Intermodulation product

Klystron Hnearity (both ampHtude and phase) is considered fair to good. For RF power, several decibels below saturation, the ampHtude Hnearity exhibits a curvature as shown in Fig. 6.12. As drive is increased, the RF output reaches saturation and further increases in drive reduces power output. The Hnearity curvature and saturation characteristic will generate harmonic and intermodulation products, which maybe filtered... 

Another very important measure of Hnearity is the relative level of generated odd order intermodulation products in the ampHfier. For intermodulation to take place, two or more signals must exist at the same time as a combined input signal. They must be at different frequencies, but near enough to each other so that they both fit within the passband of the ampHfier. A suitable example input signal is of the form of Eq. (7.23)... 

FIGURE 7.45 For intermodulation distortion analysis, the amplifier undertest maybe thought of as an ideal amplifier shunted by a mixer that creates the intermodulation product components. Multiple frequency signal components make up the inputs to the mixer. 

TABLE 7.2 Some Third-Order Intermodulation Products for a Three-Tone Signal... 

Why not just merge two or more signals together in a tee and send them to a common antenna Because unless they are stopped by some means, the signals will backfeed up each other s input lines and into the transmitters where spurious intermodulation products (spurs) will be generated within the final cavities of the transmitters. These spurs will then be transmitted up to the antenna and broadcast FCC rules specify that spurs must be 80 dB below the carrier frequency, so care must be taken to prevent them. 

FDMA impHes that several individual carriers coexist in the transmit amplifiers. To operate the amplifiers in a quasilinear region relative to their saturated output power to limit intermodulation products, the amplifiers, must be operated in a backed off condition. For example, to limit third-order intermodulation... 

Backoff Amplifiers are not linear devices when operated near saturation. To reduce intermodulation products for multiple carriers, the drive signal is reduced or backed off. Input backoff is the decibel difference between the input power required for saturation and that employed. Output backoff refers to the reduction in output power relative to saturation. 

Multitone test techniques use carefully designed mixtures of tones applied simultaneously to the device under test (DUT). The individual tone elements have weU-defined frequency, phase, and amplitude relationships. The frequencies of multitone components are selected to avoid mathematically predictable harmonic and intermodulation products that would fall on or near any of the fundamentals. The phase of each tone is fixed, but randomly selected relative to each of the other tones. Amplitude relationships may vary, depending on the device under test. 

Noise power ratio (NPR) The ratio, expressed in decibels, of signal power to intermodulation product power plus residual noise power, measured at the baseband level. 

EMI refers to EM energy that interrupts, obstructs, or otherwise degrades or limits the effective performance of electrical equipment. It is any EM disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics and electrical equipment. It can be induced intentionally, as in some forms of electronic warfare, or unintentionally, as a result of spurious emissions and responses, intermodulation products, and the like. EMI is a system safety concern because many safety-critical electronic systems... 

The reaction of elemental phosphorus with hydrogen was also used for PH2 production. H atoms from MW-discharged H2 were passed over the red modification, and the resulting PH2 was detected by LIF [51, 52], IMF (intermodulated fluorescence) [27], or MW spectroscopy [14]. The reaction of phosphorus vapor with atomic or molecular hydrogen did not lead to any PH2 electronic emission [18]. Emission bands, which had been observed during the reaction of elemental P with atomic H, were first attributed to PH2 [53,54], but they were later shown to be due to HPO [55]. 

Intermodulation The production, in a nonlinear transducer element, of frequencies corresponding to the sums and differences of the fundamentals and harmonics of two or more frequencies that are... 

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