This work presents a low temperature co-fired ceramic (LTCC) technology based system-in-package (SiP) operating beyond 100 GHz. The SiP encloses a semiconductor transceiver chip in a pea-sized LTCC package. The SiP is efficient and robust in terms of its electrical, thermal and mechanical characteristics. Moreover, it is low-cost and requires only standard manufacturing and assembly techniques. Finally, two fully-integrated 122 GHz radar sensors are demonstrated in LTCC technology.