**2.2.2 Platform noise analysis of Netbook system[6]**

Platform noise analysis can be conducted through the noise floor measurement at antenna port of wireless device. The complete setup for noise floor measurement should at least consist of following hardware instruments: Shielded box, pre-amplifier, spectrum analyser or EMI receiver, high quality coaxial cable, and Netbook EUT.

The frequency-domain noise floor measurement setup for Netbook platform is shown as Figure 11(a). The measuring procedure is as following: Put the EUT Netbook inside the shielded box and connect its antenna port to the pre-amplifier and spectrum analyser. We first measured the ambient noise with Netbook power-off, then powered on the Netbook and measured the noise level within the selected communications bands as interfering platform noise.

Figure 13 shows the noise level captured by the integral WWAN antenna of the Netbook on GSM 850, GSM 900, and DCS 1800 bands. The platform noises on GSM 850, GSM 900, and DCS 1800 bands are shown in Figure 2(a), (b), and (c) respectively. Figure 13(a) shows that the major noise spectrum falls on 864 MHz and 888 MHz, corresponding to the 36th and 37th harmonics of the Azalia Sound Card with 24 MHz fundamental driver frequency.

Fig. 13. Measured noise level on WWAN bands of Netbook.

Platform noise analysis can be conducted through the noise floor measurement at antenna port of wireless device. The complete setup for noise floor measurement should at least consist of following hardware instruments: Shielded box, pre-amplifier, spectrum analyser

The frequency-domain noise floor measurement setup for Netbook platform is shown as Figure 11(a). The measuring procedure is as following: Put the EUT Netbook inside the shielded box and connect its antenna port to the pre-amplifier and spectrum analyser. We first measured the ambient noise with Netbook power-off, then powered on the Netbook and measured the noise level within the selected communications bands as interfering

Figure 13 shows the noise level captured by the integral WWAN antenna of the Netbook on GSM 850, GSM 900, and DCS 1800 bands. The platform noises on GSM 850, GSM 900, and DCS 1800 bands are shown in Figure 2(a), (b), and (c) respectively. Figure 13(a) shows that the major noise spectrum falls on 864 MHz and 888 MHz, corresponding to the 36th and 37th harmonics of the Azalia Sound Card with 24 MHz fundamental driver frequency.

(a) GSM850 (b) GSM900

(c) DCS1800

Fig. 13. Measured noise level on WWAN bands of Netbook.

**2.2.2 Platform noise analysis of Netbook system[6]** 

platform noise.

or EMI receiver, high quality coaxial cable, and Netbook EUT.

Figure 13(b) shows broadband and regularity characteristics of noise on 900 MHz band. Since the fundamental frequency of the LVDS interconnection cable is 50 MHz and noise spectrum falls between 900 MHz and 950 MHz, we can calculate from system clock map that the noise spectrum received by antenna was originated from 18th and 19th harmonics of LVDS cable. Figure 13(c) shows that the noise measured on DCS 1800 band falls on 1824 MHz, which is 38th harmonic of CCD camera. Figure 13(c) also shows noise occurring around 1850 MHz and 1900 MHz, which are the 38th and 39th harmonics of LVDS cable respectively. From the noise spectrum analysis, we found out that the noise sources mentioned above cause in-band interference on operation bands of GSM 850/950 and DCS 1800 systems frequently. Figure 14(a) shows the noise measurement result on Band-1 of WCDMA, and it appears as lower level and ambiguous. However, because Band 5of WCDMA almost operate on the same frequencies with GSM 850, it thus suffers interference from the 36th and 37th harmonics of the Azalia Sound Card.

From the platform noise measurement method and clock map analysis, we are able to establish the system design rule for related position and orientation of noise source(s) and antenna(s) placement to suppress in-band interference. We can also utilize various isolation or shielding techniques to effectively prevent the antenna port noise level from platform noise sources, and further reduce the delay time caused by lengthy product debug and speed up testing time.

Fig. 14. Measured noise level on WCDMA bands of Netbook.

#### **2.2.3 Impact analysis of platform noise on TIS of GSM/WCDMA systems[6]**

TIS is a figure of merit for receiving performance of a mobile or wireless terminal device. Receiver performance is considered as important to over all system performance as is Transmitter performance. The downlink, or subscriber unit receive path is integral to the quality of the device's operation. The receiver performance of the Equipment Under Test (EUT) is measured utilizing Bit Error Rate (BER) or Frame Errasure Rate (FER). This test specification uses the appropriate digital error rate (as measured by the subscriber unit) to evaluate effective radiated receiver sensitivity at each spatial measurement location. All of the measured sensitivity values for each EUT test condition will be integrated to give a single figure of merit referred to as Total Isotropic Sensitivity (TIS). The BER specification of CTIA on GSM and WCDMA systems for optimal transmitted data rate are 2.44% and 1.22% respectively. TIS measurement not only measures the performance of stand-alone antenna, but also takes wireless device itself into account to realize the practical implementation. We evaluated the EIS (Effective Isotropic Sensitivity) by measuring the minimum received power that met the BER requirement on the test position. The TIS result is able to clearly show the 3-dimensional receiving performance of wireless communications device under specific mobile communications environment.

The complete setup for TIS measurement should at least consist of following hardware instruments: fully anechoic chamber, measuring antenna(s), base-station communications emulator, RF relay switch, high quality coaxial cable, control PC, and position controller. The practical setup for TIS measurement is shown as Figure 4. The operation principle of Figure 15 is as following: Connect control PC to the base-station communications emulator and then make the base-station emulator send test signal to transmit antenna. The power level of transmit antenna is set to -60 dBm for TIS measurement. The power level decreasing step specified by CTIA is 0.5 dB for transmit antenna to measure the minimum power level obtained by receiving antenna. When the transmitted power has been attenuated to some lower level and signal received from receiving antenna to basestation emulator with BER worse than 2.44% (GSM)/1.22% (WCDMA), then we have the minimum receiving power for Netbook.

Fig. 15. Setup for TIS measurement.

TIS is a figure of merit for receiving performance of a mobile or wireless terminal device. Receiver performance is considered as important to over all system performance as is Transmitter performance. The downlink, or subscriber unit receive path is integral to the quality of the device's operation. The receiver performance of the Equipment Under Test (EUT) is measured utilizing Bit Error Rate (BER) or Frame Errasure Rate (FER). This test specification uses the appropriate digital error rate (as measured by the subscriber unit) to evaluate effective radiated receiver sensitivity at each spatial measurement location. All of the measured sensitivity values for each EUT test condition will be integrated to give a single figure of merit referred to as Total Isotropic Sensitivity (TIS). The BER specification of CTIA on GSM and WCDMA systems for optimal transmitted data rate are 2.44% and 1.22% respectively. TIS measurement not only measures the performance of stand-alone antenna, but also takes wireless device itself into account to realize the practical implementation. We evaluated the EIS (Effective Isotropic Sensitivity) by measuring the minimum received power that met the BER requirement on the test position. The TIS result is able to clearly show the 3-dimensional receiving performance of wireless communications device under

The complete setup for TIS measurement should at least consist of following hardware instruments: fully anechoic chamber, measuring antenna(s), base-station communications emulator, RF relay switch, high quality coaxial cable, control PC, and position controller. The practical setup for TIS measurement is shown as Figure 4. The operation principle of Figure 15 is as following: Connect control PC to the base-station communications emulator and then make the base-station emulator send test signal to transmit antenna. The power level of transmit antenna is set to -60 dBm for TIS measurement. The power level decreasing step specified by CTIA is 0.5 dB for transmit antenna to measure the minimum power level obtained by receiving antenna. When the transmitted power has been attenuated to some lower level and signal received from receiving antenna to basestation emulator with BER worse than 2.44% (GSM)/1.22% (WCDMA), then we have the

**2.2.3 Impact analysis of platform noise on TIS of GSM/WCDMA systems[6]** 

specific mobile communications environment.

minimum receiving power for Netbook.

Fig. 15. Setup for TIS measurement.

The results of TIS measurement are shown in Table 1 and 2. The High/Mid/Low channels of GSM850/900 and DCS1800 systems are selected to analyse the platform noise level impact on TIS measurement as shown in Table 1. We found that TIS performance is getting worse as in-band noise increases. Table 1(c) shows the relationship between platform noise level and TIS on CH 512 and CH 698 of DCS 1800 system, it indicates that TIS has 5dB degradation as platform noise increases 2 dB. Table 2 shows the TIS measurement result of WCDMA of Netbook. From the platform noise level and TIS comparison between CH 4357 and CH 4408 of WCDMA Band-5, we found that TIS has 2dB degradation as platform noise increases 1.5 dB. From the observation above, we briefly conclude that TIS performance of the wireless product degrades 2 dB whenever intra-system platform noise level increases 1 dB. It therefore shows that the platform noise is the major factor affecting the receiving sensitivity of wireless devices.


Table 1. Measured TIS on WWAN bands of Netbook (a) GSM850 (b)GSM900(c)DCS1800.


(b) WCDMA Band5

Table 2. Measured TIS on WCDMA bands of Netbook.
