  In the past years quasi-conformal mapping has been typically used to design
broadband electromagnetic cloaks. However, this technique has some inherit
practical limitations such as the lateral beam shift, rendering the device
visible or difficult to hide a large object. In this work we circumvent these
issues by using strict conformal mapping to build the first isotropic cloak.
Microwave near-field measurement shows that our device (with dielectric
constant larger than unity everywhere) has a very good cloaking performance and
a broad frequency response. The present dielectric approach could be
technically extended to the fabrication of other conformal devices at higher
frequencies.
