SSS Online

Preview / Read the Current Issue of SSS

Volume 5 - Number 1 -- Spring 1997

Updated 8/6/97


Part 2


New Products


The Development Kit is an extension to the Sirius Communications PMCM Development Board

It allows to continuously monitor in real-time up to 6 simultaneous receiver signals, such as correlation values, the receiver phase error, the AGC value, the carrier recovery and the timing recovery. A complex constellation diagram can also be shown. These measurements allow to quickly evaluate the performance of a receiver, and to tune the transmitter and/or receiver parameters. The PMCM Development Board allows to program a huge range of modem parameters, and to derive Bit Error Rate (BER) figures. The effect of typical parameters of the Development Board can immediately be quantified using the PMCM Development Kit. For instance, the step response of the PLL for carrier recovery can be visualised as a function of the PLL gain and PLL bandwidth.

The PMCM Development Kit consists of 3 parts:

1. Development Kit Monitor software

The Development Kit Monitor software can simultaneously handle 6 measurements out of a set of 32 receiver signals. This set can be freely assigned by the user, and the configuration can be done from the Development Board terminal window. Any of the 6 measurement channels can be plotted on a time axis, or in a complex plane, or both at the same time. The following 2 examples the system under test uses QPSK with different codes of length 15 on the I and the Q branches. This is also called QPN (Quadriphase Pseudo-Noise).

At the left of the screen, the 2 upper function plots show snapshots of the correlation data of I and Q channels with each code, as a function of time. The third functional plot shows the chip frequency offset at the receiver (D_RX_FCHIP) and the frequency offset (D_RX_CARR) of the receiver carrier, as a function of time.

At the right of the screen, the constellation plot of the demodulated QPN signal is shown.

Lock-in behaviour of carrier tracking PLL


As a result of a carrier frequency step at the transmitter side, the receiver carrier frequency starts to produce a beatnote, that slows down in frequency until lock is reached. During pull-in, correlation values are unusable, and become stable again when lock is reached. The receiver chip frequency offset (D_RX_CARR) remains unaffected. The transient behaviour results in constallation dots outside the main spots.

Receiver response to step in transmit chip frequency.


As a result of a chip frequency step at the transmitter side, the receiver chip frequency (D_RX_FCHIP) offset starts evolving towards a new stable value. The receiver carrier tracking loop (see D_RX_CARR) goes through a transient behaviour, due to the coupling with the chip frequency tracking loop, and then reaches again its original value.

2. PMCM software extension

The PMCM software running on the TMS320C31 is extented with a separate monitor process, that runs on the frequency of one of the internal timers of the TMS. This monitor process selects 6 out of 32 measurements and sends them to the PC via the ISA board.This set of 32 monitor signals is updated by the PMCM receiver process every symbol.

To match the slower speed of the PC, the selected measurements are automatically downsampled by the monitor process. However, independent of the speed of the PC running the Development Kit Software, the measurement set is always kept consistent. The faster the PC, the higher the resolution of the measurements plotted on the screen of the PC.

The TMS monitor process is provided as source code, and is open to the developer, who can add his own signals to observe via the Development Kit, up to a maximum of 32 signals.

3. ISA interface board

The PMCM Development Board communicates to the PC via an ISA interface board. The 16-bit ISA Board provides a 16-bit handshaked output for the Development Kit software. It can also be used as a 16-bit parallel input/output port to the PMCM Development Board.



This CDMA/Spread Spectrum Development Board (second generation) provides a configuration with the PMCM IC and the TMS 320-C31 DSP. This allows full flexibility in modulation schemes, data rates, spreading codes, tracking loops, synchronization algorithms, acquisition strategy, etc.


  • Stand-Alone operation or interfacing with terminal
  • Serial PC interface
  • Programmable IF in both transmitter and receiver
  • Programmable sample rate in transmitter and receiver
  • Programmable symbol rate
  • Custom spreading codes and code lengths
  • Various modulation schemes
  • Correlation data dump for visualization of constellation plots
  • Flexible tracking, demodulation and data formatting
  • Performance measurements such as real-time BER calculation
  • Comprehensive tutorial included


To ask for the data sheets, contact Kristoffel Mulier at:

Sirius Communications NV
Wingepark 51
B-3110 Rotselaar

tel: +32 16 44 44 02
fax: + 32 16 44 54 81
Please Contact us today!

In October 2000, this website and the copyright to all editions of Spread Spectrum Scene Online was purchased by SSS Online, Inc., and is operated by Pegasus Technologies. For more of the best information on RF, Spread Spectrum and wireless, press one of the buttons below:

Pastissues Index E-zine Menu SSS-Mag Home Pegasus Tech