Design of a Low-Cost Flat E-Band Down-Converter with Variable Conversion Gain

Area of Science:

• Microwave Engineering
• Integrated Circuit Design
• Millimeter-wave Technology

Background:

• Millimeter-wave (mmWave) systems require efficient down-conversion for applications like high-speed communication and sensing.
• Existing designs often face challenges with bandwidth, gain flatness, and port isolation at these high frequencies.

Purpose of the Study:

• To design and implement a wideband diode-based down-converter operating from 60 to 90 GHz.
• To achieve a variable and flat conversion gain across the operating band.
• To utilize Miniature Hybrid-Microwave Integrated Circuit (MHMIC) technology for compact implementation.

Main Methods:

• A wideband double-balanced mixer with a novel topology was developed for minimum reflection and high RF-LO isolation.
• A Local Oscillator (LO) chain combining active (x2) and passive (x3) multipliers was employed.
• A differential TransImpedance Amplifier (TIA) using OPA 657 with variable gain was integrated.
• A WR-12 waveguide to Substrate Integrated Waveguide (SIW) transition was designed for E-band operation.

Main Results:

• The down-converter achieved a maximum conversion gain of -5 dB with a variation of ±5 dB across the 60-90 GHz band.
• High isolation between RF and LO ports exceeded 22 dB.
• The mixer exhibited a return loss better than 10 dB at RF and LO ports.
• The device consumed 560 mW of power.

Conclusions:

• The designed MHMIC down-converter demonstrates excellent performance for E-band applications.
• The novel mixer topology and integrated TIA contribute to the wideband, flat gain characteristics.
• This implementation offers a viable solution for high-frequency signal processing with improved efficiency and integration.