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Silicon Laboratories Si435 Series Скачать руководство пользователя страница 14

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5. PCB Antennas for Si4455/Si435x RF ICs

This document shows the PCB antenna layouts that are used in Si4455/435x applications. More information about
these antennas and descriptions of their operation can be found in the application note, “AN686: Antennas for the
Si4455/435x RF ICs”.

The Si4455 transceiver and Si435x receiver RF chips use the same PCB antennas, and the parameters for these
antennas depend on the operating frequency. Because the antennas are reciprocal and linear, the same antenna
can be used for transmitting and receiving. In all cases, the applied antennas are matched/tuned to have 50

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input impedance, thus a matching network is required for use between the RF IC and the antenna.

A typical single-ended IFA antenna applied in the Si4355-PRXB315B (Si4355CPRXB315B) development board is
shown in Figure 14. Here the tuning arm of the antenna uses two layer curls to reduce the area occupied by the
antenna.

Figure 14. Single-ended IFA used in the Si4355-PRXB315B (Si4355CPRXB315B) Development

Board

A typical BIFA (balanced IFA) antenna applied in the Si4455-LED-434 (Si4455CLED-434) development board is
shown Figure 15. Here also the tuning arm of the antenna uses two layer curls to reduce the area occupied by the
antenna.

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Содержание Si435 Series

Страница 1: ...nsiderations in the layout design For optimal performance Silicon Labs recommends using the PCB layout design suggestions described in the following sections 2 Design Recommendations when Using Si4455 435x RF ICs Extensive testing has been completed using reference designs provided by Silicon Labs It is recommended that designers use the reference designs as is since they minimize de tuning effect...

Страница 2: ...he matching network to the GND is not blocked through the RX side therefore a dc blocking capacitor CC1 is necessary For the Direct Tie type matching the coupling between the RX and TX sides is not critical since no harmonic leakage through the coupled RX path occurs as both of them are filtered after the common connection point Beside the TX output unwanted harmonics appear on other pins due to c...

Страница 3: ...parasitic inductance between the ground pour and the GND pins Avoid using long and or thin transmission lines for connecting the components or else due to its distributed parasitic inductance some de tuning effects can occur Avoid placing the nearby inductors in the same orientation to reduce the coupling between them Use tapered line between transmission lines with different width i e different i...

Страница 4: ...connecting CM1 to the GND metal at the other side of the matching network the suppression of the double frequency harmonic could increase even by 5 dB by reducing the coupling between stages of the low pass filter If space allows the parallel inductor in the RX path LR1 should be perpendicular to the nearby inductors in the TX path as this will reduce TX to RX coupling Increase the grounding effec...

Страница 5: ...nnected to the top layer GND metal if possible to further improve RF grounding this may be accomplished with diagonal trace connections through the corners of the RFIC footprint The crystal should be placed as close to the RFIC as possible to ensure wire parasitic capacitances are kept as low as possible this will reduce any frequency offsets that may occur Use at least 0 5 mm separation between t...

Страница 6: ...ting and wiring should not be placed in this region to prevent coupling effects with the matching network It is also recommended that the GND return path between the GND vias of the TX LPF Match and the GND vias of the RFIC paddle should not be blocked in any way the return currents should see a clear unhindered pathway through the GND plane to the back of the RFIC Use 50 grounded coplanar lines w...

Страница 7: ...RF part of the Si4455 LED 434 Si4455CLED 434 pico board PCB The top and bottom layers are shown respectively Examples for the 50 grounded coplanar trace dimensions are shown in Table 1 Figure 5 Ground Poured Sections with PCB Vias around the Matching Network Top Layer Figure 6 Ground Poured Sections with PCB Vias Bottom Layer ...

Страница 8: ...eters Table 1 Parameters for 50 Grounded Coplanar Lines f 119 960 MHz T 0 018 0 035 mm Er 4 6 H 1 5 mm 0 26 m G 0 25 mm 0 64 mm W 1 26 mm 0 45 mm Note For the 4 layer PCBs the thickness between the top and the next inner layer should be taken into account ...

Страница 9: ...MCU sections are connected well as possible to each other Figure 8 and Figure 9 show this solution for the Si4455 LED 434 Si4455CLED 434 development board The top and bottom layers are shown respectively As shown in Figure 8 and Figure 9 there are as many connection wires as possible between the two parts to minimize the parasitic inductance in the grounding between the two stages Figure 8 Ground ...

Страница 10: ...a or the SMA connector with a 50 SMA antenna by soldering a 0805 size of 0 resistor to the proper side see the SMA PCB ANT selecting 0805 0 in Figure 10 On these boards the only route where 50 coplanar transmission line is used is between one of the 0805 resistors and the SMA connector since the output of the matching network is very close to the 0805 resistors Figure 10 demonstrates the layout st...

Страница 11: ... the LNA input to a 50 source impedance i e the antenna In addition the LR2 CR2 are parallel resonant at the desired operating frequency This resonance is an important factor in TRX Direct Tie matching because it enables the RF IC to work in TX mode without any output power degradation when the RX side shows very high impedance The matching component values should be chosen based on the operating ...

Страница 12: ... tuning effects in the matching network Since the Si435x LED xxx Si435xCLED xxx development boards have the same PCB structure as the Si4455 LED xxx Si4455CLED xxx development boards the distance between the RF IC and the SMA connector and the antenna is the same In addition a 50 grounded coplanar transmission line is necessary between the SMA PCB ANT selecting 0805 0 and the matching network to a...

Страница 13: ...AN685 Rev 0 4 13 Figure 13 Layout of the RF Part of the Si4355 LED 434 Si4355CLED 434 Development Board ...

Страница 14: ...d for transmitting and receiving In all cases the applied antennas are matched tuned to have 50 input impedance thus a matching network is required for use between the RF IC and the antenna A typical single ended IFA antenna applied in the Si4355 PRXB315B Si4355CPRXB315B development board is shown in Figure 14 Here the tuning arm of the antenna uses two layer curls to reduce the area occupied by t...

Страница 15: ...ired The printed balun drives a differential BIFA and the impedance match is done by a differential strip line Furthermore it is necessary to keep at least 2 mm space between the entire antenna and the border of the PCB to ensure a reliable antenna input impedance and radiating characteristic Silicon Labs has tested the use of this type of BIFA antenna to ensure its performance For example the inp...

Страница 16: ...s Si4455 LED 868 Si4455CLED 868 development boards was also under investigation with the follow parameters Delivered power to the antenna is approximately 12 dBm Radiated power is approximately 5 dBm in EIRP antenna gain is around 7 dB Data rate 2 4 kbps 2 level FSK modulation deviation 30 kHz The measured range is larger than 1 km the result is shown in Figure 17 Figure 17 Range at 868 MHz 1125 m...

Страница 17: ...ermination for the PA of the RF IC and the differential to single ended conversion since the Si4012 RF IC has a differential PA output As shown in Figure 18 the parallel inductor between the PA output differential pins is separated by two parts LM2 and LM4 which should have the same value so that the 2nd harmonic can be effectively suppressed with a shunt capacitor CM3 The matching principles are ...

Страница 18: ... effects in the matching network The length of the leading traces for the two separated inductors LM2 LM4 should be equal to each other The choke inductor LM1 and the capacitor for suppressing the 2nd harmonic CM3 should be placed to the bottom layer and connected into the common symmetric point of the separated inductors 6 2 PCB Antennas for the Si4012 RF IC The Si4012 RF IC can use the same PCB ...

Страница 19: ...19 APPENDIX This section includes references for all the PCB layouts that use the Si4355 or Si4455 RF IC Figure 20 4455 PCExxDxxxM 4455CPCExxDxxxM Pico Board Figure 21 Si4355 LED 434 Si4355CLED 434 Development Board ...

Страница 20: ...AN685 20 Rev 0 4 Figure 22 Si4355 LED 868 Si4355CLED 868 Si4355 LED 915 Si4355CLED 915 Development Board Figure 23 Si4355 PRXB434B 4355CPRXB434B Development Board ...

Страница 21: ...AN685 Rev 0 4 21 DOCUMENT CHANGE LIST Revision 0 3 to Revision 0 4 4455Cyyy in brackets added to 4455 yyy 4355Cyyy in brackets added to 4355 yyy 4012Cyyy in brackets added to 4012 yyy ...

Страница 22: ...lth which if it fails can be reasonably expected to result in significant personal injury or death Silicon Laboratories products are generally not intended for military applications Silicon Laboratories products shall under no circumstances be used in weapons of mass destruction including but not limited to nuclear biological or chemical weapons or missiles capable of delivering such weapons Trade...

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