Anritsu MS4647B
Understanding the Anritsu MS4647B (VectorStar)
In the world of extreme semiconductor metrology and millimeter-wave radar research, standard lab equipment hits a physical wall around 40 GHz. To characterize advanced 5G millimeter-wave chips, automotive radar (77 GHz), and next-generation 6G backhaul systems, engineers require a machine of terrifying precision. The Anritsu MS4647B is that machine. As a flagship member of the VectorStar family, it is a 70 GHz Vector Network Analyzer (VNA) built for absolute, uncompromising accuracy.
What makes the MS4647B legendary is its massive frequency span. Older high-frequency VNAs were "banded"—meaning they could measure 50 to 75 GHz, but if you wanted to measure 2 GHz, you had to physically disconnect the device and move it to a different machine. The MS4647B can perform a continuous, unbanded sweep from an incredibly low 70 kHz all the way to 70 GHz in a single click. This is critical for characterizing high-speed digital lines that have DC-like low-frequency content but massive high-frequency harmonics.
Unrivaled Dynamic Range
To measure the isolation of a massive radar filter, the VNA must be able to blast a loud signal into the front, and listen for a microscopic whisper coming out the back. The MS4647B boasts an industry-leading dynamic range of > 140 dB. It achieves this by using a proprietary Non-Linear Transmission Line (NLTL) sampler bridge instead of traditional mixer diodes, dropping the noise floor to near-thermal limits.
Dynamic Range (dB) = Pmax_source - Pnoise_floor
Because the MS4647B can output a massive +14 dBm of clean power at 70 GHz, and its NLTL receivers have an incredibly low noise floor of -130 dBm (at 10 Hz IF Bandwidth), it achieves a staggering 144 dB of dynamic range, allowing it to see isolation leaks that other VNAs simply register as dead noise.
Comparison
| High-End VNA Model | Technology Base | Max Continuous Freq | Primary Advantage |
|---|---|---|---|
| Keysight PNA-X (N5247B) | Mixer-Based Superheterodyne | 67 GHz | Massive software suite, built-in nonlinear X-parameters |
| Anritsu MS4647B (VectorStar) | NLTL Sampler Bridge | 70 GHz (Expandable to 1.1 THz) | Best-in-class low-frequency start (70 kHz) and trace noise |
| Rohde & Schwarz ZNA67 | Mixer-Based | 67 GHz | Exceptional touch UI and dual local oscillators |
Frequently Asked Questions
How can the MS4647B measure up to 1.1 THz if it's only a 70 GHz machine?
By using 'Millimeter-Wave Extender Modules'. Anritsu engineers designed external, heavy metal blocks that sit directly on the probe station next to the silicon wafer. The MS4647B sends a clean 20 GHz signal into the block, and the block uses massive, non-linear multiplier diodes to multiply that frequency up to 1,100 GHz (1.1 THz). The raw 70 GHz VNA acts as the highly precise IF (Intermediate Frequency) backend engine for these extreme extender modules.
What is 'Trace Noise' and why does Anritsu brag about it?
If you measure a perfect 50-ohm cable, the S21 line on the screen should be perfectly flat. In reality, thermal noise causes the line to look 'fuzzy' and jittery. This fuzz is Trace Noise. Because the MS4647B uses NLTL samplers, it suffers from drastically less phase jitter than a mixer-based VNA. A lower trace noise means an engineer can zoom in to see a 0.01 dB ripple in a filter without the measurement being drowned out by screen fuzz.
Why is the 70 kHz starting frequency such a big deal?
Most 67 GHz VNAs cannot start sweeping until 10 MHz. If you are characterizing an amplifier for a massive broadband optical communication link, that amplifier must pass the extremely low-frequency DC bias pulses (in the kHz range) all the way up to the 60 GHz data harmonics. If your VNA can't measure the kHz range, you are physically blind to how the amplifier behaves under low-frequency thermal memory effects. The MS4647B covers it all.