Posted on

Digital Phase Frequency Detector

I have all the hardware I need to complete this project. I’ll be uploading a few pictures and videos in the next few days of this working. I’ve decided to close the loop with the Arduino Uno. The Arduino will receive the output of the phase-frequency detector and change the input. I needed to do this for a few reasons. The time required to assemble and debug the entire phase-locked loop would have taken longer than I would of had. Second the Arduino adds a really interesting component to this project. Since the phase-frequency detector is a very robust you can do things like lock two XBees together and double your sensor bandwidth for 3D imaging.  Or you can use it to drive two wheels forward and keep them moving at the same speed with two electric motors. 
Also the demo kit that NXP sent is awesome for a lot of reasons. It allows easy prototyping of typically difficult to work with surface mount components. The kit shows how small the SMT components are. The additional resistors and capacitors for proper functionality are also included in the dev kit.  I hope NXP would consider selling it would be great to use in electrical designs that would eventually be miniaturized. 
First let’s take a look at a single demo board. There are a few observations about this board I’ll make before I move onto the design.
Figure 1: Single Demo Board (Back)
As you can see in this demo board there are some added resistors and capacitors. This will help to limit the current through the device. In my original schematic I neglected these but it is clear they are needed. Second I wanted to point out the dime to the left of the board in Figure 1. If you compare Franklin D. Roosevelt’s ear to the size of the 74AUP2G57GM his ear is slightly larger! This is a very small chip; ideal for the Internet of Things and wearables.
So I was sent 5 of these boards. I can imagine they are ESD sensitive. I found some ESD Foam and used that to lay out all the boards. The boards for the phase frequency detector are shown below as well as their alignment as it shows in the schematic.
Figure 2a: The initial layout of the boards.
Figure 2b:  The schematic we are wiring to.
The next step to wire these boards as they are represented in the schematic. This was a multi-day process. I went through one board at a time and wired them per the schematic. Some of this progress is shown in Figure 3 below.
Figure 3: Some initial boards wired completed. Wiring and soldering and wiring and soldering…
So after spending time wiring and soldering and then soldering and wiring even more the entire phase frequency detector is assembled and ready to detect some frequency and phase differences! The entire device is shown below in figure 4. 
Figure 4: the entire phase frequency detector
This concludes my post on assembling the phase frequency detector. In the next post we’ll plug it in and turn it on, look at some code and watch some flashing LEDs.
Posted on

Looking at the data

the complete schematic is here:

Schematic for RFID1 simulation


Input and output for RFID1. It may be desirable to increase the DC offset or the amplitude of the output
But i’m going to go with this signal to start and work on refining the output after I breadboard the design.

So there are a few ways to increase the strength of the output signal while still maintaining the necessary modulation of the RFID card. I added a small load on the output. This did reduce the over all time the signal was ‘high’ but it would likely not matter much to the micro-controller. ¬†I increased and decreased the overall inductance and changed the ratios of a few resistors but mostly it led to an instability in the overall output of the signal. ¬†Coilcraft has a few nice 125 kHz RFID inductors on their site that I’m going to add to the BOM and the board layout.

My next step is to work on doing the PCB layout, routing, stack-up, geometry ect and get the board made. Then I’m going to build up and test a breadboard while I wait for the real parts to get in. I’m not going to buy a micro controller yet…I have an arduino device in mind but I’ll post another section on this hardware.