This letter presents a broadband multistage low-noise amplifier (LNA) in a 0.15- $\mu $ m GaAs pseudomorphic high-electron-mobility (pHEMT) process. The LNA employs multiple bandwidth extension techniques, including cascode, feedback, and gain-enhanced source–drain coupled line (SDCL). The SDCL enhances the gain by combining the source and drain signals and compensates the gain roll-off of the amplifier, which is first proposed in this letter to our knowledge. These techniques are adopted in a three-stage monolithic microwave integrated circuit (MMIC) LNA, achieving a wide bandwidth with high gain. The measured results show that the LNA obtains an average gain of 24.7 dB and a noise figure (NF) of 1.7–2.8 dB in 0.5–24 GHz, with a compact chip area of only 1.47 mm $^{2}$ .

This paper analyzes the main factors limiting the bandwidth expansion of low-noise amplifiers (LNA) and designs a broadband LNA with a bandwidth of 2-40.5 GHz. The LNA is designed using multiple bandwidth expansion methods, including cascode, resistance feedback, and cascode Darlington amplifier. The amplitude-frequency characteristics and bandwidth expansion principle of the three structures are studied theoretically based on the small-signal equivalent circuit model. Thanks to these techniques, a three-stage LNA is designed in a 0.15-μm GaAs pseudomorphic high-electron-mobility (pHEMT) process. The measured results show that the designed LNA achieves an average gain of 21.6 dB in 2-40.5 GHz while maintaining a noise figure (NF) below 3.6 dB. The measured output 1-dB gain compression point (OP1 dB) is from 4.5 to 12.8 dBm and the input/output return loss are better than 5 dB. The chip area is only 1.57 mm ² , including input and output test pads.

A multiple feedback-based technique is presented to improve broadband simultaneous noise and impedance matching (BSNIM) performance in a GaAs low-noise amplifier (LNA). It consists of dual reactive feedback for the first stage and frequencydependent feedback loops (FDFLs) for the succeeding stages. Compared to existing BSNIM technologies, the proposed method completes the theoretical derivation of the required load and can provide flexible solutions, which effectively increases the optimization opportunity. Besides, in order to achieve the required load, a structure composed of low-Q high order LC-ladder networks and FDFLs are introduced, which greatly reduce the difficulty of impedance conversion. The detailed strategies for BSNIM are also given. To verify feasibility, a 6-14 GHz three-stage common-source LNA has been fabricated via 0.15-μm GaAs pHEMT process, with a measured gain of 26.8 ± 0.75 dB, a minimum noise of 1.21 dB, and S11 of less than -15 dB throughout the entire operating band.

In this letter, a novel multiconductor coupled line (MCL) balun is presented for the implementation of a wideband double balanced mixer (DBM). The proposed balun utilizes an artificial transmission line (ATL) (composed of periodical shunt stubs), and manages to shorten the length by 65.1% compared with the three-line balun. Besides, in order to provide a point for intermediate frequency (IF) extraction, two sections of coupled lines are exclusively added behind local oscillator (LO) balun. And this structure also transmits LO signals to the diodes for mixing. Through the aforementioned operations, a compact balun and an 18–50 GHz mixer in 0.15- $\mu$ m GaAs pseudomorphic high electron mobility transistor (p-HEMT) process are designed. The measured results show that within the operation frequency, the phase and amplitude difference of the balun are lower than 3.5 $^{\circ}$ and 1.1 dB, respectively. The mixer dB conversion loss (CL) and 33 dB LO-to-RF isolation under 15 dBm LO power. The monolithic microwave integrated circuit (MMIC) area is 0.96 $\times$ 1.68 mm $^{2}$ , including all pads.

This paper presents a high-accuracy multifunction chip (MFC) with amplitude and phase control in X-band. The MFC is designed with a common leg structure and incorporates a 6-bit attenuator (ATT), a 6-bit phase shifter (PS), two gain compensation amplifiers (GCAs), three single pole double throw switches (SPDTs), and fourteen logic control circuits. However, cascading these blocks causes the change of the terminal impedances of the ATT and PS, which is detrimental to the accuracy. To solve this problem, the extra tunable interstage matching networks (IMNs) are introduced between each ATT and PS cell to alleviate the terminal impedance changes. The compensation capacitances are also applied to ATT to reduce the insertion phase shift. The receive and transmit modes switching is achieved by using four SPDTs. In addition, the resistance feedback is used in GCAs to compensate for passive losses and provide gain to the MFC. To validate the design scheme, the proposed MFC is fabricated in 0.15-μm GaAs pseudomorphic high-electron-mobility transistor (pHEMT) process. The measured results show that the MFC has excellent accuracy due to the introduction of IMNs. In the range of 8-11 GHz, the measured maximum root-mean-square (RMS) amplitude error of the MFC is less than 0.28 dB, and the maximum RMS phase error is less than 3.3°. Moreover, the MFC is achieved with a compact layout of 4.3 mm × 2.85 mm. Excellent performance and compact size make the MFC greatly potential in spaceborne phased array applications.

In this brief, a novel reduced-size 1800 hybrid is presented to implement a U-band subharmonic mixer (SHM) via a 0.15-μm GaAs pHEMT process. The isolations between Σ-port and -port of the proposed 1800 hybrid are significantly enhanced by two structures: one is a compact multiconductor edge-coupled line balun with artificial transmission line and the other is an in-phase power divider composed of λLO/4 coupled line. As a proof-of-principle demonstration, a single balanced SHM with an antiparallel diode pair configuration is designed and fabricated, which exhibits a conversion gain of -12.25 dB 1 1.55 dB within the operating RF frequency of 40 to 60 GHz under 14 dBm LO pumping power. The improved isolations of LO-to-RF and 2LO-to-RF are 33 to 47 dB and 44 to 57 dB, respectively. The measured results surpass previously reported performance of SHMs.