Hi Payalneg,
nice to hear about progress. I did decoder in cpld (VHDL in lattice machx02) but as far as i can tell it is overkill. I had bpsk to spi converter in cpld but i still needed mcu for pc interfacing. I choose to override need for cpld by using faster mcu.

regards

Brano

I just did today programmer for epm3064. Today, digital phase detector will be finished by Howard. Calculate crc via cpld probably not a problem Wait and see.
I posted a couple of posts above MCU computer

you have more option in cpld. I used different approach. I measured pulse widht in cpld and ignored too short and too long pulses. So you can take in to account only pulses let say between 90-110ns for normal and 170-220 for phase change pulses. In this case you can align perfectly to pulse edge and can have tolerance for freq deviation.

You'll probably want to change your criteria for detecting a phase change. Some transponders (particularly MRT PTX) will generate two short pulses rather than one long pulse during a phase change, due to the tuning and relatively high Q of the tank circuit. If the detector ignores the short pulses, it will miss the phase change.

Howard, if you need Digital Phase Detector in CLPD, please PM me.

This is exciting! Can you fit all of the digital circuitry into the PLD?

I think yes. I will start this work after test my device

really very interesting these posts!
I'm french, I'll try to make the phase detector ? Do you think it's possible to connect the phase detector after the original AMB loop (wire with 470ohm resisitor and balun) ?
to reduce the parasitic noises, why not put a 5MHz filter before the amplifier loop?

thanks

You'll still need amplification and a comparator with some hysteresis to create the digital input levels necessary for the phase detector. The tank circuit formed by the timing loop and its parallel capacitance filters at 5 MHz, so it would be best to not use the 470R resistor and balun transformer. It might be possible to use more filtering, but if you use too much then the system won't follow the modulation very well. It's certainly worth trying if there are noise problems.

OK,

What is the unit used to make your loop? foot, inch ?
I think is foot.
For an outdoor application on our circuit I need a 1' x 13' minimum loop.
What is the minimal input level for the pase detector circuit ?

I think I'll start with your installation with your loop decoding to understand and see the analog levels.

thanks.

I'm using a 1x8 foot loop. You can use a larger or smaller loop by changing C1 in the loop amplifier to make the loop resonate at 5 MHz. (The tuning is not very critical.) For experimentation, it's easiest to just use a trim capacitor for C1.

The phase detector requires 5V CMOS logic levels: <0.6V low, > 4.4V high.

Here are the schematics for the loop amp and phase detector input amp, which should be used together:

http://www.rctech.net/forum/11802000-post68.html

I have done the loop amplifier. I have only 140mV peak to peak AMB transponder, the signal level is it correct before I build the phase detector input amp ? On the 42 post you have 200mV peak to peak.


Thanks.

That will work fine. The phase detector input amplifier provides the rest of the gain needed.

I have a problem with the phase detector input amplifier.
When I connect Q4 output to the 74HC04 input, the signal is disturbs. Before the 74HC04 input, signal is perfect centered to 2,5 V.
Have you met this problem before ?
thanks

That isn't a problem. What you have observed is normal.