Because you haven't given the current gain β of 90 13 and the capacity value of C 1, and the impedance value of the load behind, you can only roughly estimate the values of R 1 and R2: R 1 kω, and R2 takes 201k. But the duty cycle must not be 50%, because your circuit does not set a static operating point circuit for the transistor Q 1, and the on time of the transistor must be less than the off time.

In fact, the simplest way to convert sine wave, triangular wave and sawtooth wave into rectangular wave is to use inverters in logic devices, such as CD4069, MC 14069, 74HC04, 74HC 14 and so on. As long as the AC signal is connected to the input end of the inverter through capacitive coupling and then the signal is taken from the output end of the inverter, usually a rectangular wave can be obtained by one inverter. See the picture below-