Linear Transmitter Frequency Plan for Fixed IF and Variable LO
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Solution Overview
Problem
Existing VSAT systems face bandwidth inefficiencies and interference issues due to the use of variable Intermediate Frequency (IF) signal frequencies and fixed Local Oscillator (LO) reference signal frequencies, leading to increased bandwidth requirements and difficulties in multiplexing signals over a single inter-facility link, which results in higher costs and complex signal calibration.
Innovation Solution
Implementing a linear technology radio with a pre-amplifier, IF amplifier, and mixer that uses a fixed IF signal frequency and a variable LO reference signal frequency, allowing for the generation of a radio frequency (RF) signal with a frequency band from 28.1 to 30 GHz, enabling the use of a single inter-facility link without frequency overlap and reducing installation costs by utilizing standard semiconductor chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable IF signal frequency is used, then the frequency range coverage is improved, but the bandwidth requirement increases and signal interference occurs
Solution Approach 1:
The patent inverts the conventional frequency plan by making the LO reference signal variable instead of the IF signal. This inversion allows the IF signal to remain fixed at a lower frequency (reducing bandwidth requirements), while the variable LO reference signal (200-400 MHz) is multiplied by a fixed factor (e.g., 128) to achieve the desired high frequency output range (28.1-30 GHz), thereby covering the required frequency range without increasing bandwidth.
Solution Approach 2:
The patent changes the parameter that is varied - instead of varying the IF signal frequency, the LO reference signal frequency is varied (from 200 MHz to 400 MHz). This parameter change, combined with frequency multiplication by a fixed factor, achieves the same frequency range coverage (28.1-30 GHz) while maintaining a fixed, lower frequency IF signal that requires less bandwidth.
2Adaptability or versatility
If a variable IF signal frequency is used, then the frequency range coverage is improved, but signal interference and multiplexing difficulty increase
Solution Approach 1:
The patent inverts the conventional approach by making the LO reference signal variable and the IF signal fixed. This inversion eliminates frequency overlap between transmit and receive signals on the IFL, as the fixed IF signal (e.g., 2 GHz) remains separate from the variable LO reference signal (200-400 MHz) and its multiplied output. Consequently, a single IFL can carry both signals without interference, greatly simplifying multiplexing and eliminating the need for expensive custom conversion chips.
3Quantity of substance
If a fixed IF signal frequency is used, then bandwidth is reduced and multiplexing is simplified, but frequency range coverage is limited
Solution Approach 1:
The patent implements frequency multiplication where a lower frequency LO reference signal (200-400 MHz) is multiplied by a fixed factor (e.g., 128) to generate the high frequency output (28.1-30 GHz). This nested frequency generation approach allows a fixed IF signal to be combined with a variable LO reference signal to achieve wide frequency range coverage without requiring the IF signal itself to vary, thereby maintaining bandwidth efficiency while achieving adaptability.
Solution Approach 2:
The patent changes which parameter is varied to achieve frequency range coverage. Instead of varying the IF signal frequency, the LO reference signal frequency is varied (200-400 MHz) and then multiplied by a fixed factor. This parameter substitution maintains a fixed IF signal (preserving bandwidth efficiency) while achieving the required frequency range coverage through the variable LO and multiplication process.
4Adaptability or versatility
If high frequency IF signals are used, then frequency range coverage is improved, but signal attenuation increases and calibration becomes more difficult
Solution Approach 1:
The patent inverts the conventional frequency plan by keeping the IF signal at a fixed, lower frequency (e.g., 2 GHz) instead of using high variable frequencies. This inversion significantly reduces signal attenuation over long cable distances. The high frequency range (28.1-30 GHz) is achieved instead through frequency multiplication of the LO reference signal, which does not suffer from the same attenuation issues on the IFL.
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 the necessary bandwidth between indoor and outdoor units by a factor of 128, eliminates interference, and simplifies signal calibration, thereby lowering installation costs and improving the efficiency of VSAT systems.
Implementation Method 1
a pre-amplifier to amplify a Local Oscillator (LO) reference signal
Implementation Method 2
an intermediate frequency (IF) amplifier to amplify an IF signal
Implementation Method 3
a frequency multiplier to multiply the LO reference signal
Implementation Method 4
a mixer to mix the amplified LO reference signal and the amplified IF signal to generate a radio frequency (RF) signal
Data Source
Figure 1A~1B
Figure 2~3
AI summary
A linear technology radio for use in satellite communication is provided. The linear technology radio includes: a pre-amplifier to amplify a Local Oscillator (LO) reference signal; an intermediate frequency (IF) amplifier to amplify an IF signal; a frequency multiplier to multiply the LO reference signal; and a mixer to mix the amplified LO reference signal and the amplified IF signal to generate a Radio Frequency (RF) signal, wherein a frequency band of the IF signal is fixed, a frequency band of the LO reference signal is variable, and a highest frequency of the LO reference signal frequency band is less than a lowest frequency of the IF signal frequency band.