OFDM signal spectrum shaping device and method for OFDM signal spectrum shaping

1. An orthogonal frequency division multiplexing (OFDM) signal spectrum shaping device, comprising:

an input interface configured to receive an input signal;

a modulation portion coupled to the input interface, configured to modulate the input signal to generate a plurality of uncompensated sub-carriers; and

a sub-carrier gain control module configured to apply a plurality of gain factors to the plurality of uncompensated sub-carriers to generate a plurality of compensated sub-carriers that are substantially equal in amplitude; wherein a different set of gain factors is used for each frequency hopping band.

2. The OFDM signal spectrum shaping device of claim 1 , wherein the sub-carrier gain control module is configured to:

apply a first gain factor to a first uncompensated sub-carrier to obtain a first compensated sub-carrier; and

apply a second gain factor to a second uncompensated sub-carrier to obtain a second compensated sub-carrier, wherein the amplitude of the first compensated sub-carrier and the second compensated sub-carrier are substantially equal in amplitude.

3. The OFDM signal spectrum shaping device of claim 2 , further comprising:

an Inverse Fast Fourier Transform (IFFT) component configured to transform the plurality of sub-carriers to a time domain waveform; and

a digital to analog converter (DAC) for converting at least a portion of the time domain waveform to an analog signal.

4. The OFDM signal spectrum shaping device of claim 3 , further comprising a synthesizer configured to generate a local oscillator signal for modulating the analog signal to generate a modulated signal.

5. The OFDM signal spectrum shaping device of claim 4 , wherein the synthesizer selectively varies frequency of the local oscillator signal over time so that the modulated signal is a frequency hopping signal that has varying frequency bands over time.

6. The OFDM signal spectrum shaping device of claim 4 , wherein the synthesizer is controlled at least in part by a band selection signal for controlling the local oscillator signal's frequency band selection among a plurality of frequency bands.

7. The OFDM signal spectrum shaping device of claim 4 , wherein the synthesizer is controlled at least in part by a hop timing signal for controlling timing of the local oscillator signal's frequency band selection among a plurality of frequency hop bands.

8. The OFDM signal spectrum shaping device of claim 4 , further comprising a band gain control module that generates a time varying band gain factor applied to the modulated signal such that a resulting band gain adjusted modulated signal has time varying frequency bands that are substantially the same in amplitude.

9. The OFDM signal spectrum shaping device of claim 8 , further comprising a transmitter radio for transmitting the band gain adjusted modulated signal.

10. The OFDM signal spectrum shaping device of claim 2 , further comprising a preamble inserter for inserting a synchronization preamble to at least a portion of the time domain wave form.

11. A method for shaping an orthogonal frequency division multiplexing (OFDM) signal spectrum, comprising:

receive an input signal;

at an orthogonal frequency division multiplexing (OFDM) communications device, modulating the input signal and generating generate a plurality of uncompensated sub-carriers; and

at the orthogonal frequency division multiplexing (OFDM) communications device, applying a plurality of gain factors to the plurality of uncompensated sub-carriers to generate a plurality of compensated sub-carriers that are substantially equal in amplitude; wherein a different set of gain factors is used for each frequency hopping band.

12. The method of claim 11 , wherein applying the plurality of gain factors includes:

applying a first gain factor to a first uncompensated sub-carrier to obtain a first compensated sub-carrier; and

applying a second gain factor to a second uncompensated sub-carrier to obtain a second compensated sub-carrier, wherein the amplitude of the first compensated sub-carrier and the second compensated sub-carrier are substantially equal in amplitude.

13. The method of claim 12 , further comprising:

performing an Inverse Fast Fourier Transform (IFFT) to transform the plurality of sub-carriers to a time domain waveform; and

converting at least a portion of the time domain waveform to an analog signal.

14. The method of claim 13 , further comprising generating a local oscillator signal, and modulating the analog signal using the local oscillator signal to generate a modulated signal.

15. The method of claim 14 , further comprising selectively varying frequency of the local oscillator signal over time so that the modulated signal is a frequency hopping signal that has varying frequency bands over time.

16. The method of claim 14 , further comprising using a band selection signal to control at least in part the local oscillator signal's frequency band selection among a plurality of frequency bands.

17. The method of claim 14 , further comprising using a hop timing signal to control at least in part timing of the local oscillator signal's frequency band selection among a plurality of frequency hop bands.

18. The method of claim 14 , further comprising generating a time varying band gain factor, and applying the time varying band gain factor to the modulated signal such that a resulting band gain adjusted modulated signal has time varying frequency bands that are substantially the same in amplitude.

19. The method of claim 18 , further comprising transmitting the band gain adjusted modulated signal.

20. The method of claim 12 , further comprising inserting a synchronization preamble to at least a portion of the time domain wave form.

21. A multi-band (MB) orthogonal frequency division multiplexing (OFDM) (MB-OFDM) transmitter to operate in a plurality of different hop bands, the transmitter comprising:

modulation circuitry to generate a plurality of uncompensated sub-carriers that are modulated with input modulation symbols; and

spectrum shaping circuitry to apply a plurality of gain factors to the uncompensated sub-carriers to generate a plurality of compensated sub-carriers that are substantially equal in amplitude to counter effects of gain variations in the different hop bands; wherein a different set of gain factors is used for each of the different hop bands.