Antenna, antenna feed and losses

[zainka]

Hi

I youst wondered

I have seen some designs around where the matched antenna is placed somewhat offside according to the pcb with a radio module often seen nowadays (like radiometrics, linx and so on, no specific), and between the antenna input/output of the module, and the antenna itself, I have seen there has been used a simple wire with no screen/shield on it to conect the items.

Wouldn't this affect the.. well i am not to clever with the terminology, but the antenna impedance and effectivity of the system. wouldn't this extra non shielded wire actually become a part of the antenna???

joust asking since I am into a similar project my self using a lynx transceiver.

 

[dinone]

Certainly the effect of this simple wire with no screen/shield deeply impact the matching condition: you need to have a 50 phm cable/wire to connect the antenna to the receiver. Regarding your question regarding the possibility to "become a part of antenna" it's depend on the type the antenna to use (no if the antenna is a patch), from the frequency and so on. For sure I don't work with wire without ground or shield.

By

 

[vfone]

A simple wire (shielded or not, with or without ground) is equivalent with a parasitic inductance.
If the designer integrates this inductance into the matching network of the antenna, the loss through this wire will be minimal.