Novelties in microwave mixer design: New diode model, schematics and layout possibilities

Novelties in microwave mixer design: New diode model, schematics and layout possibilities

Author: 
Kristóf Máté Osbáth, Gergely Mészáros and János Ladvánszky
Abstract: 

Design steps of a 10 GHz diode mixer of a novel structure have been reported. In our earlier publication [1], the diode half H mixer was discovered at MHz frequencies (Fig. 1). In this paper, we show the 10 GHz realization of this mixer. First, diode modelling is detailed. A novel nonlinear DC model comprising of two ideal diodes in series with different parameters improves model accuracy compared to the case of one diode. High frequency linear diode model applies the same trick: the two diodes used for modelling are in series.Interconnection nodes of the package model are grounded by capacitors. Nonlinear DC and linear high frequency models are combined and remaining model parameters are identified using bias dependent S-parameters. Then the schematics of the low frequency mixer realization is transformed in order to be realizable at microwaves. We use a rat race hybrid as a transformer realization. Novelty is that a specific port of the rat race is used both as the LO and the IF ports, with LO to IF isolation provided by a low pass IF filter. In order to draw the mixer layout conveniently, we use an oval realization of the rat race hybrid. The mixer has been realized on Rogers’s 4003C type duroid.

Paper No: 
1571