Block Diagram Theory of Operation

Block Diagram 2

A12 Pulse Attenuator

In addition to 0.3 GMSK modulation, the RF signals must also be pulse modulated because the GSM system uses TDMA (time division multiplexing). The function of the A12 Pulse Attenuator assembly is to pass the RF output signal with 0 dB, 30 dB or > 80 dB of attenuation. The A12 Pulse Attenuator assembly allows “straight through” operation to simulate the RF carrier ON or it provides >80 dB of attenuation to turn the RF carrier OFF. In addition to these two functions, the A12 Pulse Attenuator assembly can provide a calibrated 30 dB of attenuation. This is used to test a radios ability to recover a weak signal with other high power signals in adjacent time slots.

The diagnostics procedures check this assembly by using the internal RF spectrum analyzer. The pulse attenuator itself is solid state and highly reliable. Diagnosing the attenuator requires many other assemblies in the HP/Agilent 8922. Diagnostic failures of the Pulse Attenuator could also be caused by the A23 Input, A11 Receiver Mixer, A16 Receiver, A17 Step Loop B, or A18 Spectrum Analyzer assemblies, or a missing LO cable on the rear panel (early instruments).

A23 Input

A24 High Power Attenutor

The A23 Input assembly is both the input for the Signal Analyzer section and the final output from the Signal Generator section. For additional information on how the A23 Input assembly is used in the signal analyzer, refer to the Block Diagram 1 discussion.

The RF output signal is received from the A12 Pulse Attenuator assembly. The A23 Input assembly has a step attenuator (5 dB/step) that can attenuate the RF signal up to 125 dB. The A23 Input assembly also contains a switch to select the proper output port. For high output levels, the port AUX RF OUT is available. For most operations, the RF signal is routed to the RF IN/OUT port and connected directly to a radio or transmitter. The radios are “duplex”, meaning they simultaneously transmit and receive at different frequencies. The most common setup is to have the HP/Agilent 8922 Signal Generator routed to the RF IN/OUT connector to simulate a base station and is “transmitting” to the radio-under-test. At the same time, the radio-under-test is “transmitting” to the HP/Agilent 8922 Signal Analyzer at a frequency offset by 45 MHz. This signal comes in the HP/Agilent 8922 RF IN/OUT connector and is routed to the Signal Analyzer section.

The 14 dB (8 dB with the HP/Agilent 8922F,H,M,S) A24 High Power Attenuator assembly is shown on Block Diagram 1 inside the A23 Input block. It is actually external to the Input Module and provides 14 dB attenuation of all signals going into or coming out of the RF IN/OUT connector on the front panel.

Diagnostic procedures individually check that all the step attenuator switches provide attenuation, although the accuracy of this measurement is limited. A connectivity check is provided with the diagnostics to verify the connections going into and out of the A23 Input assembly. This section is the most likely cause of output level accuracy problems, especially “hard failures” where the output is incorrect by 5 to 20 dB (indicating an attenuator pad has failed).

14-13

Page 208 Page 210
Page 209
Image 209
Agilent Technologies 8922 manual A12 Pulse Attenuator, A23 Input A24 High Power Attenutor
Page 208 Page 210

8922 specifications

Agilent Technologies 8922 is a versatile and robust mobile communication test set, designed to fulfill the demanding requirements of wireless device manufacturers and service providers. Primarily focused on mobile radio communications, the 8922 provides a comprehensive solution for testing a wide array of signaling standards and technologies, making it essential in the rapidly evolving telecommunications landscape.

One of the standout features of the Agilent 8922 is its support for multiple wireless standards, including GSM, GPRS, EDGE, WCDMA, and HSPA. This makes the device an ideal choice for testing mobile devices that operate on different generations of cellular networks. Additionally, the 8922 is equipped with advanced measurement capabilities, allowing users to perform key performance indicators assessments, such as power, modulation quality, and spectral emission analysis, ensuring devices meet stringent regulatory and performance standards.

The 8922 is designed with an intuitive user interface that simplifies the setup and execution of tests. It features a large color display, making it easier for users to view test results and navigate through various functions. The built-in automation capabilities enable seamless integration into production environments, where efficiency and repeatability are crucial for high-volume testing.

Technologically, the Agilent 8922 incorporates advanced signal processing algorithms, which enhance its measurement accuracy and speed. The device's architecture allows for real-time analysis of signals, enabling users to identify issues quickly and efficiently. This is particularly important in the realm of mobile communications, where time-to-market is critical for competitive advantage.

Another significant characteristic of the 8922 is its flexible configuration options. Users can customize the test set with different hardware and software modules to suit specific testing needs. This scalability ensures that the 8922 remains relevant as wireless technologies evolve and new standards emerge.

In conclusion, the Agilent Technologies 8922 is an indispensable tool for professionals engaged in the testing of mobile communications devices. Its broad support for multiple standards, advanced measurement capabilities, user-friendly design, and flexibility make it a top choice in the telecommunications testing community. As the mobile communication industry continues to advance, the 8922 stands out as a leading solution for ensuring that devices meet quality and performance expectations.
Top Page Image Contents