Antenna of HL7800

IoT Modules
1

Hi,
Currently I am on a project intended to use HL7800 module, which based on CAT M1. It is used in Australia so it will be used in band 28. Could you give me some guide on how to select the antenna? An external or an internal one? Thanks.

2

Plus, do you think it possible to have one (or two) layout PCB antenna? Anyway I prefer internal antenna.

3

Hi @yinghuang

Depending of your application you can select either PCB, internal or external type. What is important is to make sure your antenna and PCB RF track meet the requirement described in the HL7800 PTS available on the source.

https://source.sierrawireless.com/resources/airprime/hardware_specs_user_guides/airprime_hl7800_and_hl7800-m_product_technical_specification/

Check section 3.19.1 RF connection.

A 50Ω (with maximum VSWR 1.1:1, and 0.5dB loss) RF track is recommended to be connected to standard RF connectors such as SMA, UFL, etc. for antenna connection.

The antenna must meet the following specification for each RF band targeted:
Impedance: 50Ω
VSWR max Rx/Tx: 2.5:1

Hope it helps.

4

Hi, Sierra_bbo,

I find an antenna from Linx, with part number being ANT-LTE-CER. Do you think it suitable?

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5

A solderable antenna with VSWR max 2.5:1 in Band 28 for Cat M1 seems difficult. The application of this project is just one communication module Cat M1 and with a plastic enclosure, powered by battery.

6

Hi @Yinghuang

This antenna is not really suitable for use on B28. VSWR 4:1.

If you use this antenna, it will probably work in dense urban environment. However if you target more rural or challenging environment such as underground, it will affect the performance.

As an example, in the mangOH Red dev kit we provide an antenna from Taoglas Ref: FXUB63.

This antenna has a max VSWR on B28 of 2:1.

In conclusion, if you only target B28, you’d better select a different part

7

Well received.

BTW, do you think that by careful designing an inverted F PCB antenna can meet the requirement of VSWR? The Taoglas antenna is expensive.

8

Hi, bbo,
I am reading the spec of HL7800. About the UART connection between HL7800 and host MCU, there are 8-wire, 4-wire and 2-wire modes. But I cannot see the descriptions about these modes. In practical which mode should I choose? Meanwhile where can I find the descriptions about this please? Thanks.

9

Hi @yinghuang,

You should be able to meet the VSWR requirement with any type of antenna. Now, unless you have previous experience in the topic, I would not recommend you to design your antenna. Better find an existing solution meant to perform well in the targeted bands.

The Taoglas PN is a wide band antenna. If you only target the B28, you should be able to find so cheaper option.

Regarding your question related to UART wiring, please create a new post since it is not related to the initial subject.

Thanks

10

Well received, thank you.