CC2500 output impedance and range

Thank you very much for your help!

I am a newbie in RF networking, so I really appreciate it.

Anyway, finally I boost the CC2500 output using a CC2591 kit.

I would ask you other questions: unfortunately there isn't the reference design of CC2591 and so i don't know the mechanical dimensions CC2591EMK board connector (see

http://focus.ti.com/docs/toolsw/folders/print/cc2591emk.html).

i guess that the pitch is 2.54 mm but i am not sure about this. Can you help me?

Furthermore I have reading something about SimpliciTI, it should resolve collision problem...do you confirm?

Thank you in advance.

Regards,

Oscar

Oscar,

Trying to implement a polarization or time diversity is really separate questions.    Polaraization diversity is handled much like you have shown in the diagram.  One antenna is orthoganal to the second antenna.   In a pure line of site this means the radiation pattern will be stronger in two directions.   The spacing is a minimum of 1/4 wavelength between antennas for maximum effect.    Yes the second boards ground plane effects the results so one should program the small card and run it on battery to remove it fromt he bottom card to get a more conclusive measurment.

Time diversity generally has two antennas spaced 1/4 wavelength and in the same directioin.  This is primarily done for robustness.   If you have a closed room that has an area with a dead area the small time delay due to the antenna spacing will most likely cover the area.     Of course moving the antennas around could also change a dead area.   

Running two antennas in parallel generally means a combiner is used to send the signals to the antennas of equal delays.  You cannot connect the two antennas in parallel without some intermediate device.    This will change the impedance matching and loading of the radio's output power.  

In the case of time domain an RF fast switch can be used to switch from one antenna to the next.  

The above idea is done in many applicaitons.  If you take two antennas of the same orientation your RSSI signal strength in open field is maximum as long as height is observed.   If you then rotate one 90 degrees the signal will decrease 3 dB or more. 

In a close area (room)  you depending upon scattering to communicate.  Therefore it is hard to say if a diversity implementation provides better coverage but it definitely makes a system more robust if the second antennas orientation is not normal to the transmit antenna.

So in summary,  I would not use a metallic enclousre for control.   If you can identify a weak to dead area combination then test these combinations as shown.   The whip antenna is made to work outside of an enclosure.     If you are considering a plastic enclosure and PCB antenna then you would repeat the test for that prototype.  We can guide you to an equivalent performaning PCB antenna. 

Regards,

Rea Schmid

Hi Gregorio,

sorry for the delay of my answer.

I attach the configuration i have used for our 4 km radio link. Hope this helps.

Regards.

Oscar

#if TI_CC_RF_FREQ == 2400                          // 2.4GHz
// Product = CC2500
// Crystal accuracy = 40 ppm
// X-tal frequency = 26 MHz
// RF output power = 0 dBm
// RX filterbandwidth = 540.000000 kHz
// Deviation = 0.000000
// Return state:  Return to RX state upon leaving either TX or RX
// Datarate = 9.6 kbps
// Modulation = (7) MSK
// Manchester enable = (0) Manchester disabled
// RF Frequency = 2483.000000 MHz
// Channel spacing = 199.950000 kHz
// Channel number = 0
// Optimization = Sensitivity
// Sync mode = (3) 30/32 sync word bits detected
// Format of RX/TX data = (0) Normal mode, use FIFOs for RX and TX
// CRC operation = (1) CRC calculation in TX and CRC check in RX enabled
// Forward Error Correction = (0) FEC disabled
// Length configuration = (1) Variable length packets, packet length configured by the first received byte after sync word.
// Packetlength = 61
// Preamble count = (2)  4 bytes
// Append status = 1
// Address check = (0) No address check
// FIFO autoflush = 0
// Device address = 0
// GDO0 signal selection = ( 6) Asserts when sync word has been sent / received, and de-asserts at the end of the packet
// GDO2 signal selection = (0) Associated to the RX FIFO: Asserts when RX FIFO is filled at or above the RX FIFO threshold. De-asserts when RX
//                            FIFO is drained below the same threshold.
// FIFO_THR = 14
// 5 bytes in TX FIFO (59 available spaces)
// 60 bytes in the RX FIFO

void writeRFSettings(void)
{
    // Write register settings
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_IOCFG2,0x29);  // GDO2 output pin config.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_IOCFG0,0x06);  // GDO0 output pin config.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_PKTLEN,0x3D);  // Packet length.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_PKTCTRL1,0x05);  // Packet automation control. + test address
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_PKTCTRL0,0x05);  // Packet automation control.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_ADDR,0x06);  // Device address.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_CHANNR,0x00); // Channel number.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSCTRL1,0x07); // Freq synthesizer control.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSCTRL0,0x00); // Freq synthesizer control.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FREQ2,0x5F); // Freq control word, high byte
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FREQ1,0x80); // Freq control word, mid byte.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FREQ0,0x00); // Freq control word, low byte.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MDMCFG4,0x88); // Modem configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MDMCFG3,0x84); // Modem configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MDMCFG2,0x73); // Modem configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MDMCFG1,0x22); // Modem configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MDMCFG0,0xF8); // Modem configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_DEVIATN,0x00); // Modem dev (when FSK mod en)
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MCSM1,0x1F); //MainRadio Cntrl State Machine
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_MCSM0,0x18); //MainRadio Cntrl State Machine
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FOCCFG,0x1D); // Freq Offset Compens. Config
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_BSCFG,0x1C); //  Bit synchronization config.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_AGCCTRL2,0x07); // AGC control.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_AGCCTRL1,0x00); // AGC control.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_AGCCTRL0,0xB2); // AGC control.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FREND1,0xB6); // Front end RX configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FREND0,0x10); // Front end RX configuration.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSCAL3,0xEA); // Frequency synthesizer cal.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSCAL2,0x0A); // Frequency synthesizer cal.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSCAL1,0x00); // Frequency synthesizer cal.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSCAL0,0x11); // Frequency synthesizer cal.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FSTEST,0x59); // Frequency synthesizer cal.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_TEST2,0x88); // Various test settings.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_TEST1,0x31); // Various test settings.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_TEST0,0x0B);  // Various test settings.
    delay(10);
    TI_CC_SPIWriteReg(TI_CCxxx0_FIFOTHR,0x0E);  // FIFO TRESHOLD = 60 bytes (RX)
}



// PATABLE (-16 dBm output power)
extern char paTable[] = {0x55};
extern char paTableLen = 1;

#endif