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Lna Integrates Fast Shutdown Function, Chin-Leong Lim Nov 2014

Lna Integrates Fast Shutdown Function, Chin-Leong Lim

Chin-Leong Lim

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 …


Low Loss Configuration For Integrated Pin-Schottky Limiters, Chin-Leong Lim Jul 2014

Low Loss Configuration For Integrated Pin-Schottky Limiters, Chin-Leong Lim

Chin-Leong Lim

Compared to the PIN diode limiter, the Schottky-PIN limiter improves receiver protection, but has a higher insertion loss. Low cost, plastic packaged diodes can further worsen the loss. Diode stacking, mesa diode construction, and isolating the Schottky diode with a high-impedance quarter wave line or a directional coupler can reduce loss, but detrimentally raises the limiting threshold and/or adds bulk or cost. The PIN-Schottky limiter’s insertion loss can be improved by integrating the diodes’ parasitic capacitances into a low pass ladder network, but this solution requires the PIN diode to have two anode connections. Recently, the PIN-Schottky limiter was integrated …


Compact Lna Drives 2.5-Ghz Base Stations, Chin-Leong Lim Dec 2013

Compact Lna Drives 2.5-Ghz Base Stations, Chin-Leong Lim

Chin-Leong Lim

Cellular basestations' low noise amplifiers (LNA) must have input impedances that are closely matched to the antennas. Unfortunately, the amplifier devices cannot be conjugate matched without sacrificing their noise performances. Current solutions such as the isolator and the balanced LNA can satisfactorily solve the matching problem but at the expense of increased cost, weight and size. On the other hand, the confined space atop cellular towers makes the current solutions unattractive. To shrink the balanced LNA for cellular infrastructure service, we pair a highly integrated dual-amplifier MMIC with miniature multilayer couplers. This MMIC also has the distinction of being the …