How to combine signals with different sampling times?

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Glo
Glo el 2 de En. de 2015
Respondida: Asfand Haroon el 26 de Jul. de 2022
Hello all,
I am designing a communication system, in which two channels must be combined and sent over the same AWGN channel, and then received at the receiver. I am using BPSK mod/demodulator block from Comm. sys. Toolbox.
Both channels have same Bandwidth (100 kHz), but different carrier frequencies (one sided local oscillator of fc_1 = 22.4 MHz and fc_2 = 23.9 MHz respectively). Moreover, my carrier frequencies are sampled sinusoidal signals at 4*fc:
T_sample_fc_1 = 1/(22.4 MHz *4) = 11.16071429 e-9; T_sample_fc_2 = 1/(23.9 MHz *4) = 10.46025105 e-9;
So, I have to up sample/interpolate the base-band signals with a different up sampling factor, i.e
T_sample_baseband = 1/(100e3); For 100 kHz base-band signal
Upsampling factor for signal 1 = [1/100e3]/[1/(4*22.4e6)] = 896; Upsampling factor for signal 2 = [1/100e3]/[1/(4*23.9e6)] = 956;
Now, the problem starts when I try to combine these two channels to be sent over the same channel.
I have tried using the following blocks to combine them:
- Add - Merge - Create Bus
Simulink returns an error stating that the sample time of both signals are different so they cannot be combined.
I cannot use a rate transition block (without losing deterministic behavior of one of the signals) to make the two sample times equal, because the two sample times are not a rational multiple of each other (like 0.1 s and 0.2 s for example).
I have been stuck at this problem for about 3 weeks, and cannot find the solution to it. Any guidance/recommendation will be highly appreciated. Thanks!

Respuestas (1)

Asfand Haroon
Asfand Haroon el 26 de Jul. de 2022
use the multiplexing technique to pass over the signals using the same bandwith

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