THE SQUARE KILOMETER ARRAY (SKA) radio synthesis telescope is estimated to require millions of receivers. To keep receiver cost down, CMOS technology is being looked at as an option. With recent improvements in CMOS transistors, this technology can even achieve the low noise figures needed in radio astronomy. At the University of Calgary's (Calgary, Canada) Department of Electrical and Computer Engineering, Leonid Belostotski and James W. Haslett have achieved sub-0.35-dB noise figures. The researchers assert that those figures can be further improved by designing a low-noise amplifier (LNA) for the telescope antenna with non-50-O port impedance. Power-constrained optimization should be used as well.
Essentially, the noise-figure optimization procedure determines the signal-source resistance that results in the reduced noise figure. The LNA, which is designed in 90-nm bulk CMOS, achieves a sub-0.2-dB noise figure from 800 to 1400 MHz. It also flaunts return loss of more than 11 dB, gain of more than 17 dB driven into a 50-O load, and an output 1-dB compression point of +2 dBm. While consuming 43 mA from a 1-V supply, the output third-order intercept point is +12 dBm. The output second-order intercept point is +22 dBm.
To achieve the best noise figure, an SKA LNA optimization must be done in conjunction with the design of the circuit board on which the LNA will be mounted. In this LNA implementation, the load choke inductor and source inductor are integrated. See "Sub-0.2 dB Noise Figure Wideband Room-Temperature CMOS LNA With Non-50-O Signal Source Impedance," IEEE Journal of Solid-State Circuits, Nov. 2007, p. 2492.
