In certain embodiments, a method includes generating a first signal and a second signal. The first signal includes at least one first sub-signal, and the second signal includes at least one second sub-signal. A subcarrier frequency spacing of the first sub-signal is M times as large as a subcarrier frequency spacing of the second sub-signal. The method further includes separately sending each first sub-signal and each second sub-signal. In a range of a first preset frequency apart from a reference subcarrier frequency, all the second sub-signals sent on a subcarrier corresponding to a subcarrier frequency whose difference from the reference subcarrier frequency is a non-integer multiple of the subcarrier frequency spacing of the first signal are zero signals. The reference subcarrier frequency is a subcarrier frequency of the first sub-signal adjacent to the second signal in a frequency domain.