PCB antenna (printed circuit board antenna)

　　Analysis of the core differences between PCB antennas and external antennas: a comprehensive comparison from structure to application

　　1. Definition and essential difference: integrated VS independent design logic

　　PCB antenna (printed circuit board antenna)

　　Essence: an antenna formed directly on a PCB circuit board by etching copper foil, using the circuit board medium (such as FR4, Rogers) as a radiation carrier.

　　Morphology: common types include monopole, dipole, slot antenna, patch antenna and planar inverted F antenna (PIFA).

　　Derivative type: flexible PCB antenna (FPC antenna), based on flexible circuit board design, suitable for curved or foldable devices.

　　External antenna

　　Essence: a physical antenna component independent of the device motherboard, connected to the device through an interface (such as IPEX, SMA).

　　Morphology: including whip antenna (Whip Antenna), rubber duck antenna (Rubber Duck Antenna), helical antenna (Helical Antenna), etc., divided into omnidirectional or directional radiation types.

　　II. Core difference comparison: from technical parameters to actual performance

　　1. Structural design and integration

　　PCB antenna

　　Advantages:

　　▶ Highly integrated in the circuit board, no additional assembly required, saving space (thickness is usually < 1mm);

　　▶ Low cost, can be formed in one go through the PCB process, suitable for mass production (such as 2.4GHz WiFi/Bluetooth module).

　　Limitations:

　　▶ Radiation efficiency is affected by PCB material (dielectric constant) and ground layer, and is susceptible to electromagnetic interference from the motherboard;

　　▶ Performance depends on PCB layout, and debugging is complex (impedance matching and ground plane optimization are required).

　　External antenna

　　Advantages:

　　▶ Independent structure, which can optimize the design of radiation units and achieve higher gain (such as above 5dBi, PCB antenna is usually ≤3dBi);

　　▶ Physically isolate motherboard interference, suitable for high-sensitivity scenarios (such as long-distance communication).

　　Limitations:

　　▶ Additional space is required for installation, which increases the size of the device (e.g. the whip antenna can be more than 10cm long);

　　▶ High cost, requires welding interface (e.g. IPEX), and increases assembly complexity.

　　2. Performance parameter comparison

　　Gain and radiation efficiency

　　PCB antenna: Gain is usually 0-3dBi, efficiency is about 50%-70% (affected by PCB material loss);

　　External antenna: Omnidirectional antenna gain is 2-5dBi, directional antenna can reach 8-16dBi, efficiency is 70%-90% (e.g. spiral antenna).

　　Bandwidth and frequency band adaptability

　　PCB antenna: mainly narrowband design (e.g. 2.4GHz single band), multi-band requires complex structure;

　　External antenna: can cover wide frequency band (e.g. 2.4/5GHz dual band), support millimeter wave frequency band (e.g. 5G NR).

　　Anti-interference ability

　　PCB antenna: susceptible to interference from motherboard chips and power circuits, requires strict grounding design;

　　External antenna: physically isolate interference sources, and shielding design can improve anti-interference.

　　3. Differences in application scenarios

　　PCB antenna applicable scenarios

　　▶ Consumer electronics (mobile phones, smart watches): pursue ultra-thin design, and do not require high communication distance;

　　▶ Short-range IoT devices (ZigBee, BLE): transmission distance < 100 meters, power consumption sensitive scenarios;

　　▶ Integrated module (WiFi module): complete antenna debugging before leaving the factory to reduce the difficulty of terminal manufacturers' development.

　　External antenna applicable scenarios

　　▶ Industrial equipment (drones, remote sensors): need to cover a distance of more than 1 km;

　　▶ In-vehicle communications (GPS, 4G/5G): need high gain to resist shielding (such as roof antennas);

　　▶ Professional equipment (base stations, microwave backhaul): require high EIRP (effective omnidirectional radiated power), such as:

　　EIRP = transmit power (Pt) × antenna gain (Gt), external antennas can increase transmission distance through high gain.

　　III. Analysis of key technical terms: core indicators affecting performance

　　Gain

　　Definition: The ratio of the radiated power of an antenna in a specific direction to that of an ideal point source antenna, in dBi (relative to an omnidirectional antenna) or dBd (relative to a half-wave dipole).

　　Example: 0dBd antenna converted to dBi is 2.15dBi, and the external antenna gain is usually 2-10dBi higher than the PCB antenna.

　　Efficiency

　　The ratio of radiated power to input power. PCB antennas have a lower efficiency (50-70%) due to dielectric loss, while external antennas can reach 70-90%.

　　EIRP (Effective Isotropic Radiated Power)

　　Formula: EIRP = Pt (transmitted power) × Gt (antenna gain), which reflects the actual radiation capability of the antenna.

　　Example: 10dBm transmit power with 5dBi external antenna, EIRP=15dBm; if 2dBi PCB antenna is used, EIRP=12dBm, and the transmission distance is shortened by about 30%.

　　IV. Selection Decision Guide: How to choose an antenna according to needs?

　　Space Limitation

　　Ultra-thin devices (such as smart bracelets): PCB/FPC antennas are preferred;

　　Device with reserved external interfaces (such as routers): select external antennas to expand performance.

　　Communication distance

　　Short distance (<100 meters): PCB antenna is enough;

　　Medium and long distance (100 meters - 1 km): external omnidirectional antenna (such as 5dBi whip antenna);

　　Long distance (>1 km): external directional antenna (such as Yagi antenna).

　　Environmental complexity

　　Interference-intensive scenarios (such as urban buildings): external antenna with anti-interference design;

　　Simple environment (such as open areas): PCB antenna can meet basic needs.

　　V. Conclusion: Trade-offs and integration trends of technical routes

　　PCB antennas win with integration and low cost, suitable for consumer and short-distance scenarios; external antennas dominate the industrial and professional fields with high gain and anti-interference. It is worth noting that the hybrid solutions (such as PCB antenna + external amplifier) that have emerged in recent years are gradually balancing performance and cost, while metamaterials (Metamaterial) and AI optimized layout technology are also driving PCB antennas towards high performance. In the future, the boundary between the two may be further blurred due to breakthroughs in flexible electronics and miniaturization technology.