AN4117 STMICROELECTRONICS | Alldatasheet
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Technical content
Datasheet sections
- 1 Application circuit
- 2 Transmitter parameters
- 2.1 Adjacent channel power
- 2.2 Modulation bandwidth
- 2.3 Unwanted emissions in the spurious domain
- 3 Receiver parameters
- 3.1 Receiver sensitivity
- 3.2 Blocking
- 3.3 Receiver spurious radiation
- 4 Measurement equipment
- 5 Reference
- 6 Revision history
October 2012 Doc ID 023222 Rev 1 1/22 AN4117 Application note Using the SPIRIT1 transceiver under EN 300 220 at 434 MHz By Placido De Vita Introduction The SPIRIT1 is a very low power RF transceiver, intended for RF wireless applications in the sub-1 GHz band. It is designed to operate in both licence-free ISM and SRD frequency bands at 169, 315, 433, 868 and 915 MHz. This application note outlines the expected performance when using the SPIRIT1 under EN requirements in this band, no specific use and no channel spacing are defined. Devices supporting audio and video applications use a digital modulation method with a maximum bandwidth of 300 kHz. Devices supporting digital voice have a maximum bandwidth not exceeding 25 kHz. The maximum allowed output power is +10 dBm (10 mW). For details of the regulatory limits in the 433.050 - 434.790 MHz SRD frequency bands, please refer to the ETSI EN 300 220-1 v2.3.1 [2] and ERC recommendation 70-03 [3].
1 Application circuit
functionality and the ETSI standard request. amplifier (PA) and a balun network for the receiver. Figure 1. SPIRIT1 application daughterboard
Figure 2. SPIRIT1 application daughterboard plugged into the motherboard
Figure 3. Daughterboard schematic
AN4117 Transmitter parameters Doc ID 023222 Rev 1 7/22
2 Transmitter parameters
All the measurements here reported are performed with the following parameters: Tc = 25 °C, Vdd = 3.0 V, f = 434.030 MHz. They are also measured with the reference design reported in EN 300 220 v1 [2] Annex A.1. The modulation bandwidth, adjacent channel power, and unwanted emissions in the spurious domain measurements are here reported. The measurements are realized according to EN 300 220 v1 [2] sections 7.6, 7.7 and 7.8.
2.1 Adjacent channel power
The adjacent channel power (ACP) is defined as the amount of the modulated RF signal power which falls within a given adjacent channel. This power is the sum of the mean power produced by the modulation, hum and noise of the transmitter. This measurement is applicable only to narrowband systems. This test measures the power transmitted in the adjacent channel during continuous modulation. The ACP is measured with a spectrum analyzer which conforms to the requirements given in EN 300 220-1 v2.3.1 (2010-02) [2] Annex C. In this application note, ACP measured with 12.5 kHz and 25 kHz channel spacing are investigated. For these measurements the integrated bandwidths of the adjacent channel are 8.5 kHz and 16 kHz respectively. The ETSI limit for the ACP is 10 µW (-20 dBm) for 12.5 kHz channelization and 200 nW (-37 dBm) for 25 kHz channelization. Figure 4 and 5 illustrate the measured ACP at the 434.3 MHz center frequency with 12.5 kHz channelization, Figure 6 illustrates the measured ACP with 25 kHz channelization. The data rate for the modulated signal in Figure 4 is set to 1.2 Kbps, the frequency deviation is set to 1 kHz, and the modulation is set to 2-FSK. The data rate for the modulated signal in Figure 5 is set to 2.4 Kbps, the frequency deviation is set to 2.4 kHz, and the modulation is set to Gaussian FSK (GFSK) with BT = 0.5. The data rate for the modulated signal in Figure 6 is set to 4.8 Kbps, the frequency deviation is set to 2.4 kHz, and the modulation is set to Gaussian FSK (GFSK) with BT = 0.5. The output power integrated around the carrier is 12 dBm in the bandwidth and with average detection. With this power the ACP is -38 dBm in the first two cases and -43 dBm in the third case. The SPIRIT1 is fully compliant with the ETSI transmitter adjacent channel power requirements with margin.
Figure 4. Adjacent power measurement, 12.5 kHz narrowband channel spacing,
1.2 Kbps data rate, 1 kHz frequency deviation, 2-FSK modulation
Figure 5. Adjacent power measurement, 12.5 kHz narrowband channel spacing,
Figure 6. Adjacent power measurement, 25 kHz narrowband channel spacing,
2.2 Modulation bandwidth
appropriate emissions level and the frequency error or drift under extreme test conditions. is not included in this report. integration at the different offset regions. output power is set to 11 dBm. With these parameters, the spectral masks of SPIRIT1 comply with ETSI [2] subclause 7.7.
Figure 7. ETSI spectral mask measurement limits and sub-band edges Note: f c is the emission center frequency. fe is the sub-band edge frequency. Only the upper half of the emission is shown. The lower half is a mirror image. Figure 8. Spectral mask measurement, 12.5 kHz narrowband channel spacing,
Figure 11. Spectral mask measurement, 100 kHz channel spacing, 38.4 Kbps data Figure 12. Spectral mask measurement, 500 kHz channel spacing, 250 Kbps data
2.3 Unwanted emissions in the spurious domain
described in ETSI [2] subclause 7.8.
Receiver parameters AN4117 14/22 Doc ID 023222 Rev 1
3 Receiver parameters
All the measurements here reported are performed with the following parameters: Tc = 25 °C, Vdd = 3.0 V, f = 434.300 MHz. The product family of short range radio devices is divided into three receiver categories, each having a set of relevant receiver requirements and minimum performance criteria. The set of receiver requirements depends on the choice of receiver category by the equipment provider. The SPIRIT1 is a transceiver that meets receiver category 2. According to EN 300 220-1 (v2.3.1, 2012-02) [2], a category 2 receiver is described as “Medium reliable SRD communication media, e.g. causing inconvenience to persons, which cannot simply be overcome by other means”. The main parameters that must be measured for category 2 devices are the sensitivity, the blocking, and the receiver spurious radiation. The adjacent channel selectivity is referred to receiver category 1, so it is not necessary for SPIRIT1 to meet this parameter.
3.1 Receiver sensitivity
The receiver sensitivity is the minimum level of the signal at the receiver input produced by a carrier at the nominal frequency of the receiver, modulated with the normal test signal modulation, which produces the performance of a bit error rate (BER) of 10 -2 without correction. Under normal test conditions, the value of the typical usable sensitivity for 25 kHz channel spacing equipment with a 16 kHz bandwidth should not exceed -107 dBm. If the RX bandwidth is not 16 kHz, the sensitivity limit is modified according to the following formula: Equation 1 The measurement is performed using an RF signal source generator centered at the same receiver frequency with the wanted modulation signal. The demodulated data and clock are taken from the SPIRIT1 receiver and sent to the same generator to perform the BER measurement. The generator signal level is reduced and a BER of 1% is obtained. To reduce the power consumption, an internal SMPS is integrated into the SPIRIT1. Figure 15 demonstrates the ETSI 1% BER sensitivity limit (red line) and the SPIRIT1 sensitivity for different data rates with SMPS. This application note outlines the expected performance when using the SPIRIT1 under EN 300 220-1 (v2.3.1, 2012-02) [2] at 434.3 MHz, without defining the maximum channel spacing. To show the real performance of the SPIRIT1 transceiver, different channel spacings are shown. The test conditions are:
- 2-FSK modulation, 1.2 kHz data rate, 1 kHz frequency deviation, 12.5 kHz channel spacing
- GFSK modulation with BT = 0.5, 2.4 kHz data rate, 2.4 kHz frequency deviation, 12.5 kHz channel spacing
- GFSK modulation with BT = 0.5, 4.8 kHz data rate, 2.4 kHz frequency deviation, 25 kHz channel spacing
- GFSK modulation with BT = 1, 38.4 kHz data rate, 20 kHz frequency deviation, 100 kHz channel spacing
- GFSK modulation with BT = 1, 250 kHz data rate, 127 kHz frequency deviation, 500 kHz channel spacing. The SPIRIT1 is fully compliant with the ETSI category 2 receiver sensitivity requirements with large margin.
Figure 15. Sensitivity vs. data rate with 1% BER
3.2 Blocking
degradation of 1% is obtained. respectively, 12.5 kHz, 25 kHz, 100 kHz, and 500 kHz channel bandwidth.
Figure 18. RX blocking vs. CW interferer offset with 1% BER, 100 kHz channel Figure 19. RX blocking vs. CW interferer offset with 1% BER, 500 kHz channel
3.3 Receiver spurious radiation
as described in ETSI [2] subclause 8.6.
4 Measurement equipment
The following equipment was used for the measurements. Table 1. Measurement equipment
5 Reference
- SPIRIT1 datasheet. 2. ETSI EN300 220 V2.3.1: “Electromagnetic compatibility and Radio spectrum Matters (ERM); Short Range Devices (SRD); Radio equipment to be used in the 25 MHz to 1000 MHz frequency range with power levels ranging up to 500 mW”. 3. CEPT/ERC/Recommendation 70-03: “Relating to the use of Short Range Devices (SRD)”. 4. CEN/TC prEN 13757-4:2011.10: “Communication systems for meters and remote reading of meters - Part 4: Wireless meter readout (radio meter reading for operating in SRD bands)”.
6 Revision history
Table 2. Document revision history 01-Oct-2012 1 Initial release.