Reversible TDD Transceiver Layout for Shared TX/RX RF Chains
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Solution Overview
Problem
Conventional AIS transceivers face challenges in miniaturization due to the need for separate circuit areas for transmit and receive operations, which complicates their design and increases component count, especially in time-division duplex systems.
Innovation Solution
The implementation of a reversible RF chain architecture that alternates between intermediate frequencies, allowing for shared components and reduced layout complexity by using dual PLL synthesizers and voltage-controlled oscillators, enabling efficient switching between receive and transmit modes without altering local oscillator frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate circuit areas are used for transmit and receive operations, then reliability is improved, but device complexity increases and miniaturization becomes difficult
Solution Approach 1:
The patent merges separate transmit and receive circuit areas into a shared circuit architecture. The receiver local oscillator is shared with the transmitter, and the intermediate frequency is made reversible between transmit and receive modes. This consolidation reduces component count and layout complexity while maintaining reliable operation through time-division duplexing that separates transmit and receive operations in time.
Solution Approach 2:
The patent implements universal circuit components that serve multiple functions. The local oscillator generates frequencies for both receive downconversion and transmit upconversion. The intermediate frequency stage handles both received signals and generated transmit signals. This multi-functionality reduces overall device complexity while maintaining the reliability of separate transmit and receive paths through temporal separation.
2Reliability
If separate circuit areas are used for transmit and receive operations, then reliability is improved, but the area of the transceiver increases
Solution Approach 1:
The patent combines separate transmit and receive circuit areas into overlapping shared regions. By making the intermediate frequency reversible and sharing the local oscillator, the physical layout area is reduced. Time-division duplexing allows the same physical components to be used for both transmit and receive operations at different times, enabling miniaturization while preserving reliability through operational separation.
3Device complexity
If reversible RF circuits are used, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements dynamic switching between transmit and receive modes using time-division duplexing. RF switches dynamically connect the shared intermediate frequency stage to either receive or transmit paths based on operational mode. This dynamic configuration reduces static circuit complexity while managing manufacturing precision requirements through controlled switching operations rather than complex permanent circuit interconnections.
Solution Approach 2:
The patent employs periodic switching between transmit and receive operations following TDMA timing protocols. This periodic action allows the same circuit components to be reused alternately for transmit and receive functions, reducing overall device complexity. The rhythmic switching pattern simplifies the circuit architecture compared to permanently separate paths, while managing precision requirements through predictable, timed operations.
4Quantity of substance
If intermediate frequency is made reversible, then the number of components is reduced, but signal interference increases
Solution Approach 1:
The patent uses periodic time-division switching to alternate between transmit and receive modes on the shared intermediate frequency stage. By confining transmit and receive operations to distinct time slots, signal interference is minimized despite component sharing. The periodic switching ensures that transmit-generated signals do not continuously interfere with receive operations, allowing component reduction while managing interference through temporal separation.
Solution Approach 2:
The patent implements rapid switching between transmit and receive modes, rushing through the transition periods to minimize interference exposure. The fast switching allows the system to quickly move from transmit to receive mode on the shared intermediate frequency, reducing the time window for signal interference to occur. This enables component sharing while mitigating harmful interference effects through brief, controlled transition periods.
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
This approach facilitates the miniaturization of transceivers by reducing the number of components and layout complexity, enabling ultra-fast frequency settling and amplitude control, while maintaining low phase noise and spurious performance, thus improving receiver performance and reducing costs.
Implementation Method 1
The source of the required local oscillator signals is a quartz reference clock 56, which is connected to a dual PLL synthesiser 58. The dual PLL synthesiser 58 is connected to a first Voltage Controlled Oscillator (VCO) 60, for generating a local oscillator signal at a first local oscillator frequency, and to a second Voltage Controlled Oscillator (VCO) 62, for generating a local oscillator signal at a second local oscillator frequency.
Implementation Method 2
a signal entering the first receiver chain 12 is passed to a second SAW filter 28, and then to a first RF mixer 30, where it is downconverted to a first intermediate frequency (IF). The resulting IF signal is passed through a first IF amplifier 32, an IF crystal filter 34, and a second IF amplifier 36
Data Source
AI summary
A radio transceiver, particularly for use in a time division duplex system, has two reversible transceiver chains, each containing a respective radio frequency mixer; and an intermediate frequency generator, for receiving a baseband signal containing data for transmission, and for generating signals at two different intermediate frequencies modulated with said data. In a receive mode, each transceiver chain receives a respective signal at a respective radio frequency, and the respective radio frequency mixer downconverts the respective signal to a respective intermediate frequency. In transmit mode, one of said signals at the two different intermediate frequencies modulated with said data is passed to the respective radio frequency mixer for upconversion to the respective RF frequency. An AIS transponder includes such a radio transceiver. Miniaturization is helped by reusing certain circuit areas for both transmit and receive.