Comb Limiter-Comb Linear Amplifier Combiner

The use of wireless transmission has greatly grown over the last several years and is expected to increase at a phenomenal rate. One problem resulting from this growth has been how to increase the number of transmitters and radios in limited spaces without negatively impacting the transmission and receiving functions. The use of frequency-hopping radios is one way to increase capacity; however, in the military environment, nonlinear effects such as intermodulation can severely limit the number of frequency-hopping Single Channel Ground and Airborne Radio System (SINCGARS) radios that can be successfully collocated.

SENTEL Corporation has worked closely with the Department of the Navy to develop approaches to these problems in the shipboard environment. SENTEL and the Navy’s Space and Warfare Systems Command (SPAWAR) co-developed a Comb Limiter Combiner (CLIC) for connecting one or more receivers to a single antenna. More particularly, CLIC mitigates intermodulation effects in receivers for wideband transmission. SENTEL then developed a Comb Linear Amplifier Combiner (CLAC), which allows one or more transmitters to transmit through one transmit antenna. An integrated CLIC-CLAC application greatly increases the number of frequency-hopping SINCGARS radios that can be successfully collocated, while minimizing the intermodulation effects.

CLIC-CLAC solves collocation problems onboard Navy ships. The Navy has a requirement (on all amphibious transport and command ships) to transmit using several (up to 16) SINCGARS radios on a single ship without interference. By using CLIC-CLAC, it is possible to allow up to 20 SINCGARS radios to operate simultaneously in frequency-hopping mode without interference. Additionally, the Navy is interested in minimizing the number of antennas on the ship superstructures. CLIC-CLAC will allow the Navy to reduce the number of antennas required from 16 to two. Initially, the prototype CLIC-CLAC was successfully tested in the SPAWAR Communications Lab in November 2001.

The Navy and SENTEL are also addressing Ultra High Frequency (UHF) shipboard problems. Amphibious combatant ships can have 20 HAVEQUICK radios and up to four Enhanced Position Location Reporting Systems (EPLRSs). With an UHF-capable CLIC-CLAC, collocation issues will be mitigated, and the requirement for over 20 antennas will be reduced to no more than four antennas. This significantly reduces topside weight and radar cross-section.