Communications device including a filter for notching wideband transmit signals and associated methods

A wideband communications device comprising:

• a receiver to periodically operate in a scan mode for receiving a narrowband signal from at least one narrowband communications device;
• a signal analyzer downstream from said receiver and operable to determine a frequency of the received narrowband signal;
• a modulator and a filter downstream from said modulator and operable to generate an output wideband complex signal with at least one frequency notch therein;
• said filter comprising
• a finite impulse response (FIR) filter comprising L taps to generate N output values, with L>N,
• a Fast Fourier Transform (FFT) block downstream from said FIR filter and having the length N so that filter transition regions occur between frequency bins of said FFT block,
• a notching block downstream from said FFT block and from said signal analyzer and operable to the generate at least one frequency notch based on the frequency of the received narrowband signal, and
• an Inverse Fast Fourier Transform (IFFT) block downstream from said notching block and having the length N;
• and
• a transmitter downstream from said filter and operable to transmit the output wideband complex signal with at least one frequency notch therein.

A method for generating an output wideband complex signal with at least one frequency notch therein, the method comprising:

• modulating an output wideband complex signal to be transmitted;
• and
• using a filter for filtering the modulated output wideband complex signal to include the at least one frequency notch therein, the filtering comprising
• filtering the modulated output wideband complex signal using a finite impulse response (FIR) filter comprising L taps to generate N output values, with L>N,
• generating a Fourier transform of the modulated wideband complex signal using a Fast Fourier Transform (FFT) block downstream from the FIR filter, the FFT block having a length N so that filter transition regions occur between frequency bins of the FFT block,
• generating the at least one frequency notch in the Fourier transform using a notching block downstream from the FFT block, and
• generating an inverse Fourier transform of the Fourier transform with the at least one frequency notch therein using an Inverse Fast Fourier Transform (IFFT) block downstream from the notching block, the IFFT block having the length N.