Passive microwave circuits - Reciprocal liabilities

Mainly telecommunications systems and radars are made up of a large assembly of circuits, which are themselves manufactured using active or passive components. This article deals only with reciprocal circuits and passive components, while non-reciprocal elements are dealt with in the following article. .

After a brief description of their operating principle, we'll focus on a number of technological pointers to help you understand their practical characteristics and field of application.

Based on what we have said in the articles and , it is clear that the majority of circuits operating at frequencies up to around twenty gigahertz will be based on coaxial, microstrip or coplanar technology. For higher frequencies, i.e. millimeter-wave frequencies, waveguides are predominantly used. For frequencies above 200 GHz, circuits designed using quasi-optical methods are increasingly used.

Passive microwave circuit components are classified according to the number of accesses. The greater their number, the greater the complexity and the more sophisticated the function performed. We will cover :

• dipoles that reflect energy (short circuits), absorb it entirely (matched charges) or partially (sliding charges);

• quadrupoles that modify the amplitude (attenuators) or phase (phase shifters) of the electromagnetic wave, as well as quadrupoles that modify the direction of wave propagation (elbows, twists, rotary joints) or change the cross-section of the guiding structure;

• tees, power dividers and directional couplers to send a wave from one incident channel to two or more others.

To characterize such devices, the very special technique of "s" parameters will be introduced, described and applied.