L Band High Pass Filters And Their Various Applications

The world of radio frequencies and signals may be a bit hard to digest, or understand, especially for laymen (or those who have little or nil knowledge of electronics). However, we should all be thankful that the various radiofrequency signals work effectively, and are not bumped off, or trampled, by each other, because of the effective job done by electronic RF filters – whether they’re high pass, low pass, bandpass and others. In this segment, we shall discuss the general specifications, and benefits, of using L-band high pass filters.

How High Pass Filters Work

Whether it’s any of the radio-frequency bands in the IEEE, or the Institute of Electronics and Electrical Engineers, or the ITU (International Telecommunication Union), electronic radiofrequency filters are always busy at work, and that of course includes L-band high pass filters.

High pass filters are electronic devices which “pass” or allow the entry of signals with a frequency higher than certain cut-off frequencies, while at the same time “attenuating” or isolating signals with frequencies that are lower that the cut-off frequency.

Some high pass filters are built using a resistor and capacitor, wherein the high pass filter passes higher frequencies and attenuates lower frequencies. The filter’s capacitor passes higher frequencies, causing the output voltage to fluctuate further. The lower frequencies are then blocked, and there’s reduced current across the resistor, which keeps the output voltage closer to the ground.

The L-Band’s Wide Range Of Uses

The IEEE defines the L-band as the 1 to 3 GHz range of the radio spectrum, and it plays host to a wide array of very important functions and applications. In mobile communications, the European Conference of Postal and Telecommunications Administrations has already allowed individual countries to adopt the L-band for the use in terrestrial mobile/fixed communications supplemental downlink.

This means that LTE (Long Term Evolution), UMTS/HSDPA base stations can use the L-band to offer additional bandwidth for smart phone and mobile device communication/data transmissions.

The L-band is also used for satellite navigation, especially by GPS or Global Positioning System carriers, and is centered at 1176.45 MHz (L5), 1227.60 MHz (L20, 1381 MHz (L3) and 157 MHz (L1) frequencies. The Galileo Navigation System and the GLONASS system also utilizes the L-band in the same way as GPS.
The L-band is also the playground of GSM mobile phones, which operate at 800-900 and 1800-1900 MHz, along with Iridium, Inmarsat and Thuraya satellite phones.

The 1090 MHz is also used by aircrafts around the world to communicate or relay their position information to the ground, as well as between aircraft for improved traffic information and avoidance.

L-band high pass filters also help regulate and traffic in amateur radio operations,  as well as in digital audio broadcasting, radio astronomy and even weather tracking and telemetry applications. In amateur radio, the widely-used L-band frequencies range from 1240 to 1300 MHz, while amateur satellite uplinks are allowed in the 1260 to 1270 MHz range, and is known as the 23-centimeter band by radio amateurs.