Transformer-Feedback Receiver Circuit for Linear RF Impedance Matching
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Solution Overview
Problem
The increasing demand for high receiver linearity in wireless communications, particularly in devices like cellular phones, is challenged by the need to manage multiple frequency bands with strong interference while maintaining low noise and power consumption, especially in receiver architectures that use positive feedback which can lead to non-linearity and instability.
Innovation Solution
A receiver circuit design utilizing negative feedback through a transformer to combine a feedback signal with the input signal, achieving frequency-selective impedance matching by upconverting the feedback signal to the RF frequency, thereby improving linearity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If positive feedback is used in receiver architecture, then input impedance control is improved, but linearity deteriorates and instability increases
Solution Approach 1:
The patent inverts the feedback approach by using negative feedback instead of positive feedback. The feedback signal is subtracted from the input signal through the transformer, creating negative feedback that improves linearity while maintaining impedance control capabilities.
Solution Approach 2:
The patent implements a feedback mechanism where the output signal is fed back through a mixer and transformer to the input. This feedback loop allows dynamic control of input impedance while maintaining stability and linearity through the negative feedback configuration.
2Object-affected harmful factors
If frequency selective impedance matching is implemented, then interference rejection is improved, but device complexity increases
Solution Approach 1:
The transformer in the patent serves multiple functions simultaneously: it provides impedance transformation, combines the feedback signal with the input signal, and enables frequency-selective impedance matching. This multi-functionality reduces the need for additional separate components.
Solution Approach 2:
The transformer acts as an intermediary element that mediates between the feedback path and the input signal. It combines the feedback signal with the input signal while providing frequency-selective impedance matching, simplifying the overall circuit architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves excellent in-band and out-of-band linearity with improved intermodulation performance and reduced noise figure, while maintaining low power consumption.
Implementation Method 1
The upconverted feedback signal is combined in the voltage domain with the input signal, e.g. by means of a transformer
Data Source
AI summary
An example of a receiver circuit is disclosed. The receiver circuit comprises an input for receiving a radio frequency signal, an output for providing an output signal of the receiver circuit, a receive path, wherein the receive path is connected between the input and the output of the receiver circuit, and a feedback path, wherein an input of the feedback path is connected to the output of the receiver circuit. The receiver circuit also comprises a transformer, wherein an output signal of the feedback path is combined with the received radio frequency signal in the receive path to form a first signal. The receive path comprises a first mixer for downconverting the first signal by a local oscillator frequency, and an amplifier for amplifying the downconverted first signal. The feedback path comprises a second mixer for upconverting a signal in the feedback path by said local oscillator frequency. The combination of the output signal of the feedback path with the received radio frequency signal is achieved by means of the transformer.