Today, we officially announce the Valon 5015, a new model in our line-up of frequency synthesizers. In this blog, Stuart provides some background on why we developed it, its capabilities, and the challenges of delivering the best phase noise on the market at a very low price point.
I have been a practicing RF engineer for many decades. One thing that has always interested me is the criteria other engineers use to buy and use test equipment for their labs. It is not uncommon to see an expensive HP/Agilent/Keysight or Rohde and Schwarz signal generator in a lab, set to the same common frequency and amplitude for years. The old saying: “Nobody ever got fired for buying IBM” seems to apply here, especially at capital equipment budget time.
I have also noticed that more important than fancy modulation and all the other bells and whistles, was the need for more than one signal source used in a test setup. Generally, something like two local oscillators, or a local oscillator and sampling clock, or maybe two RF test tones was always a common requirement. These sources didn’t need to be anything particularly special; they just needed to be available. That is what prompted us, several years ago, to start designing and manufacturing our own line of modular signal sources that could replace expensive laboratory test instruments.
Our market model has always been to provide a low-cost signal source module with good signal purity and stability that was easy to program and simple to integrate into a test rack or equipment chassis. Non-volatile data memory has been a key function in every synthesizer we made. We always had models with USB communication, but we shied away from ever requiring USB power.
The new 15GHz Valon 5015 synthesizer is a culmination of our current understanding of our customers’ needs and budget. Frequency range was one area for improvement. The Valon 5009 went to 6GHz, which continues to satisfy many of our customers’ applications. However, we became aware that a few of our customers were using our synthesizers with frequency doublers and triplers to get into the higher bands. So, the Valon 5015 was developed with the specific goal of covering all of X-band and most of Ku-band without sacrificing phase noise. In fact, the 5015 phase noise is outstanding. Take a look at the plot below. That’s -100dBc/Hz at 10kHz offset at 15GHz, which is very good for a wide-range signal source for under $2K.
Providing higher frequency output is only useful if you can also provide higher power. That is why we wanted to get at least +10dBm across the entire microwave bands from 1GHz to 15GHz. The 5015 is guaranteed to provide greater than +13dBm from 100MHz to 15GHz and typically can supply +15dBm at most frequencies. That is a lot of power particularly in the microwave range. That means you can drive many devices like multipliers directly without any additional power gain stages.
Of course, it is not much of a benefit for a source to go to 15GHz if the phase noise is mediocre. So providing the best phase noise at a very low price point was also a top priority goal. To keep the price under $2000 we had to rule out using YIG tuned oscillators, multiple offset loops, and ovenized crystal oscillators. Instead we evaluated all manufacturers of integrated synthesizer chips and various topology configurations using our signal source analyzer in order to select the best devices. By using the best available ICs with our offset sub-synthesizer topology, we were able to achieve better than -100dBc/Hz at 10kHz offset at 15GHz, which is very good.
Providing low spurs and avoiding boundary spurs was a secondary goal. The Valon 5015 does use a fractional-N main synthesizer so “frac” spurs are not completely unavoidable, but they can be greatly reduced. The 5015 topology uses a somewhat common method of changing reference frequencies in the 100MHz range to dodge boundary spurs. What we do that is unique is our method of generating a low phase noise sub-synthesized reference frequency and the reference frequency selection algorithm. This method minimizes boundary spurs while not sacrificing phase noise.
In addition to the low phase noise and high power, another innovation we added in the 5015 is calibrated absolute output power. Two new factors contributed to this development. One is the use of the best broadband, flat-gain, MMIC amplifiers. These are expensive but we feel they are worth the cost. The other innovation is our automatic synthesizer test station. This is an amazing combination of test hardware and software that allows us to automatically test output power at many frequency points and power levels and record the results in a test file for each synthesizer. The synthesizer then uses this data file to interpolate and compensate the synthesizer output for the exact power output at any particular frequency. This new scheme has the benefit of not only allowing the user to specify a desired output power in dBm accurately, but also allows for fine amplitude level setting. The overall result is a flat and calibrated output power over the entire 10MHz to 15GHz range.
All of our synthesizers have provided a USB control interface so the user can use either a command line based terminal emulator program or our GUI to talk to the synthesizer. The 5009 provided a second asynchronous 2-wire TTL port as another serial interface to our synthesizer. This is great for most machine-to-machine control applications, but some of our customers were using multiple 5009s in large arrays for research and factory control applications. The USB or serial interface was not the optimum way to easily control many devices.
So, the Valon 5015 adds an Ethernet access port as well. We didn’t include the typical Ethernet RJ-45 in our product, but instead used a high quality 2-mm connector. The advantage is that the housing can be much thinner. This means less wasted material when machining, but it also makes the EMI shielded cavities smaller and less prone to moding. This is common in a microwave device that covers multiple octaves. The other consideration is that including the RJ-45 in our product would limit the ability to embed our product in our customers’ application. A lot of our synthesizers end up in a rack-mounted chassis which contains a lot of other hardware. Having the ability to put the RF end of the synthesizer where it is needed in the most direct way while still allowing the Ethernet connection to be located remotely is a huge advantage in many applications.
Lastly, I’d like to mention our Valon 5015 switching power regulation. Many engineers think that a switching power supply has no place in a low-noise RF product. But if that was strictly the case, there would be no spectrum analyzers, no vector network analyzers, and virtually no other pieces of commercial test equipment. A synthesizer as advanced as the 5015 uses more power than can be handled with linear regulation. Plus, we didn’t want to limit our customers to using a narrow power voltage range. We have a lot of experience designing RF products for our customers that integrate an RF signal processing scheme in amongst a lot of power-hungry digital components. So we know how to make switchers pretty quiet. The switching frequency and its harmonics in the 5015 are virtually undetectable. We are pretty proud that the 5015 can use any input power from 5Vdc (4.5V guaranteed minimum at the dc input connector so you can have some cable loss from your 5V supply) to 15V maximum (and a skosh over, 16V maximum).
By the way, like all Valon products, all our devices are reverse voltage protected. Even with an industrial component like ours, it is important to realize that mistakes happen. No user wants to have his project put on hold because he accidently blew up a device due to the power supply connection being configured ass-backwards.
The Valon 5015 incorporates many years of RF experience and know-how into a new 15GHz synthesizer module. We are sure you will find that it offers precision and versatility at a low cost, and look forward to hearing about how you integrate it into your applications.