SWRA730 February   2022 CC1311P3 , CC1311R3 , CC1312R , CC1312R7 , CC1314R10 , CC1352P , CC1352P7 , CC1352R , CC1354P10 , CC1354R10

 

  1.   Trademarks
  2.   Acronyms
  3. 1Description of the PCB Antenna
    1. 1.1 Implementation of the PCB Meander Monopole Antenna
    2. 1.2 Matching Network
  4. 2Test Setup
    1. 2.1 Radiation Pattern
  5. 3Unmatched Results
    1. 3.1 Smith Chart – Natural Impedance without Antenna Match Components
    2. 3.2 Smith Chart – Impedance with external component Z64
      1. 3.2.1 433 MHz Unmatched
      2. 3.2.2 470 MHz Unmatched
      3. 3.2.3 490 MHz Unmatched
      4. 3.2.4 510 MHz Unmatched
      5. 3.2.5 868/915 MHz Unmatched
  6. 4Single-Band Matching and Result
    1. 4.1 433-MHz Smith chart, SWR, Bandwidth, and Efficiency
    2. 4.2 470-MHz Smith chart, SWR, Bandwidth, and Efficiency
    3. 4.3 490-MHz Smith Chart, SWR, Bandwidth, and Efficiency
    4. 4.4 510-MHz Smith Chart, SWR, Bandwidth, and Efficiency
    5. 4.5 868/915-MHz Smith Chart, SWR, Bandwidth, and Efficiency
  7. 5Dual Band Matching and Results
    1. 5.1 433-MHz and 2440-MHz Smith Chart, SWR, Bandwidth, and Efficiency
    2. 5.2 470-MHz and 2440-MHz Smith Chart, SWR, Bandwidth and Efficiency
    3. 5.3 490 MHz and 2440 MHz Smith Chart, SWR, Bandwidth and Efficiency
    4. 5.4 510-MHz and 2440-MHz Smith Chart, SWR, Bandwidth, and Efficiency
    5. 5.5 868/915 and 2440-MHz Smith Chart, SWR, Bandwidth, and Efficiency
  8. 6Summary - Bill of Materials and Results
  9. 7Conclusion
  10. 8References

4.5 868/915-MHz Smith Chart, SWR, Bandwidth, and Efficiency

As mentioned earlier in Section 3.2.5 the bandwidth of the antenna is sufficient to achieve a good match for 868 MHz and 915 MHz simultaneously. Hence we only need one matching network for both frequencies, and therefore tune the antenna for ( (915+896) / 2 ≈ ) 892 MHz.

Figure 4-17 shows the theoretical Smith chart for matching the antenna for single-band 892 MHz with a theoretical SWR of 1.065.

GUID-20211124-SS0I-50NC-KCTM-8LMNFZ5VH1FD-low.pngFigure 4-17 Theoretical Smith Chart for Single-Band 892-MHz Matching

Further tuning of the resonance of the antenna was needed after realizing the theoretical match. Figure 4-18 and Figure 4-19 shows the resulting impedance and SWR which at 1.225 is less than the threshold for a good match of SWR < 2.0. Table 4-5 shows the BOM with components used to relies the matching network given in Figure 1-2.

The bandwidth of the antenna defined by SWR < 2.0 can be seen in Figure 4-19 to be 941.16-845.8 = 95.81 MHz.

Table 4-5 Matching Network BOM for 892-MHz Single-Band Operations
Ref. DesignatorMurata Part NumberValue
Z600 Ω
Z61

DNM

Z62

DNM

Z630 Ω
Z64GRM0335C1H2R0CA012 pF
Figure 4-18 Smith Chart Measurement of 868, 892, and 915 MHz
Figure 4-19 SWR Measurement of 892-MHz And Bandwidth at SWR < 2

Figure 4-20 and Figure 4-21 shows the radiation pattern of the antenna matched for 892 MHz radiating at 13 dBm 868/915 MHz. Table 4-6 shows the TRP and efficiency for the antenna with the given matching network

Table 4-6 TRP and Efficiency for 868/915 MHz
Figure 38Figure 39
Frequency868 MHz915 MHz
Power setting13 dBm13 dBm
Conducted output power11.89 dBm12.83 dBm
TRP10.51 dBm12.71 dBm
Efficiency72.78 %97.27 %
Figure 4-20 Radiation Pattern of the Antenna Matched for 892-MHz Radiating with 13 dBm 868-MHz Setting
Figure 4-21 Radiation Pattern of the Antenna Matched for 892-MHz Radiating with 13 dBm 868-MHz Setting
Note: If either 868 or 915 MHz is preferred over the other, the antenna can be tuned towards either frequency. This would increase the efficiency and bandwidth of the frequency.