Frequency Converters, RF Amplifiers, Integrated Radio/Antennas, and Radio Modems

The network operator faces certain choices as to how to configure equipment used in a base
station or subscriber terminal.
The first choice in regard to a base station is whether the radio will be combined with the
antenna. Such combinations make for generally simpler installations and allow the installer to
run a data stream on ordinary data cable back to a router or switch. The drawback is that a limited
amount of functionality can be built into such a compact unit. If, on the other hand, a feed must be taken from the antenna to a transceiver, then the signal quality is more likely to be
impaired. In some cases where a radio/antenna combination is used, the installer may choose
to employ a downconverter that will shift the transmission to a lower frequency where it is less
subject to attenuation within the antenna cable.
The second choice is whether to use an outboard amplifier. Radio frequency amplifiers are
devices for boosting a signal that are sometimes added to transceivers in base stations. In the
United States they are forbidden for use in the unwired spectrum unless they have been specifically
designed around a given transceiver. Outboard amplifiers add to the cost of the system
but may be necessary in some instances where the transceiver simply lacks the power to reach
certain subscribers.
Subscriber premises equipment is generally simpler than that at the base station, but, in
some instances, the radio may also be part of the antenna. In other cases the antenna lead goes
to an outboard modem, often called a brick in the trade. The tendency today, especially in
indoor installations, is to place the modem and the antenna on a PCMCIA card that can be
installed directly in a computer’s card slot.