Introduction

GPS – Introduction

KW Microwave Corporation has been designing and developing state-of-the-art components for GPS applications since the mid 1980s. The first application was a preamplifier, L1 & L2, still in use today, primarily on fighter aircraft pod mounted renage systems.

The use of GPS for military systems has been mandated by congress . The last of the GPS satellites has been launched and the system is fully operational. Initial developments by KWM were for the encoded Precise Positioning Service (PPS); but, KWM has since manufactured components for commercial applications using the GPS signal.

In many applications, the GPS receiver must be mounted remotely from the antenna and the amount of interference is much worse than many systems/receiver designers initially predicted. To accommodate the remote antenna and associated interference problems, specialized filters, low-noise amplifiers and preamplifiers are required.

Why should a preamplifier be used when a high quality , low-loss cable can be used? There are several reasons not to use the low-loss cable:

• Low-loss cables are very large, expensive and hard to handle.
• Low-loss cable degrades the noise figure by at least 0.5 to 1 dB for a 20 foot run.
• The extra weight of a low-loss cable becomes a concern on flight oriented applications.

Many receivers utilize inexpensive ceramic filters in their front ends . These filters typically have the first full spurious response as low as 2GHz and a multitude of responses between 2GHz and 18 GHz There are a variety of high power radar and other original signal sources in this band that could effectively block or even burn out a receiver without adequate filtering.

KW Microwaves GPS preamplifier and low-noise amplifiers are designed to filter out unintentional signals that are near the GPS band.