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 Datasheet(PDF) – CML Microcircuits
These scripts can be easily modified to support other Block Types. The output power will decrease once the PA is powered down, and this results in a lower signal level fed back into the CMX We cm998 tailor an existing product to your unique requirements Learn more Contact us. These scripts require the following evaluation boards: As this is effectively a stable oscillating condition the instability detector will not detect this operating state.
A simple guide to help users get started evaluating the DE The error signal produced by the ckx998 detector should be accessed for a particular design and an appropriate threshold set. A worst-case value of —30dB is guaranteed.
Both Single Ended and Differential modes are shown. The CMX includes gain adjustment to make threshold setting easier.
CMX998 – Cartesian Feedback Loop Transmitter
If the loop becomes unstable due to phase inaccuracies the feedback loop will tend to spill energy out-of band. 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. What can I do to ensure a stable carrier leakage when I enable the RF detector? For clarification, the relevant change is: Do you have any recommended signal-levels that will allow me to see the CMX at cms998 best?
Datasheets CMX Datasheet rev Are there any particular aspects of power-up or down sequence of the EV that I should be aware of? Can you help explain how the instability detector on the CMX operates and how it can be used? 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.
If instability is detected then normal procedure is to power down the transmitter. This means a common shift is applied to DC offset correction signal and modulator reference. Such effects are unlikely to cause a phase shift as large as degrees. There is a preferred method of powering down the EV to also avoid damage to the power amplifier PA. EV high resolution schematics and component overlay. The PA device is not protected and enabling this device without the load may irreparably dame the device.
If the loop is set up degrees out of phase the loop will oscillate and will generally dwtasheet a maximum level carrier.
The CMX instability detector cannot detect lead or lag error as it works on a simple baseband signal. Note that a different loop-filter might be required for the kHz and kHz channels.
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 you continue to use this site we will assume that you are happy with it.
The instability detector found on the CMX is a relatively simple mechanism that measures the level datasheft out-of band energy of the feedback loop. I am looking to develop a high quality non-constant envelope transmitter and am looking to improve the linearity of my current design.
CMX – Cartesian Feedback Loop Transmitter – CML Microcircuits
Three scripts for evaluating performance of a multi-mode modem using the DE Included are forward and feedback paths; local oscillator circuitry including loop phase control; an instability detector and uncommitted op-amps for input signal conditioning. In the form of a populated Cmxx998, this flexible platform enables users, using a control interface, to configure and evaluate the CMX to various applications and frequency bands.
The effect is shown in Table 1 below:. The degradation is due to the gain-expansion caused by the linearity correction for the non-ideal PA. A simple guide cms998 help users get started evaluating the EV 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.
The modulation accuracy of a CMX transmit is determined by the down-converter feedback path. This can over-drive the PA which may over-current and fail.
The instability detector is designed to detect minor phase variations and resultant instability following initial phase correction. As phase error increases, the instability detector will show a worsening level of out-band energy. This effect can be avoided by using BVREF to bias the input signal rather than using a resistor network tied to 3.