Project topics and materials
Get Complete Project Material File(s) Now! »
Characteristics of the Mixing Function
The principle parameters required to characterize the mixer performance [19] [20] are conversion gain ( ), frequency range, third-order intercept point (IP3), spurious free dynamic range (SFDR), gain compression, and isolation which are defined in the following sections:
Conversion Gain
Conversion gain is defined as the ratio in powers between the output IF/RF power level and the input RF/IF power level. It can be a gain or a loss depending on the efficiency of the mixing process which is based on the type of the mixer.
Frequency Range
The frequency range is the range of frequencies over which the mixer will meet the specification parameters. The circuit construction of components inside a mixer will indicate the frequency range over which the mixer can run [21]. The frequency range of RF/LO signals is changed from a mixer to another one.
Third-Order Intercept Point
Two-tone third order intermodulation operates when two RF/IF signals enter simultaneously the RF/IF port of a mixer and they interact. Two-tone signals are used in predicting the nonlinear behavior of a mixer as the input RF/IF power increases. We consider two-tone signals at frequencies and which have the same amplitude injected into the RF/IF port of a mixer and the LO signal injected into its LO port. Third order and intermodulation occurs at the mixer output at frequencies which are very close to and as shown in Figure 1.4. Third order products will increase by 3 dB for each dB increment at the input.
Spurious Free Dynamic Range
The dynamic range of a mixer is defined as the range of power over which it provides useful operation. The spurious free dynamic range (SFDR) ⁄ is commonly/ used to describe the dynamic range of RF systems. The SFDR denoted in is the difference in powers between the first order output signal and the third order intermodulation products at the mixer output when they have the same power as the noise floor ( ), see Figure 1.5.
Gain Compression
Gain compression is a measure of the linearity of the mixer which is the useful index of distortion generation. It is specified in terms of an input power level at which the conversion gain drops off by 1 dB as illustrated in Figure 1.5.
Isolation
Isolation (Iso) denoted in dB is a measure of the amount of power at the output port of a mixer. Iso is defined as the ratio of power between an IF/RF signal and a LO signal. Three types of isolation are quoted in mixers: LO-RF isolation, LO-IF isolation, and RF-IF isolation. The LO-RF isolation is the ratio of the LO power into the RF one as defined in Equation (1.11). It is important when the mixer is used as an up-converter. The LO-IF isolation is the ratio of the LO power into the IF one as given in Equation (1.12). It is important when the mixer is used for a down-converter. The RF-IF isolation is the ratio of the RF power into the IF one as written in Equation (1.13).
Frequency Up and Down-Conversion Theoretical Responses by Small Signal Analysis
The frequency up and down-conversion theoretical responses are calculated by small signal analysis in order to highlight the origin of the differences between up and down-conversion responses as it was shown in the above paragraph. In order to proceed a small signal analysis, the following assumptions are done:
The optical data input power ����,� is injected into each ����, where � = � for ���� and � = � for ����, at the wavelength ���� as plotted in Figure 3.11. It is worth noting that ���� and ���� respectively correspond to SOA1 and SOA2 in the architecture of the used SOA-MZI in the experimental results.
Third Order Input Intercept Point
Two tone third order input intercept point (IIP3) [137] [138] [139] is obtained by measuring the third order terms generated in presence of two incident equal amplitude optical signals at the common input port (C) of the SOA-MZI. The experimental setup shown in Figure 3.20 is used to measure the IIP3. Two tone signals at frequencies � and � are generated by an arbitrary waveform generator (AWG) after filtering by a low pass filter (LPF) and attenuated by a variable electrical attenuator (EAtt).
Table of contents :
Acknowledgments
Table of Contents
Introduction
Chapter One Optical and Electro-Optical Mixing Generalities
1.1 Introduction
1.2 Mixing Function
1.2.1 Mixing Process
1.2.2 Characteristics of the Mixing Function
1.3 Optical Mixing for RF Signals
1.3.1 Implementation Techniques of Optical Mixers for RF Signals
1.3.2 Comparison between Different Techniques of Optical Mixers
1.4 Mixing by the Sampling Method
1.4.1 Up-Conversion by Periodic Sampling
1.4.2 Down-Conversion by Bandpass Sampling
1.4.3 Sampling Pulse Width
1.4.4 Receiver and Sampling Noise
1.5 Conclusion
Chapter Two Static and Dynamic Characteristics of a Semiconductor Optical Amplifier Mach– Zehnder Interferometer
2.1 Introduction
2.2 Semiconductor Optical Amplifier
2.2.1 Introduction
2.2.2 SOA Structure
2.2.3 Recombination Processes in a SOA
2.2.4 SOA Fundamentals
2.2.5 SOA Nonlinearities
2.2.6 Dynamic Response
2.3 Characteristics of a SOA-MZI Structure
2.3.1 Static Characteristic of a SOA-MZI
2.3.2 Dynamic Characteristic of a SOA-MZI
2.4 Experimental Characterizations of the Used SOA-MZI
2.4.1 Static Characteristic
2.4.2 Dynamic Characteristic
2.5 Conclusion
Chapter Three All-Optical Sampling Mixing Based on a SOA-MZI
3.1 Principle of All-Optical Mixing Based on a SOA-MZI
3.2 Mixer Characteristics
3.2.1 Experimental Setup of the All-Optical Mixer Characterization
3.2.2 Optical Pulse Source Characteristics and Its Influence on the Data Signal at the SOA-MZI Output
3.2.3 Frequency Up and Down-Conversion Experimental Spectrums with an IF/RF Sinusoidal Signal
3.2.4 Experimental Results of Up and Down-Conversion Gains
3.2.5 Frequency Up and Down-Conversion Theoretical Responses by Small Signal Analysis
3.2.6 Qualitative Analysis of Frequency Up and Down-Conversion Theoretical Responses
3.2.7 Isolation
3.2.8 Third Order Input Intercept Point
3.3 Frequency Conversion of Complex Modulated Data Based on the SOA-MZI
3.3.1 QPSK and OFDM Modulation Formats
3.3.2 Error Vector Magnitude (EVM)
3.3.3 Frequency Up-Converted Modulated Data Results
3.3.4 Frequency Down-Converted Modulated Data Results
3.4 Conclusion
Chapter Four Frequency Conversion by Using the SOA-MZI Differential Configuration
4.1 Principle of All-Optical Mixing Based on the SOA-MZI Differential Configuration
4.2 Frequency Conversion Based on the SOA-MZI Differential Configuration
4.2.1 Experimental Setup Description
4.2.2 Conversion Gain
4.2.3 Frequency Conversion of a QPSK Signal
4.2.4 Frequency Conversion of an OFDM Signal
4.3 Conclusion
Conclusion and Perspectives
Bibliography
