IMS highlights microwave products and technologies
Monday June 3
As discussed during the Monday evening IMS reception, Huber+Suhner, a Swiss supplier of components and systems for electrical and optical connectivity, recently bought Astrolab. This sounds like a win-win situation: Astrolab, which offers its patented minibend and microbend cable assemblies, gets access to a much larger market, and H+S gains a well-respected brand.
Tuesday June 4
Agilent Technologies Press breakfast:
Barry Alcorn, Market Segment manager Americas field operation electronic measurement group, introduced Greg Peters, vice president and general manager for the Component Test Division, who presented some of the MIL/Aero areas that Agilent addresses. AXIe is a big part of that effort because of the higher power and increased channel count it supports.
Joe Rickert, R&D manager microwave and communications division electronic measurements group, discussed some of the challenges for broadband signal analyzers and signal generators. GP Tardioli, R&D manager, mobile broadband organization, Electronic Measurements Group, highlighted the conflict between the desirability for many more femtocells and similar small base stations, and the need for affordable pricing.
A huge number of radios are implied by the extension of internet-enabled devices. There is a similar drive to finer granularity, according to Ben Zarlingo, application specialist, to reduce the size of each area managed for smart grid applications. And, according to Rickert, one-third of the web traffic in the evening is Netflix streaming.
Noisecom’s JV9000 Series Programmable and Adjustable VCC Noise and Spur Generators are instruments that add programmable noise to a power supply voltage. The idea is to increase the noise until the product fails. Alternatively, you can use it to determine parameters such as power supply rejection ratio.
Boonton’s big news was the 55 Series USB peak power sensor that makes 40,000 readings/s. The company claims this is an order of magnitude faster than the competition—even if you choose to average eight or 10 readings, the result is still faster than most other meters.
The flexible resolution 5000 Series flexible resolution scope was being shown. The four-channel scope’s eight ADCs are combined in serial and parallel configurations to accommodate fast digital signals or slower analog inputs with wide dynamic range.
The company’s defense group has developed remote cal capabilities that solve the problem of long-term satellite test. Cal references are physically located next to the DUT inside the test chamber. This means that damage to cables or instrument replacement no longer requires extensive re-calibration. It’s done automatically via the local references. Clearly, the technique isn’t limited to satellite test, but that application is typical of very long-term expensive tests that can be compromised by cable or instrument problems.
Ben Zarlingo described the need for the RTSA capability for anomaly discovery and swept-tuned operation for familiarity. He said that with the 89600 VSA software, a user can transition from either RTSA or swept scalar information to I/Q vector solutions.
Finally, the company has developed remote capabilities for the FieldFox VNA, accessed from an iPhone or iPad. You need a Wi-Fi connection, but once connected, you can operate the instrument and view results from anywhere in the world.
David Asquith, a product manager based in Stevenage, UK, demo’d the new 3050A/3320 PXI Low Noise RF Signal Generator and Dual Channel AWG with phase-coherent multiple outputs suitable for MIMO development. The company’s PXI Maestro software allows up to eight cell phones to be concurrently tested.
Joe Mazzochette, general manager, discussed his company’s optical fiber-based microwave delay line products. With them, customers can simulate satellite communications complete with Doppler effects. Because a line is used to simulate the propagation delay, a line with multiple taps can model the interactions within a radio network. The company claims 40-GHz operation and because the line is all analog, very low noise and good resolution.
Mini Circuits:
Although the company does not provide extensive details about custom production test capabilities on its website, test instruments based on standard Mini Circuit modules can be a very cost-effective approach, and many projects have been successfully completed. One equipment rack displayed at the company’s booth contained an RF oscillator and 100-W power amplifier together with 16 to 32 channels derived from splitters. Contact the company directly for more information: [email protected].
Wednesday June 5
Papers on MRI RF Coils:
I attended a couple of presentations about medical imaging: Rennings, et al., “A MIM/Coaxial Stub-Line CRLH Zeroth-Order Series-Mode Resonator used as an RF Coil Element for 7-Tesla Magnetic Resonance Imaging,” and Chen, et al., “RF Coil Element with Longitudinal and Transversal Two-Peak Field Distribution for Low SAR 7-Tesla Magnetic Resonance Imaging.”
MRI machines with up to 7T field strengths have been discussed at IMS for the last few years and have the advantage of higher resolution images. The B0 low frequency field is longitudinal and the B1 RF field is circularly polarized. It’s the RF field that interests IMS people.
Both papers dealt with the separate elements that are joined to form the circumferential coil. It’s important that as much of the power as possible is in the correct direction. Otherwise, inefficiencies show up as tissue heating. SAR was mentioned several times and at least one of the presenters discussed testing the coil design with a phantom, much as a phantom is used to evaluate SAR for cell phones.
The width of each individual structure is about 25 mm, so because it’s much smaller than the RF wavelength, the overall field appears to be continuous.
Lots of RTSA applications were highlighted at Tek's booth. An 802.11ad application was set up using a couple of Hitachi downconverters to get the signal into the 20-GHz range for the RTSA.
The latest RTSA model, the 5000 Series, is being sold as a mid-range analyzer, but its performance is close to that of the top-of-the-range 6000 model.
R&S now has 160-MHz realtime analysis capability on the Model FSW via the FSW K160R option. The instrument directly covers frequencies from 2 Hz to 50 GHz and has been upgraded to perform 600,000 FFTs/s in realtime mode. This means that the PoI is half that of the completion—about 1.8 µs vs 3.6. And, the swept tuned bandwidth also has been increased to 320 MHz, but not for RTSA mode.
The RTO scope was demonstrated performing several mixed-domain demos that implied a good dynamic range and high ENOB. The RTO has a hi-resolution mode, but it’s listed under the “decimation” menu with little datasheet information. With the built-in very fast DSP capabilities, you can define a filter to do hi-res mode than the decimation mode box-car approach.
The production test applications that NI is addressing via its FPGA capability include power servoing, ordinarily a time-consuming test that can be performed in a fraction of the time by embedding the algorithm in an FPGA. The company also demonstrated digital pre-distortion and envelope tracking. And, NI is partnering with Measuro to deal with non-linear RF and microwave measurements through use of the PXIe-5644R vector signal transceiver coupled with LabVIEW software.
Thursday June 6
On Thursday, Steve Reyes showed me a test setup capable of measuring noise figure on wafer up to 95 GHz. This has been a big problem for people working at 75 and 95 GHz, but now has been greatly simplified.
Papers on Power Amplifiers:
I attended a couple of presentations on special amplifier architectures: Motoyama, et al., “Stacked FET Structure for Multi-Band Mobile Terminal Power Amplifier Module,” and Chakrabarti and Krishnaswamy, “Design Considerations for Stacked Class-E-like mm-Wave High-Speed Power DACs in CMOS.”
In the first paper, a series of FETs was used to increase the output impedance. Ordinarily, increasing impedance isn’t the direction people take, but in this case, it facilitated better matching and improved efficiency. Good results were shown across several frequency bands.
In the other paper, the “power DAC” idea was developed. Again, FET stages were stacked, but each could be controlled to have a very small (idle) bias current that supported fast switching, totally off, or totally on. Summing the output power from the several stages gave a high overall output but also very good efficiency when most of the stages were off and only one or two were handling a small signal.
The company has improved its CMOS on sapphire process even further and claims to surpass GaAs performance. Switches made with the CMOS on sapphire process are very linear because of the high resistivity of the sapphire substrate. Rodd Novak (chief marketing officer) presented a description of the progress made from one process to the next as well as the ATE test applications the company serves. I asked about MEMS, but he thought that the performance of his switches was at least as good and being CMOS, didn’t wear out. Also, he could integrate control functions and other circuitry along with the switches.
I saw a demo of a capacitor DAC—not Peregrine's term, but it is a programmable capacitor that allows you to switch capacitance in or out to accomplish dynamic tuning, for example. The range was from 50 fF to about 10 pF.
Keith Moore (UK technical director) said that the company has more than 600 PXI switch products, but that’s still not enough. People need to do odd things with switching or they need to do them more economically. For example, he said that the high cost of a matrix is related to the width of the analog bus, so rather than offer only a couple of widths such as 8 or 16, Pickering Interfaces offers several intermediate sizes. This allows users to choose exactly what they need without paying for capacity they don’t want. And, Moore said that the latest products increased density while maintaining a 2-A switching capability. He said that a 2X further density improvement was likely in the future.
Moore commented that FET switching was improving as well as MEMS-based switches, although he didn’t expect to see MEMS used for general-purpose work—they are very sensitive to hot-switching transients.
dBm:
Mike Cagney, founder and CEO, said dBm is doing well, with a few contracts being funded that the company had pursued for two or three years. On the other hand, he thought that IMS was heavily weighted towards component vendors.
The company has a recently introduced 14-GHz reflectometer for antenna characterization. Also, a 4.5-GHz VNA has been introduced to complement the existing 1.3-GHz unit.
The company had a large booth and a small section devoted to LeCroy scopes and the SPARQ VNA. This was the first time I had seen the simultaneous 4-channel eye diagram capability introduced maybe a year ago, and it’s impressive—but you need a big monitor to make the best use of it.
I talked with Dr. Tudor Williams (senior systems engineer) about Mesuro’s new closed-loop active load pull technique. Traditional active load pull provides harmonic frequencies at appropriate phases to develop the desired impedance at the output of the DUT. The technique has advantages, such as the capability to provide gain, but because it’s a closed-loop system, it also can have unwanted oscillations. In contrast, an open loop system provides harmonics in an iterative way, stepping through the Smith Chart area of interest. There is no feedback, so there’s no oscillation. The drawback is the time taken for iterating.
The new closed loop system breaks the RF path, and is claimed to have advantages of both traditional closed and open loop approaches without the drawbacks. Dr. Williams is sending me recent technical papers on the technique.
The company highlighted its 19” rack-mounted switch-matrix solutions.
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