International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A composite PCM/FM+FM/FM system combines the spectral efficiency of the analog system with the accuracy of a PCM system when needed for specific sensors and allows the direct transmission of binary computer words if necessary. A PCM/FM+FM/FM system combines the bit sequence with the modulated subcarriers at baseband and the resultant modulates the carrier. In the design of the composite system it is of importance to determine the impact of the subcarriers on the bit error rate of the bit sequence and to determine the degradation of the output signal-to-noise ratio of the subcarrier channels caused by the bit sequence.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A typical PCM/FM system is designed for a peak to peak carrier deviation of 0.7 times the bit rate of the PCM data. This value of PCM data deviation has been shown to be optimum for both PCM/FM [1] and PCM/FM+FM/FM [2] systems. However, the optimum deviation of the carrier by the FM subcarrier for a PCM/FM+FM/FM system is dependent upon the specific subcarrier type and required subcarrier signal to noise ratio at the receiver output. This paper introduces a simple method to calculate the optimum deviation of the carrier by FM subcarriers for a PCM/FM+FM/FM system. The method developed is used to calculate the optimum value of subcarrier deviation for two sample PCM/FM+FM/FM systems when IRIG constant bandwidth channels are used as FM subcarriers. The calculated optimum values of FM subcarrier deviation of the carrier, subcarrier mod index, are utilized in a companion paper to study the performance of PCM/FM+FM/FM systems [3]. The work presented herein can be extended to calculate the optimum deviation of the carrier by FM subcarriers for any PCM/FM+FM/FM system.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Today’s telemetry environment is becoming increasingly digital. Highly reliable and relatively inexpensive digital recorders readily available, and most telemetry facilities are migrating away from the older analog recorders which are difficult to calibrate and expensive to maintain. Unfortunately, most site managers find they still have one or more “legacy” signals (such as FM-FM, PAM, and pre-detect PCM) that still require analog recording. To exclusively use digital recorders the TM site must integrate some device to convert the analog signals to digital format before recording. Until recently, the TM site managers had very few options short of building custom equipment to convert and capture the legacy signals. One solution available from Racal (for their Storeplex digital recorder) is to purchase their Analog Record/Play Signal Module. Unfortunately, their module uses a 16-bit Sigma-Delta converter and has a maximum bandwidth of 45.5 KHz, which is woefully inadequate for many analog signals. Other manufacturers offer similar solutions with similar bandwidth restrictions. Another solution is to purchase a multiplexor “front-end” which is capable of mixing multiple signal types (both digital and analog) on to the recorder’s serial-digital data stream. This option can provide higher analog bandwidths, but represents a significant investment (greater than $100K and often more than the recorder itself). This paper discusses the conceptualization, design, and performance of a unit to fill the gap between the low-bandwidth analog channel module and the high-end signal multiplexors. We will discuss how high-speed field-programmable gate arrays (FPGAs) can be configured to provide a low-cost interface between the digital recorder and the analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) to capture and playback the analog signals. Our design focuses on achieving the maximum possible bandwidth for each analog signal while ensuring that IRIG-A or IRIG-B timecode are recorded simultaneously (so the analog signals can be later synchronized with their digital counterparts). We have found that such a solution permits multiple analog signals from 400 KHz up to 3 MHz to be easily and inexpensively recorded on the current generation of digital recorders. Our conclusions show that such a device can permit most telemetry sites to transition completely to more reliable, cheaper, and easier-to-maintain digital recorders.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The US Air Force is required to protect the lives of individuals and property in areas potentially hazardous as a result of launch vehicle failures occurring from Vandenberg AFB, California. This paper describes the application of modern telemetry processing equipment to the Range Safety function.