ОБЩЕЕ ОПИСАНИЕ

The ADL5960 is a wideband, small form factor vector network analyzer front end consisting of a resistive bidirectional bridge, downconversion mixers, programmable IF amplifiers and filters, and a highly flexible local oscillator (LO) interface. The bridge provides >14 dB of directivity up to 17 GHz. The primary transmission line from RFIN to RFOUT is wideband matched to 50 Ω with only 1.1 dB loss at low frequencies, increasing to 1.8 dB loss at 20 GHz.

The ADL5960 supports several different LO interface configurations that simplify the clocking design of a vector network analyzer (VNA) solution as well as the interfacing of the device to an analog-to-digital converter (ADC). The frequency divider and multipliers in the LO interface enable measurement sweeps beyond the operating frequency range of the LO source, enabling operation over the full 20 GHz frequency range of the ADL5960 using a 6 GHz synthesizer. The IF frequency offset mixer, driven through the offset interface formed by the OFP and OFM pins, enables further simplification by allowing the swept RF and LO interfaces to share the same frequency source. The frequency of the IF output signals is then determined by the low-frequency source driving the OFP/OFM interface. When this interface is driven at the ADC sample frequency with the divide by 4 enabled, it automatically centers the IF output signal in the first Nyquist zone.

The IF filters with programmable bandwidth and IF amplifiers with individually programmable gain enable simultaneous dynamic range optimization of the IF output signals of the forward channel (IFFP, IFFM) and reverse channel (IFRP, IFRM). The IF amplifiers have an adjustable output common-mode level, sufficient drive capability, and wide output voltage swing to enable direct interfacing to a wide range of ADCs.

All configurations and functions in the ADL5960 are fully programmable through a 3-wire serial peripheral interface (SPI). The ADL5960 is offered in a 3 mm × 4 mm, 26-lead land grid array(LGA) package.

 

ТЕОРИЯ ЭКСПЛУАТАЦИИ

The ADL5960 is designed to enable broadband multiport network analyzer solutions in a small footprint.The ADL5960 is built around an integrated broadband bidirectional resistive bridge and coupled to broadband dual downconversion mixers. The differential IF outputs of the mixers are passed through low-pass filters with SPI-programmable bandwidth and IF amplifiers with individually SPI-programmable gain.

The LO interface to the mixers supports multiple SPI-programmable configurations, and is designed to simplify the frequency plan in a vector network analyzer application. The LO interface contains frequency multipliers and dividers that enable a wider frequency range of operation than supported by the LO signal source itself.

A second input to the LO interface, the offset interface formed by the OFP and OFM pins, enables a zero-offset operating mode with greatly simplified frequency plan. In this mode, only a single swept high-frequency signal source is needed, driving both the RF and LO interfaces of the ADL5960. The signal supplied to the OF interface controls the frequency of the IF output signal as it mixes with the LO signal supplied to the LOP/LOM interface before driving the downconversion mixers.

Multiple ADL5960 devices can be phase synchronized and operated simultaneously, which enables the construction of small footprint multiport network analyzers using one ADL5960 device per network analyzer port.

 

OF INTERFACE

Further simplification of the VNA configuration can be achieved by employing the differential offset frequency (OF) interface. In this configuration, a single swept source can be used to drive the RF and LO interfaces at the same frequency (zero frequency offset), while the IF output frequency is set by the signal applied to the OF interface. To enable the offset mixer, clear Bit 4 in Register 0x20 and program the OFMODE bit field in Bits[3:2]. The offset frequency input interface, when enabled, contains a programmable divider with ratios of 1, 2, and 4.