Broadband compact InGaAs pin 5-bit digital attenuator using π-type resistive network

Abstract

A broadband compact InGaAs pin 5-bit digital attenuator using a p-type resistive network is demonstrated. The proposed 5-bit digital attenuator is composed of p-type resistive networks for good input/ output matching and accurate attenuation characteristics. The fabricated attenuator MMIC has good performance characteristics, such as an insertion loss less than 11.5 dB and a small RMS amplitude error of 2.3 dB at the broadband frequency range of 7 -40 GHz. In addition, the overall chip size, which is significantly reduced by using the developed multilayer structure, is only 1.59 × 0.84 mm 2 .Introduction: An attenuator is a network that reduces input power by a predetermined ratio while matching input and output impedances. Microwave attenuators have been widely used in high-frequency communication systems such as automotive collision avoidance, optical communication, and phased-array radar applications [1,2]. Most monolithic microwave integrated circuit (MMIC)-based attenuators have been developed by using a GaAs-based FET technology for military applications. However, owing to limitations of the device performance, the RF characteristics and bandwidth are restricted [3][4][5]. From this standpoint, pin diodes with optimised junction areas have been used with better performance characteristics over FET devices in terms of high switching cutoff frequency, small distortion and high power handling capability [6,7]. In addition, InGaAs pin diodes based on InP-based material systems have several advantageous features, such as low turn-on voltage, fast switching time, and good RF performance [8].In this work, a broadband InGaAs pin 5-bit digital attenuator using a p-type network has been designed and fabricated. Based on the circuit schematic of a p-type resistive network, the operating principle of the proposed InGaAs pin diode based attenuator is discussed. The attenuator MMIC has been implemented by using a BCB-based multilayer MMIC technology and its microwave performance has been characterised by on-wafer test setups.

An X‐band substrate integrated waveguide attenuator

“…The shape of a SIW attenuator prototype is shown in Figure . The three major SMD chip‐type resistors are located on the etched top layer, all together hired for structuring resistive π‐network, which works better than T‐type network in a view of return loss across wide bandwidth . The series resistor (Rs) bridges the electrical gap of the slotted SIW structure.…”

“…A resistive attenuator is widely used for RF and microwave system. It reduces the signal level down to the desired level, and helps improve the matching network or stability of the amplifiers . Typical resistive attenuator is structured in a shape of T‐type or π‐type network comprised of chip‐type resistors on the quasi‐TEM mode transmission line [e.g., microstrip (MS), coplanar waveguide (CPW)], which offers low profile properties and flexible design .…”

A 10–20 GHz 6-Bit High-Accuracy Digital Step Attenuator with Low Insertion Loss in 0.15 µm GaAs p-HEMT Technology

“…Moreover, especially when cascading multi-stage units, the inter-stage impedance mismatch leads to further worsening of the property. In order to address this issue, the literature [ 20 , 21 , 22 , 23 ] elucidates the compensation methods and effects of π-type, T-type, bridge T-type and distributed structures, and verifies the principle under different technologies. Nevertheless, this solution still suffers from a high attenuator IL due to the presence of the transistor lossy resistance R on in the reference state, which is the reason why switching path designs should be adopted with caution [ 5 ].…”