hsp50214 Intersil Corporation, hsp50214 Datasheet - Page 6

• Manufacturer Part Number: hsp50214
• Description: Programmable Downconverter
• Manufacturer: Intersil Corporation

Functional Description
The HSP50214 Programmable Downconverter (PDC) is an
agile digital tuner designed to meet the requirements of a
wide variety of communications industry standards. The
PDC contains the processing functions needed to convert
sampled IF signals to baseband digital samples. These func-
tions include LO generation/mixing, decimation filtering, pro-
grammable FIR shaping/bandlimiting filtering, re-sampling,
automatic gain control (AGC), frequency discrimination and
detection as well as multi-chip synchronization. The
HSP50214 interfaces directly with a DSP microprocessor to
pass baseband and status data.
A top level functional block diagram of the HSP50214 is
shown in Figure 1. The diagram shows the major blocks and
multiplexers used to reconfigure the data path for various
architectures. The HSP50214 can be broken into 13 sec-
tions: Synchronization, Input, Input Level Detector, Carrier
Mixer/Numerically Control Oscillator (NCO), CIC Decimating
Filter, Halfband Decimating Filter, 255-Tap Programmable
FIR Filter, Automatic Gain Control (AGC), Resampler/Half-
band Filter, Timing NCO, Cartesian to Polar Converter, Dis-
criminator, and Output sections. All of these sections are
configured through a microprocessor interface.
The HSP50214 has three clock inputs; two are required and
one is optional. The input level detector, carrier NCO, and CIC
decimating filter sections operate on the rising edge of the
input clock, CLKIN. The halfband filter, programmable FIR fil-
ter, AGC, Resampler/Halfband filters, timing NCO, discrimina-
tor, and output sections operate on the rising edge of
PROCCLK. The third clock, REFCLK, is used to generate tim-
ing error information.
NOTE: All of the clocks may be asynchronous.
PDC Applications Overview
This section highlights the motivation behind the key program-
mable features from a communications system level perspec-
tive. These motivations will be defined in terms of ability to
provide DSP processing capability for specific modulation for-
mats and communication applications. The versatility of the
Programmable Downconverter can be intimidating because of
the many Control Words required for chip configuration. This
section provides system level insight to help allay reservations
about this versatile DSP product. It should help the designer
capitalize on the greatest feature of the PDC - VERSATILITY
THROUGH PROGRAMMABILITY. It is this feature, when fully
understood, that brings the greatest return on design invest-
ment by offering a single receiver design that can process the
many waveforms required in the communications marketplace.
FDM Based Standards and Applications
Table 1 provides an overview of some common frequency
division multiplex (FDM) base station applications to which the
PDC can be applied. The PDC provides excellent selectivity
for frequency division multiple access (FDMA) signals. This
high selectivity is achieved with 0.012Hz resolution frequency
control of the NCO and the sharp filter responses capable
with a 255-tap, 22-bit coefficient FIR filter. The 16-bit resolu-
HSP50214
6
tion out of the Cartesian to Polar Coordinate converter are
routed to the frequency detector, which is followed by a 63-
tap, 22-bit coefficient FIR filter structure for facilitating FM and
FSK detection. The 14-bit input resolution is the smallest bit
resolution found throughout the conversion and filtering sec-
tions, providing excellent dynamic range in the DSP process-
ing. A unique input gain scaler adds an additional 42dB of
range to the input level variation, to compensate for changes
in the analog RF front end receive equipment. Synchroniza-
tion circuitry allows precise timing control of the base station
reconfiguration for all receive channels simultaneously. Por-
tions of this table were corroborated with reference [2].
TABLE 1. CELLULAR PHONE BASE STATION APPLICATIONS
TDM Based Standards and Applications
Table 2 provides an overview of some common time division
multiplying (TDM) base station applications to which the
PDC can be applied. For time division multiple access
(TDMA) applications, such as North American TDMA
(IS136), where 30kHz is the received band of interest the
PCS basestation, the PDC offers 0.012Hz frequency resolu-
tion in downconversion in addition to
grammable) filtering capability. The
can be processed using the PDC Cartesian to Polar coordi-
nate converter and d /dt detector circuitry or by processing
the I/Q samples in the DSP P. The PDC provides the ability
to change the received signal gain and frequency, synchro-
nous with burst timing. The synchronous gain adjustment
allows the user to measure the power of the signal at the A/D
at the end of a burst, and synchronously reload that same
gain value at the arrival of the next user burst.
For applications other than cellular phones (where the pre-
ambles are not changed), the PDC frequency discriminator
output can be used to obtain correlation on the preamble
pattern to aid in burst acquisition.
STANDARD
CHANNELS
DEVIATION
DEVIATION
# TRAFFIC
CONTROL
CONTROL
CHANNEL
CHANNEL
MODULA-
MODULA-
RX BAND
BW (kHz)
(Kbps)
VOICE
PEAK
PEAK
(MHz)
RATE
TION
(kHz)
(kHz)
TION
USING FDMA
824-849
(IS-91)
AMPS
FSK
832
FM
30
12
10
8
MCS-L1
MCS-L2
925-940
1200
25.0
12.5
FSK
600
FM
4.5
0.3
5
NMT-400
NMT-900
453-458
890-915
1999
12.5
FSK
200
FM
3.5
1.2
25
5
/4 DPSK modulation
= 0.35 matched (pro-
451-456
C450
20.0
10.0
FSK
222
444
FM
2.5
5.3
4
871-904
915-925
ETACS
NTACS
1240
25.0
12.5
FSK
800
FM
9.5
6.4
8