As described in Chapter 6, an inverter circuit with lumped elements is always applied for coupling wireless power transfer (WPT) because its frequency is usually in the kHz-MHz range and its wavelength is very low compared to the circuit size. As described in Chapters 7 and 8, radio waves with frequencies in the GHz range that are below tens of cm^-1 are used for WPT to extend the WPT distance. At frequencies above 1 GHz, the size of the circuit and the wavelength are essentially the same; therefore, distributed constant lines are often applied to the circuit at frequencies greater than GHz instead of the lumped elements (Figure 9.1). We must consider a phase and an amplitude at each point in the circuit and the characteristic impedance of the circuit given by the amplitude and the phase of the voltage and current in the circuit. We should additionally consider parasitic capacitances and inductances at GHz frequencies. While the inverter circuits and design method described in Chapter 6 can be applied for WPT via radio waves, other transmitter/receiver circuits and design methods with the distributed constant lines are more suited for WPT via radio waves and should be used instead of the circuits described in Chapter 6.

Chapter Contents:

• 9.1 Introduction
• 9.2 RF transmitter
• 9.2.1 RF amplifier with semiconductor
• 9.2.2 Vacuum tube type microwave generator/amplifier
• 9.3 RF rectifier
• 9.3.1 RF rectifier with semiconductor
• 9.3.2 Vacuum tube-type microwave rectifier
• 9.4 RF amplifier/rectifier with semiconductor
• References

Inspec keywords: inductive power transmission; invertors; radiowaves; radiofrequency power transmission

Other keywords: transmitter-rectifier technologies; lumped elements; inverter circuit; parasitic capacitances; parasitic inductances; characteristic impedance; distributed constant lines; radio waves; transmitter-receiver circuits; wireless power transfer coupling; WPT; design method

Subjects: Wireless power transmission; DC-AC power convertors (invertors)