Interesting question about matching

Suppose i have a system of transmitter and antenna. Everyone know that if transmitter is not matched to antena, some of the power will return to the transmitter.
Now consider a receiver connected to antenna. Suppose they dont' match. If the signal comes from antenna to receiver, and there is no match, signal will return to the source, correct? But it means that signal will be transmitted to antenna, so our receive antenna becomes to transmit antenna!
Anyone has an answer?

In theory yes, think in a passive repeater, it takes the sinal from one antenna that is conected direct to other, the reflected wave would behave like this.

but consider practical situation. Think in the reception level . Usually it is very small, the reflected wave is even smaller , so what is going to be the transmited level ? Definetely, that is not reason for practical concern.

I also agree this point, the antenna will leak reflected power. but the efficiency
of leakage may not be same as receiving.

Anyway, the leakaged power from antnna is much smaller than the receiver
power of antenna. So this is OK for the environment.

But how the same antenna is transmitting and receiving at the same time?

That is right. Some people even use this to point a low gain antenna to a
bigger antenna so it can collect part of the energy the big one is
leakening.

First, the antenna can transmit EM wave, it also has the ability to receive, vice
versa. So, if we look the input power and reflected power as two power sources,
and they are superposed on the antenna. In this point of view, transmitting and receiving
are allowed to happen in the same time.

Ofcourse the receiving antenna will act as a transmit antenna but the radiation mechanism is more of a leakage than an intended radiator and also the power levels involved is too low and the effect of this leakage can often be ignored in practical situations.

An antenna can be used as transmitter and receiver at the same time. you have to insert a circulator between the antenna and transmitter receiver sources.

This can be also used in scan blindness problems in antennas.

Or a duplexer is used in CDMA system,in which transmitter and receiver work at the same time.

There will be some delay due to the travelling path from antenna to receiver.