To address the issues of large size and integration difficulty in traditional Ku-band bandpass filters, this paper proposes a novel 8th-order SIW bandpass filter utilizing LTCC technology. The filter features an effective coupling topology, with eight SIW cavities interconnected through electromagnetic hybrid coupling, achieving wide bandwidth and high out-of-band rejection. To reduce overall volume, the eight SIW cavities are divided into two layers, with four cavities on each layer. By designing a coupling matrix and adjusting the coupling coefficients between the cavities, the filter"s volume is significantly reduced. Coplanar waveguide coupling is employed at the microstrip and SIW junctions, introducing two transmission zeros in the out-of-band region to suppress spurious passbands and further enhance out-of-band performance. Experimental results show that the filter has a bandwidth of approximately 13.3-17.2 GHz, a relative bandwidth (FBW) of 26%, an in-band insertion loss of less than -2.2 dB, and out-of-band rejection greater than -20 dB in the 18-20 GHz range.