SynthNV PRO: 12.5MHz – 6.4GHz RF Signal Generator Plus RF Detector

Specifications

1. USB and UART Warning

The SynthNV Pro 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 SynthNV 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 SynthNV Pro UART signals and vv. See UART app note for UART usage instructions.

2. Characteristics

2.1 Electrical Characteristics

Characteristic	Min.	Typ.	Max.	Unit	Notes
Supply Voltage	4.7	5	5.5	V	Suggested 1A minimum
Supply Current		250		mA
Standby Supply Current		60		mA	RF output OFF
RF Input / Output Frequency Range	12.5	-	6400	MHz
Calibrated Frequency Range	12.5		6400	MHz
RF Output Power Maximum	6	11	15	dBm	See graph
RF Output Power Minimum		-45		dBm	See graph
RF Input Power Range	-40		15	dBm	Max is +20dBm before damage
RF OFF Output Power			-80	dBm	100% shutdown of RF section
RF Output Frequency Resolution	0.1			Hz	Default is 100Hz selectable by Channel Spacing Setting
RF Output Power Resolution	0.01			dB
RF Phase Resolution	0.01			°	** See note 1
RF Output Impedance		50		Ω
Internal Reference Frequency		10 or 27		MHz	Selectable
Internal Reference Tolerance		2.5		ppm
External Reference Frequency	10	-	100	MHz	Keep phase comparator less than 100MHz
External Reference Level	-10	10		dBm	Keep below 3.3Vpp
Trigger	-0.3		3.3	V	Internally pulled up
UART	-0.3	3.3	5	V	3.3V native, 5V tolerant

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

Description	Min	Max	Unit	Notes
Operating Temperature	-40	50	°C	Without airflow or heatsinking
Operating Temperature	-40	75 Internal	°C	Query 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 of the SynthNV Pro is shown below. This graph is of unleveled operation at the maximum gain setting of the output and -45dBm for the minimum setting. Settings between these two levels will be controlled and uncalibrated levels can be attained below -45dBm. RF output 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. Device calibration is performed at the factory and stored in onboard flash memory. Calibration is good from 12.5MHz to 6.4GHz. All parts of the signal chain have high quality voltage regulation, and the D/A driving the VGA have a 1% voltage reference controlling their outputs. Maximum power transitions in the graphs below are due to switch points in the switchable output harmonic filter and are not user controllable.

3.2 RF Output Harmonic Content

The typical SynthNV Pro harmonic distortion is shown below for the second and third harmonics. This data is taken at a leveled fundamental power of 0dBm.
If lower harmonic 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

3.3 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 30KHz 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 SynthNV Pro 27MHz internal reference: For the fundamental VCO range of 3200MHz to 6400MHz the first integer boundary happens at 27MHz X 119 = 3213MHz, the next at 27MHz X 120 = 3240MHz and every 27MHz thereafter up to 6399MHz. Below the fundamental VCO band the spacing will be affected by the RF divider. If the desired VCO operating frequency is 3213.01MHz 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 3210MHz. Spurs 3MHz away will be attenuated to satisfactory levels by the loop filter.

3.4 Phase Noise and Jitter

3.5 RF Power Detector

The power detector on the SynthNV Pro is comprised of a broadband log detector that is calibrated from 12.5MHz to 6.4GHz. Between it and the input SMA connector is a 10dB pad designed to give a broadband 50 ohm match, plus allow higher powers (up to 15dBm) into the detector. Between the log detector and the analog to digital converter are 3 selectable circuits for advanced users. The default is an instantaneous sample which samples the RF power at an indeterminate time quickly after its initiated. The other two involve 1) a resistor/capacitor averaging circuit and 2) a diode/capacitor peak detector circuit which is uncalibrated due to its diode voltage drop. The last two circuits specifics are TBD but may help in application with high peak to average RF power.

The detector knows nothing about the frequency content of the signal it is receiving. It only measures power and the power it measures is a summation of all content across its working spectrum. (It is not a spectrum analyzer.)

In closed systems using the signal generator and power detector, it is possible to know the frequency the detector is reading, plus calibrate out any amplitude error. This allows the device to function as a scalar network analyzer which can be used to sweep the frequency response of amplifiers, attenuators and filters. Its also possible to use an external directional coupler to measure the return loss of those types of devices.

The plot below shows a typical raw Detector Error trace relative to the calibrated output power of the signal generator side (which also has some embedded error). The Cal Error trace shows the error after a software calibration is performed with the supplied GUI Network Analyzer application.

4. Device Information

4.1 Mechanical Dimensions