Skip to main content
Electrical Engineering

Return to Question

deleted 18 characters in body
Source Link
Evan
Evan
  • 359
  • 1
  • 7

Suppose I'm designing a transmitter which has an LO and an IQ mixer. I would like to shift the LO down by 100 MHz or so, so I can mix it with the IQ mixer output so I can monitor the IQ mixer balance and LO leakage. The main issue is that the LO might be anywhere from 4 to 8 GHz. My worry is that if I use a single sideband mixer to generate the LO-100 MHz, the parasitic upper sideband (LO+100 MHz) will also mix with the IQ mixer output, and so I will never be able to tune the IQ mixer better than the SSB mixer suppresses it's upper sideband. I've determined this is the case if you assume a mixer is a perfect multiplier.

However, I understand however that mixers aren't linear... if the LO+100 MHz sideband is 25 dB lower than LO-100 MHz, will it contribute at all?

Second, if I have this signal which consists of LO-100 MHz and a much smaller LO+100 Mhz, how do I knock out LO+100 MHz if LO spans an octave?

Finally, is there a good way to do what I seem to be trying to do? I just wanna get the output of the IQ mixer from the microwave range back down to the 0-1 GHz range so I can monitor it easily. I wonder if a sampling detector is a good way to go.

Suppose I'm designing a transmitter which has an LO and an IQ mixer. I would like to shift the LO down by 100 MHz or so, so I can mix it with the IQ mixer output so I can monitor the IQ mixer balance and LO leakage. The main issue is that the LO might be anywhere from 4 to 8 GHz. My worry is that if I use a single sideband mixer to generate the LO-100 MHz, the parasitic upper sideband (LO+100 MHz) will also mix with the IQ mixer output, and so I will never be able to tune the IQ mixer better than the SSB mixer suppresses it's upper sideband. I've determined this is the case if you assume a mixer is a perfect multiplier.

However, I understand however that mixers aren't linear... if the LO+100 MHz sideband is 25 dB lower than LO-100 MHz, will it contribute at all?

Second, if I have this signal which consists of LO-100 MHz and a much smaller LO+100 Mhz, how do I knock out LO+100 MHz if LO spans an octave?

Finally, is there a good way to do what I seem to be trying to do? I just wanna get the output of the IQ mixer from the microwave range back down to the 0-1 GHz range so I can monitor it easily. I wonder if a sampling detector is a good way to go.

Suppose I'm designing a transmitter which has an LO and an IQ mixer. I would like to shift the LO down by 100 MHz or so, so I can mix it with the IQ mixer output so I can monitor the IQ mixer balance and LO leakage. The main issue is that the LO might be anywhere from 4 to 8 GHz. My worry is that if I use a single sideband mixer to generate the LO-100 MHz, the upper sideband (LO+100 MHz) will also mix with the IQ mixer output, and so I will never be able to tune the IQ mixer better than the SSB mixer suppresses it's upper sideband. I've determined this is the case if you assume a mixer is a perfect multiplier.

However, I understand that mixers aren't linear... if the LO+100 MHz sideband is 25 dB lower than LO-100 MHz, will it contribute at all?

Second, if I have this signal which consists of LO-100 MHz and a much smaller LO+100 Mhz, how do I knock out LO+100 MHz if LO spans an octave?

Finally, is there a good way to do what I seem to be trying to do? I just wanna get the output of the IQ mixer from the microwave range back down to the 0-1 GHz range so I can monitor it easily. I wonder if a sampling detector is a good way to go.

Tweeted twitter.com/StackElectronix/status/889026347355516928
Source Link
Evan
Evan
  • 359
  • 1
  • 7

How do I reuse the LO when designing a loopback receiver?

Suppose I'm designing a transmitter which has an LO and an IQ mixer. I would like to shift the LO down by 100 MHz or so, so I can mix it with the IQ mixer output so I can monitor the IQ mixer balance and LO leakage. The main issue is that the LO might be anywhere from 4 to 8 GHz. My worry is that if I use a single sideband mixer to generate the LO-100 MHz, the parasitic upper sideband (LO+100 MHz) will also mix with the IQ mixer output, and so I will never be able to tune the IQ mixer better than the SSB mixer suppresses it's upper sideband. I've determined this is the case if you assume a mixer is a perfect multiplier.

However, I understand however that mixers aren't linear... if the LO+100 MHz sideband is 25 dB lower than LO-100 MHz, will it contribute at all?

Second, if I have this signal which consists of LO-100 MHz and a much smaller LO+100 Mhz, how do I knock out LO+100 MHz if LO spans an octave?

Finally, is there a good way to do what I seem to be trying to do? I just wanna get the output of the IQ mixer from the microwave range back down to the 0-1 GHz range so I can monitor it easily. I wonder if a sampling detector is a good way to go.