The light source mentioned in recent quantum radar scheme, in which the quantum entanglement effect of entangled photons is used to realize three-dimensional quantum enhancement, has been analyzed andthe possible solution is also discussed. In the new quantum radar scheme, positive correlation in frequency and transverse momentum can be used to realize three-dimensional quantum enhancement. Taking two-photon states as an example, firstly, preparationof the positively correlated state of frequency or momentum is investigated separately, and then on this basis, the preparation of entangled photon sources with positive correlation of both frequency and momentum is further discussed. Numerical simulation shows that through a spontaneous parametric down conversion process, the entangled photon source with positive correlation in frequency and transverse momentum can be generated by using a tightly focused pulsed pump light.