Custom Search
Over 10000 Pages Indexed
Your Host
Click here to read about RF CafeKirt
Blattenberger

... single-
handedly
redefining
what an
engineering website
should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5CCG (5th MOB):
My USAF radar shop

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse
riding business website -
lots of info

•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe©

RF Cafe E-Mail

UHF superhet receiver - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


Victorb
Post subject: UHF superhet receiver Posted: Sat Nov 19, 2005 12:31 pm
Hi people,
I was hoping somebody could give me some advice on an upcoming RF college project. I have to design and construct a simple superhet receiver to pick up an aircrafts pulse modulated transponder signal operating at 1.09 Ghz. At this stage I just have more questions than answers!

How selective should my bandpass filters be, would passive LC filters work at such a high input frequency?

Should I consider using active pin-programmable digital filters instead, would the necessity of an onboard clock be worth the effort? Would power consumption be acceptable? (Device needs to be portable)

For the VCO, should I look for an IC with an external resonant tank or one where it is included?

What kind of intermediate frequency should I be aiming for? Hoping to have the option to drive both audio earphones and input to laptop through parallel port.

Could somebody recommend a good company with a wide range of RF components?

Any information would be greatly appreciated, even if it's just point me in the direction of some decent literature.


Top

Guest
Post subject: SuperhetPosted: Sun Nov 20, 2005 2:16 am
Hi!

Bandwidth needs to be enough to handle the pulse modulation - what's the PRF and the duty cycle? That'll give you a starting point on BW.

LC filters are getting a bit "iffy" at that frequency - try using transmission-line resonators or cavities. Microstrip would also do - but there are whole books on THAT subject!

You won't find a digital filter with a center frequency of 1 GHz that anyone other than the government can afford...

Pulse systems are usually not picky about close-in noise, so either internal or external tank VCO's should do.

For chips, try National Semi and Analog Devices for PLLs, RF Micro Devices for various parts, Sirenza, and the old groups from Motorola (Freescale and On Semiconductor). There are a whole lot of specialized suppliers. You find them by Googling.

Good Luck!



Posted  11/12/2012
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger
    KB3UON

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel