Yes, it is possible to simulate two or more signals using the same frequency and combine them in MATLAB/Simulink. This technique is known as frequency division multiplexing.
In your example, you can simulate the BPSK and QPSK modulated signals separately using MATLAB/Simulink and then combine them using an appropriate mixer circuit. However, since the two signals have different bandwidths, you may need to filter them before combining to avoid interference between them.
Regarding the receiver's ability to demodulate Signal 1 correctly, it depends on the receiver's design and the amount of interference caused by Signal 2. If the receiver is designed to demodulate a BPSK signal with a 10kHz bandwidth, it should be able to extract Signal 1 correctly as long as the interference from Signal 2 is sufficiently low. The exact level of interference that can be tolerated depends on various factors, such as the signal-to-noise ratio (SNR), the modulation scheme, and the receiver's sensitivity.
