Design of an S-Band Diplexer for Telemetry and Telecommand Subsystems in LEO Satellites

Ahmadi, Behzad; Narimani, Razieh; Hosseini, Elham

doi:10.22034/jsst.2024.1485

Design of an S-Band Diplexer for Telemetry and Telecommand Subsystems in LEO Satellites

Document Type : Original Research Paper

Authors

Behzad Ahmadi ¹

Razieh Narimani ²

Elham Hosseini ¹

¹ Assistant Professor, Satellite Research Institute, Iranian Space Research Center, Tehran, Iran

² Instructor, Satellite Research Institute, Iranian Space Research Center, Tehran, Iran

10.22034/jsst.2024.1485

Abstract

This study investigates the design requirements for telemetry and telecommand subsystems in satellites operating in low Earth orbit (LEO) and outlines the specifications for a diplexer suited for the S-band frequency range. The analysis emphasizes the critical impact of transmitter signal leakage and noise floor levels on diplexer performance. The proposed diplexer incorporates two bandpass filters operating at distinct frequency bands, enabling simultaneous transmission and reception through a single antenna in two-way communication systems. One of the primary design challenges stems from satellites' limited power generation capabilities, necessitating a strong focus on minimizing power consumption across all subsystems. In this context, reducing power loss in the telemetry and telecommand subsystem is crucial, as the diplexer directly influences transmitter power consumption and receiver sensitivity. Therefore, achieving minimal transmission loss is a critical design objective, which requires employing high-quality factor (Q-factor) technologies in the design of the filters. While waveguides provide superior Q-factors, their large dimensions and high mass render them unsuitable for S-band applications in satellite systems. Similarly, due to sublayer losses, ceramic substrate technologies, such as microstrip and stripline, fall short of the required Q-factor. To overcome these limitations, this study introduces a diplexer designed using coaxial technology, which offers an optimal balance of high Q-factor, compact dimensions, and low mass. The designed diplexer achieves a return loss greater than 20 dB, a transmission loss of less than 0.5 dB, and an isolation exceeding 50 dB, meeting the stringent requirements of LEO satellite subsystems.

Keywords

Diplexer

LEOSatellites

SBand

Telemetry and Telecommand Subsystem: Filter

Subjects

telecommunications

Article Title Persian

طراحی دیپلکسر باند S برای زیرسیستم تله‌متری و تله‌کامند ماهواره‌های LEO

Authors Persian

بهزاد احمدی ¹

راضیه نریمانی ²

الهام حسینی ¹

¹ استادیار، پژوهشکده سامانه‌های ماهواره پژوهشگاه فضایی ایران، تهران، ایران

² مربی، پژوهشکده سامانه‌های ماهواره پژوهشگاه فضایی ایران، تهران، ایران

Abstract Persian

در این مقاله ضمن بررسی الزامات موجود در زیرسیستم تله‌متری و تله‌کامند یک ماهواره در مدار LEO، مشخصات مورد نیاز دیپلکسر جهت استفاده در این زیرسیستم در باند فرکانسی S استخراج شده و تاثیر نشت سیگنال فرستنده و کف نویز فرستنده بر روی مشخصات دیپلکسر، مورد مطالعه قرار گرفته است. دیپلکسر دارای دو فیلتر میان‌گذر با فرکانس‌های گذر متفاوت است که در سیستم‌های مخابراتی دوطرفه هم‌زمان، ارسال و دریافت را از طریق یک آنتن امکان‌پذیر می‌کند. به دلیل سختی تولید توان در ماهواره‌ها یکی از قیود اصلی طراحی مربوط به توان مصرفی هر زیرسیستم است و به همین دلیل تا حد امکان می‌بایست از اتلاف توان جلوگیری شود. از آن‌جا که در زیرسیستم تله‌متری و تله‌کامند وجود دیپلکسر هم در مسیر ارسال و هم در مسیر دریافت باعث تاثیر قابل توجه بر توان مصرفی فرستنده و حساسیت گیرنده می شود، الزام اولیه در طراحی این قطعه کمینه کردن تلف عبوری آن است که این مهم به معنای استفاده از تکنولوژی‌هایی با ضریب کیفیت بالا در طراحی فیلتر است. استفاده از موجبرهای توخالی با وجود در اختیار گذاشتن ضریب کیفیت بسیار بالا، در باند S به دلیل ابعاد و جرم بالا مرسوم نیست. فناوری‌های مبتنی بر زیرلایه های سرامیکی مانند مایکرواستریپ و استریپ‌لاین نیز به دلیل تلفات زیر لایه‌ها ضریب کیفیت مورد نیاز را برآورده نمی‌کند. با توجه به این مسائل، در این مقاله با استفاده از فناوری کابل‌های هم محور با سطح مقطع مربعی که هم ضریب کیفیت مناسب و هم ابعاد و جرم کمی دارند، طراحی دیپلکسر انجام شده است. دیپلکسر طراحی شده دارای تلف بازگشتی بهتر از 20 dB، تلف عبوری کمتر از 0.5 dB و ایزولاسیون بهتر از 50 dB است.

Keywords Persian

دیپلکسر

ماهواره‌های LEO

باند S

زیرسیستم تله‌متری و تله‌کامند

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