chapter 9, Basic RF Definitions and IMD Effects on TV Picture

In Part 3 RF and Control Concepts from: Digital and Analog Fiber Optic Communications for CATV and FTTx Applications

Author(s): Avigdor Brillant

Published: 10 June 2008

Chapter DOI: http://dx.doi.org/10.1117/3.732502.ch9

Chapter Page Count: 35 pages

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Front Matter

Part 1 System Overview
1. WDM, Fiber to the X, and HFC Systems: A Technical Review

2. Basic Structure of Optical Transceivers

3. Introduction to CATV Standards and Concepts of Operation

Part 2 Semiconductors and Passives
4. Introduction to Optical Fibers and Passive Optical Fiber Components

5. Optics, Modules, and Lenses

6. Semiconductor Laser Diode Fundamentals

7. Laser Dynamics: External Modulation for CATV and Fast Data Rates

8. Photodetectors

Part 3 RF and Control Concepts
9. Basic RF Definitions and IMD Effects on TV Picture

10. Introduction to Receiver Front-End Noise Modeling

11. Amplifier Analysis and Design Concepts

12. AGC Topologies and Concepts

13. Laser Power and Temperature Control Loops

Part 4 Introduction to CATV MODEM and Transmitters
14. Quadrature Amplitude Modulation (QAM) in CATV Optical Transmitters

15. Introduction to CATV MODEM

16. Linearization Techniques

17. System Link Budget Calculation and Impairment Aspects

Part 5 Digital Transceivers Performance
18. Introduction to Digital Data Signals and Design Constraints

19. Transceivers and Tunable Wavelength Transceiver Modules

Part 6 Integration and Testing
20. Cross-Talk Isolation

21. Test Setups

Back Matter

Preview

Chapter Contents

9.1 Distortions and Dynamic Range
9.2 1-dB Compression Point and IP3 Relations
9.3 Amplifier Gain Reduction Due to Third-Order Nonlinearity
9.4 Cross Modulation Effects
9.5 AM-to-PM Effects
9.6 Multitone CTB Relations
9.7 RF Lineups, NF Calculations, and Considerations
9.8 RF Lineups, P_1dB and IP₃ Calculations, and Considerations
9.9 Mismatch Effects
9.10 CSO and CTB Distortion Effects on TV Picture
9.11 Main Points of this Chapter
References

Excerpt

9.1 Distortions and Dynamic Range

Any active network can be described by the power series. This term is correct in the first approximation, when the system has no memory. Memory effects of an active system are caused by a time-varying phase response, which is, in turn, manifested in the frequency response. This phase response is referred to as the amplitude modulation (AM) to phase modulation (PM) characteristic. This phenomenon describes how the phase response is affected by input power. Under these terms of memory, the system is described by a Volterra series. The power series presentation here considers AM- to-PM effects only and the associated calculation is scalar only, which means a simple polynomial with real coefficients.

Assume an RF device such that its output voltage performance is described by power series at the operating frequency ω as follows:

where a₀ describes the dc component, (in ac coupling, this can be neglected) a₁x describes the linear gain, a₂x² describes the second-order distortion, a₃x³ describes the third-order distortion, and a_nXⁿ describes the nth-order distortion.

Since the transfer function is not linear, intermodulation interference occurs, In fact, this power series can be referred to as a sum of transfer functions, where each one generates distortions of a different order. Presenting these arguments in a log scale would result in a linear function where its slope is the distortion order (the Y axis represents power in dBm, since 20 log of the voltage is measured, and the X axis is the input power). Thus, it can be written as