How to Tune a Pass-Reject Duplexer

[00:00:07]Hi everyone. My name is Sofia Gazas. I'm an applications engineer at Telewave and today we're going to talk about how to tune a pass reject duplexer. So, let's start. We have here our BSF compact duplexer and here is our TPRD 4544 and USF duplexer.

[00:00:29]So, before we start, it's important to understand that our duplexer allows simultaneous transmit and receive operation using just a single antenna while maintaining proper isolation between both between both parts.

[00:00:46]So, in this example, we are using the TPRD 4544 which is a four cavities 4-in duplexer.

[00:00:57]A key factor in a duplexer for performance is the length of the interconnect interconnecting cables.

[00:01:04]All of these cables uh are part of the tuning system and directly affect the response. So, all of these cables are a quarter wavelength cable and the cable connected here in the T is especially critical and must be selected careful.

[00:01:23]This one pass um this one side pass the high pass uh frequency and this other uh cable pass the low pass frequency.

[00:01:34]So, uh the tools we require for the tuning are 7 7877616 nut driver 716 open wrench, uh small bladed screwdriver or a tuning tool and N-male 50 ohm load.

[00:01:58]So, each cavity, all of these, has two main tuning to elements. The tuning broad, that is which adjust the pass frequency, and the tuning capacitor, this one, which set sets the reject or notch frequency.

[00:02:17]So, two cavities we will use for the high pass side and the other two for the low pass side.

[00:02:25]So, let's start. We need to connect the VNA output to the TX port and the VNA input to the antenna port.

[00:02:35]And in the other side we connect the terminate to low pass for the 50 ohm load.

[00:02:42]And we'll start with the low pass, so we connect the low the load the high pass side.

[00:02:55]Connect the VNA TX output to the low pass and the VNA input to the antenna.

[00:03:15]Okay.

[00:03:17]Now, we are using our notch driver, open wrench, sorry, and our notch driver.

[00:03:26]And let's pass the slow frequency.

[00:03:56]>> Now let's move it to another one.

[00:04:00]We need to tune first the pass and then after the notch or the reject frequency.

[00:04:28]Okay, now we are using the uh tuning capacitor.

[00:04:36]We are turning load.

[00:04:39]Let's tuning the notch.

[00:05:01]Okay, for the lows uh pass side, we are setting the pass frequency that is uh 452.5 and we are using the tuning capacitor to uh uh reject the high pass that it's 457.5. [music] Here in the screen we have the markers.

[00:05:26]So Okay. Now we can do a fine uh fine and tuning here.

[00:05:38]I have a better insertion loss.

[00:06:06]>> Okay.

[00:06:07]Now, let's move our capacitors.

[00:06:26]Okay. For this specific model, the typical performance performance is around 1 dB of insertion loss, and we get Here in the on the screen you can see we get old that uh 9 dB of insertion loss, that is good.

[00:06:44]And the minimum um the minimum isolation is 75 dB. So, we are getting 87, that is good.

[00:06:53]So, now uh let's move to the high pass side. So, we switch the connections. Let's move our load this side and the output of the or VNA to the high pass.

[00:07:30]Okay.

[00:07:33]Okay. Now, in the high pass side, we're going to pass 457.5 and reject [music] 452.5.

[00:07:43]So, let's see using our open wrench.

[00:08:03]Just a little bit.

[00:08:15]No.

[00:08:21]Smooth.

[00:08:32]Okay.

[00:08:35]So, now we are getting 0.7 of insertion loss.

[00:08:44]Now, let's move our reject frequency with our capacitor.

[00:09:06]And now, let's move the other one.

[00:09:21]Okay.

[00:09:28]Final tuning.

[00:09:55]>> Okay.

[00:09:57]Okay. Now, we can uh do the final tuning just to see how affect if we move the high side how affect our low side.

[00:10:12]And then, we can final our tuning.

[00:10:32]Okay. Now, um we can see on the screen that we are um close to get uh the best performance.

[00:10:39]We can do the final uh tuning or more precise.

[00:10:44]During this step, it's important to use both screwdriver and the wrench at the same time, adjusting the tuning rod while I while tuning it to to ensure the setting does not shift.

[00:10:58]So, let's do it at the same time.

[00:11:05]Just to be sure that it this one doesn't move.

[00:11:14]Okay. 109.

[00:11:23]196.

[00:11:27]Okay.

[00:11:34]Okay. 99.

[00:11:40]94.

[00:11:41]Okay.

[00:11:44]Let's do a fine adjusting to our capacitors.

[00:11:52]They are good.

[00:12:11]Okay, now that change it to the high pass.

[00:12:50]Okay.

[00:13:10]Okay.

[00:13:13]Okay, now both sides are tuned in.

[00:13:19]And we finish with our tuning of the duplexer.

[00:13:25]So, that is ready for operation.

[00:13:27]So, in this video we tuned the duplexer as a complete system. But, if the desired frequencies are significantly uh different from the original ones, the tuning should be done cavity by cavity. So, you need to tune cavity by cavity for separate. And, you can see our video on how to tune a pass reject cavity.

[00:13:50]Thank you for watching this video. I'm Sofia Casas, and don't forget to like and subscribe. If you want to learn more about our products, or if you want to contact us, just visit our website. Have a nice day.