Elektor_Mag_-_January-February_2021

82 January & February 2021 http://www.elektormagazine.com

Layout
In addition to the already mentioned zigzag pattern for the arrange-
ment of inductors, you have to ensure short, direct connections
to ground. Double-sided printed circuit boards with one side for
signals and one side for ground make this much easier. Especially
at higher frequencies, and therefore lower capacitance, you must
not forget that the solder pads themselves act as little capacitors
with respect to ground. If this is relevant you will need to take
these ‘parasitic’ capacitors into account when selecting the value
of the capacitor.
200522-04

Figure 22: Close-up of the pass-band of the filter in Figure 20 showing the
typical small dip near 75 MHz.

Figure 23: The innards of a filter. Note the positioning of the inductors.

related products

> OWON SDS1102 2-ch Digital Oscilloscope (100 MHz)

http://www.elektor.com/owon-sds1102-2-ch-digital-oscilloscope-100-mhz 

> Siglent SDG2042X Arbitrary Waveform Generator

(40 MHz)

http://www.elektor.com/siglent-sdg2042x-arbitrary-waveform-generator-40-mhz 

> OWON XSA1015-TG Spectrum Analyser

(9 kHz – 1.5 GHz)

http://www.elektor.com/owon-xsa1015-tg-spectrum-analyser-9-khz-1-5-ghz  

[1] “Analogue Electronics Design - Part 1: Analogue filter theory”, Alfred Rosenkränzer, Elektor September/October 2020:

http://www.elektormagazine.com/magazine/elektor-155/58969

[2] LC Filter Design Tool: https://rf-tools.com/lc-filter/

[3] AADE: https://getwinpcsoft.com/Filter-Design-179557/download/

[4] Quickfil 5.1 (DOS program): http://www.omicron-lab.com/products/vector-network-analysis/quickfil/

[5] Simetrix: http://www.simetrix.co.uk

WEB LINKS

Contributors

Idea, circuits and text:

Alfred Rosenkränzer

Schematics: Patrick Wielders

Translation: Arthur de Beun

Editor: Stuart Cording

Layout: Giel Dols

Questions or Comments?

Do you have any questions or comments related to this article?

Then email Elektor at [email protected].

Figure 24: A filter in SMD technology with inductors at an angle of 90°.
Noticeable: the blue inductors are not connected in series and the
capacitors are not connected in parallel.