The HF2LI-MOD is an option for the HF2LI and allows for the direct analysis of sidebands in dynamic AM (amplitude modulation) and FM (frequency modulation) schemes. This option helps the user to precisely measure periodic variations in the frequency or the amplitude of the application signal. Such schemes are typically applied in oscillator and resonator related setups.
HF2LI-MOD 주요 특징
HF2LI-MOD 업그레이드 및 호환성
HF2LI-MOD 기능 다이어그램
HF2LI-MOD Amplitude Modulation
s(t) = [ Ac + Am * sin(ωmt) ] * sin(ωct)
In AM the amplitude of a carrier signal is periodically changing (modulated). In most applications this modulation is small and is therefore subject to noise. The purpose of measuring an AM signal with a lock-in amplifier is to take advantage of its steep filters to recover the signal of interest. As the AM spectrum consists of 3 bands, the HF2LI-MOD uses 3 demodulators to demodulate all 3 band simultaneously providing the best-in-class signal recovery performance. Simultaneous amplitude modulation and demodulation is supported and can be entirely controlled from the graphical user interface of the HF2LI. The generation of AM signals is useful for stimulus generation in the application, but is also handy for system testing purposes.
HF2LI-MOD Frequency Modulation
s(t) = sin[ ωct + ωp/ωm * sin(ωmt) ]
In FM the frequency of a carrier signal is periodically changing (modulated). As the modulation is often a small signal and therefore subject to noise, the demodulation with a lock-in amplifier can be advantageous thanks to its configurable filtering. The HF2LI Lock-in Amplifier is capable of demodulating a signal of interest at several frequencies simultaneously, and the HF2LI-MOD option provides the FM demodulation at the carrier frequency and at the first sidebands (ωc ± ωm). The HF2LI-MOD frequency modulation is optimized for narrow-band operation, meaning that the peak frequency deviation ωp and the modulation frequency ωm shall satisfy ωp/ωm << 1. However, the HF2LI-MOD operates also at peak frequency deviations up to the limit ωp/ωm < 2 with a decreasing accuracy.
HF2LI-MOD User Benefits
|AM and FM Specifications|
|ωc, fc: carrier frequency range||0.7 µHz - 50 MHz|
|ωm, fm: modulation frequency range||0.7 µHz - 50 MHz|
|ωs, fs: sideband frequency||fs = m * fc ± n * fm|
|Ac: amplitude of carrier signal||Ac < Vrange|
|m,n: harmonic analysis||m,n = 1 to 32|
|hAM: AM modulation index||hAM = Am / Ac|
|Am: amplitude of modulation signal||Ac + Am < Vrange|
|hFM: FM modulation index||hFM = fp / fm|
|ωp, fp: peak frequency deviation demodulation||fp < 2 * fm|
|ωp, fp: peak frequency deviation modulation||fp < 12'000 * fm|