Optimum noise measure configurations for transistor negative resistance amplifiers

Response to comments on “low‐noise one‐port microwave transistor amplifier”

“…This claim is confirmed as well by experimental results for noise figure presented in Figure 8 in [2] and in Figure 10 in [4], by subtracting the circulator and matching network losses (0.3 dB). Therefore, we do not agree with the conclusion given in [6,7], that the noise of the two-port LNA and a reflection amplifier (such as OPTA) are the same.…”

“…In order to study the noise characteristics of this kind of amplifiers, and perform a test of the proposed expressions [2] with minimum errors, we selected this frequency for the design of OPTA, due to the available circulator and the fact that its noise measurements are easy and direct (in the range of 10 MHz to 1600 MHz) using the noise figure meter HP8970A. Finally, we want to comment that the design methods presented in [6,7] are very interesting for obtaining the "optimum noise measure M", however, to our knowledge these are also approximations, where the first method uses a graphical solution and the second method…”

Noise analysis of reflection‐type microwave RTD amplifier

“…Additionally, the results of this work are compared with those of previously reported transistor‐based reflection‐type amplifiers [20–22]. The resonant tunnelling transistor (RTT)‐based amplifier, consisting of an RTT and an ideal signal source, exhibited a simulated NF of 0.55 dB with an operating frequency of 100 GHz [20].…”

“…Whereas the F SH equation in [20], given by 1 − eI B R D /(2 kT g ), deals with only the effect of the IBRD magnitude generated by the NDR device, (6) in this work, given by 1 − eI B R D /(2 kT g ) ′ (1–1/ G A ), reflects the effect of a finite gain of the IC as well as the effect of the I B R D magnitude. Field‐effect transistor (FET)‐based reflection amplifiers [21, 22], consisting of an FET and an input/output signal separating device of a circulator, were reported, demonstrating an NF of 1.4 dB (a noise measure of 0.406) at 9.7 GHz [21]. To achieve the input impedance of the FET with negative resistance, reactive elements were additionally inserted in the source and drain terminals of the FET.…”

“…To achieve the input impedance of the FET with negative resistance, reactive elements were additionally inserted in the source and drain terminals of the FET. The values of the reactive elements had to be selected carefully by introducing the graphical contour method [21] or the noise matrix approach [22] to obtain the lowest achievable NF. In contrast, it is not necessary to insert any additional elements for negative resistance into the RTD amplifier and a minimum NF value can be easily achieved through a simple procedure of locating the bias voltage near the point where the I B R D magnitude is minimal in Fig.…”