Book excerpt: A 68-82 GHz highly integrated, wideband linear receiver is demonstrated. The receiver achieves a maximum gain of 28.1 dB, a NF of 8 dB, and an input-referred 1 dB gain compression point (IP1dB) of -23.6 dBm at 77 GHz while dissipating 413 mW. The receiver enables applications within the band to share and reuse the same front-end chip. To further explore the opportunity at higher frequency, an 81-92.6 GHz low-noise amplifier is demonstrated with a gain of 21 dB, a NF of 9 dB, and an IP1dB of -18.8 dBm. On the other hand, critical transmitter building blocks, such as an up-conversion mixer has also been investigated. A highly linear double-balanced active up-conversion mixer based upon multi-tanh triplet technique has been validated to show a single sideband (SSB) power conversion gain of 5.1 dB and an output-referred 1 dB gain compression point (OP1dB) of -5.8 dBm at 77 GHz. Finally, a high-power signal generation at submillimeter-wave is demonstrated and fabricated in InGaAs/InP D-HBT technology. The second harmonic push-push oscillator shows an output power of 0 dBm at 200 GHz, which opens a new frontier for applications, such as weather observation radar, chemical, and tumor detections, and next-generation optical systems. By using an even higher order harmonic generation, THz signal sources can be expected in the very near future.