Pulse compression using biphase modulation with Barker code

hello everyone

Please i need your help in a project on which I work.

This project consists to apply the pulse compression to a sinusoidal signal sin (2 * pi * f * t) with f = 25KHz, using a bi-phase modulation (barker code).

But what I got is that the SNR after the autocorrelation between signal transmitted and signal received for the modulated signal is lower than that of an unmodulated signal. So please is that normal, even That one of the advantages of pulse compression is to increase the SNR. And to have good compression a modulated signal must be used. And what we obtained as result is: (SNR1: before correlation, SNR2: after correlation)

For 7bit barker code

SNR1 = 10.4213

SNR2 = 55.9106

For 11bit barker code

SNR1 = 10.5402

SNR2 = 54.0267

For 13bit barker code

SNR1 = 10.2933

SNR2 = 53.4273

Unmodulated signal

SNR1 = 10.3518 dB

SNR2 = 69.3871 dB

and thank you for your help .

(all the results I got using simulation in matlab)