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

Simons, Rainee N.

Wintucky, Edwin G.

NASA Technical Reports Server

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
https://ntrs.nasa.gov/search.jsp?R=20150000886 2019-08-31T14:05:01+00:00Z
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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 mm-
wave 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 step-
recovery 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-to-
noise 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 
1. R.J. Acosta, J.A. Nessel, R.N. Simons, M.J. Zemba, J.R. 
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 Millimeter-
Wave 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 
Technology Satellite (ACTS): Four-Year System 
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. 




Multi-Band (K- Q- and E-Band) Multi-Tone Millimeter-Wave Frequency Synthesizer for Radio Wave Propagation Studies

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