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Spectrum Analyzers for High Frequency Point-to-point and Point-to-multipoint Networks

A spectrum analyzer that can be used to verify the performance of a local multipoint distribution service transceiver's transmitter is featured on this month's cover

March 1, 1998
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Spectrum Analyzers for High Frequency Point-to-point and Point-to-multipoint Networks

Anrtisu Co.
Richardson, TX

The world of microwave radio continues to add exciting opportunities to the telecommunications market. With the advent of digital microwave technology, manufacturers now are providing point-to-multipoint systems that offer digital voice and data distribution for private networks in place of more expensive wireline transmission.

A more recent technology that is creating a great deal of excitement is local multipoint distribution service (LMDS). LMDS is a two-way broadband technology operating at 25 to 31 GHz that allows network integrators and communications service providers to offer a wide range of services to homes and businesses quickly and inexpensively. These services include high speed Internet access, real-time multimedia file transfer, remote access to corporate local area networks, interactive video, video on demand, video conferencing and telephony. Several microwave radio and system manufacturers are developing LMDS equipment for the US market. One of the greatest needs for manufacturers preparing to compete in this emerging and fast-paced industry is quality test equipment, such as a spectrum analyzer that can verify the performance of the transmitter of the LMDS transceiver.

The models MS2665C and MS2667C spectrum analyzers are poised to take advantage of this growing market of high frequency point-to-point and point-to-multipoint networks. These instruments provide the performance and built-in functionality required to perform the necessary measurements of these networks at an affordable price.

The models MS2665C and MS2667C spectrum analyzers cover the 9 kHz to 21 GHz and 9 kHz to 30 GHz frequency ranges, respectively. Extended frequency coverage soon will be added to this platform to address the LMDS market. For mm-wave applications, extended coverage to 100 GHz is provided using external mixers.

Housed in a portable, lightweight package, these units are suitable for use in the maintenance of RF base stations and microwave radios. However, performance has not been sacrificed since both instruments have the specifications necessary for manufacturing or research and development.

The MS2665C analyzer features phase noise performance of £-100 dBc/Hz at 1 GHz and £-94 dBc/Hz at 21 GHz. Noise floor performance is £ -115 dBm at 1 GHz and £ -98 dBm at 21 GHz. Phase noise performance of the model MS2667C is £-95 dBc/Hz at 1 GHz and £ -83 dBc/Hz at 30 GHz. The unit offers noise floor performance of £-115 dBm at 1 GHz and £-91 dBm at 30 GHz. Optional narrow resolution bandwidths (30, 100 and 300 Hz) may be added to both instruments as an option to improve sensitivity.

Such specifications are necessary when analyzing the LMDS bandwidth, which is similar to other RF networks in that it is divided into channels with bandwidths that may vary from 100 kHz to 40 MHz, depending on network requirements. As a result, several measurements must be made to verify the transmitter channel performance, including channel power and bandwidth, adjacent-channel leakage power (or adjacent-channel power) and noise power.

Channel power and bandwidth must be measured for some (if not all) of the possible channel bandwidths used by the transceiver. Adjacent-channel leakage power verifies that the power in each channel does not leak beyond a tolerable threshold on adjacent channels. If this leakage is too high, harmful interference is introduced that impedes transmission on adjacent channels. Noise power is a measurement of the noise within a channel when a signal is not being transmitted, or a measurement of noise on the receive channels. Additional measurements include frequency stability and phase noise of the LO as well as spurious responses of the carrier signal.

The MS2665C and MS2667C spectrum analyzers perform all of these measurements. Built-in measurement capability includes channel power, adjacent-channel power, occupied bandwidth, carrier-to-noise ratio and noise power. A frequency counter also is built into each analyzer. Table 1 lists the spectrum analyzer's key specifications.

Table I
Key Specification

 

MS2665C

MS2667C

Frequency range

9kHz to 21 GHz

9kHz to 30 GHz

Phase noise at 10kHz offset
(dBc/Hz)

£ -100

£ -95

Noise floor (dBm)

£ -115

£ -115

Maximum dynamic range (dB)

110

110

Total level accuracy (dB)

± 2.3

± 2.3

All data can be stored on disk via a built-in Personal Computer Memory Card International Association-compatible memory card reader. In addition, general-purpose interface bus (GPIB) and RS-232C interfaces are standard for remote control operation. A parallel interface can replace the GPIB for output to a printer.

These spectrum analyzers are the latest versions in the MS2660 series. Previous models in the platform include a 3 GHz version that addresses the personal communications service (PCS) market and an 8.1 GHz version for the development of point-to-point radios at 4, 6 and 8 GHz, and for meeting harmonic measurement requirements at PCS frequencies. With the introduction of the microwave models, coverage is provided for microwave radio development up to and exceeding 40 GHz as well as for mm-wave applications. Prices for the models MS2665C and MS2667C spectrum analyzers start at $25,000.

Anritsu Co.,
Richardson, TX
(800) 267-4878.

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