The DR resonators are used as resonating element in filters, oscillators and similar, by replacing lines or mechanical cavity. Can be either a puck in TE (Transverse Electric) modes, used over 2 GHz, or square metallic cavity in TEM (Transverse ElectroMagnetic) modes up to 5 GHz.
The advantages are the high Q, a good stability (a few ppm/°C), low phase noise and small size, a classic example is in TV Sat LNB where the puck is used in the LO oscillating circuit. If they are used as filter they have a better Q and a better stability compared to a mechanical filter or as oscillator the have a better stability but above all a better phase noise.
If they are used properly in well designed oscillating circuits, for example in VCOs, the improvement in terms of phase noise is quite remarkable and above all expectations.
INFORMATION ON FREQUENCY: The frequency in DR resonators what is a controversial and difficult to establish matter. The verification is performed by each manufacturer in a different way and with different test jig, it follows that the end user will have differences on the frequency. The differences are due also to the manner of use, for example as a cavity filter or oscillating circuit, depending on the type of support used at the base or on the variation of the tuning element and on the shape of the container, etc... We usually perform tests in repetitive way using always the same test jig. For the TE pucks the frequency indicated in the description is the lowest obtainable considering that it can be rised with a metallic tuning element or decreased with a little deposition of alumina on the top.
SUPPORT FOR DR OR TUNING ELEMENT (for TE pucks) At the base of the pad DR it is normally used an "amorphous" element as insulating support with a good hardness and with good thermal stability, is not recommended teflon or mica is therefore preferable to use quartz, alumina and ceramics for microwave. In fact this is the mounting that experimentally has given excellent results in terms of Q and stability vs. temperature (for the choice of the alumina you see in LAMINATES section). The same material can be glued to the top of the puck as tuning, being able to easily shatter in small pieces according to the need. Some of our puck are already equipped with amorphous support glued at the base. For adjusting and tuning continuosly you can use the microwave tuning elements.
