projekte:3cmbeacon:start
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projekte:3cmbeacon:start [2023/01/06 18:26] – thasti | projekte:3cmbeacon:start [2023/01/23 19:42] (aktuell) – [Architecture] thasti | ||
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====== Integrated 10 GHz Beacon Transmitter ====== | ====== Integrated 10 GHz Beacon Transmitter ====== | ||
- | After the decline in use of ATV in Germany, an idea of building a 3 cm beacon at [[https:// | + | After the decline in use of ATV in Germany, an idea of building a 3 cm beacon at [[https:// |
The goal of this project was building a 10 GHz beacon transmitter suitable for long-term unsupervised operation from commercially available integrated circuits. To make full use of the transmit power constraints in Germany, an output power of 1-2 W was targeted. Support for contemporary digital beacon transmission modes such as [[https:// | The goal of this project was building a 10 GHz beacon transmitter suitable for long-term unsupervised operation from commercially available integrated circuits. To make full use of the transmit power constraints in Germany, an output power of 1-2 W was targeted. Support for contemporary digital beacon transmission modes such as [[https:// | ||
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**Quick Pointers:** | **Quick Pointers:** | ||
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A simple block diagram of the beacon transmitter is shown in the figure below. | A simple block diagram of the beacon transmitter is shown in the figure below. | ||
- | ~TODO~ | + | {{ : |
The beacon transmitter accepts an external 100 MHz reference clock provided by a GNSS-disciplined oscillator. GNSS stabilization is the de-facto standard for beacons on 10 GHz and above due to their narrow spacing and small bandwidth. It also enables receiving stations to use the beacon as a frequency reference for aligning their own equipment. | The beacon transmitter accepts an external 100 MHz reference clock provided by a GNSS-disciplined oscillator. GNSS stabilization is the de-facto standard for beacons on 10 GHz and above due to their narrow spacing and small bandwidth. It also enables receiving stations to use the beacon as a frequency reference for aligning their own equipment. | ||
- | A Silicon Labs Si5342 is used as a crystal-driven reference PLL, which takes care of reference clock jitter cleaning and modulation generation. The high-resolution fractional divider allows synthesizing sub-Hz frequency steps of the output RF carrier, which are required for modern modulation formats. Due to the architecture of the synthesizer, | + | {{ : |
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+ | A Silicon Labs Si5342 is used as a crystal-driven reference PLL, which takes care of reference clock jitter cleaning and modulation generation. The high-resolution fractional divider allows synthesizing sub-Hz frequency steps of the output RF carrier, which are required for modern modulation formats. Due to the architecture of the synthesizer, | ||
The HMC952A also has a built-in output RF power detector, which is read out by an on-board controller with integrated ADC. This simplifies the design since no external coupler is required to monitor forward power. The MCU further takes care of reading out the various DC power sensors on the board (to monitor voltages and currents of the SMPSes) and runs the sequencing of the beacon transmitter itself. It (optionally) communicates with a remote device through RS-422 (differential signalling). | The HMC952A also has a built-in output RF power detector, which is read out by an on-board controller with integrated ADC. This simplifies the design since no external coupler is required to monitor forward power. The MCU further takes care of reading out the various DC power sensors on the board (to monitor voltages and currents of the SMPSes) and runs the sequencing of the beacon transmitter itself. It (optionally) communicates with a remote device through RS-422 (differential signalling). | ||
===== RF Design ===== | ===== RF Design ===== | ||
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One of the key design features that helps with driving down cost is working with a commercial four-layer FR4 stackup. These have become ubiquitous and cheap to use, so one supplier (JLCPCB from China) was chosen and their PCB process characterized for RF performance. Two dedicated RF test coupons were designed: Based on the results of long simulations, | One of the key design features that helps with driving down cost is working with a commercial four-layer FR4 stackup. These have become ubiquitous and cheap to use, so one supplier (JLCPCB from China) was chosen and their PCB process characterized for RF performance. Two dedicated RF test coupons were designed: Based on the results of long simulations, | ||
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===== Testing ===== | ===== Testing ===== | ||
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Before going into continuous operation at DB0HDF, the transmitter hard- and software were extensively tested on the lab workbench. The output power, phase noise and spurious performance was first evaluated, with a particular emphasis on varying input voltage conditions. Long supply wires could possibly cause regulator instabilities in final installations, | Before going into continuous operation at DB0HDF, the transmitter hard- and software were extensively tested on the lab workbench. The output power, phase noise and spurious performance was first evaluated, with a particular emphasis on varying input voltage conditions. Long supply wires could possibly cause regulator instabilities in final installations, | ||
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===== Transmitter Integration at DB0HDF ===== | ===== Transmitter Integration at DB0HDF ===== | ||
With the PCB battle-tested, | With the PCB battle-tested, | ||
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projekte/3cmbeacon/start.1673029565.txt.gz · Zuletzt geändert: 2023/01/06 18:26 von thasti