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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Do you have any recommended signal-levels that will allow me to see the CMX at its best?

As phase error increases, the instability detector will show a worsening level of out-band energy. This issue can datasneet 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.

Included are forward and feedback paths; local oscillator circuitry including loop phase control; an instability detector and uncommitted op-amps for input signal conditioning.

CMX998 – Cartesian Feedback Loop Transmitter

Are there any particular aspects of power-up or down sequence of the EV that I should be aware of? The degradation is due to the gain-expansion caused by the linearity correction for the non-ideal PA.

I am looking to develop a high quality non-constant envelope transmitter and am looking to improve the linearity of my current design. If instability is detected then normal procedure is to power down the transmitter. This App Note discusses these issues using the DE in a worked example. This can over-drive the PA which may over-current and fail. The CMX includes gain adjustment to make threshold setting easier.

Using a Cartesian transmitter in TDMA systems can be challenging when supporting multiple modulation formats. A simple guide to help users get started evaluating the EV Both Single Ended and Differential modes are shown. These scripts can be easily modified to support other Block Types.


The measurements include the effects of the non-ideal PA that is corrected by the Cartesian loop. The PA device is not protected and enabling this device without the load may irreparably dame the device. The modulation accuracy of a CMX transmit is determined by the down-converter feedback path. 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.

The error signal produced by the instability detector should be accessed for a particular design and an appropriate threshold set. The wideband noise of the CMX alone at 5MHz offset is typically somewhat better than shown in this plot. The effect is shown in Table 1 below:. Such effects are unlikely to cause a phase shift as large as degrees. EV high resolution schematics and component overlay. The data will appear in the grayed-out data box. The output power will decrease once the PA is powered down, and this results in a lower signal level fed back into the CMX In the form of a populated PCB, this flexible platform enables users, using a control interface, to configure and evaluate the CMX to various applications and frequency bands.

A simple guide to help users get started evaluating the DE There is a preferred method of powering down the EV to also avoid damage to the power amplifier PA. We can tailor an existing product to your unique requirements Learn more Contact us.

As this is effectively a stable oscillating condition the instability detector will not detect this operating state. 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.

CMX – Cartesian Feedback Loop Transmitter – CML Microcircuits

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. For clarification, the relevant change is: Technical Portal No additional information available. It is datasheft to read the included readme.


The CMX instability detector cannot detect lead or datasjeet error as it works on a simple baseband signal. These scripts require the following evaluation boards: 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. If you continue to use this site we will assume that you are happy with it.

Can you help explain how the instability detector on the CMX operates and how it can be used? Datasheets CMX Datasheet rev If the loop is set datasheey degrees out of phase the loop will oscillate and will generally produce a maximum level carrier.

What can I do to ensure a stable carrier leakage when I enable the RF detector? If the loop cms998 unstable due to phase inaccuracies the feedback loop will tend to spill energy out-of band. Note that a different loop-filter might be required for the kHz and kHz channels.

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. This effect can be avoided by using BVREF to bias the input signal rather than using a resistor network tied to 3.

Typical changes are variations in antenna VSWR and thermal effects. Three scripts for evaluating performance of a multi-mode modem using the DE The effect is shown in Table 1 below: The instability detector is designed to detect minor phase variations and resultant instability following initial phase correction.

We use cookies to ensure that we give you the best experience on our website. If a design supports dynamic loop phase datasheft then an instability detector event normally triggers loop re-calibration.