134
M. El Ghzaoui and S. Das
SNR 1
1
r
N
SNR 2
2
r
N
Signal cophasing
∑
Demodulator
Fig. 5 2-branch MRC receiver
In MRC receiver, the signal amplitude at the transmitter at a given time t i , is
A S, M (t 0 ) it can be expressed as
V S,M (t 0 ) = r 1 (t 0 )
r 1 (t i )
N
+ r 2 (t 0 )
r 2 (t i )
N
=
r 1 (t i )
2
+ r 2 (t i )
2
N
(10)
V N ,M (t 0 ) = n 1
r 1 (t i )
N
+ n 2
r 2 (t i )
N
=
n 1 r 1 (t i ) + n 2 r 2 (t i )
N
(11)
The instantaneous voltage to noise power ratios must be multiplied at t i by their
received signal enveloper.
P N , M (t 0 ) =
r 1 (t i )
2
N 2 E
n
2
1
+
r 2 (t i )
2
N 2 E
n
2
2
=
r 1 (t i )
2
+ r 2 (t i )
2
N
So,
SNR P M (t 0 ) =
r 1 (t i )
2
+ r 2 (t i )
2
N
=
1
N
r 1 (t i )
2
+ r 2 (t i )
2
(12)
MGC Output(dB) = SNR1 + SNR2
(13)
7.4 Alamouti Code in MIMO System with RMC Receiver
To show the basic concept of the Alamouti code in THZ communication system with
RMC receiver, we have considered two transmitting and two receiving antenna block
coding systems. Let h lj be the impulse response from transmitter j to receiver l. We