User:Rubin joseph 10/RF test equipment

Tune test instrment (TTI) is group of electronic test equipment that deal with small signal. suitble for frequency 9 KHz to 100GHz. include the following instrument
 * Signal generator
 * Tracing generator
 * RF Counter
 * Spectrum analyzer
 * Network analyzer
 * Atomic Clock



RF TTI
The TTI using the superheterodyne principle, a signal at variable frequency f is converted to a fixed lower frequency, fIF, before detection. Frequency fIF is called the intermediate frequency, or "IF".

Heterodyne receivers "mix" all of the incoming signals with an internally generated waveform called the local oscillator using a Frequency mixer. The user tunes the radio by adjusting the set's oscillator frequency, fLO. In the mixer stage of a receiver, the local oscillator signal multiplies with the incoming signals, which shifts them all down in frequency. The one that shifts to fIF is passed on by tuned circuits, amplified, and then demodulated to recover the original audio signal. The oscillator also shifts a "copy" of each incoming signal up in frequency by amount fLO. Those very high frequency "images" are all rejected by the tuned circuits in the IF stage.

High-side and low-side injection
The amount that a signal is down-shifted by the local oscillator depends on whether its frequency f is higher or lower than fLO. That is because its new frequency is |f − fLO| in either case. Therefore, there are potentially two signals that could both shift to the same fIF one at f = fLO + fIF and another at f = fLO − fIF. One or the other of those signals has to be filtered out prior to the mixer to avoid aliasing. When the upper one is filtered out, it is called high-side injection, because fLO is above the frequency of the received signal. The other case is called low-side injection. High-side injection also reverses the order of a signal's frequency components. Whether or not that actually changes the signal depends on whether it has spectral symmetry or not. The reversal can be undone later in the receiver, if necessary.

Sensor TTI
Some sensor neaseare there object by check the tuning enfluence on the sensor (SAW Tenprature sensor, SAW Presure Sensor, Ultara Wave sensor )

Ultasonic TTI
Acoustic spectroscopy

Acadmic Research
At the terahertz laser research feild there are all the componnent for TetaHerz superheterodyne receive instrument that Terahtez Comb generator (TCG), Signal frequency laser, optical downconverter. In this way it possible to build teraherz counter- meseare teraherz frequency, teraherz Spectrume Analyser that TTI have spectra  resulution of 10-12 compar with 10-7 spectra resulotion in the  conventional spectrometer

resources

 * Agilent's AN200: Fundamentals of electronic frequency counters is a very good resource
 * Automatic RF Techniques Group
 * eBooks on how spectrum analyzers and spectrum analysis work; and how to build a Spectrum Analyzer
 * Network Analyzer Basics (PDF, 5.69 MB), from Agilent
 * Primer on Vector Network Analysis (PDF, 123 KB), from Anritsu
 * Large-Signal Network Analysis (PDF, 3.73 MB), by Dr. Jan Verspecht
 * Homebrew VNA by Paul Kiciak, N2PK
 * Measuring Frequency Response (PDF, 961 KB), by Dr Ray Ridley
 * PTB Braunschweig, Germany - with link in English language
 * National Physical Laboratory (UK) time website
 * Web pages on atomic clocks by The Science Museum (London)

Category:Electronic test equipment