William Poole Jr

Bit Error Rate testing on the MKW01 Sub GHz Transceiver.

Discussion created by William Poole Jr Employee on Oct 2, 2014

Bit Error Rate (BER) testing is the standard method of determining sensitivity of a receiver and other parameters such as blocking or adjacent channel interference where degradation of sensitivity is the determination of the effect of the parameter.

 

Typically the point where 0.1% BER occurs is the considered the test threshold. This is also written as a BER of 1e-3 or 10-3. That is, if 1 bit in 1000 has an error,  it becomes a noticeable problem. This would scramble about one of every 120 bytes, so the majority of packets of about that size would be damaged and communications interrupted.

 

The basic test would be to create some data, and use that to modulate an RF source, pass it through some transmission path to the Receiver Under Test, take the resulting data and compare it to the source data.

BER-basic.gif

 

BER is about the same regardless of what the content of the data transmitted is, but for reliable and repeatable testing it is common to use a Pseudo-Random bit stream, a random appearing string of 0’s and 1’s, as the data source. Since the mathematical means of generating a Pseudo-Random bit stream is standardized (making the data more “pseudo” than “random”) it is common for the source and comparison to use the same pattern and hence need not be co-located or connected.

 

Many signal generators have a built in BER test routine and PN code modulation capability. This puts both the PN generation and comparison in the same box. The modulated RF source is routed through a variable attenuator, creating the transmission path, allowing the exact signal level at the receiver input to be set as desired.

 

BER-SMIQ.jpg

 

The Rhode & Schwartz SMIQ is an example of such a signal generator with a BER test option.

 

When set to continuous receive mode, the data and data clock from the MKW01 receiver are routed out via DIO2 and DIO1, these can be fed to the BER test set and a sensitivity test performed.

 

Freescale Application Note AN4640 which can be found at:  http://cache.freescale.com/files/rf_if/doc/app_note/AN4640.pdf details setting up the R&S SMIQ for testing BER on the earlier Freescale MC12311 transceiver. For the MKW01Z128 set up is even easier, DIO1 & DIO2 are connected to J18 on the MRB-KW01 to facilitate BER testing.

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