Difference of Receivers

[zeb.waqas]

regards!!
enlist differences between Digital & Analog AM Receiver in........
1> Construction
2> Working
3> Implementation
4> Performance
5> Noise Rejection
6> Stability
7> Gain
8> Power Consumption

 

[mowgli]

Hello zeb.waqas

you are asking a very lot of thing ... by the way let's proceed point by point

1) Construction
the basic block of an analog AM receiver is the classical envelope detector circuit (diode, R, C circuit) while a digital receiver is built around a more complicated processing chain made usually by ADC -> DSP block (it could be implemented by ASIC, DSP, FPGA, GPP or a combination of the above) -> DAC.
In these terms it could seem a simplistic description but it is so a wide topic we are discussing.

2) Working
an analog AM receiver and a digital AM receiver works the same, in the sense that they perform demodulation of the same incoming signals.

3) Implementation
See point (1).

4) Performance
A priori nobody can say wether a digital AM RCV has better performances than an analog one or not. It depends on the devices, their application fields and obviously their costs.

5) Noise Rejection
Implementation of totally analog RCV with very good selectivity and low noise figure could be a very hard task but not impossible, at the expense of cost and size of the device (especially at low frequencies). On the contrary a digital receiver allows you to exploit all the potential of signal processing algorithms with the software running on a programmable device. Obviously digital receivers too have a analog front end (we are still far from the Software Radio ideal of placing the A/D conversion just behind the antenna) so a good design of the analog front end is always required, but the availability of DSP capabilities gives you the possibility to relax the specifications on the analog part and still match the overall requirement of the RCV due to the processing gain provided by the digital part.

6) Stability
This is another crucial point: once it has been fully debugged the SW/FW embedded in a digital RCV has always a deterministic behaviour, while the same thing could be true for a fully analog device at the expense of calibration work during operations or at manufacturing level.
This is one of the greatest advantage of a digital device versus its analog counterpart because in the case of a digital RCV the source of instability (in the sense of different performances for nominally equal devices) is limited.

7) Gain
To evaluate a RCV you should consider parameters like its noise figure or Sensitivity. Gain is more suitable to an amplifier which is only a part of the RCV itself.

8) Power Consumption
It depends on the complexity of the design: modern digital processors (FPGA, DSP, GPP) runs with hundreds of MHz clock and power dissipation is on the order of several Watts. Also ADC are a hungry of power, especially the fastest ones.

Regards
Mowgli