ADF7020 ISM BAND TRANSCEIVER module

Found out the ADF7020 radio module is quite popular in market, so just brought some back to get a hands on it.

The ADF7020 chip
This chip, once frustrated me, because it's such highly integrated and it make ones feels that most of the study in discrete RF circuit design is worthless, LNA, quadrature mixer, IF filter, IF amplifier, modulator, demodulator, ADC, power amp, PLL... all-in-one single chip. What a respectable piece of art. It looks like there are no space left for RF designer. But I have to overcome this frustration and test test this little modules.

The module

The module is supposed to be inserted between two UART device as a cable replacement device. It consists of ADF7020 ISM band transceiver, a MCU, which responds for initialization and translate the external UART signal to the data format required for ADF7020. A 11.0592MHz crystal , what an odd frequency, some matching circuit, a SMA connector, a power regulator, and 7 pin interface terminal.
The manufacturer provide with an PC tool to config the module, the tool controls the carrier frequency, RF output power, baud rate etc. I set the carrier to around 443MHz and trying to see if any RF comes out from the SMA connector.

The output

It just fire up RF output once power is turn on, clearly seeing the fundamental 441MHz output, with power level of 15dbm (adjusted figure due to -3db attenuator) and some harmonics, about be 30dbc lower than the fundamental. This is a good start, some real field test have to be done to see how this power level is translating to the actually usable distance.

HP8590D Spectrum analyzer death CRT

The CRT display of 8590D spectrum analyzer is dead. There are a BNC composite video output on the back. Looks like it can output to a TV or something.

Brought back a composite video to VGA converter, it turns out like this.

Mixer compare - NE602 vs BFR93 Discrete Glibert cell

The discrete transistor Gilbert cell mixer which is briefly tested a month before, is that mixer really having a decent performance? Let's compare it with a classic, popular NE602 mixer. Because both mixer do not have 50 ohm output impedance so this time a 4:1 transformer is added to make it more match with the 50 ohm spectrum analyzer.

The board for mixer comparison is consist of upper section discrete Gilbert cell and lower section of NE602 mixer. Left side is RF and LO input connector and the output connector is on the right side.

The 1.6 mm board is a mistake, 1.2 mm would be better.


Transistor Gilbert cell under test, with LO input 27MHz -20dbm and RF input 32MHz -20dbm,
beside the wanted 5MHz mixing product, many other frequency component is observed.


With same input signal. The NE602A mixer give way less spurious component, but the mixing product also lower in power. This may caused by the bias current of NE602 is smaller than the discrete mixer. It is observed that the LO isolation in NE602 is better.

This comparison attempt did not draw any conclusion, further analyst and more test is required to be done.

New NE602 mixer board arrived

NE602 mixer board, built to compare the performance of the previous discrete Gilbert cell mixer.

Datasheet stated that it comes with temperature compensated bias network. I should test this.