A Ka-Band InP HBT MMIC Power Amplifier With 19.8:1 IP3/Pdc LFOM at 48 GHz

This article describes the design and measured performance of a linear efficient Ka -band InP DHBT PA with an IP3/
$\text{P}_{\mathrm {dc}}$
linearity figure of merit (LFOM) of 19.8:1 at 48 GHz and 14.1:1 at 40 GHz. The MMIC PA is based on an InP DHBT technology with peak
${f}_{AT}$
and
${f}_{\mathrm{ max}}$
of
$>$
300 and
$>$
600 GHz, respectively, and achieves among the best LFOM at the Ka -band above 40 GHz from an MMIC-matched amplifier. The amplifier is a single-stage four-way combined design that was optimized for a combination of power and PAE at < 2-dB compression. The linear
${P}_{\mathrm{ 1\,dB}}$
is 21.2 dBm with a PAE of 28.3% and a corresponding IP3 of 36.1 dBm. A remarkable IP3-
${P}_{\mathrm {1\,dB}}\,\,=$
14.9 dB is obtained which is significantly higher than the 10 dB rule of thumb for semiconductors. At 48 GHz, a peak IP3 of 36.6 dBm and LFOM of 19.8:1 is achieved which is twice better than the low microwave frequency rule-of-thumb of 10:1 for LFOM. Under a 200-MHz QPSK modulation, linear PAEs of 17.4%–19.5% for 5% EVM across a 40–44-GHz band were achieved. This work demonstrates among the highest IP3/
$\text{P}_{\mathrm {dc}}$
LFOM and EVM linear PAE reported for an MMIC above 40 GHz.