[SOLVED] X-Band Multiple Channel Config

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Hello all,

I am working on designing a X-band radar for motion detection. Problem I am facing now is that I will have multiple Tx/Rx channels(connected to diferent antennas) running(pulsed radar) and I need to synchronize or lock them to each other somehow. I have some ideas but not sure which one would work.

1-) A way to synchronize different VCO's to each other. I checked out some PLL's, however in their datasheet RefinA and RefinB refers to complementary signals and not two distinct signals.
Can anyone suggest a way to do it?

2-) Using a switch to alternate between Antennas; however, due to high power nature of PA, I'm not sure what would be the effect of thermal memory on that.

3-) Using a N-way Divider at the output of VCO, then using the divided signals as Tx_signal in different channels.

Ideas are appreciated on the matter.

Kind Regards,

ktr
 

I think you don't have to synchronize the RF signals coming from the VCOs, but you can synchronize the pulses.
Synchronizing the pulses should be an easy job, using a microcontroller or even simple digital logic ICs.
Now depends what power you have, but you can get high-power (100W or even more) PIN diodes which can be used as switches up to 12GHz.
**broken link removed**
 

My problem is the VCO I have dont have enough power by itself to support multiple mixers.
I think I will use 2 PLL's using same XCO, then those VCO's will be locked to the same source, hence I can use N-way divider before Tx_PA and give the aforementioned Rx channel mixers same LO.

@vfone

vfone said:
Now depends what power you have, but you can get high-power (100W or even more) PIN diodes which can be used as switches up to 12GHz.
**broken link removed**
Click to expand...

Do you think using these diodes is a bettter way of switching compared to controlling gate voltages of PA's? Tx channels will not transmit at the same time.
 

Switching the PAs is better choice than using PIN diode switches, which have limited isolation vs frequency.
Have to be sure that settling time of the PAs during their switching is good for your application. Usually, higher the power, higher is the settling time.
 
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    ktr

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For 10GHz radar I would try 5GHz VCO + relatively cheap 6GHz switches + 5ghz doubling mixer. I have seen such approach used to switch between 10 or more antennas from a single VCO.
 
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I found a switch which I thought good for me. https://www.analog.com/en/products/adrf5027.html this one(SPDT)

I am thinking of giving a control voltage with duty cycle proportionate with PA's settling time + Tx's switching time(how long my pulse is). Then, I can control 1 PA would work at any given time, and I would have all receiving antennas work (MIMO) if I put switch. Another Switch will turn on/off PA's gate voltage, a low frequency one because gate voltages are DC.

So, it makes 2 switches, one on the RF line, one at the gate voltage control.

Is that a correct approach?

- - - Updated - - -

Georgy.Moshkin said:
For 10GHz radar I would try 5GHz VCO + relatively cheap 6GHz switches + 5ghz doubling mixer. I have seen such approach used to switch between 10 or more antennas from a single VCO.
Click to expand...

Doubling mixer? Can you tell me about it? First time I hear such a thing.
 
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ktr said:
Doubling mixer? Can you tell me about it? First time I hear such a thing.
Click to expand...

Check out this patent: US20090015465
It uses LO, transmits LO*2 and receives RF which must be relatively close to LO*2.
I have seen similar doubling mixer used for 10GHz FMCW scanning antenna array with 6ghz switches, no separate transmit antenna. Each antenna had separate rat-race doubling type mixer, which produced 10GHz from 5GHz. Very interesting design.
 
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Initially you mentioned: "high power nature of PA".
The switch from Analog Devices supports only +24dBm of power (250mW).
 

vfone said:
Initially you mentioned: "high power nature of PA".
The switch from Analog Devices supports only +24dBm of power (250mW).
Click to expand...

Yes, at first I thought I would put switch after PA, then I realized that switch can not handle 1-2 W power, so I decided to use it before PA, where line power is around 10mW. I will use a secondary switch to alternate between gate voltages of PA's, so the one that wont be used wont dissipate unnecessary energy.

 

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