hec@holliselectronics.com

Engineering Services

Hollis Electronics Company LLC (HEC) contract engineering resources have been providing specialized product development and services for over 20 years. Our seasoned engineering team has designed and deployed equipment around the world with decades of non-stop operation. The primary areas of expertise are in spread spectrum, frequency hopping techniques and digital signal processing theory and implementation of complex real-time DSP algorithms in state-of-the-art processors. See section below for examples of scope and type of projects contracted.
Whether you need project support or a complete turnkey solution, HEC can provide the resources to get you from design specification to product roll-out.

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EXAMPLES OF CUSTOM PROJECTS
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4MIMO

A major telecommunications company contracted Hollis Electronics Company LLC (HEC) to design and build a 4MIMO system. The system accepts four 70 MHz IF Input signals and produces four 70 MHz IF Output signals. These signals are processed by the 4MIMO system such as to meet the specifications in the IEEE 802.11-03/940r4 document. This system is controlled via an Ethernet interface and operates from a (100-250) VAC power source. The input signals, connected via SMA connectors, have up to a 40 MHz +3 dB bandwidth. The 4MIMO system allows 2MIMO operation with certain software parameters set. The system allows an operator to choose one of the 6 models (A-F) described in the aforementioned IEEE specification along with selection of parameters defining the Transmit and Receive antenna arrays. The customer provided their own GUI and RF interface for their final product.

TDMA System Monitor/Measurement Unit (TSM-MU)

The TDMA System Monitor – Measurement Unit (TSM-MU) was designed and manufactured by Hollis Electronics Company LLC for use in Intelsat’s Time Division Multiple Access (TDMA) satellite link network. The TSM-MU is a network monitor, which is integrated within TDMA reference terminals and specific TDMA traffic terminals within the INTELSAT TDMA network.
The TSM-MU continuously monitors traffic and performed measurements on up to four (4) separate transponders with up to 100 carriers on each transponder. The following 6 measurements were taken for each carrier:

  • Eb/No + 0.1 dB
  • Amplitude Slope + 0.1 dB
  • Carrier Frequency Error + 1 KHz
  • Receive Signal Level + 0.1 dB
  • Satellite Output Level + 0.1 dB
  • Burst Status Based on Burst Energy

Measurements were reported for each carrier with results every 2 minutes. That is up to 2400 measurements in 2 minutes!

In addition, the following measurements are supported in a selectable Demand operation on a single transponder:

  • Reference Terminal TX EIRP
  • BMLA Amp & Group Delay measurements
  • Transponder Operating Point
  • Frequency and Time Input Control

Each Demand measurement operates asynchronously to the routine measurements.

The TSM-MU is controlled through an Ethernet interface with the SCP (System Control Processor).

All this was performed on 2000 technology.

Bit Error Rate Test Set (BERTS)

The Hollis Electronics Bit Error Rate Test Set (BERTS) was built to satisfy the following criteria:

  • Low Cost
  • Easy to set-up and operate
  • Automatically Synchronizes
  • Measurement Intervals of 1, 10, 100 Seconds or Continuous
  • Measures extremely small Bit Error Rates (less than 1×10-8)

HEC’s BERTS is a low cost solution for measuring the Bit Error Rate of 120 Mbps TDMA Modems. A bench top stand-alone test instrument, the BERTS is capable of measuring bit error rates from 0.1 to 1 x 10-8. Measurement intervals are 1, 10, 100 seconds or Count Mode. Using the Count Mode extremely small bit error rates (less than 1 x 10-8) can be measured or measurements involving a long time duration can be performed. The BERTS generates two burst data streams, P and Q, for determining the bit error rate. Synchronization is automatically performed without any operator input. Bit error rates for both the P and Q channels are measured simultaneously. All information is displayed on an easy-to-read front panel display. Easy to set-up and simple to operate the BERTS provides TDMA System Operators with the tool they need at a price they can afford. Although ideally suited for 120 Mbps TDMA modems, the BERTS is capable of measuring bit error rates on modems with data rates from 600 bits per second to 140 Mbps. The Hollis Electronics BERTS is your low cost solution for measuring the bit error rate of 120 Mbps TDMA modems.

SORF Flywheel

The SORF Flywheel was a revolutionary new product when developed by Hollis Electronics for INTELSAT to aid in the trouble shooting of TDMA systems during a system crash or loss of Start Of Receive Frame (SORF). During a system crash or loss of SORF, the HEC SORF Flywheel enabled a user to determine where in the TDMA frame an interference was occurring. The HEC SORF Flywheel uses Hollis Electronics proven Digital Signal Processing (DSP) Platform and Frame generation circuitry.

The HEC SORF Flywheel is a stand-alone test instrument which generates four TTL SORF signals which are synchronized to a TTL SORF input and a 10 MHz standard input. The SORF output maintains synchronization with the SORF input to within 100 ns. The HEC SORF Flywheel can be powered by 90 to 260 VAC. All inputs and outputs use BNC connectors except for the 25-pin D connector for the BMLA interface and the 9-pin D connector for the RS-232 port. The system is easy to use and informs the user of system status via a scrolling 4 character alpha-numeric LED display. The HEC SORF Flywheel has four modes of operation:

1. Search Mode - In this mode the system searches for the SORF pulse. Once the system obtains and synchronizes with the SORF pulse the HEC SORF Flywheel automatically enters into the Track Mode. The Search Mode is not user selectable, but automatically selected when the selector switch is in the Track Mode and the system has not yet synchronized with the SORF timing pulse. This mode is also entered automatically when the system returns after a loss of the SORF pulse.

2. Tracking Mode – In this mode the system maintains synchronization with the SORF input and using present and past timing data generates a drift rate and drift direction. This mode is selected by turning the selector switch to TRACK.

3. Flywheel Mode – In this mode the SORF Flywheel tracks the disconnected input SORF signal. This is accomplished by using internally generated timing and the average drift rate generated while the system was in the tracking mode. This mode is selected by turning the selector switch to FLYWHEEL or automatically when the SORF input signal is lost. This is the mode which is ideal for TDMA system trouble shooting. By using the output of the HEC SORF flywheel to trigger an oscilloscope on the TDMA frame the user can determine where in the TDMA frame an interference is occurring. When the HEC SORF Flywheel enters the “Flywheel Mode” the LED display scrolls the following message “Flywheeling (xxx min)”. Where xxx is the number of minutes the system has not detected a SORF pulse.

4. BMLA Mode – In this mode the SORF Flywheel generates a 2ms Frame RS-422 SORF and SOTF based upon the 10 MHz input. This mode of operation allows an operator to easily perform BMLA measurements without a satellite signal. This is very useful for BMLA training without going out over the link and for performing in station measurements. This mode is selected by positioning the selector switch to BMLA.

Additional Capability – When used with a PC the HEC SORF flywheel can be used as a burst negator or to gate out an empty time slot for Analog Spectrum Analyzer analysis. Hollis Electronics Company built the HEC SORF Flywheel as a stand-alone system but it also has the capability to be controlled by a PC. External control by a PC is via the external RS-232 port on the HEC SORF Flywheel. By using a PC for external control a user can set up four separate TTL timing signals locked to the TDMA frame. Each timing signal can have multiple pulses, each pulse having user selectable start and stop times with 50 ns resolution. These timing signals are locked to the incoming SORF to within + 100ns. The timing signal outputs, when combined with a TTL RF switch (available separately), can be used to form a burst negator.