Dear Vasudev,

please specify the range of low power and operating frequency.

Hi Sir,

Operating frequency is 401-406 MHZ and power consumption is around 1mw for LNA and for Mixer is around 2mw.....

Sir I think Direct conversion architecture is suitable for this, but  It has some problems like 1/f noise, DC offset.....You please suggest me how to overcome these drawbacks .....

Thanks

Vasudev

Receiver architecture is decided by the bandwidth of a channel, number of RF channels, and spacing between adjacent channels. Direct receivers will also receive image frequencies apart from desired carrier. 

A narrow band filter at RF is recommended to remove all other frequencies except the desired signal. Narrow band filters adds extra insertion loss and apart from the cost and size. If size is not constraint, co-axial or cavity type filters can be used.

I agree with the above. Also the cost of your front end is very important. The super heterodyne architecture is a winner in most cases (in regards of performance) but the cost is sky-high. Most receivers use direct conversion since the architecture is low cost and the system performance is adequate for the applications.

Garage door receiver architecture is based on the regen as well as the super regen. In the range of the ISM band 300-400 MHz. Decades ago, SAW resonators were used to control the regeneration oscillator and the stability was quite good. The decode sensitivity at reasonable bps was better than 1 uV. Very low cost. An integrated regen architecture would be compelling!