Rainee N. Simons and Edwin G. Wintucky

Glenn Research Center, Cleveland, Ohio

Multi-Band (K- Q- and E-Band) Multi-Tone

Millimeter-Wave Frequency Synthesizer for

Radio Wave Propagation Studies

NASA/TM—2014-218438

December 2014
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Rainee N. Simons and Edwin G. Wintucky

Glenn Research Center, Cleveland, Ohio

Multi-Band (K- Q- and E-Band) Multi-Tone

Millimeter-Wave Frequency Synthesizer for

Radio Wave Propagation Studies

NASA/TM—2014-218438

December 2014

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Acknowledgments

The support from the 2013 NASA GRC Center Innovation Fund (CIF) is gratefully acknowledged. 

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NASA/TM—2014-218438 1 

Multi-Band (K- Q- and E-Band) Multi-Tone Millimeter-Wave Frequency 

Synthesizer for Radio Wave Propagation Studies 

Rainee N. Simons and Edwin G. Wintucky*

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

This paper presents the design and test results of a 

multi-band multi-tone millimeter-wave frequency synthesizer, 

based on a solid-state frequency comb generator. The intended 

application of the synthesizer is in a space-borne transmitter for 

radio wave atmospheric studies at K-band (18 to 26.5 GHz), 

Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). These 

studies would enable the design of robust multi-Gbps data rate 

space-to-ground satellite communication links. Lastly, the 

architecture for a compact multi-tone beacon transmitter, which 

includes a high frequency synthesizer, a polarizer, and a conical 

horn antenna, has been investigated for a notional CubeSat 

based space-to-ground radio wave propagation experiment. 

1.0 Introduction 

The frequency spectrum allocated and utilized currently for 

satellite communications uplinks and downlinks are rapidly 

getting congested due to very heavy usage. The logical choice 

is to move higher up in frequency into the millimeter-wave 

(mm-wave) frequency bands, which are sparsely used. The 

mm-wave bands include frequencies in the Q-band (37 to 

42 GHz) and the E-band (71 to 76 GHz). Migrating to the mmwave frequency bands has the added advantages of smaller 

antenna size and lower mass for a given spacecraft effective 

isotropic radiated power (EIRP). In addition, in the case of 

commercial communications satellites, which use multiple 

beams to increase throughput, the beamwidth for a given 

antenna aperture size is smaller at the above mm-wave 

frequencies. The smaller beamwidth results in a smaller spot 

size on ground, which allows packing a greater number of spot 

beams over a given area and thus enables greater spectral 

efficiency through frequency reuse. Prior to system planning 

and system design for deployment in space, it is essential to 

investigate the effects of Earth’s atmosphere on radio wave 

propagation at the above frequencies. In general, radio waves 

suffer increasing attenuation, scintillation, depolarization, and 

group delay due to atmospheric gases, clouds and rain (Ref. 1). 

In this paper, we present the design, construction and test 

results for a multi-band multi-tone millimeter-wave frequency 

synthesizer (Ref. 2) based on the discrete frequency spectrum 

produced by a high frequency solid-state comb generator. 

 

*

Retired. 

Unlike the single frequency beacon source, which flew on 

NASA’s Advanced Communications Technology Satellite 

(ACTS) (Ref. 3) for Ka-band propagation experiments 

(Ref. 4), the multi-tone frequency synthesizer is capable of 

simultaneously delivering coherent multiple frequencies. These 

multiple frequencies enable characterizing the frequency 

dependent group delay effects, which are essential for the 

design of multi-Gbps data rate wide band satellite 

communications links. 

2.0 Multi-Tone Frequency Synthesizer 

Architecture 

2.1 Multi-Tone Frequency Synthesizer 

Circuit Design, Construction and 

Mode of Operation 

Harmonic generators are a convenient way to generate high 

frequency signals, when direct generation of the high 

frequencies is challenging. Harmonics are generated whenever 

a sinusoidal signal drives a non-linear capacitance, that is the 

capacitance varies instantaneously with voltage or current. 

Such generators have become practicable because of the 

availability of high quality step-recovery diodes. The steprecovery diodes are also know as charge-storage or snap-back 

diodes. The theory of harmonic generation using step-recovery 

diodes can be found in Reference 5. 

A simplified block schematic of the basic multi-tone 

frequency synthesizer based beacon transmitter that could fly 

on a geostationary satellite as a hosted payload for radio wave 

propagation experiments at mm-wave frequencies is presented 

in Figure 1. The synthesizer consists of a comb generator, 

which puts out evenly spaced harmonic frequencies of the input 

signal, which are coherent and tunable over a wide frequency 

range. These harmonics are then amplified to the power level 

needed for radio wave propagation studies. 

Harmonics that are amplified are simultaneously transmitted 

as beacon signals from space to receiving ground stations 

located at several climate zones within the CONUS. By 

measuring the signal relative strength and phase at ground sites 

one can estimate the attenuation and group delay or dispersion 

due to atmospheric induced effects. 
NASA/TM—2014-218438 2 

2.2 Rational for a Multi-Band Multi-Tone 

Frequency Synthesizer Circuit, Design, 

and Construction 

Significant amount of statistical data has been accumulated 

since the pioneering ACTS experiments of the 1990’s and 

accurate models that predict the impairments to radio waves in 

the 20/30 GHz bands due to Earth’s atmosphere are available. 

In addition, communications satellite systems are currently 

operational at these frequencies. It is also well understood that 

signals at Q-band and E-band frequencies would experience 

much higher attenuation during rain fades than signals in the 

20/30 GHz range. The deep fades will result in poor signal-tonoise ratio at the Q-band and E-band beacon receivers on 

ground, which could cause the receivers to lose frequency/ 

phase lock. To overcome this problem it is desirable to include 

a coherent K-band (18 to 26.5 GHz) beacon source along with 

the Q-band and E-band beacon sources on the payload. Because 

of higher signal-to-noise ratio at K-band, the beacon receiver 

on ground can retain lock during deep fades and thus enable 

high availability attenuation measurements or characterization. 

This data is valuable and can provide a reference for model 

development and also provide an understanding of frequency 

model scaling factors for future system design when Q-band 

and E-band propagation data is unavailable (Ref. 1). 

A block schematic of the multi-band multi-tone frequency 

synthesizer breadboard circuit is presented in Figure 2. The 

synthesizer consists of a high frequency wideband solid-state 

comb generator. The K-band and Q-band harmonics are 

separated by bandpass filters and amplified to the power level 

required for radio wave propagation studies before 

transmission. 

2.3 K-Band/Q-Band Multi-Tone Frequency 

Synthesizer Characterization and 

Test Data 

A generic test setup for characterizing the K-band and the 

Q-band multi-tone frequency synthesizer circuits described 

above is presented in Figure 3. Photographs of the K-band and 

the Q-band breadboard coaxial test set up are shown in Figures 

4 and 5, respectively. Notice that the set up is very compact. 

The bandpass filters and the low noise amplifiers (LNAs) are 

appropriately selected for the two frequency bands. The 

measured K-band and Q-band spectrums are presented in 

Figures 6 and 7, respectively. The tones are 1 GHz apart, but 

can be tuned by changing the frequency of the input signal to 

the frequency comb generator. Figures 8 and 9 present the 

results for the case when the tones are 500 MHz apart. These 

figures indicate that the spectrum is very distinct with excellent 

signal-to-noise ratio. In addition, it is worth while to point out 

that the K-band and Q-band multi-tones are coherent since they 

are derived from a common input signal source as indicated in 

Figure 2. A chain of MMIC based power amplifiers can further 

enhance the power levels such that the beacon EIRP is on the 

order of 30 dBW at the edge of CONUS coverage (Ref. 6). A 

minimum data collection period of 36 months is recommended 

and hence the above EIRP is the end of life value (Ref. 1). 
NASA/TM—2014-218438 3 
NASA/TM—2014-218438 4 
NASA/TM—2014-218438 5 

2.4 E-Band Multi-Tone Frequency 

Synthesizer Characterization and 

Test Data 

The test setup for characterizing the E-band multi-tone 

frequency synthesizer is presented in Figure 10. A photograph 

of the E-band breadboard waveguide (WR-12) test set up is 

shown in Figure 11. An E-band frequency extension module 

consisting of a harmonic mixer and a diplexer are used to extend 

the frequency range of the spectrum analyzer. The separation 

between the tones can be tuned by changing the frequency of 

the input signal to the frequency comb generator. 

The measured E-band spectrums at the output of the low noise 

amplifier (LNA) are presented in Figures 12 to 14. These plots 

are for tones that are 1, 2, and 3 GHz apart in frequency, 

respectively. The corresponding amplitudes are also indicated in 

the figures. Notice that the tones are very distinct with excellent 

signal-to-noise ratio. In addition, spectrum analyzer 

measurements were conducted with the frequency span control 

set for narrow frequency range. As an example, Figure 15 

presents one such tone measured at the center frequency of 

70 GHz with the frequency span set equal to 100 MHz. The 

results indicate that the linewidth of the tone is on the order of 

3 to 4 MHz close to the noise floor. A chain of MMIC power 

amplifiers can enhance the power of the tones to any desired level. 
NASA/TM—2014-218438 6 
NASA/TM—2014-218438 7 

3.0 Phase Noise Characteristics 

The phase noise of the multi-tones degrades by 20 log of the 

multiplication factor. Hence, if we assume that the phase noise 

of the input signal source driving the comb generator is 

–152 dBc/Hz at 10 kHz offset and if the multiplication factor is 

20 then the phase noise of this tone is –152 + 20 log (20), which 

is –126 dBc/Hz. Similarly, if the multiplication factor is 35 then 

the overall phase noise is –121 dBc/Hz. 

4.0 Temperature Characteristics 

The measurements reported here were performed at room 

temperature. Hence, additional studies are required to quantify 

the effect of temperature on the multi-tone frequency 

synthesizer output frequency and power. 

5.0 Space Radiation Effects 

Studies conducted by other researchers have indicated that 

the step recovery diodes are susceptible to neutron damage 

(Ref. 7). The degree of damage is dependent on the amount and 

time of exposure to neutron fluence. 

6.0 E-band Multi-Tone Frequency 

Synthesis by Upconverting 

K-Band Multi-Tones 

To avoid the degradation of phase noise as described above, 

it is possible to up convert the K-band multi-tones from the 

output of the wideband power divider (Fig. 2) with a mixer 

circuit. However, such a design has several disadvantages. 

First, besides a broadband mixer circuit the system also requires 

an additional local oscillator (LO), which makes the overall 

design more complex. Second, the additional components 

potentially increase the overall cost. Third, mixing also 

produces image and other spurious signals, which have to be 

filtered out. Lastly, if coherent K-band and E-band multi-tones 

are to be simultaneously transmitted then, the above LO has to 

be phase locked to the signal source exciting the wideband 

frequency comb generator (Fig. 2), which further increases the 

complexity and cost. 

7.0 Notional CubeSat Space 

Experiment Package 

A basic multi-tone beacon transmitter chain, which includes 

a high frequency synthesizer, a polarizer, and a conical horn 

antenna has been configured and illustrated in Figure 16. The 

transmitter chain is compact enough to be accommodated inside 

a 1U CubeSat as illustrated in Figure 17. The CubeSat 

architecture is being investigated for a notional space-to-ground 

radio wave propagation experiment.

8.0 Conclusions 

The design, construction and test data for a K-band, 

Q-band, and E-band multi-tone frequency synthesizer for radio 

wave propagation studies are presented. The tones in each of 

the above bands are very distinct with excellent signal-to-noise 

ratio. The beacon transmitter will enable characterizing the 

frequency dependent group delay effects, which are essential 

for the design of multi-Gbps data rate wide band satellite 

communications links. 

Lastly, a simplified layout for a compact multi-tone beacon 

transmitter for a notional CubeSat based space-to-ground radio 

wave propagation experiment has been presented. Besides, 

radio wave propagation studies, the multi-tone frequency 

synthesizer can be used for space borne active remote sensors 

like scatterometers, which require coherent, highly stable multi 

frequency signals. 
NASA/TM—2014-218438 8 

References 

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Morse and J. Budinger, “W/V-Band RF Propagation 

Experiment Design,” 18th Ka and Broadband 

Communications Navigation and Earth Observation 

Conference Digest, pp. 355–362, Ottawa, Canada, 

Sept. 24–27, 2012. 

2. R.N. Simons and E.G. Wintucky, “Multi-Tone MillimeterWave Frequency Synthesizer for Atmospheric Propagation 

Studies,” 2014 IEEE International Symposium on 

Antennas and Propagation and USNC/URSI National 

Radio Science Meeting Digest, Memphis, TN, July 6–12, 

2014. (Also published as NASA/TM—2014-218122, 

April 2014). 

3. R. Bauer, “Ka-band Propagation Measurements: An 

Opportunity with the Advanced Communications 

Technology Satellite (ACTS),” Proc. IEEE, vol. 85, no. 6, 

pp. 853–862, June 1997. 

4. R.J. Acosta, R. Bauer, R.J. Krawczyk, R.C. Reinhart, M.J. 

Zernic, F. Gargione, “Advanced Communications 

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Performance,” IEEE Jour. Selected Areas in 

Communications, vol. 17, no. 2, pp. 193–203, Feb. 1999. 

5. H.A. Watson (Editor), “Microwave Semiconductor 

Devices and Their Circuit Applications,” McGraw-Hill 

Book Co., New York, 1969, Section 7.6, pp. 187–190. 

6. R.N. Simons and E.G. Wintucky, “Q-Band (37–41 GHz) 

Satellite Beacon Architecture for RF Propagation 

Experiments,” 2012 IEEE Symposium on Antennas and 

Propagation and USNC/URSI National Radio Science 

Meeting Digest, Chicago, IL, July 8–14, 2012. (Also 

published as NASA/TM—2014-218124, April 2014). 

7. R.J. Chaffin, “Neutron Damage Effects in Step Recovery 

Diode Frequency Multipliers,” IEEE Trans Nuclear 

Science, vol. 18, no. 6, pp. 366-370, Dec 1971.