The Digital Quadrature Tuner (DQT) provides many of the

functions required for digital demodulation. These functions

include carrier LO generation and mixing, baseband

sampling, programmable bandwidth filtering, baseband AGC,

and IF AGC error detection. Serial control inputs are provided

which can be used to interface with external symbol and

carrier tracking loops. These elements make the DQT ideal

for demodulator applications with multiple operational modes

or data rates. The DQT may be used with HSP50210 Digital

Costas Loop to function as a demodulator for BPSK, QPSK,

8-PSK OQPSK, FSK, FM, and AM signals.

The DQT processes a real or complex input digitized at rates

up to 52 MSPS. The channel of interest is shifted to DC by a

complex multiplication with the internal LO. The quadrature

LO is generated by a numerically controlled oscillator (NCO)

with a tuning resolution of 0.012Hz at a 52MHz sample rate.

The output of the complex multiplier is gain corrected and fed

into identical low pass FIR filters. Each filter is comprised of a

decimating low pass filter followed by an optional

compensation filter. The decimating low pass filter is a 3

stage Cascaded-Integrator-Comb (CIC) filter. The CIC filter

can be configured as an integrate and dump filter or a third

order CIC filter with a (sin(X)/X)3 response. Compensation

filters are provided to flatten the (sin(X)/X)N response of the

CIC. If none of the filtering options are desired, they may be

bypassed. The filter bandwidth is set by the decimation rate of

the CIC filter. The decimation rate may be fixed or adjusted

dynamically by a symbol tracking loop to synchronize the

output samples to symbol boundaries. The decimation rate

may range from 1-4096. An internal AGC loop is provided to

maintain the output magnitude at a desired level. Also, an

input level detector can be used to supply error signal for an

external IF AGC loop closed around the A/D.

The DQT output is provided in either serial or parallel formats

to support interfacing with a variety DSP processors or digital

filter components. This device is configurable over a general

purpose 8-bit parallel bidirectional microprocessor control bus.

Features

• Input Sample Rates to 52MSPS

• Internal AGC Loop for Output Level Stability

• Parallel or Serial Output Data Formats

• 10-Bit Real or Complex Inputs

• Bidirectional 8-Bit Microprocessor Interface

• Frequency Selectivity <0.013Hz

• Low Pass Filter Configurable as Three Stage CascadedIntegrator-Comb (CIC), Integrate and Dump, or Bypass

• Fixed Decimation from 1-4096, or Adjusted by NCO

Synchronization with Baseband Waveforms

• Input Level Detection for External IF AGC Loop

• Designed to Operate with HSP50210 Digital Costas Loop

• 84 Lead PLCC

Applications

• Satellite Receivers and Modems

• Complex Upconversion/Modulation

• Tuner for Digital Demodulators

• Digital PLLs

• Related Products: HSP50210 Digital Costas Loop;

A/D Products HI5703, HI5746, HI5766

• HSP50110/210EVAL Digital Demod Evaluation Board