In this episode Shahriar takes a close look at the top-of-the-line Rigol DSA875-TG 7.5GHz Spectrum Analyzer. This unit which, offers a built in tracking generator for the full frequency range, has a portable form-factor. I offers the following performance:
9 kHz to 7.5 GHz Frequency Range
Typical -161 dBm Displayed Average Noise Level (DANL) normalized to 1 Hz
-98 dBc/Hz @10 kHz offset Phase Noise
Total Amplitude Uncertainty <0.8 dB
10 Hz Minimum Resolution Bandwidth (RBW)
The unit is tested against linearity specification as well as overload conditions. The phase noise of the unit is also verified with an external Keysight synthesizer. The instrument is used to measure OIP3, P1dB input and output matching of various amplifiers. The tracking generator is also used to measure gain and switching behavior of a WiFi extender module. The built-in functions are used to measure OBW, channel power, ACP and THD. The teardown of the unit is also presented showing excellent build quality and manufacturing.
In this episode, Shahriar repairs a few PXI module cards including a PXI-2596 Microwave Switch, a PXI-4461 Signal Analyzer and a PXI-4071 7.5 Digit FlexDMM unit. The PXI-2596 and PXI-4461 have both suffered mechanical damage to the on-board components. Some re-wiring as well as component replacement is necessary to correct the problems.
The PXI-4071 module halts the PXI system boot up entirely. The card is missing a flash memory IC and could potentially have a bad PXI bus main IC. The PXI bus IC replacement does not correct the problem. This implies a missing firmware on the flash memory IC.
In this episode Shahriar attempts the repair of a Matsusada RE-600-1.6V 1.6A power supply. This low profile power supply is intended for rack-mount application and has been likely used in a vapor deposition system before it has failed. The scent from the unit hints at capacitor failures due to thermal stress over a long period of time. The teardown of the unit reveals the low-profile construction as well as the ventilation air flow. The faulty capacitors are replaced with higher temperature rated units. Unfortunately further faults are detected and it is revealed that the main switching transistors have also failed. All part number of all ICs and control modules are either sanded off, or permanently potted. Since no schematic is available, the repair has to be temporarily put on hold.
In this episode Shahriar takes a close look at one of Keysight (Agilent) InfiniMax III active probes. The model N2802A offers 25GHz of analog bandwidth, 17.5pS of rise time and a total differential input capacitance of 32fF at 10k-Ohm input impedance. The front-end amplifier of this active probe is designed in an in-house InP process, the same process responsible for the front-end of the X-Series Keysight oscilloscopes.
The teardown of the probe shows the control circuitry in the main probe body built around a PIC 16F877 microcontroller coupled to a DAC, EEPROM memory and various high-current and precision op-amps for biasing. The main front-end microwave module reveals the InP ASIC and supporting microwave circuity. There seems to be a dual-path design to provide a large DC common-mode offset capability as well as a high-bandwidth.
In this episode Shahriar and Timo demonstrate the design methodology of an FPGA based 32×32 RGB LED matrix driver. Timo has kindly devoted some of his time to describe the block diagram and the thought process which goes into designing this type of FPGA display driver. The various components of the overall system (PLL, UART, and Display Controller) are shown along with the simulation data. The outputs of the Spartan-6 FPGA board are then measured using a Keysight S-Series oscilloscope. The design of the RGB matrix is also demonstrated using a custom clock interface sent wirelessly to the unit via Bluetooth.
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.