Application of S-band resonant cavity filters for 4G rejection at TTC Ground Stations

S-band ground station is providing Telemetry Tele-Command TTC support to the remote sensing satellites $24\times 7$ and in the recent years due to the 4G mobile signals from the base-station towers the satellite signal encounters a strong interference. Due to this interference ground station receive systems don't work properly resultant as a poor carrier to noise ration C/NO, poor energy per bit to the noise density EB/No at the receiver and observed receiver unlock and data break during different satellite passes. This paper presents the application of low loss combline coaxial cavity bandpass filter for 4G signal rejection at TTC ground station. The filter is a 5th order Chebyshev tunable using tuning and coupling screws. The center frequency F0, lower cut-off frequency FC1 and upper cut-off frequency FC2 of the filter is set to 2225MHz, 2169MHz and 2280 MHz respectively. The filter is having an insertion loss of 1.0dB, $\pm 0.5\text{dB}$ of passband ripple and 40dB rejection at $\mathrm{F}0\pm 55 \ \text{MHz}$