  Superconducting qubits provide a promising platform for physically realising
quantum computers at scale. Such devices require precision control at microwave
frequencies. Common practice is to synthesise such control signals using IQ
modulation, requiring calibration of a in-phase (I) and quadrature (Q) signals
alongside two DC offsets to generate pure tones. This paper presents an
economic physical implementation of an alternative method referred to as double
upconversion which requires considerably less hardware calibration and physical
resources to operate a qubit. A physical circuit was created using standard PCB
design techniques for microstrip filters and two common RF mixers. This circuit
was then utilised to successfully control a superconducting transmon qubit.
When using proper RF shielding, qubit tones were demonstrated with over 70dB of
spurious-free dynamic range across the entire operational spectrum of a
transmon qubit.
