Oscillator frequency and Modulator Frequency?

[sunnykpradeep]

I have doubt,i.e; while using encoder ex:HT12E we use some oscillator........while transmitting it we use some RF module ex:TX433


Q1) does the oscillator in the both encoader and oscillator should same?if same why?if not,why?

Q2)Why we require an ocillator in the encoader ?

Q3) How the modulator and encoader's frequencies & oscillator related ?

Q4) how to selest the frequency of the oscillator,i.e; parameters?

Thank you.

 

[Fadi Mkhayel]

no for sure it isn't the same. the oscillator at the encoder is used as a digital clock and consequently determines the speed of operation of the encoder. modulator and encoader's frequencies aren't really related. The encoder give the baseband data which is modulated by the modulator on a certain carrier (frequency).

 

[jpsganesh]

I have doubt,i.e; while using encoder ex:HT12E we use some oscillator........while transmitting it we use some RF module ex:TX433

Q1) does the oscillator in the both encoader and oscillator should same?if same why?if not,why?
Encoder OSC is used to generate data based on key pressed and address line of HT12E. This data will be sent to (modulated) 433MHz transmitter.

Q2) Why we require an ocillator in the encoader ?
OSC used to generate CLK pulses to operate the IC. Based on this CLK pulse all I/Ps (Data & Address) will be read, encoding process and th the data will be generated.

Q3) How the modulator and encoader's frequencies & oscillator related ?
Ref HT12E datasheet page no. 6 & 7 - Timing diagram. In that clearly mentioned how the CLK pulse will be used to generate the data.

Q4) how to selest the frequency of the oscillator,i.e; parameters?
HT12E and HT12D suggested freq are 3KHz and 150KHz
Ref: https://www.edaboard.com/threads/287839/#post1231525 - post 2
Thank you.

For your knowdge:

Nyquist rate [edit]Main article: Nyquist rate
In 1927, Nyquist determined that the number of independent pulses that could be put through a telegraph channel per unit time is limited to twice the bandwidth of the channel. In symbols,


where fp is the pulse frequency (in pulses per second) and B is the bandwidth (in hertz). The quantity 2B later came to be called the Nyquist rate, and transmitting at the limiting pulse rate of 2B pulses per second as signalling at the Nyquist rate. Nyquist published his results in 1928 as part of his paper "Certain topics in Telegraph Transmission Theory."

https://en.wikipedia.org/wiki/Shannon–Hartley_theorem