A radio frequency digital receiver system for detecting RF signals, comprising: an RF digital receiver including discrete Fourier transform means, the digital receiver system for making detection decisions on an RF signal received by an antenna based on a spectral estimate formed from an output of the DFT means; the digital receiver system characterised in that the RF digital receiver is configured to: a) sample the RF signal to provide a sequence of data capture windows; b) process the data capture windows with a discrete Fourier-transform; c) apply spatially variant apodization configured for performing digital signal processing on the complex output of the Fourier-transformed data, to obtain a spectral estimate, wherein applying the SVA includes: calculating parameters α at each frequency bin according to the following equation: α = R X k X k + 1 + X k − 1 where k is an integer representing the frequency bin applying the calculated parameters to each frequency bin according to X a k = { X k, f o r α < 0 X k − α X k + 1 + X k − 1, f o r 0 ≤ α ≤ 1 2 X k − 1 2 X k + 1 + X k − 1, f o r α > 1 2 and (d) performing detections on the spectral estimate. an RF digital receiver including discrete Fourier transform means, the digital receiver system for making detection decisions on an RF signal received by an antenna based on a spectral estimate formed from an output of the DFT means; the digital receiver system characterised in that the RF digital receiver is configured to: a) sample the RF signal to provide a sequence of data capture windows; b) process the data capture windows with a discrete Fourier-transform; c) apply spatially variant apodization configured for performing digital signal processing on the complex output of the Fourier-transformed data, to obtain a spectral estimate, wherein applying the SVA includes: calculating parameters α at each frequency bin according to the following equation: α = R X k X k + 1 + X k − 1 where k is an integer representing the frequency bin applying the calculated parameters to each frequency bin according to X a k = { X k, f o r α < 0 X k − α X k + 1 + X k − 1, f o r 0 ≤ α ≤ 1 2 X k − 1 2 X k + 1 + X k − 1, f o r α > 1 2 and (d) performing detections on the spectral estimate. a) sample the RF signal to provide a sequence of data capture windows; b) process the data capture windows with a discrete Fourier-transform; c) apply spatially variant apodization configured for performing digital signal processing on the complex output of the Fourier-transformed data, to obtain a spectral estimate, wherein applying the SVA includes: calculating parameters α at each frequency bin according to the following equation: α = R X k X k + 1 + X k − 1 where k is an integer representing the frequency bin applying the calculated parameters to each frequency bin according to X a k = { X k, f o r α < 0 X k − α X k + 1 + X k − 1, f o r 0 ≤ α ≤ 1 2 X k − 1 2 X k + 1 + X k − 1, f o r α > 1 2 and calculating parameters α at each frequency bin according to the following equation: α = R X k X k + 1 + X k − 1 where k is an integer representing the frequency bin applying the calculated parameters to each frequency bin according to X a k = { X k, f o r α < 0 X k − α X k + 1 + X k − 1, f o r 0 ≤ α ≤ 1 2 X k − 1 2 X k + 1 + X k − 1, f o r α > 1 2 and (d) performing detections on the spectral estimate.