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This paper presents X-Band wide bandwidth coaxial cavity band pass filter for spacecraft checkout applications. Mostly coaxial cavity filter is used for designing narrow bandwidth filter, less than 1 percent bandwidth but in this paper an attempt has been made to design and develop a compact size filter with more than 1 percent bandwidth. The main advantage of this designed filter is its wide bandwidth and excellent harmonic rejection performance. The realized filter has 1.1 dB insertion loss at center frequency of 8.2 GHz, better than 18 dB return loss over a passband of 7.96 GHz to 8.44 GHz and 60 dB rejection at 720 MHz away from center frequency. Achieved results of proposed filter are in good agreement with the design specifications.

SAR payloads are generally used on-board all-weather imaging satellites. When compared to optical payloads they are found more suitable for target detection applications in absence of sunlight. Their working principle is based on transmission and reception of pulses of predefined pulse characteristics. The reflected pulse from earth terrain is analysed and processed based on the changes in the transmitted pulses. This analysis provides all the necessary information regarding the terrain. The effectiveness of the image generation depends on the accuracy of the desired pulse that is transmitted. Thus there is a need for characterizing the transmitted pulses for all the relevant parameters. This paper provides an automated scheme to characterize the transmit receive modules in a typical LFM (Liner Frequency Modulation) SAR payload. This scheme includes a test set up comprising of various COTS measurement instruments. It also includes an automation software which conducts all the measurements using the test set up and presents the results in a standard form.

Alumina thin coatings were grown on Germanium (Ge) coated black polyimide (GBP) or Kapton which has been used as a sunshield membrane on communication satellite antennas to protect it from environmental degradation during ground storage and implementation. The deposited nanoalumina coatings were found to be optically transparent in solar regime in spectral window while RF characteristic revealed negligible losses. Space worthiness of the coating was examined by simulated environments, e.g. humidity, thermal cycling and thermovacuum tests. No degradation was observed in its microstructural, thermo-optical, electrical, chemical state and RF characteristic in particular Ku and Ka bands. The aforesaid study indicates that the alumina thin coating is able to prevent surface degradation of GBP retaining the thermo-optical properties of the Ge coated Kapton and RF transparency which are functional requirements for communication antenna. The thickness of the optimized alumina coating was ~60 nm.

Protective alumina thin films of different thicknesses (35–95 nm) were grown by pulsed RF magnetron sputtering technique at room temperature on germanium (Ge) coated black polyimide or Kapton® substrate which is often employed as sunshield membrane on communications satellite antennas. The thin alumina top layer provides shielding of Ge coating from degradation during storage. The alumina thin film was characterized by X-ray diffraction, field emission scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) techniques to investigate microstructural and electronic characteristics. Thermo-optical properties such as IR emittance, solar absorptance, reflectance and transmittance and electrical property e.g. sheet resistance of the deposited alumina films were measured. The RF losses e.g. insertion loss and return loss were measured in both Ku band (10.5–14.5 GHz) and Ka band (27–40 GHz). Finally, to prove anti-degradation behavior of alumina thin film, water droplet spreading experiments were carried out and evaluated its chemical degradation by XPS.