The Anritsu Microwave Site Master™, model S820E, is a handheld two-port cable and antenna analyzer designed for field use yet delivering benchtop performance. Five models covering 1 MHz to 8, 14, 20, 30 or 40 GHz are available. An optional VNA mode provides fully reversing S-parameter measurements. An optional vector voltmeter (VVM) mode, with standard A/B and B/A ratio capability, may be used as a drop-in vector voltmeter replacement.
Key specifications of the Site Master are:
- Dynamic range: 110 dB typical from 20 MHz to 40 GHz, 100 dB specified
- Sweep speed: ≤ 650 µs/point
- Frequency resolution: 1 Hz from 1 MHz to 40 GHz
- Simultaneous extended USB sensor transmission and error-corrected reflection measurements
- Field-proven design: explosive atmosphere MIL-PRF-28800F Section 4.5.6.3 compliant
- Coaxial and waveguide measurements
- USB/Ethernet connectivity, full remote control capability
- Intuitive, menu-driven 8.4 inch touchscreen with daylight/nighttime viewable modes
- Standard three-year warranty
Figure 1 The NLTL sampler exhibits much wider bandwidth than one using SRDs.
Two decades ago, in 1995, the world’s very first handheld one-port vector network analyzer was introduced by Anritsu. Considered unbelievable by many, the measurements were initially challenged until proven to be highly accurate and repeatable. That product still exists in many forms and is universally recognized as the de facto industry standard, known as Site Master.
The standard Site Master is ideal for applications up to 6 GHz. However, there are needs for higher frequency coverage. Until recently, no product on the market offered VNA capability beyond 26.5 GHz. The Anritsu S820E Microwave Site Master breaks through that barrier and delivers benchtop performance up to 40 GHz.
To understand how the S820E is capable of delivering up to 110 dB of dynamic range, even at 40 GHz, consider the advanced technology that is deployed inside the S820E. The traditional VNA is comprised of a source, transfer switch, couplers or bridges, and reference/measurement receivers. Measurements are typically down-converted to an intermediate frequency (IF), where the signal is processed. The most common method for conversion uses mixers. However, mixers typically do not have sufficient bandwidth to directly down-convert signals higher than just a few GHz. Higher frequency signals, which exceed the fundamental mixer band, must be down-converted using harmonics of the mixer. The disadvantage is that the conversion efficiency rapidly declines as the harmonic order increases. The consequences are reduced dynamic range, elevated noise floor and often degraded sweep frequency resolution. Very large amounts of IF gain are required to compensate for the reduced conversion efficiency, often adding undesirable side effects, such as increased noise, higher nonlinearity, additional heat and thermal drift and increased power consumption. Mixers with good high frequency performance typically perform poorly at low frequencies, so the problem is simply shifted, not resolved.
Figure 2 S820E measurement overlaid with ShockLine measurement of a 1.95 GHz bandpass filter.
An alternative method is a sampler using step recovery diodes (SRD). SRD samplers are widely deployed and offer many advantages over mixer-based methods. However, the SRD sampler method also suffers from declining down-conversion efficiency.
The most efficient down conversion method is the nonlinear transmission line (NLTL) sampler. Historically, it has been challenging to mass produce this technology with reasonable price and consistency. Anritsu engineers have successfully overcome these challenges with newly developed “VNA-on-a-chip” monolithic microwave integrated circuit (MMIC) devices. These devices are establishing new benchmarks in the high performance/price ratio for VNA instruments such as the S820E. These highly integrated MMIC devices have the performance advantages of NLTL technology and additional benefits, such as unmatched temperature stability and no degradation of frequency resolution. The extremely high conversion efficiency enables the S820E to deliver 110 dB of dynamic range up to 40 GHz. Since lower IF gain is required, longer battery life and better linearity are additional benefits. Figure 1 compares the NLTL-based sampler technology to the SRD-based sampler.
Equipped with NLTL technology, the handheld S820E is able to correlate with Anritsu’s premium VectorStar™ VNA and Anritsu’s ShockLine™ series of benchtop VNAs with uncanny precision, bringing true benchtop performance from the lab to the field. Figures 2 and 3 show examples of measurement correlation.
Figure 3 S820E measurement overlaid with VectorStar measurement of a WR28 waveguide 39.6 GHz bandpass filter. The slight variation is mainly due to the repeatability of the waveguide connection.
Figure 4 Simultaneous vector, error-corrected S11 (return loss) and USB sensor transmission measurements.
Although capable of providing benchtop quality measurements, the S820E is designed to handle the unique challenges of the field. Measurements on long transmission lines are a fine example, where the ends of the line are far apart and not reachable with conventional test port cables. Examples include communication or signaling cables that are embedded in aircraft wings or the fuselage, long waveguide runs in Navy vessels and satellite ground stations, and long microwave coaxial cable runs in the elevator shafts of high-rise office buildings. Historically, these measurements have been performed using scalar network analyzers (SNA). Detector modules could extend the transmission measurement capability using long extender cables, providing a scalar (magnitude only) response. S11 of the device being tested could also be measured using a calibrated auto-tester module. Today, VNAs have replaced SNAs for most measurements, and the SNA instrument is no longer readily available. Fortunately, the S820E can make these measurements with ease. Combining unique “USB Sensor Transmission” and vector error-corrected S11 measurement capabilities, the S820E measures both required parameters simultaneously with one user calibration. The USB sensor measurement is made using USB extenders. Anritsu provides a passive, plug-n-play USB extender kit. Users simply add a suitable length of CAT5e or CAT6 cable between the two USB extender modules. Figure 4 shows a measurement example.
The Anritsu S820E is a rugged, handheld solution, allowing users to confidently make VNA measurements in the uniquely challenging field environment and achieve benchtop performance to 40 GHz.
Anritsu
Morgan Hill, Calif.
www.anritsu.com