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SDR Demonstrator for Linear Radio Systems



  • Direct Conversion Receiver
  • Cartesian Loop Transmitter
  • 1W Power Amplifier
  • VCO and Fractional-N PLL
  • Operation from 452MHz to 467MHz
  • Nominal +3.6V Supply


  • SDR Wireless Data Modem Demonstration
  • Direct Conversion Receiver (CMX994) and Linear Cartesian Loop Transmitter (CMX998)
  • Demonstration platform for the CMX7164 Multi-mode Modem

Supply Requirement:

  • Nominal 3.6V dc regulated power supply

The DE9941 is a small demonstration platform for the CMX994 Direct Conversion Receiver, the CMX998 Cartesian Loop Transmitter and the CMX7164 Multi-mode Wireless Data Modem.

The DE9941 can be used to demonstrate Tx and Rx performance with QAM modulation, FSK and GMSK type modulation. Together with the PE0003 host controller, a full transceiver can be demonstrated using a Function Image and control scripts.

The DE9941 provides a Fractional-N PLL and VCO plus associated circuits to provide local oscillator signals for the CMX994/E and CMX998. The PE0003, together with the control scripts, gives the user the ability to program the RF synthesiser to the correct operating frequencies.

The design also includes a 1W power amplifier, harmonic filter and Tx/Rx switch. The RF performance is designed to be compliant with EN 302 561 and EN 300 113, all the circuits are provided with power-down capability to allow standby functionality.

Note: User Manual Rev2 is for the use with older boards containing CMX994 and CMX998 combination and User Manual Rev3 is for use with new boards containing CMX994E and CMX998 combination.

PCB Image

DE9941: Demonstration Board for CMX994, CMX998 and CMX7164

Design Support Information


DE9941 FAQ

Q: How do I control the CMX994 or CMX998 on the DE9941 board?

A: The DE9941 includes the CMX7164 Multi-Mode Modem, the CMX998 Cartesian Feedback Loop Transmitter, and the CMX994 Direct Conversion Receiver.  When the PE0003 Ev Kit Interface Card is used as the host controller for DE9941, the PE0003 communicates with the CMX998 and CMX994 through the CMX7164’s SPI Thru-Port.  The CMX7164 SPI Thru-Port is beneficial because it allows control of peripherals with fewer uC pins and PCB traces.

There are three CMX7164 internal registers that are key for this discussion:

- $62, SPI Thru-Port Control

- $63, SPI Thru-Port Write

- $78, SPI Thru-Port Read

CMX7164 register $78 comes into play when you need to read an external device register.  CMX7164 register $63 contains the value to be written to an external device register, and CMX7164 register $62 defines important C-BUS/SPI parameters such as:

- Which Chip Select will be used for the transaction

- If the transaction will be read or write

- Number of bytes to be written to the target device

- CMX7164 IRQ behavior when the write is completed

- The address of the target device

For example, let’s say we need to write 0xFC to CMX998 register $02 using the CMX7164 SPI Thru-Port.  Pseudocode of the required SPI Thru-Port transaction would look like this:

- Host writes 0xFC to CMX7164 register $63

- Host then writes 0x4102 to CMX7164 register $62 (SSOUT1, Interrupt when the C-BUS Thru-Port Control/Write registers are free, write transaction, 1 data byte, register address $02)

To do this same transaction in the PE0003 graphical user interface (GUI):

- Select “C-BUS Control” tab and observe the “Write a Register” area

- Ensure “16 bit” is checked

- Enter 63 for “Register Address”, enter FC for “Register Data”, and then click “Write”

- Enter 62 for “Register Address”, enter 4102 for “Register Data”, and then click “Write”

Here is a pseudocode example of a read transaction using the SPI Thru-Port.  In this example, CMX998 “readback” register $F2 will be read out:

- Host writes $71F2 to $62 (SSOUT1, Interrupt when read or write operation triggered by this Thru-Port command is completed on the SPI port, read transaction, 1 data byte, register address $F2)

- Host waits for IRQ

- Host reads CMX7164 register $78 to obtain the data

To do this same transaction in the PE0003 GUI:

- Select “C-BUS Control” tab and observe the “Write a Register” area

- Ensure “16 bit” is checked

- Enter 62 for “Register Address”, enter 71F2 for “Register Data”, then click “Write”

- Move over to the “Read a Register” area

- Enter 78 for “Register Address”, then click “Read”.  The data will appear in the grayed-out data box.

Control of the CMX994 Direct Conversion Receiver is performed in the same manner.

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