Fig 1.
Fig 2.
The principles by which waveforms are transformed by harmonics.
The VDS is formed by the original signal and the odd harmonic, and the IDS is formed by the original signal and the even harmonic.
Fig 3.
Typical network roles for a class F amplifier.
Fig 4.
The ideal schematic diagram that is to calculate the drain efficiency of the two-stage class F amplifier which controlled only third harmonic.
Fig 5.
Designed two-stage high efficiency and high voltage class F amplifier schematic diagram.
Table 1.
Numerical values of circuit elements in Fig 5.
Fig 6.
Large-signal LDMOSFET equivalent circuit provided by STMicroelectronics.
Fig 7.
Simulation data of high-efficiency and high-voltage class F amplifier.
Red and blue lines represent the drain voltage and drain current, respectively. The voltage and current waveform data from (a) the first stage and (b) the second stage.
Fig 8.
Simulation data of high-efficiency and high-voltage class F amplifier.
S parameter used for impedance matching (a) S11, (b) S22.
Fig 9.
Block diagram showing amplifier performance measurement.
Fig 10.
(a) Measurement environment for manufactured class F amplifier performance and (b) zoomed-in manufactured class F amplifier.
Fig 11.
Ultrasonic pulse echo measurement process.
Fig 12.
Limiter and expander schematic used in the experiment.
(a) Expander (b) limiter circuits.
Fig 13.
Discharged signal and ultrasonic echo signal transmitted and received by a high-efficiency and high-voltage class F amplifier and 25 MHz transducers.
Fig 14.
Curves showing variation of POUT and calculated PAE and THD values obtained from high-efficiency and high-voltage class F amplifier with a 7.5 dBm input power according to frequency.
(a) PAE vs. Frequency, (b) THD vs. Frequency, (c) POUT vs. Frequency.
Fig 15.
The first echo signal transmitted and received by a high-efficiency and high-voltage class F amplifier and 25-MHz transducers.
Fig 16.
FFT spectrum data transmitted and received by a high-efficiency and high-voltage class F amplifier and 25-MHz transducers.
(a) FFT spectrum data for fundamental signal, second harmonic and third harmonic (b) FFT spectrum data enlarged to show bandwidth.
Table 2.
Ultrasonic echo signal harmonics.
Fig 17.
(a) Measured Pout and (b) calculated PAE and gain graphs from high-efficiency and high-voltage class F amplifier with an input frequency of 25 MHz.
Table 3.
Summarized performances of class AB amplifier [48], class C amplifier [49], class F amplifier [50,51], and our developed class F amplifier.