エリカ・ジャオ - RFおよびマイクロ波コンポーネント

Demystifying Mixer Spurs in RF Downconversion: Frequency Planning and ADS Simulation Guide

Feeling overwhelmed by spurious signals in your RF designs? You’re not alone. The unpredictable nature of spurs can ruin performance and cause major headaches for any engineer. You can demystify intermodulation by understanding it’s a predictable result of mixer nonlinearity1. Use mixer spurious charts and simulation software like ADS to select frequencies that avoid spurs. Also, keep the mixer’s input power well within its linear range to minimize them. This sounds simple, but let’s break it down. I remember a project early in my career where a mysterious spur nearly derailed our entire timeline. It was a frustrating experience, but it taught me a valuable lesson: understanding the fundamentals is […]

Stop Self-Jamming on a RF Up/Down converter: Advanced PCB Layout and Shielding for RF Isolation

Poor isolation in your up/downconverter can ruin your system’s performance. This leads to self-jamming and unreliable links1. But a systematic approach can help you achieve deep isolation levels. Excellent isolation in a broadband RF up/downconverter is achieved by combining three key techniques. First, use dense ground via fences and multi-cavity shielding for physical isolation. Second, design a clean power delivery network with separate supplies. Finally, verify the entire design with EM simulation. When I first started designing integrated transceiver systems, I learned a tough lesson about isolation. It’s not just a single parameter you can tweak; it’s the result of a total design philosophy. If your transmit and receive channels […]

Satcom Basics: Why Ka-Band Upconverter is Crucial for Satellite Transmit

Ever wondered how massive amounts of satellite data reach us clearly? It’s not as simple as pointing a dish, as signal loss and distortion are huge challenges. Up/down conversion is crucial for satellite communication. It lets us use smaller antennas by transmitting at high frequencies. It also steps down the received frequency, preventing signal distortion and enabling accurate data recovery by the system’s electronics. This process might sound technical, but it’s the backbone of reliable satellite links. I remember a new salesperson asking me this exact question. Understanding it is key to appreciating the engineering behind every clear satellite call or data stream. This process is not just a single […]

LNB Design Secrets: Maximize Antenna Gain and Lower Noise Figure via HFSS

You have an LNB, and it has a small antenna inside. So why do you still need that big satellite dish? The two must work together to capture a usable signal. An LNB cannot function effectively for satellite reception without a dish. The dish’s large surface area is essential for capturing the extremely weak satellite signal and concentrating its power onto the LNB’s feedhorn. Without the dish, the LNB’s tiny internal antenna would not gather enough signal to work. I asked my mentor this exact question years ago. He explained that the dish and the LNB are a team, and you can’t have one without the other. Understanding their distinct […]

PA and LNA: Why you cann’t use a RF Amplifier replace LNA in Receiver Design

Using a power amp as a preamp seems logical but can cripple your system. This choice will drown weak signals in noise, making them impossible to recover. No, you should never use a power amplifier as a preamp. A power amp has a very high noise figure1, designed for output power, not sensitivity. Using one would add so much noise that it would overwhelm the weak incoming signal, destroying the receiver’s performance. It’s a question I’ve heard before, even from my own sales team. They’ll ask, “It’s an amplifier, and the gain is there, so why not?” I always tell them the same thing: it would be a disaster. The […]

Why RF Wideband Amplifier Flat Gain Droop: The Secrets of R-L-C Network

Designing a multiband SSPA with a perfectly flat gain curve feels like an impossible task. The physics just seems to be working against you. But it is achievable. To design a multiband Solid State Power Amplifier (SSPA) with flat gain, you must combine three techniques1. First, use a negative feedback circuit for stability. Second, add an R-L-C input matching network to flatten the gain. Third, use wideband load-pull to control harmonics and maintain efficiency. I’ve been designing RF components for over a decade, and this challenge comes up on almost every wideband project. The temptation is to focus on just one area, like output power, and hope for the best. […]

How Does Digital Pre-Distortion Achieve Closer Power Amplifier Saturation to for Better Linearity?

Getting maximum power from your SSPA without creating signal distortion is a constant challenge. This trade-off between power and linearity often forces unwanted compromises in system design and efficiency. The best way to optimize an SSPA is by using Digital Pre-Distortion (DPD).1 DPD digitally models the amplifier’s non-linear behavior, including memory effects2, and creates an inverse distortion signal. This pre-corrected signal, when amplified, results in a clean, linear output even near saturation. I’ve spent years in the lab pushing amplifiers to their limits. The goal is always the same: get as much clean power as possible. You need high linearity for today’s complex modulation schemes, but you also need high […]

How to Accurately Determine RF Power Amplifier Drain Efficiency with Power Back-off?

You trust the datasheet for amplifier efficiency. But your real-world SSPA design overheats and performs poorly. I will show you how to measure the real efficiency and avoid these problems. To accurately determine RF power amplifier efficiency, you must go beyond the datasheet. Use a high-precision digital multimeter and a calibrated power meter. De-embed your test setup using S2P files. And most importantly, test with realistic modulated signals using a 3-5dB power back-off. Datasheet numbers are a great starting point, but they are far from the whole story. They represent an ideal world that rarely exists in a final product. Understanding the gap between the datasheet and reality is the […]

Why GaN SSPA Ruin Your High Linearity: Taming Trapping Effects via DPD and Power Back-off

Choosing between GaN and GaAs SSPAs is tricky. GaN’s smaller size is appealing, but its non-linearity can secretly tank your system performance1. Let’s find the right solution. Choose GaN for higher power density and a smaller footprint, but be prepared for its non-linearity. To maintain signal integrity, you must implement Digital Pre-Distortion (DPD) and a 3-5 dB power back-off. For applications demanding high linearity without DPD, GaAs remains a solid choice.2 Performance Dimension GaAs SSPA GaN SSPA Power Density Low (0.5 ~ 1 W/mm) Extremely High (3 ~ 10 W/mm or higher) Linearity Superior (Inherent good linearity) Good (Requires digital pre-distortion DPD) Breakdown Voltage Moderate (~ 10 ~ 20 V) […]

SSPA vs. TWTA: Why SSPA Wins the High-Linearity and EVM Battle

Choosing the right power amplifier is a critical decision. You need raw power, but a distorted signal can ruin your entire system. The right choice balances both needs perfectly. Solid-State Power Amplifiers (SSPAs) ensure linearity by using advanced semiconductor materials like Gallium Nitride (GaN) which have a wider linear operating range1. They also employ active linearization techniques, such as digital predistortion, to mathematically cancel out non-linear behavior2 before the signal is even amplified. I remember a tense discussion I had on a Ku-band satellite project. A very experienced senior engineer was set on using a traditional Traveling Wave Tube Amplifier (TWTA). He argued for its incredible 60% efficiency3, and on […]

投稿者: エリカ・ジャオ

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