Hi,
I have these two circuit (transmitter and a receiver) i have to understand the circuit and pick values for it. The operating frequency is meant to be 12 MHz and the transmitter circuit is meant to have 50mW MPT.
I have attached the circuits and i will write up what i understand so far, please feel free to add to my description so i can get a clear picture of the circuits which should enable me to analyse the circuit by hand roughly then in LTSpice.
Analogue Transmitter (1):
The input is a 0-9V square wave that is manchester encoded (aka modulating signal).
R1 is a filter, both R1 and R2 are potential dividers to make sure we don't blow up Q2
Since the waveform is a square it's made up of many sine waves (Fourier series) so C1 is meant to filter out those high order harmonics ie it controls the width of bandwidth (anything else?)
Q2 is a transistor switch which is meant to turn the crystal oscillator Y1 one and off.
When Q2 is on R4 is shorted and oscillator is off and vice versa
The term that was coined around was it's a OOK modulation (which is also known as ASK not sure if it's same or OOK is a form of ASK)
So modulation is the act of adding information to an unmodulated signal (carrier), having 100% modulation for this circuit. With amplitude modulation there will be side bands (AM is for sine or square waves so for square we are doing ASK i am assuming). This will probably make the output like bursts of OFF (absence of carrier) with bunched up waves ON.
Not really sure on this modulation, ASK,OOK thing
Y1 is a crystal oscillator, it provides a stable frequency it has a very high Q factor (measure of sharpness or selectivity of frequency response of circuit). An oscillator is an amplifier with positive feedback from output to input. It has series and a parallel resonance frequencies (i can use the 12MHz specification but not sure which one to work out first what do it mean by series/parallel resonant frequency?). So over this very narrow band the crystal is basically inductive, but i do know i will be using the series one as it's a good approximation to the operating frequency. Which transistor is providing the feedback?
R3 and R4 are biasing resistors which are meant to drive Q2 to active region (thus an amplifier), why do we need VDD? from specs max current through a BF199 is 25 mA and Beta is 40. They form a potential divider as well.
C2 C3 and Y1 form the colpitts oscillator
All i get is, in normal operation amplifier shifts the phase by 180, the tapped capacitance provides another 180 shift thus 0 in total (ie positive feedback?). Is there an RFC choke in this circuit?
Q1 and R5 plus R3,R4 makes an emitter follower configuration, according to the reference sheet i have at A i am supposed to get about 4V V p-p with 5V DC.
C4 blocks DC
B C is meant to be a matching circuit (Pi network) which is meant to match the output impedance of source (oscillator i think, for resistance i can probably take R5 but not sure how to get the reactance). Pi network has a Q as well but it's different to the one from oscillator only thing it has in common is the operating frequency. I am not sure how to pick a suitable Q so can't really calculate the L C values. It's mostly meant to act as a filter and work at that operating frequency.
C5 and C7 are meant to be trimming capacitors (not sure what they are doing in this cct for sure)
Antenna is just a wire in this case so we are meant to pick a suitable resistance 50 ohm is appropriate.
B is meant be about 4 V p-p and C is meant to be about 6 V p-p, not sure why it's 6 V cause i don't see any amplifiers there, meant to transfer about 5-35 is mW.
Analogue Receiver (2):
TP1 is meant to be about 100 mV p-p
C1 is meant to be block any DC i think
C2,C3 and L1 are meant to be part of a parallel tuned resonant at operating frequency (what does that mean exactly?)
C4 no idea
Q1 is an amplifier never seen anything like it, i have done small signal on a collector feedback circuit, someone said this is an emitter feedback?
TP2 is meant to be 2 V p-p AC with 2 V DC (where does the DC come from?) the 2V is the amplification of 100mV AC.
D1 is a rectifier diode with the resistor and capacitor it's a detector circuit (AM demodulation) it's half wave rectification where C is meant to boost the mean value of the output. So the wave will have a DC level and with the capacitor inside the RF bursts the square wave will be a smoothed signal?
The first op amp is meant to be a filter not sure what else to make of it. R5 and R6 is a potential divider (why is that needed)
C7 ensure there is no DC signal
The opamp second one is meant to be a comparator and all that is connected to a connector. Inputting a high voltage at input to saturate the op-amp and compare the voltages at it's inputs, so when input AC is negative the output is a positive saturated square wave.
I am not sure what R9,R10 are also potential divider (why is that needed) no clue about R7
Both are meant to be used as non-linear op amps i think.
TP3 is meant to be 5V manchester encoded signal that we put in from the transistor
It's a bit to digest, my knowledge of receiver is far less then the transmitter so would like some concept cleared there and purpose of the components basically any explanations or references will be welcome. Then there is the case of analysis.
THanks
I have these two circuit (transmitter and a receiver) i have to understand the circuit and pick values for it. The operating frequency is meant to be 12 MHz and the transmitter circuit is meant to have 50mW MPT.
I have attached the circuits and i will write up what i understand so far, please feel free to add to my description so i can get a clear picture of the circuits which should enable me to analyse the circuit by hand roughly then in LTSpice.
Analogue Transmitter (1):
The input is a 0-9V square wave that is manchester encoded (aka modulating signal).
R1 is a filter, both R1 and R2 are potential dividers to make sure we don't blow up Q2
Since the waveform is a square it's made up of many sine waves (Fourier series) so C1 is meant to filter out those high order harmonics ie it controls the width of bandwidth (anything else?)
Q2 is a transistor switch which is meant to turn the crystal oscillator Y1 one and off.
When Q2 is on R4 is shorted and oscillator is off and vice versa
The term that was coined around was it's a OOK modulation (which is also known as ASK not sure if it's same or OOK is a form of ASK)
So modulation is the act of adding information to an unmodulated signal (carrier), having 100% modulation for this circuit. With amplitude modulation there will be side bands (AM is for sine or square waves so for square we are doing ASK i am assuming). This will probably make the output like bursts of OFF (absence of carrier) with bunched up waves ON.
Not really sure on this modulation, ASK,OOK thing
Y1 is a crystal oscillator, it provides a stable frequency it has a very high Q factor (measure of sharpness or selectivity of frequency response of circuit). An oscillator is an amplifier with positive feedback from output to input. It has series and a parallel resonance frequencies (i can use the 12MHz specification but not sure which one to work out first what do it mean by series/parallel resonant frequency?). So over this very narrow band the crystal is basically inductive, but i do know i will be using the series one as it's a good approximation to the operating frequency. Which transistor is providing the feedback?
R3 and R4 are biasing resistors which are meant to drive Q2 to active region (thus an amplifier), why do we need VDD? from specs max current through a BF199 is 25 mA and Beta is 40. They form a potential divider as well.
C2 C3 and Y1 form the colpitts oscillator
All i get is, in normal operation amplifier shifts the phase by 180, the tapped capacitance provides another 180 shift thus 0 in total (ie positive feedback?). Is there an RFC choke in this circuit?
Q1 and R5 plus R3,R4 makes an emitter follower configuration, according to the reference sheet i have at A i am supposed to get about 4V V p-p with 5V DC.
C4 blocks DC
B C is meant to be a matching circuit (Pi network) which is meant to match the output impedance of source (oscillator i think, for resistance i can probably take R5 but not sure how to get the reactance). Pi network has a Q as well but it's different to the one from oscillator only thing it has in common is the operating frequency. I am not sure how to pick a suitable Q so can't really calculate the L C values. It's mostly meant to act as a filter and work at that operating frequency.
C5 and C7 are meant to be trimming capacitors (not sure what they are doing in this cct for sure)
Antenna is just a wire in this case so we are meant to pick a suitable resistance 50 ohm is appropriate.
B is meant be about 4 V p-p and C is meant to be about 6 V p-p, not sure why it's 6 V cause i don't see any amplifiers there, meant to transfer about 5-35 is mW.
Analogue Receiver (2):
TP1 is meant to be about 100 mV p-p
C1 is meant to be block any DC i think
C2,C3 and L1 are meant to be part of a parallel tuned resonant at operating frequency (what does that mean exactly?)
C4 no idea
Q1 is an amplifier never seen anything like it, i have done small signal on a collector feedback circuit, someone said this is an emitter feedback?
TP2 is meant to be 2 V p-p AC with 2 V DC (where does the DC come from?) the 2V is the amplification of 100mV AC.
D1 is a rectifier diode with the resistor and capacitor it's a detector circuit (AM demodulation) it's half wave rectification where C is meant to boost the mean value of the output. So the wave will have a DC level and with the capacitor inside the RF bursts the square wave will be a smoothed signal?
The first op amp is meant to be a filter not sure what else to make of it. R5 and R6 is a potential divider (why is that needed)
C7 ensure there is no DC signal
The opamp second one is meant to be a comparator and all that is connected to a connector. Inputting a high voltage at input to saturate the op-amp and compare the voltages at it's inputs, so when input AC is negative the output is a positive saturated square wave.
I am not sure what R9,R10 are also potential divider (why is that needed) no clue about R7
Both are meant to be used as non-linear op amps i think.
TP3 is meant to be 5V manchester encoded signal that we put in from the transistor
It's a bit to digest, my knowledge of receiver is far less then the transmitter so would like some concept cleared there and purpose of the components basically any explanations or references will be welcome. Then there is the case of analysis.
THanks
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