In this paper, a microstrip lowpass filter with wide stopband and sharp roll-off is presented. The proposed filter consists of a modified radial stub resonator which is cascaded by four suppressing cells. To reduce the overall size, the transmission lines are folded. The cut-off frequency of the proposed filter is 1.19 GHz. The transition band is approximately 0.2 GHz from 1.19 to 1.39 GHz with corresponding attenuation levels of 3–20 dB. The stopband is from 1.39 to 19 GHz with attenuation level of <20 dB. The insertion loss and return loss in the passband from DC to 0.8 GHz are better than 0.26 and 14 dB, respectively. The proposed filter is fabricated and measured. The simulated and measured results are in good agreement.

In this paper, a Class-E inverter and a thermal compensation circuit for wireless power transmission in biomedical implants are designed, simulated, and fabricated. In the analysis of the Class-E inverter, the voltage-dependent non-linearities of Cds, Cgd, and RON as well as temperature-dependent non-linearity of RON of the transistor are considered simultaneously. Close agreement of theoretical, simulated and experimental results confirmed the validity of the proposed approach in taking into account these nonlinear effects. The paper investigated the effect of temperature variations on the characteristics of the inverter. Since both the output power and efficiency decrease with increasing temperature, a compensation circuit is proposed to keep them constant within a wide temperature range to enable its application as a reliable power source for medical implants in harsh environments. Simulations were performed and the results confirmed that the compensator enables significant improvements by maintaining the power and efficiency almost constant (8.46 ± 0.14 W and 90.4 ± 0.2%) within the temperature range of − 60 to 100 °C. Measurements performed at 25 °C and 80 °C with and without the compensation circuit were in good agreement with the theoretical and simulation results. The obtained measured output power and efficiency at 25 °C are equal to 7.42 W and 89.9%.