Volume One, Chapter 27: No Way Through
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When he stepped out of Zhou Zhenhua’s office, even the air seemed a few degrees more spirited.
“Madmen. Both of you are madmen.” Shen Qingyun walked beside Du Yuze, muttering under his breath, though his own cheeks were flushed with excitement.
“Now we’re a whole group of madmen.” Du Yuze did not look back. His stride was swift and steady.
When they returned to the large workshop of the Advanced Technology Preliminary Research and Verification Center—a facility converted from an old warehouse—Master Li and several other veteran craftsmen were already waiting. They did not crowd around to ask about the result. They merely looked at Du Yuze and Shen Qingyun. Their silence spoke more powerfully than any question could have.
Du Yuze walked to the enormous mobile blackboard in the center of the workshop and picked up a fresh stick of chalk.
“Everyone.” His voice echoed through the cavernous workshop. “The factory director approved it.”
No one cheered.
Several of the veteran craftsmen merely clenched their fists in silence, their knuckles making faint cracking sounds. It was the sound of strength suppressed for far too long, finally finding an outlet.
“First step: avionics.” Du Yuze wrote the two words on the blackboard. “Our Dragon Sparrow is practically blind right now. I’m going to give it a pair of eyes that can see a thousand miles.”
Shen Qingyun took over, speaking rapidly, with the distinctive fervor of a technical specialist. “Our goal isn’t any of the range-finding radars currently in use. We’re going straight for a pulse-Doppler radar.”
“Pulse-Doppler?” Master Li frowned. He had spent his entire life working with machinery and was somewhat estranged from these new terms. “What’s so different about this thing from the ones we repair now?”
“Different?” Shen Qingyun gave a bitter smile. “Master Li, let me put it this way. With our current radar, looking at an aircraft in the sky is like looking with the naked eye. If the aircraft hides in the clouds or flies close to the ground, the radar can’t see it. To the radar, clouds and the ground are nothing but a chaotic mass of clutter.”
He picked up another piece of chalk and drew a simple diagram on the blackboard.
“A pulse-Doppler radar, on the other hand, can pluck a fast-moving aircraft out of all that clutter. It doesn’t look at the target itself; it looks at the target’s speed. As long as you’re moving, even if you’re hiding behind a mountain, it can ‘hear’ you.”
The workshop fell silent. The veteran craftsmen understood only half of what they were hearing, but they understood one thing perfectly—this was powerful technology.
“In theory, yes.” Shen Qingyun’s tone shifted, and his expression grew solemn. “But putting it into practice is incredibly difficult. Signal processing, clutter suppression, moving-target indication… Every one of them is a major obstacle. We have no references, no blueprints, and we don’t even know what components we’ll need. We’ll have to work everything out for ourselves.”
A younger technician could not help speaking up. “Chief Engineer Shen, I read some foreign journals a few days ago. They said the core of a pulse-Doppler radar is a high-speed signal processor and a traveling-wave tube. We… haven’t even seen those things before.”
“That’s why this is preliminary research.” Du Yuze’s voice was not loud, yet it overpowered every other discussion. “We’re here to build the things we’ve never seen. Chief Engineer Shen, take the lead. List the technical difficulties for the avionics team, and we’ll tackle them one by one.”
“All right.” Shen Qingyun answered, then led the others into the blueprint room beside the workshop.
In the days that followed, the entire center became a machine running at full speed. The lights in the blueprint room remained on throughout the night, while arguments frequently rang out from the workshop.
The formulas and sketches on the blackboard were replaced again and again, and discarded blueprints piled up in the wastepaper baskets like small hills.
Problems soon emerged.
“This won’t work. This approach is a dead end.” Shen Qingyun slammed a stack of papers covered in calculations onto the table. His whole body radiated frustration. He had barely slept in two days, and dark hollows had sunk beneath his eyes.
“What happened?” Du Yuze asked as he approached with a cup of hot tea.
“Clutter suppression.” Shen Qingyun clutched at his hair. “The filter we designed can theoretically eliminate most fixed-frequency ground clutter. But once we take into account trees swaying in the wind and waves on the sea—this ‘slow-moving clutter’—our radar goes completely blind. It can’t tell whether it’s looking at a tree or a low-speed helicopter.”
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He pointed to a complicated set of Fourier transform equations on the blackboard. “Look here. The signal and the clutter are completely superimposed in the frequency spectrum. Unless we can increase our processing power a hundredfold, there’s no way to calculate the result in real time. But where are we supposed to find a processor like that?”
The technicians around them fell silent as well. This was an impasse. They had exhausted every known filtering algorithm, and the result was always the same.
The atmosphere in the workshop, so exhilarated at first, began to grow heavy.
Du Yuze looked at the defeated Shen Qingyun, then at the string of equations on the blackboard that made even his own head spin. He knew they could not go on like this.
He returned to his small office and closed the door.
His head felt swollen, too. Technical terms and heated arguments churned through his mind. He closed his eyes.
System: Exchange “Essentials of the Fundamental Principles of Pulse-Doppler Radar.” Cost: 150 points.
A cool stream of data poured into his mind. Du Yuze did not become a radar expert, but several of the most fundamental concepts and possible solutions instantly became clear to him. He knew what questions to ask.
He pushed open the door and once again walked over to Shen Qingyun, who looked as though his soul had left his body.
“Old Shen.” He pointed at the blackboard. “Let me ask a layman’s question. Don’t laugh at me.”
“Go ahead.” Shen Qingyun sounded listless.
“Why do we have to confront all this clutter head-on? If it can’t be separated, can’t we make it change on its own?”
“What do you mean?” Shen Qingyun did not understand.
“Look. Our radar pulses are transmitted at a fixed frequency, right?” Du Yuze traced a waveform in the air with his finger. “We transmit one ‘beep’ and wait for it to come back. What if this time we transmit a ‘beep,’ next time a ‘boop,’ and the time after that a ‘beep-boop’? If we probe using different frequencies or repetition periods, wouldn’t the echoes from the same target differ under each kind of detection?”
Shen Qingyun froze. It was as if something had struck him.
“You mean… changing the pulse repetition frequency?” he murmured. “Using nonfixed, staggered pulse repetition frequencies?”
“I don’t know what it’s called.” Du Yuze spread his hands. “I just figure that if one key can’t open the lock, we should try a few different keys.”
“Staggered pulse repetition frequencies…” Shen Qingyun’s breathing quickened. He snatched the chalk from Du Yuze’s hand and rushed to the blackboard, erasing all the previous equations.
“If we alternate between high and low pulse repetition frequencies… then the velocity ambiguity generated under the first frequency can be resolved using the second—and vice versa! That way, we won’t need to filter the clutter directly. We can use an algorithm to calculate the target’s true velocity!”
His chalk flew across the blackboard as entirely new formulas and logic diagrams appeared line by line.
“We don’t need a processor with a hundred times the computing power! We only need to change the transmission logic, then use our existing processor to complete the calculations! My God… my God!”
Shen Qingyun suddenly stopped writing. He turned around and stared fixedly at Du Yuze.
“How did you come up with this idea?”
“I was just making things up.” Du Yuze brushed the chalk dust from his hands. “The nonsense of a layman, that’s all.”
Shen Qingyun said nothing. He simply stared at Du Yuze, as though trying to discover a flower growing from his face. After a long while, he nodded heavily, suppressing all his questions, then turned back to the new calculations.
The entire technical team was set alight by this completely new approach.
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The atmosphere of despair vanished, replaced by an even more frenzied dedication.
Three days later, an entirely new technical proposal was completed.
At the proposal review meeting, Shen Qingyun stood before the blackboard and explained in detail the advantages and feasibility of the staggered pulse repetition frequency system.
“…Therefore, in theory, this approach is viable.” After Shen Qingyun concluded, thunderous applause erupted throughout the conference room.
“Excellent! Chief Engineer Shen, shall we begin work on the hardware prototype immediately?” a young technician asked excitedly.
“Yes, the hardware.” Some of Shen Qingyun’s excitement faded. He picked up a checklist. “To implement this design, we first need a highly stable crystal oscillator and a programmable digital waveform generator. Most importantly, we need a high-performance semiconductor substrate to manufacture our core processing chip.”
He paused, then spoke each word clearly.
“According to my calculations, to handle this level of data throughput, we need at least… high-purity gallium arsenide wafers.”
“Gallium arsenide?”
The term was like a basin of ice water, instantly extinguishing all the enthusiasm in the conference room.
The air froze.
Master Li remained silent for a long time before finally speaking in a hoarse voice. “Chief Engineer Shen, I’ve only ever seen pictures of that stuff in foreign magazines. I hear it costs more than gold, and that the entire country can’t produce a usable piece. Is that true?”
Another veteran engineer responsible for materials also looked troubled. “The best material in our factory’s warehouse is high-purity silicon. Gallium arsenide… I’ve heard Laboratory Twelve has a few samples, brought back from abroad through extraordinary means. They’re barely the size of a fingernail, and treated like priceless treasures. Where are we supposed to get wafers?”
The faces that had been filled with hope only moments earlier fell one after another.
They were like a group of swordsmiths who, after enduring every imaginable hardship, had finally drawn up the design for a peerless sword—only to discover at the last moment that they possessed neither the coal to light the furnace nor the iron with which to forge the blade.
The immense joy brought by their theoretical breakthrough was smashed to pieces against the harsh gap in their industrial foundation.
A deathly silence filled the conference room.
Du Yuze said nothing. He listened quietly, watching each person’s reaction.
Only after everyone had finished speaking did he rise.
He walked over to Shen Qingyun, picked up the checklist bearing the words “gallium arsenide,” folded it, and slipped it into his jacket pocket.
“The avionics team will continue refining the algorithms. Take all the theoretical work as far as it can possibly go.”
He swept his gaze around the room.
“I’ll solve the materials problem.”
With that, he turned and walked out of the conference room.
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