As a state-of-the-art design for an integrated CFBL, the CMX improves the . connecting circuitry, details of which are given in the product datasheet. The CMX is an integrated solution for a Cartesian Feedback Loop based linear transmitter. Acting as a direct conversion quadrature mixer from I and Q to RF. CMX datasheet, CMX circuit, CMX data sheet: CMLMICRO – The Product Data Amendment series of documents,alldatasheet, datasheet, Datasheet.

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If instability is detected then normal procedure is to power down the transmitter. Technical Portal No additional information available.

This process will continue as the PA mcx998 ramps down, datazheet the up converter output and PA input signal level continuously increasing. EV high resolution schematics and component overlay. As phase error increases, the instability detector will show a worsening level of out-band energy. There are three CMX internal registers that are key for this discussion: If the loop becomes unstable due to phase inaccuracies the feedback loop will tend to spill energy out-of band.

We can tailor an existing product to your unique requirements Learn more Contact us. Both Single Ended and Differential modes are shown. Included are forward and feedback paths; local oscillator circuitry including loop phase control; an instability detector and uncommitted op-amps for input signal conditioning.

Can you help daatsheet how the instability detector on the CMX operates and how it can be used?

CMX998 – Cartesian Feedback Loop Transmitter

Such effects are unlikely to cause a phase shift as large as degrees. Three scripts for evaluating performance of a multi-mode modem using the DE This can over-drive the PA which may over-current and fail. Datasheets CMX Datasheet rev The CMX instability detector cannot detect lead or lag error as it works on a simple baseband signal. We use cookies to ensure that we give you the best experience on our website.


Do you have any recommended signal-levels that will allow me to see the CMX at its best? For clarification, the relevant change is: I am looking to develop a high quality non-constant envelope transmitter and am looking to improve the linearity of my current design. The error amplifier input signal levels will diverge, so the error signal to the up converter will increase, and the signal level to the PA input will also increase.

Are there any particular aspects of power-up or down sequence of the EV that I should be aware of?

CMX – Cartesian Feedback Loop Transmitter – CML Microcircuits

A simple guide to help users get started evaluating the EV Typical changes are variations in antenna VSWR and thermal effects. There is nothing specific to be aware of when powering the EV up for the first time, however it is very important to ensure that a 50ohm load is attached to J9 before enabling the power amplifier.

The results from this improved configuration are also shown in Table 1 and although a small degradation is still observed the carrier leakage is still dBc, which is considered more than adequate for most applications. The instability detector found on the CMX is a relatively simple mechanism that measures the level of out-of band energy of the feedback loop.

CMX Datasheet(PDF) – CML Microcircuits

The recommended way to avoid this is to power-down the CMX down-converter before powering down the PA.

It is important to read the included readme.

A simple guide to help users get started evaluating the DE These scripts require the dataxheet evaluation boards: The measurements include the effects of the non-ideal PA that is corrected by the Cartesian loop. If a design supports dynamic loop phase calibration then an instability detector event normally triggers loop re-calibration.

What can I do to ensure a stable carrier leakage when I enable datasheet RF detector? The modulation accuracy of a CMX transmit is determined by the down-converter feedback path. The instability detector comprises a high-pass filter followed by a peak-detector circuit and this combination indicates the presence of this high frequency energy.


This issue can be greatly reduced if the alternative configuration for applying a bias voltage to the input signal is used, as documented in EV Datasheet version 5 and above. If you continue to use this site we will assume that you are happy with it. These scripts can be easily modified to support other Block Types.

The effect is shown in Table 1 below: The effect is shown in Table 1 c,x998. The wideband noise of the CMX alone at 5MHz offset is typically somewhat better than shown in this plot. This effect can be avoided by using BVREF to bias the input signal rather than using a resistor network tied to 3. The CMX includes gain adjustment to make threshold setting easier. The error signal produced by the instability detector should be accessed for a datawheet design and an appropriate threshold set.

The data will appear in the grayed-out data datqsheet. This App Note discusses these issues using the DE in c,x998 worked example. The degradation is due to the gain-expansion caused by the linearity correction for the non-ideal PA.

The output power will decrease once the PA is powered down, and this results in a lower signal level fed back into the CMX If the loop is set up degrees out of phase the loop will oscillate and will generally produce a maximum datssheet carrier. As this is effectively a stable oscillating condition the instability detector will not detect this operating state.