Due to rapidly growing of radar sensor market such as object range detection sensors, collision-avoid sensors, speed-detection sensors, traffic-control sensors, health-care sensors, and human motion detection sensors, microwave and millimeter-wave radars have paid much attention. For these applications, high per-formance, small size, and low cost are crucial for the radars. Especially, in automotive safety applications, radar sensor is the key component to improve the convenience and the safety of the automobile. Compared with other range sensor such as ultrasonic and vision sensor, the radar sensor has the benefit in terms of ro-bustness against the unexpected circumstances such as fog, rain, and light. However, the cost inefficiency is the bottleneck of the radar sensor in automotive sensors. Furthermore, at least 6 to 10 short range and medium range radars are required to provide the $360^\circ$ safety with 0.1meter and 1meter resolution respectively. These features restrict the penetration of radar sensors in the automobile. Thus, development of cost effective radar sensor are urgent.
In K-band, frequency allocation for UWB radar is at least more than several GHz with extremely low output power constraint. The range resolution is directly determined by the bandwidth, thus the K-band UWB operation has the advantage in terms of range resolution at the short range. On the other hand, the bandwidth of FMCW radar allocated in K-band is excessively narrow. However, in terms of the transmit power and nar-row band nature, its maximum detectable range is 2~3 times longer than that of the UWB radar.
Thus, this thesis proposes K-band dual-mode radar including FMCW and UWB mode and the main contribution is to implement the K-band Radar transmitter suitable for dual-mode radar and to propose the key sub-circuits appropriate for dual-mode radar. The proposed radar concept has the benefits of both mode of radar, which suggests the possibility of short range detection capability with high range resolution and of medium range detection capability with moderate range resolution. Also, to improve the performance of both operation modes, the pulse compression technique using binary phase modulation schemes in the UWB mode and the closed loop linearization technique using Phase-locked loop in the FMCW mode is implemented.
The proposed dual mode radar transmitter is composed of RF front-end integrated in a single chip and external PLL using commercial product. The RF front-end is composed of the 24/26GHz dual band VCO using high Q asymmetric transformer, wideband frequency divider chain including dual band differential injection locking frequency divider, pulse former and wideband output balun stage. For 0.1meter range resolution, we propose and demonstrate the pulse former adopting the current steering for fast switching capability. The proposed pulse former operates as a switch to generate a pulse modulated carrier signal and a bi-phase modulator for pulse compression. The TX leakage is cancelled by pulse former’s own nature, ideally perfect leakage cancellation. The pulse former also operates as a differential gain amplifier for FMCW mode.
The dual-mode radar transmitter is fully integrated on a single chip using TSMC 0.13- $\mu m$ 1-poly 8-metal CMOS process, which provides a 3.35 um-thick Cu top metal layer. The maximum bandwidth of the output spectrum is more than 4 GHz in pulse compression mode, thus the expected range resolution is more than 0.075 meter. The operation frequency of the dual mode transmitter tunes from 23.885 GHz to 24.724 GHz for low band and 25.758 GHz to 26.801 GHz for high band which covers 24/26 GHz UWB band and 24 GHz FMCW band. The FMCW mode signal using external PLL is modulated linearly using Triangular wave-form and the absolute error is below 1.5MHz. The -5dBm output peak power is measured in the condition of wire bonding with 108mW power consumption. Finally, the leakage power as low as -59dBm is achieved.
The proposed dual-mode radar concept is demonstrated using dual-mode receiver which is integrated in a single chip with the transmitter. For FMCW mode, 42meter of maximum detection range and 0.6meter of range resolution are measured. In UWB mode, the demonstration is performed using a delay line based meas-urement. The DC power consumption of the dual-mode radar transceiver is 262mW.