Noise Figure and Sensitivity of a Superregenerative Parametric Amplifier

Superregeneration is a process in which a circuit is made to oscillate intermittently. In this paper the characteristics of superregeneration in a low-noise cavity-type parametric amplifier are examined both theoretically and experimentally. The superregenerative parametric amplifier is a device performing the functions of both sampling and amplification. Incorporated with a detector, this device can be used for video-modulated signal reception. Because of the internal sampling operation, the frequency of the modulation on the input signal must be less than half the sampling frequency in order for the information to be recovered without distortion. However, input noise and circuit noise may have a bandwidth much wider than half the sampling frequency and therefore produce a folded spectrum at the output of the amplifier. This fact complicates the use of noise figure in determining the sensitivity of such an amplifier. For many applications, sensitivity is a more meaningful figure of merit than noise figure. This paper discusses sensitivity and noise figure and derives expressions for the noise figure. The derivations take into proper account the noise spectrum folding associated with the sampling operation. Experimental data on sensitivity and noise figure are presented.