Identify components for RC circuit

[Freak174]

Identify components for RF circuit

Hi there!

I just finished a course in Radio electronics and found it very interesting and thought that doing my own circuit would give me so much more experience and for sure some headache along the way but its totally worth it!

The first step is to decide how complex I want it to be, and because it's my first time I will go for something easy and later on if I feel it was worth the time.. make it more complex.

Because I am a student I would like to go as cheap as possible right now, so I am trying to find components from ebay. Because I believe if you buy from original sites you have to order many pieces and that the shipping is high. Please correct me if I'm wrong here!

1. Frequency range:
Frequency range will be between 2.4-2.5GHz because here in Sweden it doesnt require any license.

2. What kind of topology do I want?
There are two easy topologies I'm thinking of, heterodyne and homodyne. If I choose the homodyne I don't have to think about the image frequency, but at the same time I will have some problems with a leaking oscillator through the mixer (LO feedthrough).
What would you recommend as a rookie?

Lets assume I want to do a homodyne, the main parts needed are:LNA, mixer, oscillator amplifier. We will consider the filters and attenuators later.

3. Components:
Mixer: Up- downconverter, a mixer that can go from DC and up is the ultimate case.
I've only found one named "MC13143D" that converts from DC to 2.4GHz at ebay, but the fact that it doesn't go further than 2.4GHz makes me feel that I'm limited due to the fact that I can't transmit below 2.4GHz. What I'm trying to say, the VCO I've found goes between 2.4-2.5GHz, so the output will be 2.4+x GHz (where x is the signal I want to transmit, perhaps sound or voice). Will this be a problem?

Datasheet: http://pdf.datasheetcatalog.com/datasheet/motorola/MC13143D.pdf

Oscillator: Here I've found a good VCO I believe, the name is MAX2750 (cost:7.5$) and covers a range of 2.4-2.5GHz. Due to phase problems I will have to include a PLL aswell.

Datasheet: http://datasheets.maximintegrated.com/en/ds/MAX2750-MAX2752.pdf

PLL: I've found one PLL that covers upto 2.4GHz named "SP5748".

Datasheet: http://pdf.datasheetcatalog.com/datasheet/zarlinksemiconductor/zarlink_SP5748_JUL_01.pdf

Amplifier: Here I've also found one, it covers all frequencies between 0.5-2.5GHz named "VNA-22" (cost:13$).

Datasheet: **broken link removed**

LNA: A front-end LNA covering the 2.4GHz band named "CC2591". These are made for Zigbee, but I dont believe it will be a problem, or?
Looking at the datasheet it says "Noise figure, High Gain Mode: 4.8dB", isn't that way to high?

Datasheet: **broken link removed**

Filter: When we receive the signal from the antenna, we have to make sure that only the desired signal is passing. So we need a bandpass-filter. Should you buy one that is premade or can I simply make one myself?

4. Connect all these together:
* About the impedance matching, I only need to consider it where the antenna is being connected to, correct? In that case, in receiver it's the LNA and transmitter amplifier?
* When I want to solder all the components together, can I do it all on a single PCB? Does the range between the component affect anything?


I have been searching alot, but I cannot find any guide where radio IC components are being used. It seems like this is a dead area for newbies that want to make a radio system. So today I took the decision to give up on searching and ask here instead.


Cheers!

 

[BradtheRad]

Yes, I have always tried to wait until I want to order several items, so that it's worth it to pay the costly 'minimum' charge for shipping and handling.

Ebay is all right, if the seller has very few negative feedbacks. Even so, many vendors are in a certain far East land, and you don't always know what you're getting.

------------------------

A radio transmitter/receiver consists of several sections, all of which have to function properly and cooperate together. Do you have a working system to start? Then you might carry out your project in stages:

1) Build the receiver first, to make sure you can detect a broadcast.

2) Build the antenna. Improve it and increase distance of reception.

3) Build the transmitter. Adjust it so you can pick it up on your receiver.

Etc.

 

[godfreyl]

Re: Identify components for RF circuit

Because I am a student I would like to go as cheap as possible right now, so I am trying to find components from ebay. Because I believe if you buy from original sites you have to order many pieces and that the shipping is high. Please correct me if I'm wrong here!

Hi

A couple of points to bear in mind:
a) Beware of fake / counterfeit / remarked components. There's a lot of that on ebay. Be especially wary of "bargains".
b) The policies of online dealers like RS-online, Digikey and Mouser may not be as bad as you think. It's worth using their websites anyway, even if you don't buy from them, as the search facilities make it easy to find what you're looking for.
c) Some companies, like Texas, give away free samples. You don't even have to pay for the shipping. See their websites for details.

BTW, you might want to ask the mods to fix the thread title. I ended up here because I thought it was a question about how to calculate the values for an RC filter or something. You can use the "report post" button below your first post to contact the mods.