Noise analysis of microwave circuits and systems has been a research issue for many decades. A circuit's noise performance is given in terms of noise figure or noise temperature. The signal energy exiting a generator or antenna is amplified or attenuated in passing from the input to the output of a two-port network. Along this signal path, thermal energy in the components add noise to the signal. In some applications, e. g., in a radar receiver, it is necessary to anticipate the amount of noise that circuits add to the signal path. When receiving a radar pulse, the receiver will also add some noise to the signal. This added noise masks the pulses, which will make it more difficult to detect them. When the ratio of pulse power to noise becomes too low, the pulse and the target cannot be detected. Thus, a receiver that adds the least amount of noise possible is desirable. There is a similar requirement for a microwave radio. A microwave signal is modulated with data and transmitted from an antenna on top of a mountain. A receiver on a neighboring mountain ridge receives this signal and extracts the data. When the signal becomes overwhelmed by noise, however, the data stream can no longer be reconstructed.

Chapter Contents:

• 8.1 Introduction
• 8.2 Noise Model
• 8.3 Noise Power Waves
• 8.4 Noise Figure
• 8.5 Measuring Noise Figure
• 8.6 Summary
• 8.7 Problems
• 8.8 References

Inspec keywords: circuit noise; microwave amplifiers

Other keywords: circuit noise performance; signal path; microwave signal; radar pulse; microwave radio; signal energy; data stream; thermal energy; noise analysis; noise temperature; noise figure; two-port network; small signal microwave amplifier design; microwave circuits; pulse power

Subjects: Microwave circuits and devices; Amplifiers