Mini-circuit ADE-1 mixer DC modulation measurement

Input DC voltage is applied to IF port, RF input:40MHz, 5dBm

Voltage mV	Current mA	Attenuation db
600	130	5.1
550	105	5.3
500	79	5.6
450	54	6
400	31	6.4
350	14	7.1
300	6	8.3
250	4	10.3
200	3	13.1
150	2	15.2
130	1	19
100	1	23
80	1	28
60	0.5	37

Mini-circuit ADE-1 mixer S11 Reflection coefficient measurement

The mini-circuit ADE-1 mixer is a diode-ring type passive mixer. As a +7dBm mixer work best at +7dBm of local oscillator input, or at least +4dBm to make it start working. It sounds like a quite huge power, so may be impedance matching is needed to optimize the efficiency of driving this mixer.  

How to do impedance matching? ok, may be we need to know the impedance of this particular component. As not very obviously showing in the picture, the IF and RF port of the mixer is connected to 50 ohm resistor for proper termination.The LO port is connected to the network analyzer for reflection coefficient measurement. Through a 1nF (-16j ohm@10MHz to -1.6j ohm@100MHz) capacitor in series.

The network analyzer is set to 10MHz to 100MHz, in -10dBm low power level, it have a quite high impedance(313ohm@10MHz) and a bit of capacitive (-22j ohm@10MHz).

In -5dBm power level, it's impedance is lowered.

In 0dBm, it's impedance is quite close to 50ohm

In +4dBm, even lower.

In +7dBm, even lower

In +10dBm, Well, it's quite hard to drive because impedance is quite low.

HF band ADF4002 PLL Test

The 36.5-50MHz ADF4002 PLL-VCO circuitry is completed.

The VCO having a tunning range of 36.5MHz ~ 50MHz from 0V to 5V, that translate to sensitivity of  2.7MHz/V. 

The sensitivity of VCO is used to feed into ADIsimPLL tool, generate a second order loop filter of  1KHz bandwidth, 100kHz phase detector frequency and charge pump current 5mA.

The PLL is programmed to lock to 40.0MHz, some noise is observed.

Compare with the output spectrum of Agilent E4432 Signal generator, which is very nice and clean.

Is the PLL phase noise performance good enough? The noise is from VCO or loop filter? 

The bandwidth limit of a small dipole antenna matching circuit

If we model the antenna as an RC circuits, no matter how sophisticated the matching circuits is, the best bandwidth we can get is given by the formula :

T is gain and R is the real component of antenna impedance and C is the equivalence input capacitance of antenna. This equation suggest that the larger the real component of the antenna impedance, the better bandwidth we can get. And the Larger capacitance, the better bandwidth we can get.

REFERENCE

V. Iyer , S. N. Makarov , D. D. Harty , F. Nekoogar and R. Ludwig  "A lumped circuit for wideband impedancematching of a non-resonant, short dipole or monopole antenna",  IEEE Trans. AntennasPropag.,  vol. 58,  no. 1,  pp.18 -26 2010