  Engineering the admittance of external environments connected to
superconducting qubits is essential, as increasing the measurement speed
introduces spontaneous emission loss to superconducting qubits, known as
Purcell loss. Here, we report a broad bandwidth Purcell filter design within a
small footprint, which effectively suppresses Purcell loss without losing the
fast measurement speed. We characterize the filter's frequency response at 4.3
K and also estimate Purcell loss suppression by finite-element-method
simulations of superconducting planar circuit layouts with the proposed filter
design. The measured bandwidth is over 790 MHz within 0.29 mm$^2$ while the
estimated lifetime enhancement can be over 5000 times with multiple Purcell
filters. The presented filter design is expected to be easily integrated on
existing superconducting quantum circuits for fast and multiplexed readout
without occupying large footprint.
