The present disclosure relates to a slow-wave transmission line for transmitting slow-wave signals with reduced loss. In this regard, the slow-wave transmission line is formed in a multi-layer substrate and includes an undulating signal path. The undulating signal path includes at least two loop structures, wherein each loop structure includes at least two via structures connected by at least one intra-loop trace. The undulating signal path further includes at least one inter-loop trace connecting the at least two loop structures. Additionally, the slow-wave transmission line includes a first ground structure disposed along the undulating signal path. In this manner, a loop inductance is formed by each of the at least two loop structures, while a first distributed capacitance is formed between the undulating signal path and the ground structure.