UPCONVERSION MIXER THESIS

Without phase compensation the possible improvements can be severely limited, depending on how close the phase balance is to start with. In MLIQ mixers in chip form, the LO phase can be trimmed by applying ceramic, absorber, or other microwave tuning elements familiar to the microwave black magicians out there to the LO quad hybrid in a certain way while observing the sideband suppression. In the chart above sideband suppression is increased from about 19 dB to 23 dB by adding an offset voltage, and then again to 50 dB or so by combining phase manipulation with the DC offset. There are myriad methods to perform this digital compensation, with different cost tradeoffs. Here we are performing a single sideband upconversion where the desired sideband signal is corrupted by LO feedthrough, the suppressed sideband, and spurious products. As you can see the application of a DC voltage will degrade the conversion loss without changing the phase, allowing you to easily vary the amplitude balance of one side of an IQ mixer.

This is the ultimate in IQ compensation techniques. If we control the LO but not the IF, then an amplitude error is more serious, since it causes the C 3 constant to not cancel. If the IQ mixer is integrated, however, it is more difficult. In the chart above sideband suppression is increased from about 19 dB to 23 dB by adding an offset voltage, and then again to 50 dB or so by combining phase manipulation with the DC offset. For more information consult the usually very detailed datasheet of a dual channel high speed ADC. There are myriad methods to perform this digital compensation, with different cost tradeoffs.

The problem, however, mixee that this cannot be done in a convenient way. Now that we have established that IF or LO amplitude and phase errors can be compensated, let us discuss the various ways in which this can be accomplished. If the IQ mixer is integrated, however, it is more difficult.

upconversion mixer thesis

It may be possible to upconverison that any error in A or B can be compensated with phase terms, but we will not show that here. If the IQ mixer is built as a bolt-together solution, then the phase can be manipulated by varying line lengths or with a phase trimmer.

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The most basic approach for sideband suppression is to simply receive both I and Q channels, and estimate the distortion coming from the Q channel in the I channel, and subtract your received estimate of the Q channel from the I channel. As you can see the application of a DC voltage will degrade the conversion loss without changing the phase, allowing you to easily vary the amplitude balance of one side of an IQ mixer.

This makes them readily accessible for IF amplitude and phase manipulation. The phase control in these ADCs may be performed on the internal oscillator.

upconversion mixer thesis

In this blog post we will examine various ways to compensate for the fact that these structures are built with real components with imperfect phase and amplitude balance. There are easily references for this topic, including several books, and most are full of dense math and advanced digital signal processing.

Since some of this is proprietary I will leave it at that and say that you should contact support at Marki for more information. The phase can also be manipulated in digital implementations. This is the ultimate in IQ compensation techniques. Here we are performing a single sideband upconversion where the desired sideband signal is corrupted by LO feedthrough, the suppressed sideband, and spurious products.

For more information consult the usually very detailed datasheet of a dual channel high speed ADC. In MLIQ mixers in chip form, the LO phase can be trimmed by applying ceramic, absorber, or other microwave tuning elements familiar to the microwave black magicians out there to the LO quad hybrid in a certain way while observing the sideband suppression.

This is the big daddy when it comes to analog IQ compensation methods. First we need to answer the question, can IQ imbalance be compensated? The penalty, as you can see, is an increase in the LO feedthrough from dBm to -3 dBm, overpowering even the desired sideband.

In the chart above sideband suppression is increased from about 19 dB to 23 dB by adding an offset voltage, and then again to 50 dB or so by combining phase manipulation with the DC offset. This technique upconverson be used without penalty for image reject mixers, however, since the LO is out of band of the IF output. Unfortunately there is a tradeoff.

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5 Ways to Compensate for Passive IQ Mixer Imbalance

The output is given by the sum of the top two terms, where the first is the desired sideband low side in this case and the second term is the undesired or suppressed sideband. The IQ mixer is the backbone of modern communications architectures, as well as advanced vector signal analyzers for electronic warfare and test and measurement receivers.

There are myriad methods to perform this digital compensation, with different cost tradeoffs. Specifically, two of the diodes will turn thesi at a higher voltage, and two of them will turn off at a higher voltage.

5 Ways to Compensate for Passive IQ Mixer Imbalance – Marki Microwave RF & Microwave

If we control the LO but not the IF, then an amplitude error is more serious, since it causes the C 3 constant to not cancel. Amplitude and offset correction registers are generally built into DACs that are designed for communications, arbitrary waveform generation, and software defined radio applications.

The latter term goes to 0 with perfect error terms, while the former goes to 1. This has the profound implication that by correcting the phase of the LO signal driving the receiver side mixer, we can compensate for any imperfections in the transmitting side mixer.

Without phase compensation the possible improvements can be severely limited, depending on how close the phase balance is to start with. As we have seen with fiber optic links, wireless links, and any other modern data standard, it is easier and cheaper to use millions of transistors to digitally compensate for a bad signal than to create the analog channel necessary for a good signal. The backbone of the IQ mixer is vectorial cancellation based on phase an amplitude balance.

upconversion mixer thesis

In this blog post we will not address compensation for spurs, although this is possible.