Mixed Local Oscillator Signal Conversion for Satellite Phase Noise Reduction
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Solution Overview
Problem
Communications satellites face challenges in efficiently converting and routing signals due to high phase noise from multiple local oscillator signals and the impracticality of large waveguide switch matrices, especially when handling large bandwidths and multiple downlink beams.
Innovation Solution
The use of a mixed local oscillator signal for both down-conversion and up-conversion, along with a bandpass filter to select specific frequency ranges, reduces phase noise and eliminates the need for complex waveguide switch matrices by allowing flexible routing of signals across different frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple local oscillator signals are used for frequency conversion, then signal routing flexibility is improved, but phase noise increases
Solution Approach 1:
The patent combines multiple frequency conversion operations into a single conversion stage by merging the functions of multiple LO signals into one mixed LO signal. The first and second LO signals are mixed together to create a single mixed LO signal that performs both down-conversion and up-conversion operations, reducing the number of separate LO sources from two to one, thereby reducing phase noise while maintaining routing flexibility
Solution Approach 2:
The mixed LO signal acts as an intermediary that mediates between the multiple original LO signals and the frequency conversion process. By mixing the first and second LO signals to create this intermediate mixed signal, the system reduces the number of direct LO sources affecting the signal path, thereby reducing phase noise while preserving the ability to route signals flexibly across different frequency bands
2Adaptability or versatility
If waveguide switch matrices are used for signal routing, then signal distribution capability is improved, but device mass increases
Solution Approach 1:
The patent extracts the frequency conversion function from the traditional waveguide switch matrix architecture. Instead of using a large N×N waveguide matrix to route signals between multiple inputs and outputs, the invention removes this bulky structure and replaces it with frequency-based signal separation and conversion, keeping only the essential bandpass filters and frequency conversion components
Solution Approach 2:
The mixed LO signal generation circuit serves multiple functions simultaneously: it generates the local oscillator signal for frequency conversion, acts as a signal mixer to combine multiple LO signals, and provides frequency translation capability. This multi-functional approach replaces what would otherwise require separate waveguide switching matrices for each function, reducing overall device mass
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 significantly reduces phase noise and enables flexible signal routing and frequency reuse, allowing for efficient conversion and distribution of signals across multiple downlink beams without the need for large and cumbersome waveguide switch matrices.
Implementation Method 1
a first mixer arranged to mix the received signal with a first local oscillator LO signal to down-convert the received signal
Implementation Method 2
a bandpass filter arranged to filter the mixed signal such that the filter bandwidth defines the width of the first frequency range, the bandpass filter having a passband with a centre frequency at the IF
Implementation Method 3
a second mixer arranged to mix the filtered IF signal with a second LO signal to up-convert the IF signal to an output frequency range different to the input frequency range
Data Source
AI summary
Apparatus for use in a communications satellite can include a first mixer arranged to mix and down-convert a received signal in an input frequency range with a first local oscillator LO signal so that a signal within the received signal at a center frequency of a first frequency range is converted to an intermediate frequency IF, a bandpass filter having a passband with a center frequency at the IF arranged to filter the mixed signal such that the filter bandwidth defines the width of the first frequency range, and a second mixer arranged to mix the filtered IF signal with a second LO signal to up-convert the IF signal to an output frequency range. One of the first and second LO signals is a mixed LO signal obtained by mixing the other one with a third LO signal, and the output frequency range is different from the input frequency range.