Digital IMP Cancellation for Transmitter Intermodulation Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Satellite communication systems face limitations due to intermodulation products (IMPs) and side lobe re-growth, which restrict channel capacity and efficiency, especially in high power transmission systems where non-linear devices generate active and passive IMPs, requiring transmitter back-off to near linear operation to prevent interference.
Innovation Solution
The technology employs direct cancellation techniques in the digital domain to suppress passive and active IMPs by isolating and multiplying source signals to create an IMP cancellation signal, allowing for operation at or near saturation with multiple carriers while controlling out-of-band emissions, applicable to both transmitters and receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmitter operates at high power near saturation, then power efficiency and capacity improve, but intermodulation products and out-of-band emissions increase
Solution Approach 1:
The patent applies pre-distortion techniques where the transmitter deliberately introduces the opposite of expected nonlinear distortions before signal amplification. By pre-compensating for intermodulation products and out-of-band emissions in the digital domain before DAC conversion, the system can operate amplifiers near saturation while maintaining linear output characteristics and suppressing harmful IMPs.
Solution Approach 2:
The patent implements feedback mechanisms where a portion of the transmitter output is captured, analyzed for intermodulation products, and used to generate correction signals. These feedback signals are processed through digital signal processing algorithms that calculate the optimal cancellation signals to suppress identified IMPs, creating a closed-loop control system that dynamically compensates for nonlinear distortions.
2Object-generated harmful factors
If transmitter back-off is increased to reduce IMPs, then intermodulation products decrease, but power efficiency and EIRP deteriorate
Solution Approach 1:
The patent converts the harmful intermodulation products generated by high-power amplifier operation into beneficial cancellation signals. By capturing the actual IMPs produced during saturation operation and processing them through digital signal processing, the system generates anti-phase cancellation signals that suppress the harmful emissions while allowing the amplifier to maintain efficient high-power operation.
3Object-generated harmful factors
If digital cancellation techniques are applied, then IMP suppression improves, but device complexity increases
Solution Approach 1:
The patent replaces complex analog filtering and isolation hardware with digital signal processing techniques. Instead of using multiple physical filters, isolators, and passive components to suppress intermodulation products, the system uses digital algorithms running on FPGAs or DSP processors to calculate and generate cancellation signals, simplifying the hardware architecture while achieving superior IMP suppression performance.
Data Source
AI summary
A transmitter channel interference mitigation processing method for cancellation of intermodulation products are described. In one embodiment, a method comprising generating continuous and real time IMP cancellation signals (ICS) in the baseband digital signal set of the transmitter based on a transmitter signal set, combining digital IMP cancellation signals with a digital baseband transmitter signal set such that the digital cancellation signals, when converted to analog signals and transmitted as part of an analog transmitter signal set, are cancelled by and so cancel the IMPs generated by the non-linear components in the analog transmitter hardware, including digitally generating the IMP cancellation signals using a process based on a power series description of a non-linear process generating the IMPs, generating 3rd order IMP cancellation signals by digitally multiplying two or three signals of the transmitter signal set to create 3rd order IMP cancellation signals, generating 5th order IMP cancellation signals by digitally multiplying two or three or five signals of the transmitter signal set to create 5th order IMP cancellation signals, generating 7th order IMP cancellation signals by digitally multiplying two or three or five or seven signals of the transmitter signal set to create 7th order IMP cancellation signal, generating odd order IMP cancellation signals (ICS) by digitally multiplying an odd number of digital signals and combining multiplied digital signals with the transmitter baseband digital signals, creating IMP cancellation signals in the receiver, and cancelling one or both of active and passive IMPs generated in a transmitter path that fall within a receiver passband.