SynthHD PRO (v2): 10MHz – 24GHz Dual Channel Microwave Generator


The Windfreak Technologies SynthHD PRO is a 10 MHz to 24 GHz dual channel software tunable RF signal generator and frequency sweeper controlled and powered by a device running Windows or Android via its USB port. The SynthHD PRO’s dual independent channels can be configured to run as two different frequencies, or the same frequency with different phases.  This allows its use in antenna beam steering applications or quadrature signal generation commonly used in image reject frequency conversion.

The SynthHD PRO also has nonvolatile onboard flash memory so it can be programmed to fire up by itself on any frequency, power, sweep or modulation setting (and combinations thereof) to run without a PC in the field. This makes for a highly mobile, low power, and lightweight solution for your RF signal generation needs.

Expect excellent performance and high reliability despite the SynthHD Pro’s low cost.

In Stock.  Ships within 3 days.

The Windfreak SynthHD PRO RF signal generator is similar to the SynthHD but has these extra features:

  • Improved calibration for higher amplitude accuracy
  • Milled aluminum case for better electrical performance and use in more rugged environments
  • SynthHD PRO has 100uS frequency step time
  • CE certification
  • Easy stack-ability

Product Lightlights:

  • 10 MHZ to 24 GHZ in 0.1 Hz steps
  • -40 dBm to +18 dBm (typical) in 0.01 dB steps
  • Set each channel to independent frequencies and amplitudes
  • 0 to 360 degrees coherent phase control in 0.01 degree steps on each channel
  • Stack multiple devices for coherent phase control on every channel
  • Select internal 10 or 27MHz reference or use external 10-100MHz reference
  • Pulse, AM, and FM internal modulation including FMCW radar chirp
  • Pulse Modulation with 1uS minimum width and 1uS resolution
  • Pulse, AM, and FM external modulation from DC – 10KHz
  • Powerful Trigger modes allow external triggering of most functions without a PC connected
  • Linear and list mode (frequency and amplitude hopping) sweeps include dual channel differential sweeps
  • Save all settings to the device for use without a PC
  • 32 bit ARM processor onboard which is Arduino compatible
  • Digital schematics and complete Labview GUI executable and source code (pictured below) included with purchase
  • Windows, Linux, and Android compatibility
  • Designed and manufactured in the USA with maximized value and cost ratio

Contact us for custom firmware and hardware options

SynthHD Pro Software GUI (Labview source code included with purchase)


The following video shows the SynthHD Pro doing a Pulsed FM Radar Chirp (FMCW) that is simultaneously AM modulated.

The video below is taken with both channels driven into a mixer. The mixer is then fed into an oscilloscope and displayed on the right side of the video. The signal shows the DC and near DC downconverted component. The DC level depends on the phase relationship between the two channels. The switch on the far right of the GUI toggles between controlling channels (RFA or RFB).

For orders over 10 units discounts will apply. Request a quote here. Emails will be answered within 24 hours. Keep an eye on your SPAM folder. You will be given a lead time and a quote if you desire large volume.

Download SynthHD Pro Model

(If drawing does not show up, disable popup blockers such as ublock in chrome.)

Measure dimensions by downloading the model and installing the free edrawings viewer app..

Weight 1.5 lbs
Dimensions 7 × 5 × 2 in

Features List

  • Amplitude calibration from 10MHz – 20GHz
  • Open source Labveiw GUI software control via USB
  • Run hardware functions with or without a PC
  • 32-bit ARM processor on board
  • Two channel frequency, phase and amplitude control
  • Quadrature (or other phase) LO signal generation
  • 1Hz frequency resolution
  • 01 degree phase control on each channel
  • 100uS RF lock time standard
  • Up to +20dBm output power
  • 01dB amplitude resolution
  • Over 50dB of power control
  • Absolute power display on Software GUI
  • 10MHz – 100MHz external reference input
  • Selectable 10 or 27 MHz internal reference output
  • 5ppm internal reference accuracy
  • Internal and external FM, AM, Pulse Modulation
  • Pulsed FMCW Chirp
  • External sweep, step and modulation trigger
  • 500 point frequency and amplitude hop table
  • Dual channel frequency and amplitude lock
  • Channel enable / disable saves energy
  • 5 Ultra low noise linear regulators on board
  • 0 X 2.15 inches not including RF connectors
  • USB or UART control via USB-C connector
  • Operation from 20GHz to 24GHz is uncalibrated


SynthHD PRO v2 Hardware Improvements:

  • Frequency response improved to 10MHz to 24GHz
  • Amplitude calibration from 10MHz to 20GHz
  • No 1/2 subharmonic on frequencies below 15GHz
  • Better high-frequency RF power around +15dBm at 10GHz and +8dBm at 20GHz
  • Better high-frequency RF pulse on/off isolation and speed
  • 500 point nonvolatile frequency and amplitude hop table
  • Better no-compensation amplitude stability over temperature
  • Improved mechanical housing facilitates custom bulkhead mounting
  • USB-C connector is tougher, plus brings in native UART control
  • Switch to 5V power supply
  • Larger faster flash memory for larger calibration, step, and modulation tables
  • New software is backwards compatible to version 1 devices

1. USB and UART Warning

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

2. Characteristics

2.1 Electrical Characteristics

Supply Voltage4.755.5VSuggested 2A minimum
Supply Current9001200mA420mA per channel
Standby Supply Current70mABoth RF channels OFF
RF Output Frequency Range10-24000MHz
Calibrated Frequency Range1020000MHz
RF Output Power Maximum61720dBmSee graph
RF Output Power Minimum-40dBmSee graph
RF OFF Output Power-90dBm100% shutdown of RF section
RF Frequency Resolution0.1HzDefault is 100Hz selectable by Channel Spacing Setting
RF Output Power Resolution0.01dB
RF Phase Resolution0.01°** See note 1
RF Output Impedance50
Internal Reference Frequency10 or 27MHzSelectable
Internal Reference Tolerance2.5ppm
External Reference Frequency10-100MHzKeep phase comparator less than 100MHz
External Reference Level10dBmKeep below 3.3Vpp
Trigger-0.33.3VInternally pulled up

Note 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 and frequency resolutions but slower phase tuning speed. Going below 100MHz carrier with smaller Channel Spacing than 100Hz may be prohibitively slow and/or erratic.

2.2 Thermal Operating Characteristics

Operating Temperature-4030°CWithout airflow or heatsinking
Operating Temperature-4075 Internal°CQuery internal temperature sensor with software and keep below 75C with airflow, heat sinking or limited duty cycle.

3. Typical Performance

3.1 RF Output Power

The 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 the minimum and maximum levels shown below. RF port power and frequency can be set independent of each other. Power levels are settable in 0.01dBm increments. On board calibration is attained through a look 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 the D/A’s driving the VGAs have a 1% voltage reference controlling their outputs.

SynthHD Pro Per Channel 10MHz-1GHz

SynthHD Pro Power Per Channel 1GHz-20GHz

SynthHD Pro Power Per Channel 20GHz-24GHz

Typical SynthHD Pro Calibration
Note: +15dBm setting hitting max power limit above 12GHz

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

SynthHD Pro Harmonic Content With 0dBm Fundamental Power

Typical 100MHz Waveform
Typical 100MHz waveform, both channels adjusted to 90 degrees offset (500MHz scope).

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 with a 3MHz offset between channels. The other trace is taken with a 20KHz offset between channels. The 20KHz offset places each signal within each other’s loop bandwidth and the leakage modulates each other’s VCO control voltages where loop gain is high. Offsets inside the loop bandwidth will have worse isolation. The below data is taken with both PLL_ICP settings at 15.

SynthHD RF Pro Port to Port Isolation
Note: Performance below 3.7 GHz continues to trend downward.
5GHz Port to Port Isolation Spectrum with +1MHz Offset
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 of the loop bandwidth and thus significantly attenuated.

3.4 Integer Boundary Spurs

A mechanism for in band fractional spur creation in all fractional PLL’s is the interactions between the RF 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 an offset frequency that corresponds to the difference in frequency between an integer multiple of the reference and the VCO frequency. These spurs are attenuated when outside the loop filter which is 12KHz wide. By having two selectable internal reference frequencies of 10MHz and 27MHz the problem 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 of 3400MHz 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 the fundamental VCO band the spacing will be affected by the RF doubler or RF divider respectively. If the desired VCO operating frequency is 3402.01MHz this would give spurs 10KHz on either side of the carrier 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 by the loop filter.

1GHz Phase Noise

5GHz Phase Noise

10GHz Phase Noise

15GHz Phase Noise

20GHz Phase Noise

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 testing of IP3 in passive and active components. The plot below shows two tones combined with a YL-70 0.5-2.0 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
Two Tone Generation Via Wilkinson Combiner

3.7 Performance over Temperature

The SynthHD Pro has an algorithm to reduce amplitude drift over temperature.  The user can specify 4 different control settings in the firmware.

  1. No temperature compensation
  2. Compensation only during a frequency or amplitude setting
  3. #1 plus periodic adjustments every 1 second
  4. #1 plus periodic adjustments every 10 seconds (factory default)

Temperature compensation 2 and 3 are turned off during active modulation.  Frequency sweeps and hops are only compensated for each step unless the setting is 0.

All subsequent temperature plots are based on an internal temperature measurement with temperature compensation turned ON.  When the SynthHD has one RF channel turned on in a lab environment with moderate airflow at 25°C the internal temperature will usually be around 40°C.

Typical Error vs Temperature vs Frequency -10dBm

Typical Error vs Temperature vs Frequency 0dBm

Typical Error vs Temperature vs Frequency +10dBm

4. Device Information

4.1 Mechanical Dimensions

SynthHD Pro Mechanical Dimensions

4.2 Product Renderings

SynthHD Pro Product Renderings - Top USB Side

SynthHD Pro Product Renderings - Bottom RF Side


  • Wireless communications systems
  • Antenna beam steering
  • Quadrature LO for image reject mixers
  • RF and Microwave radios
  • Software Defined Radio (SDR)
  • Radar including FMCW
  • Automated Test Equipment (ATE)
  • EMC – radiated immunity pre-compliance testing
  • Electronic Warfare (EW) and Law Enforcement
  • IP3 Two Tone Intermodulation Distortion Testing
  • Quantum device research
  • Plasma physics


  1. Datasheet
  2. Quickstart Guide
  3. Software Users Guide
  4. Control Software GUI Download (hit Cancel during hardware search if demo-ing software)
  5. Linux & Windows Command Line Guide
  6. UART Hookup Guide for Arduino and Raspberry Pi
  7. Python Package

V2 is 95% similar in software and commands to v1.4.

Old v1.4 Downloads

Downloads for SynthHD Pro (ver 1 which is 54MHz – 14GHz):

  1. Datasheet
  2. SynthHD vs SynthHD PRO Phase Noise Comparison
  3. Software Users Guide
  4. Control Software GUI Download (hit Cancel during hardware search if demo-ing software)
  5. Linux & Windows Command Line Guide
  6. Compare with the SynthHD
  7. SynthHD Press Release
  8. Python Package