60GHz OFDM NLOS 1 phased arrays Consider a 10m NLOS link at 60GHz which employs OFDM and 16QAM modulation format and transmits at a data rate of 4Gb/s, occupying a bandwidth of 2GHz. (a)Calculate the link margin if the transmitter consists of a phased array with 32 elements, each element

Question

60GHz OFDM NLOS 1 phased arrays

Consider a 10m NLOS link at 60GHz which employs OFDM and 16QAM modulation format and transmits at a data rate of 4Gb/s, occupying a bandwidth of 2GHz.

(a) Calculate the link margin if the transmitter consists of a phased array with 32 elements, each element transmitting with an output power [latex]P_{TXi}[/latex] of 0dBm (10dB back-off from the saturated power, [latex]P_{SAT}[/latex] ), the receiver noise figure and detector SNR are 7dB and 21dB, respectively, and the transmit and receive antennas each have a gain of 6dBi.

(b) Recalculate the link margin when the output power of each transmit element increases from 0dBm to + 5dBm.

Accepted Answer

The free-space loss over 10m is

[latex]L F S=20 imes \log _{10}\left(\frac{\lambda}{4 \pi d} ight)=88 \mathrm{~dB}[/latex] where [latex]\lambda=5 \mathrm{~mm}[/latex] and [latex]\mathrm{d}=10 \mathrm{~m}[/latex]

For arrays, [latex]P_{T X}=P_{T X i}+10 \log _{10}(N), G_{T X}=G_{A i}+10 \log _{10}(N)[/latex],
Hence, [latex]P_{T X}=0 \mathrm{dBm}+10 \log _{10}(32)=15 \mathrm{dBm}, G_{T X}=G_{R X}=6+15=21 \mathrm{~dB}[/latex], and [latex]E I R P[/latex]

[latex](\mathrm{dBmi})=P_{\mathrm{TX}}(\mathrm{dBm})+G_{T X}(\mathrm{dBi})=15 \mathrm{dBm}+21 \mathrm{dBi}=36 \mathrm{dBmi}[/latex]

[latex]P_{R X}=E I R P-L_{F S}+G_{R X}=36-88+6=-46 \mathrm{dBm}[/latex]

The receiver sensitivity is

[latex]S_{i}=-174 \mathrm{dBm}+10 \log _{10}\left(2 imes 10^{9} ight)+7 \mathrm{~dB}+21 \mathrm{~dB}-10 \log _{10}(32)=-68 \mathrm{dBm}[/latex]

That leaves a loss margin of 22dB.

(b) If the power transmitted by each element increases from 0dBm to 5dBm, the link margin improves by 5dB to 27dB.

The main advantage of an N [latex] imes[/latex] transmit phased array over a large (N [latex] imes[/latex] ) transmitter with large (N [latex] imes[/latex] ) antenna is the fact that the signal from the phased array can be electronically steered to the desired direction, whereas the large transmitter radiates in a fixed direction.

Question 2.10: 60GHz OFDM NLOS 1 phased arrays Consider a 10m NLOS link at ...

This Question has been Answered.

Already have an account?

Login

Related Answered Questions