On-board electrically small diplexer for future radio science planetary RF subsystem applications

• Developed an electrically small microstrip diplexer with compact dimensions (0.6 λ × 0.511 λ). • Achieved high port isolation (>30 dB) for dual frequencies, critical for RF subsystem performance. • Designed tailored intrinsic filters with multiple transmission zeros for superior stopband characteristics. • Included tunable stubs for frequency flexibility in diverse RF applications. • Fabricated and validated the diplexer, with results demonstrating excellent agreement with simulations. • Offers potential for integration into future planetary exploration Radio Occultation systems. An electrically small Microstrip diplexer is presented for the on-board Radio Occultation (RO) system. The planetary atmosphere undergoes complex changes and to understand it thoroughly, Radio Occultation techniques are being comprehensively employed either through ground or satellite stations. The change or shift in the frequency is the prime methodology for occultation measurements. Typically, the RF subsystem of the satellite payload possesses two distinct frequency synthesizers. The proposed diplexer consists of two identical geometry allowing a balance between high port isolation and suitability for onboard RF applications. The tailored intrinsic filters create numerous transmission zeros, causing agreeable stopband and edges. The stubs of the diplexer can be altered for further fine-tuning of the diplexer in case of frequency alterations for other RF subsystems. The electrical dimensions of the self-symmetrical diplexer are 0.6 ƛ x 0.511ƛ at the lowest frequency. The port isolation is above 30 dB for dual frequencies. A prototype is prepared and validated results are presented. The proposed diplexer can be useful for multiple RO RF subsystems in future planetary applications.