High-temperature superconducting Josephson junctions (HTSC JJs) have great potential as promising materials for creating high-frequency devices such as microwave generators, sensitive detectors or mixers and voltage standard [1,2]. Due to the large energy gap of HTSC, the working frequency range of such devices has expanded to the THz frequency range [3]. However, for some applications the performances of the HTSC devices are limited by fairly low impedance of the JJ. One possible way to solve this problem is to replace a single JJ by a chain or an array of JJs combined with planar coupling structures. We report on a modeling of a broadband receiving system based on a meander series of YBaCuO grain boundary junctions integrated into a log-periodic antenna. The technique for calculating the receiving properties of JJs in the direct detection regime was developed and applied. At the first stage, electromagnetic modeling of several geometries of antennas was carried out for effective receiving in the frequency range 50 - 800 GHz. The electromagnetic properties of the systems are investigated, namely the amplitude-frequency characteristic and the beam pattern. For the chosen antenna geometry, the cases of a series of junctions integrated as a receiving element were considered; the fraction of the absorbed power in each JJ is investigated and it is shown that the use of 7 junctions makes it possible to increase the total absorbed power at a fixed frequency of 250 GHz by a factor of 2.3. At the second stage, by solving a system of second-order differential equations related through the equation for the antenna, the characteristics of the detector at bias current regime were calculated: current-voltage characteristic, operating point, responsivity, noise and noise equivalent power (NEP). It is shown that the use of a series chain of junctions allows to improve the responsivity by a factor of 2.5, NEP value by a factor of 1.5, and the dynamic range by a factor of 6-8. As a result, for the standard technology of YBaCuO magnetron sputtering on a bicrystal substrate for a temperature of 77 K, NEP in the region of 3·10-13 W/√Hz is obtained. The work is supported by the RSF (Project No. 20-79-10384).