Design of optimum high order crossover coefficients. - Karel Hájek; Jirí Sedlácek (ICECS, 1998)

General multiple LC prototype filter solutions and optimization. - Karel Hajek; Jirí Sedlácek (ICECS, 2002)

New circuits for realization of the 1st and 2nd order all-pass LC filters with a better technological feasibility. - Karel Hajek; Z. Sedlacek; B. Sviezeny (ISCAS (3), 2002)

Minimization of offset of the tunable LP filters. - Karel Hajek; Jirí Sedlácek; Bohumir Sviezeny (ECCTD, 2005)

Time domain analysis of analog filters in MATLAB environment. - Karel Zaplatilek; Karel Hajek (ISCAS, 2006)

Low-distortion current-mode quadrature oscillator for low-voltage low-power applications with non-linear non-inertial automatic gain control. - Josef Bajer; Jiri Vavra; Dalibor Biolek; Karel Hajek (ECCTD, 2011)

Increased Sensitivity of Ultrasonic Radars for Robotic Use. - Karel Hájek (MESAS, 2018)

System of Standard Approximations for Optimum Frequency Filter Design. - Karel Hajek (SMACD, 2018)

Multiple Aliasing of Windowed Real-Valued Signal as a Cause of Accuracy Limitation of DFT Methods. - Karel Hajek; Zdenek Kohl (IEEE Access, 2025)