The coinbase transaction is a special transaction that has to satisfy the following:
Only has 1 input
The input is using 0x0000000000000000000000000000000000000000000000000000000000000000 as its txid and 0xFFFFFFFF as its index (vout)
The signature script of this input has to have a length between 2 and 100 (2<= length <=100)
Any block after BIP-34 ...