Noise conversion of Schottky diodes in mm-wave detectors under different nonlinear regimes: modeling and simulation versus measurement je ' ssica gutie ' rrez, kaoutar zeljami, enrique villa, beatriz aja, maria luisa de la fuente, sergio sancho and juan pablo pascual This paper presents and discusses several methods for predicting the low-frequency (LF) noise at the output of a mm-wave detector. These methods are based on the extraction of LF noise source parameters from the single diode under a specific set of bias conditions and the transfer or conversion of these noise sources, under different operating conditions including cyclostationary regime, to the quasi-dc output of a mm-wave detector constructed with the same model of diode. The noise analysis is based on a conversion-matrix type formulation, which relates the carrier noisy sidebands of the input signal with the detector output spectrum through a pair of transfer functions obtained in commercial software. Measurements of detectors in individual and differential setups will be presented and compared with predictions.
I . I N T R O D U C T I O NThe low-frequency (LF) noise at the output of a detector may contribute to increasing system instability, becoming a source of error, for example in the operation of radiometers. Particularly, to establish appropriate switching frequencies in switched radiometer systems, it is especially relevant to know the knee frequency of devices [1]. The presence of a switching frequency in these systems transforms the noise analysis into a cyclostationary problem. Moreover, the system's knee frequency may vary depending on the operation mode of the devices. Rigorous mathematical treatment of several types of deterministic and random signals flowing through a nonlinearity is a classic topic [2], which should be reconsidered as simulation tools evolve and the requirements of systems become stricter. On the other hand, in general, apart from phase noise (PHN) in oscillators, simulation tool studies have paid limited attention to LF noise. Therefore, it is considered of great interest to have an accurate characterization of devices' LF noise together with reliable simulation tools for predicting its conversion to the system output, depending on the device operation regimes.The relevance of the device operation regime is shown in [3], which provides empirical evidence of the shot noise deviation with respect to the conventional model in a large-signal pumped Schottky diode, proposing an alternative model based, not on the mean current of the device, but on the smallsignal resistance, supported by a classic reference [4] and in agreement with the distinction between shot noise with constant and with time-varying rate presented in [5]. In [6], the simulation of cyclostationary noise is treated from a physically-based point of view. In [7], the use of time-domain and transient-envelope tools is proposed for the simulation of switching radiometer systems handling noisy broadband signals. Nevertheless, the frequency domain is usuall...