In this episode Shahriar repairs a Noise-XT 2MHz – 7GHz Ultra-Low Phase-Noise Clock Synthesizer. The instrument’s history indicates that it has suffered a fall from a work table. After a lot of difficulty, the instrument control software was found so that the unit can be tested.
Initial tests reveal that a very small output is present, however nearly 40dB below the desired value. The unit teardown shows an architecture based on dual Analog Devices DDS 14-bits DACs in conjunction with a Z-COMM VCO and a series of dividers & frequency multipliers. A detailed analysis of the unit is presented.
RF and analog measurements indicate that the RF connector is not making adequate contact with the final trace of the RF output. This explains the low output power. This problem is resolved by replacing the SMA connector entirely. The device output power, frequency accuracy, stability as well as cross-correlation phase-noise measurements are presented.
In this episode Shahriar reviews the top-of-the-line Tektronix 6-Series Oscilloscope. This 4-channel instrument offers 8-GHz of bandwidth at 25GS/s on all channel independently. Tektronix has made great strides in offering low-noise front-end custom ASICs combined with hardware digital down-conversion built into the core of the 6-Series. This enables advanced triggering across in both time and frequency domains as well as multi-domain correlated measurements.
This review is organized as follows:
00:06 – Introductions
01:42 – Instrument design, front and back panels
03:34 – Full acquisition board teardown, analysis and architecture
18:11 – PLL Experiment: Spectrum View, advanced triggering, PLL characterization and debugging
38:33 – Backplane Communication: Jitter analysis, eye diagrams, jitter composition, cross-talk
49:24 – Concluding remarks
In this episode Shahriar reviews the long awaited Signal HoundSM200C/B Real-Time 100kHz – 20GHz Real-Time Spectrum Analyzer:
The SM200C is a high-performance spectrum analyzer and monitoring receiver with a 10 Gigabit Ethernet SFP+ port, enabling the SM200C to communicate with a PC over long distances using a fiber optic cable. Designed for remotely-located accurate RF data analysis at the lowest cost possible, the SM200C features:
160 MHz instantaneous bandwidth I/Q streaming over 10GbE
SFP+ port for fast, long-distance communication with a PC using an optic cable
Device control and data transfer occurs via SFP+ connection, not USB
Tunes from 100 kHz to 20 GHz
Sweeps at 1 THz/sec at 30 kHz RBW
110 dB of dynamic range
Ultra-low phase noise
GPIO port antenna switching
The SM200B offers a USB 3.0 PC interface with 40MHz of instantaneous I/Q streaming. Furthermore, the SM200B includes a full 2-second of internal memory at 160MHz of capture bandwidth which an be accessed through the API.
The review is organized as follows:
00:00 – Introduction
00:49 – Overview, build quality and detailed specifications
05:51 – Full teardown, analysis and system architecture
18:00 – 10GbE PC interface using M.2 Key to PCIe converter
19:22 – Experiment #1: FMCW signal analysis, GUI overview & 160MHz capture capabilities
31:33 – Experiment #2: Interfering hunting, FM-versus-time, frequency hopping & advanced triggering
41:32 – Experiment #3: Digital demodulation, phase-noise & equalization
46:02 – Other GUI capabilities, mask & EM compliance, API
47:20 – Concluding remarks
In this episode Shahriar discusses some of the concerns surrounding the 5G Cellular Wireless Technology. It is important to understand the technology and the history of why 5G is unique in some ways compared with 4G LTE.
The evolution of cellular wireless technology is briefly discussed alongside with dangers of electromagnetic radiation across the entire spectrum. 5G mm-wave beam-forming technology is explored and the actual RF power levels at ground level is computed. Finally some questions about science and technology are discussed.
Perhaps this is the quote which captures my feelings toward this whole situation:
“I worry that, especially as the Millennium edges nearer, pseudoscience and superstition will seem year by year more tempting, the siren song of unreason more sonorous and attractive. Where have we heard it before? Whenever our ethnic or national prejudices are aroused, in times of scarcity, during challenges to national self-esteem or nerve, when we agonize about our diminished cosmic place and purpose, or when fanaticism is bubbling up around us – then, habits of thought familiar from ages past reach for the controls. The candle flame gutters. Its little pool of light trembles. Darkness gathers. The demons begin to stir.”
– Carl Sagan, The Demon-Haunted World: Science as a Candle in the Dark
The instrument does provide an RF output signal. However, there is also a large DC offset voltage present at the output RF port which changes depending the frequency band. The DC voltage is present even when the output RF signal is disabled. Furthermore, the OCXO of the instrument is defective and does not produce a 10MHz output signal.
The block diagram of the PSG is examined in details with emphasis on the final attenuator, coupler and doubler RF decks. Interestingly enough the output offset is traced all the way back to the Modulator Filter block. The teardown of the module reveals a series of PIN diode switches and after some investigation the fault is traced to a damaged PIN diode on the sub-3.2GHz path. Since the diode can’t be easily replaced, the control voltage to the diode is disabled instead which removed the DC offset problem.
The OCXO teardown reveals that during a prior repair, the oscillator module has been damages and torn off the PCB. New pins are added to the oscillator module which returns the crystal back to working condition. The performance of the PSG is verified using a spectrum analyzer and frequency counter.
The Signal Path (TSP) is an electrical engineering video blog for industry professionals, students and hobbyists. TSP is a non-for-profit website dedicated to provide free education spanning a wide range of electrical engineering topics. Equipment reviews, tutorials and repair videos are posted regularly.