Linear microwave amplification with Gunn oscillators

Linear microwave amplifiers with continuous power outputs of 100 mW have been constructed utilizing the frequency-independent negative conductance observed externally in Gunn oscillators. This negative conductance is exhibited only in samples containing propagating dipole layers, in other words,
n_{0} . L
must be larger than 10
¹²
cm
^-2
for n-GaAs. The output power obtainable from this amplifier is substantially larger than that from a subcritically doped GaAs amplifier (
n_{0} . L < 10^{12}
cm
^-2
) because
n_{0} . L
can be increased. Power output and efficiency are discussed in terms of n
0
and
L
. The upper-frequency limit for amplification is determined by the time the domain takes to readjust itself after a change of external voltage which leads to an upper limit for the
f. L
product (about 10
⁸
cm/s). The essential feature of the amplifier circuit is to provide both a short circuit at the Gunn oscillation frequency and a broadband circuit at the signal frequency. An average gain of 3 dB was exhibited from 5.5 GHz to 6.5 GHz. Gain compression of 1 dB occurred at 60 mW output power with 9 dB gain, while the noise figure was about 19 dB.