fft – Frequency Interpolation of DFT to create Zero-Padded IFFT

As a response to this question I have proposed interpolating new samples in a DFT (meaning the frequency samples of an existing DFT result) sufficient to be the new samples that if we were to take the inverse DFT we would get a zero padded sequence. The property referenced is that a zero padded time domain sequence will create interpolated samples in between the existing samples of the DFT of the original sequence. The new samples are determined from a circular convolution of the DFT with the Dirichlet Kernel, and when done properly, the inverse FFT of the result will be the original sequence zero-padded out to the longer length.

In deriving the details of implementing that, my most efficient solution (in a long round-about path to get there not seeing the forest for the trees) ended up being to simply take the inverse FFT, zero pad that and take the FFT.

This leads to my question now in that if our intention was to create an interpolated FFT from a given FFT (that would be the FFT of a zero padded inverse FFT), is there a more direct approach that would be more efficient than inverse FFT, zero pad, FFT based on the convolution property stated? Can we predict the frequency domain samples without having to go to the time domain in a way that would be more efficient?

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