60GHz line-of-sight link budget Consider a 2m radio link at 60GHz which employs QPSK modulation format and transmits at a data rate of 4Gb/s occupying a bandwidth of 2GHz. Calculate the link margin if the transmitter output power PTX is 0dBm, the receiver noise figure and SNR are 7dB and 14dB,

Question

60GHz line-of-sight link budget

Consider a 2m radio link at 60GHz which employs QPSK modulation format and transmits at a data rate of 4Gb/s occupying a bandwidth of 2GHz. Calculate the link margin if the transmitter output power [latex]P_{TX}[/latex] is 0dBm, the receiver noise figure and SNR are 7dB and 14dB, respectively, and the transmit and receive horn antennas each have a gain of 25dB.

Accepted Answer

The free-space loss over 2m is

[latex]L F S=20 imes \log _{10}\left(\frac{\lambda}{4 \pi d} ight)=74 \mathrm{~dB}[/latex] where [latex]\lambda=5 \mathrm{~mm}[/latex] and [latex]d=2000 \mathrm{~mm}[/latex]

[latex]P_{R X}=P_{T X}+G_{T X}-L_{F S}+G_{R X}=0+25-74+25=-24 \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}+14 \mathrm{~dB}=-174+93+7+14=-60 \mathrm{dBm}[/latex]

That leaves a shadowing and cable þ probe loss margin of 36dB. Alternatively, if PCB
antennas with 8dBi gain are employed, the loss margin is reduced to only 2dB.

Question 2.7: 60GHz line-of-sight link budget Consider a 2m radio link at ...

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