GNSS passive ceramic antenna

　　1. Core Definition and Features

　　GNSS Passive Ceramic Antenna:

　　A passive GNSS antenna based on a ceramic dielectric substrate, which achieves miniaturization, wideband and high sensitivity through the dielectric constant and structural design of ceramic materials, without the need for integrated active circuits (such as LNA).

　　Key Features:

　　Miniaturization: The high dielectric constant of ceramic substrates (such as LTCC, microwave ceramics) allows the antenna size to be smaller (such as 5×5×3mm³).

　　Low loss: Ceramic materials have low dielectric loss (<0.01), suitable for high-frequency signal transmission (L1/L5/Galileo E1/E5).

　　Wideband support: Covers multiple GNSS frequency bands (such as 1575.42MHz (L1), 1176.45MHz (L5)).

　　Low cost: No active devices are required, simplifying the manufacturing process.

　　2. Working Principle

　　Antenna Structure:

　　Patch Antenna: The most common form, fed by microstrip line or coplanar waveguide (CPW), radiating electromagnetic waves.

　　Dipole antenna: Radiates signals using symmetrical structure, suitable for wide-band design.

　　Matching circuit:

　　Integrated matching network (such as π-type network) optimizes impedance matching (50Ω) between antenna and GNSS receiver.

　　Signal flow:

　　GNSS satellite signal → passive antenna reception → matching circuit transmission → RF front-end demodulation → positioning algorithm processing.

　　3. Design points

　　3.1 Material selection

　　Ceramic substrate:

　　LTCC (low temperature co-fired ceramic): multi-layer integration, supports high frequency (>5GHz) and complex circuits.

　　Microwave ceramics (such as AlN, SiC): high thermal conductivity, suitable for high temperature environment (such as vehicle-mounted).

　　Glass ceramics: low cost, suitable for mass production of consumer electronics.

　　3.2 Antenna structure optimization

　　Patch antenna design:

　　Rectangular/circular patch: balance radiation efficiency and size (for example, 2.5×2.5mm² patch is commonly used in L1 band).

　　Multi-feed point design: supports multiple frequency bands (such as L1 + L5 dual-band).

　　Grounding design:

　　Microstrip grounding: reduce size, but avoid parasitic capacitance.

　　Via grounding: improve high-frequency stability (such as >2GHz).

　　3.3 Impedance matching

　　Matching network:

　　Use LC series/parallel circuit or distributed matching structure.

　　Simulation tools (such as HFSS) optimize parameters (such as inductance value, capacitance value).

　　3.4 Multi-band compatibility

　　Band isolation:

　　Reduce coupling between different bands through antenna spacing or metal partitions.

　　Harmonic suppression: avoid high-frequency harmonics interfering with low-frequency reception (such as L5 to L1 second harmonic).

　　4. Typical application scenarios

　　Consumer electronics: smart phones, smart watches, car navigation.

　　Internet of Things devices: shared bicycle electronic fence, drone positioning and tracking.

　　Industrial measurement: geological exploration equipment, agricultural machinery automatic navigation.

　　Wearable devices: AR glasses, health monitoring bracelets.

　　5. Testing and verification

　　Key indicator test:

　　Gain: ≥2dBi (typical value).

　　VSWR: <2.0 (ensuring effective signal transmission).

　　Return loss: ≤-10dB.

　　Sensitivity: ≥-140dBm@L1 band (open environment).

　　Simulation tools:

　　HFSS: optimize antenna radiation pattern and matching network.

　　ADS: verify multi-band collaborative performance.