The center wavelength of a bandpass filter shifts linearly with changes in ambient temperature—up with a positive change and down with a negative change. The temperature coeficient chart below gives a good approximation of the shift in wavelength for a given temperature change.
VIAVI offers bandpass filters to cover a wide spectrum of frequency ranges within a specified bandwidth, while rejecting unwanted frequencies outside of the desired frequency range.
The ShackLAN Bandpasser contains six high performance bandpass filters in a single compact package and comes standard with filters for 160, 80, 40, 20, 15 and 10 meters.
ADJUSTING SELECTIVITY Each bandpass cavity filter is provided with adjustable selectivity capability. This is accomplished by physically rotating the coupling loops within the cavity to positions corresponding to total cavity attenuations of 1/2 dB or 2 dB.
In Part I of this article, single-pole bandpass filter design was considered for situations where passband flatness is not overly demanding but insertion loss may be a critical requirement.
Several well-known methods exist for designing passive inductor-capacitor (LC) filters with resistive load terminations. However, when LC filters are used to drive the analog input pins of a high-speed analog-to-digital converter (ADC), special consideration must be given to the ADC input impedance.
