The Digital Down Converter (DDC) is a single chip

synthesizer, quadrature mixer and lowpass filter. Its input

data is a sampled data stream of up to 16 bits in width and

up to a 75 MSPS data rate. The DDC performs down

conversion, narrowband low pass filtering and decimation to

produce a baseband signal.

The internal synthesizer can produce a variety of signal

formats. They are: CW, frequency hopped, linear FM up

chirp, and linear FM down chirp. The complex result of the

modulation process is lowpass filtered and decimated with

identical real filters in the in-phase (I) and quadrature (Q)

processing chains.

Lowpass filtering is accomplished via a High Decimation

Filter (HDF) followed by a fixed Finite Impulse Response

(FIR) filter. The combined response of the two stage filter

results in a -3dB to -102dB shape factor of better than 1.5.

The stopband attenuation is greater than 106dB. The

composite passband ripple is less than 0.04dB. The

synthesizer and mixer can be bypassed so that the chip

operates as a single narrow band low pass filter.

The chip receives forty bit serial commands as a control

input. This interface is compatible with the serial I/O port

available on most microprocessors.

The output data can be configured in fixed point or single

precision floating point. The fixed point formats are 16,

24, 32, or 38-bit, two’s complement, signed magnitude, or

offset binary.

The circuit provides an IEEE 1149.1 Test Access Port.

Features

• 75 MSPS Input Data Rate

• 16-Bit Data Input; Offset Binary or 2’s Complement

Format

• Spurious Free Dynamic Range Through Modulator

>102dB

• Frequency Selectivity: <0.006Hz

• Identical Lowpass Filters for I and Q

• Passband Ripple: <0.04dB

• Stopband Attenuation: >104dB

• Filter -3dB to -102dB Shape Factor: <1.5

• Decimation Factors from 32 to 131,072

• IEEE 1149.1 Test Access Port

• HSP50016-EV Evaluation Board Available

Applications

• Cellular Base Stations

• Smart Antennas

• Channelized Receivers

• Spectrum Analysis

• Related Products: HI5703, HI5746, HI5766 A/Ds