance the strength of the received weak signal, GPS antennas typically integrate a low-noise amplifier (LNA). The function of LNA is to enhance signals and reduce losses caused by transmission lines.

2. Construction of GPS antenna

The design of GPS antennas mainly considers signal reception, directionality, and gain. The common GPS antenna structures include the following parts:

1) Radiation element

The radiating element is the core part of the antenna, responsible for receiving electromagnetic waves. Common types of radiation elements include:

Microstrip patch antenna: composed of metal patches, commonly used in portable GPS devices. It is a planar antenna typically placed on a ceramic substrate. The size and shape determine the resonant frequency of the antenna.

Spiral antenna: It forms circular polarization through a spiral structure and is commonly used in high gain applications, especially in devices that require high spatial signals.

Four arm spiral antenna: used in systems that require higher signal reception and gain, mainly for professional level GPS systems.

2) Floor (ground level)

The floor is an important component of an antenna, providing a reflective plane to increase the effectiveness of signal reception. It can affect the directionality and radiation mode of the antenna, usually made of conductive materials such as metals.

3) Filters and Low Noise Amplifier (LNA)

In order to improve the received signal strength, an LNA is usually integrated into the GPS antenna. The main function of LNA is to amplify weak signals received from satellites while reducing the impact of noise on the signal.

Filter: Helps filter out signals in non GPS frequency bands to avoid interference and ensure the purity of GPS signals.

4) Feedlines and connectors

Feedline: Transmits the signal received by the antenna to the GPS receiver. The transmission loss between the antenna and receiver should be minimized as much as possible to ensure signal quality.

Connector: The output end of the antenna is usually equipped with a standardized coaxial cable interface, such as SMA or MCX, for connecting to GPS receiving devices.

3. Gain and directivity of GPS antenna

Gain: Antenna gain refers to the ability of an antenna to amplify signals in a specific direction. Higher gain antennas (such as spiral antennas) can receive stronger signals in specific directions, while low gain antennas (such as omnidirectional antennas) can uniformly receive signals in all directions.

Directionality: Some GPS antennas have a certain degree of directionality, meaning they receive stronger signals in specific directions, while omnidirectional antennas can receive signals from all directions. Omnidirectional antennas are suitable for mobile devices, while directional antennas are suitable for fixed high-precision devices.

4. Common types of GPS antennas

Ceramic patch antenna: commonly used in devices with small size and high signal reception requirements, such as car navigation systems. Its gain and accuracy are relatively high, but its volume is large.

Spiral antenna: used in scenarios that require high signal gain, such as drones or professional level positioning equipment. This type of antenna can provide high sensitivity and a wide receiving range.

FPC antenna: suitable for portable devices such as smartphones and watches, characterized by small size, strong flexibility, and suitable for lightweight design.