 |
Moteur de recherche de fiches techniques de composants électroniques |
|
|
Moteur de recherche de fiches techniques de composants électroniques |
|
MRF89XA Fiches technique(PDF) 62 Page - Microchip Technology |
|
||||||||||||||||||||||||||||||
MRF89XA Fiches technique(HTML) 62 Page - Microchip Technology |
|
|
62 / 140 page  MRF89XA DS70000622D-page 62 Preliminary 2010-2017 Microchip Technology Inc. 3.4.4 CHANNEL FILTERS The second mixer stages are followed by the channel select filters. The channel select filters have a strong influence on the noise bandwidth and selectivity of the receiver and hence its sensitivity. Each filter comprises a passive and an active section. 3.4.4.1 Passive Filter Each channel select filter features a passive second- order RC filter, with a bandwidth programmable through the PASFILV<3:0> bits (FILCREG<7:4). As it defines a wider bandwidth, its effect on the sensitivity is negligible, but its bandwidth must be set up to optimize blocking immunity. The value entered into this register sets the single side bandwidth of this filter. For optimum performance it should be set to three to four times the cut-off frequency (fc) of the active Butterworth (or Polyphase) filter described in Section 3.4.4.2, Active Filter, and as shown in Equation 3-8. EQUATION 3-8: 3.4.4.2 Active Filter The “fine” channel selection is performed by an active, third-order, Butterworth filter, which acts as a low-pass filter for the zero-IF configuration (FSK), or a complex Polyphase filter for the low-IF (OOK) configuration. The POLFILEN bit (SYNCREG<7>) enables or disables the Polyphase filter. Figure 3-6 illustrates the required bandwidth of this filter that varies between the two demodulation modes. FIGURE 3-6: ACTIVE CHANNEL FILTER DESCRIPTION FSK mode: The 99% energy bandwidth of an FSK modulated signal is approximated, as shown in Equation 3-9. EQUATION 3-9: The BUTFILV<3:0> bits from FILCREG set co, the cut- off frequency (fc) of the filter. In a zero-IF configuration, the FSK lobes are centered on the virtual “DC” frequency. The choice of co should be such that the modulated signal falls in the filter bandwidth, anticipating the Local Oscillator frequency drift over the operating temperature and aging of the device as shown in Equation 3-10. EQUATION 3-10: Figure 3-11 illustrates an accurate overview of the filter bandwidth versus setting. OOK mode: The 99% energy bandwidth of an OOK modulated signal is approximated, as shown in Equation 3-11. EQUATION 3-11: 3fc ButterFilter BWpassive,filter 4fc ButterFilter Low-pass filter for FSK (POLFILEN = 0) Polyphase filter for OOK (POLFILEN = 1) -fc 0 frequency frequency 0 Canceled side of the polyphase filter fc -fc -fc BW99%,fsk 2 fdev BR 2 ------- + = 2fc BW99%,fsk LOdrifts + BW99%,ook 2 tbit ------- 2BR == |
Numéro de pièce similaire - MRF89XA |
|
Description similaire - MRF89XA |
|
|
Lien URL |
| Politique de confidentialité |
| ALLDATASHEET.FR |
| ALLDATASHEET vous a-t-il été utile ? [ DONATE ] |
À propos de Alldatasheet | Publicité | Contactez-nous | Politique de confidentialité | Echange de liens | Fabricants All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
French ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
