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Harros said:Well, any idea on the way to determine the inductor Q?
How to determine the capacitance range of the tuning capacitor for the ferrite core loop antenna (the rx loop attenna)?
k7elp60 said:There is a modification of this formula,Fr=1/[2 x pi x sqrt(LC)], that I have used often. It is LC=(25330/f*f) with the following conditions. L= inductance in uh, C= capacitance in pf and f= frequency in Mhz.
The last frequency mentioned was 1Mhz so LC=25330.
I have done some work with circuits on the US AM broadcast band,approximately(550Khz to 1650Khz) and have used approximately 250 uh off the shelf inductors and then calculated a appropiate capacitor using the above formula to create a resonate circuit.
Just thought this info might be helpful.
Ned
Harros said:Can I measure the inductance of the ferrite antenna using this method?
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Harros said:Hi, I found a book titled "Small Antenna Design". A formula is introduced in this book to approximate the radiation resistance of the loop. Is it suitable to estimate the resistance in the loop for our case? By the way, it is quite fussy for me (I am running out of time to get this project done ) to measure the Q of the loop...
Can I put the secondary loop next to the primary loop? Or is there any better orientation that would maximize the antenna gain?
Sorry for my unclear question. Well, for the tx antenna, how should i put the secondary loop? Should I put it next to the primary loop (as shown in the picture)? Or is there any other way to put it?RadioRon said:I'm not sure I understand what you mean by secondary loop. Can you explain?
Do you mean that i may use the equation in the text to estimate the Q of the loop (the loop in tx antenna)?RadioRon said:The text reference seems OK to me so you can use that to estimate your radiation resistance.
Harros said:Sorry for my unclear question. Well, for the tx antenna, how should i put the secondary loop? Should I put it next to the primary loop (as shown in the picture)? Or is there any other way to put it?
**broken link removed**
Do you mean that i may use the equation in the text to estimate the Q of the loop (the loop in tx antenna)?
Another question: I have found that in many RF pcb designs, the designer intentionally leave most of the copper on the pcb (They only remove the copper nearby the circuitry, by the way, I usually remove all the useless copper but the copper for circuitry on the pcb). Why they do so?
RadioRon said:The equation allows you to estimate radiation resistance. This is the value that accounts for the loss of power to radiation, it is not a resistance that turns power into heat. There is some of that too, but that is conventional wire resistance and it is added to the radiation resistance to find the total resistance. So, the overall Q of the antenna will be the ratio of inductive reactance to the sum of the radiation resistance plus wire resistance. I think the text formula only estimates the radiation resistance so it is up to you to guess or measure or estimate the wire resistance.
RadioRon said:RF designers usually leave a lot of copper on the board because they want to have a "ground plane". This is usually a sheet of copper on one side of the board or on an inner layer of a multilayer board that acts as reference for all your circuit's return currents. I think it is too difficult to explain the reasons we use a ground plane in detail in a post, so try looking up some references that discuss the purpose of a ground plane and see how far you get with understanding it.
Yes, that formula is correct for inductive reactance. Yes, the total equivalent series R of the coil is the sum of those two.Harros said:So, can we estimate the inductive reactance using this formula: X=2*pi*f*L? Do you mean that the equivalent series resistance of the coil = radiation resistance + conventional wire resistance?
Well, in my design, should i provide ground plane to all the circuits in this project? (From the text that I read from internet, a ground plane will make easier the design of the pcb circuit)
Another question: Which type of capacitors are suitable for filters building in this project? Can I mix the surface mount components (inductors) with non surface mount components in circuit building?
Harros said:For the secondary loop of the tx antenna:
As mentioned in your previous post, the number of turns of the secondary loop should be adjusted to get the best impedance match. How should i infer the impedance of the secondary loop (the number of turns) for the impedance matching? Does the impedance of the secondary loop equal to the conventional wire resistance of the second loop?
Harros said:Again, what is the suitable gain of the discrete amplifier (at the receiver) that i should build?
I do not understand. You have not defined the purpose of this amplifier enough yet. Is this amplifier shown in your diagram? If you are referring to the RF amplifier between the filters on your diagram, then I do not expect the signal to get as high as 4Vpp. This is meant to be, as we call it, a small signal amplifier, that is, one that does not have to deal with large voltage swings.Harros said:Hi, is the BJT amplifier suitable for a sin wave with a swing around 4vpp amplification? Or any suggestion on the amplifier that should i build for the above-mentioned purpose?
For each channel, we have the choice of having only 20 dB to start with, using one transistor, or we can decide to put two transistor amplifiers in cascade to get 40 dB. More than this would not be a good idea. The sensitivity of the phase detector is about -60 dBm (if I recall correctly), so we can expect that one amplifier stage in front of that chip will improve the sensitivity to about -75 dBm. This might be enough for your purpose. I suggest that we settle for using one amplifier for each of the two channels in hopes of getting sensitivity of -75 dBm. It is important that the amplifier provide not only power gain, but also a reasonable noise figure. For now, we will focus on gain and not worry too much about noise figure since this is difficult to measure anyway. We might assume that if we build a good amplifier, we might hope for a noise figure of about 4 dB or less.Harros said:By the way, there is only one amplifier for each channel in my design (as shown in the diagram). Will the amplifier provide enough amplification (20dB) for the received signal? Or should i add another amplifier in the design (each channel in receiver part)?
Harros said:I have designed an amplifier using 2N2222, however the gain is just around 10... Is there anything that i have done wrongly in designing this amplifier?
Are 2N2222 and 2N2222A the same BJT transistor?
RadioRon said:I do not understand. You have not defined the purpose of this amplifier enough yet. Is this amplifier shown in your diagram? If you are referring to the RF amplifier between the filters on your diagram, then I do not expect the signal to get as high as 4Vpp. This is meant to be, as we call it, a small signal amplifier, that is, one that does not have to deal with large voltage swings.