PE1-5.2 RF System Design & Link Budgets
You can construct a detailed system link budget using free space and practical loss models, apply world frequency band plans, and reason about 3G RF performance requirements and multicarrier power amplifiers.
The link budget is the calculation that decides whether a radio system exists at all — every gain and loss from transmitter to receiver, summed, against the required signal-to-noise ratio. Free space loss is the optimistic bound; the practical models exist because the real world adds terrain, buildings and rain. Multicarrier power amplifiers are the hard part of an SDR base station: amplifying many carriers at once demands linearity that costs efficiency, and that trade drives the whole RF design.
Work through these
World frequency band plans
Who is allowed to transmit where, which differs by country and constrains any multi-market design. It is the regulatory reality behind the flexibility argument.
Noise and channel capacity
The noise floor and the limit it puts on capacity. It is the same result as the communication subject, used here as a design constraint.
The link budget and free space loss
The accounting that decides whether a link works, starting with the loss in empty space. It is the calculation everything else in this topic refines.
Practical loss models
The models that add real terrain and buildings to the idealised loss above. They are empirical, and knowing they are empirical is important.
Detailed system link budget
The full calculation with every term included. Working one through is the exercise this topic exists for.
3G RF performance requirements
What a real standard demands of the radio, in numbers. It turns the abstract budget into a specification you could design against.
Multicarrier power amplifiers and the linearity-efficiency trade
Amplifying several carriers at once, and the trade that makes it hard: linearity costs efficiency. This is the single hardest analog problem in the field.
Signal processing capacity trade-off; design flow
How much processing the design needs and what that costs in power. It sets up the device comparison two topics down.
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Links last checked 30 Aug 2026.
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