Microwave And Millimeter Wave Ultra-wideband Low Noise Amplifier Monolithic Technology

The Monolithic Microwave Integrated Circuits (MMICs) are microwave integrated circuits with both active devices and passive structures fabricated on one semi-conductor. MMIC circuits show reduced size and weight, higher reliability, good consistency, low parasitics and low cost by mass-production. These superiorities make it the most attractive solution for many military and civil applications. Low noise amplifier (LNA) is the first stage of a receiver system which dominates the overall system noise performance. However broad bandwidth LNAs are difficult for millimeter-wave applications. In this paper, a LNA covering both K- and Ka-band is designed based on MMIC technology with good gain flatness.Firstly, the working mechanism and small signal equivalent circuit of a pHEMT device is studied. Optimal gate width and gate fingers are obtained by noise and gain performance analysis with different device structures.Balanced topology is chosen in order to get good noise performance and input match simultaneously. Then a three stage single-ended amplifier is designed. Source series negative feedback is used to move the optimal noise impedance close to the input match impedance which greatly alleviates the contradiction between noise and input VSWR. Lossy match method is applied to make compensation for the gain roll off of the transistors. Thus flat small signal gain response is achieved.Finally, a three stages single-ended LNA was fabricated using 0.15μm GaAs pHEMT technology. This MMIC LNA achieves 3 dB average noise figure with 18 dB associate gain from 21~40 GHz. The gain flatness is within±2.5 dB. Input and output return loss is better than -9 dB.This MMIC has very flat small signal gain over a broad bandwidth. It is well suited for electronic warfare, wideband ultra speed communication systems, test instrumentation and et al.