- This design is a 4-layer board ofdimensions 50 mm x60 mm
- 2.4 GHz is the operating frequency
- Includes an air quality sensor, a light sensor, and a humidity sensor.AnilRaiker, PcB Design Head at sierra circuits said,"it is criticalto isolate these sensors from the rest ofthe circuitry.lfit isn't isolated corectly,it wilgive erroneous results, ln the desian, you can see L-shaped cutout regions which are used for isolation ofthe sensors from the other sianals"
- The desian has controled impedance traces as per the RE circuitry standards, Controled impedance is fundamentally matching the properties o
the substrate material with the dimension and position of the traces. - In this board,the stack-up design includes coplanar waveguides to achieve greater isolation.In a coplanar structure, the conductor is placed
between two ground planes. Via stitching is implemented in this case to connect the ground planes. - Ground plane stitching for antenna and 50 ohms Rf transmission line. Generally, Rf PcBs involve transmission line design such as microstrip andstripline, or coplanar waveguide.
- This desian required a thicker dielectric between trace and ground since the trace width is 30 mils.
- This board comprises mixed analog and diital designs, Hence, ground pours/copper pours are designed to eliminate noise.This can be seenin the image below.
- Fine pitch BGA 0.5 mm package with via-in-pad desian is included here.
Critical design considerations and solutions
When we asked about the critical design considerations for this design,Anil Raiker explained saying," RF circuitry routing is performed consideringthe width and length of traces of 50 ohms. Apart from this, the isolation of the sensor signal from the other RF signal is crucial to avert thenoise, in this board, the sensors are kept in the opposite direction and away from the antenna to mitigate the risk of interference.
Sensors implemented in this RF PCB
According to Anil,the sensors in this board were placed in such a way that they never picked up any noise.As mentioned earlier, there are threesensors in this board - air quality, light, and humidity sensors.
Air quality sensor
Air quality sensors are used to determine air quality and pollution levels. Some of the features are.
- Monitorindoor and outdoor air quality
- Measure the densities of particular airborne substances
- Detect hazardous particulate matter
Light sensor
A light sensor is a photo-electric device that converts light energy (series of photons) into electrical energy, Light sensors implemented in
- Smartphones
- Compact disc (CD) players
- Solar panels
- Automatic turn-on light system in vehicles
- Detection of sunlight in agriculture
Humidity sensor
Humidity sensors detect the moisture level and are the most sensitive components in a design. They are found in:
- Smartphones and tablets
- Weather forecasting
- Security systems
- Household appliances
- Medical instruments