STM32W108B-SK STMicroelectronics, STM32W108B-SK Datasheet - Page 2

• Manufacturer Part Number: STM32W108B-SK
• Description: STARTER KIT FOR STM32W108
• Manufacturer: STMicroelectronics
• Series: STM32r
• Type: MCUr

Specifications of STM32W108B-SK

• Featured Product: STM32 Cortex-M3 Companion Products
• Contents: Board
• Silicon Manufacturer: ST Micro
• Core Architecture: ARM
• Core Sub-architecture: Cortex - M3
• Silicon Core Number: STM32
• Silicon Family Name: STM32W108xx
• Kit Contents: Board
• Features: IEEE
• Mfg Application Notes: STM32W108 Adjacent Channel Rejection Measurements
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: *
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Interferer waveforms
3
2/6
Table 1.
Most 802.15.4 ICs exceed the standard's requirements by a long way.
The standard does not specify the filtering of the interferer signal, it only states that it should
be 802.15.4 compliant, which means it must meet the spectral mask and error vector
magnitude (EVM) specifications.
Interferer waveforms
For the ACR figures quoted in datasheets, the interferer signal is generated by using the
arbitrary waveform generator mode of a signal generator, and constructing a near ideal
802.15.4 O-QPSK waveform containing pseudo-random symbols.
Other manufacturers use a heavily filtered IEEE 802.15.4-2003 signal to measure ACR.
This has the result of removing all energy from the interferer's sidelobes that would fall in-
band. This method creates such a signal by filtering the ideal signal prior to loading into a
signal generator. The filter uses a 100 tap FIR with cutoff frequency at 3.5 MHz so that the
2nd (3 MHz) sidelobe is not attenuated, but the 3rd one (4 MHz) is almost completely
removed. While this signal is IEEE 802.15.4-2003 compliant (it meets the EVM specified in
the standard), it is not representative of any real implementation since this degree of filtering
is not practical in real silicon.
Figure 1
generators and 802.15.4 silicon.
Using an ideal signal source, ACR performance is ultimately limited by energy from an
interfering signal that falls into the wanted channel bandwidth.
offset, the ideal and real silicon spectra are 42 dB below the wanted signal level in a
100 kHz bandwidth. A good receiver will have a 1.1 MHz bandwidth, and the integrated
power in this bandwidth is –38 dBc at 5 MHz (1.1 MHz is the bandwidth of the matched filter
for optimum signal reception, different receivers may have wider bandwidths than this).
Therefore, if a receiver has an SNR requirement of 3 dB, then it cannot achieve an ACR of
better than 35 dB. Any datasheet that quotes more than 35 dB for ACR is not using an ideal
or even a representative 802.15.4 interferer signal. While some chips may be capable of
higher rejection of the main signal lobe at 5 MHz, this is of little value since the in-band
sidelobe level limits real system performance.
At 10 MHz, the receiver cannot achieve a rejection of better than 48 dB for an ideal 15.4
signal.
The adjacent channel rejection shall be measured as follows. The desired signal shall
be a compliant 2450MHz IEEE 802.15.4 signal of pseudo-random data. The desired
signal is input to the receiver at a level 3 dB above the maximum allowed receiver
sensitivity given in 6.5.3.3. In either the adjacent or the alternate channel, an IEEE
802.15.4 signal is input at the relative level specified in Table 22. The test shall be
performed for only one interfering signal at a time. The receiver shall meet the error rate
criteria defined in 6.1.6 under these conditions.
and
Adjacent channel rejection
Minimum receiver jamming resistance requirements for 2450 MHz PHY
Figure 2
0 dB
show a comparison of 802.15.4 spectra produced by signal
Doc ID 17543 Rev 2
Alternate channel rejection
Figure 2
30 dB
shows that at 5 MHz
AN3218