State space model

[nkxl]

I want to estimate the following model with Kalman filter:

Y(t)=X(t)+v(t)
X(t)=a+b*X(t-1)+w(t).

In RATS, the state equition doesn't have the intercept a. My question is how to deal with the intercept a in the state equation in RATS form: X(t)=c'X(t-1)+w(t)?

Many thanks

[TomDoan]

The Z option on DLM is used for shifts in the state equation like this

[nkxl]

Thanks a lot!