Carrier generation at receiver in DSB-SC modulation?
You have to use a coherent detector and not any old arbitrary oscillator module or crystal that is stamped with the correct frequency. It has to be phase coherent i.e. exactly the same frequency and a stable (relatively) phase. This is why squaring or Costas loops are used. Costas loop: -



Without the continuous presence of a carrier (i.e. the carrier is suppressed) you have to use these methods.

The band-pass filter used in a squaring coherent carrier detection system does need to be broadly centred at the carrier frequency but it must have a pass-band that is wide enough so that errors are not significant. 

A filter does not make a local oscillator signal phase coherent - the act of squaring the signal and then removing DC and double frequency components gives you phase coherence. The PLL is superfluous to a squaring coherent detector BTW.