Why does my Frequency Division Multiplexer demultiplex to negative and not the message signal?

Hi,

I'm working on a project that involves on the practice of communication techniques, designed in simulink. I'm trying to design a Frequency Divison Multiplexer that multiplex 3 modulated signals (AM modulated signals), then demultiplex to obtain the original signals back. However, when designing the demodulation circuit to remove the carrier signal, I'm not sure why its giving a negative amplitude and not the orginal message signals.

I'm confused if its my demodulation circuit or its just the characeristic of an Frequency Divison Multiplexer.

Note: From the multiplexer and modulation, there aren't any issues as its responding with the correct waveform of modulation and multiplex form.

Perameters:

Input 1 - 1volt, 100Hz message, 3kHz carrier, Sine

input 2 - 1volt, 150Hz message, 2.5Khz Carrier, Sine

input 3 - 1volt, 50Hz message, 1.2Khz Carrier, Sine

Saturation (for all) - 0 lower limit, 3 upper limit

Filter Desginer1 - Butterworth, Lowpass, filter order 3, pass band 3kHz

Filter Designer2 - Butterworth, Low pass, filter order 3, pass band 2.5kHz

Filter Designer3 - Butterworth, Low pass, filter order 3, pass band 1.2Khz

Constant (for all) = -0.3055

Figure 1: Circuit Diagram of Demultiplexer & Demodulation

Figure 2: Scope from the Demultiplex, saturation then the Low Pass Filter Output from order.

Figure 2: scope output from the demodulation stage of the cirucit

[Yukthi S]

The filters look fine to me though. Can you share your model for better debugging?