  The scalar Higgs portal is a compelling model of dark matter (DM) in which a
renormalizable coupling with the Higgs boson provides the connection between
the visible world and the dark sector. In this paper we investigate the
constraint placed on the parameter space of this model by the antiproton data.
Due to the fact that the antiproton-to-proton ratio has relative less
systematic uncertainties than the antiproton absolute flux, we propose and
explore the possibility to combine all the available $\bar{p}/p$ data.
Following this approach, we are able to obtain stronger limits if compared with
the existing literature. In particular, we show that most of the parameter
space close to the Higgs resonance is ruled out by our analysis. Furthermore,
by studying the reach of the future AMS-02 antiproton and antideuteron data, we
argue that a DM mass of $\mathcal{O}(150)$ GeV offers a promising discovery
potential. The method of combining all the antiproton-to-proton ratio data
proposed in this paper is quite general, and can be straightforwardly applied
to other models.
