SRF-1016 Ver la hoja de datos (PDF) - RF Micro Devices

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SRF-1016

65MHz to 300MHz SILICON GERMANIUM IF RECEIVER

RF Micro Devices 

Preliminary

SRF-1016(Z)

The SRF-1016 is a variable gain I-Q demodulator designed for use in receiver IF sections, as shown in the figure below. It con-

sists of five subcircuits: two cascaded switched gain stages, a matched pair of mixers, and a LO quadrature generator. This

part is also available in a higher frequency version, the SRF-2016.

The gain stages are broadband differential amplifiers each with a digital control pin to set the gain. The gain control pins act

independently of each other. Since the amplifiers have approximately the same gain, setting GC1 high and GC2 low results in

approximately the same gain as setting GC1 low and GC2 high. The former setting is preferred because it offers better noise

figure. The IF input is differential with internal bias circuitry to set the common mode voltage. The use of blocking capacitors to

facilitate AC coupling is highly recommended to avoid changing the common mode voltage. Either input may be driven single-

ended if the other input is connected to ground through an AC short such as a 1000pF capacitor. This typically results in

slightly lower input P1dB.

The two matched mixers are configured with the quadrature LO generator to provide in-phase and quadrature baseband out-

puts. These can be fed through ADCs to a DSP engine, or can be fed into a low frequency 90° hybrid for image rejection. Alter-

natively, the IF signal can be extracted from the BBI port by injecting DC into the LO port.

The LO and IF ports offer a differential 50 impedance. The package (and in the case of the input port, the parallel L-R net-

work) adds inductance that tends to degrade return loss. This can easily be matched out with a series capacitor. The 27pF

capacitor on the evaluation board is appropriate for 200MHz operation; larger capacitors should be used for lower frequen-

S cies.

DESIGN LNA

RF

Filter

IF

Filter

SRF

1016

BB

Filter

BB

Filter

I

ADC

Q

ADC

Typical use for the SRF-1016 in a receiver

employing digital I/Q demodulation.

EW The SRF-1016 has high gain at UHF frequencies, so instability can result if there is poor power supply decoupling or undesired

N coupling from the input to the output. The following considerations should be observed when laying out a PC board:

Follow the general layout of the evaluation board, keeping the power supply decoupling capacitors as close to the package as

possible. The back of the package, the two ground pins and the decoupling capacitors should connect directly to ground, pref-

R erably to a large dedicated ground plane. Use the parallel L-R circuits on the input pins. Ensure that the input signal tracks are

O routed far from the output tracks. The VCC pins are not internally connected, so all must be connected together externally with

the specified decoupling capacitors.

F The figures on page 4 illustrate a typical SRF-1016’s performance with respect to temperature. Note that these numbers

include the effect of the R-L network in the IF port.

T The frequency response of the IF and LO ports is dominated by the L-R network on the input. When de-embedded, the gain and

NO P1dB response is within 0.5dB from 65MHz to 300MHz.

The SRF-1016 features immunity from changes in LO power. The gain typically changes by less than 0.6dB over a 6dB range of

LO power. Also note the excellent I/Q balance, which typically falls within 0.1dB and 1° from 65MHz to 300MHz, and varies

less than 0.05dB and 0.5° over temperature (-40 to +85C).

DS101122

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.

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