To minimize dead time in time domain duplex (TDD) transceiver, reception should ideally commence as soon as transmission ends. However, the low noise amplifier (LNA), which is typically shutdown during transmission to prevent device damage and receiver overload, can exhibit a turn-on delay. In older implementations, the shutdown function is external to the LNA device. So, one way to reduce part count and to miniaturize this class of LNA is to integrate the LNA and shutdown function in a microwave monolithic integrated circuit (MMIC). The integration also allows the shutdown circuit to be connected to the LNA at an optimum position for switching speed. This paper reports the achieved switching speed and compares it with other similar MMICs.
The LNA turns on in 0.05 uS (8x faster than the previous best) and turns off in 0.02 uS (15x faster than the previous best). In conclusion, the integration of the shutdown function not only beneficially reduces LNA part count and size, but avoids external switching’s attendant high current and slower speed. This work has the potential to significantly cut the ‘guard-time’ required by TDD LNAs.
- low noise amplifier with integrated shutdown,
- reduce dead-time in time domain duplex,
- fast switching.
Available at: http://works.bepress.com/chin-leong_lim/31/