Water Meter Antenna

The manufacturer of the water meter faced the challenge of optimising the performance and flexibility of their water meter. Our team developed an innovative antenna solution that achieved both objectives. We replaced the original electrical monopole antenna with a magnetic Antennity loop antenna. This change brought several advantages:

1. Improved range: The magnetic antenna shows better performance in environments with high dielectricity, as found in water meters.
2. Manufacturing flexibility: The new antenna design allows production of versions for 433 MHz and 868 MHz through simple component changes. This increases production flexibility and reduces inventory costs.
3. Optimised performance in encapsulated environments: The magnetic loop antenna is less susceptible to the influences of the casting material, leading to more consistent performance.

A crucial factor in antenna development for encapsulated devices like water meters is the relative permittivity (εr) of the surrounding material. This significantly influences the centre frequency and thus the antenna’s performance:

• Air: εr ≈ 1.00059
  In air, antennas work almost as in a vacuum. The wavelength and resonance frequency remain nearly unchanged.
• FR4 (typical PCB material): εr ≈ 4.4
  FR4 shortens the wavelength by about the factor √4.4 ≈ 2.1. An antenna on FR4 thus needs to be about half the size of a free-space antenna for the same frequency.
• Casting resin: εr ≈ 3-6 (depending on composition)
  Casting resins can shorten the wavelength by a factor of 1.7 to 2.4. This significantly shifts the antenna’s resonance frequency and must be considered during development.

This solution demonstrates how innovative antenna technology can significantly improve the performance and flexibility of IoT devices, even within the constraints of existing housings and circuit boards.