[Need Help] I/Q Demodulator Impedance Matching 800-1600MHz
I have a problem with my thesis. I have purchased an I/Q demodulator evaluation board with frequency range is match for 800 - 2700 MHz. But what I get is that the I/Q demodulator match (without impedance matching) in frequency range 1500 - 2700 MHz. Whereas the frequency that I want is 800-1600 MHz. From the datasheet I get the information that in can be done by make a impedance matching, but they don't give me the information what is the capacitance of the capacitor. The additional information is the RF input impedance and LO input impedance. The value is like in the picture below.
There is the constrain in the design of impedance matching, that is:
1. the total of transmission line is only 10 mm.
2. only parallel configuration that be allowed.
I have simulated many configuration but the possible configuration is must use resistor. The question is, is it possible if I use resistor to make an impedance matching with the range frequency 800 - 1600 MHz? I mean what is the disadvantage of impedance matching using parallel resistor? As I know resistor is a lossy component. But from my simulator I don't have this information. If I use a parallel resistor the swr can get 1:1.6, but if don't use a resistor the swr is more than 2.
Does any one can help me?
BR//
freqzt
Why don't you start with their recommendation? First rule in electronic design is reading the datasheet!
Thank you for your response.
I have read the datasheet. Like in the picture above,the recommendation is just for 800-1000 MHz and 1000-1500 MHz. My frequency range is 800-1600 MHz. The bandwidth is larger than their recommendation. I have simulate using capacitor with capacitance same like their recommendation but it can't solve it.
Any other suggestion?
For wider bandwidth (one octave in your case), have to use multi-pole matching networks.
http://www.eetasia.com/ARTICLES/2001...URCES=DOWNLOAD
http://paginas.fe.up.pt/~hmiranda/etele/an963.pdf
On the LO side you can use a few dB?s PAD attenuator terminated on the right impedance (actually resistance), but have to increase the LO level in correspondence with the attenuation.