When I saw that Abracon had reasonably priced programmable oscillators available, I knew I had to get some. There is a variety of different oscillators with different specifications available. I picked the Abracon ASDMB series MEMS (Micro Electro Mechanical System) oscillators [1] [2]. To be able to program these oscillators, one needs the MEMSpeed Pro II programmer and an adapter socket [3].

First off, a warning. MEMS oscillators aren’t the best performers when it comes to phase noise performance. So wherever phase noise plays an important role, these oscillators are probably not your best choice. But for that, MEMS oscillators or MEMS actuators / sensors in general are significantly less sensitive to vibrations and mechanical shock.

I got my MEMSpeed Pro II kit and the ASDMB adapter kit directly from Abracon. Any adapter kit comes with 50 blank oscillators. The case that the MEMSpeed Pro II comes in offers space for two adapter cards and plenty of blank ICs. There are numerous different oscillators with different parameters available [4].

Here’s a close-up of the MEMSpeed Pro II kit:

MEMSpeed Pro II kit with adapter socket and some blank oscillators

As you can see, there’s space for two socket cards and plenty of blank oscillators in the case. The USB drive contains all the software necessary for the programmer. Please make sure you install the software before you connect the programmer for the first time. The reason is that the programmer uses a proprietary USB driver that should be installed before the device talks to the PC for the first time.

Close-up of the MEMSpeed Pro II programmer and the adapter card with opened socket

The adapter card connects to the side of the MEMSpeed Pro II. Once everything is connected, one can hook up the programmer to the PC and start the software. The software is really self-explanatory. After entering the target frequency and clicking the “Program” button, the MEMS oscillator is programmed.

The software for the MEMSpeed Pro II is very easy to use

The “Measure” section of the software makes it possible to verify that the burn went correctly. However, it seems that the precision of this feature is not the best. It’s enough to make sure that the frequency is about right, but please don’t trust the last digit.

For an experiment, I programmed one of my ASDMB oscillators to the frequency 145.565, which is the national frequency for radio direction finding in the amateur radio community. I used my brand new Teledyne LeCroy HDO4024′s spectrum analyzer capabilities to obtain some data on the device’s performance.

As indicated above, the phase noise performance of MEMS oscillators is not the best. The following shot shows this clearly on the instantaneous spectrum and the historical spectrogram:

Output spectrum of a Abracon ASDMB programmed to 145.565 MHz viewed on a Teledyne LeCroy HDO4025

Next up is the harmonic output. The Teledyne LeCroy automatically marks harmonics and displays the level. Unfortunately, I entered a slightly off fundamental frequency (145.5 instead of 145.565). But the representation is still valid.

Using the harmonic marker function of the Teledyne LeCroy HDO4025 12-bit high definition oscilloscope to view the harmonic content of the output signal

The ASDMB oscillators can operate between 1 and 150 MHz. They can be operated between 1.8 and 3.3 V and work well over the entire range. There are different temperature options available ad there are 3 sub-types available, which are designed for an output load of 10 kΩ and either 15, 25 or 40 pF of capacitive load. At 3.3 volts, the rise time is better than 2 nS.

Altogether, this is a very nice product and from now, on a must have in my lab. From now on, I will have almost any frequency available whenever I need it. The only way Abracon could make me happier would be by coming out with an MEMS VCO that can be pulled by an external voltage.

Links and Sources:

[1] ASDMB Datasheet, Abracon: http://www.abracon.com

[2] ASDMB Blank Oscillators, Mouser: http://www.mouser.com/

[3] MEMSpeed Pro II, Mouser: http://www.mouser.com/

[4] MEMS Overview, Abracon: http://www.abracon.com/

Not too long ago I reviewed ADI’s wideband PLL synthesizer ADF4351 with integrated low phase noise VCO. The ADF4360 series family of synthesizer chips is very similar. The primary difference is their restricted frequency coverage and thus much lower price.

The ADF4360 is an integrated integer-N synthesizer with an integrated voltage controlled oscillator (VCO). The center frequency is set by external inductors. There are 9 chips in the family with 8 different frequency ranges. The frequency range are as follows:

ADF4360-0: 2400 to 2725 MHz
ADF4360-1: 2050 to 2450 MHz
ADF4360-2: 1850 to 2170 MHz
ADF4360-3: 1600 to 1950 MHz
ADF4360-4: 1450 to 1750 MHz
ADF4360-5: 1200 to 1400 MHz
ADF4360-6: 1050 to 1250 MHz
ADF4360-7: 350 to 1800 MHz
ADF4360-8: 65 to 400 MHz
ADF4360-9: 65 to 400 MHz

Even though the ADF4360-8 and ADF4360-9 have the same frequency range, they are a bit different. The ADF4360-9 has an auxiliary divider with division ranges from 2 to 31 on board. The ADF4360-8 has – just like all other ADF4360 – a hardware power down input (CE).

Analog Devices kindly sent me one of their Evaluation Kits for the ADF4360-9 (EV-ADF4360-9EB1Z) for review and evaluation [1].

EV-ADF4360-9EB1Z evaluation board from Analog Devices

What I intend to use this chip in is called a Fox-Hunt transmitter. It has very little to do with hunting actual foxes and actually relates to a common radio direction finding exercise. The way this works is that a small transmitter (the “fox”) is hidden somewhere and a group of people will attempt to locate the transmitter. Whoever finds the transmitter first, wins the game.

I want to build a very small transmitter for the 2m amateur radio band (~145 MHz) with just a few miliwatts of output power. With such a low power VHF transmitter, a radio direction finding exercise could be conducted in a small area like a park, or even more challenging, with several transmitters at the same time. A microcontroller is supposed to be in charge of setting the frequency and keying the required station identification (call-sign of the control operator) as required by the FCC.

But now back to the ADF4360. The chip has an SPI compatible 3-wire interface, operates between 3 – 3.6 Volts and its inputs are 1.8 V logic compatible. In other words: this chip will interface with pretty much any microcontroller out there. My project will probably be Atmel AVR or MSP430 based and I program in C. However, I will write example code for Arduino (AVR) / Energia (MSP430) for folks who would like to experiment with it more easily.

I looked at the output spectrum of the ADF4360-9 set to 400 MHz on a Teledyne LeCroy HDO6054. The phase frequency detector (PFD) frequency is 200 kHz and you can clearly see spurs 200 kHz spaced to both sides of the carrier. The spurs are smaller than -70 dBc and, to be fair, the ADF4360-9 is not correctly terminated. The IC has a differential output and the datasheet warns that the performance of the output signal may be degraded if not both ports are properly terminated with 50 Ohms. In my case, only one port is fed into the 50 Ohm port of the scope. The other port is open.

Output spectrum of a ADF4360-9 at 400 MHz with a 200 kHz PFD frequency. Clearly visible, the spurs 200 kHz left and right from the carrier

In any case, -70 dBc is a lot of attenuation. As a matter of fact, the output signal could be transmitted the way it is over the air. The FCC demands in 74 CFR 97.307 (e) that “the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency between 30 – 225 MHz must be at least 60 dB below the mean power of the fundamental.” This is clearly the case.

The eval board comes with a very comfortable software, just like the ADF4351 did. It is very nice to be able to manipulate all registers and parameters and watch what happens right away.

So what’s next? I will design the circuit, design a PCB, and write the necessary software code for the little VHF tracker (“fox”). The project will be an open hardware project. That means you will be able to use my project free of charge for personal use. As soon as that is done, I will post a new article with the entire project in it. Stay tuned!

Links and Sources:

[1] ADF4360-9, ADI: http://www.analog.com/

To make the evaluation of the CC2531 a bit easier, TI put together the CC2531EMK. The CC2531EMK is a an evaluation kit containing a USB dongle built around the CC2531 [1]. Element 14 sent me a CC2531 USB dongle development kit as part of a RoadTest. RoadTest is a program sponsored by Element 14 that promotes real product reviews by real people like us.

CC2531 USB Dongle plugged into my Netbook

Overview and Tech Specs

The CC2531 is a USB-Enabled System-On-Chip Solution for 2.4-GHz IEEE 802.15.4 and ZigBee applications in a tiny 6-mm × 6-mm QFN40 package. The chip is 8051-based, has 8 kB of RAM and is available with either 128 kB (CC2531F128) or 256 kB (CC2531F256) of In-System-Programmable (ISP) flash [2].

Since the chip is compliant with various national and international standards, namely ETSI EN 300 328 and EN 300 440 (Europe), FCC CFR47 Part 15 (US), and ARIB STD-T-66 (Japan), products built around this chip do not need to worry about national and international compliance. With a maximum output power of 4.5 dBm (2.82 mW), the chip is perfect for small range communication.

The CC2531 provides extensive hardware support for packet handling, data buffering, burst transmissions, data encryption (AES Security Coprocessor), data authentication, clear channel assessment, link quality indication (Accurate Digital RSSI/LQI) and packet timing information.

With 21 general-purpose I/O Pins and a 12-Bit ADC with 8 channels and configurable resolution, the chip supplies plenty of peripherals for external circuitry.

Unboxing

The box contains the CC2531EMK USB dongle and a quick start guide. The quick start guide is straight to the point and easy to understand.

CC2531EMK on top of the quick start quide

While reading the quick start guide, I realized that there is no way to program the MCU’s flash memory without the use of an external debugger. Such a debugger needs to be purchased individually. In other words, one can’t program the CC2531EMK without buying a debugger like the CC Debugger, for instance [3].

Software Installation

To get started with the CC2531 dongle, one needs to install the appropriate drivers. The driver package comes bundled with a packet sniffer application which TI provides. Be careful to use the correct URL for the download. It is not – as falsely indicated in the quick start manual – http://www.ti.com/packetsniffer! The correct URL is: http://www.ti.com/tool/packet-sniffer

Download and install the software package from the previously mentioned URL. After the installation is complete, your PC should automatically recognize your CC2531 dongle and apply the pre-installed drivers.

Upon start-up of the packet sniffer software, one has to select the protocol one intends to use. For the CC2531, the only possible options are “IEEE 802.15.4/ZigBee” and “ZigBee RF4CE”.

TI Packet Sniffer Application

The next thing that needs to be selected is, of course, the correct RF channel.

SmartRF Packet Sniffer Channel Selection

One can specify which fields of the captured traffic that the SmartRF packet sniffer software displays.

SmartRF Packet Sniffer filter selection

Summary

This is a nice piece of kit to evaluate the CC2531. However, the kit alone is not of much use. To actually accomplish anything useful, one needs at least one additional IEE 802.14 / ZigBee device. And in order to program it, an extra programmer / debugger is required.

I will go ahead and buy a CC Debugger and post again soon with my experience of the CC2531EMK in an actual (demo) application.

Links and Sources:

[1] CC2531EMK, Newark: http://www.newark.com/

[2] CC2531 Datasheet, TI: http://www.ti.com/

[3] CC Debugger, Newark: http://www.newark.com/

Before I write any further, let’s agree on some nomenclature. For the sake of this article, I will use 220 Volts and 240 Volts interchangeably. In Europe, the correct supply voltage is 240 Volts AC. However, actual supply voltages range between 220 Volts and 240 Volts. Americans usually speak of “220″ when referring to European voltages. Similarly, many Americans refer to their own supply voltage as 110 Volts even though it is actually rated at 120 Volts nominal. So again, for the sake of this article I will use 110 and 120 interchangeably.

I have a bunch of European equipment that works on 240 Volts only. Here in the US, I naturally only have 110 V available. While it is technically possible to combine two 110 Volt lines to create a 220 Volt line, I do not currently have that option to do so as my lab is fed by a single 110 V line only.

The solution to my problem is as simple as finding a 110 to 240 Volts transformer. If you have a power requirement of more than 1000 Watts, this can be a pretty expensive solution, though. Therefore, iIwas very surprised to find this 2000 W transformer for less than $100 [1]. For that price, I decided I’d give it a try.

Goldsource STU-2000 front view

There’s no actual magic inside the box. Inside the case is a standard transformer with a set of different primary taps.

According to the tech specs, this transformer will accept 110, 120, 220, and 240 Volts as input voltage. It supplies 110 Volts and 220 Volts on its output at the same time over two different receptacles.

I did measure 220 Volts output in actual working conditions with 110 Volts input. Accordingly, I could measure 240 Volts out with 120 Volts input while keeping the input selector set to “110 Volts.”

Goldsource STU-2000 input voltage selector

The transformer was pretty smelly at first. I assume this was the smell of the fresh paint. After airing it out for a few hours, it stopped smelling funny. The operation noise is barely audible and depends on the actual load.

Goldsource STU-2000 opened up.

The overall look of this transformer is pretty solid. The wiring has been done pretty well and the wires seem to have adequate thickness. The device is fused twice. There is a 20 A fuse on the primary side and another resettable 20 A fuse on the secondary side (220 V only). There are 2 spare primary fuses supplied with the transformer.

Goldsource STU-2000 secondary side

Just when I was about to close the transformer back up, I noticed a wire that looked a little bit suspicious. Have a look, do you see it?

Faulty wire in the 200 V primary hook-up

The transformer works very well for my purpose. I have several SMD soldering tools and other scientific devices powered through this device. Most devices do not mind about the fact that the mains frequency is not being translated. European mains frequency is 50 Hz and in the USA it’s 60 Hz. Only devices which derive timing information from the mains frequency, like cheap alarm clocks for instance, will have difficulties dealing with the wrong frequency.

Links and Sources:

[1] Goldsource STU-2000, Amazon: http://www.amazon.com

Today, I tried out a 300 Watt 12 V DC to 220 V AC inverter I bought off eBay not too long ago. For just $26.50 including shipping, I got it from the eBay seller hi-autopia [1]. I was already suspicious because of the low price, but decided to give it a try anyway. So here it is:

Label of the One-Hung-Low brand 300 W inverter

I could not find any information on this manufacturer at all. A tag on the side of the inverter indicates it was manufactured somewhere in Asia. So how well would this One-Hung-Low brand inverter perform? Well, let’s start with some visible results of my test:

Molten 4mm probes (Hirschmann Kleps 30)

Yes, those were perfect 4mm test clips at some point. So what happened? The inverter was connected to a 12 V battery through the above test clips and a pair of 4mm test leads. Probably not the best for continuous current at the maximum 300 Watts, but okay for the 60 Watts I used as a test load. And just for the record, the DC hook-up wire that was supplied with the inverter was about half as thick as my test leads.

Input side of the 300 W inverter.

The load I used for the test was a 60 W 220 Volt soldering iron. A soldering iron is an entirely resistive load and shouldn’t cause any hardship on an inverter. I measured the output voltage across the output of the inverter, a steep 420 volts while idle. Once I connected the soldering iron, it fell to 230 Volts. The voltage seemed to drop every second or so. It looked as if the circuitry had difficulties regulating the output voltage. But before I could hook up my oscilloscope and take a screenshot, I started smelling smoke. And shortly after that, the smoke started coming out of the case of the inverter. My test clips started glowing bright orange before I finally got to disconnect the inverter from the battery.

Output side of the 300 W inverter.

I thought this was awfully weird. Not only was the behaviour of the inverter strange, it seemed like the inverter had no protection circuitry whatsoever. While thinking about it, I noticed that this inverter does not have a fuse on the input side like most professional inverter do. So the fuse had to be on the inside. I mean, it couldn’t be that the inverter isn’t fused, right?

Closer look at the input section of the inverter

Well, guess again, there’s no fuse or any other means of protection in the input circuitry. To skip ahead: There’s none in the output section either. But more about that later. Just by glancing at the circuitry, I suspect this is a modified sine wave inverter. And with that in mind, I am very surprised about the size of the transformer (yellow). For 300 W output, I’d expect a transformer to be capable of handling at least 500 VA. The transformer used here looks more like 12 VA…

Close up view of the circuitry revealing several safety issues

The first thing that caught my eye was the lack of a proper routing for the 220 V traces. At high voltages, traces must be spaced out as far as possible to avoid arcing to ground planes or other traces. Ideally, the design should implement an actual physical separation by utilizing milled notches. In the above pictures, the 220 V wires are the two thin black wires in the bottom right corner.

General overview of the 300 W inverter

The low spacing between the PCB and the case is concerning, as well. There are absolutely no precautions taken in order to prevent the solder joints to touch the case. As a matter of fact, the two bend transistors in the bottom left corner may have been bent over the way they are for some degree of “protection.”

There seems to be a temperature sensor as fault prevention. But just by looking at the discolored casing of one of the two driver MOSFETs, I suspect this fault detection is not very effective, to say the least.

By the way, the device is, of course, not certified under Part 15 of the FCC rules.

I did send a message to the eBay seller hi-autopia about this and will supply him with a link to this article. His reaction should be rather interesting. While I doubt he knew about the quality (or the lack thereof), this is a great opportunity for him to show how well he responds to customer complaints and how he resolves them.

Links and Sources:

[1] hi-autopia, eBay: http://www.ebay.com/

Dieter has a huge selection of toroids and magnet wire for an extremely low price. I was really surprised by the prices he offers as I used to pay a fortune for the same things from other distributors. At first, I thought the prices were a little too good to be true but I tried out his store, paid with PayPal and received the goods within 2 business days, no problems or catches at all!

Assortment of common toroid types

Some other things I found in his store were Intermediate Frequency (IF) transformers. IF transformers are also referred to as IF cans because of the metal can shield around the actual inductor. The formerly big players in the market for IF cans, Sumida and Toko, discontinued their production a long time ago. Since then, it can be a hassle finding a reliable and inexpensive source for these products. I asked about the reliability of his stock and Dieter indicated: “All parts listed on my website are expected to last as long as I do.”

455 kHz IF filters

Links and Sources:

[1] Dieter Gentzow, W8DIZ: http://www.kitsandparts.com/

The ADF4351 from Analog Devices (ADI) is a modern wideband PLL synthesizer with integrated low phase noise VCO. It is capable of generating signals between 35 MHz to 4400 MHz with a very low jitter of typical 0.3 ps. ADI agreed to send me the EVAL-ADF4351EB1Z, an evaluation board for the ADF4351, for review purposes. Let’s check it out!

The ADF4351 has an integrated voltage-controlled oscillator (VCO) with a fundamental output frequency ranging from 2200 MHz to 4400 MHz. In addition, divide-by-1/-2/-4/-8/-16/-32/-64 circuits allow the user to generate RF output frequencies as low as 35 MHz. For applications that require isolation, the RF output stage can be muted. The mute function is both pin- and software-controllable. An auxiliary RF output is also available, which can be powered down when not in use. Control of all on-chip registers is through a simple wire interface. The device operates with a power supply ranging from 3.0 to 3.6 V and can be powered down when not in use.

ADF4351 evaluation board

ADI ships the EVAL-ADF4351EB1Z with a USB cable and a CD. The CD contains all software necessary to get started right away. The board itself makes a very clean impression. Despite the surface mount technology, all case styles of the components used can comfortably be handled with appropriate hand soldering tools. This allows for easy application specific modifications.

There are two 4 mm jacks for power (3.75 V to 5.5 V), a small USB connector, and 3 SMA connectors on the board. The first SMA connector serves as reference input for an external reference signal. Alternatively, it can be used as an output for the on-board reference (25 MHz). The other two SMAs are the primary RF output of the ADF4351. It is a differential pair. For best performance, make sure to terminate both outputs correctly (50 Ohms) even if just one output is being used.

Power can either be supplied through the 4 mm banana jacks or the USB port. Switches S1 and S2 are used to select the power source. Switch S1 is used to power the ADF4351 from the external DC connector and switch S2 to power from the USB port. The USB clock can cause spurs in the RF signal if power is derived from the USB port.

Plenty of test points on the board allow easy troubleshooting. An additional 100 mil / 2.54 mm header can be populated to gain easier access to the most important logic signals.

The external loop filter on the eval board has a bandwidth of 35 kHz. This value can easily be changed by changing the value of the corresponding components. The software package ‘ADIsimPLL’ from Analog Devices is a great tool for designing an application specific loop filter.

Make sure to install the software from the CD before connecting the evaluation board to the PC for the first time. Once the software is installed properly, connect the board to the PC and start the ADF4351 software package. If the two power LEDs on the board (D5 and D6) do not light up upon connection, verify S1 and S2 for proper selection of the desired power source.

ADF4351 Application Software

The software is self-explanatory. It allows accessing and manipulating of all functions and registers of the ADF4351. Additionally, the software allows you to use the evaluation board as a sweep generator and it can do frequency hopping between two frequencies.

After trying this board out for a while, I highly recommend this chip. It is small, inexpensive ($8.25, 100 QTY) and extremely simple to integrate.

I can think of many applications for the ADF4351 in the amateur radio community. The ADF4351 a perfect 21st century alternative for older SP5055 based designs. The SP5055 was a very popular synthesizer chip used in many older amateur radio projects.

The chip is predestined to be used as a flexible Local Oscillator (LO) in amateur radio transverters. A flexible LO frequency allows to cover more bandwidth in the target frequency range than the IF transceiver itself offers. Paired with a baseband processor and a power amplifier, this chip easily transform into an inexpensive amateur television (ATV) transmitter. I will show some practical designs and applications in future articles. Stay tuned!

Links and Sources:

[1] ADF4351, ADI: http://www.analog.com/

[2] ADF4351 Datasheet, ADI: http://www.analog.com/

[3] Evaluation Board User Guide, ADI: ftp://ftp.analog.com/

The Teledyne LeCroy WaveStation 2052 is a 50 MHz, 2-channel Function/Arbitrary Waveform Generator with 14-bit resolution, 125 MS/s and 16 kpts memory depth. It’s supposed to be a high-quality entry-level arb gen and designed to be a great lab mate for the the WaveAce-series oscilloscopes. T&M Instruments [1] was once again kind enough to supply a demo device for review purposes. Let’s check it out!

Front view of the WaveStation 2052

As usual with this kind of function generators, the exact characteristics and limitations depend on which channel is being used and what kind of waveform is being generated.

For the whole WaveStation-series, channel 2 is the “better” channel in regards of maximum amplitude. The maximum amplitude of channel 2 is 4 mVpp to 20 Vpp for frequencies ≤ 10 MHz and 4 mVpp – 10 Vpp for frequencies larger than 10 MHz and high impedance. If 50 Ohm impedance is selected, the available amplitude range is cut in half.

The amplitude range of channel 1 is 4 mVpp – 6 Vpp for high impedance and half of that for 50 Ohm impedance. What “high impedance” exactly means in this regard is nowhere to be found in the datasheet. I asked Teledyne LeCroy to provide this info and ideally update the datasheet to reflect this information, as well.

50 MHz sine wave, generated with the WaveStation 2052

The possible frequency range also depends on the selected waveform. It is 1 μHz – 50 MHz (Sine), 1 μHz – 25 MHz (Square), 500 μHz – 5 MHz (Pulse), 1 μHz – 300 kHz (Triangle / Ramp), and 1 μHz – 5 MHz (Arbitrary Waveforms).

150 kHz triangle waveform, generated by the WaveStation 2052

I am not going to cover every tiny detail of the tech specs here. The article is supposed to reflect my personal experience with the WaveStation 2052 and not to just cite the information from the datasheet. If you are interested in the tech specs in greater detail, please consult the datasheet [2].

There are more arbitrary waveforms pre-programmed into the WaveStation than one can count. They are organized in different groups for easier access.

Some of the built-in arbitrary waveforms of the WaveStation 2052

If the supplied arbitrary waveforms aren’t enough, you can build your own. Teledyne LeCroy offers a free software package designed exactly for that purpose [3].

The datasheet promises a rise time of smaller than 12 ns. This number seems pretty conservative compared to the value I measured. My measurement determined a rise time of 4.8 ns.

4.8 ns rise time at 25 MHz

Built-in modulation capabilities include AM, PM, FM, ASK, FSK and PWM. That’s a few more than most entry-level function generators offer. The user can choose to use an internal modulation source or apply an external modulation signal.

In the modulation menu, I also found a modulation type labelled “DSB-AM.” There is absolutely no explanation about this modulation type in the datasheet. DSB-AM is a common designator for “regular” amplitude modulation (AM) resulting in two sidebands and a carrier. That didn’t make sense as this type of AM is already listed in the menu as “AM.” So what’s up with that?

Double-sideband (DSB) is one of the built-in modulation schemes of the WaveStation 2052

I wondered if they might mean double-sideband modulation (DSB). There are two kinds of double-sideband modulation. The first being double-sideband reduced carrier (DSB-RC), in which the original carrier stays present but with limited amplitude. The second is double-sideband suppressed carrier (DSB-SC). DSB-SC would definitely be like hitting the jackpot. To my knowledge, this modulation type is not commonly offered in entry-level function generators (nor in pricier generators, for that matter).

To see what this mysterious modulation type is, I connected the WaveStation 2051 to a WaveAce 1002 oscilloscope and set the WaveStation as follows: 10 kHz sinusoidal carrier “DSB-AM” modulated with a 1.25 kHz sinusoidal tone. And this is what it looked like in the frequency domain (bottom trace):

10 kHz DSB carrier modulated with a 1.25 kHz sine tone. No remaining carrier is visible, just the two sidebands.

Bingo, jackpot! It’s double-sideband suppressed carrier. We can clearly see the absence of the original 10 kHz carrier and the two sidebands. The sidebands are both exactly 1.25 kHz away from the original carrier. This finding immediately ups the value of the WaveStation 2052 by a lot. Teledyne LeCroy should make sure to mention this bonus point in the manual of the WaveStation and on their webpage.

The DSB modulation can also be used to conduct such called two-tone measurements to determine intermodulation products in linear systems. This feature is very useful for checking the linearity of a HF amplifier for instance. How this works in a practical setup, I will show in a future article.

The menu structure is pretty organized and menu options are where you would expect them to be. Rarely-used featured are hidden a bit deeper in the menu structure than frequently used features. Most functions are self-explanatory, yet there is a great operator’s manual available [4] in case any questions arise.

I do have one suggestion towards the functionality of the rotary encoder (big black dial, top right corner), though. It appears that the rotary encoder also has a tactile switch function. This function is, however, not utilized anywhere. It would improve the user experience significantly if this tactile switch could be used as “select” or “confirm” button when values are being selected using the rotary encoder. At the moment one selects the right value with the rotary encoder and then needs to press a different button to confirm the selection.

If GPIB (IEEE 488) compatibility is needed, a USB to IEEE 488 adapter is available. That way the WaveStation integrates seamlessly into more complex automatic test setups.

A 10 MHz input for an external reference signal is available on the back of the WaveStation. This is a very important feature for me as I synchronize every piece of equipment in my lab to an extremely accurate 10 MHz reference. Make sure to enable the external reference input in the menu, though. The device defaults to the internal reference if an external signal is not found.

The dimensions of the WaveStation are 105 mm x 229 mm x 281 mm (4.1” x 9.0” x 11.1”). Due to its compact size, it fits well even on every moderately crowded workbench. With just 2.6 kg (5.7 lbs), it’s pretty lightweight, as well.

Thanks to its wide power supply range of 100 – 240 VAC and a frequency range of 45 Hz to 440 Hz, this arb gen is excellent for service all around the world. Thanks to the wide frequency range, the function generator can even be used in special 400 Hz mains supply environments such as on board of an aircraft and in special military applications (MIL-STD-704).

The list price of the WaveStation 2052 is $3,450.00. If you are interested in buying one of these, contact T&M Instruments [1] directly. If you are unsure, you can request a demo as well and try the WaveStation out before you make a final decision.

This review is really just scratching the surface of what the WaveStation-series arbitrary waveform generators are capable of. Most features deserve an article on their own. And that’s what I plan on doing in the future. so stay tuned for more.

Links and Sources:

[1] T&M Instruments: http://www.tandm.net/

[2] WaveStation Datasheet, Teledyne LeCroy http://teledynelecroy.com/

[3] WaveStation Software, Teledyne LeCroy http://teledynelecroy.com/

[4] WaveStation Operator’s Manual, Teledyne LeCroy http://teledynelecroy.com/

If you have ever wanted to experiment with an RISC microcontroller that comes with special Digital Signal Processing (DSP) capability, the STM32F3DISCOVERY board might just be the right board for you to start with. STMicroelectronics shipped out a board to me for review. Let’s have a look!

The STM32 F3 series of microcontrollers are based on the 32-bit ARM Cortex-M4 core, which has Digital Signal Processor (DSP) extensions and a Floating-Point Unit (FPU). The STM32F3DISCOVERY board comes with an STM32F303VCT6 [1] microcontroller featuring 256 KB Flash, 48 KB RAM in an LQFP100 package [2].

• STM32F303VCT6, ST’s ARM® Cortex™-M4F based MCU with:
• 256 KB Flash
• 48 KB SRAM
• Maximum CPU Frequency: 72 MHz
• Real Time Clock (RTC)
• 2 x Watchdog
• 9 x 16-bit Timer
• 1 x 32-bit Timer
• 4 x 12-bit ADC (39 channels)
• 2 x 12-bit DAC
• 88 GPIOs
• 3 x SPI
• 2 x I2C
• 5 x USART
• USB
• CAN
• Supply Voltage: 2 – 3.6 V
• L3GD20, ST MEMS motion sensor, 3-axis digital output gyroscope
• LSM303DLHC, ST MEMS system-in-package featuring a 3D digital linear acceleration
  sensor and a 3D digital magnetic sensor.
• Flexible power supply options
• Power from either on-board USB connector
• External 3 V or 5 V supply
• On-board ST-LINK/V2
• Reset button
• One user push-button and 8 user LEDs
• 100 mil (2.54 mm) expansion headers

Due to the kind of sensors the board offers and the DSP functionality of the MCU, the board is perfect for navigational experiments. The board offers plenty of horsepower to be used in autonomous Unmanned Aerial Vehicles (UAVs) such as Quadcopters and RC planes.

The board looks very organized and cleanly routed. There are two USB-port. One for the user application and one for the ST-LINK/V2 debugger. ST did leave an unpopulated spot for an external crystal for applications which require greater accuracy / precision.

STM32 F3 Discovery Board, top view

What I particularly like is the 100 mil / 2.54 mm header on the bottom of the board. This header makes it easy to use breadboard style setups for experiments.

STM32 F3 Discovery Board, bottom view

The default firmware features 3 small sample applications. On power-up, the 8 user LEDs will start lighting in a circular motion. If the user button is pressed, the LEDs will now indicate the direction of acceleration. If the button is pressed again, the 8 LEDs will act as a compass and indicate the direction to magnetic north.

Here’s a short video of the first demo application. Sorry for the poor video quality.

The board is available for $10.88 from Newark [3].

Links and Sources:

[1] ST 32 F302-series MCUs, STM: http://www.st.com/

[2] STM32F3DISCOVERY User Manual, STM: http://www.st.com/

[3] STM32F3DISCOVERY User Manual, STM: http://www.newark.com/

The Abracon ABFT frequency translators / jitter attenuators are available as 20 MHz and 40 MHz versions. They both require a 10 MHz reference frequency input, have an ultra small footprint (5.00 x 7.00 mm) and only consume 14 mA under lock. Abracon sent me an evaluation board for the 20 MHz version. Let’s check it out!

Close-Up view of the Abracon ABFT eval board (20 MHz version)

Before we dive in, let’s talk about clock multiplication using a classic PLL design. To talk about the problems associated with classic PLL multiplier circuits, here is a simple 10 MHz to 20 MHz multiplier circuit:

Simple frequency doubler using a classic PLL based approach

I am intentionally mixing block diagram symbols and actual circuit drawing symbols for clarity. The VCOs output signal is divided by two using a D type flip flop. If the VCO frequency is exactly 20 MHz, the output of the D flip flop is 10 MHz. The output of the flip flop is then compared to the 10 MHz reference by a simple XOR gate based phase detector. How an XOR gate based phase detector works has been explained in one of my previous articles.

A big problem with that circuit (and most PLL designs for that matter) is the following: if the input signal is exactly 10 MHz with absolutely no jitter, everything works well. The phase noise performance of the output would then primarily depend on the used VCO. The problem is, jitter free signals simply don’t exist in the real world. Remember, jitter is the undesired deviation from true periodicity of an assumed periodic signal. Jitter can be observed in several of the signal parameters. Troublesome for this circuit are phase and frequency errors. We will talk about frequency errors only as every phase error forcibly causes instantaneous frequency errors.

Let’s assume the input signal jumps between 9,999,990 Hz and 10,000,010 Hz. Our PLL circuit is now doubling this error because it is a fixed x 2 multiplier. The jitter on the output signal will therefore essentially be twice the jitter on the input frequency. The output frequency will therefore jump between 19,999,980 Hz to 20,000,020 Hz. This condition is quite obviously undesirable.

A possible workaround is to increase the time constant of the loop-filter (R1 + C1). If overdone, the PLL will turn into a Frequency Locked Loop (FLL) and it will no longer be able to react to quick changes in phase and frequency differences. While this reduces the aforementioned problem drastically, the big loop time introduces a new problem. The loop is now too slow to correct errors quickly enough to have a reliable output signal. Additionally, the lock-time is increased significantly. Both are of course undesirable conditions.

Needless to say, designing such a PLL can be a big pain in one’s proverbial behind when there are heightened phase noise / jitter requirements on the table. It’s simply nothing that can be accomplished with your common 4046 CMOS or similar. So instead of trying experiment with different loop filters and trying to find the ‘right’ trade-off of loop properties for hours on end, why not grab something off the shelf that works right away? And that takes us right back on topic of the Abracon ABFT frequency translator.

Abracon ABFT frequency translator / jitter attenuator evaluation board

Here are the tech-specs straight from the datasheet [1]:

• 5x7x2 mm SMT, RoHS Compliant reflow-able package
• +3.3V Supply Voltage
• Temperature Range: -40ºC to +85ºC
• LVCMOS Output
• Frequency Stability Over the Whole Temperature Range: ± 25 ppb
• Supply Current Under Lock: < 14 mA
• Rise Time: < 1.2 ns
• Stand Alone Aging (10 years): + 12 ppm

To make the evaluation and experimentation process simpler, Abracon offers a small evaluation board for the ABFT [2]. The board’s dimensions are about 40 x 30 mm. Equipped with 3 industry standard SMA connectors (Reference in, V_dd, and RF Out), the board can quickly be implemented in test setups.

But that’s enough text for now. It’s time to look at some pictures. I used the ABPSM-ULN-A ultra low noise power supply module and the Abracon Sync ‘n Go together with the ABFT eval board in my test setup.

My test setup: The ABFT is connected to a Sync ‘n Go 10 MHz reference and an ultra low noise power supply using high quality coaxial cable

The first thing we’re going to have a look at is the output waveform. I am using the LeCroy WaveAce 1002 for the following two screenshots.

Output of the ABFT 20 MHz in the time domain

Shape, voltage and frequency look good. There’s a bit of ringing due to an impedance mismatch between the probe and the ABFT. The overshoot is caused by the impedance mismatch, as well. You might note that the rise time measured by the WaveAce is higher than what the ABFT’s datasheet claims. But no need to worry — what’s displayed here is the rise time of the LeCroy WaveAce 1002 as shown in my review. I simply do not have a scope that is capable of dealing with 1.2 ns rise time.

Output of the Abracon ABFT 20 MHz frequency translator on a LeCroy WaveAce oscilloscope. Top: Time domain, Bottom: Frequency domain

No surprise in the frequency domain either. Because an ideal rectangular signal is made up of sine waves of the fundamental frequency and uneven multiples of the fundamental frequency, the uneven harmonics displayed on the WaveAce 1002 are stronger than the even ones.

Now it’s time to look closer at the phase noise performance. Signal source analyzers are extremely expensive. That’s why I do not have one available to me. However, Abracon’s Syed Raza (Director of Engineering, Abracon Corporation) supplied proof for the phase noise performance without hesitation. He is also using the ABPSM-ULN-A ultra low noise power supply module and the Abracon Sync ‘n Go together with the ABFT eval board in his setup. The output of the ABFT eval board is fed into an Agilent E5052A signal source analyzer.

Setup to test the phase noise performance of the ABFT using an Agilent E5052A Signal Source Analyzer

The phase noise performance measured by the E5052A is at any given marker point better than what is mentioned in the datasheet. The black line is the phase noise of the ABFT and the blue line is a 10 MHz Stratum III reference.

Phase noise performance of the 20 MHz ABFT measured with an Agilent E5052A Signal Source Analyzer

The datasheet has some additional phase performance screenshots. Abracon shows for instance what happens when the input of the ABFT is fed with a dirty crystal oscillator. The phase noise is significantly improved.

Abracon suggests that the device is suitable for use in Telecom applications such as base station equipment, broadband modems, DSLAMs and base stations.

I can think of much simpler applications than that. For instance, 20 MHz and 40 MHz are both common clock frequencies for microcontroller. If a high precision requirement or simply the need to synchronize the MCU application to an external 10 MHz reference arises, this is pretty much the simplest way to go.

It is noteworthy that the ABFT still puts out a valid signal in free running mode if no reference input signal is present. Therefore, the ABFT would be very suitable for applications where a free-running mode is desired as well as the option to sync the device to a more accurate 10 MHz reference signal when required. I personally can see myself using this feature in future microwave synthesizer designs.

Mouser has both the 20 MHz and the 40 MHz versions in stock for $26.30 per piece [3]. That price is for single quantities. The price drops to $21.04 per piece for 500 ABFT modules. Reels are available with 250 or 1000 units per reel.

Links and Sources:

[1] Abracon ABFT Datasheet, Abracon: http://www.abracon.com/

[2] Abracon ABFT Evaluation Board, Abracon: http://www.abracon.com/

[3] Abracon ABFT 20 MHz, Mouser Electronics: http://www.mouser.com/