A 6-bit high-accuracy active phase shifter is developed in 0.13-μm CMOS technology for Ku-band phased arrays. Improved transformer balun with wriggly stub is applied to split the single input to differential and achieve high balance with reduced chip area. Two-stage polyphase filter (PPF) generates broadband I/Q signals with high accuracy. A main digital-to-analog convertor (DAC) controls the I/Q amplitude to achieve 6-bit phase resolution, while an auxiliary DAC compensates the amplitude/phase error introduced by balun and PPF. Consequently, high resolution along with low phase/gain error can be achieved. The phase shifter shows measured rms phase error of <4° at 12-18 GHz and <3° at 13-18 GHz. The measured mean gain is -2.5-1 dB, and the rms gain error is <0.9 dB at 12-18 GHz. The total power consumption is 37.5 mW, and chip size is $0.75 x 0.32$ mm$²$ excluding pads.

In this paper, a slotted conical patch connected to a small triangular patch multiband antenna for both microwave and millimeter-wave applications is presented. The designed antenna has three characteristics. The proposed antenna is a multiband, having a compact size of 0.35λ₀ × 0.35λ₀ × 0.004λ₀ at its lowest operational frequency, i.e., 2.4 GHz, and more importantly, it can cover both the microwave and millimeter-wave bands with a single feeding. According to the −10 dB matching bandwidth, experimental results show that the antenna operates at (2.450–2.495) GHz, (5.0–6.3) GHz, and (23–28) GHz. The reduced size, simple design, and multiband large bandwidth are some of the advantages over the reported designs in the latest literature. Both simulated and experimental results show a good agreement, and the proposed antenna can be used for wireless local area network (WLAN) applications and fifth-generation (5G) wireless communication devices.

As a dedicated communication protocol for Internet-of-Things, narrowband internet of things (NB-IoT) needs to establish the communication link rapidly and reduce retransmissions as much as possible to achieve low power consumption and stable performance. To achieve these targets, the low-power scheme of the initial cell search and frequency tracking is investigated in this paper. The cell search process can be subdivided into narrowband primary synchronization signal (NPSS) detection and narrowband secondary synchronization signal (NSSS) detection. We present an NPSS detection method whose timing metric is composed of symbol-wise autocorrelation and a dedicated normalization factor. After the detection of NPSS, the symbol timing and fractional frequency offset estimation is implemented in a resource-efficient way. NSSS detection is conducted in the frequency domain with a calculation-reduced algorithm based on the features of NSSS sequences. To compensate the accumulated frequency offset during uplink transmission, a pilot-aided rapid frequency tracking algorithm is proposed. The simulation results of the proposed cell search scheme are outstanding in both normal coverage and extended coverage NB-IoT scenarios, and the accumulated frequency offset can be estimated with high efficiency.

An analytical approach based on the thermoelectrical analogy to calculate the maximum channel temperature of multifinger AlGaN/GaN HEMT transistor is presented. The model is capable of predicting the maximum channel temperature, including the impact of the nonlinearity of thermal conductivity for every single gate with excellent accuracy. The model remains invariant under device scaling up and down and gives an accurate estimation for any number of gate fingers. Furthermore, the temperature field fluctuation due to the interaction between gates and variation in the number of gate fingers can be easily identified by the model. The validity of the proposed approach has been testified by comparing the results with those from infrared spectroscopy and numerical simulations for different AlGaN/GaN HEMT transistors with a different number of gates. The significance of models is justified by its ability to evaluate the temperature of any gate finger with high accuracy. Such an ability is particularly highly important while optimizing the structure layout and cooling system for high-power AlGaN/GaN HEMT transistors. The model can serve as a powerful tool for power devices and microwave IC designers and can be easily incorporated into SPICE empirical or physical-based models.