Reduction of Antenna Size for Tiny Devices

[mnieder]

I work on the design of self-sufficient wireless sensor nodes (edge length range of 5 .... 15mm). Now I'm looking for the minimal volume of the antenna (the small electronic layer is for this consideration negligible but keep in mind the rest of the volume is a metal block => shielding effects of the battery). Assuming constant receiver sensitivity (e.g. -100dbm), transmitting power (e.g. 0dbm) and a range (e.g. 1m): I know the effect of the carrier frequency wavelength -> higher frequencies allow smaller antennas but an increase from 2,4GHz to 24GHz reduces the range by a factor of 10 due to the higher damping in the air. After decision for the carrier frequency (e.g. 2,4GHz) and a antenna shape (e.g. Miniloop-Antenna) I look for an relationship between antenna efficiency and volume. Are there any analytical formulas for any antenna shapes, where I can calculate an efficiency via gain and volume?

 

[Kit-the-great]

Read any common antenna book (like C.A. Balanis Antenna Theory. Analysis and design.) You can find this formulas in most antennas book. For ex.: for aperture antennas (for uniform currents distribution) You can evaluate the beamwidth by this expression: W=l/D, where:
W - -3dB beamwidth (rad)
l - wavelength
D - aperture diameter

Best regards,
Kit-the-great

 

[microstrip_line]

It is said that adding an absorber in the antenna can shift the frequency lower and reduce the size in this way