Waveform Optimization Using RF Pulse Signal on Voltage-Doubler Broadband Rectenna

In this article, the DC-output improvement of a broadband rectenna has been demonstrated using pulse signal. The pulse waveform is optimized by varying its duty cycle as well as its modulation frequency. The rectenna operating from 1.6 to 2.8 GHz is characterized experimentally with low/medium RF power and different loads. The optimized waveform has a duty cycle that varies between 1 and 20 % for a modulation frequency between 1 and 6 MHz. The results show that the DC voltage and the efficiency are improved over the frequency band of interest, particularly for frequencies below 1.8 GHz and those above 2.6 GHz. The DC-output improvement, compared to the 1-tone signal, is characterized by the calculation of voltage/efficiency gain. High gain values are experimentally obtained: close to 14 dB at 1.675 GHz and -20 dBm RF power. The voltage gain is greater than 0 dB for low (3 kΩ) and high (100 kΩ) loads. At 2.4 GHz and for a low load of 3 kΩ, 4-dB gain is measured at -30 dBm. For a load of 100 kΩ, the efficiency goes from 8.3 % for the 1-tone to about 74.7 % for the optimized waveform, at -15 dBm RF power level.