Evaluation of the DC-DC buck converter

2016-12-28

  This is the evaluation reports of various DC-DC converter products that are available in Japan. DC-DC converter is used to provide a stable output DC voltage to its load such as rechargeable battery. We have tested 5 types DC-DC converter samples which is available in Amazon and Ebay. Thanks.   DC-DC-Converter Evaluation Report from Seong-Hun Choe

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Measuring Wireless Power Transfer Efficiency (1)

2016-11-24

Transmission efficiency of the wireless power transfer (WPT) system can be measured with a vector network analyzer (VNWA). The following picture shows how we measured the transmission efficiency of this system. The yellow WPT coil in the left side is connected to the port 1 of VNWA, while the blue WPT coil in the right side is connected to the port 2 of VNWA. The resonant frequency of this system…

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Impedance matching of the WPT coil

2016-11-18

Hello, I will explain how I matched input impedance of the WPT coil to 50 Ohm. Please look at the following picture. You can see that SMA cable is directly connected with the feed coil. Let’s see the frequency characteristic properties of this WPT coil. Frequency range is between 1 MHz and 27 MHz. So the center frequency is 14 MHz (=0.5*(1+27) MHz) that is the resonant frequency of this…

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Measuring Lumped Elements Values for WPT coil

2016-11-16

Hello. I will explain how to measure and  decide  lumped elements values for WPT coil. Here is the WPT coil that I made for my experiments. The WPT coil consists of a resonant coil and a feed coil with SMA connector. The resonant coil is spiral and has parasitic capacitance between the spiral lines and this capacitance make this coil resonate at LC resonant frequency. The feed coil is a…

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Extraction of lumped elements parameters using VNWA

2016-11-10

VNWA3E has special functions to extract the lumped elements parameters of circuits or some components.  Today, I will explain how to use this functions with the following 1 [nF] ceramic capacitor. First, I measured the S11 parameters and other parameters using the special tool which is designed for through-hole components.  We can easily expect that component wire produces parasitic inductance, which results in some resonance at some frequency. The following…

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S-parameters with LTSpice

2016-11-01

The .net Spice function can be used to calculate two port parameters such as Z,Y,H and S parameters. Zin and Zout can also be calculated. The circuit below shows a simple example. This is the bans pass filter (BPF). Here is the LTspice file. ltspice_sparameter   1. Create an input port V1 with a series resistance. The series resistance will typically be 50 Ohm for S-parameters. This resistance will not…

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RF Coxial Switch

2016-10-14

I bought one SP4T (Single Pole Four Through)  switch from one US company. This switch’s size seems to be a little large. I decided to purchase this SW because it shows very small insertion loss and large power capacity. JETSTREAM JTCS4M This figure shows how I measure the insertion loss and other parameters with VNWA. Here is the measured results. Very amazing!

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Measuring impedance of the rectifier

2016-09-20

I built a rectifier circuit for WPT project.  This rectifier is used at receiver to convert AC from the coil to DC. Here are the pictures and the circuit diagram. Please look at the R1 in left side. The R1 is need to match the impedance of the system. The value should be 50 Ohm, But I use 47 Ohm instead here because of the simplicity of the circuit.  The…

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Measuring Attenuator with VNWA

2016-09-20

I am using the vector network analyzer for my WPT project. It is called VNWA 3E (Link) and shows great performance. Last time, I purchased some atteunators at ebay.com. I thought that these attuenators can be used to measure the gain of the RF amplifier. There are 4 types of atteuantors. -3dB, -6dB, -20dB and -30 dB. This is the setup. It is very easy to setup the attuenator. First…

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