Power Combiner 195
detector schematic shown in Figure 7.4 5. As the output node Vo1 is a high
impedance point, it is sensitive to proces s variatio n. As a result, the transistor
biasing (V
bn
) needs to be adjusted to tune the Vo1 level back, which shifts the
power detection range. This problem can be easily fixed by adding an op-amp
after the originally designed power detector circuit to fix the output voltage
level, as shown in Figure 7 .45.
7.5 Conclusion
In this chapter, a 2D distributed power combining network is proposed by
replacing the bulky RH T-line in traditional power combiners with compact
metamaterial-typed CRLH T-line. Compared with the RH T- line , CRLH T-
line shows unique features such as nonlinear phase-frequency dependence and
zero-phase-shift capability, and thus can replace bulky RH T-line with the
same functionality but much more compact area. By periodically loading
transistors in a pro posed 2D active in-phase CRLH T-line network, transis-
tor outputs can be in-phase co mbined both in series and in parallel within
a compact area in a dis tributed manner, thus achieving high output power,
high output power density and wide-band simultaneously. Three 60GHz PA
prototypes with single-ended 2× 2 powe r combining network a nd differential
2×4 and 4×4 power combining network s are implemented in 65nm CMOS
technology. The 1
st
PA prototype with single-ended 2×2 powe r combining
shows 8.3dB gain, 7.1% PAE, and 9.7dBm OP
1dB
with 16GHz bandwidth
(44 to 60GHz) and area of 0.39mm
2
. This work is further improved to have a
differential topology with compact transformer matching. The 2
nd
PA proto-
type with differential 2×4 power combining shows 13.2 dB gain, 8.7% PAE,
20GHz bandwidth (53 to 73 GHz) and 13 dBm OP
1dB
with 74.5 mw/mm
2
output power density, realizing s tate-of-the-art power performance and wide
bandwidth simultaneously. The power performance is further improved by the
3
rd
PA prototype with differ ential 4×4 power combining, which shows 17.5-
dB gain, peak PAE of 11.3%, 8.8-GHz bandwidth (54 to 62.8 GHz), and 16.6-
dBm OP
1rB
with 95.2-mw/mm
2
output power density, demonstrating the top
power performance in literature. All three PA prototypes show sta te-of-the-
art performance, demonstrating the benefit of the pro posed power combining
network for effective short-range communication.
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