Double-Balanced Mixer Circuit With Common-Mode Noise Suppression
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Solution Overview
Problem
Double-balanced mixers in communication technologies face challenges with unwanted DC interference and AC interference in output signals, which affect design efficiency and performance, especially when applying bias voltages.
Innovation Solution
A double-balanced mixer circuit design that includes a diode mixer, a voltage divider circuit, and an amplifier, where the diode mixer receives input signals and bias voltages to generate output signals, and the voltage divider circuit generates a common mode signal to suppress noise, allowing the amplifier to produce a final output signal with reduced interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a diode mixer is used to generate output signals, then frequency conversion is achieved, but DC interference and AC interference are introduced in the output signal
Solution Approach 1:
A voltage divider circuit is introduced as an intermediary component between the diode mixer and the amplifier. This voltage divider generates a common mode signal that serves as a mediator to cancel out the DC and AC interference in the output signal, allowing frequency conversion to proceed while eliminating harmful interference components
Solution Approach 2:
The interference signals (DC and AC) generated by the diode mixer are converted into a useful common mode signal through the voltage divider circuit. This common mode signal is then used by the amplifier to suppress the original interference, transforming the harmful interference into a beneficial reference for noise cancellation
2Object-generated harmful factors
If capacitors are added to the output circuit to suppress noise, then interference is reduced, but circuit area increases
Solution Approach 1:
The traditional mechanical/electrical approach of using capacitors for noise suppression is replaced with a signal processing approach. The voltage divider circuit generates a common mode signal that electronically cancels interference through the amplifier, substituting passive component-based suppression with active signal-based suppression
Solution Approach 2:
The approach to noise suppression changes from modifying circuit parameters (adding capacitors) to modifying signal parameters (introducing common mode signal). This parameter change allows interference suppression without increasing physical circuit area
3Reliability
If bias voltages are applied to the diode mixer, then mixing performance is improved, but common mode voltage and noise are generated
Solution Approach 1:
The voltage divider circuit provides a feedback mechanism by generating a common mode signal that is fed back to the amplifier. This feedback signal is specifically designed to counteract the common mode voltage and noise generated by the bias voltages in the diode mixer, allowing high mixing performance while eliminating the associated harmful effects
Data Source
AI summary
A mixer circuit including a mixer, a voltage divider circuit, and an amplifier, is provided. The mixer receives a first input signal, a second input signal, and at least one set of bias voltages, and generates an output signal. A frequency of the output signal is related to a frequency of the first input signal and a frequency of the second input signal. The voltage divider circuit receives the bias voltages and generates a common mode signal at an output end. The amplifier is coupled to the mixer to receive the output signal, and is coupled to the output end of the voltage divider circuit and configured to suppress noise in the output signal, and generate a final output signal.