CA2168681A1 - Rf repeaters for time division cordless telephone systems without timing signals - Google Patents
Rf repeaters for time division cordless telephone systems without timing signalsInfo
- Publication number
- CA2168681A1 CA2168681A1 CA002168681A CA2168681A CA2168681A1 CA 2168681 A1 CA2168681 A1 CA 2168681A1 CA 002168681 A CA002168681 A CA 002168681A CA 2168681 A CA2168681 A CA 2168681A CA 2168681 A1 CA2168681 A1 CA 2168681A1
- Authority
- CA
- Canada
- Prior art keywords
- signals
- amplifier
- basestation
- signal
- handset
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
Abstract
An RF repeater for exchanging digital telephone signals between a basestation and a mobile cordless handset, has an amplifier for amplifying basestation-to-handset signals and handset-to-basestation signals, a timing generator for providing a timing output and a switching arrangement operable in response to the timing output to sample the signals and to connect the sampled signals alternately to the amplifier for amplification thereby. The timing output of the timing generator having a frequency sufficient to effect Nyquist sampling of the signals by said switching arrangement and at least one filter connected to the amplifier for reconstructing the signals from the amplified samples thereof so that said signal timing information is not required.
Description
216&681 26PlSCA
The present invention relates to RF repeaters for use in cordless telephone systems and, more particularly, for interfacing with mobile cordless handsets and with b~eest~tions, 5 which are conn~te~ to public switched telephone networks, for exch~nging l~AI~n~il and receive signals. More particularly, the present invention is applicable to RF repeaters employing time division duplex (TDD) tr~nemiesions, to those employing frequencydivision duplex (FDD) trAnemieeions and, also, to those employing both TDD
tr~nemiesions and FDD trAnemiesions.
The present RF repeaters are useful, in particular, in telephone systems which employ RF
l~p~lel~ to re-broadcast signals that reach the RF repeaters via radio links. However, the invention is also useful for systems employing other signal links, e.g. ~le-lir~t~l co-axial and/or fiber optic cables, cable television plant and microwave links, to supply the signals 15 between the basestation and the RF repeaters.
It is expected that Personal Co..~ tion Services (PCS) microcells will be supporting a rapidly increasing number of h~n-leete in North ~m~ric~ and elsewhere in the near future.
A number of proposed h~n-leete use TDD formats, which employ a single frequency for both h~n~eet-to-bAeest~tion co.~ tion and for bAeest~tion-to-h~n~1eet co.~.. ~i~tion, with a h~n~set and bAeestAtion ~l~r~ A,~ rapidly in time, as to which has the use of the signal frequency. For example, DECT, Omnipoint and PHS systems use TDD formats.
25 Typically, the hAn~leet uses the signal frequency for 1 millieecond, and the b~ee,et~tion uses the signal frequency for the next millieecond.
In FDD formats, such as cellular telephone systems, DCS-1900 systems etc., industry mAmlf~tllres an RF repeater which uses a first ~ntt-nn~ to receive a tr~nemieeion from a 30 basestation and then rebroadcasts the tr~nemiesion as an amplified signal via a second Ant~nn~ Similarly, a signal elllAI~ g from the h~n~eet is received at the second Antenn~, and then amplified and rebroadcast to the b~çst~tion via the first ~ntPnn~ In some cases, a co-axial cable is employed instead of a radio link to exch~nge the signals between the b~est~tion and the RF repeater. These arrangements allow desi~nPrs of radio telephone networks to fill-in" coverage gaps (e.g. inside buildings, on the "shadowed" side of 5 valleys etc.) at low cost.
Thus, Figure 1 shows a prior art system using a radio link for connP~ting a b~est~tion 10 to a mobile cordless h~n-l~et 11 via an RF repeater in~ic~te~l generally by reference numeral 12. The RF repeater 12 has radio links via ~ PI~n~ Al and A2 with the 10 basestation 10 and the h~n~l~et 11, respectively. A co-axial cable or optical fiber cable may ~ltPrn~tively be employed to link the RF repeater 12 to the b~P,~ ion 10. For FDD
systems, components 14a and 14b of the RF repeater 12 are diplex filters. The diplex filters are illLercollnPcted by a ~ signal path Pl for ~l~sll~il signals passing from the basestation 10 to the h~n-l~et 11, and a receive signal path P2 for receive signals passing 15 from the h~n-lset 11 to the b~est~t on 10. The signal paths Pl and P2 include amplifiers l5a and 15b, respectively.
For TDD h~n-l~et~, RF repeaters are generally more complicated since, in t_is case, and because the same frequency is used for ~ slllil and receive signals, components 14a and 20 14b of Figure 1 cannot be diplex filters, but instead are switches that select either a basestation - RF repeater - h~n(lset signal path or a h~ndset - RF repeater - b~est~tion signal path, depending on the time epoch.
TDD RF repeaters need access to the timing of the llallslllil and receive signals to effect 25 the switching of components 14a and 14b correctly. Access to this timing is often ~iffirlllt, particularly when the b~est~tion - RF repeater signal tr~n~mi~sion is via a radio link, which precludes spec~ ed subcarriers for transporting timing i,~llllalion.
The timing of components 14a and 14b becomes even more difficult once time delays caused by tr~n~mi~ion from the b~est~tion to the RF l~eat~ become large compared to the RF repeater - h~ndset propagation delay, since this can result in the RF repeater needing to amplify and rebroadcast both transmit and receive signals in the same time S epoch.
To overcome these difficulties, TDD repeaters are typically arranged as shown in Figure
The present invention relates to RF repeaters for use in cordless telephone systems and, more particularly, for interfacing with mobile cordless handsets and with b~eest~tions, 5 which are conn~te~ to public switched telephone networks, for exch~nging l~AI~n~il and receive signals. More particularly, the present invention is applicable to RF repeaters employing time division duplex (TDD) tr~nemiesions, to those employing frequencydivision duplex (FDD) trAnemieeions and, also, to those employing both TDD
tr~nemiesions and FDD trAnemiesions.
The present RF repeaters are useful, in particular, in telephone systems which employ RF
l~p~lel~ to re-broadcast signals that reach the RF repeaters via radio links. However, the invention is also useful for systems employing other signal links, e.g. ~le-lir~t~l co-axial and/or fiber optic cables, cable television plant and microwave links, to supply the signals 15 between the basestation and the RF repeaters.
It is expected that Personal Co..~ tion Services (PCS) microcells will be supporting a rapidly increasing number of h~n-leete in North ~m~ric~ and elsewhere in the near future.
A number of proposed h~n-leete use TDD formats, which employ a single frequency for both h~n~eet-to-bAeest~tion co.~ tion and for bAeest~tion-to-h~n~1eet co.~.. ~i~tion, with a h~n~set and bAeestAtion ~l~r~ A,~ rapidly in time, as to which has the use of the signal frequency. For example, DECT, Omnipoint and PHS systems use TDD formats.
25 Typically, the hAn~leet uses the signal frequency for 1 millieecond, and the b~ee,et~tion uses the signal frequency for the next millieecond.
In FDD formats, such as cellular telephone systems, DCS-1900 systems etc., industry mAmlf~tllres an RF repeater which uses a first ~ntt-nn~ to receive a tr~nemieeion from a 30 basestation and then rebroadcasts the tr~nemiesion as an amplified signal via a second Ant~nn~ Similarly, a signal elllAI~ g from the h~n~eet is received at the second Antenn~, and then amplified and rebroadcast to the b~çst~tion via the first ~ntPnn~ In some cases, a co-axial cable is employed instead of a radio link to exch~nge the signals between the b~est~tion and the RF repeater. These arrangements allow desi~nPrs of radio telephone networks to fill-in" coverage gaps (e.g. inside buildings, on the "shadowed" side of 5 valleys etc.) at low cost.
Thus, Figure 1 shows a prior art system using a radio link for connP~ting a b~est~tion 10 to a mobile cordless h~n-l~et 11 via an RF repeater in~ic~te~l generally by reference numeral 12. The RF repeater 12 has radio links via ~ PI~n~ Al and A2 with the 10 basestation 10 and the h~n~l~et 11, respectively. A co-axial cable or optical fiber cable may ~ltPrn~tively be employed to link the RF repeater 12 to the b~P,~ ion 10. For FDD
systems, components 14a and 14b of the RF repeater 12 are diplex filters. The diplex filters are illLercollnPcted by a ~ signal path Pl for ~l~sll~il signals passing from the basestation 10 to the h~n-l~et 11, and a receive signal path P2 for receive signals passing 15 from the h~n-lset 11 to the b~est~t on 10. The signal paths Pl and P2 include amplifiers l5a and 15b, respectively.
For TDD h~n-l~et~, RF repeaters are generally more complicated since, in t_is case, and because the same frequency is used for ~ slllil and receive signals, components 14a and 20 14b of Figure 1 cannot be diplex filters, but instead are switches that select either a basestation - RF repeater - h~n(lset signal path or a h~ndset - RF repeater - b~est~tion signal path, depending on the time epoch.
TDD RF repeaters need access to the timing of the llallslllil and receive signals to effect 25 the switching of components 14a and 14b correctly. Access to this timing is often ~iffirlllt, particularly when the b~est~tion - RF repeater signal tr~n~mi~sion is via a radio link, which precludes spec~ ed subcarriers for transporting timing i,~llllalion.
The timing of components 14a and 14b becomes even more difficult once time delays caused by tr~n~mi~ion from the b~est~tion to the RF l~eat~ become large compared to the RF repeater - h~ndset propagation delay, since this can result in the RF repeater needing to amplify and rebroadcast both transmit and receive signals in the same time S epoch.
To overcome these difficulties, TDD repeaters are typically arranged as shown in Figure
2.
10 In Figure 2, an RF repeater indicated generally by reference numeral 16 employs four physically distinct ~"I~n~ A3, A4, AS and A6 for b~sest~tion-to-h~n-1set and h~nll~et-to-basestation co~ ic~tions~ with amplifier 18 connected in a transmit signal path P3 between the ~ntPnn~ A3 and A6 and with amplifier 20 conn~ctçd in a receive signal path P4 between the ~ntPnn~ B and C, as shown. If the pl~cçnlçnt of the ~ u~ A3-A6 is15 effected correctly, the RF repeater 16 opel~es without need of timing signals and can even support large time delays. However, the RF lepea~er 16 is capable of osc-ill~ting because signals em~n~ting from the ~nt~n~ A3 can be received at the ~ nl~ A4, amplified by the amplifier 20 broadcast by the ~nt~nn~ AS and received at the ~l~t~nl~ A6, and then amplified by the amplifier 18 to be rebroadcast from the ~ A3.
To avoid this oscillation, the ~ntPnn~ A3-A6 need to be carefully sited so as not to interact, while still keeping the handset and the basestation in the field of view. In practice, this is difficult.
25 It is accordingly an object of the present invention to provide a novel and improved RF
repeater for use in cordless telephone systems which avoids a need for a plurality of ~nt~nn~, but which does not need transmit and receive signal timing info,lllation 2 1 6~68 1 According to the present invention, there is provided an RF repeater which has a timing output and a ~wi~cl.illg arrangement the operation of which is controlled by a timing output from the timing generator. The ~wi~chhlg arrangement samples a b~çst~tion-to-h~n-1~et signal and a handset-to-basestation signal and ~lt~rn~tely connects samples of the two 5 signals to at least one amplifier for amplification thereby. The frequency of the timing output of the timing generator is selçctçd so that the ~wilcl~ing all~lgel"ent effects Nyquist sampling of the signals and one or more filters are employed to reconstruct the signals from the amplified samples thereof.
10 The RF repeater according to the present invention thcl~rol~ has the advantage that no timing information is required to be tr~n.~mitted to the RF r~eatel, although generic information as to bandwidth and center frequency of operation must be known. Also, the present RF repeater can be implemented with only two ~ n~c and so can be easier to site than that shown in Figure 2.
The present RF l~peater can support bursts of the two signals which overlap in time which typically occurs due to large time delays in the propagation or signal links.
In addition, since the present RF repeater operates without reference to the b~ceshtion or 20 handset timing, it can support more than one TDD h~n~l~et type ~imlllt~nPously, even if the two types have dirÇelellt timings. Also, the present RF repeater can support FDD
handsets, even while simlllt~n~-ously supporting TDD handsets.
Further fealuies and advantages of the present invention will be more readily a~par~
25 from the following description thereof when taken in connection with the acco,~a~yhlg drawings, in which:
Figures 1 and 2 show diagrams of two prior art RF repeaters with an associated ~est~tion and handset;
2 1 6868 ~
Figure 3 shows a block diagram of an RF repeater according to a first embodiment of the present invention, in association with the b~est~tion and the handset;
Figures 4a to 4d show waveforms which occur in the RF repeater of Figure 3;
Figures S and 6 show block diagrams ill~ lhlg another RF repeater according to a second embodiment of the present invention; and Figure 7 shows a block diagram of a further RF repeater, according to a third embodiment 10 ofthe present invention.
Figure 3 shows an RF repeater, in~li~tçd generally by reference numeral 24, which differs from the RF repeater 12 of Figure 1 by the ad~litic)n of two RF b~n~lr~s filters 26 and 28, and a high speed oscillator 30 to provide a timing output which provides the RF r~ealel 15 24 with a very fast ~wilCl~illg action. In the embodiment of Figure 3, the components 14a and 14b are replaced by switches 14c and 14d.
The switches 14c and 14d form a switching arrangement which a) samples the two signals passing through the RF repeater 14, i.e. the b~est~tion-to-h~n-lset signal and the h~n-l~et-20 to-b~cest~tion signal and b) connects the samples of the two signals ~ltçrn~tçly to respective ones of the amplifiers. Thus, successive samples of the b~est~tion-to-h~n-l~et signal are amplified by the amplifier 18a and, ~ltçrn~ting with these samples, successive samples of the handset-to-b~est~tion signals are amplified by the amplifier 20a.
25 By chopping ~e switches 14c and 14d quickly between the two signal directions (base-to-handset and h~n~l~et-to-base), and by using replacing filters 26 and 28 by reconstruction filters 26a and 28a, the lack of a timing signal synchronized to the time epoch is nn~cess~ry since the reconstruction filters 26a and 28a ensure that any errors due to the high speed ~wilcl~illg are ~inl~o~ , provided the usual Nyquist sampling criteria apply, i.e. the switching rate of the switches 14c and 14d ~lele~ cl by the frequency of the timing outputs of the oscillator 30, measured in Hertz, should be at least twice the bandwidth of the RF signals that the amplifier is to rebroadcast, and the reconstruction filters 26a and 28b are bAn-lrA~s filters with a bandwidth of less than half the ~wilching 5 rate, but more than the RF signal bandwidth.
To take a concrete example, CT-2 signals typically occupy rh~nnel~ from 864 to 868 MHz. The net RF signal bandwidth, if all channels are to be rebroadcast, is 4 MHz. If an asynchronous, fast oscillator were employed to switch at a 21 MHz switch rate, a 10 typical filter bandwidth for the filters 26a and 26b would be 6 MHz, with a filter center frequency of 866 MHz.
Figure 4a dia~ ldmlllatically illustrates the b~est~tion-to-h~n-l~et signal passing through points X, X1, X2T and X3T of Figure 3. It will be seen that at points X and X1, i.e.
15 before and after the filter 26a, the basestation-to-h~n~lset signal received by All~ A7 from basestation 10a is lmrhAnged. At point X2T, this signal has been sampled by the switch 14c, and at point X3T, and at point Y, the signal samples appear in their amplified state, as amplified by amplifier 18a. The signal samples then pass through the b2n-1r~ss filter 28b, which from these samples reconstructs the basestation-to-handset signal, in its 20 amplified form, so that it appears at point Yl as illustrated in Figure 4b.
The h~n~et-to-ba~est~tion signal, received at ~-lelll-A A8 from h~n-l~et lla, appears at points Y1 and Y, i.e. before and after passing through the bandpass filter 28b, as shown in Figure 4c. This signal is then sampled by the switch 14d, so that the samples thereof 25 appear at point YR2 in the form shown in Figure 4c. These signal samples are then amplified by amplifier 20a and appear at points YR3 and X as shown in Figure 4c. The amplified samples then pass to the b~n-lrA~s filter 26a, which reconstruct the h~ncl~et-to-handset signal from these samples into the form diag~",ll,~ti~lly illustrated in Figure 4d.
2l6868l Figures 4b and 4d illustrate the interleaved native of the b~est~tion-to-h~ntl~et and h~n~l~et-to-b~est~tion c~ "~ ications. However, the amplifier 24 of Figure 3 does not require the colmllul~ications timing. Also, if the basestation-to-h~n~lset and h~n-l~et-to-basestation con~lllul~ications overlap in time, as happens when large time delays are 5 encountered, the amplifier 24 will still operate s~ti~f~ctorily.
Figures S shows an RF repeater, in~ ted generally by leferellce numeral 40, which is similar to that disclosed in the inventor's United States Patent No. 5,377,255, issued December 27, 1994, the disclosure of which is incol~?oldled herein by reference. The RF
10 repeater 40 has a coaxial cable input and output 42 conn~ct~l to a component 44 which is in turn conn~cted to one t~rmin~l of a transfer switch 46. A coaxial cable (not shown) forms a signal conduit from a b~est~tion (not shown) to the cable te~ l 42.
The ~ r~;l switch 46 has three other terminals, of which two are conn~cted to the input 15 and the output, respectively, of an amplifier 48, while the third is conn~cted through band limiting filter 50 to an ~ P~n~ A9.
The lldl~r~ switch 46 has two switch states. In the first switch state, the lldl~rel switch 46 connects the component 44 to the input of the amplifier 48 and also connects the output 20 of the amplifier 48 to the band limiting filter S0 and the ~nt~nn~ A9. In its second switch state, the ~ r~ switch 46 connects the component 44 to the output of the amplifier 48, and also connects the ~nt~nn~ A9, through the band limiting filter 50, to the input of the amplifier 48.
25 It will be appa~en~ that, in the first switch state of the llal~r~,l switch 46, the amplifier 48 serves to amplify a ~l~lslllil signal passing from the coaxial cable to the ~ 52, whereas in the second switch state of the l~ r~l switch 46 the amplifier serves to amplify an incoming receive signal passing from the ~ 52 to the coaxial cable.
2 1 6868 ~
The component 44, which differs from the corresponding component disclosed in the aforesaid prior United States Patent No. 5,377,255, is illustrated in greater detail in Figure 6, in which a power pickup 54 is shown, which serves to supply t_e power to the component 44.
s It is particularly pointed out that unlike the corresponding RF l~eat~r disclosed in United States Patent No. 5,377,255, the RF repeater has no lldns~ /receive ~wilching logic circuit 56 for deriving signal timing from the basestation and the h~n~lset 10 Tn~t~l, the RF repeater 40 of Figure 6 includes a timing generator in the form of a high speed oscillator 56 to provide a timing output to the transfer switch 46 to cause the RF
repeater 40 to switch between transmit and receive states. The frequency of the timing output of the oscillator is sufficiently high to cause the transfer switch 46 to effect Nyquist sampling of both of the basestation-to-h~n-lcet signal and the handset-to-~ st~tion signal.
15 By use of a bandpass filter 58 to reconstruct the h~n~lset-to-base~tion receive signal and by use of the filter 50 to reconstruct the basestation-to-h~n-l~et signal, functionality similar to that described above with reference to Figures 3 and 4a is achieved, except that in the RF repeater 40 only one amplifier is used. The use of one amplifier in the RF repeater 40 emphasizes that, at any instant, the amplifier is configured for one and only one of 20 ba~est~tion-to-handset or h~ntl~et-to-~est~tion co..~ tions. The smooth, continuous intercolnlllunication between b~est~tion and handset results from the reconstruction filters 50 and 58.
A third embodiment of the present invention is shown in Figure 7, in which reference 25 numeral 70 in-1icates generally a further RF repeater.
The RF repeater 70 of Figure 7 has an amplifier 72, which is a high gain (e.g. 60 dB) amplifier, andwhich is connected as shownto four switches Sl-S4. The four switches Sl-S4 form part of a switching arrangement 74, which has first and second inputs 76 and 77 conn~cte~l to ~nt~nn~ Al0 and Al l, for receiving respectively, a signal broadcast as a radio signal from the bs~est~tion l0a and a signal broadcast as a radio signal from the h~ntl~et l l a.
The switching arrangement 74 also has first and second outputs 79 and 80 which are 5 connected to antennas Al2 and Al3, which respectively broadcast a reconstituted receive signal to the basestation l 0 and a reconstituted transmit signal to the handset l l .
Between the switches S3 and S4 and the outputs 79 and 80, there are connected a pair of b~nclp~es filters 82 and 83.
Four low gain amplifiers 84, 85, 86 and 87 are connected as shown to the inputs and outputs of the switching arrangement 64. The amplifiers 84-87 are low gain (e.g. 6 dB) amplifiers.
The switches S 1-S4 are operated by an oscillator 90. More particularly, the switches S l and 15 S4 normally operate together, i.e. have the same state, while switches S2 and S3 operate together, i.e. have the same state, but the state ofthe switches Sl and S4 is opposite from that of the switches S2 and S3.
In operation of the RF repeater 70, the signal received by the ~nt~nn~ A10 from the 20 b~est:~tion 10 traverses a signal path including the switch S1, the amplifier 72, the switch S4, the b~n-lp~s filter 83 and the antenna A13, from which it is broadcast to the handset 11.
On the other hand, the signal received by the antenna A11 from the handset l l traverses a signal path through the switch S2, the amplifier 72, the switch S3 and the b~n(1p~s filter 82, and is then broadcast from the antenna Al2 to the basestation l0.
The switches S 1-S4 are incorporated in a commercially available integrated circuit and are operated by a timing output from the timing generator oscillator 90 at a frequency sufficiently high to effect Nyquist sampling of the signals, as will be a~ar~lll from the above, and the signals, after amplification by the amplifier 72, are reconstructed by the filters 82and83.
By the provision of the amplifiers 81 through 87, useful signal energy in both the transmit 5 and receive signals is not blocked prior to amplification, and thus the RF link budget is improved.
10 In Figure 2, an RF repeater indicated generally by reference numeral 16 employs four physically distinct ~"I~n~ A3, A4, AS and A6 for b~sest~tion-to-h~n-1set and h~nll~et-to-basestation co~ ic~tions~ with amplifier 18 connected in a transmit signal path P3 between the ~ntPnn~ A3 and A6 and with amplifier 20 conn~ctçd in a receive signal path P4 between the ~ntPnn~ B and C, as shown. If the pl~cçnlçnt of the ~ u~ A3-A6 is15 effected correctly, the RF repeater 16 opel~es without need of timing signals and can even support large time delays. However, the RF lepea~er 16 is capable of osc-ill~ting because signals em~n~ting from the ~nt~n~ A3 can be received at the ~ nl~ A4, amplified by the amplifier 20 broadcast by the ~nt~nn~ AS and received at the ~l~t~nl~ A6, and then amplified by the amplifier 18 to be rebroadcast from the ~ A3.
To avoid this oscillation, the ~ntPnn~ A3-A6 need to be carefully sited so as not to interact, while still keeping the handset and the basestation in the field of view. In practice, this is difficult.
25 It is accordingly an object of the present invention to provide a novel and improved RF
repeater for use in cordless telephone systems which avoids a need for a plurality of ~nt~nn~, but which does not need transmit and receive signal timing info,lllation 2 1 6~68 1 According to the present invention, there is provided an RF repeater which has a timing output and a ~wi~cl.illg arrangement the operation of which is controlled by a timing output from the timing generator. The ~wi~chhlg arrangement samples a b~çst~tion-to-h~n-1~et signal and a handset-to-basestation signal and ~lt~rn~tely connects samples of the two 5 signals to at least one amplifier for amplification thereby. The frequency of the timing output of the timing generator is selçctçd so that the ~wilcl~ing all~lgel"ent effects Nyquist sampling of the signals and one or more filters are employed to reconstruct the signals from the amplified samples thereof.
10 The RF repeater according to the present invention thcl~rol~ has the advantage that no timing information is required to be tr~n.~mitted to the RF r~eatel, although generic information as to bandwidth and center frequency of operation must be known. Also, the present RF repeater can be implemented with only two ~ n~c and so can be easier to site than that shown in Figure 2.
The present RF l~peater can support bursts of the two signals which overlap in time which typically occurs due to large time delays in the propagation or signal links.
In addition, since the present RF repeater operates without reference to the b~ceshtion or 20 handset timing, it can support more than one TDD h~n~l~et type ~imlllt~nPously, even if the two types have dirÇelellt timings. Also, the present RF repeater can support FDD
handsets, even while simlllt~n~-ously supporting TDD handsets.
Further fealuies and advantages of the present invention will be more readily a~par~
25 from the following description thereof when taken in connection with the acco,~a~yhlg drawings, in which:
Figures 1 and 2 show diagrams of two prior art RF repeaters with an associated ~est~tion and handset;
2 1 6868 ~
Figure 3 shows a block diagram of an RF repeater according to a first embodiment of the present invention, in association with the b~est~tion and the handset;
Figures 4a to 4d show waveforms which occur in the RF repeater of Figure 3;
Figures S and 6 show block diagrams ill~ lhlg another RF repeater according to a second embodiment of the present invention; and Figure 7 shows a block diagram of a further RF repeater, according to a third embodiment 10 ofthe present invention.
Figure 3 shows an RF repeater, in~li~tçd generally by reference numeral 24, which differs from the RF repeater 12 of Figure 1 by the ad~litic)n of two RF b~n~lr~s filters 26 and 28, and a high speed oscillator 30 to provide a timing output which provides the RF r~ealel 15 24 with a very fast ~wilCl~illg action. In the embodiment of Figure 3, the components 14a and 14b are replaced by switches 14c and 14d.
The switches 14c and 14d form a switching arrangement which a) samples the two signals passing through the RF repeater 14, i.e. the b~est~tion-to-h~n-lset signal and the h~n-l~et-20 to-b~cest~tion signal and b) connects the samples of the two signals ~ltçrn~tçly to respective ones of the amplifiers. Thus, successive samples of the b~est~tion-to-h~n-l~et signal are amplified by the amplifier 18a and, ~ltçrn~ting with these samples, successive samples of the handset-to-b~est~tion signals are amplified by the amplifier 20a.
25 By chopping ~e switches 14c and 14d quickly between the two signal directions (base-to-handset and h~n~l~et-to-base), and by using replacing filters 26 and 28 by reconstruction filters 26a and 28a, the lack of a timing signal synchronized to the time epoch is nn~cess~ry since the reconstruction filters 26a and 28a ensure that any errors due to the high speed ~wilcl~illg are ~inl~o~ , provided the usual Nyquist sampling criteria apply, i.e. the switching rate of the switches 14c and 14d ~lele~ cl by the frequency of the timing outputs of the oscillator 30, measured in Hertz, should be at least twice the bandwidth of the RF signals that the amplifier is to rebroadcast, and the reconstruction filters 26a and 28b are bAn-lrA~s filters with a bandwidth of less than half the ~wilching 5 rate, but more than the RF signal bandwidth.
To take a concrete example, CT-2 signals typically occupy rh~nnel~ from 864 to 868 MHz. The net RF signal bandwidth, if all channels are to be rebroadcast, is 4 MHz. If an asynchronous, fast oscillator were employed to switch at a 21 MHz switch rate, a 10 typical filter bandwidth for the filters 26a and 26b would be 6 MHz, with a filter center frequency of 866 MHz.
Figure 4a dia~ ldmlllatically illustrates the b~est~tion-to-h~n-l~et signal passing through points X, X1, X2T and X3T of Figure 3. It will be seen that at points X and X1, i.e.
15 before and after the filter 26a, the basestation-to-h~n~lset signal received by All~ A7 from basestation 10a is lmrhAnged. At point X2T, this signal has been sampled by the switch 14c, and at point X3T, and at point Y, the signal samples appear in their amplified state, as amplified by amplifier 18a. The signal samples then pass through the b2n-1r~ss filter 28b, which from these samples reconstructs the basestation-to-handset signal, in its 20 amplified form, so that it appears at point Yl as illustrated in Figure 4b.
The h~n~et-to-ba~est~tion signal, received at ~-lelll-A A8 from h~n-l~et lla, appears at points Y1 and Y, i.e. before and after passing through the bandpass filter 28b, as shown in Figure 4c. This signal is then sampled by the switch 14d, so that the samples thereof 25 appear at point YR2 in the form shown in Figure 4c. These signal samples are then amplified by amplifier 20a and appear at points YR3 and X as shown in Figure 4c. The amplified samples then pass to the b~n-lrA~s filter 26a, which reconstruct the h~ncl~et-to-handset signal from these samples into the form diag~",ll,~ti~lly illustrated in Figure 4d.
2l6868l Figures 4b and 4d illustrate the interleaved native of the b~est~tion-to-h~ntl~et and h~n~l~et-to-b~est~tion c~ "~ ications. However, the amplifier 24 of Figure 3 does not require the colmllul~ications timing. Also, if the basestation-to-h~n~lset and h~n-l~et-to-basestation con~lllul~ications overlap in time, as happens when large time delays are 5 encountered, the amplifier 24 will still operate s~ti~f~ctorily.
Figures S shows an RF repeater, in~ ted generally by leferellce numeral 40, which is similar to that disclosed in the inventor's United States Patent No. 5,377,255, issued December 27, 1994, the disclosure of which is incol~?oldled herein by reference. The RF
10 repeater 40 has a coaxial cable input and output 42 conn~ct~l to a component 44 which is in turn conn~cted to one t~rmin~l of a transfer switch 46. A coaxial cable (not shown) forms a signal conduit from a b~est~tion (not shown) to the cable te~ l 42.
The ~ r~;l switch 46 has three other terminals, of which two are conn~cted to the input 15 and the output, respectively, of an amplifier 48, while the third is conn~cted through band limiting filter 50 to an ~ P~n~ A9.
The lldl~r~ switch 46 has two switch states. In the first switch state, the lldl~rel switch 46 connects the component 44 to the input of the amplifier 48 and also connects the output 20 of the amplifier 48 to the band limiting filter S0 and the ~nt~nn~ A9. In its second switch state, the ~ r~ switch 46 connects the component 44 to the output of the amplifier 48, and also connects the ~nt~nn~ A9, through the band limiting filter 50, to the input of the amplifier 48.
25 It will be appa~en~ that, in the first switch state of the llal~r~,l switch 46, the amplifier 48 serves to amplify a ~l~lslllil signal passing from the coaxial cable to the ~ 52, whereas in the second switch state of the l~ r~l switch 46 the amplifier serves to amplify an incoming receive signal passing from the ~ 52 to the coaxial cable.
2 1 6868 ~
The component 44, which differs from the corresponding component disclosed in the aforesaid prior United States Patent No. 5,377,255, is illustrated in greater detail in Figure 6, in which a power pickup 54 is shown, which serves to supply t_e power to the component 44.
s It is particularly pointed out that unlike the corresponding RF l~eat~r disclosed in United States Patent No. 5,377,255, the RF repeater has no lldns~ /receive ~wilching logic circuit 56 for deriving signal timing from the basestation and the h~n~lset 10 Tn~t~l, the RF repeater 40 of Figure 6 includes a timing generator in the form of a high speed oscillator 56 to provide a timing output to the transfer switch 46 to cause the RF
repeater 40 to switch between transmit and receive states. The frequency of the timing output of the oscillator is sufficiently high to cause the transfer switch 46 to effect Nyquist sampling of both of the basestation-to-h~n-lcet signal and the handset-to-~ st~tion signal.
15 By use of a bandpass filter 58 to reconstruct the h~n~lset-to-base~tion receive signal and by use of the filter 50 to reconstruct the basestation-to-h~n-l~et signal, functionality similar to that described above with reference to Figures 3 and 4a is achieved, except that in the RF repeater 40 only one amplifier is used. The use of one amplifier in the RF repeater 40 emphasizes that, at any instant, the amplifier is configured for one and only one of 20 ba~est~tion-to-handset or h~ntl~et-to-~est~tion co..~ tions. The smooth, continuous intercolnlllunication between b~est~tion and handset results from the reconstruction filters 50 and 58.
A third embodiment of the present invention is shown in Figure 7, in which reference 25 numeral 70 in-1icates generally a further RF repeater.
The RF repeater 70 of Figure 7 has an amplifier 72, which is a high gain (e.g. 60 dB) amplifier, andwhich is connected as shownto four switches Sl-S4. The four switches Sl-S4 form part of a switching arrangement 74, which has first and second inputs 76 and 77 conn~cte~l to ~nt~nn~ Al0 and Al l, for receiving respectively, a signal broadcast as a radio signal from the bs~est~tion l0a and a signal broadcast as a radio signal from the h~ntl~et l l a.
The switching arrangement 74 also has first and second outputs 79 and 80 which are 5 connected to antennas Al2 and Al3, which respectively broadcast a reconstituted receive signal to the basestation l 0 and a reconstituted transmit signal to the handset l l .
Between the switches S3 and S4 and the outputs 79 and 80, there are connected a pair of b~nclp~es filters 82 and 83.
Four low gain amplifiers 84, 85, 86 and 87 are connected as shown to the inputs and outputs of the switching arrangement 64. The amplifiers 84-87 are low gain (e.g. 6 dB) amplifiers.
The switches S 1-S4 are operated by an oscillator 90. More particularly, the switches S l and 15 S4 normally operate together, i.e. have the same state, while switches S2 and S3 operate together, i.e. have the same state, but the state ofthe switches Sl and S4 is opposite from that of the switches S2 and S3.
In operation of the RF repeater 70, the signal received by the ~nt~nn~ A10 from the 20 b~est:~tion 10 traverses a signal path including the switch S1, the amplifier 72, the switch S4, the b~n-lp~s filter 83 and the antenna A13, from which it is broadcast to the handset 11.
On the other hand, the signal received by the antenna A11 from the handset l l traverses a signal path through the switch S2, the amplifier 72, the switch S3 and the b~n(1p~s filter 82, and is then broadcast from the antenna Al2 to the basestation l0.
The switches S 1-S4 are incorporated in a commercially available integrated circuit and are operated by a timing output from the timing generator oscillator 90 at a frequency sufficiently high to effect Nyquist sampling of the signals, as will be a~ar~lll from the above, and the signals, after amplification by the amplifier 72, are reconstructed by the filters 82and83.
By the provision of the amplifiers 81 through 87, useful signal energy in both the transmit 5 and receive signals is not blocked prior to amplification, and thus the RF link budget is improved.
Claims (14)
1. An RF repeater for exchanging digital telephone signals between a basestation and a mobile cordless handset, comprising:
at least one amplifier for amplifying basestation-to-handset signals and handset-to-basestation signals;
a timing generator for providing a timing output;
a switching arrangement operable in response to the timing output to sample saidsignals and to connect the sampled signals alternately to said at least one amplifier for amplification thereby;
the timing output of said timing generator having a frequency sufficient to effect Nyquist sampling of said signals by said switching arrangement; and at least one filter connected to said at least one amplifier for reconstructing said signals from the amplified samples thereof.
at least one amplifier for amplifying basestation-to-handset signals and handset-to-basestation signals;
a timing generator for providing a timing output;
a switching arrangement operable in response to the timing output to sample saidsignals and to connect the sampled signals alternately to said at least one amplifier for amplification thereby;
the timing output of said timing generator having a frequency sufficient to effect Nyquist sampling of said signals by said switching arrangement; and at least one filter connected to said at least one amplifier for reconstructing said signals from the amplified samples thereof.
2. An RF repeater as claimed in claim 1, including an antenna for exchanging said signals with the basestation as radio signals.
3. An RF repeater for exchanging digital telephone signals between a basestation and a mobile cordless handset, comprising:
a pair of switches;
a first signal path for basestation-to-handset signals and a second signal path for handset-to-basestation signals, said first and second signal paths extending between said switches;
a timing generator connected to said switches and operable to cause said switches to alternately interrupt said signals so as to chop said signals into signal components at a frequency sufficiently high to effect Nyquist sampling of said signals; and filters connected to said switches and effective to reconstitute said signals from the amplified signal components.
a pair of switches;
a first signal path for basestation-to-handset signals and a second signal path for handset-to-basestation signals, said first and second signal paths extending between said switches;
a timing generator connected to said switches and operable to cause said switches to alternately interrupt said signals so as to chop said signals into signal components at a frequency sufficiently high to effect Nyquist sampling of said signals; and filters connected to said switches and effective to reconstitute said signals from the amplified signal components.
4. An RF repeater for exchanging digital telephone signals between a basestation and a mobile cordless handset, comprising:
an amplifier for amplifying both basestation-to-handset signals and handset-to-basestation signals, said amplifier having an input and an output;
an antenna for exchanging said signals with the handset as radio signals;
a signal input for receiving the basestation-to-handset signal;
a timing generator for providing a timing output;
a switching arrangement operable in response to the timing output to alternately connect (a) said antenna to said amplifier input and said output to said signal input and (b) said signal input to said amplifier input and said amplifier output to said antenna;
the timing output of said timing generator having a frequency sufficient to effect Nyquist sampling of said signals by said switching arrangement; and at least one filter connected to said at least one amplifier for reconstructing said signals from the amplified samples thereof.
an amplifier for amplifying both basestation-to-handset signals and handset-to-basestation signals, said amplifier having an input and an output;
an antenna for exchanging said signals with the handset as radio signals;
a signal input for receiving the basestation-to-handset signal;
a timing generator for providing a timing output;
a switching arrangement operable in response to the timing output to alternately connect (a) said antenna to said amplifier input and said output to said signal input and (b) said signal input to said amplifier input and said amplifier output to said antenna;
the timing output of said timing generator having a frequency sufficient to effect Nyquist sampling of said signals by said switching arrangement; and at least one filter connected to said at least one amplifier for reconstructing said signals from the amplified samples thereof.
5. An RF repeater for exchanging digital telephone signals between a basestation and a mobile cordless handset comprising:
an amplifier;
a timing generator for generating a timing output;
a switching arrangement connected to said amplifier and said timing generator and operable to alternately connect a basestation-to-handset signal and a handset-to-basestation signal to said amplifier in response to the timing output to chop said signals into signal fragments for amplification by said amplifier;
the timing output of said timing generator having a frequency sufficient to effect Nyquist sampling of said signals by said switching arrangement; and a pair of filters connected to respective outlets of said switching arrangement and effective to at least substantially reconstitute said transmit and receive signals from said signal fragments.
an amplifier;
a timing generator for generating a timing output;
a switching arrangement connected to said amplifier and said timing generator and operable to alternately connect a basestation-to-handset signal and a handset-to-basestation signal to said amplifier in response to the timing output to chop said signals into signal fragments for amplification by said amplifier;
the timing output of said timing generator having a frequency sufficient to effect Nyquist sampling of said signals by said switching arrangement; and a pair of filters connected to respective outlets of said switching arrangement and effective to at least substantially reconstitute said transmit and receive signals from said signal fragments.
6. A digital telephone system, comprising:
a basestation for connection to a public switched telephone system;
a mobile cordless handset; and an RF repeater, said RF repeater comprising at least one amplifier for amplifying the signals and a switching arrangement operable to chop the signals at a predetermined switching frequency into signal fragments; and at least one bandpass filter for filtering the amplified signal fragments, said at least one bandpass filter having a bandpass related to said switching frequency as to at least substantially reconstitute the transmit and receive signals from the signal fragments.
a basestation for connection to a public switched telephone system;
a mobile cordless handset; and an RF repeater, said RF repeater comprising at least one amplifier for amplifying the signals and a switching arrangement operable to chop the signals at a predetermined switching frequency into signal fragments; and at least one bandpass filter for filtering the amplified signal fragments, said at least one bandpass filter having a bandpass related to said switching frequency as to at least substantially reconstitute the transmit and receive signals from the signal fragments.
7. A digital telephone system as claimed in claim 6, wherein said switching arrangement comprises a pair of switches, and first and second signal paths extending between said pair of switches, said RF repeater including an oscillator controlling the rate of operation of said switches, and said at least one bandpass filter comprising a pair of filters respectively connected to said switches.
8. A digital telephone system as defined in claim 6, wherein said switch arrangement comprises a single switch operable to connect the signals alternately to said amplifier and said RF repeater includes an oscillator operatively connected to said switch for operating said switch at the predetermined switching frequency.
9. A digital telephone system as claimed in claim 6, wherein said switching arrangement has first and second inputs for receiving the signals respectively; and first and second outputs for supplying the reconstituted signals, respectively;
said switching arrangement comprising switches operable to alternately connect said first input to said first output and said second input to said second output through said amplifier;
said RF repeater including an oscillator operable to effect switching of said switches at the predetermined switching frequency, and said at least one bandless filter being connected between said switches and said first and second outputs, respectively.
said switching arrangement comprising switches operable to alternately connect said first input to said first output and said second input to said second output through said amplifier;
said RF repeater including an oscillator operable to effect switching of said switches at the predetermined switching frequency, and said at least one bandless filter being connected between said switches and said first and second outputs, respectively.
10. A method of repeating signals between a basestation and a mobile handset, comprising the steps of:
receiving first signals from the basestation and second signals from the handset at a repeater location generating a timing output at the repeater location.
employing the timing output to provide Nyquist samples of the first and second signals;
amplifying the signal samples;
reconstructing the first and second signals from the amplified samples and transmitting the reconstructed first signal to the handset and the reconstructedsecond signal to the basestation from the repeater location
receiving first signals from the basestation and second signals from the handset at a repeater location generating a timing output at the repeater location.
employing the timing output to provide Nyquist samples of the first and second signals;
amplifying the signal samples;
reconstructing the first and second signals from the amplified samples and transmitting the reconstructed first signal to the handset and the reconstructedsecond signal to the basestation from the repeater location
11. A method as claimed in claim 10, which includes multiplexing the signal samples and amplifying the multiplexed samples in a common amplifier.
12. An RF repeater for exchanging digital telephone signals between a basestation and a mobile cordless handset, comprising:
timing means for generating a timing output, switch means connected to said timing means and responsive to the timing output for sampling the signals at a rate determined by said timing output, amplifier means for amplifying the sampled signals; and filter means connected to said amplifier means for reconstructing said transmit and receive signals from the amplified components thereof.
timing means for generating a timing output, switch means connected to said timing means and responsive to the timing output for sampling the signals at a rate determined by said timing output, amplifier means for amplifying the sampled signals; and filter means connected to said amplifier means for reconstructing said transmit and receive signals from the amplified components thereof.
13. An RF repeater as claimed in claim 12, wherein said timing means provides the timing output with a frequency sufficiently high to cause said switch means to effect Nyquist sampling of the signals.
14. An RF repeater as claimed in claim 12 or 13, wherein said amplifier means comprises a single amplifier and said switch means comprises means for alternately connecting samples of a basestation-to-handset signal and at a handset-to-basestation signal to said single amplifier.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002168681A CA2168681A1 (en) | 1996-02-02 | 1996-02-02 | Rf repeaters for time division cordless telephone systems without timing signals |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002168681A CA2168681A1 (en) | 1996-02-02 | 1996-02-02 | Rf repeaters for time division cordless telephone systems without timing signals |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2168681A1 true CA2168681A1 (en) | 1997-08-03 |
Family
ID=4157487
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002168681A Abandoned CA2168681A1 (en) | 1996-02-02 | 1996-02-02 | Rf repeaters for time division cordless telephone systems without timing signals |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2168681A1 (en) |
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- 1996-02-02 CA CA002168681A patent/CA2168681A1/en not_active Abandoned
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