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RF-PowerTransferStandard.php    6586 Bytes    05-07-2022 17:36:35

RF Reference Source - for Powermeter Calibration

Some kind of a transfer standard

This design is strongly inspired by (A very beautiful website) It has not a sub - milli resolution nor a temperature coefficient of 0 ppm. It generates a sinewave of 100 MHz with approx. - 10 dBm, as we are using mostly 80 MHz or 120 MHz for our experiment. It is intended to verify the functionality of our RF Power Detectors and their synchronism. It is portable and usb powered.

Transfer Power Standard

✈ Principle of operation • Circuit description

From the +5V (nominally 5V±0.25V at up to 0.5A) of the usb port, a low dropout linear voltage regulator (IFX25001-3.3) generates +3.3V for an crystal oscillator of 100 MHz. Following the output of the crystal oscillator is a limiter designed with a BAV99 which limits the output voltage to 1.6 Vpp. After a lowpass (designed for 117 MHz) and an attenuator (10 dB) you should see approx. -10 dBm at the output when terminated with 50 Ω.

✈ Stability / Power Consideration

The voltage regulator (IFX25001 ME V33,IFX25001 TF V33) has a 0.5 mV/K accuracy. This means that a temperature range of 20°C ±10 °C results in an output voltage of 3.3 V ±0.1 V. If we assume that the output voltage (of the regulator) is linearly related to the output of the xco, then we have an output power of 14.349 dBm (±0.3 dB). Variations are smoothed out by the diode limiter. The photo-model uses a 106.25 MHz xco, and a 4 dB attenuator, as the 100 MHz types are stuck in the mail ...

Fundamental, -4.0 dBm
Harmonics, down by more than 50 dB

Transfer Power Standard

The output of the limiter, tested with 10 MHz (squarewave), as the scope has (only) a bandwidth of 100 MHz. Input was 2.0 Vpp but the output is stable over a wide range.

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t1 = 6585 d

t2 = 150 ms

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