Patent ID: 7612618

Claim:
A phase locked loop (PLL) apparatus of an orthogonal frequency division multiplexing (OFDM) system, comprising: a frequency dividing means for dividing an oscillating signal; a phase detecting means for detecting a phase difference between a reference signal and the divided signal from the frequency division means and outputting a phase difference signal; a variable loop filter for filtering the phase difference signal outputted from the phase detecting means; a voltage controlled oscillating means for outputting the oscillator signal to the frequency dividing means according to the voltage control signal filtered from the variable loop filter; and a variable loop filter control means for varying a filtering band of the variable loop filter for each of the plurality of channel bands having a plurality of subcarrier channels with subcarrier bandgaps between each of the plurality of subcarrier channels, wherein each of the subcarrier bandgaps change for each of the plurality channel bands, and wherein each of the plurality of subcarrier channels sustain orthogonality between each of the plurality of subcarrier channels when each of the plurality of channel bands change from a first channel band to a second channel band.