Microwave Journal

67 GHz Signal Generator Delivers High Output Power with Low Phase Noise and Harmonics

January 13, 2020

Rohde & Schwarz has extended the frequency range of the R&S SMA100B signal generator from 20 to 67 GHz, with intermediate options of 31.8, 40 or 50 GHz to best fit the application. The 40 GHz option, for example, covers all major radar bands in development and the 5G bands to 39 GHz. With the 67 GHz option - and overrange operation to 72 GHz - the instrument supports emerging satellite links at Q- and V-Band and the unlicensed 60 to 71 GHz bands used by IEEE 802.11ad and IEEE 802.11ay.

The R&S SMA100B is the only analog signal generator available with a large spurious-free dynamic range that can simultaneously generate high output levels with low harmonics, phase noise and wideband noise - even with the extended frequency range. The signal generator also has a continuous level sweep with a 70 dB dynamic range and the capability to generate chirp signals.


Figure 1

Figure 1 Measured single sideband phase noise vs. output frequency with the ultra-low phase noise option.

Figure 2

Figure 2 Measured output power vs. frequency with the high output power options.

Figure 3

Figure 3 The continuous power sweep has 70 dB dynamic range.

Figure 4

Figure 4 Amplitude modulated pulsed signal. The amplitude envelope is generated with an external source.

Figure 5

Figure 5 Chirp signal (10 µs duration, 30 MHz bandwidth) generated with the R&S SMA100B.

The R&S SMA100B is well suited for generating low noise local oscillator signals for radar applications, where extremely low phase noise is crucial. With the ultra-low phase noise option, the generator achieves a measured phase noise of −120 dBc/Hz at 20 kHz offset from a 40 GHz carrier (see Figure 1). As sampling rates increase with each generation of analog-to-digital and digital-to-analog converters, pure RF carriers with extremely low phase noise and low wideband noise are required to measure component and system performance. Complementing its ultra-low phase noise, the R&S SMA100B achieves low wideband noise: −150 dBc/Hz at 40 MHz offset from a 30 GHz carrier.

In practical test setups, the attenuation from cables and adapters can limit the measurement range. With the ultra-high output power option with integrated harmonic filters, the R&S SMA100B can compensate for most cable losses (see Figure 2), considerably simplifying test setups by eliminating the need for external amplifiers and harmonic filters. With this option, the R&S SMA100B can measure the saturated output power and compression characteristics of power amplifiers, particularly those using GaN devices. GaN amplifiers typically have higher saturated output power than GaAs-based amplifiers and, depending on the amplifier’s gain, may require higher input power to reach the 1 dB compression point and saturation.

To measure an amplifier’s full transfer function with an analog signal generator, the level sweep must cover a large dynamic range without interruption. Blanking the input power can cause an unpredictable reaction in an amplifier’s automatic level control, which should be avoided. The R&S SMA100B has an uninterrupted RF level sweep range of more than 70 dB without blanking or spikes (see Figure 3).


Received pulsed radar signals often have superimposed amplitude modulation, representing radar transmitters with rotating antennas and narrow lobes. In such cases, the receivers only receive short input signals. To simulate this scenario when testing, the ScanAM option of the R&S SMA100B can generate pulsed signals with superimposed amplitude modulation, with a modulation depth greater than 70 dB (see Figure 4).

Some radar systems, such as weather and long-range surveillance radars, use pulse compression, where each pulse is “chirped,” i.e., modulated with a linear frequency modulation. This improves range resolution, the ability to distinguish between two objects close to each other. The R&S SMA100B can generate chirp signals with adjustable chirp duration and bandwidth, even superimposing impairments such as AM noise and AM drift to simulate the influence of the receiver’s hardware (see Figure 5).

With new frequency options, the R&S SMA100B extends its frequency range to above 67 GHz and provides extremely low phase noise, high output power and low harmonics. These features make it well suited for testing radar receivers, other defense systems, mmWave telecommunications and RF semiconductors supporting these markets.

Rohde & Schwarz
Munich, Germany