  Working in a way that passively receives the electromagnetic radiation of
celestial body, the radio telescope is easily disturbed by external radio
frequency interference (RFI) as well as the electromagnetic interference (EMI)
generated by electric and electronic components operating at telescope site.
The quantitative analysis for these interferences must be taken into account
carefully for further electromagnetic protection of the radio telescope. In
this paper, based on the electromagnetic topology (EMT) theory, a hybrid method
that combines Baum-Liu-Tesche (BLT) equation and transfer function is proposed.
In this method, the coupling path of radio telescope is divided into strong
coupling and weak coupling sub-paths, and the coupling intensity criterion is
proposed by analyzing the conditions that BLT equation simplifies to transfer
function. According to the coupling intensity criterion, the topological model
of a typical radio telescope system is established. The proposed method is used
to solve the interference response of the radio telescope system by analyzing
the subsystems with different coupling modes respectively and then integrating
the responses of the subsystems as the response of the entire system. The
validity of the proposed method is verified numerically. The results indicate
that the proposed method, compared with the direct solving method, reduces the
difficulty and improves the efficiency of the interference prediction.
