V.M. Vladimirov, V.V. Markov, D.V. Petrov, V.N. Shepov

A tri-band (L1/L2/L3) low-noise amplifier (LNA) for an active antenna for the high accuracy positioning using GLONASS/GPS signals has been designed. Microstrip filters (MSF) with low insertion losses in the passband and an input L1 and L2+L3 diplexer have been developed for the LNA input circuit. The measured insertion losses in the passband of MSF along with the diplexer in both frequency bands are equal to - 1,2 dB, and non-uniformity is 0,4 dB. The return losses in both bands exceed - 15 dB. The group delay non-uniformity is better than 4 ns in each band. The overall dimensions of the input MSF are 9×7×4 mm. MSFs with high attenuation in the stopbands have been developed for the microwave path. The measured squareness of the L1 MSF response at the level ΔF-30 dB /ΔF-3 dB is 2,5, while at the level ΔF-40 dB /ΔF-3 dB it is 3,2. The squareness of the L2+L3 MSF response at the level ΔF-30 dB /ΔF-3 dB is 2,2, and at the level ΔF-40 dB /ΔF-3 dB it is 2,8. Here, the MSF insertion losses of each band including the combiner do not exceed - 2,5 dB, non-uniformity in the passband is less than 0,8 dB, return losses is better than - 14 dB, group delay in the passband of each frequency band is less than 4 ns. The MSF overall dimensions for the microwave path of the L1 and L2+L3 LNA are 14×7×3 mm. The developed MSFs allow one to achieve the LNA noise coefficient not exceeding 1,8 dB, with the gain being up to 40 dB, VSWR lower than 1,5 and group delay non-uniformity less than 4 ns in all the three frequency bands. Here, the LNA current consumption is less than 50 ma. The results obtained suggest the possibility of applying MSF in the LNA input circuits of the high accuracy active antennas of multiband GNSS receivers.