GPS – Introduction
GLOBAL POSITION SATELLITE (GPS) PRODUCTS
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.
PREAMPLIFER VS. LOW-LOSS CABLE
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.
INTERFERENCE AND JAMMING
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.
HIGH POWER PROTECTION
KW Microwave has designed GPS low-noise amplifiers and preamplifiers with special circuitry that inhibits and protects both the low-noise amplifier, preamplifier and receiver from damage due to high power inband signals.
KWMs GPS engineers are capable of designing preamplifiers and low-noise amplifiers with gain from 10dB to 40dB. As will be noted when reviewing KWMs part number GPS-1-14009 later in this section, KWM engineers have developed a GPS Preamplifier which handles 313 watts of in-band pulsed power and up to 1 Kilowatt out-of-band.
KWM GPS engineers have experience in the design of the entire GPS receiver system and can apply that knowledge in product design.