A wireless data link operating at a carrier frequency of 220 GHz is supporting a data rate of up to 25 Gbit/s in on-off-keyed PRBS as well as complex 256-QAM (quadrature amplitude modulation) transmission. The millimeter-wave transmit and receive frontends consist of active multi-functional millimeter-wave microwave integrated circuits (MMICs), realized in 50 nm mHEMT technology and packaged into split-block waveguide modules. The paper presents system considerations for wireless links in the 200-300-GHz range, discusses the design and performance of dedicated broadband transmit and receive MMICs, and presents link experiments. With an RF transmit power of -3.4-1.4 dBm in the IF frequency range from 0 to 20 GHz , a receiver conversion gain of better than -4.8 dB up to 270 GHz and an estimated noise figure of less than 7.5 dB at 220 GHz, a 231-1 PRBS with a data rate of up to 25 Gbit/s is transmitted over 50 cm and received with an eye diagram quality factor >;3 . At 10 Gbit/s, an uncorrected bit-error rate (BER) of 1.6·10-9 is measured over a distance of 2 m. A 256-QAM signal with approx. 14 Mbit/s is received with an uncorrected BER of 9.1·10-4.