Citation
Abstract
This article presents the derivations of both the exact and approximate equations for determining the follow-up receiver noise temperature from measured output powers when the first-stage low-noise amplifier (LNA) power supply is turned on and ofi. Although approximate equations have been used by DSN engineers since the early 1960s when the LNA was a maser, it is important to know whether the equation and experimental procedure are still valid when the LNA is a cryogenically cooled high-electron mobility transistor (HEMT) rather than a maser. In this article, it is shown that the approximate equations and experimental procedure being used for masers can also be used for HEMTs for obtaining an accurate value of the follow-up receiver temperature. However, if the first stage amplifier is not cryogenically cooled, but is at room temperature, it is shown that, if the approximate equation is used, a correction factor (also derived in this article) might have to be applied in order to get an accurate value. Since the derivations do not appear to be documented in any reports, the equations are rederived and presented in this article.
Keywords
Details
- Volume
- 42-143
- Published
- November 15, 2000
- Pages
- 1–11
- File Size
- 212.5 KB