Selectable High/Low Side Injection in IF Transceiver
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Solution Overview
Problem
Conventional radio transceivers face challenges in achieving fast PLL lock times and low power consumption, especially in battery-powered applications, due to the need to frequently re-lock the PLL when switching between transmit and receive modes, which results in latency and increased current consumption.
Innovation Solution
The implementation of selectable high/low side injection methods in low IF transceivers, allowing the local oscillator frequency to remain constant for both transmit and receive modes, and enabling the rejection of image frequencies through agile receiver circuits with selectable inverters, thereby eliminating the need for PLL re-locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PLL is re-locked when switching between transmit and receive modes, then the receiver can operate at the correct frequency, but the lock time increases and power consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the mixer to accept both high-side and low-side injection modes. The receiver is designed with selectable injection paths that are prepared in advance, allowing immediate switching between transmit and receive modes without requiring PLL re-locking. This pre-prepared configuration enables fast mode switching while maintaining frequency accuracy.
2Reliability
If the PLL is re-locked when switching between transmit and receive modes, then the receiver can operate at the correct frequency, but power consumption increases
Solution Approach 1:
The receiver is pre-configured with both high-side and low-side injection paths available before mode switching occurs. This preliminary preparation eliminates the need for power-intensive PLL re-locking operations during mode transitions, thereby reducing power consumption while maintaining frequency accuracy.
3Device complexity
If a single LO is used for both transmit and receive, then device complexity is reduced, but the PLL must be re-locked when switching modes
Solution Approach 1:
The patent applies dynamics by making the mixer injection path selectable rather than fixed. The system dynamically switches between high-side and low-side injection modes based on whether the transceiver is in transmit or receive mode. This dynamic configuration allows a single LO to serve both functions without requiring re-locking, as the mixer adapts its injection path to match the current operational mode.
4Device complexity
If image frequencies are not rejected, then the receiver circuit is simpler, but susceptibility to interference increases
Solution Approach 1:
The patent converts the potentially harmful image frequency interference into a beneficial feature by using it for its intended purpose. The selectable inverter is configured to invert the image frequency signal and feed it to the summer, where it combines with the desired signal. This conversion transforms what would normally be harmful interference into a useful signal component, eliminating the need for complex image rejection filtering while maintaining circuit simplicity.
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 reduces latency and power consumption by allowing fast mode switching without re-locking the PLL, improving data delivery speed and battery life, while also simplifying the design by eliminating the need for dual oscillators and reducing interference from image frequencies.
Implementation Method 1
A conventional technique in radio design is to use a Mixer to perform frequency translation (i.e., multiplying two frequencies (F1, F2) to obtain the sum and difference frequencies (Fout)=M*F1+/−N*F2 (where M or N=1, 2, 3, . . .)=F1+F2, F1−F2, 2*F1+/−F2, 2*F2+/−F1, 3*F1+/−2*F2, etc.).
Data Source
AI summary
A method of communication between a first transceiver having a first local oscillator set at a first frequency and a second transceiver having a second local oscillator set at a second frequency disclosed. The method includes transmitting a first signal at a first frequency from the first transceiver to the second transceiver, transmitting a second signal at the second frequency from the second transceiver to the first transceiver, and receiving the second signal at the first transceiver. The method further includes maintaining the first local oscillator at the first frequency and the second local oscillator at the second frequency during the transmitting of the first signal, during the receiving of the first signal, during the transmitting of the second signal, and during the receiving of the second signal.