Keysight N9321C Basic Spectrum Analyzer: 9kHz-4GHz 

Cost-effective All-in-one Solution for RF Testing

With the rapid development of wireless communications, industrial IoT, consumer electronics and other industries, RF signal testing has become a core link in the whole process of product R&D, mass production quality inspection, and equipment operation and maintenance. In the current general RF test market, high-end professional instruments deliver powerful performance but suffer from high procurement costs, while entry-level products generally have the pain points of insufficient accuracy, single function, and poor environmental adaptability. Most users struggle to find a balanced option that "meets performance requirements, is functionally scalable, and keeps costs under control".

In response to this industry demand, Keysight has launched the N9321C Basic Spectrum Analyzer. With full frequency coverage from 9kHz to 4GHz, industry-leading measurement accuracy, flexible and rich expansion capabilities, and a portable and durable industrial-grade design, it precisely meets the core test requirements of scenarios such as R&D and production of small and medium-sized enterprises, on-site equipment operation and maintenance, and university teaching and scientific research, making it a benchmark product that combines both performance and cost-effectiveness in the field of general RF testing.

1. Core Product Performance Analysis

As a basic spectrum analyzer developed by Keysight for general RF testing, all core performances of the N9321C are strictly calibrated. Under the operating conditions of meeting the calibration cycle and 30-minute warm-up after power-on, it can stably reach the nominal specifications in the full operating temperature range of 5℃ to 45℃. Its core performance is divided into three core modules, balancing measurement accuracy and practicality.

Quick Overview of Core Performance

1. Wide Frequency Coverage, High-stable Frequency and Sweep Performance

Frequency performance is the core foundation of a spectrum analyzer. N9321C achieves full-band AC coupling coverage from 9kHz to 4GHz, which completely covers the operating frequency bands of most common applications including Bluetooth, Wi-Fi, LoRa, civil broadcasting and industrial RF, and meets the test requirements of mainstream RF signals without additional expansion.

The instrument features an ultra-high frequency resolution of 1Hz, which can accurately distinguish narrowband signals and small frequency deviation signals with close frequency points, even two signals with only tens of hertz apart can be clearly identified and separated. It is equipped with a 10MHz frequency reference as standard, with an annual aging rate as low as ±1×10⁻⁶. With the optional PFR high-precision reference source, the annual aging rate can be further improved to ±1×10⁻⁷. Combined with excellent temperature stability, it can effectively reduce frequency drift during long-term use and ensure long-term consistency of test data.

At the same time, the instrument supports 0Hz zero-span mode for time-domain analysis of RF signals, with a sweep time covering an ultra-wide range from 600ns to 1000s. It supports continuous and single sweep modes, as well as multiple trigger modes such as free run, video trigger and external trigger, which can meet the conventional spectrum analysis of steady-state signals and adapt to the capture and test of pulse signals and burst signals.

2. High-fidelity Amplitude Measurement, Industry-leading Dynamic Range

Amplitude measurement accuracy directly determines the test reliability of core indicators such as RF signal power, gain and attenuation. Under the standard test environment of 20℃-30℃, the absolute amplitude accuracy of N9321C at 50MHz frequency point can reach ±0.3dB, the 95th percentile accuracy in the whole frequency band from 100kHz to 3GHz is only ±0.60dB, even in the high frequency band from 3GHz to 4GHz, the accuracy can still be controlled within ±0.65dB. The test data can be directly used as the compliance basis for product R&D and mass production quality inspection.

The instrument is equipped with a high-precision input attenuator of 0-50dB with 1dB step, which can flexibly adapt to input signals of different powers. The measurement range covers an ultra-wide range from displayed average noise level to +20dBm, which can not only capture micro-watt weak signals, but also complete the measurement of medium and high-power RF signals; At the same time, it has a complete input protection mechanism, which can withstand up to +33dBm continuous input power and ±50VDC DC voltage, effectively avoiding instrument damage caused by misoperation.

In terms of dynamic range performance, when N9321C is equipped with optional P04 preamplifier, the normalized displayed average noise level in 10-500MHz frequency band is as low as -161dBm, which can accurately capture the weak transmission signal of low-power RF modules and hidden spurious interference; the second harmonic distortion in 50MHz to 4GHz frequency band is lower than -65dBc, and the third-order intercept point can reach up to +15dBm, which can accurately restore the non-linear characteristics of RF devices, providing reliable data support for performance optimization of components such as amplifiers and filters.

3. Flexible adjustable bandwidth filtering system to meet test requirements of multiple scenarios

N9321C is equipped with a complete resolution bandwidth (RBW) and video bandwidth (VBW) adjustment system. RBW covers 10Hz to 3MHz, and VBW covers 1Hz to 3MHz. Both adopt the industry-standard 1-3-10 adjustment sequence, and the operation logic conforms to the usage habits of RF test personnel, which can be flexibly switched according to test requirements.

The RBW filter of the instrument adopts Gaussian digital filtering design, and the 60dB/3dB bandwidth shape factor is less than 5:1, which can effectively suppress the interference of adjacent channel signals and ensure the accuracy of in-band signal measurement; with optional EMC module, it directly supports CISPR standard EMI bandwidth of 200Hz, 9kHz, 120kHz, 1MHz, and is equipped with a quasi-peak detector. It can complete pre-compliance EMC test of electronic equipment without purchasing additional special equipment.

II. On-demand customizable optional function system

One of the core advantages of N9321C is its complete original optional function modules. Users can flexibly select corresponding functions according to their own test scenarios and needs, without paying for redundant functions, realizing a customized solution of "basic model meets core needs, optional modules expand special capabilities", effectively controlling the procurement and use cost of test equipment. Core optional modules can be divided into three categories:

1. Basic performance upgrade options

These options are mainly used to improve the basic measurement performance of the instrument, adapting to scenarios with higher requirements for test accuracy:

P04 Preamplifier: covering the full frequency band from 9kHz to 4GHz, with a nominal gain of 25dB from 100kHz to 4GHz. It can greatly reduce the displayed average noise level of the instrument, improve the ability to capture weak signals, and meet the test requirements of low-power RF modules and small spurious signals;

PFR High-precision Frequency Reference: it improves the annual aging rate of the 10MHz reference source from ±1×10⁻⁶ to ±1×10⁻⁷, optimizes the frequency stability in the full temperature range, and adapts to laboratory test scenarios requiring long-term high frequency accuracy.

2. Special test function expansion options

These options can expand the test capability of the instrument, allowing a single spectrum analyzer to realize the functions of multiple special test equipment, greatly reducing the equipment investment for multi-scenario testing:

EMC Electromagnetic Compatibility Test Module: supports CISPR standard EMI bandwidth and quasi-peak detector, meeting the pre-compliance test requirements of conducted emission and radiated emission of electronic equipment. It is a cost-effective choice for EMC rectification of household appliances, industrial equipment and consumer electronics enterprises;

TG4 Tracking Generator + RM4 Reflection Measurement Module: the TG4 module covers 5MHz to 4GHz frequency band and can achieve signal tracking output. When combined with the RM4 module, it can complete return loss, voltage standing wave ratio (VSWR) and insertion loss test of RF amplifiers, filters, antennas and cables, replacing special vector network analyzers, and adapting to the performance detection of RF components;

AMA/DMA Modulation Analysis Module: the AMA module supports AM/FM analog modulation signal analysis from 10MHz to 4GHz, and the DMA module supports ASK/FSK digital modulation signal analysis from 2.5MHz to 4GHz. It can accurately measure core indicators such as modulation depth, frequency deviation and symbol rate, adapting to the modulation performance test of wireless communication modules;

TMG Time-Gated Sweep Module: It supports external and periodic timer gate sources, enables gated spectrum analysis of pulse signals and burst signals, and is suitable for testing time-division multiplexed RF signals such as radar and walkie-talkies.

3. Options for Improving Test Efficiency and Management

These options are mainly used to optimize test workflows and improve the efficiency of batch testing and automated testing, making them ideal for mass production quality inspection and laboratory batch testing scenarios:

TPN Task Planner: A single file can edit up to 20 test tasks, and supports three execution modes: automatic, manual, and manual-on-fault. When paired with Keysight's dedicated PC software, it enables fully automated execution of test workflows, and test data can be exported in batches, greatly reducing manual operations and improving the efficiency of mass production quality inspection.

SCN Channel Scanner Module: It supports three scanning modes: Top N, Bottom N, and List. It can monitor 1-20 channels simultaneously and generate histograms and time trend charts, which is suitable for signal monitoring and troubleshooting of multi-channel wireless devices.

PWM/PWP Power Sensor Support Module: It is compatible with Keysight U2000 Series and U2020/X Series USB power sensors, extends the frequency range of power measurement up to 40GHz, with a dynamic range covering -60dBm to +44dBm, enabling RF power measurement with wider frequency band and higher accuracy.

III. Full-Scenario Adaptation to Cover Multi-Industry Test Requirements

The performance and functional design of the N9321C are fully built around the actual scenarios of general RF testing. From the constant temperature environment of the laboratory to complex working conditions in industrial sites, from R&D debugging to mass production quality inspection, it can provide stable and reliable test solutions, and it is core-adapted for five major application scenarios:

1. RF R&D and Mass Production Quality Inspection for Small and Medium-Sized Enterprises

For small and medium-sized enterprises manufacturing wireless communication modules, consumer electronics, and industrial IoT devices, core indicators such as frequency accuracy, transmit power, spurious interference, and harmonic distortion need to be accurately tested during the R&D phase, while test efficiency and cost control need to be balanced during the mass production phase.

The high-precision measurement capability of the N9321C fully meets the debugging requirements in the R&D phase. Its flexible optional modules allow customizing test capabilities according to product types, and when paired with the TPN Task Planner, it enables automated batch testing during mass production. There is no need to invest heavily in multiple dedicated devices, so it can control the budget while ensuring full-process coverage of product testing.

2. EMC Pre-Compliance Testing for Electronic Devices

Electronic devices must pass mandatory EMC certification before they can be launched. However, most enterprises lack professional EMC test equipment during the product R&D stage, which makes it impossible to troubleshoot electromagnetic interference problems in advance. This easily leads to failure of formal certification and delayed product launch. Dedicated EMC test systems have extremely high procurement costs, which are unaffordable for small and medium-sized enterprises.

When the N9321C is equipped with an EMC option, it can fully meet the pre-compliance testing requirements of CISPR standards. It can accurately identify the frequency point and amplitude of electromagnetic interference of the product, provide reliable data support for circuit rectification, avoid certification risks in advance, and greatly reduce the certification cycle and rectification cost of the product. It is a cost-effective choice for early-stage EMC testing for small and medium-sized enterprises.

3. On-Site Maintenance for Communication and Industrial Equipment

For on-site maintenance of communication base stations, radio and television transmission equipment, and industrial RF control systems, the core pain point is the complex on-site environment, which places extremely high requirements on the portability, environmental adaptability, and power-on response speed of the instrument. Traditional benchtop spectrum analyzers are large and heavy, difficult to carry to outdoor sites, while portable instruments generally suffer from insufficient accuracy and single functions.

The N9321C has a net weight of only 7.9kg and a compact size for easy portability. It supports 100-240VAC wide voltage input, and can be adapted to outdoor power supply scenarios via mobile power bank and vehicle power supply. With a wide operating temperature range of 5℃ to 45℃, coupled with an industrial design that is shock and vibration resistant, it can adapt to various complex on-site environments. It can reach the nominal measurement accuracy within 30 minutes after power-on, quickly locate faults such as frequency drift, power reduction, and spurious interference of the equipment, and greatly improve the efficiency of on-site maintenance.

4. RF Teaching and Basic Scientific Research in Colleges and Universities

For RF basic teaching in electronic information, communication engineering and other majors in colleges and universities, multiple spectrum analyzers need to be deployed in batches. They are required to cover the basic teaching content of spectrum analysis and RF measurement, be simple to operate for students, and at the same time keep procurement budget and later maintenance costs under control.

The operating interface of the N9321C follows the general industry logic, covers all basic functions, and can perfectly meet the teaching requirements of basic radio frequency experiments, course design, and graduation projects; The instrument features low failure rate and comes with a 5-year original factory warranty, which greatly reduces the later maintenance cost of the laboratory, and its cost-effective positioning is also suitable for large-volume procurement and configuration by colleges and universities; Meanwhile, the abundant optional modules can also meet the basic scientific research needs of teachers and students, achieving dual adaptation for teaching and scientific research.

5. Performance Testing of RF Components

For manufacturers of components such as RF amplifiers, filters, antennas, and cables, it is required to quickly test core performance indicators such as gain, loss, and VSWR of components during mass production. The traditional solution requires simultaneous configuration of a spectrum analyzer and a network analyzer, which leads to high equipment investment and complicated test procedures.

After the N9321C is equipped with the optional TG4 tracking generator and RM4 reflection measurement module, it can complete the scanning test of the full frequency range from 5MHz to 4GHz within 2 seconds, and accurately measure indicators such as reflection loss, insertion loss, and VSWR of components. One instrument can complete the full performance test of components, greatly simplifying the test procedure and reducing the equipment investment in production.

IV. Comparison with products of the same category, highlighting core advantages

In the entry-level basic spectrum analyzer market covering the 9kHz to 4GHz frequency band, compared with other products at the same positioning, the N9321C has four irreplaceable core advantages:

1.Better measurement accuracy and environmental adaptability. For entry-level products at the same price range, the amplitude accuracy at the 50MHz frequency point is mostly above ±0.5dB, and most of them can only achieve the nominal accuracy in a room temperature environment of 20℃-30℃. When the ambient temperature changes, the measurement error will increase significantly; while the N9321C can achieve an amplitude accuracy of ±0.3dB, and can stably meet the nominal specifications throughout the full operating temperature range of 5℃-45℃. Whether it is the constant temperature environment of the laboratory or the variable temperature working condition of the industrial site, it can ensure the reliability of test data.

2.Higher scalability and long-term use value. Most entry-level products at the same price range only have basic spectrum analysis functions, with very few optional modules, and cannot expand special test capabilities. When users have new test requirements, they can only purchase additional new test equipment; while the N9321C provides more than ten optional original factory modules, covering all from performance upgrade to special test functions. One instrument can implement multiple functions such as spectrum analysis, network analysis, EMC test, modulation analysis, etc., and can be flexibly upgraded according to changes in user requirements, resulting in a much lower long-term use cost than products at the same price range.

3.Better weak signal capture and dynamic range performance. When the preamplifier is turned on for products at the same price range, the displayed average noise level (DANL) can only reach about -140dBm, which has limited capability for capturing weak signals; while when the preamplifier of the N9321C is turned on, the DANL can be as low as -161dBm, and the third-order intercept point can reach up to +15dBm. Whether it is the capture of weak small signals or the spurious identification in a strong signal environment, the capability far exceeds that of products at the same price range.

4.More complete brand guarantee and after-sales service. As a leading brand in the global test and measurement industry, Keysight has decades of accumulation in RF test technology, and has a complete product quality control and technical support system; the N9321C comes with an original factory warranty. Meanwhile, Keysight has multiple service centers across the country, which can provide professional calibration and maintenance services, providing comprehensive guarantee for the long-term stable use of the instrument.

Closing Guide

If you are looking for a 9kHz-4GHz frequency band spectrum analyzer that balances measurement accuracy, functional scalability and cost performance, and want to know more about the option configuration scheme and actual test cases that are more suitable for your own test scenario, or need to customize a dedicated RF test solution, please feel free to contact us. Contact Us

 Contact Us>>