The rocket frames of the HQ-9 appear similar to the 5V55 missile used with the earlier S-300 complex, but it is said that the fuel used on the HQ-9, at least on the later versions, is the one used on the KT-1, or the solid fuel rocket boosters used to launch satellites to space.
Much like the HQ-16 started from the Buk, the HQ-9 started from a common root with the S-300 but has deviated from the S-300 in terms of guidance, electronics and sensors.
The HT-233 fire control radar is similar to the Russian Flaplid and Tombstone in concept, but appears different in the frequency range, using C-band instead of X-band, like the MPQ-53 of the Patriot. However, the MPQ-53 is designed to work as an all in one unit, although capable of cooperation with other radars. The HT-233 is designed with work with other radars foremost, like Flaplid, but also like Flaplid, it can work on its own if the paired search radars are taken down. If the HT-233 engagement radar of the HQ-9 works on C-band, this would mean its TVM guidance system would work on this band, like the Patriot missile does. (IMO this data needs to be revisited.) In commercial brochures of the FD-2000 export version of the HQ-9, it is also mentioned the missile guidance system having an active capability.
Both HQ-9 and S-300 systems rely on entirely different sets of search radars of which there are a handful and not going to say too much about them as it will TLDR. Similarities in these radars are more due to working on the same common principles of design rather than copying the other. Needless to say, the Big Bird search radar used with the S-300PMU, one of the more commonly used search radars used with the S-300 complex has a very unique spaced reflective type phase array design, and even though this radar unit was part of the bundle sold by Russia to China's S-300 purchases with China having a number of these samples, this unit is not copied.
Instead, the HQ-9 system adopted an AESA for one of its search radars, this the Type 305A.
