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This brief proposes a broadband flat-gain Doherty power amplifier (DPA) for 5G new radio (NR) mobile handsets. It is implemented by the heterogeneous integration of GaAs HBT process for PA die and 6-layer laminate for output network. To realize wideband Doherty-operation, an on-laminate transformer with three $\pi $ -shaped networks is designed. Meanwhile, the parallel coupling of on-chip spiral inductors is introduced into input quadrature power splitter and interstage matching network to extend bandwidth and reduce size. Mechanism of the proposed DPA is analyzed and a prototype is implemented for verification. For continuous-wave (CW) signal, saturation power of 36-dBm and comparable peak power added efficiency (PAE) of the DPA at 3.3, 3.75 and 4.2 GHz are realized. Within the 6-dB power back-off (PBO) range, the measured PAE is higher than 27%. Flat gain within n77 band (3.3 – 4.2 GHz) is obtained, varying from 25.8 dB to 27.2 dB. Under the excitation of 5G NR 100-MHz QPSK signal, the proposed DPA delivers a PAE of 26.2% – 30.3% with the averaged output power of 30 dBm in n77 band. The corresponding lower and upper adjacent channel leakage ratios (ACLRs) are measured from −32.1 dBc to −36.5 dBc without digital pre-distortion (DPD). The size of die is $1.34\times1.44$ mm2, and the occupied core area of laminate is $1.69\times3.85$ mm2.

This paper presents a three-stage wideband LNA with gain switching technique designed for 5G millimeter-wave applications operating at 23.6-46.5 GHz. By deriving an analytical equation of input impedance and noise matching, a two-pole matching network based on ladder transformer is introduced. The coupling between the transformers can be used to control the two poles of S11 and simultaneously match the source impedance to the optimized noise impedance, achieving broadband input matching and low noise figure (NF). A 24 dB gain tuning range with 6 dB per step has been designed to accommodate different input power level for automatic gain control (AGC). The gain control is implemented with current slicing at the 2nd and 3rd stages, which can keep input/output impedance nearly constant during gain switching. The proposed wideband LNA has been fabricated in 28-nm bulk CMOS process with a chip size of only 0.13 mm2. Measured results show a peak gain of 23 dB within a 3-dB bandwidth from 23.6 to 46.5 GHz, with S11 better than −10 dB over the bandwidth. The measured NF is 2.2 – 3.7 dB with an average of 3 dB. The input 1 dB gain compression point (IP1dB) ranges from −27 to −23.8 dBm throughout the gain bandwidth. Moreover, the measured gain can be switched with value of 21.5/14.9/9.1/2.9/−3 dB, and the corresponding NF and IP1dB are 3.7/4.9/7.9/12.8/14.3 dB and −23.8/−19.5/−14.8/ −13.1/−8.8 dBm at 33 GHz, respectively. This design is suitable for wideband 5G millimeter-wave communication.

This article introduces a filtering technique applied to the design of a wideband and high-gain Fabry–Pérot cavity (FPC) antenna for millimeter-wave (mm-wave) applications. The suggested method is to insert a low-pass frequency selective surface (FSS) into an FPC with intrinsic high-pass feeding source. By a combination of the two components (FSS and source), bandpass response can be generated effectively while maintaining high-gain performances realized by the proposed FPC. Both the proposed high-pass source and low-pass FSS exhibit wideband characteristics with tunable radiation nulls. Combined with a multimode resonant cavity structure, wideband performances can be achieved for the total antenna. For demonstration, a filtering FPC antenna operating at 30 GHz is designed, fabricated, and measured. The antenna consists of a low-pass feeding source, a modified ground, a partially reflective surface (PRS), and a low-pass FSS. Measured results show that the operating bandwidth of the antenna is from 22 to 30.5 GHz for the refection coefficient $\le -10$ dB. It realizes a flat in- band gain with a peak gain of 19.5 dBi. The in- band radiation patterns are stable, whereas the out-of-band radiation suppression level is around 14 dB.

This paper presents compact 24–35 GHz filtering low noise amplifier (LNA) and filtering switch in 28-nm CMOS technology. A compact mixed magnetic-electric coupling circuit is designed, where a transmission zero is introduced out of the passband due to the cancellation of the magnetic and electric couplings. By analyzing the impedance characteristics, this structure can be designed with the impedance conversion function to replace the widely used transformers in integrated circuit designs. It shows the advantages of easy control of coupling coefficient and out-of-band rejection. Then, an LNA employing the magnetic-electric coupling circuits as impedance matching networks is designed. Image rejection can be achieved without increasing the circuit area. Moreover, by loading transistors to this mixed magnetic-electric coupling circuit, the input impedance can be controlled by the parasitic components of the transistor. Subsequently, a filter passband can be switched on and off, realizing a very compact filtering single-pole single-throw (SPST) switch. The fabricated filtering LNA is measured with a 3-dB bandwidth of 24–35 GHz, a noise figure (NF) of 2.4-3.6 dB, a maximum gain of 22 dB, and suppression of better than 25 dBc below 18 GHz. The filtering switch shows a minimum on-state loss of 2.1 dB at 28.6 GHz with better than 12.9 dB rejection below 16 GHz and off-state isolation of higher than 19 dB.