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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CMX – Cartesian Feedback Loop Transmitter – CML Microcircuits
If the loop is set up degrees out of phase the loop will oscillate and will generally produce a maximum level carrier. Included are forward and feedback paths; local oscillator circuitry including loop phase control; an instability detector and uncommitted op-amps for input signal conditioning.
As phase error increases, the instability detector will show a worsening level of out-band energy. Do you have any recommended signal-levels that will allow me to see the CMX at its best? Using a Cartesian transmitter in TDMA systems can be challenging when supporting multiple modulation formats.
The error signal produced by the instability detector should be accessed for a particular design and an appropriate threshold set. The data will appear in the grayed-out data box. Note that a different loop-filter might be required for the kHz and kHz channels.
The modulation accuracy of a CMX transmit is determined by the down-converter feedback path. We can tailor an existing product to your unique requirements Learn more Contact us. Technical Portal No additional information available. If you continue to use this site we will assume that you are happy with it. What can I do to ensure a stable carrier leakage when I enable the RF detector? A simple guide to help users get started evaluating the EV Three scripts for evaluating performance of a multi-mode modem using the DE The degradation is due to the gain-expansion caused by the linearity correction for the non-ideal PA.
If a design supports dynamic loop phase calibration then an instability detector event normally triggers loop re-calibration. Typical changes are variations in antenna VSWR and thermal effects. 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. The recommended way to avoid this is to power-down the CMX down-converter before powering down the PA. If the loop becomes unstable due to phase inaccuracies the feedback loop will tend to spill energy out-of band.
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.
Such effects are unlikely to cause a phase shift as large as degrees. Are there any particular aspects of power-up or down sequence of the EV that I should be aware of? It is important to read the included readme. Can you help explain how the instability detector on the CMX operates and how it can be used? 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.
This process will continue as the PA output ramps down, with the up converter output and PA input signal level continuously increasing. 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.
The output power will decrease once the PA is powered down, and this results in a lower signal level fed back into the CMX These scripts can be easily modified to support other Block Types. 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. EV high resolution schematics and component overlay.
CMX998 – Cartesian Feedback Loop Transmitter
A worst-case value of —30dB is guaranteed. 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. The effect is shown in Table 1 dahasheet.
The PA device is not protected and enabling this device without the load may irreparably dame the device. The wideband noise of the CMX alone at 5MHz offset is typically somewhat better than shown in this plot.
The CMX includes gain adjustment to make threshold setting easier. 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.