This article presents a monostatic Single Input Single Output (SISO) joint communication and sensing (JCAS) system based on Impulse Radio Ultra-Wide Bandwidth (IR-UWB) technology operating in the millimeter-wave (mmW) spectrum. The architecture relies on synchronized mmW oscillations and pulsed quench signals to achieve stable pulse-to-pulse phase. The modulation scheme is obtained by a transformation of a n-states pulse position modulation (n-PPM) into a n-state phase shift keying (n-PSK) modulation, which ensures ultra-stable and low-power mmW pulse generation. Proof of concept of this JCAS sytem has been developed, based on a transmitter unit with a 65 nm CMOS SOI chipset including antenna achieving 2 dBm effective radiated power (ERP). Coherent integration capabilities help achieve high Signal-to-Noise Ratio (SNR), even with pulse repetition frequency (PRF). Measurement results show that this IR-UWB JCAS architecture achieves a data rate of 200 Mbps, with high accuracy (sub-mm) ranging and motion detection.