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RF2713

QUADRATURE MODULATOR/DEMODULATOR

RF Micro Devices 

RF2713

Pin Function Description (Modulator Configuration)

Interface Schematic

1

I INPUT A When the RF2713 is configured as a Quadrature Modulator, each mixer is

driven by an independent baseband modulation channel (I and Q). The

VCC

VCC

mixers can be driven single-endedly (as shown in the modulator applica-

tion circuit) or differentially. When driving single-endedly, the B Inputs (pins

1260 Ω

1260 Ω

2 and 4) should be connected to each other. This ensures that the base- INPUT A

band signals will reach each mixer with the same DC reference, yielding

INPUT B

the best carrier suppression. Note that the input impedance changes

according to the drive mode (see the mixer equivalent circuit on the previ-

ous page). The single-ended input impedance (as shown in the modulator

application circuit) is 1200Ω for each of the two inputs. In the balanced

configuration, the input impedance would be 2400Ω for each of the two

inputs.

The mixers are Gilbert Cell designs with balanced inputs. The equivalent

schematic for one of the mixers is shown on the previous page. The input

impedance of each pin is determined by the 1200Ω resistor to VCC in par-

allel with a transistor base. Note from the schematic that all four input pins

have an internally set DC bias. For this reason, all four inputs (pins 1

through 4) should be DC blocked. The capacitance values of the blocking

capacitors is determined by the baseband frequency. When driving sin-

gle-endedly, both the series (pins 1 and 3) and shunt (pins 2 and 4) block-

ing capacitors should be low impedances, relative to the input impedance.

DC bias voltages may be supplied to the inputs pins, if required, in order to

increase the amount of carrier suppression. For example, the DC levels on

the reference inputs (pins 2 and 4) may be offset from each other by add-

ing different resistor values to ground. These resistors should be larger

than 2kΩ. Note from the mixer schematic that all four input pins have an

internally set DC bias. If DC bias is to be supplied, the allowable ranges are

limited. For 5V applications, the DC reference on both I pins or both Q pins

must not go below 2.7VDC, and in no case should the DC voltage on any of

the four pins go below 2.0VDC or above 5.5VDC. IF a DC reference is to be

supplied, the source must also be capable of sinking current. If optimizing

carrier suppression further is not a concern, it is recommended that all

four inputs (pins 1 through 4) be DC blocked.

2

I INPUT B Same as pin 1, except complementary input.

See pin 1.

3

Q INPUT A Same as pin 1, except Q Buffer Amplifier.

See pin 1.

4

Q INPUT B Same as pin 3, except complementary input.

See pin 1.

5

BG OUT

Band Gap voltage reference output. This voltage output is held constant

over variations in supply voltage and operating temperature and may be

used as a reference for other external circuitry. This pin should not be

loaded such that the sourced current exceeds 1mA. This pin should be

bypassed with a large (0.1μF) capacitor.

6

I IF OUT

Connecting pins 6 and 7 to each other accomplishes the summing function

of the upconverted I and Q channels. In addition, because these outputs

are open collector type, they must be connected to VCC in order to properly

bias the Gilbert Cell mixers. Maximum gain and output power occur when

the load on these two pins is ~1200Ω. In most applications the impedance

of the next stage will be lower and a reactive impedance transforming

match should be used if maximum gain and output level are of concern.

For applications where the gain is not as critical, a 1200Ω resistor may be

added in parallel with a choke inductor. If neither gain nor output level is

critical, the inductor may be replaced with a resistor that sets the desired

source impedance to drive the next stage. If the next stage is an "open" at

DC, the blocking capacitor may be eliminated.

IF OUT

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

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

Rev A5 DS061016

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