Affordable Design Techniques for Broad-Band DAS Expansion

Broadcasted on 1/26/2011

Rand Skopas

Rand Skopas
Dir. of Field Sales

Frequency expansion drives increasingly complex and more costly broad-band DAS solutions. Leading DAS Designers are now beginning to offset some of this cost by using Signal Tappers in place of more costly Directional Couplers. Microlab now offers the highest-performance/most cost-effective Signal Tapper solution available on the market. In this webinar, the concept of the Signal Tapper will be introduced. This webinar will also include an analysis of the performance characteristics and recommended design revisions that will enable tremendous cost savings without any sacrifice to over-all system performance.

Webinar Q&A

Below are questions that were recieved during the webinar.

Are there any differences in the way that Signal Tappers are specified when compared to Directional Couplers?

The most significant point of difference in the way that the units are specified is related to the dB or coupling value. In a directional coupler, the reference is between the input and the coupled port (as an example, in a 10dB directional coupler the output at the coupled port is -10dB down from the power level at the input) For Signal Tappers, the reference value represents the power differential between the output and the coupled port. Additional points of difference are in the directivity which is typically ~20dB for Directional Couplers, and not stated at all for Signal Tappers.

What impact could the lack of directivity (and resulting isolation) have on over-all system performance?

On the TX path, there is really very little impact at all on the system performance, the only potential issue would occur on the RX path, where the signal isolation between ports would be equal to the directivity plus the coupled value.  Although isolation between signals is a desired characteristic, the RX signal levels are typically so low, that the actual difference in system performance is almost imperceptible.  Additionally, if you use the proper compensation techniques during the design phase (and today’s iBwave and software package can help here) any negative impact on performance can be mitigated.)

What kinds of customers are using Signal Tappers rather than Directional Couplers?

The real answer here is that we are seeing customer usage at all levels of the DAS market.  OEM customers like Nokia, Ericsson and others have recognized the over-all benefits of Signal Tapper.  Many of the carriers, such as Verizon, are already deploying these types of designs within their DAS architecture.  We are also seeing extensive usage through our Distribution Channels in the US such as Tessco, Talley and Hutton.  This tells us that many of the smaller System Integrators are deploying these units in their systems as well.