Dual-Use RF Transistor Cascode Without External Switches
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Solution Overview
Problem
Existing RF communication device circuits face challenges in minimizing complexity, cost, and parasitic capacitance, especially at high frequencies, due to the need for external switches and components that degrade performance and increase power consumption, making them unsuitable for very high frequency radio communications and ultra-wideband transceivers.
Innovation Solution
A circuit design using a common-gate amplifier configuration with a choke for voltage biasing, allowing the circuit to operate in both receive and transmit modes without external switches, with a tunable resonant circuit and amplitude modulation capabilities, optimized for low noise and power amplification, and fabricated using a deep-submicron process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external switches are used to couple antenna to transmit and receive circuitry, then the circuit can be switched between transmit and receive modes, but the parasitic capacitance increases and performance degrades at very high frequencies
Solution Approach 1:
The patent removes external switches from the circuit by integrating the switching function directly into the transistor gate control mechanism. The gate of the transistor serves dual purposes: amplification control and mode switching, eliminating the need for separate external switch components that introduce parasitic capacitance.
Solution Approach 2:
The patent combines the amplification and switching functions into a single transistor device. The same transistor that amplifies RF signals also performs the switching between transmit and receive modes through gate voltage control, merging two previously separate functions into one integrated component.
2Reliability
If external switches and filters are added to the signal path, then transmit and receive circuitry can be isolated, but the device complexity and number of external components increases
Solution Approach 1:
The patent makes the transistor serve multiple functions: it acts as an amplifier during both transmit and receive modes, and simultaneously functions as a switch to isolate the opposite path. This multi-functionality eliminates the need for separate isolation switches and filters, reducing overall device complexity.
Solution Approach 2:
The transistor's gate control mechanism automatically performs the isolation function without requiring external control switches. When the transistor is biased in cutoff mode, it naturally isolates the opposite signal path, making the isolation function self-service rather than requiring additional external components.
3Ease of operation
If external switches are used for antenna coupling, then mode switching is achieved, but insertion losses increase and power consumption increases
Solution Approach 1:
The patent extracts the switching function from external switch components and relocates it to the transistor's gate control mechanism. This eliminates the insertion losses associated with external switches while maintaining the ability to switch between transmit and receive modes through electronic control.
4Ease of manufacture
If discrete external components are used instead of integrated circuit components, then certain functions can be achieved, but the cost and PCB area consumed increases
Solution Approach 1:
The patent merges multiple discrete external components (amplifier, switch, filters) into a single integrated transistor device fabricated on the same chip as the transmit and receive circuitry. This integration dramatically reduces PCB area while maintaining all necessary functionalities through clever circuit design and biasing schemes.
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 solution enables efficient RF front-end operation at high frequencies with reduced parasitic capacitance and current consumption, suitable for ultra-wideband communication systems, and supports multiple communication protocols in a single chip, achieving low noise amplification and high power output.
Implementation Method 1
a common amplifier arranged in a common-gate configuration between a first node and said terminal; a transmit amplifier operable to amplify a radio frequency signal present at an input node and provide the amplified signal to said first node; and a receive amplifier operable to amplify a radio frequency signal present at said first node
Implementation Method 2
A circuit design using a common-gate amplifier configuration with a choke for voltage biasing
Implementation Method 3
with a tunable resonant circuit and amplitude modulation capabilities, optimized for low noise and power amplification
Data Source
AI summary
A circuit for amplifying radio frequency signals comprising: a terminal for connection to an antenna; a common amplifier arranged in a common-gate configuration between a first node and said terminal; a transmit amplifier operable to amplify a radio frequency signal present at an input node and provide the amplified signal to said first node; and a receive amplifier operable to amplify a radio frequency signal present at said first node and provide the amplified signal to an output node; wherein the circuit is operable in two modes: in a receive mode, the common and receive amplifiers being configured so as to together form a receive cascode for amplifying radio frequency signals received at the terminal; and in a transmit mode, the common and transmit amplifiers being configured so as to together form a transmit cascode for amplifying radio frequency signals applied at the input node.