♦   Link Budgets   ♦

RFCLB (Radio Frequency Communications Link Budget) is a Spreadsheet Workbook (shareware) for the computation of Spacecraft RF-Link Design Control Tables. It is tailored to space system applications and covers the functions of

• Telemetry, Tracking, and Commanding (TT&C)
• Payload Data Transmission (PDT)
• Δ-DOR Navigation.

The development of RFCLB started in 2014, supplementing a series of university courses in spacecraft engineering. Since then, the tool has continuously evolved as a Students Project (mentored by a lecturer and former senior staff member of the European Space Agency). Making RFCLB here available for download follows the spirit of free and open exchange of scholarly and academic work for science and technology.

RFCLB enables detailed insight into methods and core-budget calculations. This is a distinct advantage over other tools that might feature an appealing Graphical User Interface but are lacking transparency for users interested in applied equations and underlying principles.

RFCLB also includes user conveniences such as the automated import and export of design data from/to Interface Control Tables in MS-Word files [1,2]. This capability can massively reduce in projects the repetitive typing effort of manual data-transfer into/from TT&C link budget spreadsheet tables.

RFCLB can help students and practising engineers to apply, or to enhance, their skills in spacecraft TT&C link design, analyses and the relevant system trade-offs. The development of the tool follows recommendations of the Consultative Committee for Space Data Systems (CCSDS); this makes RFCLB suitable for professional spacecraft TT&C engineering.
The CCSDS recommends a computational technique for Radio Frequency and Modulation Systems used in Earth Stations and Spacecraft to determine detailed link budgets for TT&C. The complexity of these calculations is illustrated in the excerpt (click on image) from CCSDS 401 (4.1.5) B-3, showcasing the intricate nature of the involved calculations.

(click image to see excerpt)

Implementing these recommendations in software tools such as spreadsheets requires a significant effort. For those seeking an accessible solution, the RFCLB tool offers a practical implementation of the CCSDS recommendation for TT&C link budget calculations. The (educational) tool aligns with industry standards.

♦   Transmission Feed Lines   ♦

The shown transmission line with complex characteristic impedance Z_o implies a loss between input power P₁ and output power P₂. The example (values selected for simplicity) can identify software design-tool limitations. What would be the power-loss obtained by your software tool? Is the loss either 1.05dB; or 0.74dB; or 0.35dB; or a different value?
The actual loss is 0.35dB which is less than the matched line loss of 0.6dB for the 100 feet long Feed Line. One might wonder if, or why, the value of 0.35dB is correct, or why another software tool might obtain a different (wrong) result. The following tool can provide insight and is a general end-to-end loss-calculator for RF Feed Lines.
The accurate assessment of end-to-end losses implied by (long) cable-connections (feed lines) between source and load, is a very common engineering task. The tool can be useful for students in microwave engineering, and for RF engineers in general. The calculator is suitable also at low RF-frequencies, for which the characteristic impedance of the transmission line must be considered as a complex value. This makes the tool useful also for HAM-Radio applications.

The Microsoft Excel^® Workbook RF Transmission Line Loss Calculator is available for download as zip-File (1.7MB) including auxiliary files. Please, consider the following:

• The Workbook requires Excel 2016, or higher, or Microsoft 365 on PC-Windows. It applies VBA-Macros; therefore, it is incompatible with Macintosh Systems.
• Important: The tool must be installed in a directory that is only local on the PC. Do not install in a directory that is shared or synchronized with external drives.
• The file has been verified to be virus-free. If preferred, the user can subject the downloaded file to local anti-virus software.
  In Microsoft Office, macros from the Internet will be blocked by default. For steps to take to allow VBA macros, please consult this Microsoft article. An easy approach to unblock a downloaded file, is described here: Unblock.
  In Microsoft 365 and Office 2024, also the settings for ActiveX controls have changed to be disabled by default. For Steps to enable ActiveX controls, please consult this Microsoft article.

♦   RF Receiver Cascades   ♦

As a further supplement to RFCLB, a tool has been developed for cascade analyses in receiver systems. The assessment of end-to-end system noise performance implied by cascaded active and passive components from antenna to receiver, is a very common task in RF and microwave engineering. The tool can be useful for students, engineers and RF practitioners in general. The calculator is intuitive, and the user is supported by comments inserted in the tool.

The Microsoft Excel^® Workbook Cascade is available for download (Excel .xlsm-file, 1.7MB). Please, consider the following:

• The Workbook requires Excel 2016, or higher, or Microsoft 365 on PC-Windows. It applies VBA-Macros; therefore, it is incompatible with Macintosh Systems.
• Important: The tool must be installed in a directory that is only local on the PC. Do not install in a directory that is shared or synchronized with external drives.
• The file has been verified to be virus-free. If preferred, the user can subject the downloaded Excel file to local anti-virus software before loading into Excel.
  In Microsoft Office, macros from the Internet will be blocked by default. For steps to take to allow VBA macros, please consult this Microsoft article. An easy approach to unblock a downloaded file, is described here: Unblock.
  In Microsoft 365 and Office 2024, also the settings for ActiveX controls have changed to be disabled by default. For Steps to enable ActiveX controls, please consult this Microsoft article.