JN517X Datasheet, PDF (28/100 Pages) NXP Semiconductors – Supports multiple network stacks

NXP Semiconductors
JN517x
IEEE802.15.4 Wireless Microcontroller
9.7.1.2 Antenna diversity
Support is provided for antenna diversity, which is a technique that maximizes the
performance of an antenna system. It allows the radio to switch between two antennas
that have very low correlation between their received signals. Typically, this is achieved by
spacing two antennae around 0.25 wavelengths apart or by using 2 orthogonal
polarizations. So, if a packet is transmitted and no acknowledgement is received, the
radio system can switch to the other antenna for the retry, with a different probability of
success.
Additionally antenna diversity can be enabled while in receive mode waiting for a packet.
The JN517x measures the received energy in the relevant radio channel every 40 s and
the measured energy level is compared with a pre-set energy threshold, which can be set
by the application program. The JN517x device will automatically switch the antenna if the
measurement is below this threshold, except if waiting for an acknowledgement from a
previous transmission or in the process of receiving a packet, where it will wait until this
has finished. Also, it will not switch if a preamble symbol having a signal quality above a
minimum specified threshold has not been detected in the last 40 s.
Both modes can be used at once and use the same ADO (SELA) and ADE (SELB)
outputs to control the external switch.
The JN517x provides an output (ADO) on one of DIO0, DIO4 and DO1 that is asserted on
odd-numbered retries and optionally its complement (ADE) on one of DIO1, DIO5 and
DO0, that can be used to control an antenna switch; this enables antenna diversity to be
implemented easily (see Figure 17 and Figure 18).
antenna A antenna B
SEL
ADO
SELB
ADE
A
B
RF switch: single-pole,
double-throw (SPDT)
COM
device RF port
aaa-015444
Fig 17. Simple antenna diversity implementation using external RF switch
JN517X
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2.0 — 8 November 2016
© NXP Semiconductors N.V. 2016. All rights reserved.
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