Contents
1USB / UART WARNING .............................................................................................................................. 2

2Characteristics ............................................................................................................................................. 3

2.1

Electrical Characteristics ......................................................................................................................................... 3

2.2

Thermal Operating Characteristics .......................................................................................................................... 4

3

Typical Performance ................................................................................................................................. 4

3.1

RF Output Power..................................................................................................................................................... 4

3.2

RF Output Harmonic Content .................................................................................................................................. 7

3.3

RF Port to Port Isolation .......................................................................................................................................... 8

3.4

Integer Boundary Spurs......................................................................................................................................... 10

3.5

Phase Noise and Jitter ........................................................................................................................................... 10

3.6Intermodulation Distortion after an External Wilkinson Combiner ....................................................................... 14

3.7

Performance over Temperature ............................................................................................................................ 15

4

Device Information ................................................................................................................................. 17

4.1

Mechanical Dimensions ........................................................................................................................................ 17

4.2

Product Renderings ............................................................................................................................................... 18

1 USB / UART WARNINGThe SynthHD Pro v2 was designed to work with, and ships with, a USB 2 cable. Use a USB 3 cable only when tapping intothe UART signals for 3.3V COM port control of the SynthHD Pro with your own microcontroller circuit. Using a USB 3cable attached to a USB 3 port on a PC may have unknown consequences as the PC is not designed to see the SynthHDUART signals and vv. See UART app note for UART usage instructions.

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10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2Windfreak Technologies, LLC.

2 Characteristics
2.1 Electrical Characteristics
Characteristic

Notes

Min.

Typ.

Max.

Unit

Supply Voltage

Suggested 2A minimum

4.7

55.5

V

Supply Current

420mA per channel

9001200mA

Both RF channels OFF70

Standby Supply Current
RF Output Frequency Range

10

Calibrated Frequency Range

10

RF Output Power Maximum

See graph

RF Output Power Minimum

See graph

RF OFF Output Power

100% shutdown of RF section

RF Frequency Resolution

Default is 100Hz selectable by Channel

6-17mA
24000

MHz20000

MHz20dBm
dBm-40-90dBm0.1

Hz0.01

dB0.01°

Spacing Setting
RF Output Power Resolution
RF Phase Resolution** See note 1

RF Output ImpedanceInternal Reference Frequency

Selectable

Internal Reference Tolerance
External Reference Frequency

Keep phase comparator less than1050

Ω10 or 27

MHz

2.5ppm-100

MHz100MHz
External Reference Level

Keep below 3.3VppTrigger

Internally pulled up

UARTdBm+10-0.3

3.3

V-0.3

3.3

VNote 1: Phase tuning speed, phase resolution and carrier frequency are inter-related. Phase tuning speed slows as RF
carrier frequency and Channel Spacing settings decrease. Smaller Channel Spacing will have higher phase andfrequency resolutions but slower phase tuning speed. Going below 100MHz carrier with smaller Channel Spacing
than 100Hz may be prohibitively slow and/or erratic.

10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

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2.2 Thermal Operating Characteristics
Description

Notes

MinMaxUnit

Operating Temperature

Without airflow or heatsinking-4030°C

Operating Temperature

software and keep below 75C with airflow,-4075 Internal°C

Query internal temperature sensor withheat sinking or limited duty cycle.

3 Typical Performance
3.1 RF Output PowerThe typical output power (per channel) of the SynthHD PRO is shown below. This graph is of raw
unleveled operation at both the maximum and minimum gain settings of the output variable gain section.
Gain is set via dBm power commands allowing output power levels anywhere in the range between theminimum and maximum levels shown below. RF port power and frequency can be set independent ofeach other. Power levels are settable in 0.01dBm increments. On board calibration is attained through alook up table for each channel. Device calibration is performed at the factory and stored in onboard
flash memory. Calibration is good from 10MHz to 20GHz. Operation from 20GHz to 24GHz is
uncalibrated and unspecified. All parts of the signal chain have high quality voltage regulation, and theD/A’s driving the VGAs have a 1% voltage reference controlling their outputs.

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Windfreak Technologies, LLC.

10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

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Note: +15dBm setting hitting max power limit above 12GHz

610MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2Windfreak Technologies, LLC.

3.2 RF Output Harmonic Content
The typical SynthHD PRO harmonic distortion is shown below for the second and third harmonics.
Also shown is a subharmonic created when generating fundamental frequencies above 15GHz. All
frequencies above 15GHz are generated with an RF doubler. This data is taken at a leveled fundamental
power of 0dBm.
If lower harmonic and subharmonic levels are needed, Windfreak Technologies suggest the use of low
cost SMA filters from Crystek and Minicircuits.
Example: Crystek Lowpass Filter – many cutoff frequencies, 1GHz example: CLPFL-1000, $25

Typical 100MHz waveform, both channels adjusted to 90 degrees offset (500MHz scope).
10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

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3.3 RF Port to Port Isolation
Port to port isolation is shown below with both channels at 0dBm output power. One trace is taken witha 3MHz offset between channels. The other trace is taken with a 20KHz offset between channels. The20KHz offset places each signal within each other’s loop bandwidth and the leakage modulates eachother’s VCO control voltages where loop gain is high. Offsets inside the loop bandwidth will haveworse isolation. The below data is taken with both PLL_ICP settings at 15.

Note: Performance below 3.7 GHz continues to trend downward.

810MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2Windfreak Technologies, LLC.

5GHz Port to Port Isolation Spectrum with +1MHz Offset
Note: The plot above shows the conducted port at 5.0 GHz. The terminated port is set at 5.001 GHz.
The spur location is at a 2MHz offset since the SynthHD Pro uses an RF divide by 2 circuit to achieve
5GHz. As the RF frequency decreases, the isolation spurs move out, until they are eventually outside ofthe loop bandwidth and thus significantly attenuated.
10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2Windfreak Technologies, LLC.

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3.4 Integer Boundary Spurs
A mechanism for in band fractional spur creation in all fractional PLL’s is the interactions between theRF VCO frequency and the internal 27MHz, internal 10MHz or arbitrary external reference frequency.
When these frequencies are not integer related, spur sidebands appear on the VCO output spectrum at anoffset frequency that corresponds to the difference in frequency between an integer multiple of thereference and the VCO frequency. These spurs are attenuated when outside the loop filter which is12KHz wide. By having two selectable internal reference frequencies of 10MHz and 27MHz theproblem is eliminated by switching reference frequencies when working around a boundary.
Example if using the SynthHD PRO 27MHz internal reference: For the fundamental VCO range of3400MHz to 6800MHz the first integer boundary happens at 27MHz X 126 = 3402MHz, the next at
27MHz X 127 = 3429MHz and every 27MHz thereafter up to 6777MHz. Above and below thefundamental VCO band the spacing will be affected by the RF doubler or RF divider respectively. If thedesired VCO operating frequency is 3402.01MHz this would give spurs 10KHz on either side of thecarrier that may be unacceptable. In this case, using the 10MHz reference would be suggested since its
closest integer boundary is at 3400MHz. Spurs 2MHz away will be attenuated to satisfactory levels bythe loop filter.

3.5 Phase Noise and Jitter

250MHz Phase Noise

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1GHz Phase Noise

5GHz Phase Noise

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Windfreak Technologies, LLC.

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10GHz Phase Noise

15GHz Phase Noise

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20GHz Phase Noise

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3.6 Intermodulation Distortion after an External Wilkinson Combiner
It’s possible to lock both channels in both frequency and amplitude for easy tuning during IMD testingof IP3 in passive and active components. The plot below shows two tones combined with a YL-70 0.52.0 GHz KL combiner that has roughly 20dB of isolation between ports. The tones are centered at
1GHz and separated by 1MHz. This method will allow for IP3 testing below roughly +40dBm.

Two Tone Generation via Wilkinson Combiner

1410MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2Windfreak Technologies, LLC.

3.7 Performance over Temperature
The SynthHD Pro has an algorithm to reduce amplitude drift over temperature. The user can specify 4different control settings in the firmware.
0) No temperature compensation
1) Compensation only during a frequency or amplitude setting2) #1 plus periodic adjustments every 1 second3) #1 plus periodic adjustments every 10 seconds (factory default)
Temperature compensation 2 and 3 are turned off during active modulation. Frequency sweeps andhops are only compensated for each step unless the setting is 0.
All subsequent temperature plots are based on an internal temperature measurement with temperaturecompensation turned ON. When the SynthHD has one RF channel turned on in a lab environment withmoderate air flow at 25°C the internal temperature will usually be around 40°C.

10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

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10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

4 Device Information
4.1 Mechanical Dimensions

10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

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4.2 Product Renderings

Top USB Side

Bottom RF Side

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10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

10MHz – 24GHz Dual Channel Signal Generator, Hardware Rev. 2
Windfreak Technologies, LLC.

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