Test and Measurement Equipment Instrument Selection Informational

How do I select a signal generator for testing a receiver at millimeter wave frequencies?

Q: Can I use a sub-6 GHz generator with an upconverter?

Yes. A common lower-cost approach: use a mid-range VSG (6-20 GHz) with an external frequency upconverter (mixer + LO) to reach mmWave. Advantages: lower instrument cost ($30,000-60,000 total). Disadvantages: higher EVM floor (the upconverter adds phase noise and distortion), additional complexity (two instruments), and limited output power. For R&D prototyping: this is a viable approach. For production or conformance testing: a direct mmWave VSG is preferred.

Q: What about 77 GHz automotive radar testing?

Automotive radar at 77 GHz requires: a signal generator at 76-81 GHz (W-band). Options: VDI or OML frequency extenders driven by a 20-40 GHz generator, or dedicated automotive radar signal emulators (Keysight E8740A, R&S AREG100A). The radar test also requires: FMCW chirp generation (specific to automotive radar), target simulation (delay, Doppler shift, RCS), and antenna pattern characterization (OTA in anechoic chamber).

Q: How important is phase noise at mmWave?

Phase noise is often the limiting factor for EVM at mmWave. At 28 GHz: the generator phase noise is approximately 9 dB worse than at 10 GHz (20 log(28/10)). For 5G NR 256QAM: the required EVM is 3.5%. The phase noise contribution to EVM must be < 1% to leave margin for other impairments. This requires integrated phase noise < 1° RMS (100 kHz to carrier/2). Only high-end generators achieve this at 28+ GHz. For 64QAM testing (EVM 8%): the phase noise requirement is 6 dB more relaxed, and mid-range instruments suffice.

How do I select a signal generator for testing a receiver at millimeter wave frequencies? Testing mmWave receivers (5G FR2, automotive radar, satellite) requires a signal generator with specific capabilities beyond the standard sub-6 GHz requirements: (1) Frequency range: 5G FR2 testing: 24.25-52.6 GHz minimum. Must cover all relevant bands (n257: 26.5-29.5, n258: 24.25-27.5, n260: 37-40, n261: 27.5-28.35). Automotive radar: 76-81 GHz (W-band). Satellite Ka-band: 26.5-40 GHz. 6G research: 100-300 GHz. Above 50-67 GHz: signal generators use frequency multiplier/upconverter modules. Major options: direct generation to 67 GHz (Keysight M9384B VXG, R&S SMW200A), or external upconversion (VDI, OML frequency multiplier heads from lower-frequency generators). (2) Key specifications for mmWave: output power: +5 to +15 dBm (higher power is harder at mmWave; many generators produce only -10 to +5 dBm above 50 GHz). For sensitivity testing: need -100 dBm or lower (use external precision attenuators). Phase noise: critical for 5G FR2 EVM testing. 256QAM at FR2: requires integrated phase noise < 1° RMS over 100 kHz to 100 MHz offset. Generator phase noise at 28 GHz should be < -95 dBc/Hz at 10 kHz offset. Phase noise scales with frequency: a generator with -110 dBc/Hz at 10 GHz has approximately -101 dBc/Hz at 28 GHz (20 log ratio). Modulation bandwidth: 5G FR2: up to 400 MHz (for 100 MHz × 4 carrier aggregation). The generator must support > 400 MHz RF bandwidth with acceptable EVM. EVM floor: < 1.0% (-40 dB) for testing 256QAM receivers. High-end VSGs achieve 0.3-0.5% (-46 to -50 dB) at mmWave. (3) Connector/waveguide: below 50 GHz: 2.4 mm coaxial connector (DC-50 GHz). Below 67 GHz: 1.85 mm coaxial connector (DC-67 GHz). Above 67 GHz: waveguide flanges (WR-15, WR-10). Cable losses at mmWave: 2-5 dB/m at 28 GHz (use short, high-quality cables). (4) Major instruments: Keysight M9384B VXG: to 44 GHz (direct), modulated BW 2 GHz. Dual-channel for MIMO testing. Price: $100,000-200,000. R&S SMW200A: to 44 GHz, modulated BW 2 GHz. Best-in-class EVM. Price: $80,000-180,000. Keysight E8267D PSG: to 44 GHz with option, CW/modulated. Price: $50,000-120,000. Anritsu MG3710E: to 6 GHz (needs upconverter for mmWave).

Category: Test and Measurement Equipment

Updated: April 2026

Product Tie-In: VNAs, Spectrum Analyzers, Signal Generators

mmWave Signal Generator Selection

Testing at mmWave frequencies adds significant complexity and cost compared to sub-6 GHz testing, primarily due to the higher cable losses, connector challenges, and phase noise requirements.

OTA (Over-the-Air) Testing at mmWave

(1) Many mmWave devices (5G FR2 phones, phased-array modules) have integrated antennas with no RF test port. Testing must be done OTA in an anechoic chamber or compact antenna test range (CATR). The signal generator feeds a calibrated antenna inside the chamber. The AUT (Antenna Under Test) receives the signal in free space. The path loss between the source antenna and the AUT must be calibrated. (2) OTA test systems: Keysight UXM 5G Test Platform with mmWave remote radio heads. R&S CMX500 with CATR chamber. ETS-Lindgren/MVG anechoic chambers with integrated source/receiver. OTA test system cost: $200,000-1,000,000 (including chamber, positioner, instruments).

mmWave Signal Generator Specs

5G FR2: 24.25-52.6 GHz, 400 MHz BW
Phase noise at 28 GHz: < -95 dBc/Hz @ 10 kHz
EVM floor: < 1.0% for 256QAM testing
Cable loss at 28 GHz: 2-5 dB/m
Price: $50K-200K (direct to 44-67 GHz)

Common Questions

Frequently Asked Questions

Can I use a sub-6 GHz generator with an upconverter?

Yes. A common lower-cost approach: use a mid-range VSG (6-20 GHz) with an external frequency upconverter (mixer + LO) to reach mmWave. Advantages: lower instrument cost ($30,000-60,000 total). Disadvantages: higher EVM floor (the upconverter adds phase noise and distortion), additional complexity (two instruments), and limited output power. For R&D prototyping: this is a viable approach. For production or conformance testing: a direct mmWave VSG is preferred.

What about 77 GHz automotive radar testing?

Automotive radar at 77 GHz requires: a signal generator at 76-81 GHz (W-band). Options: VDI or OML frequency extenders driven by a 20-40 GHz generator, or dedicated automotive radar signal emulators (Keysight E8740A, R&S AREG100A). The radar test also requires: FMCW chirp generation (specific to automotive radar), target simulation (delay, Doppler shift, RCS), and antenna pattern characterization (OTA in anechoic chamber).

How important is phase noise at mmWave?

Phase noise is often the limiting factor for EVM at mmWave. At 28 GHz: the generator phase noise is approximately 9 dB worse than at 10 GHz (20 log(28/10)). For 5G NR 256QAM: the required EVM is 3.5%. The phase noise contribution to EVM must be < 1% to leave margin for other impairments. This requires integrated phase noise < 1° RMS (100 kHz to carrier/2). Only high-end generators achieve this at 28+ GHz. For 64QAM testing (EVM 8%): the phase noise requirement is 6 dB more relaxed, and mid-range instruments suffice.

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