Efficient frequency-domain beamforming

A method of determining an output signal including one of a channel signal or a beam signal, the method comprising:

• receiving, at a frequency-domain beamforming circuit, in-phase and quadrature (I-Q) samples for B beams or C′ channels at one of a first interface coupled to an analog front end or a second interface coupled to a processing circuit;
• determining a Discrete Fourier transform (DFT) for the I-Q samples for each beam or for each channel to determine frequency-domain vector signals through a Fast Fourier Transform (FFT) or any fast variant thereof,
• multiplying frequency-domain filter coefficients and the frequency-domain vector signals to produce vector output signals;
• combining the vector output signals entering a given channel or a given beam to produce a channel signal or a beam signal;
• determining an inverse DFT for the channel signal or the beam signal to produce a time-domain signal through an inverse FFT (IFFT) or any fast variant thereof,
• performing an overlap/add operation on the time-domain signal to produce the output signal;
• and
• providing the output signal to one of the first interface or the second interface.

A system comprising:

• a first interface coupled to an analog front end;
• a second interface coupled to a signal processing circuit;
• and
• a frequency-domain beamforming circuit coupled to the first interface and the second interface, the frequency-domain beamforming circuit configured to:
• receive in-phase and quadrature (I-Q) samples for B beams or C′ channels;
• determine a Discrete Fourier transform (DFT) for the I-Q samples for each beam or for each channel to determine frequency-domain vector signals;
• multiply frequency-domain filter coefficients and the frequency-domain vector signals to produce vector output signals;
• combine the vector output signals entering a given channel or a given beam to produce a channel signal or a beam signal;
• determine an inverse FFT (IFFT) for the channel signal or the beam signal to produce a time-domain signal;
• perform an overlap/add operation on the time-domain signal to produce an output signal;
• provide the output signal to one of the first interface or the second interface;
• wherein, in a receive mode, the frequency-domain beamforming circuit is configured to replicate the frequency-domain vector signals from the output of each of the FFTs to each of a plurality of frequency-domain filters such that the frequency-domain beamforming circuit performs one FFT per channel;
• and
• wherein, in a transmit mode, the frequency-domain beamforming circuit is configured to perform one FFT operation per beam, sum the frequency-domain vector signals on a per element basis in the frequency domain, and reuse the IFFT for each channel.