homodyne and heterodyne....

[A.Anand Srinivasan]

i would like to know the difference between a homodyne receiver and a heterodyne receiver....

Some circuit illustrations would be of great help.....

 

[dhasmana]

The difference betwen a homodyne and a heterodyne receiver is that in a heterodyne receiver there in an IF (intermediate frequency) conversion , whereas in a homodyne receiver there is no IF conversion done.

 

[gnjus]

I recommend you look "RF microelectronics(Razavi)" chapter 5 Transceiver Architectures.

 

[sonal]

In order to measure to high resolution, both homodyne and heterodyne systems need to precisely determine the phase of the returned interference signal.

Homodyne systems measure phase by comparing the intensities of two sinusoidal signals (sine and cosine). By contrast, modern heterodyne systems measure phase by timing the arrival of zero crossings on a sinusoidal signal (see first figure).

Because the signal slope at the zero crossings is nominally 45º, phase noise ≈ intensity noise. Therefore the influence of noise on both systems is effectively the same.

The second and third figures illustrate this point. The graphs show the effect of 5% pk-pk noise on heterodyne and homodyne systems in a plane mirror interferometer.


Heterodyne - the zero crossing point shifts by ±1.25 nm
Homodyne - the Arctangent result shifts ±1.25 nm