WORK Microwave's Handheld Satcom Test Source

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TEST REPORT Test Signal Generator The Reference Determines the Quality In order to be able to measure complex analog systems, calibrate test equipment or test high-frequency converters, you need to have a test signal generator. This device generates a signal at a specific frequency and power level where its precision is extremely critical since it is to be used as a reference signal. WORK Microwave offers exactly this kind of test signal generator; it can produce signals from 50-180 MHz and also from 950-2150 MHz. The Handheld Satcom Test Source is shipped in a suitable protective package in which you‘ll find a red aluminum case, two USB cables (A-B) and a power cable. When you open up the red aluminum case you‘ll find in its padding the signal generator, the power supply, a USB stick, the user manual and a certificate of conformance certifying that the Handheld Satcom Test Source complies with the listed parameters. It is even noted on the certificate that any documentation that was used in the manufacture of this signal generator can be made available upon request. This kind of documentation results in traceability; all measured values can be traced as far back as the manufacturer WORK Microwave thereby precluding any discussions on any measurement results. Page 15 of the user manual explains all of the functions of the test signal generator in a detailed yet easy-tounderstand format. The installation of the unit is quite simple. You only need to run the executable file from the USB storage device. An actual installation is not necessary. Naturally, you can also copy the program to the hard drive. The manufacturer was also thoughtful enough to include a copy of the user manual in the USB storage device. Installing drivers is not necessary since Windows XP, Windows Vista and Windows 7 will recognize the instrument as an HID (Human Interface Device) and automatically incorporate it into the operating system. The Handheld Satcom Test Source has an elongated housing fabricated out of aluminum. There‘s no doubt that this is a robust test instrument that is further protected on the front and back by hardened plastic. On the front panel you‘ll find the 11-12/2013 WORK Microwave Handheld Satcom Test Source Allows for precise and certified high-frequency measurements www.TELE-audiovision.com/13/11/work-microwave ■ TELE-audiovision Editor Vitor in action. It's not nearly as difficult as it looks. 98 TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 11-12/2013 — www.TELE-audiovision.com www.TELE-audiovision.com — 11-12/2013 — TELE-audiovision International — 全球发行量最大的数字电视杂志 99
1 power supply input (12V- 24V), two USB type B inputs and three status LEDs. The first LED indicates the instruments operational status (OK or error), the second LED shows the charging status of the rechargeable battery and the third one shows the system status. The two USB inputs have different functions. USB1 serves as an additional source of power and also provides for the data communication with the PC. USB2 is exclusively used to provide power to the unit if for some reason the external power supply can‘t be used. The Handheld Satcom Test Source runs from an internal rechargeable battery that lets you use it without having to keep it connected to a power source. This is not surprising considering this is a portable signal generator. It‘s also interesting that this instrument can be operated from a PC or laptop via the USB ports and since a single USB port cannot provide enough power, the Handheld Satcom Test Source can be connected to both USB ports. Very clever! On the back of the test source is the on/off switch. There‘s also a BNC jack that provides a 10 MHz reference output signal as well as an SMA jack that provides the signal generated by the test source. The signal generator also provides a DC voltage on this output which is indicated by an additional LED. Control of the unit is taken care of by a Windows program which also controls a sweep function. Measurement of High-frequency Converters The primary use of the Handheld Satcom Test Source is the measurement of various parameters of high-frequency (RF) converters. These RF converters, also available from WORK Microwave, convert the signal to be transmitted from its original frequency to a higher output frequency. Since these high-frequency signals could not be routed through a satellite uplink station between all the different devices (modulators, multiplexers, etc.) using coaxial cable without incurring some signal loss, waveguides or very expensive cable are needed. Instead, a different path is used. The signal is routed and processed in the 50 to 180 MHz range or the 950 to 2150 MHz range until it‘s ready to be sent to the uplink section. Only then, in this final step, is the highfrequency converter used to upconvert the signal into the satellite uplink frequency range. Obviously, this high-frequency converter cannot introduce any errors that might interfere with a neighboring transponder or even go as far as interfering with normal satellite operation. This kind of interference is known as intermodulation. Intermodulation occurs when two signals are modulated on two frequencies that are very close to each other, causing additional signal peaks to appear on the sides of the two main frequencies. (see Figure 1). To check and see how much a high-frequency converter can minimize this Intermodulation effect, you would need two RF test sources so that you can modulate two nearby signal levels with known parameters. These two signal levels would then be routed to the high-frequency converters. Using a spectrum analyzer, you could then generate an picture of this intermodulation. It‘s exactly for this reason 2 1: Intermodulation occurs directly next to the wanted signal - see the red labled signals 2: The compression point is defined to be at exactly 1 dB. From here on the signal quality deviates from the ideal characteristic. that WORK Microwave incorporated two independent synthesizers in the Handheld Satcom Test Source so that now you can use just a single RF signal source to perform this measurement. Obviously this greatly reduces the costs involved in acquiring these RF test sources since now you‘d only need one of these instruments instead of two. At the same time the test setup itself is simplified since only a single cable and the upconverter need to be connected. Another parameter that is measured when it comes to high-frequency converters is the so-called 1 dB compression point. This measurement is used to check the non-linear response of the high-frequency converter. Here the amplitude of the input signal is slowly increased until the signal distortion due to non-linearity deviates exactly 1 dB from the ideal characteristic curve (see Figure 2). The red line shows the ideal output curve. Above a specific input level the highfrequency converter begins to distort the signal such that a lower signal level is available at the output - hence the name “Compression“: a lower signal level is at the output; the signal has been compressed. To be able to compare different devices, you measure the input power level that results in a 1 dB compression at the output. Here the WORK Microwave Test Source proves itself with the ability to set the test signal to any frequency from 50 to 180 MHz and 950 to 2150 MHz with a power level from 100 TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 11-12/2013 — www.TELE-audiovision.com
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WORK Microwave's Handheld Satcom Test Source

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