User's Manual
Table Of Contents
- Contents
- 1 Overview
- 2 DC and AC Characteristics
- 3 Electrical Interface
- 4 SPI Interface and Sequences
- 5 Power States
- 6 Messaging Protocol
- 7 microNode Provisioning
- 8 Antenna Diversity
- 9 Regulatory Considerations
- 10 Manufacturing Considerations
- 11 Errata
- Appendix A Abbreviations and Terms
- Appendix B PCB Land Pattern and Vias
- Appendix C REACH AND RoHS Compliance
- Appendix D On-Ramp Wireless RMA Process
- Appendix E microNode Mechanical Drawing
On-Ramp Wireless, Inc. 38 014-0033-00 Rev. H
8 Antenna Diversity
The microNode supports Antenna Diversity for optimal System performance. In many cases, the
microNode and Host system are mounted in fixed locations that often experience nulls in the RF
coverage. Antenna Diversity can help with optimization of the RX and TX paths. In marginal
coverage areas, an RF null could easily disadvantage the microNode to force it to transmit at a
higher TX Power (more current) or cause network loss and frequent rescanning to reacquire the
network (again, more current). These scenarios produce customer dissatisfaction as well as
increased battery drain. On-Ramp Wireless has designed numerous diversity solutions and has
found the circuit in shown in the following figure to work well.
NOTES:
1. It is not normally recommended to use the Node’s 3V3 output. However, this is
one ideal case for its use. VCC of U402 can use the Node’s 3V3 to allow optimal
power consumption. If the Node turns off its 3V3 supply, it cannot use its RF path
and the entire diversity circuit powers down.
2. The antennas (and associated matching values) are dependent on the antennas
used and the PCB layout.
3. The U400 CEL part crosses to a Skyworks AS214-92LF.
Figure 21. Antenna Diversity Circuit