Questions and discussions about the antennas for the TD RF modules.
Posts: 51
Joined: Mon Jul 06, 2015 4:06 pm

Antenna Bandwidth

by ramon2015 Thu Nov 19, 2015 11:55 am


I am designning the antenna matching network and I would like to know the recomended bandwidth, center frequency and VSWR for TD1208.
In case I want to use both Uplink and Downlink channels I should use an intermediate frequency as center frequency?
or is it common to unbalance the bandwidth to improve one or other link?

Regards, Ramon.
Posts: 3
Joined: Tue Nov 03, 2015 12:51 pm

Re: Antenna Bandwidth

by yluque Tue Nov 24, 2015 7:58 am

Dear Ramon,

To design the antenna matching, you must match your antenna on 868.13MHz central frequency with bandwith of 500kHz. Due to this Ultra Narrow Band, i think you can obtain an VSWR<2.
As you know it is necessary to make matching of your antenna with your final casing. In order to limit the casing influence, make sure to leave at least 7mm away between antenna and housing. Also favor the use of an 1/4 Wave antenna or 1/2 Wave antenna if it is possible.

Best regards,

Yohann Luque
Posts: 51
Joined: Mon Jul 06, 2015 4:06 pm

Re: Antenna Bandwidth

by ramon2015 Mon Feb 08, 2016 11:49 am

Dear Yohan,

Thanks for your answer.

You have suggested to match the antenna at 868,13 MHz keeping VSWR < 2 for a BW= 500 kHz (+/- 250Khz), right?

868,13 Mhz is the center frequency for te UpLink sub-band, and
869,525 MHz is the center frequency for te DownLink sub-band

Since I may need the DL message I would like to balance the tuning so both links are performing more or less the same.
What do you think I use a center freq as 868,64 Mhz in order to keeo centered between both link bands?
Or is it still recommended (even if I need UL & DL) to match at the UL center freq as you suggested in the begining?

Regards, Ramon.
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