How to match ceramic resonator to 50R?

[neazoi]

Hi I have an SBL1 mixer and I want to follow it by a ceramic resonator (2 pins) CSA6.00MG so as to create a cheap BPF.
How can I match the ceramic resonator inputs and outputs to 50R?

 

[c_mitra]

I guess that the resonator at resonance acts more like an inductor and you can use either a cap or a resistor to match the impedance.

Simplest is to use a 50R resistor in series with the output.

 

[FvM]

The resonator is intended for oscillator circuits, respectively it has no impedance specification. To design a matching circuit, you need to measure the impedance parameters first.

 

[neazoi]

The resonator is intended for oscillator circuits, respectively it has no impedance specification. To design a matching circuit, you need to measure the impedance parameters first.

I don't mind to be too accurate, loosing some signal I guess is ok. Just for the filter to operate. Neither the response is too critical. It will be used to reduce the LO feedthrough in another circuit and allow the IF to pass in I could use an LC, but I thought the resonator to be a simple solution although not optimal as I said. What if I try the series 50R at the inputs and outputs will it work at all? Or should I just try the resonator alone and hope it to provide any filtering?

 

[vfone]

Diode mixers require diplexers at the IF output to provide wideband load for all the mixing products (for improving mixer linearity).
According to Murata, 330 ohms resistors provide good match for their ceramic filters. Other values may affect the filter bandwidth and insertion loss.

 

[BigBoss]

You confuses Ceramic Resonators for Oscillators and Ceramic Filters.
https://www.murata.com/~/media/webrenewal/support/library/catalog/products/filter/cerafil/p11e.ashx

You should choose a Filter not Resonator for oscillators.There are many of them because 6MHz has been used for SIF in Analogue TV Receivers for many years.

 

[neazoi]

Diode mixers require diplexers at the IF output to provide wideband load for all the mixing products (for improving mixer linearity).
According to Murata, 330 ohms resistors provide good match for their ceramic filters. Other values may affect the filter bandwidth and insertion loss.

Can I use ceramic resonators instead of filters (3-pin) in this configuration?

 

[betwixt]

Ceramic resonators and ceramic filters work differently.

A filter is designed to have a pass characteristic covering a wide band, at least a few KHz with 'other' frequencies often dumped to their ground pin . Their impedance is relatively constant across the pass band.

A resonator is designed to have a closely spaced peak and notch in it's response at one frequency and an impedance changing greatly at each of them. In addition, three pin resonators usually have built in loading capacitors from in/out pins to the ground pin to save designers having to install them as external parts.

So, yes you can use a resonator as a filter but expect higher than normal losses and an unspecified pass response. The frequency is likely to be close to but not exactly as marked.

Brian.

 

[FvM]

To illustrate the previous explanation, here's a |S21| and S11 measurement of a similar ceramic resonator, Kyocera PRBC-8.00HR



You see that passband in 50 ohm system is rather wide, > 100 kHz. Quite different from an AM IF filter.

 

[neazoi]

To illustrate the previous explanation, here's a |S21| and S11 measurement of a similar ceramic resonator, Kyocera PRBC-8.00HR

View attachment 149863 View attachment 149864

You see that passband in 50 ohm system is rather wide, > 100 kHz. Quite different from an AM IF filter.

I see
100KHz could be fine in my application, this "filter" is only intended to minimize LO feedthrough to other circuits and the LO is at an IF offset.
Did you use the circuit with the diplexer for this simulation or just a resonator in series with the generator?

 

[FvM]

It's a VNA measurement, resonator with 50 ohm source and load.