Wideband RF Output Isolation Using Cascode Tee-Filter Paths
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving sufficient isolation between multiple RF signal outputs, particularly when these signals operate at different frequencies and are derived from the same antenna, leading to potential mutual interference and reduced signal quality.
Innovation Solution
The proposed solution involves a cascode circuit with a common transistor and split second-stage transistors, coupled with inductive elements and tee-filters, to selectively pass RF signals and achieve isolation between output ports. This configuration ensures that each RF signal is preferentially passed to its designated output terminal, minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple RF signals are transmitted through the same antenna and output circuit, then the system can support multi-mode wireless communications, but isolation between different RF signal outputs deteriorates leading to mutual interference
Solution Approach 1:
The output circuit is segmented into multiple independent signal paths, each handling a specific RF frequency range. The cascode configuration divides the transistor circuitry into separate stages (first transistor for input signal, second transistor for output signal) that are electrically isolated yet functionally connected, allowing multiple RF signals to be transmitted through the same antenna without mutual interference.
Solution Approach 2:
The patent introduces intermediate filtering elements (tee-filters, inductors, capacitors) between the RF amplifier output and the antenna connection. These intermediary components selectively pass desired RF frequencies while blocking unwanted frequencies, thereby achieving isolation between different RF signal paths without preventing multi-mode operation.
2Object-affected harmful factors
If isolation circuits are added to reduce interference between RF outputs, then signal quality improves, but circuit complexity increases
Solution Approach 1:
The cascode transistor configuration serves multiple functions simultaneously: it provides signal amplification, frequency isolation, and impedance matching. The same transistor structure that amplifies the RF signal also inherently provides isolation between different frequency paths, eliminating the need for separate isolation circuits and reducing overall complexity.
Solution Approach 2:
The patent merges the amplification function and isolation function into a single integrated cascode circuit structure. The first and second transistors work together as both an amplification stage and an isolation mechanism, while the tee-filters combine filtering and impedance transformation functions, reducing the total number of discrete components needed.
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 described configuration achieves isolation of -20 dB or greater between the output terminals, effectively reducing mutual interference and enhancing the signal-to-noise ratio of the RF signals, even when the signals have center frequencies differing by more than 1.5 GHz.
Implementation Method 1
the first output comprises a first tee-filter configured to preferentially pass the first RF signal to a first connection terminal; and the second output comprises a second tee-filter configured to preferentially pass the second RF signal to a second connection terminal
Implementation Method 2
the second source/drain of the first transistor is coupled with a first terminal of a first inductor, a second terminal of the first inductor coupled with a first voltage node; and the second source/drain of the second transistor is coupled with a first terminal of a second inductor, the second terminal of the second inductor coupled with the first voltage node
Data Source
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AI summary
Wide-band output isolation is provided. A device (100) includes a first output (304) for a first RF signal and a second output (306) for a second RF signal. The device (100) includes a first transistor (212) having a first source/drain. The device (100) includes a second transistor (214) having a first source/drain, wherein the first source/drain of the first transistor (212) is coupled to the first source/drain of the second transistor (214) and wherein the first and second transistors (212, 214) are disposed between the first output (304) and the second output (306).