As mentioned above, the fractional divider 12 generates predictable spurs which may be identified utilizing well known computer programs. The reference frequency fref and the divider ratio R therefore may be selected to generate spurs having amplitude and frequencies within a desired frequency band. For example, the reference frequency fref=2.225 and the corresponding reference divider R=7 49/89 is selected such that a a frequency resolution of 25 kHz, i.e. 2.225/89, maybe provided which accommodates a 25 kHz and 12.5 kHz channel spacing. Additionally, the generated spurs due to utilizing a reference divider R= 7 49/89 are found to be below the side band noise limits of the VCO 15. Referring to FIG 4. a frequency vs amplitude graph of the output of the VCO 15 for an exemplary fout=453.900 MHZ is shown. The horizontal axis of this graph illustrates the output frequency spectrum of the VCO 15 which includes the output frequency fout and the offset frequency spurs generated at 25 kHz intervals. The horizontal axis illustrates the amplitudes at the output frequency spectrum of the VC0 15. The level of predicted spurs at the offset frequencies is tabulated in the TABLE 1 below. Also included in the TABLE 1 are the 10 kHz VCO side band noise (SBN) at each of the off set spurs.

It may be noted that in each 25 kHz offset frequency the contribution of the generated spur to the SBN of the VCO 15 is negligible. It may be appreciated by one of ordinary skill in the art that at worse case the 100 kHz spur is equal to -86 dbc, i.e.( -87dbc)+(-97dbc). This results in a degradation in the side band noise of about -11 dbc. However, in many communication application this level is well within the communication systems specifications, such as desense and adjacent channel selectivity which is generally specified at -85 dbc.

Accordingly it may be appreciated that the reference divider R may be selected such that the generated spurs due to the fractional division of the synthesizer 10 fall below an spectral limit, such as the VCO side band noise.