4.1.5 Receiver Blocking and Selectivity Characteristics

This section describes the blocking behavior of the ATA8510/15. The numbers listed are the 3-dB blocking characteristics. The measurements below are carried out with a useful signal at a frequency of fRF and a level of 3 dB above the BER = 10-3 sensitivity levels, as shown in parameter nos. 4.90 to 5.20 in RF Receiving Characteristics. The values indicated describe how much a continuous wave disturber can be larger than these useful signal levels until the BER drops back to 10-3. For example, the sensitivity level is -106.5 dBm (see parameter no. 5.10 in RF Receiving Characteristics) and at a distance of 1 MHz the blocking is 64 dBC (see parameter no. 7.10 in RF Receiving Characteristics or the following figure). The useful signal applied in the measurement is -106.5 dBm + 3 dB = -103.5 dBm and the measured absolute blocker level for BER 10-3 is -103.5 dBm + 64 dBC = -39.5 dBm.

The following figures, Figure 4-10 and Figure 4-11, show the blocking behavior for 433.92 MHz with 165 kHz bandwidth using FSK modulation with a data rate of DR = 20 kBit/s and a frequency deviation of fDEV = ±20 KHZ. All measurements are with high resolution to capture all spurious receiving frequencies.

Figure 4-9. Measured Blocking at ±1 MHz Frequency Offset (fRF = 433.92 MHz, BW = 165 kHz, FSK, DR = 20 kBit/s, fDEV = ±20 kHz)
Figure 4-10. Measured Blocking at ±10 MHz Frequency Offset (fRF = 433.92 MHz, BW = 165 kHz, FSK, DR = 20 kBit/s, fDEV = ±20 kHz)
Figure 4-11. Measured Blocking in the Frequency Range from 100 MHz to 900 MHz (fRF = 433.92 MHz, BW = 165 kHz, FSK, DR = 20 kBit/s, fDEV = ±20 kHz)

The differences in the blocking characteristics for other RF frequencies or bandwidths are shown in parameter nos. 6.90 to 7.80 in RF Receiving Characteristics. To describe the differences more clearly, the blocking for 25 kHz IF bandwidth and 360 kHz IF bandwidth is depicted in the following figure.

Figure 4-12. Measured Blocking at ±1 MHz Frequency Offset (fRF = 433.92 MHz, BW = 25 kHz, FSK, DR = 2.4 kBit/s, fDEV = ±2.4 kHz)

To describe the differences more clearly, the blocking for 25 kHz IF bandwidth and 360 kHz IF bandwidth is depicted in the following figure.

Figure 4-13. Measured Blocking at ±1 MHz Frequency Offset (fRF = 433.92 MHz, BW = 366 kHz, FSK, DR = 20 kBit/s, fDEV = ±20 kHz)