433MHz helical PCB antenna impedance

Konstantin Bilozor

Hello,

I design matching circuit for 433 MHz helical PCB antenna (13 turns) used in reference design (swrr081). I can find only documents which report impedance for 868 MHz helical PCB antenna, but not for 433 MHz.

Maybe someone have measured impedance? Can you provide me this number?

Best regards,

Konstantin

over 10 years ago

0 RGW over 10 years ago

TI__Mastermind 33170 points

The impedance of the antenna when on an EM whilst inserted onto a TRXEB is approx. 10 -j210:

By using a 0.9 pF and 56 nH shunt to GND towards the antenna, the match will be approx. 50 ohm.

0 Konstantin Bilozor over 10 years ago in reply to RGW

Prodigy 135 points

Hello Richard,

Please, see the screenshot attached below.

If I plot matching network with those component values, I get a point which is far away from 50 Ohm.

Hope to hear from you,

Konstantin

0 TER over 10 years ago in reply to Konstantin Bilozor

TI__Guru**** 317180 points

- Real components have a different behavior compared to ideal components which are used in the smith chart program.
- Parasitics on the PCB also contribute.

In real life the match will always be different than what a smith chart program estimate due to this.

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433MHz helical PCB antenna impedance