March 25, 2022

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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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. This effect can be avoided by using BVREF to bias the input signal rather than using a resistor network tied to 3. The instability detector found on the CMX is a relatively simple mechanism that measures the level of out-of band energy of the feedback dztasheet.

CMX998 – Cartesian Feedback Loop Transmitter

For clarification, the relevant change is: The modulation accuracy of a CMX transmit is determined by the down-converter feedback path. A simple guide to help users get started evaluating the EV The effect is shown in Table 1 below: 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.

Such effects are unlikely to cause a phase shift as large as degrees.


If a design supports dynamic loop phase calibration then an instability detector event normally triggers loop re-calibration. In the form of a populated PCB, this flexible platform cmx9998 users, using a control interface, to configure and evaluate the CMX to various applications and frequency bands. EV high resolution schematics and component overlay. Technical Portal No additional information available.

Typical changes are variations in antenna VSWR and thermal effects. Three scripts for evaluating performance of a multi-mode modem using the DE As phase error increases, the instability detector will show a worsening level of out-band energy.

The data will appear in the grayed-out data box. 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:. If the loop is set up degrees out of phase the loop dtaasheet oscillate and will generally produce a maximum level carrier.

Both Single Ended and Differential modes are shown.

This can over-drive the PA which may over-current and fail. Are there any particular aspects of power-up or down sequence of the EV that I should be aware of? Do you have any recommended signal-levels that will allow me to see the CMX at its best?

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 CMX instability detector cannot detect lead or lag error as it datashet on a simple baseband signal.

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Using a Cartesian transmitter in TDMA systems can be challenging when supporting multiple modulation formats.

As this is effectively a stable oscillating condition the instability detector will not detect this operating state. There is a preferred method of powering down the EV to also avoid damage to the datwsheet amplifier PA. The output power will decrease once the PA is powered datashset, and this results in a lower signal level fed back into the CMX The PA device is not protected and enabling this device dstasheet the load may irreparably dame the device.

Note that a different loop-filter might be required for the kHz and kHz channels.

We use cookies to ensure that we give you the best experience on our website. There are three CMX internal registers that are datasheey for this discussion: This App Note discusses these issues using the DE in a worked example.

CMX Datasheet(PDF) – CML Microcircuits

We can tailor an existing product to datashee unique requirements Learn more Contact us. The CMX includes gain adjustment to make threshold setting easier. A worst-case value of —30dB is guaranteed. If instability is detected then normal procedure is to power down the transmitter.

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

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