Switchable Wideband RF Summer Balancing Gain, Noise, and Linearity
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Solution Overview
Problem
Existing RF circuits, such as H-tree networks, face challenges in controlling gain without sacrificing matching and bandwidth, as prior approaches like resistive combiners and common variable gain amplifiers only achieve a limited dynamic range improvement, leading to issues with noise and linearity performance.
Innovation Solution
A selectively switchable RF summer circuit with resistances equal to Z0/3, featuring a series combination of a switch and a resistor coupled across an amplifier, allowing for passive and active modes of operation to balance noise and linearity by modifying gain values at the summed signal port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a resistive combiner with switched resistances or common variable gain amplifier topology is used, then gain control is achieved, but dynamic range improvement is limited and matching/bandwidth are sacrificed
Solution Approach 1:
The circuit dynamically switches between passive and active modes using switches (302, 304, 306) to reconfigure the amplifier's operation state. This dynamic reconfiguration allows the circuit to adapt gain control while maintaining impedance matching and bandwidth characteristics across different operating conditions, resolving the contradiction between gain control and matching/bandwidth preservation.
Solution Approach 2:
The invention changes the operational parameters of the amplifier by switching between passive and active modes, which modifies the effective resistance and gain characteristics. This parameter change enables the circuit to achieve wideband operation with improved dynamic range while maintaining proper impedance matching, overcoming the limitations of fixed-topology approaches.
2Power
If signals sum coherently in an H-tree network, then large signal is produced at output port, but non-linear distortion occurs at coupled amplifier
Solution Approach 1:
The circuit uses dynamic switching between passive and active modes to control the amplifier's operation point. When signals sum coherently and large signal levels are produced, the circuit can switch to active mode to maintain linearity and prevent non-linear distortion, while still delivering the required high signal level to the output port.
Solution Approach 2:
The switchable configuration provides a form of feedback control where the circuit can detect operating conditions and switch modes accordingly. This allows the circuit to maintain optimal linearity performance under high signal conditions by transitioning to active mode operation when coherent summation produces large signals that could cause distortion.
3Measurement precision
If signals sum incoherently in an H-tree network, then signal-to-noise ratio is reduced, but gain is reduced
Solution Approach 1:
The dynamic switching capability allows the circuit to operate in passive mode when incoherent summation occurs, maintaining proper gain levels while preserving signal-to-noise ratio performance. The circuit adapts to the incoherent summation condition by selecting the appropriate operational mode to balance gain and noise performance.
Data Source
AI summary
A radio frequency (RF) summer circuit having a characteristic impedance Zo comprises first and second ports coupled by first and second resistances, respectively, to a junction. The circuit further comprises a series combination of a third resistance and a switch movable between open and closed positions and an amplifier having input and output terminals and operable in an off state and an on state wherein the series combination is coupled across the input and output terminals of the amplifier between the junction and a third port. The first resistance, second resistance, and the third resistance are all substantially equal to Z0/3. Further, when the switch is moved to the closed position and the amplifier is switched to the off state a passive mode of operation is implemented and when the switch is moved to the open position and the amplifier is switched to the on state an active mode of operation is implemented. The RF summer circuit develops a summed signal at the third port equal to a sum of signals at the first and second ports modified by one of first and second gain values.