This article presents a novel architecture of load-modulated balanced amplifier (LMBA) with a unique load-modulation characteristic different from any existing LMBAs and Doherty power amplifiers (DPAs), which is named pseudo-Doherty LMBA (PD-LMBA). Based on a special combination of control amplifier (carrier) and balanced amplifier (peaking) together with proper phase and amplitude controls, an optimal load-modulation behavior can be achieved for PD-LMBA, leading to maximized efficiency over extended power back-off range. More importantly, the efficiency optimization can be achieved with only a static setting of phase offset at a given frequency, which greatly simplifies the complexity for phase control. Furthermore, the cooperations of the carrier and peaking amplifiers in PD-LMBA are fully decoupled, thus lifting the fundamental bandwidth barrier imposed on the Doherty-based active load modulation. Upon theoretical proof of these discoveries, a wideband RF-input PD-LMBA is physically developed using the GaN technology for experimental demonstration. The prototype achieves a highly efficient performance from 1.5 to 2.7 GHz, e.g., 58%–72% of efficiency at 42.5-dBm peak power and 47%–58% at 10-dB output back-off (OBO). When stimulated by a 10-MHz long term evolution (LTE) signal with a 9.5-dB peak-to-average power ratio (PAPR), the developed PD-LMBA achieves an efficiency of 44%–53% over the entire bandwidth at an average output power of around 33 dBm.
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This content will become publicly available on December 5, 2024
A D-band frequency-doubling distributed amplifier thorugh monolithic integration of SiC SIW and GaN HEMTs
This is the first report of a distributed amplifier
(DA) realized through monolithic integration of transistors with
a substrate-integrated waveguide (SIW). The DA uses a steppedimpedance
microstrip line as the input divider like in
conventional DAs, but uses a low-loss, high-power-capacity SIW
as the output combiner. The input signal is distributed to four
GaN high-electron mobility transistors (HEMTs) evenly in
magnitude but with the phase successively delayed by 90° at the
fundamental frequency. The HEMTs are separated by a half
wavelength at the second harmonic frequency in the SIW, so
that their outputs are combined coherently at the SIW output.
To overcome the limited speed of the GaN HEMTs, they are
driven nonlinearly to generate second harmonics, and their
fundamental outputs are suppressed with the SIW acting as a
high-pass filter. The measured characteristics of the DA agree
with that simulated at the small-signal level, but exceeds that
simulated at the large-signal level. For example, under an input
of 68 GHz and 10 dBm, the output at 136 GHz is 24-dB above
the fundamental. Under an input of 68 GHz and 20 dBm, the
output at 136 GHz is 14 dBm, with a conversion loss of 6 dB and
a power consumption of 882 mW. This proof-of-principle
demonstration opens the path to improving the gain, power and
efficiency of DAs with higher-performance transistors and drive
circuits. Although the demonstration is through monolithic
integration, the approach is applicable to heterogeneous
integration with the SIW and transistors fabricated on separate
chips.
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- NSF-PAR ID:
- 10442666
- Date Published:
- Journal Name:
- Asia-Pacific Microw. Conf. (APMC), Taipei, Taiwan, Dec. 2023
- Page Range / eLocation ID:
- 1-3
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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