Time Transfer Modem Using RFIC Pre-Selection Filtering
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Solution Overview
Problem
Existing clock synchronization systems face challenges in maintaining accurate synchronization between remote devices, especially across long distances, due to physical and signaling overhead, which affects throughput, cost, and size, particularly in scenarios where cabling is not feasible, such as across oceans or in remote locations.
Innovation Solution
A time transfer modem system utilizing a radio frequency integrated circuit (RFIC), a tunable RF front end with a pre-selection filter, and processing circuitry to up-convert, filter, and down-convert timing signals, enabling sub-nanosecond accuracy in clock synchronization through satellite communications, using spread spectrum signals with long memory codes to reduce interference and support multiple simultaneous operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cabling is used for clock synchronization, then synchronization accuracy is improved, but feasibility deteriorates when stations are located across oceans or in remote regions
Solution Approach 1:
The patent uses satellite communications as an intermediary medium to transmit timing signals between ground stations that are too distant to be connected by cable. The satellite acts as a mediator that bridges the gap between remote stations, enabling clock synchronization across oceans and remote regions where direct cabling is not feasible.
2Adaptability or versatility
If satellite communications are used for clock synchronization, then adaptability for remote locations is improved, but device complexity and overhead increase
Solution Approach 1:
The patent extracts and removes adjacent channel interference from the received signal using filtering techniques before processing the timing signal. This extraction of harmful components reduces the burden on subsequent processing stages and simplifies the overall system design by eliminating the need for complex interference management throughout the signal chain.
Solution Approach 2:
The patent performs preliminary filtering of the received signal to remove adjacent channel interference before further processing. By taking this action in advance, the system prepares the signal for more accurate timing extraction and reduces complexity in later stages, as the interference has already been mitigated.
3Adaptability or versatility
If traditional RF front-end design is used, then frequency range coverage is improved, but adjacent channel interference increases
Solution Approach 1:
The patent introduces a pre-selection filter as an intermediary component between the antenna and the RFIC to block adjacent channel interference before it enters the frequency conversion stage. This filter acts as a gatekeeper that allows the desired frequency range to pass through while preventing harmful adjacent channel signals from causing interference.
Solution Approach 2:
The patent segments the frequency processing into distinct stages: a pre-selection filter stage that handles frequency selection and interference rejection, followed by an RFIC stage that handles the actual frequency conversion and processing. This segmentation allows each component to be optimized for its specific function, with the filter handling interference and the RFIC handling signal conversion.
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 system achieves high accuracy clock synchronization with reduced size, power, and weight, enabling efficient clock synchronization across long distances, including through satellite intermediaries, while minimizing equipment delays and environmental effects like the Sagnac effect.
Implementation Method 1
The RF front end may be further configured to up-convert the input, including the timing signal and the adjacent signals, to generate an up-converted timing signal centered at a select frequency that is outside of the frequency range of interest but within the operational frequency range of the RFIC
Implementation Method 2
The RF front end may be further configured to attenuate, via the pre-selection filter, the up-converted adjacent signals at the up-converted adjacent frequencies to generate a filtered timing signal at the select frequency
Implementation Method 3
The RFIC may be configured to down-convert and digitize the filtered timing signal to generate a digitized timing signal
Data Source
AI summary
A time transfer modem includes a radio frequency integrated circuit (RFIC), a radio frequency (RF) front end, and processing circuitry. The RF front end is configured to receive and up-convert an input for time transfer with a remote station to generate an up-converted timing signal centered at a select frequency that is outside of a frequency range of interest but within an operational frequency range of the RFIC. The RF front end may also be configured to attenuate, via a pre-selection filter, up-converted adjacent signals to generate a filtered timing signal at the select frequency. The RFIC may be configured to down-convert and digitize the filtered timing signal to generate a digitized timing signal for signal processing by the processing circuitry to determine a clock difference between a local clock signal and the digitized timing signal that originated from the remote station.