Two new filter series for high frequency testing applications–-LC17 and HC17-–provide brick wall characteristics and performance to 7 GHz making them candidates for audio-digital-conversion and digital-audio-conversion (ADC/DAC) test set ups. Such signal conditioning testing is especially important for semiconductor chips and integrated circuits where testing frequencies continue to trend higher and higher. Relevant markets include commercial, industrial, medical, military/defense and test & measurement.
TTE’s new filters leverage the steep roll-off response of Chebyshev topology in 17th-order low-pass 
(LC) and high-pass (HC) designs to address gigahertz frequencies–-much higher than traditional brick wall anti-aliasing elliptical function filters which are typically limited to less than 500 MHz.
These new LC17 and HC17 filters, while not true brick-wall filters, are designed in a way that their steep roll-offs closely resemble brick-wall filters. Moreover, because TTE’s new filters are based on Chebyshev topology, they have a slight ripple in the passband and no ripple in the stopband, unlike elliptical designs which have ripple in both the passband and stopband. Thus TTE’s filters provide desirable stopband performance at high frequency with limited passband ripple.
The passband-to-stopband ratio for the LC17 filter is -50 dBc at 1.19 fo and -60 dBc at 1.27 fo . That ratio for the HC17 filter is -50 dBc at 0.84 fo and -60 dBc at 0.78 fo. The frequency range for both filters is 1 MHz to 7 GHz. Standard or custom cases are available.
A Summary Datasheet for TTE’s LC and HC series (both combined into one PDF) provides additional information about the new LC17 and HC17 filters. Complete technical information is available at the company’s website at, respectively, the Lowpass Chebyshev (LC) page and the Highpass Chebyshev (HC) page. TTE offers low Total Harmonic Distortion (THD) versions of its filters – including the LC17T and HC17T – to improve ADC/DAC testing by reducing the harmonics inherently present in signal generators.
A technical discussion about brick wall filters – and the LC17 and HC17 series – was recently issued by TTE (an affiliate of GCG) entitled “The Need for High Frequency Brick Wall Filters“.
