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20 ohm resistor color code

来源:LM317 Electronics Components编辑:Advanced Thermal Solutions, Inc.时间:2021-06-15 15:00:46

PAs in the field today are predominately linearized by some form of feed-forward technology, a conceptoriginally proposed by Black during the 1930s.1 In recent years, however, designers have started to veer away from traditional feed-forward approaches toward linearization techniques that employ digital predistortion. Compared to feed-forward architectures, designs based on digital predistortionapproaches are showing higher efficiency at lower cost and, with recent advances in technology, digital predistortion can now support signal bandwidths in excess of 20 MHz.

The results of the RF modelling technique are very encouraging, as even at this stage of the study the performance is excellent.

Philips continues the search for better models and in particular, the equaliser. RF analysis allows best choice for optical networks to be made.

20 ohm resistor color code

With these results, Philips 12.5Gbit/s asynchronous optical cross point switch and Teradyne GbX connectors and backplane will help bring protocols like 10Gigabit Ethernet, SONET and SDH into metro and wide area networks.

Valerie Prevel is from Philips Semiconductors, Business Line Networking Infrastructure,in Caen, France. Special thanks are due to Carle Lengoumbi, co-author, who helped tremendously during her 3 months internship at Philips.

20 ohm resistor color code

Power amplifiers (PA) are one of the most expensive and most power-consuming components in 3G base station architectures. They are inherently nonlinear, and when operated near saturation, cause intermodulation products that interfere with adjacent and alternate channels. This interference affects the adjacent channel leakage ratio (ACLR) and its level is strictly limited by FCC and ETSI regulations.

Fortunately, there are linearization techniques that allow PAs to operate efficiently and at the same time maintain acceptable ACLR levels. In effect, linearization affords the use of a lower-cost more-efficient PA in place of a higher-cost less-efficient PA.

20 ohm resistor color code

PAs in the field today are predominately linearized by some form of feed-forward technology, a conceptoriginally proposed by Black during the 1930s.1 In recent years, however, designers have started to veer away from traditional feed-forward approaches toward linearization techniques that employ digital predistortion. Compared to feed-forward architectures, designs based on digital predistortionapproaches are showing higher efficiency at lower cost and, with recent advances in technology, digital predistortion can now support signal bandwidths in excess of 20 MHz.

In this paper, we use digital predistortion to linearize a laboratory PA. The transmit waveform is four carriers of UMTS comprising a 20 MHz signal bandwidth. An adaptive algorithm is used with a closed-loop hardware architecture to improve ACLR by 15 dB, meeting the 3GPP specification with 12% efficiency. It is also shown that the PA phase nonlinearity is a large contributor to ACLR and cannot be neglected.

Philips Semiconductors was able to make relevant decisions thanks to extensive RF analysis and its experience in the RF application domain. For example, time domain reflectometry (TDR) and S-parameter measurement show that PCB choice affects the jitter measurement and eye pattern form. The TDR response gives information about the impedance of the system; while S-parameter measurement describes its RF behaviour. With S-parameters, reflections versus frequency (S11) and losses versus frequency (S21) can be taken into account. Such a study lead to a choice of material used in the Teradyne backplane. Indeed, the loss chart shows the limit of FR4 after 6GHz. The same study on Rogers material indicates it is better than FR4 in the frequency band. This conclusion is illustrated by the two eye diagram at 10GHz, one from an application with a Rogers backplane &endash; see figure 3 &endash; and the other from an FR4 application &endash; figure 2.

Fig 2: Eye diagram at 10GHz using FR4

Fig 3: Eye diagram at 10GHz using a Rogers backplane

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