Differential Active Mixer With Bandwidth Peaking for Flat Gain
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Solution Overview
Problem
Designing an ultra wide band active mixer on a die for use as an integrated circuit that spans from DC to greater than 20 GHz is challenging due to difficulties in achieving constant gain across the entire frequency band, especially when dealing with low-level signals and the need for amplifier stages in wide band applications.
Innovation Solution
The solution involves a core mixer with a steering module, a bandwidth peaking network, and a common mode bias network, which includes coils and resistors to enhance frequency bandwidth, provide controlled impedance, and maintain gain across the entire frequency range, along with a common mode biasing method for AC applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wide band mixer is designed to respond to the entire frequency band from DC to 20 GHz, then the frequency bandwidth is improved, but the gain consistency across the frequency band deteriorates
Solution Approach 1:
The patent implements dynamic bandwidth peaking networks that adjust their characteristics across the frequency spectrum. The network includes series LC circuits tuned to specific frequencies that provide selective impedance transformation, allowing the mixer to maintain consistent gain from DC to 20 GHz by dynamically compensating for frequency-dependent variations in the mixing process.
Solution Approach 2:
The patent changes the impedance parameters of the mixer circuit through the bandwidth peaking network. By transforming the output impedance and loading conditions as a function of frequency, the circuit maintains optimal operating parameters across the entire ultra-wide band, thereby preserving gain consistency while extending bandwidth.
2Power
If an amplifier stage is added to amplify low-level mixed signals, then the signal amplification is improved, but the device complexity increases
Solution Approach 1:
The patent merges the mixing and amplification functions into a single integrated stage. The active mixer core inherently provides gain through its transistor configuration, eliminating the need for a separate amplifier stage. This consolidation reduces device complexity while maintaining the ability to amplify low-level signals.
Solution Approach 2:
The mixer circuit is designed to perform multiple functions simultaneously: frequency conversion, signal amplification, and impedance matching. The active elements serve both as mixing devices and as amplifiers, reducing the overall circuit complexity while achieving the required signal level for further processing.
3Productivity
If the mixer is fabricated as an integrated circuit on a die, then the manufacturing efficiency is improved, but the fabrication difficulty for ultra wide band performance increases
Solution Approach 1:
The patent employs local quality variations in the integrated circuit layout to achieve ultra-wide band performance. Different regions of the circuit are optimized for specific frequency ranges, with careful attention to local impedance control, parasitic element management, and transistor biasing. This localized optimization enables DC to 20 GHz operation while maintaining compatibility with standard IC fabrication processes.
Solution Approach 2:
The circuit incorporates dynamic elements such as varactor diodes and tuned LC networks that can be fabricated using standard semiconductor processes. These elements provide frequency-selective behavior that compensates for fabrication variations, enabling consistent ultra-wide band performance across production batches without requiring specialized manufacturing techniques.
Data Source
AI summary
A wideband mixer includes a core mixer having input terminals and output terminals for, respectively, receiving differential input signals and providing amplified differential output signals. A steering module is coupled to the core mixer for receiving differential reference signals and providing bi-phase modulated amplified differential output signals. The core mixer is configured to provide a value of gain between the differential input signals and the differential output signals. A bandwidth peaking network is coupled to the core mixer and includes (a) a first coil and a first resistor connected in series and (b) a second coil and a second resistor connected in series. The first coil and resistor and the second coil and resistor, respectively, are coupled to the core mixer for receiving the amplified differential output signals. The bandwidth peaking network is configured to increase the frequency bandwidth of the core mixer.