Abstract: A radio frequency (RF) horn can include an interior surface with an inner geometry comprising irregular, aperiodic corrugations and/or undulations. The pattern of the inner geometry can excite higher order modes simultaneously in two RF signals each at a different frequency that combine with fundamental modes of the signals to produce substantially Gaussian profiles of the two signals at the output aperture of the horn. Even though the signals are at different frequencies, the illumination pattern of both signals on a reflector antenna at which the horn is directed can be substantially the same.

Abstract: A radio frequency (RF) coaxial horn can comprise an inner RF horn disposed inside a larger outer RF horn. An interior surface of the inner horn can comprise a pattern of irregular, aperiodic features that excite modes in first and second RF signals each at a different frequencies that produce substantially Gaussian beam profiles of the first and second signals at the output aperture of the inner horn. The waists of the beam profiles of the first and second signals can be outside the inner horn but inside the outer horn. An interior surface of the outer horn and/or an outer surface of the inner horn can similarly excite modes in a third RF signal at a frequency different than the first and second RF signals to produce a substantially Gaussian beam profile of the third signal at the output aperture of the outer horn. The waist of the beam profile of the third signal can be aligned with the waists of the beam profiles of the first and second signals.

Abstract: A compact tracking coupler includes a plurality of ridged waveguides arranged circumferentially around a circular waveguide wherein long sides of the ridged waveguides extend circumferentially and short sides of the ridged waveguides extend radially relative to the circular waveguide. The compact tracking coupler can be especially useful in a multi-band antenna feed.

Abstract: Wireless terminals, systems, and methods use interlaced diplexers. A first diplexer can provide a first pair of bands separated by a first separation band, and a second diplexer can provide a second pair of bands separated by a second separation band. The first separation band and the second separation band can overlap. Transceivers (comprising transmitters and receivers) can be coupled to the diplexers to provide frequency-division duplex communications using one or both of the pairs of bands.

Abstract: A system for pre-concentrating analytes in a sample prior to introduction into a chromatographic column is generally disclosed comprising a housing, an adsorbent disposed in the housing, and first and second conduits having an inlet and an outlet, respectively, for transferring fluid out of and into the housing during adsorption/dry purge and desorption stages, respectively. In some embodiments, the inlet of the first conduit and the outlet of the second conduit are both disposed in one end of the housing and are offset from each other with respect to the adsorbent.

Abstract: Disclosed are systems and methods that include a sampling device, a chromatographic column, and a transfer line through which a fluid containing analytes to be measured are communicated from the sampling device to the column. The pressure at which the fluid containing the analytes is applied at the inlet of the transfer line is adjusted as the temperature of the column increases in accordance with certain relationships in order to maintain a substantially constant flow rate or velocity for the fluid exiting the column. In this way, the system compensates for changes in the viscosity of the fluid flowing through the column that result from changes in the column temperature.

Abstract: A system for controlling the flow rate into a chromatographic column is disclosed generally comprising communicating a fluid to the column through a transfer line, measuring the inlet pressure, determining the outlet pressure, and adjusting the applied pressure until the inlet and outlet pressures produce a desired flow rate for the transfer line outlet. In certain embodiments, the applied pressure is adjusted by controlling a proportional valve. In some embodiments, the outlet pressure is determined by measuring the pressure drop across the transfer line and calculating the outlet pressure from the measured inlet pressure and the pressure drop.

Abstract: A system for controlling the flow rate into a chromatographic column is disclosed generally comprising communicating a fluid to the column through a transfer line, measuring the inlet pressure, determining the outlet pressure, and adjusting the applied pressure until the inlet and outlet pressures produce a desired flow rate for the transfer line outlet. In certain embodiments, the applied pressure is adjusted by controlling a proportional valve. In some embodiments, the outlet pressure is determined by measuring the pressure drop across the transfer line and calculating the outlet pressure from the measured inlet pressure and the pressure drop.

Abstract: A system for controlling the flow rate into a chromatographic column is disclosed generally comprising communicating a fluid to the column through a transfer line, measuring the transfer line inlet pressure, determining the transfer line outlet pressure, and adjusting the applied pressure until the inlet and outlet pressures produce a desired flow rate for the transfer line outlet. In certain embodiments, the applied pressure is adjusted by controlling a proportional valve. In some embodiments, the outlet pressure is determined by measuring the pressure difference across the transfer line and calculating the transfer line outlet pressure from the measured inlet pressure and the pressure difference.

Abstract: Disclosed are systems and methods that include a sampling device, a chromatographic column, and a transfer line through which a fluid containing analytes to be measured are communicated from the sampling device to the column. The pressure at which the fluid containing the analytes is applied at the inlet of the transfer line is adjusted as the temperature of the column increases in accordance with certain relationships in order to maintain a substantially constant flow rate or velocity for the fluid exiting the column. In this way, the system compensates for changes in the viscosity of the fluid flowing through the column that result from changes in the column temperature.