featuring Dynasys de-Q ^TM tuning

A High Frequency Antenna for RFID is generally a device that receives an electrical energy wave from an “RFID Reader” and consequently emits a magnetic wave into space, or vice versa. These antenna devices could appear as simple as a paper clip or become as complex as a multi-element array.

The three most important aspects of the High frequency Antenna which will allow it to act as an efficient radiator in an RFID application is the following:

1.) The center frequency tuning should be resonant at 13.56 MHz. This resonance is obtained by adjusting capacitors and inductors such that one cancels the other’s effects. When the capacitive reactance equals the inductive reactance only the real, or resistive, part of the impedance remains. This phenomenon should be forced to occur only at 13.56 MHz.

2.) The output terminals from the RFID Reader are typically driven from a 50 ohm, real source impedance. The transmission cable is also usually a 50 ohm impedance cable. In order to get maximum power transfer of the energy available into the antenna circuit, and possibly prevent damage to the Reader, the input impedance of the antenna should also be adjusted to match the 50 ohm transmission system.

3.) The antenna circuit should allow the energy of the data signals, as well as the carrier signal centered at 13.56 MHz to be emitted into space. The data energy is in the form of an upper and lower sideband, centered about the 13.56 MHz carrier. These sidebands are accountable for the “Bandwidth” of the system. Bandwidth is sometimes expressed as the “Quality Factor” or just plain “Q” of the circuit.

de-Q^TM RFID Antennas from Dynasys

Dynasys antennas may be ordered with our excluse de-Q ^TM feature. An explanation of de-Q ^TM follows:

Each antenna has a set of electronic components that determines the impedance, “Q” and resonant frequency of its circuit. When using multiple antennas in close proximity Dynasys recommends that you de-tune all other circuits in the vicinity while the reader's antenna is interrogating.

De-tuning is accomplished by creating a low impedance across a capacitor or inductive element. By effectively shorting these reactive components the resonant frequency is shifted so far out of the band-pass that its presence is insignificant to the near-field energy pattern. This is accomplished in effect by shunting across the reactive elements.

This feature is ideal for applications such as electronic cabinets with multiple shelves.

These reactive component changes force the resonant frequency of the circuit to move out of the bandpass of the receiver. The Dynasys de-Q ^TM antenna phenomenon can also be utilized to detect the presence of objects in the proximity of a transponder position causing it to de-tune, such as indicating that a particular item is in or out of stock within a Smart Shelf.

An example of de-tuning is where an RFID Reader detects the presence of an associated nearby tag. If material is placed in proximity to the tag containing a high moisture or metal content it will in effect de-tune that tag, so much so, that it can no longer be detected by the RFID Reader.

The loss of that tag's detection is indicative of interfering material being present near the tag. If the tag is successfully detected that would be indicative of no interfering material being present.

de-Q^TM RFID Antennas from Dynasys provide the features required for custom and complex RFID antenna applications.

Choosing the proper antenna for your High Frequency RFID system is a complex task. Dynasys manufactures its own line of High Frequency antennas as well as carrying a number of other manufacturer’s antennas. Please call your Dynasys Sales Engineer, an expert in selecting the proper antenna for your application.

Learn more about RFID Antennas here:
Antenna Considerations for RFID Applications
RFID Shelf Antennas, RFID Cabinets & Smart Shelves