1 / 8

Understanding dB: Power Ratios and Logarithmic Gains in Communication Systems

This article explores the concept of decibels (dB) in the context of power ratios and signal gains, particularly in communication systems like mobile networks. It illustrates how to calculate gains from amplifiers using both linear and logarithmic scales. By comparing the power output of base stations and mobile devices, it reveals the significance of dB measurements in understanding power differences. The importance of using the appropriate units for accurate communication of parameters is also discussed, ensuring clear and effective information exchange in technical fields.

ludlow
Download Presentation

Understanding dB: Power Ratios and Logarithmic Gains in Communication Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ｄB or not dB http://www.unav.es/adi/servlet/Web2?course=80957943&action=verWeb&pagina=21510

  2. ｄB or not dB • Ratio of two quantities. • Large numerical ranges. Example • Mobile radiobase station transmits approx. a power of 80W • Mobile phone receives only about 0.000 000 002W = 2nW • 2nW is a 0.000 000 002 5% of 80W • The base station in our example transmits at +49 dBm • The mobile phone receives -57 dBm • Power difference of +49 dBm - (-57 dBm) = 106 dB

  3. dB or not dB Example • If we cascade two amplifiers with power gains of 12 and 16, respectively, • The total gain is 12 times 16 = 192 (which you can hopefully calculate in your head easily – can you?). • In logarithmic terms, the two amplifiers have gains of 10.8 dB and 12 dB, respectively, producing a total gain of 22.8 dB, which is definitely easier to calculate.

  4. ｄB or not dB dB

  5. ｄB or not dB dBm Examples: The output power range of signal generators extends typically from -140 dBm to +20 dBm or 0.01 fW (femto Watt) to 0.1 W. Mobile radio base stations transmit at +43 dBm or 20 W. Mobile phones transmit at +10 dBm to +33 dBm or 10 mW to 2 W. Broadcast transmitters operate at +70 dBm to +90 dBm or 10 kW to 1 MW.

  6. ｄB or not dB dBc • We reference this power to the power of the carrier to produce a result in dBc (1 Hz bandwidth) @ a foffset. • The c in dBc stands for “carrier”.

  7. ｄB or not dB

  8. ｄB or not dB • Importance of speaking properly and therefore employing the right units for any parameter. http://youtube.com/watch?v=_tA0m8OPJB8

More Related