evolution of dvb-t front-end receivers through integration

7/31/2019 Evolution of DVB-T Front-End Receivers Through Integration

1/4 Copyright DiBcom - MK0706WP2 1

Abstract:

In August 2006, DiBcom announced the availability ofthree new integrated circuits, intended to reduce cost and

simplify DVB-T and DVB-H digital reception on all mobileand portable devices. The DIB7070 family regroupscomponents that implement either DVB-T only, DVB-Honly, or both standards. All these components utilize theSystem-in-Package (SiP) technology to integrate twodies (Tuner + Demodulator) in one chip. This approachoffers real advantages to digital television applications(Fixed and Mobile) in terms of performance, size andcost reduction.

Evolution of DVB-T Front-end Receivers through integration

White Paper N2 - june 07

The DIB7070 components are targeted for markets suchas TV reception on PCs, in-car DVB-T boxes, and other

portable multimedia TV receivers.The high level of integration and low cost have proven tobe strong arguments in replacing the bulky DVB-T front-ends in set-top boxes and television sets. Even moreconvincing is the use of the DIB7070 in solutions wherethere is a need for a dual antenna/tuner device. Thegoal being to support antenna diversity when receptionconditions are not optimal or to offer a PVR/Time-shiftingfunctionality.

2005Two chip front-endRF tuner + demod

2006One chip front-end

2007One chip front-endsmaller package

< 2004Traditional in-can tunerfront-end

DIB7070 12x12mm

DIB9080 7x7mm

Three chip receiverDIB3000 (2005)

Two chip receiverDIB7070 (2006)

One chip receiverDIB7770 (2007)

Evolution ofintegration

by

DiBcom


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Figure 1

TraditionalSet Top Box

Traditional DVB-T Set-Top-Box DesignA DVB-T decoder for the reception of digital television is essentially composed of a front-end and a back-end (Figure 1).

Current DVB-T set-top boxes are equipped with a particularly large front-end (Figure 1 shows a classic DVB-T Set-TopBox.) However, introducing a tuner into the new mobile multimedia TV receivers, or potentially into LCD television setswith integrated DVB-T receivers, is an arduous task.

The front-end (shown in blue box) is composed of an RF tuner, commonly called in-can as it is housed in a metalliccasing, a Surface Acoustic Wave lter (SAW), an IF amplier, a crystal and a DVB-T demodulator in baseband. Thissolution is obviously not optimized from the point of view of overall dimensions. The implementation is generally bulky,4x5x1 cm, and too large for use in portable terminals.In addition, the in-can tuner consumes a high level of power (~700 mW) and requires a great deal of ne-tuning beforeleaving the factory. The RF lters need to be centered on the wanted channel, and therefore must be able to track thedesired frequency when the user selects a given channel. This characteristic makes it difcult to integrate, and it isusually implemented with discrete components such as coils and variable capacitors (varicaps) as in Figures 2 & 2a.

This results in a dispersion of the receivers characteristics (sensitivity, ltering, etc).Advancements in silicon technologies now allow us to integrate all types of electronic structures including capacitorsand inductors (Figure 3).

Figure 2a

Manual Tuning

Figure 2

55 mm

Tuner (RF)

Demodulator

FI or Baseband

Front-end

Back-end

Back-endProcessor

(MPEG2 decoder, ...)

User Interface(Display, remote control,audio/video switching...)

The front-end includes an antenna, anRF tuner, and a demodulator. The tunerensures ltering and conversion of theselected RF channel, in an intermediatefrequency (IF) or in baseband, whilethe demodulator ensures the channeldecoding and reproduces the data beingtransmitted.

The back-end of the receiver processesthe source decoding and decompressesthe data (source-coded in Mpeg-2 orMpeg-4).

Figure 3Integrated inductors

170m


3/4

A Fully Integrated Front-End

The integration of a silicon RF tuner and a DVB-T demodulator in the same component resolves the problems of space,characteristics dispersion and cost of front-ends. This is the path chosen by DiBcom with the DIB7070 family (Figure 4a).

Among the members of this family, the DIB7070-P is dedicated to terrestrial digital TV reception on PCs or portablemultimedia devices. It allows for the implementation of highly integrated solutions, in simple mode or with a doubleantenna (diversity mode), in order to ensure the best possible DVB-T indoor reception.The DIB7070-P integrates the two functions of tuner and DVB-T demodulator, thus reducing the front-end to its simplestform (Figure 4b). The tuner/demodulator coupling has a big impact on AGC optimization and prevents the duplicationof modules in both circuits. Moreover, the integration is especially efcient when a Zero IF (I & Q) tuner output isused because the costly external RF SAW lter is replaced by a simple digital lter in the demodulator. A simple crystaloscillator is therefore the only external component required.

Moreover, the fact that supplies are reduced to a single component also leans in favor of the DIB7070-P. Consumptionlevels of approximately 400mW can be measured on these circuits in DVB-T mode, on both UHF and VHF(III) bands.

with NF : Noise Figure of the receiver in dBC/N : Carrier to Noise Ratio in dB

B : Bandwith of the receiver in MHz

3

Receiver Sensitivity:

The reception sensitivity, selection of adjacent channels, and saturation due to high-level signals, are the stringentelements of the performance required by xed and mobile DVB-T receivers as dened by the NorDig and MBRAIspecications. The sensitivity is dened as the minimum received eld strength C

minneeded at the input of the front-end

insuring a Quasi Error Free (QEF) performance (ie a Bit Error rate of 2x10-4) after the Viterbi decoder. The calculatedsensitivity is given by the following formula:

The Noise Figure (NF) is mainly related to the performance of the tuner. For the DIB7070 or DIB9080 families the NoiseFigure is around 3 dB.The Carrier to Noise Ratio (C/N) value comes from the demodulator. The Proven Performance DiBcom chips exceed thelower Typical Reference Receiver C/N performance by a full 3dB which can achieve a given quality level in a coveragearea at least 50% greater than the reference !

Table 1 shows the measured sensitivity (without the need for an external LNA):

Figure 4a: DIB7070 Block Diagram Figure 4b: DIB7070 chipset

DIB7070P

Quartz

Sensitivity Measured Average sensitivity (dBm) DiBcoms Average margin (dB)

vs MBRAI spec8K QPSK CR=1/2 -97.4 3.8

8K 16QAM CR=1/2 -91.5 3.6

8k 64QAM CR=1/2 -83.9 3.7

Table 1

Highintegration


4/4Contact: [email protected] - www.dibcom.com

Receiver Linearity and Selectivity

The linearity characteristic is very important. It helps achieve a good sensitivity even in the presence of analog and digital

adjacent channels. As adjacent channels, we do not only consider n+1 and n-1 channels, but also n+k and n-k where k cango all the way to 9.The receiver linearity is often represented by the third order intercept point (IP3) which is a gure of merit that characterizesa receivers tolerance to several signals that are present simultaneously outside the desired passband. As seen on the curvesin Figure 5, for a two tone channel (F1 & F2), the intermodulation products grow with the input amplitude raised to a power ofthree as compared to only a power of one for the output level of the required signal. In addition, Table 2 gives the IP3 valuesmeasured at the input of the DIB7070 chipset family in UHF, VHF and even in L-Band for a low AGC gain (most interesting casefor saturation problems):

Test Pattern name(8K 16QAM GI=1/32 CR=1/2

Adjacent Channels(In addition to tuned channel N)

Measured AverageSensitivity (dBm)

DiBcoms Average Margin (dB) vsMBRAI spec

Linearity Patterns

L1 Digital N+2 / Analog N+4 -87.2 7.2

L2 Analog N+2 & N+4 -86.5 6.5

L3 Digital N+2 & N+4 -81.8 6.8

Selectivity Patterns

S1 (N+1) Analog N+1 -87.1 14.1

S1 (N+2) Analog N+2 -84.2 8.2

S2 (N+1) Digital N+1 -82.2 18.2

S2 (N+2) Digital N+2 -80.6 12.6

Frequency Bandwith Measured Input IP3 (for low AGC gain) on DIB7070 chipsets

UHF -5 dBm

VHF -2 dBm

L-Band -0 dBm

Table 2

Table 3

But experience proves that IP3 is not a sufcient gure of merit for the performance of digital receivers in presence of adjacentchannels. The selectivity of the channel lters is also of great importance. Therefore, the best way to evaluate the linearity /selectivity effects for a given required channel is to measure the maximal level of adjacent channels leading to a Quasi ErrorFree (QEF) quality of reception. As an example, the curves in Figure 6 show the margin offered by the DIB7070 family when itcomes to adjacent channel robustness as dened in the NorDig specication for n+1 and n+2:

Saturation

Pin(dBm)

Pout(dBm)

IP3

Intermodulation products(2F2-F1, 2F1-F2)

slop

e1

slo

pe

3

Figure 5

Another set of measurements is dened in the MBRAI / IEC62002 specication (Mobile and Portable DVB-T/H Radio AccessInterface Specication). The DiBcom margins over MBRAI Selectivity pattern (S1, S2) and Linearity patterns (L1, L2, L3)including different combination of digital and analog adjacent channels from N1 to N4 are shown in Table 3.

Figure 6 : Adjacent Channel Robustness at 666MHz

37dB

N N+1

44dB

N N+2

20dB margin

8dB margin

27dB margin

7dB margin

7070P

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QGR93

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D29NQ

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DiBcom contributes to the growing success of Digital Television by offering cost effective highly inte-grated solutions. In addition, robustness, high performance, small size and ease of integration are keyassets brought by DiBcom to move Digital TV to a mass market.

Single or Diversity DVB-T receivers can now be implemented in all types of receivers such as LCD TV,Portable Media Players (PMP), Portable Navigation Devices (PND), Laptop PCs, Automotive STBs, etc

evolution of dvb-t front-end receivers through integration

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