18 Questions 27 Answers 0 Followers
Questions related from Audrius Merfeldas
All base station antennas has 2 polarizations, -45deg and +45deg. I assume that is because mobile device antennas are in various orientations, but are the basestation signals totally the same and...
19 October 2024 751 3 View
Hi, I am doing analysis of Transystem inc. Downconverter model AiDC+1746D with RF=2216-2300MHz to IF=470-554MHz. The issue that I am unable to find frequency synthesizer and mixer, only 6.8MHz...
10 June 2024 8,463 7 View
I am designing pseudo-Doppler direction finder and trying to observe Doppler shift, but I am not able to get it. My system consists of 4 antennas shifted by RF switch. Test signal is 433MHz CW. 4...
09 November 2023 1,567 3 View
Hi, Can anybody explain or provide photos what is inside high power omni antenna? Datasheet: https://www.dlink.com.sg/product/2-4ghz-12dbi-omni-directional-outdoor-antenna/ Thank you Audrius
11 October 2023 5,847 4 View
Why log or yagi DVBT antennas are installed in horizontal polarization, while transmitters are vertical monopoles? We are talking about 470MHz-862MHz antennas. The antenna is as below:...
28 August 2023 5,812 3 View
Hi, Many wideband DVBT antennas has integrated filter for filtering LTE and 5G signals. I have disassembled few of them and found internal filter inside antenna boom. Some kind of filtering can...
24 August 2023 4,091 2 View
I need to do twisted pair cable measurements. I have differential signal generator and two channel osciloscope (Analog discovery 2) for measurements. Cable is around 300m length, but unknown...
14 August 2023 2,925 7 View
Nowadays I see many DVBT antennas on the market that announces to have LTE or 5G filters. Is there any techniques to do filter in the yagi design (parasitic element to filter specific frequencies)...
04 August 2023 4,151 3 View
I am interested of hyperlog antennas that can ensure extremally wide frequency range (lets say for EMC 30MHz - 1GH or above...
04 August 2023 295 5 View
Frequency synthesizers are quite expensive especially for double conversion RF systems. Maybe there are cheaper solutions instead of VCO that might be not such precise. A while ago I was analyzing...
21 February 2023 5,088 2 View
I am wondering why RF power LDMOS impedance are very low while by its nature suppose to be high. I understand that capacitance between gate and source is playing its role, but is it only this? As...
29 November 2022 6,839 2 View
VNA cant handle very high power (talking about 100W and more). There I need to use high power attenuators. How to measure output reflections? Is it only possible to measure S21 and try to achieve...
28 October 2022 3,318 21 View
I have the case where antenna and PCB is inside unknown plastic. Without plastic antenna radiation is very similar to power measured by direct contact measurements. Installing this PCB in plastic...
28 October 2022 2,376 1 View
Hi, I am strugling to find the SMD quadrature coupler starting 100MHz for balanced high power RF amplifier 100MHz to 500MHz. In this case I am planning to make it from coaxial cables. The...
23 July 2022 6,656 2 View
Why carrier amplifier has 100 Ohm impedance at low power in Doherty amplifier? Shouldn't it be 50 Ohm impedance, because the carrier amplifier is always on? What is happening to frequency...
20 December 2021 9,391 3 View
Normally standard RF transistors are soldered to PCB or copper heatsink. For mounting transistor (example BLM10D3438-70ABG...
04 October 2021 3,789 3 View
Would it be any benefit using few antennas connected by power combiner. Wilkinson or other power combiner have losses though increasing RF noise level. On the other hand combining two antennas...
07 November 2020 6,433 13 View
Does S11 parameter matters from receiver point of view? (Here we are talking about GSM signals. For output reflections I am totally sure, but what about imputs). From my point of view bad...
07 February 2020 1,077 4 View
