Hybrid Spread Spectrum System Constant Envelope Signal Generation
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Solution Overview
Problem
Conventional hybrid spread spectrum systems lack power efficiency and bandwidth efficiency due to non-constant envelope signals, which restricts the use of high power amplifiers and limits throughput.
Innovation Solution
A hybrid spread spectrum system that combines direct sequence and frequency hopping techniques to generate signals with a constant envelope, using multiple carriers that hop simultaneously, and includes a signal combiner and mixers to form two-carrier or three-carrier constant envelope signals, followed by high pass filtering to produce a single sideband hybrid spread spectrum signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional hybrid spread spectrum systems use non-constant envelope signals, then the system can achieve spread spectrum communication, but power efficiency deteriorates because high power amplifiers cannot operate efficiently
Solution Approach 1:
The system segments the spread spectrum signal into multiple carrier components, each modulated with specific spreading codes. By dividing the signal into multiple carriers with controlled phases and amplitudes, the system can reconstruct a constant envelope signal that allows efficient high power amplifier operation while maintaining spread spectrum properties through code modulation.
Solution Approach 2:
The system changes the signal parameters by enforcing constant envelope constraints on the multi-carrier signal. This is achieved by carefully controlling the phase and amplitude relationships between carriers and their respective spreading codes, transforming the signal from a variable envelope to a constant envelope form without losing spread spectrum functionality.
2Use of energy by moving object
If conventional hybrid spread spectrum systems use non-constant envelope signals, then the system can achieve spread spectrum communication, but bandwidth efficiency deteriorates
Solution Approach 1:
The system segments the data stream into multiple parallel channels, each modulated onto a separate carrier with its own spreading code. This segmentation enables simultaneous transmission of multiple signals in the same bandwidth, increasing throughput while maintaining spectral efficiency through the orthogonality of the spreading codes.
Solution Approach 2:
The system merges multiple carrier signals with different spreading codes into a composite constant envelope signal. By combining these signals in a specific way that maintains constant envelope properties, the system achieves both high bandwidth efficiency and increased throughput through multi-carrier transmission.
3Productivity
If the system uses multiple carriers to increase throughput, then productivity improves, but device complexity increases
Solution Approach 1:
The system segments the transmission into multiple carrier components, each handling a portion of the data stream with its own spreading code. This segmentation increases throughput by parallel transmission while managing complexity through modular signal processing structures that can be implemented using standard spread spectrum components.
Solution Approach 2:
The system uses universal spreading codes and modulation techniques that can be applied across multiple carriers. This multi-functionality allows the same hardware and processing algorithms to be reused for each carrier, increasing throughput without proportionally increasing system complexity.
Data Source
AI summary
A hybrid spread spectrum system includes a signal combiner for (a) receiving a plurality of spread spectrum encoded data signals and (b) forming a plurality of combined signals. A first set of mixers is included for (a) receiving the plurality of combined signals and at least two carriers, and (b) forming at least a two-carrier, constant envelope signal. A second set of mixers is also included for (a) receiving the at least two-carrier, constant envelope signal and a transmitter hopping signal and (b) forming a hybrid spread spectrum signal. The combined signals include (a) [s1(t)−s1(t)s2(t)s3(t)] and (b) [s2(t)+s3(t)], where si(t) are three separate spread spectrum encoded data signals. The transmitter hopping signal is a sequence of tones having (a) a duration Tc, where Tc is a chip duration, and (b) frequencies fn taken from a set of 2k values, where k is a number of bits from a pseudo-random noise (PRN) sequence.