Patexia seeks prior art for US Patent 7,113,230 (‘230) - “Method and apparatus for deriving a channel map for a digital television receiver.” The patent allegedly describes a digital TV (DTV) receiver that automatically scans multiple TV channels for a signal to create a listing of viewable TV channels, sometimes called “scan-the-sky” algorithms. This is done by measuring the amplitude of the signal, comparing it to a locally stored threshold, and removing the channel from a locally stored map of TV channels if the amplitude is less than the threshold value.

Deriving a channel map for a DTV receiver takes place by following these steps (Figure 1):

• A processor controls a tuner to periodically scan through each channel frequency to find a strong signal.
• Using a comparator, the signal amplitude is compared with a threshold value.
• The threshold value is set by the processor and is dynamically determined by:
• If the processor does not detect valid program information for a channel thought to be viewable, the threshold value is raised.
• If the processor detects valid program information, then information on the estimated noise level in the received DTV signal is used to update the threshold value.
• With the threshold value, if the comparator finds:
• The signal amplitude is greater than the threshold value, the processor moves on to the next channel frequency.
• The signal amplitude is less than the threshold value, the processor removes the channel from a channel map, and then moves on to the next channel frequency.

Figure 1.Deriving a channel map for a DTV receiver