A Differential K-Band UWB Transmitter for Short Range Radar Application with Continuous Running Local Oscillator

Abstract—The design of a differential K-band UWB (Ultra Wideband) Short Range Radar (SRR) transmitter in 90 nm bulk CMOS is presented. Implementation of SRRs in deep submicron CMOS technology is attractive, in terms of cost and monolithic integration of RF font-end with signal baseband processor. The transmitted pulse bandwidth limits the range resolution of the radar system. Due to the wide bandwidth and high frequency of CMOS implementation, UWB transmitters in the K-band are challenging to make and critical for the system performance. The design presented is based on frequency up conversion using a double balanced mixer. The differential output is combined and matched with the antenna using an on-chip balun. To mitigate local oscillator (LO) leakage of UWB differential transmitters we propose a new Pulse Generator (PG) design. A switching technique is used to minimize the LO leakage enabling continuous wave operation with very wideband pulses. Measurements of the proposed transmitter achieves a −10 dB bandwidth (BW) of 5GHz. Using a Pulse Repetition Frequency (PRF) of 100MHz the peak average power is −40 dBm. Compared to measured transmitter performance of a single balanced mixer design, the LO leakage of this dual balanced mixer is decreased with more than 20 dB, and is lower than the peak average power of the pulse. It consumes 11mW from a 1.2V supply where 6 mW is from the LO.