FI114763B - filter Events - Google Patents

Description

FIELD OF THE INVENTION The invention relates to filtering a signal received by a terminal. More particularly, the invention relates to filtering a received signal in a terminal receiver capable of operating in a plurality of frequency ranges.

Background of the Invention

Today, the terminals are implemented in such a way that they can operate in several frequency bands. For example, more bandwidths will provide more capacity to the networks, thus improving and accelerating the availability of different services and especially their availability. Frequency bands typical of cellular networks are, for example, 800 MHz, 900 MHz, 1800 MHz and 1900 MHz.

20. special features are required for receivers of multi-band terminals. Because the terminals- ·. tea antenna receives a very wide frequency band * · · ». ·. : To fold the signal, it is especially important that • · signals from unwanted • • * 25 hair are filtered out of the received signals. The filtering of the signals received by the mobile stations typically utilizes various bandpass filter arrangements that pass through a specific frequency band, i.e. the passband. . signals.

• * · 30 *** The width of the pass bandwidths of the filters used in the filter arrangement and their location in the frequency domain affect the implementation and operation of the filter arrangement.

Thus, it is possible to use different components in the implementation of each arrangement, whereby the costs of implementing the arrangements are different.

2 114763

Filters are generally required to have a good frequency stability at different temperatures. This means that the pass band of the filter must remain the same, i.e. the pass band 5 does not move despite potentially large temperature fluctuations. For example, the typical so-called. The passband of SAW filters (SAW = Surface Acoustic Waves) changes with temperature so that they may not be suitable for all purposes as such. However, SAW filters can be used as long as their properties are considered at the design stage. The advantage of SAW filters is their relatively low cost.

15 Summary of the Invention

The object of the invention is to eliminate or at least reduce the disadvantages of the prior art in filtering the signal received by the terminal. The invention provides a filtering procedure, a terminal, and a bandpass filter arrangement for filtering a signal received at a terminal.

* * · ·

The object of the invention is to improve the filter arrangement used in the receivers of portable terminals 25, so that the final passband of the output of the filter arrangement is as steep as possible.

* ·

It is a further object of the invention that the arrangement is inexpensive and technically feasible for use in a portable terminal.

. ···. The above objects are achieved by the solutions described in the independent claims.

35 3 114763

According to a first basic idea of the invention, there is provided a filtering method for a frequency band received by a multicast receiver of a wireless communication terminal, the method comprising: 5 received frequency bands being filtered to form at least two pass bands, the pass bands being further outputted; and wherein - the lowest frequencies 10 of the lowest received pass band are filtered off to narrow said pass band and other band frequencies are passed through; and / or - the upper frequencies of the highest received pass band are filtered off to narrow said pass band and other band frequencies are passed through.

Preferably, up to two different pass lanes are narrowed.

Preferably, the passband is narrowed to no more than half of the bandwidth of the unbanded passband.

Preferably, the pass bands are amplified before being exported to the band pass filter.

• · 25 Preferably, the lanes are narrowed, at least some of which overlap to some extent.

* »I · ... * Preferably, the multiband receiver receives a signal from the DCS and PCS systems.

30

According to a second basic idea of the invention, there is provided a multicast receiver for a wireless communication terminal, the receiver comprising:, ·, at least two bandpass filters, the passband of the first h / 35 band pass filter extending to the lower pass bandpass; to narrow the passband of either the first or second pass filter, or both pass passes, a third pass pass filter having one or both of the following conditions applied at one pass: - the pass pass pass of the first pass pass,

Preferably, the first and second bandpass filters 15 are connected in parallel.

Preferably, the third bandpass filter is arranged to narrow the passband by up to half the bandwidth of the passband.

20

Preferably, each bandpass filter is adapted to attenuate the frequencies outside the filter's own passband.

(· 25 Preferably, the terminal further comprises an amplifier between the first and the third bandpass filters for amplifying the signals in the passband of the first bandpass filter.

Preferably, the terminal further comprises, between the second and third bandpass filters, the signal in the passband of the second bandpass filter of the amplifier. to strengthen the lice.

Preferably, the pass bands of the first and second band pass filters have DCS and PCS system signals! 5 114763 so that each passband has different system signals at the same time.

Preferably, the third bandpass filter is implemented as a 5 ceramic filter.

Preferably, the first and second bandpass filters are SAW filters.

Preferably, the terminal is a mobile station such as a cellular telephone.

According to a third basic idea of the invention, there is provided a bandpass filter arrangement, the arrangement comprising: at least two bandpass filters, the passband of the first band pass filter extending at a lower frequency than the pass band of the second band pass filter; 20, to narrow the pass band of either the first or second band pass filters, or both, to a third band pass filter having either or both of the following valid at the pass band '**. of the conditions: 25 - the lowest pass frequency of the third pass pass filter, .. · is the pass pass of the first pass pass pass filter: *, - the highest pass pass of the third pass pass pass filter is within the pass pass of the second pass pass filter.

It is an object of the invention to provide a filter arrangement which fulfills the above requirements. Requirements to arrive ···. is provided by a filter arrangement in which the non-overlapping pass bands 35 of the first two band pass filters are applied to a third band pass filter which favors 114763 data from the lower frequency band to the lower frequencies and the upper frequency band to the upper frequencies.

The arrangement according to the invention has several advantages. The first two of the so-called 5 front filters can be low cost SAW filters that are simple to implement. Since the third filter filters the pass bands of both front filters, i.e. the third filter determines the final bands, the determination of the filtering parameters of the front filters does not need to take very careful account of the possible movement of the front filter pass bands, e.g.

List of patterns 15

In the following, the invention and its preferred embodiments will be described in more detail with reference to Figures 1-4, in which Figure 1 is a front view of the terminal, Figure 2 is a schematic block diagram of the terminal, Figure 3 represent the various '··' 25 pass bands of the filter arrangement, and.

'I I

Detailed Description of the Invention

Figure 1 illustrates an embodiment of 30 terminal 90s according to the invention, comprising keys 91 and a display 92. The terminal shown operates as a transceiver which, for example, operates using GSM, GPRS, UMTS or something else. a method known per se, or. something standard. The terminal may employ 35 Time Division Multiple Access (TDMA), FDMA (FDMA =

Frequency Division Multiple Access), CDMA (CDMA = Code

• I

7 114763

Division Multiple Access) or any other channeling method. However, the channeling method used does not affect the operation of the invention. The terminal is preferably so-called. multiband terminal.

The terminal may be a mobile telephone or some other terminal, but the type of the device itself or the like is not essential to the invention. It is essential for the invention that the device is capable of receiving a signal through the air path.

In addition to receiving a signal, the subscriber terminal 90 shown in Figure 1 is capable of transmitting a signal to the air path.

Figure 2 is a block diagram of an embodiment of a subscriber terminal device according to the invention.

The transceiver terminal comprises, on the receiver side, a front filter block 20, an amplifier 30, a filter 40 and a demodulator 50. The terminal comprises a transceiver modulator 70 and an amplifier 80. The filters 20, 40 are part of the receiver filter arrangement 20.

The terminal 90 comprises an antenna 10 of known type for transmitting and receiving a signal. The antenna can be either internal, · 25 or external. The terminal further comprises keys, .91, display 92, headset 93, and microphone 94.

? *

Further, the terminal comprises a terminal for controlling the blocks of the control means 60. The control means 60 receives signals from the microphone 94 and the keyboard 91 which are further transmitted to the headset 93 and the display screen 92.

The control means 60 can be implemented, for example, by means of a micro-pro, ···, a processor and a software.

35 In the receiving or rx direction, the terminal operates in the principle of · ··· as follows. Antenna 10 receives well 8114763 broadband signals which are applied to filter block 20 for filtering. The filter block 20 is in practice a bandpass filter which can be implemented, for example, with a SAW filter, whereby the cost of obtaining the filter 5 is relatively low. The output of the filter block 20 is coupled to the input of the amplifier 30 to amplify the signals in the filter pass band.

The amplified signals are applied to a filter 40 which is also a bandpass filter. The signals in the filter pass band are applied to demodulator 50 for demodulation, after which the demodulated signal is applied to control means 60 which further processes the signal.

15 In the transmission or tx direction, the terminal operates in principle as follows. The control means 60 processes the information signal from the microphone 94 which is applied to the modulator 70 for modulation. The signal obtained as a result of modulation 20 is amplified in amplifier 80, after which the amplified signal is transmitted via antenna 10 to the radio path.

. The terminal may, for example, operate on GSM (GSM = Global

25 Systems for Mobile Telecommunications, 900 MHz), DCS- (DCS

.. · = Digital Cellular System, 1800 MHz) and PCS. ”· (PCS = Personal Communications Services, 1900 MHz). That is, the frequency band of the DCS system is uplink 1710-1785 and downlink 1805-180 MHz. The frequency band of the PCS system is in the uplink direction 1850 - 1910 and in the downlink direction 1930 - 1990 MHz.

···, Assume that the terminal operates in three frequency bands * 'fbi (900 MHz), fb2 (1800 MHz) and fb3 (1900 MHz), of which frequency band fbl is relatively far from fb2 and fb3.

Instead, said frequency bands fb2 and fb3 are relatively close to each other and may overlap to some extent. Even if the frequency bands fb2 and fb3 do not overlap, the frequency bands must preferably be separated by bandpass filtering 5.

Figure 3 shows a filter arrangement in the receiver comprising a filter block 20 and a filter 40. Figure 3 shows that the filter block 20 comprises at least 10 first band pass filters 21 and a second band pass filter 22. The arrangement further comprises an amplifier block 30 consisting of amplifiers 31, 32. The output of the filter 21 is connected to the input of the amplifier 31 and the output of the filter 22 is connected to the input of the amplifier 32. The outputs of the amplifiers are connected and coupled to the input of a third filter 40.

The filters 21, 22 apply bandpass filtering to the frequency band they receive. The signals in the pass band of each of the filters 21, 20 22 are amplified, and the amplified signals are applied to a third filter 40, which further filters the signals in the pass bands of the filters 21, 22 'if necessary.

Referring to Fig. 4, which illustrates the pass bands 21a, 22a, 40a of the filters, '*, 21, 22, and 40. Filter 21

transmitting signals received by the terminal antenna which are in the first frequency band. Swamp-·.; The lower limit of the pass band of 30 dates 21 is the frequency f2iL

and the upper frequency f2iH. The filter 22 passes signals received by the terminal antenna which are in the second frequency band. The low-pass filter 22 is formed by the frequency f22L and the upper limit is 35 f 22h 114763

As shown in Figure 4, the lowest pass frequency f22H of the second band pass filter 22 is higher than the highest pass f2iH of the first pass pass filter 21. In other words, the pass lanes 5 of the first and second filters do not overlap.

The signals in the passband of the first filter 21 are applied for amplification to the amplifier 31 and the signals in the passband of the second filter 22 are provided for amplification in amplifier 32. After amplification, the signals are applied for filtering to a third bandpass filter 40 In other words, with reference to Figure 4, the following formula is valid:

(1) f 21L <f 40L <f 21H

The highest pass frequency 20 of the passband of the third band pass filter 40 is in the pass pass of the second pass pass filter 22. More specifically, this means a condition of the following order for a filter arrangement.

«» »» · '·' · (2) f 22L <f 40H <f 22H · t: .; 25

The third bandpass filter 40 is preferably of the * * ceramic type so that it is easy to implement.

· ',,, · Tuning is easy because the passband of the filter does not change due to temperature change. The ceramic 30 filter also gives sharp edges to my emission band.

* * ·

The lower bandwidth coming to the third bandpass filter 40 includes signals from both the DCS and the PCS system. The filter parameters of the third bandpass filter 40 are selected such that the filter passband 11 1 1 4763 is obtained as desired. The filter 40 narrows the pass bands of the first and second filters to obtain the desired width of each band. However, the third filter 40 does not necessarily need to narrow each passband 21a, 22a by as much.

The arrangement according to the invention makes it possible to minimize the filter costs, since the final pass band is determined by the pass band of only one filter, i.e. the third filter 40. In other words, the filter arrangement requires only one high performance filter (filter 40), which can be precisely adjusted to the desired emission frequency without changing, for example, the effect of temperature. Since the edges of the passband of the ceramic filter 40 are steep, the filters 21, 22 can be implemented with low cost SAW filters which do not necessarily have to have the same technical specifications as the filter 40.

20

Figures 5 and 6 show some possible pass bands for the filter arrangement. Figure 5 shows that the bandwidth. the lowest emission frequency f40L of the emission filter 40 emission band

. is in the passband 25 of the first bandpass filter 21 just as in Figure 4.

; t Conversely, the highest pass frequency of the passband of the third pass pass filter 40 is the same as the pass pass of the pass pass passage 22 of the second pass pass filter. The third pass pass filter 40 may still have higher pass passes than the pass pass pass. 22 is the highest frequency of the passband. * In connection with FIG. 5, the filter scheme has the formula • »I * *; 35 (3) f22L <f40H = f22H · * III» i2 1 1 4763

Figure 6 shows that the band pass block 20 has formed three pass bands 21a, 22a, 23a, of which the bands 21a and 23a overlap to some extent. Further, a passband 40a is shown for the bandpass filter 40.

5 For the cut-off frequencies of the pass bands, the formula (4) f21L <f40L <f23L <ί · 21Ά <f23H <f22L <f4OH <f22H · 10 applies now. The figure further shows that the filter 40 filters out frequencies lower than the frequency f40L out of the lower band, i.e. 15 bands 21a. The filter 40 also filters frequencies higher than the frequency f40H / off the top band, i.e. band 22a. The passband of the filter 40 is set such that it passes at least half of each pass, for example pass pass 22a.

20

As stated previously, the filter block 20 may comprise more than two band pass filters, each at least one emission band. Here too the status-. In the tea, the bandpass filter 40 filters and attenuates 25 at most two at a time, formed by the filter K * .determinants in the filter block 20. Specifically, the bandpass filter 40 filters the lowest pass * or mole of the filter block 20. If there are three or more pass bands formed by the filter block 30 20, »· '; '* Middle lanes as such through band pass filter · * · * 40.

Although the invention has been described above with reference to the enclosed silicon; 35, it will be understood that the invention is not limited thereto, but that one skilled in the art may modify the disclosed solutions without departing from the spirit of the invention.

Claims (17)

114763 A filtering method for 5 frequency bands received by a wireless communication multi-band receiver, characterized in that the filtering method comprises: filtering the received frequency band to form at least two pass bands, and narrowing said passband and the other frequencies of the passband being passed through; and / or 15. the upper frequencies of the highest received passband are filtered off to narrow said passband and other frequencies of the pass pass through. 2. A method according to claim 1, c h a r a c t e r i z e d in that no more than two different emission bands are narrowed. ,; Method according to claim 1 or 2, characterized in that the passband 25 is narrowed to no more than half the bandwidth of the unbanded passband. * » Method according to any one of the preceding claims, characterized in that 30 the pass lanes before being exported for band pass filtering. 5 About PCS systems. Method according to any one of the preceding claims, characterized in that the pass bands, at least a part of which overlap to some extent, are narrowed. 114763 Method according to any one of the preceding claims, characterized in that the multi-band receiver receives a signal DCS and A wireless communication multi-band receiver comprising at least two band-pass filters (21, 22), the first band-pass filter (21) of which passes a lower frequency than the second band-pass filter (22), characterized in that the receiver further comprising: a first or second bandpass filter for narrowing the passband 15 or both passbands, a third bandpass filter (40) having one or both of the following conditions applied at one time: the lowest passband frequency of the first bandpass filter ) in the pass band, - the highest pass of the third band pass filter (40). the frequency is in the passband of the second bandpass filter (22). I t 25 »» 8. A terminal as claimed in claim 7, characterized in that the first and second band-pass filters are connected in parallel. \ '30 The terminal of claim 7 or 8, * ·; ' characterized in that the third bandpass filter v: (40) is arranged to narrow the passband to a maximum of: half the passband bandwidth. Terminal device according to one of claims 7 to 9, characterized in that each bandpass filter 114763 is arranged to attenuate the frequencies outside the filter's own passband. Terminal device according to one of Claims 7 to 10, characterized in that the terminal device further comprises, between the first and third band pass filters, an amplifier (31) for amplifying the signals in the pass band in the first band pass filter (21). 10 The terminal device according to any one of claims 7 to 11, characterized in that the terminal device further comprises, between the second and third bandpass filters, an amplifier (32) for amplifying the signals in the bandwidth of the second bandpass filter 15 (22). Terminal device according to one of Claims 7 to 12, characterized in that the pass bands of the first and second band pass filters have signals of the DCS and PCS systems so that each pass band has simultaneously different system signals. Terminal device according to one of Claims 7 to 13, characterized in that the third bandpass filter (40) is implemented as a ceramic filter. Terminal device according to one of Claims 7 to 14, characterized in that the first and second, band pass filters are SAW filters. '30 Terminal device according to one of claims 7 to 15, characterized in that the terminal device is a mobile communication device such as a mobile phone. , 35 A bandpass filter arrangement comprising at least two bandpass filters (21, 22), the first band of which has a lower bandwidth than the second bandpass filter (22), characterized in that the arrangement further comprises: or a second bandpass filter for narrowing the pass band or both pass bandwidths of the third band pass filter (40) having one or both of the following conditions applied at the same time: the highest pass frequency of the third band pass filter (40) is in the access band of the second band pass filter (22). • · * I »• t • 1 t« 1 • 1 {· I • »> {·» I t 114763