Design of a radio frequency signal editing and sampling rate conversion system based on Qt platform

Radio frequency (RF) signal editing and sampling rate conversion are critical techniques employed in communication and radar systems for the extraction of targeted signals and collaborative processing of multiple standard waveforms. The existing international business tools (such as BIRD’s RF-Editor, and the vector signal analyzers from Rohde & Schwarz and Agilent) offer functions for signal editing and sampling rate conversion; however, they fail to address the urgent demand for cost-efficient and highly adaptive solutions due to economic and technological limitations, particularly in frequency hopping communication systems and multitarget radar tracking systems.

To address these issues, an integrated RF signal editing and sampling rate conversion system was developed herein on the Qt platform. A filter design method based on an improved Kaiser window function was used in the RF signal editing module. This method resolved the trade-off between performance and complexity inherent in traditional Kaiser window designs. A cost function was defined to quantitatively evaluate the performance of the Kaiser window function，which usede the normalized transition bandwidth and minimum stopband attenuation as the performance metrics. This function incorporated a weighting factor, enabling designers to dynamically prioritize transition bandwidth and stopband attenuation based on specific application requirements. An efficient golden ratio search algorithm was employed to optimize the shape parameter of the Kaiser window with minimal computational overhead. It operated within a well-defined initial search range and iteratively refined the solution interval based on objective function evaluations until it satisfied the predefined convergence criteria. The optimized Kaiser window was used to truncate the ideal infinite impulse response and obtain a finite impulse response low-pass filter with a customizable transition bandwidth and stopband attenuation. In addition, direct modulation technology was used for precise spectrum shifting. A sampling rate conversion method that integrated local interpolation and Sinc-windowed function truncation was used in the sampling rate conversion module. The Hanning window smoothed the edges of the Sinc function, whereas the local interpolation strategy considerably reduced the computational complexity; these improvements facilitated rapid conversion across arbitrary sampling rate multiples. By integrating these methodologies and adopting a hierarchical modular design paradigm, a Qt-based RF signal editing and sampling rate conversion system was developed.

Experiments conducted using measured data revealed that 1) the designed filter exhibited excellent frequency-selective characteristics and effectively attenuated signals outside the specified frequency band; 2) the frequency shift function achieved a relative error within 0.8%, satisfying the engineering tolerance requirements for broadband frequency modulation communication systems; and 3) sampling rate conversion introduced minimal signal distortion, with a time-domain mean square error (MSE) of <0.01 and frequency-domain logarithmic spectral distance of <1 dB. Notably, the computational efficiency was enhanced by over 70% compared with that of traditional Sinc interpolation with an upsampling factor of 2.5.

The proposed system could efficiently and flexibly perform RF signal editing and sampling rate conversion with fast response and stable operation. Compared with the existing commercial software solutions, it eliminated the need for costly licensing fees and specialized hardware dependencies, supported cross-platform deployment on both Windows and Linux, and featured a modular architecture that enabled independent function calling and expansion. These characteristics made it more flexible than closed-source commercial software.