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

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;
• the filter operating with a block length of M, with M =N/2, and wherein the N output values are filtered every M samples in time.

A communications device comprising:

• 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 operable to generate the at least one frequency notch, and
• an Inverse Fast Fourier Transform (IFFT) block downstream from said notching block and having the length N;
• said filter having a filter gain halfway between frequency bins of said FFT block with a magnitude of at least 0.5, and is anti-symmetric so that a composite filter bank is spectrally flat.

A communications device comprising:

• 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, said FFT block having a gain of zero one frequency bin away from a center frequency bin,
• a notching block downstream from said FFT block and operable to generate the at least one frequency notch, and
• an Inverse Fast Fourier Transform (IFFT) block downstream from said notching block and having the length N.

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;
• the filter having a filter gain halfway between frequency bins of the FFT block with a magnitude of at least 0.5, and is anti-symmetric so that a composite filter bank is spectrally flat.

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, the FFT block having a gain of zero one frequency bin away from a center frequency bin,
• 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.