Load‐modulation technique without using quarter‐wavelength transmission line. Issue 11 (12th June 2020)

• Record Type: Journal Article
• Authors: Abdulkhaleq, Ahmed M.; Yahya, Maan A.; Parchin, Naser O.; Al‐Yasir, Yasir; Sajedin, Maryam; Elfergani, Issa; McEwan, Neil J.; Abd‐Alhameed, Raed A.; Rayit, Ashwain; Rodriguez, Jonathan
• Is Part Of: IET microwaves, antennas & propagation. Volume 14:Issue 11(2020)
• Page Start: 1209
• Page End: 1215
• Publication Date: 2020-06-12
• Subjects: III‐V semiconductors -- gallium compounds -- integrated circuit design -- integrated circuit testing -- circuit simulation -- MMIC power amplifiers -- modulation; modulated signals -- adjacent channel power ratio -- amplifier linearity -- active load‐modulation technique -- input signal level -- peaking amplifier -- normalised impedance -- symmetrical gallium nitride transistors -- output back‐off peak efficiency -- peak‐average‐power ratio -- circuit design -- noise figure 31.0 dB to 35.5 dB -- power 6.0 W -- power 12.0 W -- noise figure 6.0 dB -- frequency 400.0 MHz -- frequency 3.6 GHz -- noise figure 20.0 dB -- GaN; Microwaves -- Periodicals; Microwave antennas -- Periodicals; Antennas (Electronics) -- Periodicals; Radio wave propagation -- Periodicals; Microwave communication systems -- Periodicals; 621.381305
• DOI: 10.1049/iet-map.2019.0957
• Languages: English
• ISSNs: 1751-8725

Abstract

Abstract : A proposed method for achieving active load‐modulation technique without using a quarter‐wavelength transmission line is discussed and evaluated. The theoretical analysis shows that the active load‐modulation can be achieved without using a quarter‐wavelength line, where the main amplifier sees a low impedance when the input signal level is low, and this impedance increases in proportion to the amount of current contributed from the peaking amplifier. The peaking amplifier sees an impedance decreasing from infinity to the normalized impedance. To validate the method, a circuit was designed, simulated and fabricated using two symmetrical gallium nitride (GaN) transistors (6 W) to achieve a peak power of 12 W and 6 dB output back‐off efficiency. The design operates with 400 MHz bandwidth at 3.6 GHz and showed an average efficiency of 50% at 6 dB back‐off and an efficiency of 75% at peak power. The designed circuit was tested with CW and modulated signals, the amplifier showed an Adjacent Channel Power Ratio (ACPR) of 31–35.5 dB when tested with a wideband code division multiple access signal of 6 dB peak‐average‐power ratio (PAPR) at 35.5 dBm average power. Additional 20 dB of linearity improvement was achieved after adding a lineariser.