Superconductor Devices

Antennas provide link gain by delivering directivity. A highly directional antenna also
delivers selectivity by reducing the amount of visible noise seen by the antenna, which
means a high-gain antenna improves radio bandwidth quality. The cost is a larger (more
expensive) or more complex antenna (or both), which takes up more physical space on
the mast, and in the case of smart antennas, absorbs more processor bandwidth.

Filters can also be regarded as link gain products. By filtering out unwanted signal
energy, filters improve the quality of the wanted signal energy. Filters are used on the
transmit stages of a base station and handset to prevent interference to other adjacent
users, and on the receive side to improve receive sensitivity by delivering selectivity
(ratio of wanted to unwanted signal energy).
On the receive side, we are also having to capture and process a very low level signal
(a few picoWatts), so we need to find ways of optimizing the process of small signal
amplification—that is, optimizing the design and performance of the low-noise
amplifier (LNA).
In the following sections, we review how “signal steering” technologies and LNA
technologies can together deliver link gain an improvement in radio bandwidth quality. 314