MiniVNA – return loss of cellular antenna III.
4 antennas tested with MiniVNA Tiny
Once more you will detect the typical faults marked with XXI and XXII. The bandwidth for the lower GSM bands is very small and the triangle marker 1 for the middle of the GSM 900 band is on the right side of the gap. There is a need for a matching circuit for sure. For the higher GSM bands up the UMTS 2100 the antenna looks good. If it will be used for GSM 1800 or GSM 1900 only, then a return loss of 9.5 dB can maybe archived in the final design. For some reasons this antenna shows a resonance at 2400 MHz range as well.
The upper text is out of the IoT M2M Cookbook here. If you are interested in a copy of the book please do not hesitate to drop an email to harald.naumann (at) gsm-modem.de
Remark: The first low budget VNA had a to noisy output. The Smith Chart diagram contained to many loops and at UMTS 2100 and LTE 2700 the noise made the diagram close to unusable. I replaced it to a profesional VNA listed here.