ch in turn will improve the user experience. Chapter 5 5.8 mmWave Transceiver and Antenna Design Considerations The RF PA plays an important role in wireless communication systems. The emerging 5G technologies have increased the demand for broadband, highly linear, and efficient PAs for various classes of base stations and devices. While amplifying the signal, the PA nonlinear- ity may cause some signal distortion which need to be minimized in order to meet the trans- mitter RF requirements. Therefore, PA attributes such as linearity, gain, flatness, efficiency, AM-AM/AM-PM distortion are important design parameters that must be taken into con- sideration. The GaAs E-mode pHEMT30 technology inherits many advantages of D-mode pHEMT technology and exhibits single power, high span, and high linearity characteristics. The E-mode pHEMT device has a very low switching voltage, SO there is no limit on the offset margin. An (E-mode) 0.15 um GaAs pHEMT contains 17 masks and over 200 pro- cess steps. Each of these steps needs repeatable experiment to ensure the entire process is reliable and commercial grade [26]. The GaAs-based devices have dominated most of the market due to the maturity of the technology in the microwave frequency bands. However, an InP-device has a higher break- down voltage, higher average electron velocity, larger discontinuity in the bandgap at the interface of InAlAs/InGaAs heterojunction, higher two-dimensional electron gas (2DEG) concentration, and higher electron mobility in the channel, making it more suitable for A high-electron-mobility transistor (HEMT) is a field-effect transistor incorporating a junction between two materials with different band gaps (i.e., a heterojunction) as the channel instead of a doped region (as is gener- ally the case for MOSFET). A commonly used material combination is GaAs with AlGaAs, depending on the application of the device. Devices incorporating more indium generally show better high-frequency perfor- mance, while in recent years, gallium nitride HEMTs have 