  We propose a scheme to implement a tunable, wide frequency-band dissipative
environment using a double chain of Josephson junctions. The two parallel
chains consist of identical SQUIDs, with magnetic-flux tunable inductance,
coupled to each other at each node via a capacitance much larger than the
junction capacitance. Thanks to this capacitive coupling, the system sustains
electromagnetic modes with a wide frequency dispersion. The internal quality
factor of the modes is maintained as high as possible, and the damping is
introduced by a uniform coupling of the modes to a transmission line, itself
connected to an amplification and readout circuit. For sufficiently long
chains, containing several thousands of junctions, the resulting admittance is
a smooth function versus frequency in the microwave domain, and its effective
dissipation can be continuously monitored by recording the emitted radiation in
the transmission line. We show that by varying in-situ the SQUIDs' inductance,
the double chain can operate as tunable ohmic resistor in a frequency band
spanning up to one GHz, with a resistance that can be swept through values
comparable to the resistance quantum R_q = (h/4e^2) ~ 6.5 k{\Omega}. We argue
that the circuit complexity is within reach using current Josephson junction
technology.
