The different performance parameter of frequency synthesizers are as follows:

1. Frequency Range: This specifies the output frequency range, including the lower and higher frequencies. The units of frequency are hertz (Hz), or cycles per second.

2. Frequency resolution: This parameter is also referred to as the step size, and it specifies the minimum step size of the frequency increments.

3. Output level: The output power level is usually expressed in decibels. The output power can either be fixed, say, +10 dBm, or can cover a range, say, -120 to H-15 dBm.

4. Output flatness: This parameter specifies the flatness of the output power and is measured in decibels (dB).

5. Output impedance: This parameter specifies the nominal output impedance of the FS and usually is also the recommended load impedance. In most radiofrequency and microwave equipment, this is 50 ohms.

6. Switching speed: This parameter specifies the speed at which the FS can hop from frequency to frequency.

7. Phase transient: In most applications, the behavior of the phase when in a transient state is not defined. However, many applications need to define the transient characteristics very carefully.

8. Phase noise: In most Synthesizers the amplitude noise is much lower than the phase noise and is not specified separately. However, the phase noise is a major parameter and is expressed in a few ways. The most common way is to specify the noise density in 1-Hz bandwidth at specific offset from the carrier.

9. Harmonics: This parameter specifies the level of harmonics of the output frequency and depends on many components.