gr-iqbal

gr-iqbal is a GNU Radio module designed to address IQ imbalance issues in software-defined radio (SDR) receivers. It suppresses symmetrical images in the spectrum that arise from imperfections in the quadrature receiver's RX path. The tool is particularly useful for improving signal quality in SDR applications where hardware-induced IQ imbalances degrade performance.

It consists of two primary subblocks: 'IQ Bal Fix' and 'IQ Bal Optimize'. The 'IQ Bal Fix' subblock applies correction to a complex stream using magnitude and phase parameters, mimicking hardware corrections as used in devices like the USRP. Parameters can be set manually or via messages. The 'IQ Bal Optimize' subblock performs blind detection of imbalance by minimizing correlation between the left and right parts of the spectrum, drawing inspiration from academic papers and SDR software like sdr#.

This tool is relevant for cybersecurity tasks involving wireless signal analysis, such as RF reconnaissance or SDR-based attacks, where clean spectral analysis is crucial.

gr-iqbal operates through two subblocks. 'IQ Bal Fix' corrects IQ imbalance in a complex stream using magnitude/phase parameters with an algorithm identical to USRP hardware correction; parameters are configurable manually or via messages. 'IQ Bal Optimize' blindly estimates imbalance by minimizing spectral correlation between left and right halves, using techniques inspired by internet papers and SDR tools like sdr#, though with distinct implementation details.