#### In-depth

## FSK generation

FSK can be generated by switching between distinct frequency sources; however, it is likely that there will be discrete phase jumps between the symbol states at the switching time. Any phase discontinuity at the symbol boundary will result in a much greater prominence of high frequency terms in the spectrum, implying a wider bandwidth for transmission. |
| Alternatively, FSK can be realized by applying the data signal as a control voltage to a voltage controlled oscillator-VCO (see in-depth section). Here the phase transition between consecutive symbol states is guaranteed to be smooth (continuous). FSK with no phase discontinuity between symbols is known as a Continuous Phase Frequency Shift Keying (CPFSK) format.