New-Tech Europe | Q2 2020 | Digital Edition

The RF energy harvesting system consists of an antenna, a Rectifying circuit and a rechargeable battery. We can calculate the energy harvesting link budget by using equations 1 to 4.

Free Space Loss (Lp) represents propagation loss in free space. Losses due to attenuation in atmosphere, La, should also be accounted for in the transmission equation. Where, . The received

Figure 2: A wideband 2GHz to 7.8GHz energy harvesting Wearable System

power may be given as:

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Pt is the transmitting antenna power. Lt is the Loss between power source and the antenna. EIRP is the Effective Isotropic Radiated Power. The received power Pr in dBm is given in equation 4. The received power Pr is commonly referred to as “Carrier Power”.

Losses due to polarization mismatch, Lpol, should also be accounted. Losses associates with receiving antenna, Lra, and with the receiver, Lr, cannot be neglected in computation of transmission budget. Losses associates with the transmitting antenna as written as, Lta.

Where, Pt =Pout /Lt. EIRP = Pt Gt

Figure 3: A wideband 2GHz to 7.8GHz notch, Computed S11

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